Re: IPv6 multicast snooping behaviour on 2.6.39-rc2 and later

This is what I found so far from debugging.

The packet is not forwarded due to the failed checksum at br_multicast.c:1533

        case CHECKSUM_NONE:
                skb2->csum = 0;
                if (skb_checksum_complete(skb2))
                        goto out;
        }

Contrary to description of commit ff9a57a6, when the patch of commit ff9a57a6 is applied,
pskb_trim_rcsum is never called at all on my testbed. When commit ff9a57a6 is reverted,
pskb_trim_rcsum will be called. The difference is:

with commit ff9a57a6,
   pskb_trim_rcsum is never called, br_multicast_ipv6_rcv returns -EINVAL which causes
   br_handle_frame_finish to drop the packet

without commit ff9a57a6,
   pskb_trim_rcsum is called overwriting err with 0. br_multicast_ipv6_rcv still fails on the
   same line (skb_checksum_complete). But the difference is err is set to 0 this time. Thereby,
   allowing the packet to be forwarded.

Anyway, I don't think the behaviour is correct with or without commit ff9a57a6



On 23/08/11 23:04, Ang Way Chuang wrote:

Tough luck :( Got no love from bridge. It still doesn't work with your latest patch. Please keep sending those patches.

On 23/08/11 22:10, Eric Dumazet wrote:

quoted

Le mardi 23 août 2011 à 21:31 +0900, Ang Way Chuang a écrit :

quoted

Sorry for the blurb. I hope I've configured thunderbird properly to
send in plain text. Hope you received my reply. I tried your patch on
3.0.3 and it didn't fix the problem.

Thanks for trying !

Ok could you please try following patch then ?

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 2d85ca7..e9b32a3 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c

@@ -1497,7 +1497,7 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
      if (!pskb_may_pull(skb2, offset + sizeof(struct icmp6hdr)))
          goto out;

-    len -= offset - skb_network_offset(skb2);
+    len -= offset;

      __skb_pull(skb2, offset);
      skb_reset_transport_header(skb2);

@@ -1520,6 +1520,7 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
          err = pskb_trim_rcsum(skb2, len);
          if (err)
              goto out;
+        icmp6h = icmp6_hdr(skb2);
      }

      switch (skb2->ip_summed) {

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