Newly created flows don't have flowi6_oif set (at least if the
associated socket is not interface-bound). This leads to a mismatch in
__xfrm6_selector_match() for policies which specify an interface in the
selector (sel->ifindex != 0).

Backtracing shows this happens in code-paths originating from e.g.
ip6_datagram_connect(), rawv6_sendmsg() or tcp_v6_connect(). (UDP was
not tested for.)

In summary, this patch fixes policy matching on outgoing interface for
locally generated packets.

Signed-off-by: Phil Sutter <p...@nwl.cc>
---
 net/ipv6/ip6_output.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index d5f7716..c5fc852 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1023,6 +1023,8 @@ struct dst_entry *ip6_dst_lookup_flow(struct sock *sk, 
struct flowi6 *fl6,
                return ERR_PTR(err);
        if (final_dst)
                fl6->daddr = *final_dst;
+       if (!fl6->flowi6_oif)
+               fl6->flowi6_oif = dst->dev->ifindex;
 
        return xfrm_lookup_route(sock_net(sk), dst, flowi6_to_flowi(fl6), sk, 
0);
 }
-- 
2.1.2

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