Patchwork bridge: Pseudo-header required for the checksum of ICMP6 header of MLD

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Submitter Ang Way Chuang
Date Aug. 24, 2011, 6:10 a.m.
Message ID <4E5495EA.1080906@gmail.com>
Download mbox | patch
Permalink /patch/111251/
State Superseded
Delegated to: David Miller
Headers show

Comments

Ang Way Chuang - Aug. 24, 2011, 6:10 a.m.
Just saw Eric's patch for icmp6_type. Suspect this patch may have issue for reference
of ip6h after pskb_trim_rcsum()?

Checksum of ICMPv6 is not properly computed because the pseudo header is not used.
Thus, the MLD packet gets dropped by the bridge. This patch fixes the problem for my
testbed. This bug was made visible by commit ff9a57a62afbbe2d0f3a09af321f1fd7645f38a.

This patch has been tested on 3.0.3. Due to lack of understanding on the checksum
optimization and multicast snooping of the kernel stack, can someone please verify the
correctness of this patch?

Signed-off-by: Ang Way Chuang <wcang@sfc.wide.ad.jp>
---
index 2d85ca7..bbf361b 100644
---
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Eric Dumazet - Aug. 24, 2011, 7:18 a.m.
Le mercredi 24 août 2011 à 15:10 +0900, Ang Way Chuang a écrit :
> Just saw Eric's patch for icmp6_type. Suspect this patch may have issue for reference
> of ip6h after pskb_trim_rcsum()?
> 

I dont think so, because ip6h is against skb header, not skb2 one.


> Checksum of ICMPv6 is not properly computed because the pseudo header is not used.
> Thus, the MLD packet gets dropped by the bridge. This patch fixes the problem for my
> testbed. This bug was made visible by commit ff9a57a62afbbe2d0f3a09af321f1fd7645f38a.
> 
> This patch has been tested on 3.0.3. Due to lack of understanding on the checksum
> optimization and multicast snooping of the kernel stack, can someone please verify the
> correctness of this patch?
> 
> Signed-off-by: Ang Way Chuang <wcang@sfc.wide.ad.jp>
> ---
> index 2d85ca7..bbf361b 100644
> --- a/net/bridge/br_multicast.c
> +++ b/net/bridge/br_multicast.c
> @@ -1528,9 +1528,12 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
>  			break;
>  		/*FALLTHROUGH*/
>  	case CHECKSUM_NONE:
> -		skb2->csum = 0;
> -		if (skb_checksum_complete(skb2))
> +		if (!skb_csum_unnecessary(skb2) && csum_ipv6_magic(&ip6h->saddr,
> +			&ip6h->daddr, skb2->len, IPPROTO_ICMPV6,
> +			skb_checksum(skb2, 0, skb2->len, 0))) {
> +			err = -EINVAL;
>  			goto out;
> +		}
>  	}
>  
>  	err = 0;
> ---


Sorry, I cannot comment on this, checksum games are hard :(



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Patch

--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1528,9 +1528,12 @@  static int br_multicast_ipv6_rcv(struct net_bridge *br,
 			break;
 		/*FALLTHROUGH*/
 	case CHECKSUM_NONE:
-		skb2->csum = 0;
-		if (skb_checksum_complete(skb2))
+		if (!skb_csum_unnecessary(skb2) && csum_ipv6_magic(&ip6h->saddr,
+			&ip6h->daddr, skb2->len, IPPROTO_ICMPV6,
+			skb_checksum(skb2, 0, skb2->len, 0))) {
+			err = -EINVAL;
 			goto out;
+		}
 	}
 
 	err = 0;