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bridge: notify user space after fdb update

PATCH Applied Jon Maxwell 5 participants 5 messages May 29, 2014 – Jun 2, 2014

Subsystems (3)
Networking Network drivers Ethernet bridge
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Jon Maxwell

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#0 lore raw

PATCH 1/1 bridge: notify user space after fdb update

There has been a number incidents recently where customers running KVM have reported that VM hosts on different Hypervisors are unreachable. Based on pcap traces we found that the bridge was broadcasting the ARP request out onto the network. However some NICs have an inbuilt switch which on occasions were broadcasting the VMs ARP request back through the physical NIC on the Hypervisor. This resulted in the bridge changing ports and incorrectly learning that the VMs mac address was external. As a result the ARP reply was directed back onto the external network and VM never updated it's ARP cache. This patch will notify the bridge command, after a fdb has been updated to identify such port toggling.

Signed-off-by Jon Maxwell <[email protected]>
---
 net/bridge/br_fdb.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
net/bridge/br_fdb.c +7 -1
index 9203d5a..474d36f 100644
@@ -487,6 +487,7 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
 {
 	struct hlist_head *head = &br->hash[br_mac_hash(addr, vid)];
 	struct net_bridge_fdb_entry *fdb;
+	bool fdb_modified = false;
 
 	/* some users want to always flood. */
 	if (hold_time(br) == 0)

@@ -507,10 +508,15 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
 					source->dev->name);
 		} else {
 			/* fastpath: update of existing entry */
-			fdb->dst = source;
+			if (unlikely(source != fdb->dst)) {
+				fdb->dst = source;
+				fdb_modified = true;
+			}
 			fdb->updated = jiffies;
 			if (unlikely(added_by_user))
 				fdb->added_by_user = 1;
+			if (unlikely(fdb_modified))
+				fdb_notify(br, fdb, RTM_NEWNEIGH);
 		}
 	} else {
 		spin_lock(&br->hash_lock);
Signature · 1 line
1.8.3.1
Reviewed-by on v1 1/1
#1 lore raw
Quoted 11 lines · Thu, May 29, 2014 at 09:27:16AM CEST, [email protected] wrote:

There has been a number incidents recently where customers running KVM have reported that VM hosts on different Hypervisors are unreachable. Based on pcap traces we found that the bridge was broadcasting the ARP request out onto the network. However some NICs have an inbuilt switch which on occasions were broadcasting the VMs ARP request back through the physical NIC on the Hypervisor. This resulted in the bridge changing ports and incorrectly learning that the VMs mac address was external. As a result the ARP reply was directed back onto the external network and VM never updated it's ARP cache. This patch will notify the bridge command, after a fdb has been updated to identify such port toggling.

Quoted 1 line
Signed-off-by Jon Maxwell <[email protected]>
Reviewed-by Jiri Pirko <[email protected]>
Acked-by on v1 1/1
#2 lore raw
In reply to Jon Maxwell
Quoted 11 lines · Jon Maxwell

There has been a number incidents recently where customers running KVM have reported that VM hosts on different Hypervisors are unreachable. Based on pcap traces we found that the bridge was broadcasting the ARP request out onto the network. However some NICs have an inbuilt switch which on occasions were broadcasting the VMs ARP request back through the physical NIC on the Hypervisor. This resulted in the bridge changing ports and incorrectly learning that the VMs mac address was external. As a result the ARP reply was directed back onto the external network and VM never updated it's ARP cache. This patch will notify the bridge command, after a fdb has been updated to identify such port toggling.

Quoted 1 line
Signed-off-by Jon Maxwell <[email protected]>
Acked-by Toshiaki Makita <[email protected]>
Acked-by on v1 1/1
#3 lore raw
In reply to Jon Maxwell
Quoted 11 lines · On Thu, 29 May 2014 17:27:16 +1000 Jon Maxwell <[email protected]> wrote:

There has been a number incidents recently where customers running KVM have reported that VM hosts on different Hypervisors are unreachable. Based on pcap traces we found that the bridge was broadcasting the ARP request out onto the network. However some NICs have an inbuilt switch which on occasions were broadcasting the VMs ARP request back through the physical NIC on the Hypervisor. This resulted in the bridge changing ports and incorrectly learning that the VMs mac address was external. As a result the ARP reply was directed back onto the external network and VM never updated it's ARP cache. This patch will notify the bridge command, after a fdb has been updated to identify such port toggling.

Quoted 1 line
Signed-off-by Jon Maxwell <[email protected]>
Acked-by Stephen Hemminger <[email protected]>
maintainer Applied
#4 lore raw
In reply to Jon Maxwell

From: Jon Maxwell <[email protected]>
Date: Thu, 29 May 2014 17:27:16 +1000

Quoted 11 lines

There has been a number incidents recently where customers running KVM have reported that VM hosts on different Hypervisors are unreachable. Based on pcap traces we found that the bridge was broadcasting the ARP request out onto the network. However some NICs have an inbuilt switch which on occasions were broadcasting the VMs ARP request back through the physical NIC on the Hypervisor. This resulted in the bridge changing ports and incorrectly learning that the VMs mac address was external. As a result the ARP reply was directed back onto the external network and VM never updated it's ARP cache. This patch will notify the bridge command, after a fdb has been updated to identify such port toggling.

Quoted 1 line
Signed-off-by Jon Maxwell <[email protected]>

Applied, thanks.