Linux Ethernet Bridging - Nov 2011 - [Bridge] [PATCH] bridge: Cannot communicate with brX when its MAC address is changed

When the MAC address of a bridge interface is changed, it cannot communicate
with others. Because Whether or not a packet should be transferred to bridge
interface depends on whether or not dst of a packet is in fdb and is_local=y.
If we change MAC address of a bridge interface, it isn't in fdb.

This patch adds an condition that dst of a packet matches MAC address of
a bridge interface to the conventional condition.

Signed-off-by: Koki Sanagi <sanagi.koki at jp.fujitsu.com>
---
 net/bridge/br_input.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 5a31731..4e5c862 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -94,7 +94,8 @@ int br_handle_frame_finish(struct sk_buff *skb)
 			skb2 = skb;
 
 		br->dev->stats.multicast++;
-	} else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
+	} else if ((dst = __br_fdb_get(br, dest) && dst->is_local) ||
+		   !compare_ether_addr(p->br->dev->dev_addr, dest)) {
 		skb2 = skb;
 		/* Do not forward the packet since it's local. */
 		skb = NULL;

From: Koki Sanagi <sanagi.koki at jp.fujitsu.com>
Date: Wed, 30 Nov 2011 17:31:18 +0900
> When the MAC address of a bridge interface is changed, it cannot
communicate
> with others. Because Whether or not a packet should be transferred to
bridge
> interface depends on whether or not dst of a packet is in fdb and
is_local=y.
> If we change MAC address of a bridge interface, it isn't in fdb.
> 
> This patch adds an condition that dst of a packet matches MAC address of
> a bridge interface to the conventional condition.
> 
> Signed-off-by: Koki Sanagi <sanagi.koki at jp.fujitsu.com>
This looks like a patch I've seen before, and in any event it makes
more sense to update the FDB when the MAC changes instead of adding a
special bypass rule.

Stephen?
> ---
>  net/bridge/br_input.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
> index 5a31731..4e5c862 100644
> --- a/net/bridge/br_input.c
> +++ b/net/bridge/br_input.c
> @@ -94,7 +94,8 @@ int br_handle_frame_finish(struct sk_buff *skb)
>  			skb2 = skb;
>  
>  		br->dev->stats.multicast++;
> -	} else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
> +	} else if ((dst = __br_fdb_get(br, dest) && dst->is_local) ||
> +		   !compare_ether_addr(p->br->dev->dev_addr, dest)) {
>  		skb2 = skb;
>  		/* Do not forward the packet since it's local. */
>  		skb = NULL;

On Wed, 30 Nov 2011 17:31:18 +0900
Koki Sanagi <sanagi.koki at jp.fujitsu.com> wrote:
> When the MAC address of a bridge interface is changed, it cannot
communicate
> with others. Because Whether or not a packet should be transferred to
bridge
> interface depends on whether or not dst of a packet is in fdb and
is_local=y.
> If we change MAC address of a bridge interface, it isn't in fdb.
> 
> This patch adds an condition that dst of a packet matches MAC address of
> a bridge interface to the conventional condition.
> 
> Signed-off-by: Koki Sanagi <sanagi.koki at jp.fujitsu.com>
> ---
>  net/bridge/br_input.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
> index 5a31731..4e5c862 100644
> --- a/net/bridge/br_input.c
> +++ b/net/bridge/br_input.c
> @@ -94,7 +94,8 @@ int br_handle_frame_finish(struct sk_buff *skb)
>  			skb2 = skb;
>  
>  		br->dev->stats.multicast++;
> -	} else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
> +	} else if ((dst = __br_fdb_get(br, dest) && dst->is_local) ||
> +		   !compare_ether_addr(p->br->dev->dev_addr, dest)) {
>  		skb2 = skb;
>  		/* Do not forward the packet since it's local. */
>  		skb = NULL;
> 
There is a problem with paren's in this version of the patch, don't
apply it!

Looked into using fdb to handle this, but then there would be fdb entries
where the destination port entry was either NULL (or a dummy), and that
would require a bunch of auditing of all usages and could introduce new
bugs.

I am testing a patch that does same thing by moving compare_ether up
to where broadcast is tested.