net: ipv6 bind to device issue

hi,

The issue raises when having 2 NICs both assigned the same
IPv6 global address.

If a sender binds to a particular NIC (SO_BINDTODEVICE),
the outgoing traffic is being sent via the first found.
The bonded device is thus not taken into an account during the
routing.


From the ip6_route_output function:

If the binding address is multicast, linklocal or loopback,
the RT6_LOOKUP_F_IFACE bit is set, but not for global address.

So binding global address will neglect SO_BINDTODEVICE-binded device,
because the fib6_rule_lookup function path won't check for the
flowi::oif field and take first route that fits.

Following patch should handle the issue.

wbr,
jirka


Signed-off-by: Jiri Olsa <jolsa@redhat.com>
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Jiri Olsa wrote:
> Signed-off-by: Jiri Olsa <jolsa@redhat.com>
> ---
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index c2438e8..7bf7717 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -815,7 +815,7 @@ struct dst_entry * ip6_route_output(struct net *net, struct sock *sk,
>  {
>  	int flags = 0;
>  
> -	if (rt6_need_strict(&fl->fl6_dst))
> +	if (rt6_need_strict(&fl->fl6_dst) || fl->oif)
>  		flags |= RT6_LOOKUP_F_IFACE;
>  
>  	if (!ipv6_addr_any(&fl->fl6_src))

Acked-by: Brian Haley <brian.haley@hp.com>

Saw this within the past month here too and have been testing
this same fix without problems.
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On Tue, Apr 20, 2010 at 02:46:12PM +0200, Jiri Olsa wrote:
> hi,
> 
> The issue raises when having 2 NICs both assigned the same
> IPv6 global address.
> 
> If a sender binds to a particular NIC (SO_BINDTODEVICE),
> the outgoing traffic is being sent via the first found.
> The bonded device is thus not taken into an account during the
> routing.
> 
> 
> From the ip6_route_output function:
> 
> If the binding address is multicast, linklocal or loopback,
> the RT6_LOOKUP_F_IFACE bit is set, but not for global address.
> 
> So binding global address will neglect SO_BINDTODEVICE-binded device,
> because the fib6_rule_lookup function path won't check for the
> flowi::oif field and take first route that fits.
> 
> Following patch should handle the issue.
> 
> wbr,
> jirka
> 
> 
> Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Scott Otto <scott.otto@alcatel-lucent.com>

> ---
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index c2438e8..7bf7717 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -815,7 +815,7 @@ struct dst_entry * ip6_route_output(struct net *net, struct sock *sk,
>  {
>  	int flags = 0;
>  
> -	if (rt6_need_strict(&fl->fl6_dst))
> +	if (rt6_need_strict(&fl->fl6_dst) || fl->oif)
>  		flags |= RT6_LOOKUP_F_IFACE;
>  
>  	if (!ipv6_addr_any(&fl->fl6_src))
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Jiri Olsa wrote:
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index c2438e8..7bf7717 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -815,7 +815,7 @@ struct dst_entry * ip6_route_output(struct net *net, struct sock *sk,
>  {
>  	int flags = 0;
>  
> -	if (rt6_need_strict(&fl->fl6_dst))
> +	if (rt6_need_strict(&fl->fl6_dst) || fl->oif)
>  		flags |= RT6_LOOKUP_F_IFACE;
>  
>  	if (!ipv6_addr_any(&fl->fl6_src))

Actually, looking at this again, we might want to swap the order
here since fl->oif should be filled-in for most link-local and
multicast requests calling this:

	if (fl->oif || rt6_need_strict(&fl->fl6_dst))

Just a thought, but it potentially saves a call to determine
the scope of the address.

-Brian
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From: Brian Haley <brian.haley@hp.com>
Date: Tue, 20 Apr 2010 14:13:39 -0400

> Actually, looking at this again, we might want to swap the order
> here since fl->oif should be filled-in for most link-local and
> multicast requests calling this:
> 
> 	if (fl->oif || rt6_need_strict(&fl->fl6_dst))
> 
> Just a thought, but it potentially saves a call to determine
> the scope of the address.

Yes I think we should make this change.

Jiri please respin your patch with the argument order
reversed so that we can make the inexpensive check before
the expensive one.

Thanks.
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From: David Miller <davem@davemloft.net>
Date: Wed, 21 Apr 2010 22:50:15 -0700 (PDT)

> Jiri please respin your patch with the argument order
> reversed so that we can make the inexpensive check before
> the expensive one.

Nevermind, I see you posted an updated version already,
which I've applied, thanks!
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