[PATCH net] bridge: notify user space after fdb update

[PATCH net] bridge: notify user space after fdb update

[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.

Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com>
---
 net/bridge/br_fdb.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 9203d5a..f3ee2da 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -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 = 0;
 
 	/* 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 = 1;
+				}
 			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);
-- 
1.8.3.1

Re: [PATCH net] bridge: notify user space after fdb update

[Sergei Shtylyov]

Hello.

On 05/28/2014 02:45 AM, Jon Maxwell 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.

> Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com>
> ---
>   net/bridge/br_fdb.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)

> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
> index 9203d5a..f3ee2da 100644
> --- a/net/bridge/br_fdb.c
> +++ b/net/bridge/br_fdb.c
> @@ -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 = 0;

    s/0/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 = 1;

   s/1/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);

WBR, Sergei

Re: [PATCH net] bridge: notify user space after fdb update

[Vlad Yasevich]

On 05/27/2014 06:45 PM, Jon Maxwell 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.
> 
> Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com>
> ---
>  net/bridge/br_fdb.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
> index 9203d5a..f3ee2da 100644
> --- a/net/bridge/br_fdb.c
> +++ b/net/bridge/br_fdb.c
> @@ -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 = 0;
>  
>  	/* 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 = 1;
> +				}

This looks over-indented.

-vlad

>  			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);
> 

Re: [PATCH net] bridge: notify user space after fdb update

[David Miller]

From: Jon Maxwell <jmaxwell37@gmail.com>
Date: Thu, 29 May 2014 17:27:16 +1000

> 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 <jmaxwell37@gmail.com>

Applied, thanks.

Re: [PATCH net] bridge: notify user space after fdb update

[Stephen Hemminger]

On Thu, 29 May 2014 17:27:16 +1000
Jon Maxwell <jmaxwell37@gmail.com> 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.
> 
> Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com>

Acked-by: Stephen Hemminger <stephen@networkplumber.org>

Re: [PATCH net] bridge: notify user space after fdb update

[Toshiaki Makita]

(2014/05/29 16:27), Jon Maxwell 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.
> 
> Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com>

Acked-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>

Re: [PATCH net] bridge: notify user space after fdb update

[Jiri Pirko]

Thu, May 29, 2014 at 09:27:16AM CEST, jmaxwell37@gmail.com 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.
>
>Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com>

Reviewed-by: Jiri Pirko <jiri@resnulli.us>

[PATCH net] bridge: notify user space after fdb update

[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.

Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com>
---
 net/bridge/br_fdb.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 9203d5a..474d36f 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -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);
-- 
1.8.3.1