ipvlan: don't loose broadcast MAC when setting MAC filters

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) gets called after the address was added, it blows away the broadcast MAC address in mac_filters that was added at IPv4 address addition. Fix that.

Signed-off-by Dan Williams <[email protected]>

---
 drivers/net/ipvlan/ipvlan_main.c | 3 +++
 1 file changed, 3 insertions(+)

drivers/net/ipvlan/ipvlan_main.c +0 -0

index 4f4099d..d34f580 100644

ipvlan currently fails DHCP addressing for two reasons:

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient), which don't get checked against the IP address list.

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

Instead of doing ugly stuff like watching for outgoing DHCP requests and adding the broadcast MAC to mac_filters for a period of time, just always allow the broadcast MAC. This lets the ipvlan interface be configured with DHCP in Layer2 mode as long as as broadcast replies are used.

Signed-off-by Dan Williams <[email protected]>

ipvlan currently fails DHCP addressing for two reasons:

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient), which don't get checked against the IP address list.

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

Instead of doing ugly stuff like watching for outgoing DHCP requests and adding the broadcast MAC to mac_filters for a period of time, just always allow the broadcast MAC. This lets the ipvlan interface be configured with DHCP in Layer2 mode as long as as broadcast replies are used.

Signed-off-by Dan Williams <[email protected]>

---
 drivers/net/ipvlan/ipvlan_main.c | 21 ++++-----------------
 1 file changed, 4 insertions(+), 17 deletions(-)

drivers/net/ipvlan/ipvlan_main.c +4 -18

index d34f580..787d7fb 100644
@@ -214,17 +214,6 @@ static void ipvlan_change_rx_flags(struct net_device *dev, int change)
                dev_set_allmulti(phy_dev, dev->flags & IFF_ALLMULTI? 1 : -1);
 }
 
-static void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
-{
-       struct net_device *dev = ipvlan->dev;
-       unsigned int hashbit = ipvlan_mac_hash(dev->broadcast);
-
-       if (set && !test_bit(hashbit, ipvlan->mac_filters))
-               __set_bit(hashbit, ipvlan->mac_filters);
-       else if (!set && test_bit(hashbit, ipvlan->mac_filters))
-               __clear_bit(hashbit, ipvlan->mac_filters);
-}
-
 static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
 {
        struct ipvl_dev *ipvlan = netdev_priv(dev);

@@ -239,11 +228,11 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
                netdev_for_each_mc_addr(ha, dev)
                        __set_bit(ipvlan_mac_hash(ha->addr), mc_filters);
 
+               /* always allow broadcast frames */
+               __set_bit(ipvlan_mac_hash(dev->broadcast), mc_filters);
+
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
-
-               if (ipvlan->ipv4cnt)
-                       ipvlan_set_broadcast_mac_filter(ipvlan, true);
        }
        dev_uc_sync(ipvlan->phy_dev, dev);
        dev_mc_sync(ipvlan->phy_dev, dev);

@@ -470,6 +459,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
        INIT_LIST_HEAD(&ipvlan->addrs);
        ipvlan->ipv4cnt = 0;
        ipvlan->ipv6cnt = 0;
+       __set_bit(ipvlan_mac_hash(dev->broadcast), ipvlan->mac_filters);
 
        /* TODO Probably put random address here to be presented to the
         * world but keep using the physical-dev address for the outgoing

@@ -694,7 +684,6 @@ static int ipvlan_add_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_add_tail_rcu(&addr->anode, &ipvlan->addrs);
        ipvlan->ipv4cnt++;
        ipvlan_ht_addr_add(ipvlan, addr);
-       ipvlan_set_broadcast_mac_filter(ipvlan, true);
 
        return 0;
 }

@@ -711,8 +700,6 @@ static void ipvlan_del_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_del_rcu(&addr->anode);
        ipvlan->ipv4cnt--;
        WARN_ON(ipvlan->ipv4cnt < 0);
-       if (!ipvlan->ipv4cnt)
-           ipvlan_set_broadcast_mac_filter(ipvlan, false);
        kfree_rcu(addr, rcu);
 
        return;
--

2.1.0

Quoted 16 lines · Dan Williams

ipvlan currently fails DHCP addressing for two reasons:

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient), which don't get checked against the IP address list.

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

Quoted 6 lines

Instead of doing ugly stuff like watching for outgoing DHCP requests and adding the broadcast MAC to mac_filters for a period of time, just always allow the broadcast MAC. This lets the ipvlan interface be configured with DHCP in Layer2 mode as long as as broadcast replies are used.

Guys, stop thinking that we live in IPv4-only world! Think about a hybrid environment where all your IPvlan slaves are IPv6 only while your network has IPv4 (with crap-load of broadcast traffic) and IPv6 traffic. In that situation IPvlan demuxer has to forward all that broadcast-traffic to it's slaves which they don't care at all.

I agree that the current driver falls short of handling DHCPv4 and needs a fix. But for couple of initial config packets, it's not wise to loose the performance forever. I don't like this patch.

Quoted 72 lines

Signed-off-by Dan Williams <[email protected]>

---
 drivers/net/ipvlan/ipvlan_main.c | 21 ++++-----------------
 1 file changed, 4 insertions(+), 17 deletions(-)

drivers/net/ipvlan/ipvlan_main.c +4 -18

index d34f580..787d7fb 100644
@@ -214,17 +214,6 @@ static void ipvlan_change_rx_flags(struct net_device *dev, int change)
                dev_set_allmulti(phy_dev, dev->flags & IFF_ALLMULTI? 1 : -1);
 }
 
-static void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
-{
-       struct net_device *dev = ipvlan->dev;
-       unsigned int hashbit = ipvlan_mac_hash(dev->broadcast);
-
-       if (set && !test_bit(hashbit, ipvlan->mac_filters))
-               __set_bit(hashbit, ipvlan->mac_filters);
-       else if (!set && test_bit(hashbit, ipvlan->mac_filters))
-               __clear_bit(hashbit, ipvlan->mac_filters);
-}
-
 static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
 {
        struct ipvl_dev *ipvlan = netdev_priv(dev);

@@ -239,11 +228,11 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
                netdev_for_each_mc_addr(ha, dev)
                        __set_bit(ipvlan_mac_hash(ha->addr), mc_filters);
 
+               /* always allow broadcast frames */
+               __set_bit(ipvlan_mac_hash(dev->broadcast), mc_filters);
+
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
-
-               if (ipvlan->ipv4cnt)
-                       ipvlan_set_broadcast_mac_filter(ipvlan, true);
        }
        dev_uc_sync(ipvlan->phy_dev, dev);
        dev_mc_sync(ipvlan->phy_dev, dev);

@@ -470,6 +459,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
        INIT_LIST_HEAD(&ipvlan->addrs);
        ipvlan->ipv4cnt = 0;
        ipvlan->ipv6cnt = 0;
+       __set_bit(ipvlan_mac_hash(dev->broadcast), ipvlan->mac_filters);
 
        /* TODO Probably put random address here to be presented to the
         * world but keep using the physical-dev address for the outgoing

@@ -694,7 +684,6 @@ static int ipvlan_add_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_add_tail_rcu(&addr->anode, &ipvlan->addrs);
        ipvlan->ipv4cnt++;
        ipvlan_ht_addr_add(ipvlan, addr);
-       ipvlan_set_broadcast_mac_filter(ipvlan, true);
 
        return 0;
 }

@@ -711,8 +700,6 @@ static void ipvlan_del_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_del_rcu(&addr->anode);
        ipvlan->ipv4cnt--;
        WARN_ON(ipvlan->ipv4cnt < 0);
-       if (!ipvlan->ipv4cnt)
-           ipvlan_set_broadcast_mac_filter(ipvlan, false);
        kfree_rcu(addr, rcu);
 
        return;
--

2.1.0

The current logic disables broadcast by default and enables only when an IPv4 address is added. If this is inverted and - enables broadcast by default but disables it when only IPv6 address(es) is / are added. These links can have multiple addresses and hence have to be careful if any one of those is IPv4 then broadcast bit has to be set.

Quoted 6 lines · Mahesh Bandewar

The current logic disables broadcast by default and enables only when an IPv4 address is added. If this is inverted and - enables broadcast by default but disables it when only IPv6 address(es) is / are added. These links can have multiple addresses and hence have to be careful if any one of those is IPv4 then broadcast bit has to be set.

You'd have to be careful and ignore IPv6 link local addresses. Those are added automatically whenever IPv6 is enabled and their presence does not mean the network is not IPv4 only.

But I don't like such magic behavior. It would lead to DHCP sometimes working and sometimes not in mixed v4/v6 environment depending on whether DHCPv4 or SLAAC was faster.

Could we perhaps add a flag when creating ipvlan interface stating whether IPv4 broadcast should be always enabled? Or, rather, the other way round - whether it should be disabled by default. Call it "nodhcp" or so.

Btw, speaking about IPv6 link local addresses, these actually do not work with ipvlan correctly. I'm getting DAD failures if I have more than one ipvlan interface, which is no wonder. This means that ipvlan cannot work with IPv6 reliably by default (unless you take care of ll address assignment and ensure all ipvlan interfaces get a different one).

Quoted 21 lines · Jiri Benc

Quoted 6 lines · Mahesh Bandewar

The current logic disables broadcast by default and enables only when an IPv4 address is added. If this is inverted and - enables broadcast by default but disables it when only IPv6 address(es) is / are added. These links can have multiple addresses and hence have to be careful if any one of those is IPv4 then broadcast bit has to be set.

You'd have to be careful and ignore IPv6 link local addresses. Those are added automatically whenever IPv6 is enabled and their presence does not mean the network is not IPv4 only.

But I don't like such magic behavior. It would lead to DHCP sometimes working and sometimes not in mixed v4/v6 environment depending on whether DHCPv4 or SLAAC was faster.

Could we perhaps add a flag when creating ipvlan interface stating whether IPv4 broadcast should be always enabled? Or, rather, the other way round - whether it should be disabled by default. Call it "nodhcp" or so.

Quoted 6 lines

Btw, speaking about IPv6 link local addresses, these actually do not work with ipvlan correctly. I'm getting DAD failures if I have more than one ipvlan interface, which is no wonder. This means that ipvlan cannot work with IPv6 reliably by default (unless you take care of ll address assignment and ensure all ipvlan interfaces get a different one).

ipvlan doesn't set dev_id. Once dev_id is set the kernel's IPv6LL address generation code will assign a different LL address to each ipvlan interface created from the same physical interface, despite that they have the same MAC address.

But of course you'd have to be careful to assign a *different* dev_id than any of that physical interface's non-ipvlan children too, and I have no idea how that would work since dev_id is currently done per-driver. eg, if you have a physical interface with dev_id=1 which you then create an ipvlan from, that ipvlan must not use dev_id=1 or it will be assigned the same IPv6LL address as the parent.

Dan

Quoted 29 lines · Dan Williams

Quoted 21 lines · Jiri Benc

Quoted 6 lines · Mahesh Bandewar

The current logic disables broadcast by default and enables only when an IPv4 address is added. If this is inverted and - enables broadcast by default but disables it when only IPv6 address(es) is / are added. These links can have multiple addresses and hence have to be careful if any one of those is IPv4 then broadcast bit has to be set.

You'd have to be careful and ignore IPv6 link local addresses. Those are added automatically whenever IPv6 is enabled and their presence does not mean the network is not IPv4 only.

But I don't like such magic behavior. It would lead to DHCP sometimes working and sometimes not in mixed v4/v6 environment depending on whether DHCPv4 or SLAAC was faster.

Could we perhaps add a flag when creating ipvlan interface stating whether IPv4 broadcast should be always enabled? Or, rather, the other way round - whether it should be disabled by default. Call it "nodhcp" or so.

Quoted 6 lines

Btw, speaking about IPv6 link local addresses, these actually do not work with ipvlan correctly. I'm getting DAD failures if I have more than one ipvlan interface, which is no wonder. This means that ipvlan cannot work with IPv6 reliably by default (unless you take care of ll address assignment and ensure all ipvlan interfaces get a different one).

Quoted 5 lines

ipvlan doesn't set dev_id. Once dev_id is set the kernel's IPv6LL address generation code will assign a different LL address to each ipvlan interface created from the same physical interface, despite that they have the same MAC address.

Yes, that was what my plan was but never got around fixing that

Quoted 7 lines

But of course you'd have to be careful to assign a *different* dev_id than any of that physical interface's non-ipvlan children too, and I have no idea how that would work since dev_id is currently done per-driver. eg, if you have a physical interface with dev_id=1 which you then create an ipvlan from, that ipvlan must not use dev_id=1 or it will be assigned the same IPv6LL address as the parent.

The description is very clear for dev_id (in netdevice.h). So the idea of using the subsequent numbers after master's id should be possible. After all these logical devices are going to share the same link. Most physical drivers don't assign dev-id so the beginning is 0x0 (for the physical driver) and from 0x1 can be assigned to the logical links. The definition is not clear in terms of what is the beginning (0x0 or 0x1) but from the code that generates the IPv6LL it's common that it's 0x0 hence logical links on top of these links can use 0x1 onward. However a check to see if the master-link has dev-id and staying clear of that should be sufficient.

Quoted 44 lines · Mahesh Bandewar

Quoted 29 lines · Dan Williams

Quoted 21 lines · Jiri Benc

Quoted 6 lines · Mahesh Bandewar

The current logic disables broadcast by default and enables only when an IPv4 address is added. If this is inverted and - enables broadcast by default but disables it when only IPv6 address(es) is / are added. These links can have multiple addresses and hence have to be careful if any one of those is IPv4 then broadcast bit has to be set.

You'd have to be careful and ignore IPv6 link local addresses. Those are added automatically whenever IPv6 is enabled and their presence does not mean the network is not IPv4 only.

But I don't like such magic behavior. It would lead to DHCP sometimes working and sometimes not in mixed v4/v6 environment depending on whether DHCPv4 or SLAAC was faster.

Could we perhaps add a flag when creating ipvlan interface stating whether IPv4 broadcast should be always enabled? Or, rather, the other way round - whether it should be disabled by default. Call it "nodhcp" or so.

Quoted 6 lines

Btw, speaking about IPv6 link local addresses, these actually do not work with ipvlan correctly. I'm getting DAD failures if I have more than one ipvlan interface, which is no wonder. This means that ipvlan cannot work with IPv6 reliably by default (unless you take care of ll address assignment and ensure all ipvlan interfaces get a different one).

Quoted 5 lines

ipvlan doesn't set dev_id. Once dev_id is set the kernel's IPv6LL address generation code will assign a different LL address to each ipvlan interface created from the same physical interface, despite that they have the same MAC address.

Yes, that was what my plan was but never got around fixing that

Quoted 7 lines

But of course you'd have to be careful to assign a *different* dev_id than any of that physical interface's non-ipvlan children too, and I have no idea how that would work since dev_id is currently done per-driver. eg, if you have a physical interface with dev_id=1 which you then create an ipvlan from, that ipvlan must not use dev_id=1 or it will be assigned the same IPv6LL address as the parent.

Quoted 10 lines

The description is very clear for dev_id (in netdevice.h). So the idea of using the subsequent numbers after master's id should be possible. After all these logical devices are going to share the same link. Most physical drivers don't assign dev-id so the beginning is 0x0 (for the physical driver) and from 0x1 can be assigned to the logical links. The definition is not clear in terms of what is the beginning (0x0 or 0x1) but from the code that generates the IPv6LL it's common that it's 0x0 hence logical links on top of these links can use 0x1 onward. However a check to see if the master-link has dev-id and staying clear of that should be sufficient.

My point was that if you have a parent with a non-zero dev_id, there can be other siblings of the parent that have a different dev_id and share the same MAC address. So creating an ipvlan with parent->dev_id + 1 doesn't work, because the parent may have a sibling with parent->dev_id
+ 1 and the same MAC address already.

Dan

Quoted 56 lines · Dan Williams

Quoted 44 lines · Mahesh Bandewar

Quoted 29 lines · Dan Williams

Quoted 21 lines · Jiri Benc

Quoted 6 lines · Mahesh Bandewar

The current logic disables broadcast by default and enables only when an IPv4 address is added. If this is inverted and - enables broadcast by default but disables it when only IPv6 address(es) is / are added. These links can have multiple addresses and hence have to be careful if any one of those is IPv4 then broadcast bit has to be set.

You'd have to be careful and ignore IPv6 link local addresses. Those are added automatically whenever IPv6 is enabled and their presence does not mean the network is not IPv4 only.

But I don't like such magic behavior. It would lead to DHCP sometimes working and sometimes not in mixed v4/v6 environment depending on whether DHCPv4 or SLAAC was faster.

Could we perhaps add a flag when creating ipvlan interface stating whether IPv4 broadcast should be always enabled? Or, rather, the other way round - whether it should be disabled by default. Call it "nodhcp" or so.

Quoted 6 lines

Btw, speaking about IPv6 link local addresses, these actually do not work with ipvlan correctly. I'm getting DAD failures if I have more than one ipvlan interface, which is no wonder. This means that ipvlan cannot work with IPv6 reliably by default (unless you take care of ll address assignment and ensure all ipvlan interfaces get a different one).

Quoted 5 lines

ipvlan doesn't set dev_id. Once dev_id is set the kernel's IPv6LL address generation code will assign a different LL address to each ipvlan interface created from the same physical interface, despite that they have the same MAC address.

Yes, that was what my plan was but never got around fixing that

Quoted 7 lines

But of course you'd have to be careful to assign a *different* dev_id than any of that physical interface's non-ipvlan children too, and I have no idea how that would work since dev_id is currently done per-driver. eg, if you have a physical interface with dev_id=1 which you then create an ipvlan from, that ipvlan must not use dev_id=1 or it will be assigned the same IPv6LL address as the parent.

Quoted 10 lines

The description is very clear for dev_id (in netdevice.h). So the idea of using the subsequent numbers after master's id should be possible. After all these logical devices are going to share the same link. Most physical drivers don't assign dev-id so the beginning is 0x0 (for the physical driver) and from 0x1 can be assigned to the logical links. The definition is not clear in terms of what is the beginning (0x0 or 0x1) but from the code that generates the IPv6LL it's common that it's 0x0 hence logical links on top of these links can use 0x1 onward. However a check to see if the master-link has dev-id and staying clear of that should be sufficient.

Quoted 6 lines

My point was that if you have a parent with a non-zero dev_id, there can be other siblings of the parent that have a different dev_id and share the same MAC address. So creating an ipvlan with parent->dev_id + 1 doesn't work, because the parent may have a sibling with parent->dev_id
+ 1 and the same MAC address already.

May be I'm missing something but is there a scenario where sibling (physical / port) will be sharing the same LL-address? The definition / description in netdevice.h is -

* @dev_id: Used to differentiate devices that share
* the same link layer address

So I's assuming the layered / stacked devices (children) rather than ports etc (siblings). What am I missing?

Quoted 70 lines · Mahesh Bandewar

Quoted 56 lines · Dan Williams

Quoted 44 lines · Mahesh Bandewar

Quoted 29 lines · Dan Williams

Quoted 21 lines · Jiri Benc

Quoted 6 lines · Mahesh Bandewar

The current logic disables broadcast by default and enables only when an IPv4 address is added. If this is inverted and - enables broadcast by default but disables it when only IPv6 address(es) is / are added. These links can have multiple addresses and hence have to be careful if any one of those is IPv4 then broadcast bit has to be set.

You'd have to be careful and ignore IPv6 link local addresses. Those are added automatically whenever IPv6 is enabled and their presence does not mean the network is not IPv4 only.

But I don't like such magic behavior. It would lead to DHCP sometimes working and sometimes not in mixed v4/v6 environment depending on whether DHCPv4 or SLAAC was faster.

Could we perhaps add a flag when creating ipvlan interface stating whether IPv4 broadcast should be always enabled? Or, rather, the other way round - whether it should be disabled by default. Call it "nodhcp" or so.

Quoted 6 lines

Btw, speaking about IPv6 link local addresses, these actually do not work with ipvlan correctly. I'm getting DAD failures if I have more than one ipvlan interface, which is no wonder. This means that ipvlan cannot work with IPv6 reliably by default (unless you take care of ll address assignment and ensure all ipvlan interfaces get a different one).

Quoted 5 lines

ipvlan doesn't set dev_id. Once dev_id is set the kernel's IPv6LL address generation code will assign a different LL address to each ipvlan interface created from the same physical interface, despite that they have the same MAC address.

Yes, that was what my plan was but never got around fixing that

Quoted 7 lines

But of course you'd have to be careful to assign a *different* dev_id than any of that physical interface's non-ipvlan children too, and I have no idea how that would work since dev_id is currently done per-driver. eg, if you have a physical interface with dev_id=1 which you then create an ipvlan from, that ipvlan must not use dev_id=1 or it will be assigned the same IPv6LL address as the parent.

Quoted 10 lines

The description is very clear for dev_id (in netdevice.h). So the idea of using the subsequent numbers after master's id should be possible. After all these logical devices are going to share the same link. Most physical drivers don't assign dev-id so the beginning is 0x0 (for the physical driver) and from 0x1 can be assigned to the logical links. The definition is not clear in terms of what is the beginning (0x0 or 0x1) but from the code that generates the IPv6LL it's common that it's 0x0 hence logical links on top of these links can use 0x1 onward. However a check to see if the master-link has dev-id and staying clear of that should be sufficient.

Quoted 6 lines

My point was that if you have a parent with a non-zero dev_id, there can be other siblings of the parent that have a different dev_id and share the same MAC address. So creating an ipvlan with parent->dev_id + 1 doesn't work, because the parent may have a sibling with parent->dev_id
+ 1 and the same MAC address already.

May be I'm missing something but is there a scenario where sibling (physical / port) will be sharing the same LL-address? The definition / description in netdevice.h is -

* @dev_id: Used to differentiate devices that share
* the same link layer address

Quoted 2 lines

So I's assuming the layered / stacked devices (children) rather than ports etc (siblings). What am I missing?

I don't think that distinction matters since you can create an ipvlan interface on top of any other interface except a macvlan. So any driver that sets dev_id could be the parent of an ipvlan interface. That appears to include some CAN devices and s390's qeth driver at the moment.

Dan

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) gets called after the address was added, it blows away the broadcast MAC address in mac_filters that was added at IPv4 address addition. Fix that.

Signed-off-by Dan Williams <[email protected]>

---
 drivers/net/ipvlan/ipvlan_main.c | 3 +++
 1 file changed, 3 insertions(+)

drivers/net/ipvlan/ipvlan_main.c +3 -1

index 4f4099d..d34f580 100644
@@ -241,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
 
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
+
+               if (ipvlan->ipv4cnt)
+                       ipvlan_set_broadcast_mac_filter(ipvlan, true);
        }
        dev_uc_sync(ipvlan->phy_dev, dev);
        dev_mc_sync(ipvlan->phy_dev, dev);
--

2.1.0

Quoted 8 lines · Dan Williams

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) gets called after the address was added, it blows away the broadcast MAC address in mac_filters that was added at IPv4 address addition. Fix that.

Signed-off-by Dan Williams <[email protected]>

Acked-by Mahesh Bandewar <[email protected]>

Quoted 19 lines

---
 drivers/net/ipvlan/ipvlan_main.c | 3 +++
 1 file changed, 3 insertions(+)

drivers/net/ipvlan/ipvlan_main.c +3 -1

index 4f4099d..d34f580 100644
@@ -241,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
 
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
+
+               if (ipvlan->ipv4cnt)
+                       ipvlan_set_broadcast_mac_filter(ipvlan, true);
        }
        dev_uc_sync(ipvlan->phy_dev, dev);
        dev_mc_sync(ipvlan->phy_dev, dev);
--

Quoted 3 lines

2.1.0

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Quoted 8 lines · Mahesh Bandewar

Quoted 7 lines · Dan Williams

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) gets called after the address was added, it blows away the broadcast MAC address in mac_filters that was added at IPv4 address addition. Fix that.

Quoted 2 lines

Quoted 1 line

Signed-off-by Dan Williams <[email protected]>

Acked-by Mahesh Bandewar <[email protected]>

I'm actually going to send another patch that supercedes this one and handles the DHCP issue in a slightly different way.

Dan

Quoted 26 lines

Quoted 19 lines

---
 drivers/net/ipvlan/ipvlan_main.c | 3 +++
 1 file changed, 3 insertions(+)

drivers/net/ipvlan/ipvlan_main.c +3 -1

index 4f4099d..d34f580 100644
@@ -241,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
 
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
+
+               if (ipvlan->ipv4cnt)
+                       ipvlan_set_broadcast_mac_filter(ipvlan, true);
        }
        dev_uc_sync(ipvlan->phy_dev, dev);
        dev_mc_sync(ipvlan->phy_dev, dev);
--

Quoted 3 lines

2.1.0

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Quoted 12 lines · Dan Williams

Quoted 10 lines · Mahesh Bandewar

Quoted 8 lines · Dan Williams

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) gets called after the address was added, it blows away the broadcast MAC address in mac_filters that was added at IPv4 address addition. Fix that.

Signed-off-by Dan Williams <[email protected]>

Acked-by Mahesh Bandewar <[email protected]>

Quoted 3 lines

I'm actually going to send another patch that supercedes this one and handles the DHCP issue in a slightly different way.

Sure, I'll take a look at that but irrespective of how DHCP is handled, this patch fixes the problem that you have described since ndo_set_rxmode will wipe the broadcast bit if set and will end up breaking the IPv4. So I feel that this is still required in some-form.

Quoted 30 lines

Dan

Quoted 26 lines

Quoted 19 lines

---
 drivers/net/ipvlan/ipvlan_main.c | 3 +++
 1 file changed, 3 insertions(+)

drivers/net/ipvlan/ipvlan_main.c +3 -1

index 4f4099d..d34f580 100644
@@ -241,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
 
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
+
+               if (ipvlan->ipv4cnt)
+                       ipvlan_set_broadcast_mac_filter(ipvlan, true);
        }
        dev_uc_sync(ipvlan->phy_dev, dev);
        dev_mc_sync(ipvlan->phy_dev, dev);
--

Quoted 3 lines

2.1.0

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The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) got called after the address was added, it would blow away the broadcast MAC address in mac_filters that was added at IPv4 address addition.

Next, ipvlan currently fails DHCP addressing for two reasons:

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient) which don't get checked against the address list.

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

To fix these issues, Watch for outgoing DHCP requests and enable the broadcast MAC address indefinitely when one is seen.

Signed-off-by Dan Williams <[email protected]>

---
NOTE: this patch supercedes my previous two ipvlan patches:
[PATCH 1/2] ipvlan: don't loose broadcast MAC when setting MAC filters [PATCH 2/2] ipvlan: always allow the broadcast MAC address

 drivers/net/ipvlan/ipvlan.h      |  2 ++
 drivers/net/ipvlan/ipvlan_core.c | 36 ++++++++++++++++++++++++++++++++++--
 drivers/net/ipvlan/ipvlan_main.c | 12 +++++++++---
 3 files changed, 45 insertions(+), 5 deletions(-)

drivers/net/ipvlan/ipvlan.h +2 -0

index 924ea98..7e0b8ff 100644
@@ -67,6 +67,7 @@ struct ipvl_dev {
 	struct list_head	addrs;
 	int			ipv4cnt;
 	int			ipv6cnt;
+	bool			dhcp4_seen;
 	struct ipvl_pcpu_stats	__percpu *pcpu_stats;
 	DECLARE_BITMAP(mac_filters, IPVLAN_MAC_FILTER_SIZE);
 	netdev_features_t	sfeatures;

@@ -118,4 +119,5 @@ bool ipvlan_addr_busy(struct ipvl_dev *ipvlan, void *iaddr, bool is_v6);
 struct ipvl_addr *ipvlan_ht_addr_lookup(const struct ipvl_port *port,
 					const void *iaddr, bool is_v6);
 void ipvlan_ht_addr_del(struct ipvl_addr *addr, bool sync);
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set);
 #endif /* __IPVLAN_H */

drivers/net/ipvlan/ipvlan_core.c +34 -2

index 2a17500..6dd992b 100644
@@ -126,6 +126,12 @@ static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type)
 		lyr3h = arph;
 		break;
 	}
+	case htons(ETH_P_ALL): {
+		/* Raw sockets */
+		if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
+			break;
+		/* Fall through */
+	}
 	case htons(ETH_P_IP): {
 		u32 pktlen;
 		struct iphdr *ip4h;

@@ -454,16 +460,42 @@ out:
 	return ipvlan_process_outbound(skb, ipvlan);
 }
 
+#define DHCP_PACKET_MIN_LEN 282
+
+static bool is_dhcp(struct sk_buff *skb)
+{
+	struct iphdr *ip4h = ip_hdr(skb);
+	struct udphdr *udph;
+
+	if (skb->len < DHCP_PACKET_MIN_LEN || ip4h->protocol != IPPROTO_UDP
+		|| ip_is_fragment(ip4h))
+		return false;
+
+	/* In the case of RAW sockets the transport header is not set by
+	 * the IP stack so we must set it ourselves.
+	 */
+	if (skb->transport_header == skb->network_header)
+		skb_set_transport_header(skb, ETH_HLEN + sizeof(struct iphdr));
+	udph = udp_hdr(skb);
+	return udph && udph->dest == htons(67) && udph->source == htons(68);
+}
+
 static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 {
-	const struct ipvl_dev *ipvlan = netdev_priv(dev);
+	struct ipvl_dev *ipvlan = netdev_priv(dev);
 	struct ethhdr *eth = eth_hdr(skb);
 	struct ipvl_addr *addr;
 	void *lyr3h;
 	int addr_type;
 
+	lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+	if (!ipvlan->dhcp4_seen && lyr3h && addr_type == IPVL_IPV4
+	    && is_dhcp(skb)) {
+		ipvlan->dhcp4_seen = true;
+		ipvlan_set_broadcast_mac_filter(ipvlan, true);
+	}
+
 	if (ether_addr_equal(eth->h_dest, eth->h_source)) {
-		lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
 		if (lyr3h) {
 			addr = ipvlan_addr_lookup(ipvlan->port, lyr3h, addr_type, true);
 			if (addr)

drivers/net/ipvlan/ipvlan_main.c +9 -3

index 4f4099d..a497fb9 100644
@@ -167,6 +167,8 @@ static int ipvlan_stop(struct net_device *dev)
 
 	dev_uc_del(phy_dev, phy_dev->dev_addr);
 
+	ipvlan->dhcp4_seen = false;
+
 	if (ipvlan->ipv6cnt > 0 || ipvlan->ipv4cnt > 0) {
 		list_for_each_entry(addr, &ipvlan->addrs, anode)
 			ipvlan_ht_addr_del(addr, !dev->dismantle);

@@ -214,7 +216,7 @@ static void ipvlan_change_rx_flags(struct net_device *dev, int change)
 		dev_set_allmulti(phy_dev, dev->flags & IFF_ALLMULTI? 1 : -1);
 }
 
-static void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
 {
 	struct net_device *dev = ipvlan->dev;
 	unsigned int hashbit = ipvlan_mac_hash(dev->broadcast);

@@ -239,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
 		netdev_for_each_mc_addr(ha, dev)
 			__set_bit(ipvlan_mac_hash(ha->addr), mc_filters);
 
+		if (ipvlan->ipv4cnt || ipvlan->dhcp4_seen)
+			__set_bit(ipvlan_mac_hash(dev->broadcast), mc_filters);
+
 		bitmap_copy(ipvlan->mac_filters, mc_filters,
 			    IPVLAN_MAC_FILTER_SIZE);
 	}

@@ -467,6 +472,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
 	INIT_LIST_HEAD(&ipvlan->addrs);
 	ipvlan->ipv4cnt = 0;
 	ipvlan->ipv6cnt = 0;
+	ipvlan->dhcp4_seen = false;
 
 	/* TODO Probably put random address here to be presented to the
 	 * world but keep using the physical-dev address for the outgoing

@@ -708,8 +714,8 @@ static void ipvlan_del_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
 	list_del_rcu(&addr->anode);
 	ipvlan->ipv4cnt--;
 	WARN_ON(ipvlan->ipv4cnt < 0);
-	if (!ipvlan->ipv4cnt)
-	    ipvlan_set_broadcast_mac_filter(ipvlan, false);
+	if (!ipvlan->ipv4cnt && !ipvlan->dhcp4_seen)
+		ipvlan_set_broadcast_mac_filter(ipvlan, false);
 	kfree_rcu(addr, rcu);
 
 	return;

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) got called after the address was added, it would blow away the broadcast MAC address in mac_filters that was added at IPv4 address addition.

Next, ipvlan currently fails DHCP addressing for two reasons:

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient) which don't get checked against the address list.

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

To fix these issues, Watch for outgoing DHCP requests and enable the broadcast MAC address indefinitely when one is seen.

Signed-off-by Dan Williams <[email protected]>

---
NOTE: this patch supercedes my previous two ipvlan patches:
[PATCH 1/2] ipvlan: don't loose broadcast MAC when setting MAC filters [PATCH 2/2] ipvlan: always allow the broadcast MAC address

 drivers/net/ipvlan/ipvlan.h      |  2 ++
 drivers/net/ipvlan/ipvlan_core.c | 36 ++++++++++++++++++++++++++++++++++--
 drivers/net/ipvlan/ipvlan_main.c | 12 +++++++++---
 3 files changed, 45 insertions(+), 5 deletions(-)

drivers/net/ipvlan/ipvlan.h +2 -0

index 924ea98..7e0b8ff 100644
@@ -67,6 +67,7 @@ struct ipvl_dev {
        struct list_head        addrs;
        int                     ipv4cnt;
        int                     ipv6cnt;
+       bool                    dhcp4_seen;
        struct ipvl_pcpu_stats  __percpu *pcpu_stats;
        DECLARE_BITMAP(mac_filters, IPVLAN_MAC_FILTER_SIZE);
        netdev_features_t       sfeatures;

@@ -118,4 +119,5 @@ bool ipvlan_addr_busy(struct ipvl_dev *ipvlan, void *iaddr, bool is_v6);
 struct ipvl_addr *ipvlan_ht_addr_lookup(const struct ipvl_port *port,
                                        const void *iaddr, bool is_v6);
 void ipvlan_ht_addr_del(struct ipvl_addr *addr, bool sync);
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set);
 #endif /* __IPVLAN_H */

drivers/net/ipvlan/ipvlan_core.c +34 -2

index 2a17500..6dd992b 100644
@@ -126,6 +126,12 @@ static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type)
                lyr3h = arph;
                break;
        }
+       case htons(ETH_P_ALL): {
+               /* Raw sockets */
+               if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
+                       break;
+               /* Fall through */
+       }
        case htons(ETH_P_IP): {
                u32 pktlen;
                struct iphdr *ip4h;

@@ -454,16 +460,42 @@ out:
        return ipvlan_process_outbound(skb, ipvlan);
 }
 
+#define DHCP_PACKET_MIN_LEN 282
+
+static bool is_dhcp(struct sk_buff *skb)
+{
+       struct iphdr *ip4h = ip_hdr(skb);
+       struct udphdr *udph;
+
+       if (skb->len < DHCP_PACKET_MIN_LEN || ip4h->protocol != IPPROTO_UDP
+               || ip_is_fragment(ip4h))
+               return false;
+
+       /* In the case of RAW sockets the transport header is not set by
+        * the IP stack so we must set it ourselves.
+        */
+       if (skb->transport_header == skb->network_header)
+               skb_set_transport_header(skb, ETH_HLEN + sizeof(struct iphdr));
+       udph = udp_hdr(skb);
+       return udph && udph->dest == htons(67) && udph->source == htons(68);
+}
+
 static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 {
-       const struct ipvl_dev *ipvlan = netdev_priv(dev);
+       struct ipvl_dev *ipvlan = netdev_priv(dev);
        struct ethhdr *eth = eth_hdr(skb);
        struct ipvl_addr *addr;
        void *lyr3h;
        int addr_type;
 
+       lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+       if (!ipvlan->dhcp4_seen && lyr3h && addr_type == IPVL_IPV4
+           && is_dhcp(skb)) {
+               ipvlan->dhcp4_seen = true;
+               ipvlan_set_broadcast_mac_filter(ipvlan, true);
+       }
+
        if (ether_addr_equal(eth->h_dest, eth->h_source)) {
-               lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
                if (lyr3h) {
                        addr = ipvlan_addr_lookup(ipvlan->port, lyr3h, addr_type, true);
                        if (addr)

drivers/net/ipvlan/ipvlan_main.c +9 -4

index 4f4099d..a497fb9 100644
@@ -167,6 +167,8 @@ static int ipvlan_stop(struct net_device *dev)
 
        dev_uc_del(phy_dev, phy_dev->dev_addr);
 
+       ipvlan->dhcp4_seen = false;
+
        if (ipvlan->ipv6cnt > 0 || ipvlan->ipv4cnt > 0) {
                list_for_each_entry(addr, &ipvlan->addrs, anode)
                        ipvlan_ht_addr_del(addr, !dev->dismantle);

@@ -214,7 +216,7 @@ static void ipvlan_change_rx_flags(struct net_device *dev, int change)
                dev_set_allmulti(phy_dev, dev->flags & IFF_ALLMULTI? 1 : -1);
 }
 
-static void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
 {
        struct net_device *dev = ipvlan->dev;
        unsigned int hashbit = ipvlan_mac_hash(dev->broadcast);

@@ -239,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
                netdev_for_each_mc_addr(ha, dev)
                        __set_bit(ipvlan_mac_hash(ha->addr), mc_filters);
 
+               if (ipvlan->ipv4cnt || ipvlan->dhcp4_seen)
+                       __set_bit(ipvlan_mac_hash(dev->broadcast), mc_filters);
+
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
        }

@@ -467,6 +472,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
        INIT_LIST_HEAD(&ipvlan->addrs);
        ipvlan->ipv4cnt = 0;
        ipvlan->ipv6cnt = 0;
+       ipvlan->dhcp4_seen = false;
 
        /* TODO Probably put random address here to be presented to the
         * world but keep using the physical-dev address for the outgoing

@@ -708,8 +714,8 @@ static void ipvlan_del_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_del_rcu(&addr->anode);
        ipvlan->ipv4cnt--;
        WARN_ON(ipvlan->ipv4cnt < 0);
-       if (!ipvlan->ipv4cnt)
-           ipvlan_set_broadcast_mac_filter(ipvlan, false);
+       if (!ipvlan->ipv4cnt && !ipvlan->dhcp4_seen)
+               ipvlan_set_broadcast_mac_filter(ipvlan, false);
        kfree_rcu(addr, rcu);
 
        return;
--

2.1.0

Quoted 9 lines · Dan Williams

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) got called after the address was added, it would blow away the broadcast MAC address in mac_filters that was added at IPv4 address addition.

Next, ipvlan currently fails DHCP addressing for two reasons:

I would prefer DHCPv4 instead of DHCP since it could also mean DHCPv6 which does not use broadcast.

Quoted 14 lines

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient) which don't get checked against the address list.

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

Quoted 3 lines

To fix these issues, Watch for outgoing DHCP requests and enable the broadcast MAC address indefinitely when one is seen.

This approach will work but adds a performance drag for all UDP traffic whether the link needs DHCPv4 or not (especially when it does not need). Logic works well only when the link (always) needs DHCPv4. When the link does not care about DHCPv4 the packet-inspection always happens.

Do we really need to special case DHCPv4? Do you see problems in inverting the current logic of adding broadcast bit (i.e. from enable-if-IPv4 to disable-if-IPv6-only)?

Quoted 143 lines

Signed-off-by Dan Williams <[email protected]>

---
NOTE: this patch supercedes my previous two ipvlan patches:
[PATCH 1/2] ipvlan: don't loose broadcast MAC when setting MAC filters [PATCH 2/2] ipvlan: always allow the broadcast MAC address

 drivers/net/ipvlan/ipvlan.h      |  2 ++
 drivers/net/ipvlan/ipvlan_core.c | 36 ++++++++++++++++++++++++++++++++++--
 drivers/net/ipvlan/ipvlan_main.c | 12 +++++++++---
 3 files changed, 45 insertions(+), 5 deletions(-)

drivers/net/ipvlan/ipvlan.h +2 -0

index 924ea98..7e0b8ff 100644
@@ -67,6 +67,7 @@ struct ipvl_dev {
        struct list_head        addrs;
        int                     ipv4cnt;
        int                     ipv6cnt;
+       bool                    dhcp4_seen;
        struct ipvl_pcpu_stats  __percpu *pcpu_stats;
        DECLARE_BITMAP(mac_filters, IPVLAN_MAC_FILTER_SIZE);
        netdev_features_t       sfeatures;

@@ -118,4 +119,5 @@ bool ipvlan_addr_busy(struct ipvl_dev *ipvlan, void *iaddr, bool is_v6);
 struct ipvl_addr *ipvlan_ht_addr_lookup(const struct ipvl_port *port,
                                        const void *iaddr, bool is_v6);
 void ipvlan_ht_addr_del(struct ipvl_addr *addr, bool sync);
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set);
 #endif /* __IPVLAN_H */

drivers/net/ipvlan/ipvlan_core.c +34 -2

index 2a17500..6dd992b 100644
@@ -126,6 +126,12 @@ static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type)
                lyr3h = arph;
                break;
        }
+       case htons(ETH_P_ALL): {
+               /* Raw sockets */
+               if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
+                       break;
+               /* Fall through */
+       }
        case htons(ETH_P_IP): {
                u32 pktlen;
                struct iphdr *ip4h;

@@ -454,16 +460,42 @@ out:
        return ipvlan_process_outbound(skb, ipvlan);
 }
 
+#define DHCP_PACKET_MIN_LEN 282
+
+static bool is_dhcp(struct sk_buff *skb)
+{
+       struct iphdr *ip4h = ip_hdr(skb);
+       struct udphdr *udph;
+
+       if (skb->len < DHCP_PACKET_MIN_LEN || ip4h->protocol != IPPROTO_UDP
+               || ip_is_fragment(ip4h))
+               return false;
+
+       /* In the case of RAW sockets the transport header is not set by
+        * the IP stack so we must set it ourselves.
+        */
+       if (skb->transport_header == skb->network_header)
+               skb_set_transport_header(skb, ETH_HLEN + sizeof(struct iphdr));
+       udph = udp_hdr(skb);
+       return udph && udph->dest == htons(67) && udph->source == htons(68);
+}
+
 static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 {
-       const struct ipvl_dev *ipvlan = netdev_priv(dev);
+       struct ipvl_dev *ipvlan = netdev_priv(dev);
        struct ethhdr *eth = eth_hdr(skb);
        struct ipvl_addr *addr;
        void *lyr3h;
        int addr_type;
 
+       lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+       if (!ipvlan->dhcp4_seen && lyr3h && addr_type == IPVL_IPV4
+           && is_dhcp(skb)) {
+               ipvlan->dhcp4_seen = true;
+               ipvlan_set_broadcast_mac_filter(ipvlan, true);
+       }
+
        if (ether_addr_equal(eth->h_dest, eth->h_source)) {
-               lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
                if (lyr3h) {
                        addr = ipvlan_addr_lookup(ipvlan->port, lyr3h, addr_type, true);
                        if (addr)

drivers/net/ipvlan/ipvlan_main.c +9 -4

index 4f4099d..a497fb9 100644
@@ -167,6 +167,8 @@ static int ipvlan_stop(struct net_device *dev)
 
        dev_uc_del(phy_dev, phy_dev->dev_addr);
 
+       ipvlan->dhcp4_seen = false;
+
        if (ipvlan->ipv6cnt > 0 || ipvlan->ipv4cnt > 0) {
                list_for_each_entry(addr, &ipvlan->addrs, anode)
                        ipvlan_ht_addr_del(addr, !dev->dismantle);

@@ -214,7 +216,7 @@ static void ipvlan_change_rx_flags(struct net_device *dev, int change)
                dev_set_allmulti(phy_dev, dev->flags & IFF_ALLMULTI? 1 : -1);
 }
 
-static void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
 {
        struct net_device *dev = ipvlan->dev;
        unsigned int hashbit = ipvlan_mac_hash(dev->broadcast);

@@ -239,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
                netdev_for_each_mc_addr(ha, dev)
                        __set_bit(ipvlan_mac_hash(ha->addr), mc_filters);
 
+               if (ipvlan->ipv4cnt || ipvlan->dhcp4_seen)
+                       __set_bit(ipvlan_mac_hash(dev->broadcast), mc_filters);
+
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
        }

@@ -467,6 +472,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
        INIT_LIST_HEAD(&ipvlan->addrs);
        ipvlan->ipv4cnt = 0;
        ipvlan->ipv6cnt = 0;
+       ipvlan->dhcp4_seen = false;
 
        /* TODO Probably put random address here to be presented to the
         * world but keep using the physical-dev address for the outgoing

@@ -708,8 +714,8 @@ static void ipvlan_del_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_del_rcu(&addr->anode);
        ipvlan->ipv4cnt--;
        WARN_ON(ipvlan->ipv4cnt < 0);
-       if (!ipvlan->ipv4cnt)
-           ipvlan_set_broadcast_mac_filter(ipvlan, false);
+       if (!ipvlan->ipv4cnt && !ipvlan->dhcp4_seen)
+               ipvlan_set_broadcast_mac_filter(ipvlan, false);
        kfree_rcu(addr, rcu);
 
        return;
--

Quoted 3 lines

2.1.0

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Quoted 30 lines · Mahesh Bandewar

Quoted 9 lines · Dan Williams

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) got called after the address was added, it would blow away the broadcast MAC address in mac_filters that was added at IPv4 address addition.

Next, ipvlan currently fails DHCP addressing for two reasons:

I would prefer DHCPv4 instead of DHCP since it could also mean DHCPv6 which does not use broadcast.

Quoted 17 lines

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient) which don't get checked against the address list.

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

To fix these issues, Watch for outgoing DHCP requests and enable the broadcast MAC address indefinitely when one is seen.

Quoted 5 lines

This approach will work but adds a performance drag for all UDP traffic whether the link needs DHCPv4 or not (especially when it does not need). Logic works well only when the link (always) needs DHCPv4. When the link does not care about DHCPv4 the packet-inspection always happens.

If DHCPv4 is detected on a link, doesn't that mean the link needs the broadcast filter enabled?

If you start DHCPv4 on the link you obviously
expect it to work, unless there's no DHCPv4 server available. The patch should also reset the broadcast filter on close, so network management could simply start DHCPv4, watch it fail, close/open and set static IP.

Alternatively we could have the broadcast filter on a 2 minute timer that starts when DHCPv4 is seen.

Quoted 3 lines

Do we really need to special case DHCPv4? Do you see problems in inverting the current logic of adding broadcast bit (i.e. from enable-if-IPv4 to disable-if-IPv6-only)?

The problem with this is dual-stack configuration. Typically both DHCPv4 and SLAAC are started in this case, and often SLAAC will complete earlier. So now the interface only has an IPv6 address but DHCPv4 is still ongoing; as I understand your proposal the filter would now block broadcast packets that DHCPv4 is listening for.

Dan

Quoted 150 lines

Quoted 143 lines

Signed-off-by Dan Williams <[email protected]>

---
NOTE: this patch supercedes my previous two ipvlan patches:
[PATCH 1/2] ipvlan: don't loose broadcast MAC when setting MAC filters [PATCH 2/2] ipvlan: always allow the broadcast MAC address

 drivers/net/ipvlan/ipvlan.h      |  2 ++
 drivers/net/ipvlan/ipvlan_core.c | 36 ++++++++++++++++++++++++++++++++++--
 drivers/net/ipvlan/ipvlan_main.c | 12 +++++++++---
 3 files changed, 45 insertions(+), 5 deletions(-)

drivers/net/ipvlan/ipvlan.h +2 -0

index 924ea98..7e0b8ff 100644
@@ -67,6 +67,7 @@ struct ipvl_dev {
        struct list_head        addrs;
        int                     ipv4cnt;
        int                     ipv6cnt;
+       bool                    dhcp4_seen;
        struct ipvl_pcpu_stats  __percpu *pcpu_stats;
        DECLARE_BITMAP(mac_filters, IPVLAN_MAC_FILTER_SIZE);
        netdev_features_t       sfeatures;

@@ -118,4 +119,5 @@ bool ipvlan_addr_busy(struct ipvl_dev *ipvlan, void *iaddr, bool is_v6);
 struct ipvl_addr *ipvlan_ht_addr_lookup(const struct ipvl_port *port,
                                        const void *iaddr, bool is_v6);
 void ipvlan_ht_addr_del(struct ipvl_addr *addr, bool sync);
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set);
 #endif /* __IPVLAN_H */

drivers/net/ipvlan/ipvlan_core.c +34 -2

index 2a17500..6dd992b 100644
@@ -126,6 +126,12 @@ static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type)
                lyr3h = arph;
                break;
        }
+       case htons(ETH_P_ALL): {
+               /* Raw sockets */
+               if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
+                       break;
+               /* Fall through */
+       }
        case htons(ETH_P_IP): {
                u32 pktlen;
                struct iphdr *ip4h;

@@ -454,16 +460,42 @@ out:
        return ipvlan_process_outbound(skb, ipvlan);
 }
 
+#define DHCP_PACKET_MIN_LEN 282
+
+static bool is_dhcp(struct sk_buff *skb)
+{
+       struct iphdr *ip4h = ip_hdr(skb);
+       struct udphdr *udph;
+
+       if (skb->len < DHCP_PACKET_MIN_LEN || ip4h->protocol != IPPROTO_UDP
+               || ip_is_fragment(ip4h))
+               return false;
+
+       /* In the case of RAW sockets the transport header is not set by
+        * the IP stack so we must set it ourselves.
+        */
+       if (skb->transport_header == skb->network_header)
+               skb_set_transport_header(skb, ETH_HLEN + sizeof(struct iphdr));
+       udph = udp_hdr(skb);
+       return udph && udph->dest == htons(67) && udph->source == htons(68);
+}
+
 static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 {
-       const struct ipvl_dev *ipvlan = netdev_priv(dev);
+       struct ipvl_dev *ipvlan = netdev_priv(dev);
        struct ethhdr *eth = eth_hdr(skb);
        struct ipvl_addr *addr;
        void *lyr3h;
        int addr_type;
 
+       lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+       if (!ipvlan->dhcp4_seen && lyr3h && addr_type == IPVL_IPV4
+           && is_dhcp(skb)) {
+               ipvlan->dhcp4_seen = true;
+               ipvlan_set_broadcast_mac_filter(ipvlan, true);
+       }
+
        if (ether_addr_equal(eth->h_dest, eth->h_source)) {
-               lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
                if (lyr3h) {
                        addr = ipvlan_addr_lookup(ipvlan->port, lyr3h, addr_type, true);
                        if (addr)

drivers/net/ipvlan/ipvlan_main.c +9 -4

index 4f4099d..a497fb9 100644
@@ -167,6 +167,8 @@ static int ipvlan_stop(struct net_device *dev)
 
        dev_uc_del(phy_dev, phy_dev->dev_addr);
 
+       ipvlan->dhcp4_seen = false;
+
        if (ipvlan->ipv6cnt > 0 || ipvlan->ipv4cnt > 0) {
                list_for_each_entry(addr, &ipvlan->addrs, anode)
                        ipvlan_ht_addr_del(addr, !dev->dismantle);

@@ -214,7 +216,7 @@ static void ipvlan_change_rx_flags(struct net_device *dev, int change)
                dev_set_allmulti(phy_dev, dev->flags & IFF_ALLMULTI? 1 : -1);
 }
 
-static void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
 {
        struct net_device *dev = ipvlan->dev;
        unsigned int hashbit = ipvlan_mac_hash(dev->broadcast);

@@ -239,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
                netdev_for_each_mc_addr(ha, dev)
                        __set_bit(ipvlan_mac_hash(ha->addr), mc_filters);
 
+               if (ipvlan->ipv4cnt || ipvlan->dhcp4_seen)
+                       __set_bit(ipvlan_mac_hash(dev->broadcast), mc_filters);
+
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
        }

@@ -467,6 +472,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
        INIT_LIST_HEAD(&ipvlan->addrs);
        ipvlan->ipv4cnt = 0;
        ipvlan->ipv6cnt = 0;
+       ipvlan->dhcp4_seen = false;
 
        /* TODO Probably put random address here to be presented to the
         * world but keep using the physical-dev address for the outgoing

@@ -708,8 +714,8 @@ static void ipvlan_del_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_del_rcu(&addr->anode);
        ipvlan->ipv4cnt--;
        WARN_ON(ipvlan->ipv4cnt < 0);
-       if (!ipvlan->ipv4cnt)
-           ipvlan_set_broadcast_mac_filter(ipvlan, false);
+       if (!ipvlan->ipv4cnt && !ipvlan->dhcp4_seen)
+               ipvlan_set_broadcast_mac_filter(ipvlan, false);
        kfree_rcu(addr, rcu);
 
        return;
--

Quoted 3 lines

2.1.0

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Quoted 37 lines · Dan Williams

Quoted 35 lines · Mahesh Bandewar

Quoted 9 lines · Dan Williams

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) got called after the address was added, it would blow away the broadcast MAC address in mac_filters that was added at IPv4 address addition.

Next, ipvlan currently fails DHCP addressing for two reasons:

I would prefer DHCPv4 instead of DHCP since it could also mean DHCPv6 which does not use broadcast.

Quoted 9 lines

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient) which don't get checked against the address list.

Quoted 8 lines

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

To fix these issues, Watch for outgoing DHCP requests and enable the broadcast MAC address indefinitely when one is seen.

This approach will work but adds a performance drag for all UDP traffic whether the link needs DHCPv4 or not (especially when it does not need). Logic works well only when the link (always) needs DHCPv4. When the link does not care about DHCPv4 the packet-inspection always happens.

Quoted 2 lines

If DHCPv4 is detected on a link, doesn't that mean the link needs the broadcast filter enabled?

Yes and it should stay enabled as it's going to have IPv4. Also once broadcast bit is set there should not be any additional jugglery / packet inspection which hurts performance.

Quoted 8 lines

If you start DHCPv4 on the link you obviously
expect it to work, unless there's no DHCPv4 server available. The patch should also reset the broadcast filter on close, so network management could simply start DHCPv4, watch it fail, close/open and set static IP.

Alternatively we could have the broadcast filter on a 2 minute timer that starts when DHCPv4 is seen.

Well, but this would be error-prone. I don't remember but DHCP timeout is not just 2 minutes.

Quoted 10 lines

Quoted 3 lines

Do we really need to special case DHCPv4? Do you see problems in inverting the current logic of adding broadcast bit (i.e. from enable-if-IPv4 to disable-if-IPv6-only)?

The problem with this is dual-stack configuration. Typically both DHCPv4 and SLAAC are started in this case, and often SLAAC will complete earlier. So now the interface only has an IPv6 address but DHCPv4 is still ongoing; as I understand your proposal the filter would now block broadcast packets that DHCPv4 is listening for.

That was a proposal and we can tweak it if necessary. My primary concern is that the solution should not make us pay per packet penalty once (and even if not) the DHCPv4 handshake is complete, which is not the case as it stands now.

Quoted 154 lines

Dan

Quoted 150 lines

Quoted 143 lines

Signed-off-by Dan Williams <[email protected]>

---
NOTE: this patch supercedes my previous two ipvlan patches:
[PATCH 1/2] ipvlan: don't loose broadcast MAC when setting MAC filters [PATCH 2/2] ipvlan: always allow the broadcast MAC address

 drivers/net/ipvlan/ipvlan.h      |  2 ++
 drivers/net/ipvlan/ipvlan_core.c | 36 ++++++++++++++++++++++++++++++++++--
 drivers/net/ipvlan/ipvlan_main.c | 12 +++++++++---
 3 files changed, 45 insertions(+), 5 deletions(-)

drivers/net/ipvlan/ipvlan.h +2 -0

index 924ea98..7e0b8ff 100644
@@ -67,6 +67,7 @@ struct ipvl_dev {
        struct list_head        addrs;
        int                     ipv4cnt;
        int                     ipv6cnt;
+       bool                    dhcp4_seen;
        struct ipvl_pcpu_stats  __percpu *pcpu_stats;
        DECLARE_BITMAP(mac_filters, IPVLAN_MAC_FILTER_SIZE);
        netdev_features_t       sfeatures;

@@ -118,4 +119,5 @@ bool ipvlan_addr_busy(struct ipvl_dev *ipvlan, void *iaddr, bool is_v6);
 struct ipvl_addr *ipvlan_ht_addr_lookup(const struct ipvl_port *port,
                                        const void *iaddr, bool is_v6);
 void ipvlan_ht_addr_del(struct ipvl_addr *addr, bool sync);
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set);
 #endif /* __IPVLAN_H */

drivers/net/ipvlan/ipvlan_core.c +34 -2

index 2a17500..6dd992b 100644
@@ -126,6 +126,12 @@ static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type)
                lyr3h = arph;
                break;
        }
+       case htons(ETH_P_ALL): {
+               /* Raw sockets */
+               if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
+                       break;
+               /* Fall through */
+       }
        case htons(ETH_P_IP): {
                u32 pktlen;
                struct iphdr *ip4h;

@@ -454,16 +460,42 @@ out:
        return ipvlan_process_outbound(skb, ipvlan);
 }
 
+#define DHCP_PACKET_MIN_LEN 282
+
+static bool is_dhcp(struct sk_buff *skb)
+{
+       struct iphdr *ip4h = ip_hdr(skb);
+       struct udphdr *udph;
+
+       if (skb->len < DHCP_PACKET_MIN_LEN || ip4h->protocol != IPPROTO_UDP
+               || ip_is_fragment(ip4h))
+               return false;
+
+       /* In the case of RAW sockets the transport header is not set by
+        * the IP stack so we must set it ourselves.
+        */
+       if (skb->transport_header == skb->network_header)
+               skb_set_transport_header(skb, ETH_HLEN + sizeof(struct iphdr));
+       udph = udp_hdr(skb);
+       return udph && udph->dest == htons(67) && udph->source == htons(68);
+}
+
 static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 {
-       const struct ipvl_dev *ipvlan = netdev_priv(dev);
+       struct ipvl_dev *ipvlan = netdev_priv(dev);
        struct ethhdr *eth = eth_hdr(skb);
        struct ipvl_addr *addr;
        void *lyr3h;
        int addr_type;
 
+       lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+       if (!ipvlan->dhcp4_seen && lyr3h && addr_type == IPVL_IPV4
+           && is_dhcp(skb)) {
+               ipvlan->dhcp4_seen = true;
+               ipvlan_set_broadcast_mac_filter(ipvlan, true);
+       }
+
        if (ether_addr_equal(eth->h_dest, eth->h_source)) {
-               lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
                if (lyr3h) {
                        addr = ipvlan_addr_lookup(ipvlan->port, lyr3h, addr_type, true);
                        if (addr)

drivers/net/ipvlan/ipvlan_main.c +9 -4

index 4f4099d..a497fb9 100644
@@ -167,6 +167,8 @@ static int ipvlan_stop(struct net_device *dev)
 
        dev_uc_del(phy_dev, phy_dev->dev_addr);
 
+       ipvlan->dhcp4_seen = false;
+
        if (ipvlan->ipv6cnt > 0 || ipvlan->ipv4cnt > 0) {
                list_for_each_entry(addr, &ipvlan->addrs, anode)
                        ipvlan_ht_addr_del(addr, !dev->dismantle);

@@ -214,7 +216,7 @@ static void ipvlan_change_rx_flags(struct net_device *dev, int change)
                dev_set_allmulti(phy_dev, dev->flags & IFF_ALLMULTI? 1 : -1);
 }
 
-static void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
 {
        struct net_device *dev = ipvlan->dev;
        unsigned int hashbit = ipvlan_mac_hash(dev->broadcast);

@@ -239,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
                netdev_for_each_mc_addr(ha, dev)
                        __set_bit(ipvlan_mac_hash(ha->addr), mc_filters);
 
+               if (ipvlan->ipv4cnt || ipvlan->dhcp4_seen)
+                       __set_bit(ipvlan_mac_hash(dev->broadcast), mc_filters);
+
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
        }

@@ -467,6 +472,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
        INIT_LIST_HEAD(&ipvlan->addrs);
        ipvlan->ipv4cnt = 0;
        ipvlan->ipv6cnt = 0;
+       ipvlan->dhcp4_seen = false;
 
        /* TODO Probably put random address here to be presented to the
         * world but keep using the physical-dev address for the outgoing

@@ -708,8 +714,8 @@ static void ipvlan_del_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_del_rcu(&addr->anode);
        ipvlan->ipv4cnt--;
        WARN_ON(ipvlan->ipv4cnt < 0);
-       if (!ipvlan->ipv4cnt)
-           ipvlan_set_broadcast_mac_filter(ipvlan, false);
+       if (!ipvlan->ipv4cnt && !ipvlan->dhcp4_seen)
+               ipvlan_set_broadcast_mac_filter(ipvlan, false);
        kfree_rcu(addr, rcu);
 
        return;
--

Quoted 3 lines

2.1.0

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From: Dan Williams <[email protected]>
Date: Mon, 30 Mar 2015 23:22:50 -0500

drivers/net/ipvlan/ipvlan_core.c static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type) · line 134

Quoted 6 lines

drivers/net/ipvlan/ipvlan_core.c +6 -0

+	case htons(ETH_P_ALL): {
+		/* Raw sockets */
+		if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
+			break;
+		/* Fall through */
+	}

You are not declaring any local variables in this switch block, therefore there is no reason to surround it with curly braces, remove them.

drivers/net/ipvlan/ipvlan_core.c out: · line 472

Quoted 3 lines

drivers/net/ipvlan/ipvlan_core.c +3 -0

+	if (skb->len < DHCP_PACKET_MIN_LEN || ip4h->protocol != IPPROTO_UDP
+		|| ip_is_fragment(ip4h))
+		return false;

This is not formatted properly.

Lines of conditional statements _END_ with operators, they should never begin with one.

Also, the second and subsequent lines of a multi-line if() statement should begin precisely at the first column after the openning parenthesis of the first line. You must use the appropriate number of TAB then SPACE characters to achieve this.

If you are purely using TAB characters to indent these things, it is almost certain that you are doing it wrong.

And yes, I am super sick of typing this in several times a day, especially when this is not only documented, but checked for by checkpatch and other automated tools.

drivers/net/ipvlan/ipvlan_core.c out: · line 493

Quoted 3 lines

drivers/net/ipvlan/ipvlan_core.c +3 -0

+	lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+	if (!ipvlan->dhcp4_seen && lyr3h && addr_type == IPVL_IPV4
+	    && is_dhcp(skb)) {

Likewise.

Quoted 34 lines · David Miller

From: Dan Williams <[email protected]>
Date: Mon, 30 Mar 2015 23:22:50 -0500

drivers/net/ipvlan/ipvlan_core.c static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type) · line 134

Quoted 6 lines

drivers/net/ipvlan/ipvlan_core.c +6 -0

+	case htons(ETH_P_ALL): {
+		/* Raw sockets */
+		if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
+			break;
+		/* Fall through */
+	}

You are not declaring any local variables in this switch block, therefore there is no reason to surround it with curly braces, remove them.

drivers/net/ipvlan/ipvlan_core.c out: · line 472

Quoted 3 lines

drivers/net/ipvlan/ipvlan_core.c +3 -0

+	if (skb->len < DHCP_PACKET_MIN_LEN || ip4h->protocol != IPPROTO_UDP
+		|| ip_is_fragment(ip4h))
+		return false;

This is not formatted properly.

Lines of conditional statements _END_ with operators, they should never begin with one.

Also, the second and subsequent lines of a multi-line if() statement should begin precisely at the first column after the openning parenthesis of the first line. You must use the appropriate number of TAB then SPACE characters to achieve this.

If you are purely using TAB characters to indent these things, it is almost certain that you are doing it wrong.

And yes, I am super sick of typing this in several times a day, especially when this is not only documented, but checked for by checkpatch and other automated tools.

Quoted 5 lines

drivers/net/ipvlan/ipvlan_core.c out: · line 493

Quoted 3 lines

drivers/net/ipvlan/ipvlan_core.c +3 -0

+	lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+	if (!ipvlan->dhcp4_seen && lyr3h && addr_type == IPVL_IPV4
+	    && is_dhcp(skb)) {

Likewise.

I'm sorry about that, and I will fix style/indent and re-post once Mahesh and I have agreed on the exact behavior here.

Quoted 40 lines · Mahesh Bandewar

Quoted 39 lines · Dan Williams

Quoted 27 lines · Mahesh Bandewar

Quoted 9 lines · Dan Williams

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) got called after the address was added, it would blow away the broadcast MAC address in mac_filters that was added at IPv4 address addition.

Next, ipvlan currently fails DHCP addressing for two reasons:

I would prefer DHCPv4 instead of DHCP since it could also mean DHCPv6 which does not use broadcast.

Quoted 14 lines

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient) which don't get checked against the address list.

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

Quoted 8 lines

Quoted 3 lines

To fix these issues, Watch for outgoing DHCP requests and enable the broadcast MAC address indefinitely when one is seen.

This approach will work but adds a performance drag for all UDP traffic whether the link needs DHCPv4 or not (especially when it does not need). Logic works well only when the link (always) needs DHCPv4. When the link does not care about DHCPv4 the packet-inspection always happens.

If DHCPv4 is detected on a link, doesn't that mean the link needs the broadcast filter enabled?

Quoted 3 lines

Yes and it should stay enabled as it's going to have IPv4. Also once broadcast bit is set there should not be any additional jugglery / packet inspection which hurts performance.

Yes, which is why my patch includes the check for dhcp4_seen and skips inspecting the packet. I could modify it to skip the L3 header check too in that case.

Quoted 10 lines

Quoted 8 lines

If you start DHCPv4 on the link you obviously
expect it to work, unless there's no DHCPv4 server available. The patch should also reset the broadcast filter on close, so network management could simply start DHCPv4, watch it fail, close/open and set static IP.

Alternatively we could have the broadcast filter on a 2 minute timer that starts when DHCPv4 is seen.

Well, but this would be error-prone. I don't remember but DHCP timeout is not just 2 minutes.

2m is IIRC an RFC recommended timeout for initial DHCPv4 requests. If you don't get a reply to your requests within 2m, you aren't likely to get one ever on this network and you can stop trying for a while. You either get a reply in which case you get an IPv4 address and broadcast is always enabled, or you don't, in which case you don't really need broadcast. Then when userspace next tries DHCP, the timer would allow broadcast for another 2 minutes.

Quoted 10 lines

Quoted 10 lines

Quoted 3 lines

Do we really need to special case DHCPv4? Do you see problems in inverting the current logic of adding broadcast bit (i.e. from enable-if-IPv4 to disable-if-IPv6-only)?

The problem with this is dual-stack configuration. Typically both DHCPv4 and SLAAC are started in this case, and often SLAAC will complete earlier. So now the interface only has an IPv6 address but DHCPv4 is still ongoing; as I understand your proposal the filter would now block broadcast packets that DHCPv4 is listening for.

Quoted 4 lines

That was a proposal and we can tweak it if necessary. My primary concern is that the solution should not make us pay per packet penalty once (and even if not) the DHCPv4 handshake is complete, which is not the case as it stands now.

I'm not sure what you mean by "not make us pay a per packet penalty once DHCPv4 is complete". Once an IPv4 address is assigned, the broadcast filter must allow broadcast packets. Before an IPv4 address is assigned, the driver must watch for DHCPv4 and allow broadcast packets so that the DHCP reply isn't missed.

If DHCPv4 gets no response, then there are two options:

a) down the interface (which resets the broadcast filter to block broadcast packets) and re-up it, and don't do DHCPv4 again

b) have a timer in the driver that waits a period of time for an IPv4 address after a DHCPv4 request, and blocks broadcast when the timer expires

Dan

Quoted 158 lines

Quoted 154 lines

Dan

Quoted 150 lines

Quoted 143 lines

Signed-off-by Dan Williams <[email protected]>

---
NOTE: this patch supercedes my previous two ipvlan patches:
[PATCH 1/2] ipvlan: don't loose broadcast MAC when setting MAC filters [PATCH 2/2] ipvlan: always allow the broadcast MAC address

 drivers/net/ipvlan/ipvlan.h      |  2 ++
 drivers/net/ipvlan/ipvlan_core.c | 36 ++++++++++++++++++++++++++++++++++--
 drivers/net/ipvlan/ipvlan_main.c | 12 +++++++++---
 3 files changed, 45 insertions(+), 5 deletions(-)

drivers/net/ipvlan/ipvlan.h +2 -0

index 924ea98..7e0b8ff 100644
@@ -67,6 +67,7 @@ struct ipvl_dev {
        struct list_head        addrs;
        int                     ipv4cnt;
        int                     ipv6cnt;
+       bool                    dhcp4_seen;
        struct ipvl_pcpu_stats  __percpu *pcpu_stats;
        DECLARE_BITMAP(mac_filters, IPVLAN_MAC_FILTER_SIZE);
        netdev_features_t       sfeatures;

@@ -118,4 +119,5 @@ bool ipvlan_addr_busy(struct ipvl_dev *ipvlan, void *iaddr, bool is_v6);
 struct ipvl_addr *ipvlan_ht_addr_lookup(const struct ipvl_port *port,
                                        const void *iaddr, bool is_v6);
 void ipvlan_ht_addr_del(struct ipvl_addr *addr, bool sync);
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set);
 #endif /* __IPVLAN_H */

drivers/net/ipvlan/ipvlan_core.c +34 -2

index 2a17500..6dd992b 100644
@@ -126,6 +126,12 @@ static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type)
                lyr3h = arph;
                break;
        }
+       case htons(ETH_P_ALL): {
+               /* Raw sockets */
+               if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
+                       break;
+               /* Fall through */
+       }
        case htons(ETH_P_IP): {
                u32 pktlen;
                struct iphdr *ip4h;

@@ -454,16 +460,42 @@ out:
        return ipvlan_process_outbound(skb, ipvlan);
 }
 
+#define DHCP_PACKET_MIN_LEN 282
+
+static bool is_dhcp(struct sk_buff *skb)
+{
+       struct iphdr *ip4h = ip_hdr(skb);
+       struct udphdr *udph;
+
+       if (skb->len < DHCP_PACKET_MIN_LEN || ip4h->protocol != IPPROTO_UDP
+               || ip_is_fragment(ip4h))
+               return false;
+
+       /* In the case of RAW sockets the transport header is not set by
+        * the IP stack so we must set it ourselves.
+        */
+       if (skb->transport_header == skb->network_header)
+               skb_set_transport_header(skb, ETH_HLEN + sizeof(struct iphdr));
+       udph = udp_hdr(skb);
+       return udph && udph->dest == htons(67) && udph->source == htons(68);
+}
+
 static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 {
-       const struct ipvl_dev *ipvlan = netdev_priv(dev);
+       struct ipvl_dev *ipvlan = netdev_priv(dev);
        struct ethhdr *eth = eth_hdr(skb);
        struct ipvl_addr *addr;
        void *lyr3h;
        int addr_type;
 
+       lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+       if (!ipvlan->dhcp4_seen && lyr3h && addr_type == IPVL_IPV4
+           && is_dhcp(skb)) {
+               ipvlan->dhcp4_seen = true;
+               ipvlan_set_broadcast_mac_filter(ipvlan, true);
+       }
+
        if (ether_addr_equal(eth->h_dest, eth->h_source)) {
-               lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
                if (lyr3h) {
                        addr = ipvlan_addr_lookup(ipvlan->port, lyr3h, addr_type, true);
                        if (addr)

drivers/net/ipvlan/ipvlan_main.c +9 -4

index 4f4099d..a497fb9 100644
@@ -167,6 +167,8 @@ static int ipvlan_stop(struct net_device *dev)
 
        dev_uc_del(phy_dev, phy_dev->dev_addr);
 
+       ipvlan->dhcp4_seen = false;
+
        if (ipvlan->ipv6cnt > 0 || ipvlan->ipv4cnt > 0) {
                list_for_each_entry(addr, &ipvlan->addrs, anode)
                        ipvlan_ht_addr_del(addr, !dev->dismantle);

@@ -214,7 +216,7 @@ static void ipvlan_change_rx_flags(struct net_device *dev, int change)
                dev_set_allmulti(phy_dev, dev->flags & IFF_ALLMULTI? 1 : -1);
 }
 
-static void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
 {
        struct net_device *dev = ipvlan->dev;
        unsigned int hashbit = ipvlan_mac_hash(dev->broadcast);

@@ -239,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
                netdev_for_each_mc_addr(ha, dev)
                        __set_bit(ipvlan_mac_hash(ha->addr), mc_filters);
 
+               if (ipvlan->ipv4cnt || ipvlan->dhcp4_seen)
+                       __set_bit(ipvlan_mac_hash(dev->broadcast), mc_filters);
+
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
        }

@@ -467,6 +472,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
        INIT_LIST_HEAD(&ipvlan->addrs);
        ipvlan->ipv4cnt = 0;
        ipvlan->ipv6cnt = 0;
+       ipvlan->dhcp4_seen = false;
 
        /* TODO Probably put random address here to be presented to the
         * world but keep using the physical-dev address for the outgoing

@@ -708,8 +714,8 @@ static void ipvlan_del_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_del_rcu(&addr->anode);
        ipvlan->ipv4cnt--;
        WARN_ON(ipvlan->ipv4cnt < 0);
-       if (!ipvlan->ipv4cnt)
-           ipvlan_set_broadcast_mac_filter(ipvlan, false);
+       if (!ipvlan->ipv4cnt && !ipvlan->dhcp4_seen)
+               ipvlan_set_broadcast_mac_filter(ipvlan, false);
        kfree_rcu(addr, rcu);
 
        return;
--

Quoted 3 lines

2.1.0

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Quoted 41 lines · Dan Williams

Quoted 40 lines · Mahesh Bandewar

Quoted 39 lines · Dan Williams

Quoted 27 lines · Mahesh Bandewar

Quoted 9 lines · Dan Williams

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) got called after the address was added, it would blow away the broadcast MAC address in mac_filters that was added at IPv4 address addition.

Next, ipvlan currently fails DHCP addressing for two reasons:

I would prefer DHCPv4 instead of DHCP since it could also mean DHCPv6 which does not use broadcast.

Quoted 14 lines

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient) which don't get checked against the address list.

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

Quoted 8 lines

Quoted 3 lines

To fix these issues, Watch for outgoing DHCP requests and enable the broadcast MAC address indefinitely when one is seen.

This approach will work but adds a performance drag for all UDP traffic whether the link needs DHCPv4 or not (especially when it does not need). Logic works well only when the link (always) needs DHCPv4. When the link does not care about DHCPv4 the packet-inspection always happens.

If DHCPv4 is detected on a link, doesn't that mean the link needs the broadcast filter enabled?

Quoted 8 lines

Quoted 3 lines

Yes and it should stay enabled as it's going to have IPv4. Also once broadcast bit is set there should not be any additional jugglery / packet inspection which hurts performance.

Yes, which is why my patch includes the check for dhcp4_seen and skips inspecting the packet. I could modify it to skip the L3 header check too in that case.

dhcp4_seen works correctly when there is dhcpv4 happening, but snooping continues if autoconf is not used.

Quoted 34 lines

Quoted 10 lines

Quoted 8 lines

If you start DHCPv4 on the link you obviously
expect it to work, unless there's no DHCPv4 server available. The patch should also reset the broadcast filter on close, so network management could simply start DHCPv4, watch it fail, close/open and set static IP.

Alternatively we could have the broadcast filter on a 2 minute timer that starts when DHCPv4 is seen.

Well, but this would be error-prone. I don't remember but DHCP timeout is not just 2 minutes.

2m is IIRC an RFC recommended timeout for initial DHCPv4 requests. If you don't get a reply to your requests within 2m, you aren't likely to get one ever on this network and you can stop trying for a while. You either get a reply in which case you get an IPv4 address and broadcast is always enabled, or you don't, in which case you don't really need broadcast. Then when userspace next tries DHCP, the timer would allow broadcast for another 2 minutes.

Quoted 10 lines

Quoted 10 lines

Quoted 3 lines

Do we really need to special case DHCPv4? Do you see problems in inverting the current logic of adding broadcast bit (i.e. from enable-if-IPv4 to disable-if-IPv6-only)?

The problem with this is dual-stack configuration. Typically both DHCPv4 and SLAAC are started in this case, and often SLAAC will complete earlier. So now the interface only has an IPv6 address but DHCPv4 is still ongoing; as I understand your proposal the filter would now block broadcast packets that DHCPv4 is listening for.

Quoted 4 lines

That was a proposal and we can tweak it if necessary. My primary concern is that the solution should not make us pay per packet penalty once (and even if not) the DHCPv4 handshake is complete, which is not the case as it stands now.

Quoted 6 lines

I'm not sure what you mean by "not make us pay a per packet penalty once DHCPv4 is complete". Once an IPv4 address is assigned, the broadcast filter must allow broadcast packets. Before an IPv4 address is assigned, the driver must watch for DHCPv4 and allow broadcast packets so that the DHCP reply isn't missed.

If the link is not using DHCPv4 to configure, the snooping continues and that is per packet cost the needs to be paid. Probably this can be avoided by setting dhcp4_seen = true in add_addr4 handler.

Quoted 9 lines

If DHCPv4 gets no response, then there are two options:

a) down the interface (which resets the broadcast filter to block broadcast packets) and re-up it, and don't do DHCPv4 again

b) have a timer in the driver that waits a period of time for an IPv4 address after a DHCPv4 request, and blocks broadcast when the timer expires

Probably something similar where turn on the broadcast bit and wait for the interface to get configured (2 min timer) and at the expiry decide what is to be done about braodcast bit. If the addresses configured are all IPv6, then eliminate it and if any of them are IPv4 then don't change it. In this case no special casing nor snooping is required and this should work for dual-stack scenario as well.

Quoted 162 lines

Dan

Quoted 158 lines

Quoted 154 lines

Dan

Quoted 150 lines

Quoted 143 lines

Signed-off-by Dan Williams <[email protected]>

---
NOTE: this patch supercedes my previous two ipvlan patches:
[PATCH 1/2] ipvlan: don't loose broadcast MAC when setting MAC filters [PATCH 2/2] ipvlan: always allow the broadcast MAC address

 drivers/net/ipvlan/ipvlan.h      |  2 ++
 drivers/net/ipvlan/ipvlan_core.c | 36 ++++++++++++++++++++++++++++++++++--
 drivers/net/ipvlan/ipvlan_main.c | 12 +++++++++---
 3 files changed, 45 insertions(+), 5 deletions(-)

drivers/net/ipvlan/ipvlan.h +2 -0

index 924ea98..7e0b8ff 100644
@@ -67,6 +67,7 @@ struct ipvl_dev {
        struct list_head        addrs;
        int                     ipv4cnt;
        int                     ipv6cnt;
+       bool                    dhcp4_seen;
        struct ipvl_pcpu_stats  __percpu *pcpu_stats;
        DECLARE_BITMAP(mac_filters, IPVLAN_MAC_FILTER_SIZE);
        netdev_features_t       sfeatures;

@@ -118,4 +119,5 @@ bool ipvlan_addr_busy(struct ipvl_dev *ipvlan, void *iaddr, bool is_v6);
 struct ipvl_addr *ipvlan_ht_addr_lookup(const struct ipvl_port *port,
                                        const void *iaddr, bool is_v6);
 void ipvlan_ht_addr_del(struct ipvl_addr *addr, bool sync);
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set);
 #endif /* __IPVLAN_H */

drivers/net/ipvlan/ipvlan_core.c +34 -2

index 2a17500..6dd992b 100644
@@ -126,6 +126,12 @@ static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type)
                lyr3h = arph;
                break;
        }
+       case htons(ETH_P_ALL): {
+               /* Raw sockets */
+               if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
+                       break;
+               /* Fall through */
+       }
        case htons(ETH_P_IP): {
                u32 pktlen;
                struct iphdr *ip4h;

@@ -454,16 +460,42 @@ out:
        return ipvlan_process_outbound(skb, ipvlan);
 }
 
+#define DHCP_PACKET_MIN_LEN 282
+
+static bool is_dhcp(struct sk_buff *skb)
+{
+       struct iphdr *ip4h = ip_hdr(skb);
+       struct udphdr *udph;
+
+       if (skb->len < DHCP_PACKET_MIN_LEN || ip4h->protocol != IPPROTO_UDP
+               || ip_is_fragment(ip4h))
+               return false;
+
+       /* In the case of RAW sockets the transport header is not set by
+        * the IP stack so we must set it ourselves.
+        */
+       if (skb->transport_header == skb->network_header)
+               skb_set_transport_header(skb, ETH_HLEN + sizeof(struct iphdr));
+       udph = udp_hdr(skb);
+       return udph && udph->dest == htons(67) && udph->source == htons(68);
+}
+
 static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 {
-       const struct ipvl_dev *ipvlan = netdev_priv(dev);
+       struct ipvl_dev *ipvlan = netdev_priv(dev);
        struct ethhdr *eth = eth_hdr(skb);
        struct ipvl_addr *addr;
        void *lyr3h;
        int addr_type;
 
+       lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+       if (!ipvlan->dhcp4_seen && lyr3h && addr_type == IPVL_IPV4
+           && is_dhcp(skb)) {
+               ipvlan->dhcp4_seen = true;
+               ipvlan_set_broadcast_mac_filter(ipvlan, true);
+       }
+
        if (ether_addr_equal(eth->h_dest, eth->h_source)) {
-               lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
                if (lyr3h) {
                        addr = ipvlan_addr_lookup(ipvlan->port, lyr3h, addr_type, true);
                        if (addr)

drivers/net/ipvlan/ipvlan_main.c +9 -4

index 4f4099d..a497fb9 100644
@@ -167,6 +167,8 @@ static int ipvlan_stop(struct net_device *dev)
 
        dev_uc_del(phy_dev, phy_dev->dev_addr);
 
+       ipvlan->dhcp4_seen = false;
+
        if (ipvlan->ipv6cnt > 0 || ipvlan->ipv4cnt > 0) {
                list_for_each_entry(addr, &ipvlan->addrs, anode)
                        ipvlan_ht_addr_del(addr, !dev->dismantle);

@@ -214,7 +216,7 @@ static void ipvlan_change_rx_flags(struct net_device *dev, int change)
                dev_set_allmulti(phy_dev, dev->flags & IFF_ALLMULTI? 1 : -1);
 }
 
-static void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
 {
        struct net_device *dev = ipvlan->dev;
        unsigned int hashbit = ipvlan_mac_hash(dev->broadcast);

@@ -239,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
                netdev_for_each_mc_addr(ha, dev)
                        __set_bit(ipvlan_mac_hash(ha->addr), mc_filters);
 
+               if (ipvlan->ipv4cnt || ipvlan->dhcp4_seen)
+                       __set_bit(ipvlan_mac_hash(dev->broadcast), mc_filters);
+
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
        }

@@ -467,6 +472,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
        INIT_LIST_HEAD(&ipvlan->addrs);
        ipvlan->ipv4cnt = 0;
        ipvlan->ipv6cnt = 0;
+       ipvlan->dhcp4_seen = false;
 
        /* TODO Probably put random address here to be presented to the
         * world but keep using the physical-dev address for the outgoing

@@ -708,8 +714,8 @@ static void ipvlan_del_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_del_rcu(&addr->anode);
        ipvlan->ipv4cnt--;
        WARN_ON(ipvlan->ipv4cnt < 0);
-       if (!ipvlan->ipv4cnt)
-           ipvlan_set_broadcast_mac_filter(ipvlan, false);
+       if (!ipvlan->ipv4cnt && !ipvlan->dhcp4_seen)
+               ipvlan_set_broadcast_mac_filter(ipvlan, false);
        kfree_rcu(addr, rcu);
 
        return;
--

Quoted 3 lines

2.1.0

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Quoted 106 lines · Mahesh Bandewar

Quoted 41 lines · Dan Williams

Quoted 40 lines · Mahesh Bandewar

Quoted 39 lines · Dan Williams

Quoted 27 lines · Mahesh Bandewar

Quoted 9 lines · Dan Williams

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) got called after the address was added, it would blow away the broadcast MAC address in mac_filters that was added at IPv4 address addition.

Next, ipvlan currently fails DHCP addressing for two reasons:

I would prefer DHCPv4 instead of DHCP since it could also mean DHCPv6 which does not use broadcast.

Quoted 14 lines

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient) which don't get checked against the address list.

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

Quoted 8 lines

Quoted 3 lines

To fix these issues, Watch for outgoing DHCP requests and enable the broadcast MAC address indefinitely when one is seen.

This approach will work but adds a performance drag for all UDP traffic whether the link needs DHCPv4 or not (especially when it does not need). Logic works well only when the link (always) needs DHCPv4. When the link does not care about DHCPv4 the packet-inspection always happens.

If DHCPv4 is detected on a link, doesn't that mean the link needs the broadcast filter enabled?

Quoted 8 lines

Quoted 3 lines

Yes and it should stay enabled as it's going to have IPv4. Also once broadcast bit is set there should not be any additional jugglery / packet inspection which hurts performance.

Yes, which is why my patch includes the check for dhcp4_seen and skips inspecting the packet. I could modify it to skip the L3 header check too in that case.

dhcp4_seen works correctly when there is dhcpv4 happening, but snooping continues if autoconf is not used.

Quoted 34 lines

Quoted 10 lines

Quoted 8 lines

If you start DHCPv4 on the link you obviously
expect it to work, unless there's no DHCPv4 server available. The patch should also reset the broadcast filter on close, so network management could simply start DHCPv4, watch it fail, close/open and set static IP.

Alternatively we could have the broadcast filter on a 2 minute timer that starts when DHCPv4 is seen.

Well, but this would be error-prone. I don't remember but DHCP timeout is not just 2 minutes.

2m is IIRC an RFC recommended timeout for initial DHCPv4 requests. If you don't get a reply to your requests within 2m, you aren't likely to get one ever on this network and you can stop trying for a while. You either get a reply in which case you get an IPv4 address and broadcast is always enabled, or you don't, in which case you don't really need broadcast. Then when userspace next tries DHCP, the timer would allow broadcast for another 2 minutes.

Quoted 10 lines

Quoted 10 lines

Quoted 3 lines

Do we really need to special case DHCPv4? Do you see problems in inverting the current logic of adding broadcast bit (i.e. from enable-if-IPv4 to disable-if-IPv6-only)?

The problem with this is dual-stack configuration. Typically both DHCPv4 and SLAAC are started in this case, and often SLAAC will complete earlier. So now the interface only has an IPv6 address but DHCPv4 is still ongoing; as I understand your proposal the filter would now block broadcast packets that DHCPv4 is listening for.

Quoted 4 lines

That was a proposal and we can tweak it if necessary. My primary concern is that the solution should not make us pay per packet penalty once (and even if not) the DHCPv4 handshake is complete, which is not the case as it stands now.

Quoted 6 lines

I'm not sure what you mean by "not make us pay a per packet penalty once DHCPv4 is complete". Once an IPv4 address is assigned, the broadcast filter must allow broadcast packets. Before an IPv4 address is assigned, the driver must watch for DHCPv4 and allow broadcast packets so that the DHCP reply isn't missed.

If the link is not using DHCPv4 to configure, the snooping continues and that is per packet cost the needs to be paid. Probably this can be avoided by setting dhcp4_seen = true in add_addr4 handler.

Quoted 9 lines

If DHCPv4 gets no response, then there are two options:

a) down the interface (which resets the broadcast filter to block broadcast packets) and re-up it, and don't do DHCPv4 again

b) have a timer in the driver that waits a period of time for an IPv4 address after a DHCPv4 request, and blocks broadcast when the timer expires

Quoted 6 lines

Probably something similar where turn on the broadcast bit and wait for the interface to get configured (2 min timer) and at the expiry decide what is to be done about braodcast bit. If the addresses configured are all IPv6, then eliminate it and if any of them are IPv4 then don't change it. In this case no special casing nor snooping is required and this should work for dual-stack scenario as well.

This does not work for the case where, after configuring, the DHCPv4 address lease expires and the IPv4 address is removed, and then DHCPv4 is started again. Possibly because the DHCP server was gone for a short time. The only way to handle that is to snoop again.

Reaching for maximum performance is great, but if that is done by ignoring/breaking a whole class of normal use-cases, I don't think that's reasonable. It's like saying "gee, I'd love UDP to be faster, so I'll remove anything TCP-related in the kernel".

Also, I don't think the snooping is as bad for performance as you may think. The only relevant issue here is L2 + IPv6-only,

and in that case
it's 4 extra compares (dhcp4_seen, ipv4cnt, lyr3h, and addr_type) for the external case. How much is that really going to slow things down, versus breaking a huge part of IPv4 address configuration?

Dan

Quoted 166 lines

Quoted 162 lines

Dan

Quoted 158 lines

Quoted 154 lines

Dan

Quoted 150 lines

Quoted 143 lines

Signed-off-by Dan Williams <[email protected]>

---
NOTE: this patch supercedes my previous two ipvlan patches:
[PATCH 1/2] ipvlan: don't loose broadcast MAC when setting MAC filters [PATCH 2/2] ipvlan: always allow the broadcast MAC address

 drivers/net/ipvlan/ipvlan.h      |  2 ++
 drivers/net/ipvlan/ipvlan_core.c | 36 ++++++++++++++++++++++++++++++++++--
 drivers/net/ipvlan/ipvlan_main.c | 12 +++++++++---
 3 files changed, 45 insertions(+), 5 deletions(-)

drivers/net/ipvlan/ipvlan.h +2 -0

index 924ea98..7e0b8ff 100644
@@ -67,6 +67,7 @@ struct ipvl_dev {
        struct list_head        addrs;
        int                     ipv4cnt;
        int                     ipv6cnt;
+       bool                    dhcp4_seen;
        struct ipvl_pcpu_stats  __percpu *pcpu_stats;
        DECLARE_BITMAP(mac_filters, IPVLAN_MAC_FILTER_SIZE);
        netdev_features_t       sfeatures;

@@ -118,4 +119,5 @@ bool ipvlan_addr_busy(struct ipvl_dev *ipvlan, void *iaddr, bool is_v6);
 struct ipvl_addr *ipvlan_ht_addr_lookup(const struct ipvl_port *port,
                                        const void *iaddr, bool is_v6);
 void ipvlan_ht_addr_del(struct ipvl_addr *addr, bool sync);
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set);
 #endif /* __IPVLAN_H */

drivers/net/ipvlan/ipvlan_core.c +34 -2

index 2a17500..6dd992b 100644
@@ -126,6 +126,12 @@ static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type)
                lyr3h = arph;
                break;
        }
+       case htons(ETH_P_ALL): {
+               /* Raw sockets */
+               if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
+                       break;
+               /* Fall through */
+       }
        case htons(ETH_P_IP): {
                u32 pktlen;
                struct iphdr *ip4h;

@@ -454,16 +460,42 @@ out:
        return ipvlan_process_outbound(skb, ipvlan);
 }
 
+#define DHCP_PACKET_MIN_LEN 282
+
+static bool is_dhcp(struct sk_buff *skb)
+{
+       struct iphdr *ip4h = ip_hdr(skb);
+       struct udphdr *udph;
+
+       if (skb->len < DHCP_PACKET_MIN_LEN || ip4h->protocol != IPPROTO_UDP
+               || ip_is_fragment(ip4h))
+               return false;
+
+       /* In the case of RAW sockets the transport header is not set by
+        * the IP stack so we must set it ourselves.
+        */
+       if (skb->transport_header == skb->network_header)
+               skb_set_transport_header(skb, ETH_HLEN + sizeof(struct iphdr));
+       udph = udp_hdr(skb);
+       return udph && udph->dest == htons(67) && udph->source == htons(68);
+}
+
 static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 {
-       const struct ipvl_dev *ipvlan = netdev_priv(dev);
+       struct ipvl_dev *ipvlan = netdev_priv(dev);
        struct ethhdr *eth = eth_hdr(skb);
        struct ipvl_addr *addr;
        void *lyr3h;
        int addr_type;
 
+       lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+       if (!ipvlan->dhcp4_seen && lyr3h && addr_type == IPVL_IPV4
+           && is_dhcp(skb)) {
+               ipvlan->dhcp4_seen = true;
+               ipvlan_set_broadcast_mac_filter(ipvlan, true);
+       }
+
        if (ether_addr_equal(eth->h_dest, eth->h_source)) {
-               lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
                if (lyr3h) {
                        addr = ipvlan_addr_lookup(ipvlan->port, lyr3h, addr_type, true);
                        if (addr)

drivers/net/ipvlan/ipvlan_main.c +9 -4

index 4f4099d..a497fb9 100644
@@ -167,6 +167,8 @@ static int ipvlan_stop(struct net_device *dev)
 
        dev_uc_del(phy_dev, phy_dev->dev_addr);
 
+       ipvlan->dhcp4_seen = false;
+
        if (ipvlan->ipv6cnt > 0 || ipvlan->ipv4cnt > 0) {
                list_for_each_entry(addr, &ipvlan->addrs, anode)
                        ipvlan_ht_addr_del(addr, !dev->dismantle);

@@ -214,7 +216,7 @@ static void ipvlan_change_rx_flags(struct net_device *dev, int change)
                dev_set_allmulti(phy_dev, dev->flags & IFF_ALLMULTI? 1 : -1);
 }
 
-static void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
 {
        struct net_device *dev = ipvlan->dev;
        unsigned int hashbit = ipvlan_mac_hash(dev->broadcast);

@@ -239,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
                netdev_for_each_mc_addr(ha, dev)
                        __set_bit(ipvlan_mac_hash(ha->addr), mc_filters);
 
+               if (ipvlan->ipv4cnt || ipvlan->dhcp4_seen)
+                       __set_bit(ipvlan_mac_hash(dev->broadcast), mc_filters);
+
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
        }

@@ -467,6 +472,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
        INIT_LIST_HEAD(&ipvlan->addrs);
        ipvlan->ipv4cnt = 0;
        ipvlan->ipv6cnt = 0;
+       ipvlan->dhcp4_seen = false;
 
        /* TODO Probably put random address here to be presented to the
         * world but keep using the physical-dev address for the outgoing

@@ -708,8 +714,8 @@ static void ipvlan_del_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_del_rcu(&addr->anode);
        ipvlan->ipv4cnt--;
        WARN_ON(ipvlan->ipv4cnt < 0);
-       if (!ipvlan->ipv4cnt)
-           ipvlan_set_broadcast_mac_filter(ipvlan, false);
+       if (!ipvlan->ipv4cnt && !ipvlan->dhcp4_seen)
+               ipvlan_set_broadcast_mac_filter(ipvlan, false);
        kfree_rcu(addr, rcu);
 
        return;
--

Quoted 3 lines

2.1.0

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Quoted 114 lines · Dan Williams

Quoted 112 lines · Mahesh Bandewar

Quoted 41 lines · Dan Williams

Quoted 40 lines · Mahesh Bandewar

Quoted 39 lines · Dan Williams

Quoted 27 lines · Mahesh Bandewar

Quoted 9 lines · Dan Williams

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) got called after the address was added, it would blow away the broadcast MAC address in mac_filters that was added at IPv4 address addition.

Next, ipvlan currently fails DHCP addressing for two reasons:

I would prefer DHCPv4 instead of DHCP since it could also mean DHCPv6 which does not use broadcast.

Quoted 14 lines

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient) which don't get checked against the address list.

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

Quoted 8 lines

Quoted 3 lines

To fix these issues, Watch for outgoing DHCP requests and enable the broadcast MAC address indefinitely when one is seen.

This approach will work but adds a performance drag for all UDP traffic whether the link needs DHCPv4 or not (especially when it does not need). Logic works well only when the link (always) needs DHCPv4. When the link does not care about DHCPv4 the packet-inspection always happens.

If DHCPv4 is detected on a link, doesn't that mean the link needs the broadcast filter enabled?

Quoted 8 lines

Quoted 3 lines

Yes and it should stay enabled as it's going to have IPv4. Also once broadcast bit is set there should not be any additional jugglery / packet inspection which hurts performance.

Yes, which is why my patch includes the check for dhcp4_seen and skips inspecting the packet. I could modify it to skip the L3 header check too in that case.

dhcp4_seen works correctly when there is dhcpv4 happening, but snooping continues if autoconf is not used.

Quoted 34 lines

Quoted 10 lines

Quoted 8 lines

If you start DHCPv4 on the link you obviously
expect it to work, unless there's no DHCPv4 server available. The patch should also reset the broadcast filter on close, so network management could simply start DHCPv4, watch it fail, close/open and set static IP.

Alternatively we could have the broadcast filter on a 2 minute timer that starts when DHCPv4 is seen.

Well, but this would be error-prone. I don't remember but DHCP timeout is not just 2 minutes.

2m is IIRC an RFC recommended timeout for initial DHCPv4 requests. If you don't get a reply to your requests within 2m, you aren't likely to get one ever on this network and you can stop trying for a while. You either get a reply in which case you get an IPv4 address and broadcast is always enabled, or you don't, in which case you don't really need broadcast. Then when userspace next tries DHCP, the timer would allow broadcast for another 2 minutes.

Quoted 10 lines

Quoted 10 lines

Quoted 3 lines

Do we really need to special case DHCPv4? Do you see problems in inverting the current logic of adding broadcast bit (i.e. from enable-if-IPv4 to disable-if-IPv6-only)?

The problem with this is dual-stack configuration. Typically both DHCPv4 and SLAAC are started in this case, and often SLAAC will complete earlier. So now the interface only has an IPv6 address but DHCPv4 is still ongoing; as I understand your proposal the filter would now block broadcast packets that DHCPv4 is listening for.

Quoted 4 lines

That was a proposal and we can tweak it if necessary. My primary concern is that the solution should not make us pay per packet penalty once (and even if not) the DHCPv4 handshake is complete, which is not the case as it stands now.

Quoted 6 lines

I'm not sure what you mean by "not make us pay a per packet penalty once DHCPv4 is complete". Once an IPv4 address is assigned, the broadcast filter must allow broadcast packets. Before an IPv4 address is assigned, the driver must watch for DHCPv4 and allow broadcast packets so that the DHCP reply isn't missed.

If the link is not using DHCPv4 to configure, the snooping continues and that is per packet cost the needs to be paid. Probably this can be avoided by setting dhcp4_seen = true in add_addr4 handler.

Quoted 9 lines

If DHCPv4 gets no response, then there are two options:

a) down the interface (which resets the broadcast filter to block broadcast packets) and re-up it, and don't do DHCPv4 again

b) have a timer in the driver that waits a period of time for an IPv4 address after a DHCPv4 request, and blocks broadcast when the timer expires

Probably something similar where turn on the broadcast bit and wait for the interface to get configured (2 min timer) and at the expiry decide what is to be done about braodcast bit. If the addresses configured are all IPv6, then eliminate it and if any of them are IPv4 then don't change it. In this case no special casing nor snooping is required and this should work for dual-stack scenario as well.

Quoted 5 lines

This does not work for the case where, after configuring, the DHCPv4 address lease expires and the IPv4 address is removed, and then DHCPv4 is started again. Possibly because the DHCP server was gone for a short time. The only way to handle that is to snoop again.

If the DHCPv4 lease is expired, then why DHCPv4-renew wont work (also it's unicast)? Also if the address applied is IPv4 then the broadcast bit will stay. In this case I don't understand why this wont work.

If the link is stripped off of address(es), then it should again go back into the config-mode where it would turn on the broadcast bit and enable timer to get it configured. May be I'm missing something.

Quoted 5 lines

Reaching for maximum performance is great, but if that is done by ignoring/breaking a whole class of normal use-cases, I don't think that's reasonable. It's like saying "gee, I'd love UDP to be faster, so I'll remove anything TCP-related in the kernel".

What is the amount of traffic that a link will be sending for config (DHCPv4 in this case)? I would guarantee you that it's so negligible to the extent that it's would be non-existent. But all the suggestions include snooping of every packet that goes through the link. However I'm not suggesting that this is non-important or can stay broken. But would rather have a solution that would not affect 99.9% of the traffic (per packet penalty that I mentioned earlier).

Quoted 2 lines

Also, I don't think the snooping is as bad for performance as you may think. The only relevant issue here is L2 + IPv6-only,

Also IPv4 case when the link is not using autoconf.

Quoted 5 lines

and in that case
it's 4 extra compares (dhcp4_seen, ipv4cnt, lyr3h, and addr_type) for the external case. How much is that really going to slow things down, versus breaking a huge part of IPv4 address configuration?

Quoted 170 lines

Dan

Quoted 166 lines

Quoted 162 lines

Dan

Quoted 158 lines

Quoted 154 lines

Dan

Quoted 150 lines

Quoted 143 lines

Signed-off-by Dan Williams <[email protected]>

---
NOTE: this patch supercedes my previous two ipvlan patches:
[PATCH 1/2] ipvlan: don't loose broadcast MAC when setting MAC filters [PATCH 2/2] ipvlan: always allow the broadcast MAC address

 drivers/net/ipvlan/ipvlan.h      |  2 ++
 drivers/net/ipvlan/ipvlan_core.c | 36 ++++++++++++++++++++++++++++++++++--
 drivers/net/ipvlan/ipvlan_main.c | 12 +++++++++---
 3 files changed, 45 insertions(+), 5 deletions(-)

drivers/net/ipvlan/ipvlan.h +2 -0

index 924ea98..7e0b8ff 100644
@@ -67,6 +67,7 @@ struct ipvl_dev {
        struct list_head        addrs;
        int                     ipv4cnt;
        int                     ipv6cnt;
+       bool                    dhcp4_seen;
        struct ipvl_pcpu_stats  __percpu *pcpu_stats;
        DECLARE_BITMAP(mac_filters, IPVLAN_MAC_FILTER_SIZE);
        netdev_features_t       sfeatures;

@@ -118,4 +119,5 @@ bool ipvlan_addr_busy(struct ipvl_dev *ipvlan, void *iaddr, bool is_v6);
 struct ipvl_addr *ipvlan_ht_addr_lookup(const struct ipvl_port *port,
                                        const void *iaddr, bool is_v6);
 void ipvlan_ht_addr_del(struct ipvl_addr *addr, bool sync);
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set);
 #endif /* __IPVLAN_H */

drivers/net/ipvlan/ipvlan_core.c +34 -2

index 2a17500..6dd992b 100644
@@ -126,6 +126,12 @@ static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type)
                lyr3h = arph;
                break;
        }
+       case htons(ETH_P_ALL): {
+               /* Raw sockets */
+               if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
+                       break;
+               /* Fall through */
+       }
        case htons(ETH_P_IP): {
                u32 pktlen;
                struct iphdr *ip4h;

@@ -454,16 +460,42 @@ out:
        return ipvlan_process_outbound(skb, ipvlan);
 }
 
+#define DHCP_PACKET_MIN_LEN 282
+
+static bool is_dhcp(struct sk_buff *skb)
+{
+       struct iphdr *ip4h = ip_hdr(skb);
+       struct udphdr *udph;
+
+       if (skb->len < DHCP_PACKET_MIN_LEN || ip4h->protocol != IPPROTO_UDP
+               || ip_is_fragment(ip4h))
+               return false;
+
+       /* In the case of RAW sockets the transport header is not set by
+        * the IP stack so we must set it ourselves.
+        */
+       if (skb->transport_header == skb->network_header)
+               skb_set_transport_header(skb, ETH_HLEN + sizeof(struct iphdr));
+       udph = udp_hdr(skb);
+       return udph && udph->dest == htons(67) && udph->source == htons(68);
+}
+
 static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 {
-       const struct ipvl_dev *ipvlan = netdev_priv(dev);
+       struct ipvl_dev *ipvlan = netdev_priv(dev);
        struct ethhdr *eth = eth_hdr(skb);
        struct ipvl_addr *addr;
        void *lyr3h;
        int addr_type;
 
+       lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+       if (!ipvlan->dhcp4_seen && lyr3h && addr_type == IPVL_IPV4
+           && is_dhcp(skb)) {
+               ipvlan->dhcp4_seen = true;
+               ipvlan_set_broadcast_mac_filter(ipvlan, true);
+       }
+
        if (ether_addr_equal(eth->h_dest, eth->h_source)) {
-               lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
                if (lyr3h) {
                        addr = ipvlan_addr_lookup(ipvlan->port, lyr3h, addr_type, true);
                        if (addr)

drivers/net/ipvlan/ipvlan_main.c +9 -4

index 4f4099d..a497fb9 100644
@@ -167,6 +167,8 @@ static int ipvlan_stop(struct net_device *dev)
 
        dev_uc_del(phy_dev, phy_dev->dev_addr);
 
+       ipvlan->dhcp4_seen = false;
+
        if (ipvlan->ipv6cnt > 0 || ipvlan->ipv4cnt > 0) {
                list_for_each_entry(addr, &ipvlan->addrs, anode)
                        ipvlan_ht_addr_del(addr, !dev->dismantle);

@@ -214,7 +216,7 @@ static void ipvlan_change_rx_flags(struct net_device *dev, int change)
                dev_set_allmulti(phy_dev, dev->flags & IFF_ALLMULTI? 1 : -1);
 }
 
-static void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
 {
        struct net_device *dev = ipvlan->dev;
        unsigned int hashbit = ipvlan_mac_hash(dev->broadcast);

@@ -239,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
                netdev_for_each_mc_addr(ha, dev)
                        __set_bit(ipvlan_mac_hash(ha->addr), mc_filters);
 
+               if (ipvlan->ipv4cnt || ipvlan->dhcp4_seen)
+                       __set_bit(ipvlan_mac_hash(dev->broadcast), mc_filters);
+
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
        }

@@ -467,6 +472,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
        INIT_LIST_HEAD(&ipvlan->addrs);
        ipvlan->ipv4cnt = 0;
        ipvlan->ipv6cnt = 0;
+       ipvlan->dhcp4_seen = false;
 
        /* TODO Probably put random address here to be presented to the
         * world but keep using the physical-dev address for the outgoing

@@ -708,8 +714,8 @@ static void ipvlan_del_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_del_rcu(&addr->anode);
        ipvlan->ipv4cnt--;
        WARN_ON(ipvlan->ipv4cnt < 0);
-       if (!ipvlan->ipv4cnt)
-           ipvlan_set_broadcast_mac_filter(ipvlan, false);
+       if (!ipvlan->ipv4cnt && !ipvlan->dhcp4_seen)
+               ipvlan_set_broadcast_mac_filter(ipvlan, false);
        kfree_rcu(addr, rcu);
 
        return;
--

Quoted 3 lines

2.1.0

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Quoted 6 lines

Probably something similar where turn on the broadcast bit and wait for the interface to get configured (2 min timer) and at the expiry decide what is to be done about braodcast bit. If the addresses configured are all IPv6, then eliminate it and if any of them are IPv4 then don't change it. In this case no special casing nor snooping is required and this should work for dual-stack scenario as well.

This does not work for the case where, after configuring, the DHCPv4 address lease expires and the IPv4 address is removed, and then DHCPv4 is started again. Possibly because the DHCP server was gone for a short time. The only way to handle that is to snoop again.

Reaching for maximum performance is great, but if that is done by ignoring/breaking a whole class of normal use-cases, I don't think that's reasonable. It's like saying "gee, I'd love UDP to be faster, so I'll remove anything TCP-related in the kernel".

Also, I don't think the snooping is as bad for performance as you may think. The only relevant issue here is L2 + IPv6-only, and in that case it's 4 extra compares (dhcp4_seen, ipv4cnt, lyr3h, and addr_type) for the external case. How much is that really going to slow things down, versus breaking a huge part of IPv4 address configuration?

From: Dan Williams
...

Quoted 17 lines

Quoted 6 lines

Probably something similar where turn on the broadcast bit and wait for the interface to get configured (2 min timer) and at the expiry decide what is to be done about braodcast bit. If the addresses configured are all IPv6, then eliminate it and if any of them are IPv4 then don't change it. In this case no special casing nor snooping is required and this should work for dual-stack scenario as well.

This does not work for the case where, after configuring, the DHCPv4 address lease expires and the IPv4 address is removed, and then DHCPv4 is started again. Possibly because the DHCP server was gone for a short time. The only way to handle that is to snoop again.

Reaching for maximum performance is great, but if that is done by ignoring/breaking a whole class of normal use-cases, I don't think that's reasonable. It's like saying "gee, I'd love UDP to be faster, so I'll remove anything TCP-related in the kernel".

Quoted 5 lines

Also, I don't think the snooping is as bad for performance as you may think. The only relevant issue here is L2 + IPv6-only, and in that case it's 4 extra compares (dhcp4_seen, ipv4cnt, lyr3h, and addr_type) for the external case. How much is that really going to slow things down, versus breaking a huge part of IPv4 address configuration?

How much performance do you really gain from disabling broadcasts in hardware? (Unless your network has massive broadcast storms - which are a different problem). I can imagine it helping a low power device stay idle.

For DHCP you have bigger issues.
All the versions of the dhcp client I've seen use the bpf interface for receive traffic (even once started) so you get the cost of a clone of every received packet.

David

NrybXǧv^)޺{.n+z^)w*jgݢj/zޖ2ޙ&)ߡaGhj:+vw٥

From: Dan Williams
...

Quoted 17 lines

Quoted 6 lines

Probably something similar where turn on the broadcast bit and wait for the interface to get configured (2 min timer) and at the expiry decide what is to be done about braodcast bit. If the addresses configured are all IPv6, then eliminate it and if any of them are IPv4 then don't change it. In this case no special casing nor snooping is required and this should work for dual-stack scenario as well.

This does not work for the case where, after configuring, the DHCPv4 address lease expires and the IPv4 address is removed, and then DHCPv4 is started again. Possibly because the DHCP server was gone for a short time. The only way to handle that is to snoop again.

Reaching for maximum performance is great, but if that is done by ignoring/breaking a whole class of normal use-cases, I don't think that's reasonable. It's like saying "gee, I'd love UDP to be faster, so I'll remove anything TCP-related in the kernel".

Quoted 5 lines

Also, I don't think the snooping is as bad for performance as you may think. The only relevant issue here is L2 + IPv6-only, and in that case it's 4 extra compares (dhcp4_seen, ipv4cnt, lyr3h, and addr_type) for the external case. How much is that really going to slow things down, versus breaking a huge part of IPv4 address configuration?

How much performance do you really gain from disabling broadcasts in hardware? (Unless your network has massive broadcast storms - which are a different problem). I can imagine it helping a low power device stay idle.

For DHCP you have bigger issues.
All the versions of the dhcp client I've seen use the bpf interface for receive traffic (even once started) so you get the cost of a clone of every received packet.

David

Quoted 115 lines · Mahesh Bandewar

Quoted 114 lines · Dan Williams

Quoted 112 lines · Mahesh Bandewar

Quoted 41 lines · Dan Williams

Quoted 40 lines · Mahesh Bandewar

Quoted 39 lines · Dan Williams

Quoted 27 lines · Mahesh Bandewar

Quoted 9 lines · Dan Williams

The broadcast MAC is supposed to be allowed whenever the device has an IPv4 address, otherwise ARP requests get dropped on the floor. If ndo_set_rx_mode (and thus ipvlan_set_multicast_mac_filter()) got called after the address was added, it would blow away the broadcast MAC address in mac_filters that was added at IPv4 address addition.

Next, ipvlan currently fails DHCP addressing for two reasons:

I would prefer DHCPv4 instead of DHCP since it could also mean DHCPv6 which does not use broadcast.

Quoted 14 lines

1) DHCP offers are typically unicast back to the device's MAC address, and at the IP layer have a destination IP address matching the new lease address. In ipvlan unicast packets are checked against existing addresses assigned to the ipvlan interface, so clearly this fails hard because the ipvlan interface has no IP addresses yet. Workaround: request that the server broadcast replies (-B for dhclient) which don't get checked against the address list.

2) Even when that's done, mac_filters only allows the broadcast MAC address when the interface has >= 1 IPv4 addresses, so double-fail, and the incoming DHCP offer gets dropped on the floor again.

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To fix these issues, Watch for outgoing DHCP requests and enable the broadcast MAC address indefinitely when one is seen.

This approach will work but adds a performance drag for all UDP traffic whether the link needs DHCPv4 or not (especially when it does not need). Logic works well only when the link (always) needs DHCPv4. When the link does not care about DHCPv4 the packet-inspection always happens.

If DHCPv4 is detected on a link, doesn't that mean the link needs the broadcast filter enabled?

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Yes and it should stay enabled as it's going to have IPv4. Also once broadcast bit is set there should not be any additional jugglery / packet inspection which hurts performance.

Yes, which is why my patch includes the check for dhcp4_seen and skips inspecting the packet. I could modify it to skip the L3 header check too in that case.

dhcp4_seen works correctly when there is dhcpv4 happening, but snooping continues if autoconf is not used.

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If you start DHCPv4 on the link you obviously
expect it to work, unless there's no DHCPv4 server available. The patch should also reset the broadcast filter on close, so network management could simply start DHCPv4, watch it fail, close/open and set static IP.

Alternatively we could have the broadcast filter on a 2 minute timer that starts when DHCPv4 is seen.

Well, but this would be error-prone. I don't remember but DHCP timeout is not just 2 minutes.

2m is IIRC an RFC recommended timeout for initial DHCPv4 requests. If you don't get a reply to your requests within 2m, you aren't likely to get one ever on this network and you can stop trying for a while. You either get a reply in which case you get an IPv4 address and broadcast is always enabled, or you don't, in which case you don't really need broadcast. Then when userspace next tries DHCP, the timer would allow broadcast for another 2 minutes.

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Do we really need to special case DHCPv4? Do you see problems in inverting the current logic of adding broadcast bit (i.e. from enable-if-IPv4 to disable-if-IPv6-only)?

The problem with this is dual-stack configuration. Typically both DHCPv4 and SLAAC are started in this case, and often SLAAC will complete earlier. So now the interface only has an IPv6 address but DHCPv4 is still ongoing; as I understand your proposal the filter would now block broadcast packets that DHCPv4 is listening for.

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That was a proposal and we can tweak it if necessary. My primary concern is that the solution should not make us pay per packet penalty once (and even if not) the DHCPv4 handshake is complete, which is not the case as it stands now.

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I'm not sure what you mean by "not make us pay a per packet penalty once DHCPv4 is complete". Once an IPv4 address is assigned, the broadcast filter must allow broadcast packets. Before an IPv4 address is assigned, the driver must watch for DHCPv4 and allow broadcast packets so that the DHCP reply isn't missed.

If the link is not using DHCPv4 to configure, the snooping continues and that is per packet cost the needs to be paid. Probably this can be avoided by setting dhcp4_seen = true in add_addr4 handler.

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If DHCPv4 gets no response, then there are two options:

a) down the interface (which resets the broadcast filter to block broadcast packets) and re-up it, and don't do DHCPv4 again

b) have a timer in the driver that waits a period of time for an IPv4 address after a DHCPv4 request, and blocks broadcast when the timer expires

Probably something similar where turn on the broadcast bit and wait for the interface to get configured (2 min timer) and at the expiry decide what is to be done about braodcast bit. If the addresses configured are all IPv6, then eliminate it and if any of them are IPv4 then don't change it. In this case no special casing nor snooping is required and this should work for dual-stack scenario as well.

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This does not work for the case where, after configuring, the DHCPv4 address lease expires and the IPv4 address is removed, and then DHCPv4 is started again. Possibly because the DHCP server was gone for a short time. The only way to handle that is to snoop again.

If the DHCPv4 lease is expired, then why DHCPv4-renew wont work (also it's unicast)? Also if the address applied is IPv4 then the broadcast bit will stay. In this case I don't understand why this wont work.

You're right. I mis-read your proposal above.

But having re-read it, are you proposing a 2m timer on interface up? If so (and ignore this if not) I don't think that works well either, because there's no guarantee that interface configuration will happen only close to interface up. Maybe userspace adds IPv6 addresses initially, and then later tries to do DHCP for some reason. We simply cannot rely on specific ordering of operations that userspace might want to do.

If you don't mean a 2m timer from interface up, then ignore that, and then what kind of time do you mean? :)

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If the link is stripped off of address(es), then it should again go back into the config-mode where it would turn on the broadcast bit and enable timer to get it configured. May be I'm missing something.

As above, I was wrong about the DHCPv4 lease expiration thing, but this may still run afoul of userspace operation ordering if you are talking about a 2m timer from interface up.

Just had another thought though; what if instead of snooping for all the DHCP stuff, the code just snooped outgoing IPv4 packets for a broadcast destination address? Then turn on the broadcast bit filter for 2m. That would look something like this:

static bool is_bcast4(struct sk_buff *skb)

{
	struct iphdr *ip4h;

	switch (skb->protocol) {
	case htons(ETH_P_ALL):
		/* Raw sockets */
		if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
			break;
		/* Fall through */
	case htons(ETH_P_IP):
		if (unlikely(!pskb_may_pull(skb, sizeof(*ip4h))))
			return NULL;
		ip4h = ip_hdr(skb);
		if (ip4h->ihl < 5 || ip4h->version != 4)
			return NULL;
		return ip4h->daddr == INADDR_BROADCAST;
	}
	return false;
}

static int ipvlan_xmit_mode_l2(...)

{
	if (!ipvlan->ipv4cnt && !ipvlan->bcast4_seen && is_bcast4(skb)) {
		ipvlan->bcast4_seen = true;
		ipvlan_set_broadcast_mac_filter(ipvlan, true);
	}

Yes, it's still snooping for all packets, but it's a lot fewer compares than looking for DHCP specifically.

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Reaching for maximum performance is great, but if that is done by ignoring/breaking a whole class of normal use-cases, I don't think that's reasonable. It's like saying "gee, I'd love UDP to be faster, so I'll remove anything TCP-related in the kernel".

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What is the amount of traffic that a link will be sending for config (DHCPv4 in this case)? I would guarantee you that it's so negligible to the extent that it's would be non-existent. But all the suggestions include snooping of every packet that goes through the link. However I'm not suggesting that this is non-important or can stay broken. But would rather have a solution that would not affect 99.9% of the traffic (per packet penalty that I mentioned earlier).

I agree, and it's great that we're brainstorming solutions. Unfortunately as a kernel driver, it cannot rely on specific ordering or timing of address addition/deletion since that's not something you can predict at all.

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Also, I don't think the snooping is as bad for performance as you may think. The only relevant issue here is L2 + IPv6-only,

Also IPv4 case when the link is not using autoconf.

Yes, that's true. But a kernel driver simply doesn't know what its setup will be so it cannot assume much of anything about the addressing setup despite whatever performance gains there might be...

Dan

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and in that case
it's 4 extra compares (dhcp4_seen, ipv4cnt, lyr3h, and addr_type) for the external case. How much is that really going to slow things down, versus breaking a huge part of IPv4 address configuration?

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Dan

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Dan

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Signed-off-by Dan Williams <[email protected]>

---
NOTE: this patch supercedes my previous two ipvlan patches:
[PATCH 1/2] ipvlan: don't loose broadcast MAC when setting MAC filters [PATCH 2/2] ipvlan: always allow the broadcast MAC address

 drivers/net/ipvlan/ipvlan.h      |  2 ++
 drivers/net/ipvlan/ipvlan_core.c | 36 ++++++++++++++++++++++++++++++++++--
 drivers/net/ipvlan/ipvlan_main.c | 12 +++++++++---
 3 files changed, 45 insertions(+), 5 deletions(-)

drivers/net/ipvlan/ipvlan.h +2 -0

index 924ea98..7e0b8ff 100644
@@ -67,6 +67,7 @@ struct ipvl_dev {
        struct list_head        addrs;
        int                     ipv4cnt;
        int                     ipv6cnt;
+       bool                    dhcp4_seen;
        struct ipvl_pcpu_stats  __percpu *pcpu_stats;
        DECLARE_BITMAP(mac_filters, IPVLAN_MAC_FILTER_SIZE);
        netdev_features_t       sfeatures;

@@ -118,4 +119,5 @@ bool ipvlan_addr_busy(struct ipvl_dev *ipvlan, void *iaddr, bool is_v6);
 struct ipvl_addr *ipvlan_ht_addr_lookup(const struct ipvl_port *port,
                                        const void *iaddr, bool is_v6);
 void ipvlan_ht_addr_del(struct ipvl_addr *addr, bool sync);
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set);
 #endif /* __IPVLAN_H */

drivers/net/ipvlan/ipvlan_core.c +34 -2

index 2a17500..6dd992b 100644
@@ -126,6 +126,12 @@ static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type)
                lyr3h = arph;
                break;
        }
+       case htons(ETH_P_ALL): {
+               /* Raw sockets */
+               if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
+                       break;
+               /* Fall through */
+       }
        case htons(ETH_P_IP): {
                u32 pktlen;
                struct iphdr *ip4h;

@@ -454,16 +460,42 @@ out:
        return ipvlan_process_outbound(skb, ipvlan);
 }
 
+#define DHCP_PACKET_MIN_LEN 282
+
+static bool is_dhcp(struct sk_buff *skb)
+{
+       struct iphdr *ip4h = ip_hdr(skb);
+       struct udphdr *udph;
+
+       if (skb->len < DHCP_PACKET_MIN_LEN || ip4h->protocol != IPPROTO_UDP
+               || ip_is_fragment(ip4h))
+               return false;
+
+       /* In the case of RAW sockets the transport header is not set by
+        * the IP stack so we must set it ourselves.
+        */
+       if (skb->transport_header == skb->network_header)
+               skb_set_transport_header(skb, ETH_HLEN + sizeof(struct iphdr));
+       udph = udp_hdr(skb);
+       return udph && udph->dest == htons(67) && udph->source == htons(68);
+}
+
 static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 {
-       const struct ipvl_dev *ipvlan = netdev_priv(dev);
+       struct ipvl_dev *ipvlan = netdev_priv(dev);
        struct ethhdr *eth = eth_hdr(skb);
        struct ipvl_addr *addr;
        void *lyr3h;
        int addr_type;
 
+       lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+       if (!ipvlan->dhcp4_seen && lyr3h && addr_type == IPVL_IPV4
+           && is_dhcp(skb)) {
+               ipvlan->dhcp4_seen = true;
+               ipvlan_set_broadcast_mac_filter(ipvlan, true);
+       }
+
        if (ether_addr_equal(eth->h_dest, eth->h_source)) {
-               lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
                if (lyr3h) {
                        addr = ipvlan_addr_lookup(ipvlan->port, lyr3h, addr_type, true);
                        if (addr)

drivers/net/ipvlan/ipvlan_main.c +9 -4

index 4f4099d..a497fb9 100644
@@ -167,6 +167,8 @@ static int ipvlan_stop(struct net_device *dev)
 
        dev_uc_del(phy_dev, phy_dev->dev_addr);
 
+       ipvlan->dhcp4_seen = false;
+
        if (ipvlan->ipv6cnt > 0 || ipvlan->ipv4cnt > 0) {
                list_for_each_entry(addr, &ipvlan->addrs, anode)
                        ipvlan_ht_addr_del(addr, !dev->dismantle);

@@ -214,7 +216,7 @@ static void ipvlan_change_rx_flags(struct net_device *dev, int change)
                dev_set_allmulti(phy_dev, dev->flags & IFF_ALLMULTI? 1 : -1);
 }
 
-static void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
+void ipvlan_set_broadcast_mac_filter(struct ipvl_dev *ipvlan, bool set)
 {
        struct net_device *dev = ipvlan->dev;
        unsigned int hashbit = ipvlan_mac_hash(dev->broadcast);

@@ -239,6 +241,9 @@ static void ipvlan_set_multicast_mac_filter(struct net_device *dev)
                netdev_for_each_mc_addr(ha, dev)
                        __set_bit(ipvlan_mac_hash(ha->addr), mc_filters);
 
+               if (ipvlan->ipv4cnt || ipvlan->dhcp4_seen)
+                       __set_bit(ipvlan_mac_hash(dev->broadcast), mc_filters);
+
                bitmap_copy(ipvlan->mac_filters, mc_filters,
                            IPVLAN_MAC_FILTER_SIZE);
        }

@@ -467,6 +472,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
        INIT_LIST_HEAD(&ipvlan->addrs);
        ipvlan->ipv4cnt = 0;
        ipvlan->ipv6cnt = 0;
+       ipvlan->dhcp4_seen = false;
 
        /* TODO Probably put random address here to be presented to the
         * world but keep using the physical-dev address for the outgoing

@@ -708,8 +714,8 @@ static void ipvlan_del_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
        list_del_rcu(&addr->anode);
        ipvlan->ipv4cnt--;
        WARN_ON(ipvlan->ipv4cnt < 0);
-       if (!ipvlan->ipv4cnt)
-           ipvlan_set_broadcast_mac_filter(ipvlan, false);
+       if (!ipvlan->ipv4cnt && !ipvlan->dhcp4_seen)
+               ipvlan_set_broadcast_mac_filter(ipvlan, false);
        kfree_rcu(addr, rcu);
 
        return;
--

Quoted 3 lines

2.1.0

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Quoted 4 lines

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Any thoughts on this Mahesh? Is this non-DHCP approach more to your liking? If so I'll generate an actual patch and do some testing.

Quoted 54 lines

You're right. I mis-read your proposal above.

But having re-read it, are you proposing a 2m timer on interface up? If so (and ignore this if not) I don't think that works well either, because there's no guarantee that interface configuration will happen only close to interface up. Maybe userspace adds IPv6 addresses initially, and then later tries to do DHCP for some reason. We simply cannot rely on specific ordering of operations that userspace might want to do.

If you don't mean a 2m timer from interface up, then ignore that, and then what kind of time do you mean? :)

Quoted 3 lines

If the link is stripped off of address(es), then it should again go back into the config-mode where it would turn on the broadcast bit and enable timer to get it configured. May be I'm missing something.

As above, I was wrong about the DHCPv4 lease expiration thing, but this may still run afoul of userspace operation ordering if you are talking about a 2m timer from interface up.

Just had another thought though; what if instead of snooping for all the DHCP stuff, the code just snooped outgoing IPv4 packets for a broadcast destination address? Then turn on the broadcast bit filter for 2m. That would look something like this:

static bool is_bcast4(struct sk_buff *skb)

{
      struct iphdr *ip4h;

      switch (skb->protocol) {
      case htons(ETH_P_ALL):
              /* Raw sockets */
              if (eth_hdr(skb)->h_proto != htons(ETH_P_IP))
                      break;
              /* Fall through */
      case htons(ETH_P_IP):
              if (unlikely(!pskb_may_pull(skb, sizeof(*ip4h))))
                      return NULL;
              ip4h = ip_hdr(skb);
              if (ip4h->ihl < 5 || ip4h->version != 4)
                      return NULL;
              return ip4h->daddr == INADDR_BROADCAST;
      }
      return false;
}

static int ipvlan_xmit_mode_l2(...)

{
      if (!ipvlan->ipv4cnt && !ipvlan->bcast4_seen && is_bcast4(skb)) {
              ipvlan->bcast4_seen = true;
              ipvlan_set_broadcast_mac_filter(ipvlan, true);
      }

Quoted 2 lines

Yes, it's still snooping for all packets, but it's a lot fewer compares than looking for DHCP specifically.

Any thoughts on this Mahesh? Is this non-DHCP approach more to your liking? If so I'll generate an actual patch and do some testing.

Dan

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Quoted 2 lines

Yes, it's still snooping for all packets, but it's a lot fewer compares than looking for DHCP specifically.

Any thoughts on this Mahesh? Is this non-DHCP approach more to your liking? If so I'll generate an actual patch and do some testing.

Sorry about the late reply but some how I missed that.

Yes, this looks better, but I'm thinking of solving this issue with a different approach which does not involve snooping. Or if it does, it wont be in a fast path! It is sort of falling back to your original patch which eliminates setting / resetting the broadcast bit but after deferring the broadcast / multicast processing to a work-queue. This will keep the fast path clean and we can do all sort of jugglery in work-queue (if needed) without affecting the performance of the device (fast path) whether it's IPv6 or IPv4 traffic.

Also Eric pointed out how multicast is broken in IPvlan, that needs a fix too. I have cooked something, but needs some testing, I'll push out those patches as soon as I'm happy with it's testing.