netdev - Re: [PATCH] bridge: mcast snooping, fix IPv6 MLD checksum calculation

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Date:	Sun, 27 Mar 2011 14:37:49 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Linus Lüssing <linus.luessing@....de>
Cc:	bridge@...ts.linux-foundation.org,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>,
	netdev@...r.kernel.org
Subject: Re: [PATCH] bridge: mcast snooping, fix IPv6 MLD checksum
	calculation

On Sun, Mar 27, 2011 at 08:27:23AM +0200, Linus Lüssing wrote:
> In contrast to IGMP, the MLDv1/2 message checksum needs to include an
> IPv6 "pseudo-header" in the calculations (see RFC2710, section 3.3;
> RFC3810, section 5.1.2).
> 
> The multicast snooping feature of the bridge code however did not take
> this "pseudo-header" into consideration for the checksum validation when
> parsing a snooped IPv6 MLDv1/2 message of another host, leading to
> possibly ignored, though valid MLDv1/2 messages. This commit shall fix
> this issue.
> 
> Signed-off-by: Linus Lüssing <linus.luessing@....de>
> ---
>  net/bridge/br_multicast.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
> index f61eb2e..47fae4f 100644
> --- a/net/bridge/br_multicast.c
> +++ b/net/bridge/br_multicast.c
> @@ -1525,7 +1525,10 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
>  			break;
>  		/*FALLTHROUGH*/
>  	case CHECKSUM_NONE:
> -		skb2->csum = 0;
> +		skb2->csum = ~csum_unfold(csum_ipv6_magic(&ip6h->saddr,
> +							  &ip6h->daddr,
> +							  skb2->len,
> +							  nexthdr, 0));

You also need to include the pseudo-header for the CHECKSUM_COMPLETE
case, before we've fallen through (which only happens if the
hardware checksum doesn't match).

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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