[Bridge] [PATCH] bridge: relay bridge multicast pkgs if !STP

[Joakim Tjernlund]

Currently the bridge drops all STP pkgs when
STP is off. This makes the bridge relay the Bridge Group
multicast address, 01:80:c2:00:00:00, when STP is off.
This allows for loop detection by other bridges doing STP.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund at transmode.se>
---
 net/bridge/br_input.c |   14 +++++++++++++-
 1 files changed, 13 insertions(+), 1 deletions(-)

diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 30b8877..8197823 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -112,6 +112,17 @@ static inline int is_link_local(const unsigned char *dest)
 	return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
 }
 
+/* Does address match the Bride Group multicast address.
+ * 01:80:c2:00:00:00
+ */
+static inline int is_bridge_group(const unsigned char *dest)
+{
+	__be16 *a = (__be16 *)dest;
+	static const __be16 *b = (const __be16 *)br_group_address;
+
+	return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | (a[2] ^ b[2])) == 0;
+}
+
 /*
  * Called via br_handle_frame_hook.
  * Return NULL if skb is handled
@@ -137,7 +148,8 @@ struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
 		if (NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 			    NULL, br_handle_local_finish))
 			return NULL;	/* frame consumed by filter */
-		else
+		/* Relay Bridge Group address is STP is off */
+		if (!(p->br->stp_enabled == BR_NO_STP && is_bridge_group(dest)))
 			return skb;	/* continue processing */
 	}
 
-- 
1.6.2.3