diff mbox

bridge: mcast snooping, fix IPv6 MLD checksum calculation

Message ID 1301207244-10428-2-git-send-email-linus.luessing@web.de
State Changes Requested, archived
Delegated to: David Miller
Headers show

Commit Message

Linus Lüssing March 27, 2011, 6:27 a.m. UTC 
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@web.de>
---
 net/bridge/br_multicast.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

Comments

Herbert Xu March 27, 2011, 6:37 a.m. UTC | #1 
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@web.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,
Linus Lüssing March 27, 2011, 7:06 a.m. UTC | #2 
So instead of 'if (!csum_fold(skb2->csum))' it should be this?
---
if (!csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
                     skb2->len, nexthdr, skb2->csum))
---
(I'm peeking a little bit at
http://lxr.linux.no/linux+*/net/ipv6/netfilter.c#L98)

Hmm, if so, then I don't know how to test and verify that now though.

Cheers, Linus

On Sun, Mar 27, 2011 at 02:37:49PM +0800, Herbert Xu wrote:
> 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@web.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@gondor.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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Herbert Xu March 27, 2011, 7:52 a.m. UTC | #3 
On Sun, Mar 27, 2011 at 09:06:45AM +0200, Linus Lüssing wrote:
> So instead of 'if (!csum_fold(skb2->csum))' it should be this?
> ---
> if (!csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
>                      skb2->len, nexthdr, skb2->csum))
> ---
> (I'm peeking a little bit at
> http://lxr.linux.no/linux+*/net/ipv6/netfilter.c#L98)

Yes that looks about right.

> Hmm, if so, then I don't know how to test and verify that now though.

You'd need a NIC that supported this to test.  Although I wouldn't
worry about it too much as the same code patterns appears over and
over again in our stack.  Perhaps we should put it in a helper.

Thanks,
David Miller March 30, 2011, 9:29 a.m. UTC | #4 
From: Linus Lüssing <linus.luessing@web.de>
Date: Sun, 27 Mar 2011 08:27:23 +0200

> 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@web.de>

I'm waiting for am updated version of this patch which addresses Herbert
Xu's feedback.
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diff mbox

Patch

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));
 		if (skb_checksum_complete(skb2))
 			goto out;
 	}