vlan: Propagate MAC address to VLANs

The MAC address of the physical interface is only copied to the VLAN when it is first created, resulting in an inconsistency after MAC address changes of only newly created VLANs having an up-to-date MAC.

The VLANs should continue inheriting the MAC address of the physical interface, unless explicitly changed to be different from this. This allows IPv6 EUI64 addresses for the VLAN to reflect any changes to the MAC of the physical interface and thus for DAD to behave as expected.

Signed-off-by Mike Manning <[email protected]>

---
 include/linux/if_vlan.h |    2 ++
 net/8021q/vlan.c        |   17 +++++++++++------
 net/8021q/vlan_dev.c    |   13 ++++++++++---
 3 files changed, 23 insertions(+), 9 deletions(-)

include/linux/if_vlan.h +1 -0

@@ -138,6 +138,7 @@ struct netpoll;
  *     @flags: device flags
  *     @real_dev: underlying netdevice
  *     @real_dev_addr: address of underlying netdevice
+ *     @addr_assign_type: address assignment type
  *     @dent: proc dir entry
  *     @vlan_pcpu_stats: ptr to percpu rx stats
  */

net/8021q/vlan.c +10 -1

@@ -291,6 +291,15 @@ static void vlan_sync_address(struct net
        if (ether_addr_equal(vlan->real_dev_addr, dev->dev_addr))
                return;
 
+       /* vlan continues to inherit address of parent interface */
+       if (vlan->addr_assign_type == NET_ADDR_STOLEN) {
+               ether_addr_copy(vlandev->dev_addr, dev->dev_addr);
+               goto out;
+       }
+
+       if (!(vlandev->flags & IFF_UP))
+               goto out;
+
        /* vlan address was different from the old address and is equal to
         * the new address */
        if (!ether_addr_equal(vlandev->dev_addr, vlan->real_dev_addr) &&

@@ -303,6 +312,7 @@ static void vlan_sync_address(struct net
            !ether_addr_equal(vlandev->dev_addr, dev->dev_addr))
                dev_uc_add(dev, vlandev->dev_addr);
 
+out:
        ether_addr_copy(vlan->real_dev_addr, dev->dev_addr);
 }
 

@@ -389,13 +399,8 @@ static int vlan_device_event(struct noti
 
        case NETDEV_CHANGEADDR:
                /* Adjust unicast filters on underlying device */
-               vlan_group_for_each_dev(grp, i, vlandev) {

net/8021q/vlan_dev.c +6 -2

@@ -315,17 +315,21 @@ static int vlan_dev_stop(struct net_devi
 
 static int vlan_dev_set_mac_address(struct net_device *dev, void *p)
 {
-       struct net_device *real_dev = vlan_dev_priv(dev)->real_dev;
+       struct vlan_dev_priv *vlan = vlan_dev_priv(dev);
+       struct net_device *real_dev = vlan->real_dev;
        struct sockaddr *addr = p;
+       bool is_real_addr;
        int err;
 
        if (!is_valid_ether_addr(addr->sa_data))
                return -EADDRNOTAVAIL;
 
+       is_real_addr = ether_addr_equal(addr->sa_data, real_dev->dev_addr);
+
        if (!(dev->flags & IFF_UP))
                goto out;
 
-       if (!ether_addr_equal(addr->sa_data, real_dev->dev_addr)) {
+       if (!is_real_addr) {
                err = dev_uc_add(real_dev, addr->sa_data);
                if (err < 0)
                        return err;

Quoted 33 lines · Mike Manning

The MAC address of the physical interface is only copied to the VLAN when it is first created, resulting in an inconsistency after MAC address changes of only newly created VLANs having an up-to-date MAC.

The VLANs should continue inheriting the MAC address of the physical interface, unless explicitly changed to be different from this. This allows IPv6 EUI64 addresses for the VLAN to reflect any changes to the MAC of the physical interface and thus for DAD to behave as expected.

Signed-off-by Mike Manning <[email protected]>

---
 include/linux/if_vlan.h |    2 ++
 net/8021q/vlan.c        |   17 +++++++++++------
 net/8021q/vlan_dev.c    |   13 ++++++++++---
 3 files changed, 23 insertions(+), 9 deletions(-)

include/linux/if_vlan.h +2 -0

@@ -138,6 +138,7 @@ struct netpoll;
  *     @flags: device flags
  *     @real_dev: underlying netdevice
  *     @real_dev_addr: address of underlying netdevice
+ *     @addr_assign_type: address assignment type
  *     @dent: proc dir entry
  *     @vlan_pcpu_stats: ptr to percpu rx stats
  */

@@ -153,6 +154,7 @@ struct vlan_dev_priv {
 
        struct net_device                       *real_dev;
        unsigned char                           real_dev_addr[ETH_ALEN];
+       unsigned char                           addr_assign_type;
 

include/linux/if_vlan.h struct vlan_dev_priv { · line 160

Quoted 2 lines

include/linux/if_vlan.h +0 -0

        struct proc_dir_entry                   *dent;
        struct vlan_pcpu_stats __percpu         *vlan_pcpu_stats;

Please don't start adding new members to structures when it already exists in the net_device. If anything you should be able to drop read_dev_addr if you do this correctly because you shouldn't need to clone the lower dev address to watch for changes. All you will need to do is watch NET_ADDR_STOLEN.

Quoted 31 lines

net/8021q/vlan.c +10 -1

@@ -291,6 +291,15 @@ static void vlan_sync_address(struct net
        if (ether_addr_equal(vlan->real_dev_addr, dev->dev_addr))
                return;
 
+       /* vlan continues to inherit address of parent interface */
+       if (vlan->addr_assign_type == NET_ADDR_STOLEN) {
+               ether_addr_copy(vlandev->dev_addr, dev->dev_addr);
+               goto out;
+       }
+
+       if (!(vlandev->flags & IFF_UP))
+               goto out;
+
        /* vlan address was different from the old address and is equal to
         * the new address */
        if (!ether_addr_equal(vlandev->dev_addr, vlan->real_dev_addr) &&

@@ -303,6 +312,7 @@ static void vlan_sync_address(struct net
            !ether_addr_equal(vlandev->dev_addr, dev->dev_addr))
                dev_uc_add(dev, vlandev->dev_addr);
 
+out:
        ether_addr_copy(vlan->real_dev_addr, dev->dev_addr);
 }
 

@@ -389,13 +399,8 @@ static int vlan_device_event(struct noti
 
        case NETDEV_CHANGEADDR:
                /* Adjust unicast filters on underlying device */
-               vlan_group_for_each_dev(grp, i, vlandev) {

net/8021q/vlan.c static int vlan_device_event(struct noti · line 406

Quoted 10 lines

net/8021q/vlan.c +1 -5

-                       flgs = vlandev->flags;
-                       if (!(flgs & IFF_UP))
-                               continue;
-
+               vlan_group_for_each_dev(grp, i, vlandev)
                        vlan_sync_address(dev, vlandev);
-               }
                break;
 
        case NETDEV_CHANGEMTU:

So all of this is far more complicated than it needs to be. If NET_ADDR_STOLEN is set you have to follow the lower device MAC address, otherwise you maintain your own address and have to hold a reference to it on the lower device.

You should also be able to maintain the current logic of not updating a down interface on an address change. You don't need to update a stolen MAC address until the open routine is called for the interface.

Quoted 27 lines

net/8021q/vlan_dev.c +6 -2

@@ -315,17 +315,21 @@ static int vlan_dev_stop(struct net_devi
 
 static int vlan_dev_set_mac_address(struct net_device *dev, void *p)
 {
-       struct net_device *real_dev = vlan_dev_priv(dev)->real_dev;
+       struct vlan_dev_priv *vlan = vlan_dev_priv(dev);
+       struct net_device *real_dev = vlan->real_dev;
        struct sockaddr *addr = p;
+       bool is_real_addr;
        int err;
 
        if (!is_valid_ether_addr(addr->sa_data))
                return -EADDRNOTAVAIL;
 
+       is_real_addr = ether_addr_equal(addr->sa_data, real_dev->dev_addr);
+
        if (!(dev->flags & IFF_UP))
                goto out;
 
-       if (!ether_addr_equal(addr->sa_data, real_dev->dev_addr)) {
+       if (!is_real_addr) {
                err = dev_uc_add(real_dev, addr->sa_data);
                if (err < 0)
                        return err;

net/8021q/vlan_dev.c static int vlan_dev_set_mac_address(stru · line 345

Quoted 6 lines

net/8021q/vlan_dev.c +1 -0

@@ -336,6 +340,7 @@ static int vlan_dev_set_mac_address(stru
 
 out:
        ether_addr_copy(dev->dev_addr, addr->sa_data);
+       vlan->addr_assign_type = is_real_addr ? NET_ADDR_STOLEN : NET_ADDR_SET;
        return 0;
 }

Yeah so you probably don't need most of this. Just take a look at dev_set_mac_address. It will already update this to NET_ADDR_SET which is really what you want if the user specified a MAC address. At that point you should stop following the lower dev because the user may intend to have this MAC address be static while they change the lower dev address.

Quoted 4 lines

net/8021q/vlan_dev.c +0 -0

@@ -558,8 +563,10 @@ static int vlan_dev_init(struct net_devi
        /* ipv6 shared card related stuff */
        dev->dev_id = real_dev->dev_id;
 

net/8021q/vlan_dev.c static int vlan_dev_init(struct net_devi · line 572

Quoted 8 lines

net/8021q/vlan_dev.c +3 -1

-       if (is_zero_ether_addr(dev->dev_addr))
+       if (is_zero_ether_addr(dev->dev_addr)) {
                eth_hw_addr_inherit(dev, real_dev);
+               vlan_dev_priv(dev)->addr_assign_type = NET_ADDR_STOLEN;
+       }
        if (is_zero_ether_addr(dev->broadcast))
                memcpy(dev->broadcast, real_dev->broadcast, dev->addr_len);
 

This should be just dev->addr_assign_type = NET_ADDR_STOLEN. No need to put this in a private structure member.

Quoted 34 lines · Alexander Duyck

Quoted 33 lines · Mike Manning

The MAC address of the physical interface is only copied to the VLAN when it is first created, resulting in an inconsistency after MAC address changes of only newly created VLANs having an up-to-date MAC.

The VLANs should continue inheriting the MAC address of the physical interface, unless explicitly changed to be different from this. This allows IPv6 EUI64 addresses for the VLAN to reflect any changes to the MAC of the physical interface and thus for DAD to behave as expected.

Signed-off-by Mike Manning <[email protected]>

---
 include/linux/if_vlan.h |    2 ++
 net/8021q/vlan.c        |   17 +++++++++++------
 net/8021q/vlan_dev.c    |   13 ++++++++++---
 3 files changed, 23 insertions(+), 9 deletions(-)

include/linux/if_vlan.h +2 -0

@@ -138,6 +138,7 @@ struct netpoll;
  *     @flags: device flags
  *     @real_dev: underlying netdevice
  *     @real_dev_addr: address of underlying netdevice
+ *     @addr_assign_type: address assignment type
  *     @dent: proc dir entry
  *     @vlan_pcpu_stats: ptr to percpu rx stats
  */

@@ -153,6 +154,7 @@ struct vlan_dev_priv {
 
        struct net_device                       *real_dev;
        unsigned char                           real_dev_addr[ETH_ALEN];
+       unsigned char                           addr_assign_type;
 

Quoted 9 lines

include/linux/if_vlan.h struct vlan_dev_priv { · line 160

Quoted 2 lines

include/linux/if_vlan.h +0 -0

        struct proc_dir_entry                   *dent;
        struct vlan_pcpu_stats __percpu         *vlan_pcpu_stats;

Please don't start adding new members to structures when it already exists in the net_device. If anything you should be able to drop read_dev_addr if you do this correctly because you shouldn't need to clone the lower dev address to watch for changes. All you will need to do is watch NET_ADDR_STOLEN.

Thanks for the detailed review. I had initially used the existing type in net_device, but the problem with this was that it got overwritten to NET_ADDR_SET in dev_set_mac_address(), which I was reluctant to modify. It would just be a case of setting the type earlier in that function (and caching the previous value in case there is an error).

However, based on your later comment, it seems I should not bother with the approach I have here, namely that if the VLAN MAC is set to the same value as that of the lower device MAC, that is to be considered as resetting it and thus for MAC inheritance to resume. Instead, I will just make this a 1-shot transition, i.e. the VLAN MAC starts off as inherited, and if it is set to anything (even the value of the lower device MAC), inheritance is stopped. I agree this makes for a far simpler changeset.

I don't think I can remove real_dev_addr, as that is still needed for the existing functionality in vlan_sync_address() to determine if the sync should be done, also as a way of caching it for handling in vlan_dev_open().

As a matter of interest, what is the advantage of not updating the VLAN MAC when it is down? I appreciate that one should not add/delete secondary unicast addresses in this case, but there is no such restriction for copying the MAC.

Quoted 59 lines · Mike Manning

Quoted 34 lines · Alexander Duyck

Quoted 33 lines · Mike Manning

The MAC address of the physical interface is only copied to the VLAN when it is first created, resulting in an inconsistency after MAC address changes of only newly created VLANs having an up-to-date MAC.

The VLANs should continue inheriting the MAC address of the physical interface, unless explicitly changed to be different from this. This allows IPv6 EUI64 addresses for the VLAN to reflect any changes to the MAC of the physical interface and thus for DAD to behave as expected.

Signed-off-by Mike Manning <[email protected]>

---
 include/linux/if_vlan.h |    2 ++
 net/8021q/vlan.c        |   17 +++++++++++------
 net/8021q/vlan_dev.c    |   13 ++++++++++---
 3 files changed, 23 insertions(+), 9 deletions(-)

include/linux/if_vlan.h +2 -0

@@ -138,6 +138,7 @@ struct netpoll;
  *     @flags: device flags
  *     @real_dev: underlying netdevice
  *     @real_dev_addr: address of underlying netdevice
+ *     @addr_assign_type: address assignment type
  *     @dent: proc dir entry
  *     @vlan_pcpu_stats: ptr to percpu rx stats
  */

@@ -153,6 +154,7 @@ struct vlan_dev_priv {
 
        struct net_device                       *real_dev;
        unsigned char                           real_dev_addr[ETH_ALEN];
+       unsigned char                           addr_assign_type;
 

Quoted 9 lines

include/linux/if_vlan.h struct vlan_dev_priv { · line 160

Quoted 2 lines

include/linux/if_vlan.h +0 -0

        struct proc_dir_entry                   *dent;
        struct vlan_pcpu_stats __percpu         *vlan_pcpu_stats;

Please don't start adding new members to structures when it already exists in the net_device. If anything you should be able to drop read_dev_addr if you do this correctly because you shouldn't need to clone the lower dev address to watch for changes. All you will need to do is watch NET_ADDR_STOLEN.

Thanks for the detailed review. I had initially used the existing type in net_device, but the problem with this was that it got overwritten to NET_ADDR_SET in dev_set_mac_address(), which I was reluctant to modify. It would just be a case of setting the type earlier in that function (and caching the previous value in case there is an error).

However, based on your later comment, it seems I should not bother with the approach I have here, namely that if the VLAN MAC is set to the same value as that of the lower device MAC, that is to be considered as resetting it and thus for MAC inheritance to resume. Instead, I will just make this a 1-shot transition, i.e. the VLAN MAC starts off as inherited, and if it is set to anything (even the value of the lower device MAC), inheritance is stopped. I agree this makes for a far simpler changeset.

Quoted 3 lines

I don't think I can remove real_dev_addr, as that is still needed for the existing functionality in vlan_sync_address() to determine if the sync should be done, also as a way of caching it for handling in vlan_dev_open().

The thing is that logic isn't really needed anymore though if you are going to be following the lower dev. If you follow the code what it is doing is adding the address via dev_uc_add if the lower address moves away from the VLAN address. With your changes you are updating the VLAN MAC address to the lower value in the NET_ADDR_STOLEN case so you don't need to add or remove an extra unicast address. If the user sets the MAC address you can then use the vlandev->dev_addr as the address you add/remove from the unicast list and you probably don't need to bother with tracking the lower device state anyway.

Quoted 4 lines

As a matter of interest, what is the advantage of not updating the VLAN MAC when it is down? I appreciate that one should not add/delete secondary unicast addresses in this case, but there is no such restriction for copying the MAC.

Basically you are just wasting cycles messing with it while it is down. You don't need to bother with syncing up the addresses until you bring the interface up. At that point you essentially need to do the vlan_sync_address type work anyway because you have to push your address to the lower dev, or you have to pull it up from the lower dev in the case of the stolen address. You don't want to have MAC addresses written to the device for an interface that is down.