netdev - [RFC PATCH 2/2] ipv6: don't use routing cache for inexact matchings

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Message-Id: <DFD1E072-5112-4FFD-9BD7-525A2CE2D34B@telecom-bretagne.eu>
Date:	Fri, 1 Nov 2013 18:21:41 +0100
From:	Emmanuel Thierry <emmanuel.thierry@...ecom-bretagne.eu>
To:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Cc:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: [RFC PATCH 2/2] ipv6: don't use routing cache for inexact matchings

On route selection, make the cache to be used only when the flow
output interface corresponds to the next hop interface. This
fixes problems for IPv6 hosts in multi-interfaces setup.

When a packet is sent through an interface, the RTF_CACHE entry
is created based on a specific flow information (e.g. with
fl6->flowi6_oif set to a specific value). If another packet is
sent with a different flow information than the first one, the
RTF_CACHE entry is used regardless of flow information, even if
this information would make the route selection algorithm to
select a different route.

By ignoring RTF_CACHE entries for which rt6_check_dev() fails,
we ensure consistency of the route selection algorithm.

Signed-off-by: Emmanuel Thierry <emmanuel.thierry@...ecom-bretagne.eu>
---
 net/ipv6/route.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f54e3a1..65ce3d9 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -595,7 +595,8 @@ static int rt6_score_route(struct rt6_info *rt, int oif,
 	int m;

 	m = rt6_check_dev(rt, oif);
-	if (!m && (strict & RT6_LOOKUP_F_IFACE))
+	if (!m &&
+	    ((strict & RT6_LOOKUP_F_IFACE) || (rt->rt6i_flags & RTF_CACHE)))
 		return RT6_NUD_FAIL_HARD;
 #ifdef CONFIG_IPV6_ROUTER_PREF
 	m |= IPV6_DECODE_PREF(IPV6_EXTRACT_PREF(rt->rt6i_flags)) << 2;
-- 
1.7.9.5
--
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