bridge: don't route packets while learning

While in the STP learning state, don't route packets; wait until
forwarding delay has expired. The purpose of the forwarding delay
is to detect loops in the network, and if a brouter started up
and started forwarding, it could cause a flood.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>

1 files changed, 10 insertions, 7 deletions

diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 2f5c379d9ffa..8a5527632092 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -129,7 +129,7 @@ struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
         const unsigned char *dest = eth_hdr(skb)->h_dest;
 
         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
-                goto err;
+                goto drop;
 
         if (unlikely(is_link_local(dest))) {
                 skb->pkt_type = PACKET_HOST;
@@ -138,22 +138,25 @@ struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
                                 NULL, br_handle_local_finish) == 0) ? skb : NULL;
         }
 
-        if (p->state == BR_STATE_FORWARDING || p->state == BR_STATE_LEARNING) {
+        switch (p->state) {
+        case BR_STATE_FORWARDING:
+
                 if (br_should_route_hook) {
                         if (br_should_route_hook(&skb))
                                 return skb;
                         dest = eth_hdr(skb)->h_dest;
                 }
-
+                /* fall through */
+        case BR_STATE_LEARNING:
                 if (!compare_ether_addr(p->br->dev->dev_addr, dest))
                         skb->pkt_type = PACKET_HOST;
 
                 NF_HOOK(PF_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
                         br_handle_frame_finish);
-                return NULL;
+                break;
+        default:
+drop:
+                kfree_skb(skb);
         }
-
-err:
-        kfree_skb(skb);
         return NULL;
 }