IGMP snooping: set mrouters_only flag for IPv4 traffic properly

Upon reception of a IGMP/IGMPv2 membership report the kernel sets the
mrouters_only flag in a skb that may be a clone of the original skb, which
means that sometimes the bridge loses track of membership report packets (cb
buffers are tied to a specifici skb and not shared) and it ends up forwading
join requests to the bridge interface.

This can cause unexpected membership timeouts and intermitent/permanent loss of connectivity as described in RFC 4541 [2.1.1. IGMP Forwarding Rules]:

    A snooping switch should forward IGMP Membership Reports only to
    those ports where multicast routers are attached.
    [...]
    Sending membership reports to other hosts can result, for IGMPv1
    and IGMPv2, in unintentionally preventing a host from joining a
    specific multicast group.


Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Tested-by: Hayato Kakuta <kakuta.hayato@oss.ntt.co.jp>
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On Mon, 13 Jun 2011 12:02:43 +0900
Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp> wrote:

> Upon reception of a IGMP/IGMPv2 membership report the kernel sets the
> mrouters_only flag in a skb that may be a clone of the original skb, which
> means that sometimes the bridge loses track of membership report packets (cb
> buffers are tied to a specifici skb and not shared) and it ends up forwading
> join requests to the bridge interface.
> 
> This can cause unexpected membership timeouts and intermitent/permanent loss of connectivity as described in RFC 4541 [2.1.1. IGMP Forwarding Rules]:
> 
>     A snooping switch should forward IGMP Membership Reports only to
>     those ports where multicast routers are attached.
>     [...]
>     Sending membership reports to other hosts can result, for IGMPv1
>     and IGMPv2, in unintentionally preventing a host from joining a
>     specific multicast group.
> 
> 
> Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
> Tested-by: Hayato Kakuta <kakuta.hayato@oss.ntt.co.jp>
> ---
> 
> diff -urNp linux-3.0-rc2-orig/net/bridge/br_multicast.c linux-3.0-rc2/net/bridge/br_multicast.c
> --- linux-3.0-rc2-orig/net/bridge/br_multicast.c	2011-06-09 13:34:04.164261031 +0900
> +++ linux-3.0-rc2/net/bridge/br_multicast.c	2011-06-09 20:04:23.473930447 +0900
> @@ -1424,7 +1424,7 @@ static int br_multicast_ipv4_rcv(struct
>  	switch (ih->type) {
>  	case IGMP_HOST_MEMBERSHIP_REPORT:
>  	case IGMPV2_HOST_MEMBERSHIP_REPORT:
> -		BR_INPUT_SKB_CB(skb2)->mrouters_only = 1;
> +		BR_INPUT_SKB_CB(skb)->mrouters_only = 1;
>  		err = br_ip4_multicast_add_group(br, port, ih->group);
>  		break;
>  	case IGMPV3_HOST_MEMBERSHIP_REPORT:

Acked-by: Stephen Hemminger <shemminger@vyatta.com>
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On Tue, 2011-06-14 at 13:22 -0400, Stephen Hemminger wrote:
> On Mon, 13 Jun 2011 12:02:43 +0900
> Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp> wrote:
> 
> > Upon reception of a IGMP/IGMPv2 membership report the kernel sets the
> > mrouters_only flag in a skb that may be a clone of the original skb, which
> > means that sometimes the bridge loses track of membership report packets (cb
> > buffers are tied to a specifici skb and not shared) and it ends up forwading
> > join requests to the bridge interface.
> > 
> > This can cause unexpected membership timeouts and intermitent/permanent loss of connectivity as described in RFC 4541 [2.1.1. IGMP Forwarding Rules]:
> > 
> >     A snooping switch should forward IGMP Membership Reports only to
> >     those ports where multicast routers are attached.
> >     [...]
> >     Sending membership reports to other hosts can result, for IGMPv1
> >     and IGMPv2, in unintentionally preventing a host from joining a
> >     specific multicast group.
> > 
> > 
> > Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
> > Tested-by: Hayato Kakuta <kakuta.hayato@oss.ntt.co.jp>
> > ---
> > 
> > diff -urNp linux-3.0-rc2-orig/net/bridge/br_multicast.c linux-3.0-rc2/net/bridge/br_multicast.c
> > --- linux-3.0-rc2-orig/net/bridge/br_multicast.c	2011-06-09 13:34:04.164261031 +0900
> > +++ linux-3.0-rc2/net/bridge/br_multicast.c	2011-06-09 20:04:23.473930447 +0900
> > @@ -1424,7 +1424,7 @@ static int br_multicast_ipv4_rcv(struct
> >  	switch (ih->type) {
> >  	case IGMP_HOST_MEMBERSHIP_REPORT:
> >  	case IGMPV2_HOST_MEMBERSHIP_REPORT:
> > -		BR_INPUT_SKB_CB(skb2)->mrouters_only = 1;
> > +		BR_INPUT_SKB_CB(skb)->mrouters_only = 1;
> >  		err = br_ip4_multicast_add_group(br, port, ih->group);
> >  		break;
> >  	case IGMPV3_HOST_MEMBERSHIP_REPORT:
> 
> Acked-by: Stephen Hemminger <shemminger@vyatta.com>

Can I take that as an acked-by for the IPv6 patch too?

Thanks,
Fernando

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