MLD compatibility mode doesn't account for extension headers [PATCH]

MLD compatibility mode doesn't account for extension headers [PATCH]

[David Stevens]

[-- Attachment #1: Type: text/plain, Size: 1000 bytes --]





Dave,
      The MLD v1 compatibility mode checks don't account for the
fact that extension headers are included in the ipv6 payload_len field.
That makes MLDv1 queries that include extension headers (like
Router Alert) appear to be v2 packets.
      The below patch fixes the problem.

                              +-DLS

--- linux-2.6.0-test9-bk23F2/net/ipv6/mcast.c   2003-11-21 15:53:23.916402736 -0800
+++ linux-2.6.0-test9-bk23F3/net/ipv6/mcast.c   2003-11-21 15:51:31.360513832 -0800
@@ -1017,7 +1017,9 @@
      if (!pskb_may_pull(skb, sizeof(struct in6_addr)))
            return -EINVAL;

-     len = ntohs(skb->nh.ipv6h->payload_len);
+     /* compute payload length excluding extension headers */
+     len = ntohs(skb->nh.ipv6h->payload_len) + sizeof(struct ipv6hdr);
+     len -= (char *)skb->h.raw - (char *)skb->nh.ipv6h;

      /* Drop queries with not link local source */
      if (!(ipv6_addr_type(&skb->nh.ipv6h->saddr)&IPV6_ADDR_LINKLOCAL))

(See attached file: MLDext.patch)

[-- Attachment #2: MLDext.patch --]
[-- Type: application/octet-stream, Size: 601 bytes --]

--- linux-2.6.0-test9-bk23F2/net/ipv6/mcast.c	2003-11-21 15:53:23.916402736 -0800
+++ linux-2.6.0-test9-bk23F3/net/ipv6/mcast.c	2003-11-21 15:51:31.360513832 -0800
@@ -1017,7 +1017,9 @@
 	if (!pskb_may_pull(skb, sizeof(struct in6_addr)))
 		return -EINVAL;
 
-	len = ntohs(skb->nh.ipv6h->payload_len);
+	/* compute payload length excluding extension headers */
+	len = ntohs(skb->nh.ipv6h->payload_len) + sizeof(struct ipv6hdr);
+	len -= (char *)skb->h.raw - (char *)skb->nh.ipv6h; 
 
 	/* Drop queries with not link local source */
 	if (!(ipv6_addr_type(&skb->nh.ipv6h->saddr)&IPV6_ADDR_LINKLOCAL))

Re: MLD compatibility mode doesn't account for extension headers [PATCH]

[David S. Miller]

On Fri, 21 Nov 2003 17:08:07 -0700
David Stevens <dlstevens@us.ibm.com> wrote:

>       The MLD v1 compatibility mode checks don't account for the
> fact that extension headers are included in the ipv6 payload_len field.
> That makes MLDv1 queries that include extension headers (like
> Router Alert) appear to be v2 packets.
>       The below patch fixes the problem.

Looks good.  I assume that all extension headers must appear
_before_ the igmp stuff, and therefore no other headers may
appear afterwards.

I'll apply this, thanks.

Re: MLD compatibility mode doesn't account for extension headers [PATCH]

[David Stevens]

>Looks good.  I assume that all extension headers must appear
>_before_ the igmp stuff, and therefore no other headers may
>appear afterwards.

Yes, MLD is the payload, so all extension headers must be
between the IPv6 header and the MLD header.

                        thanks, Dave,

                              +-DLS