ipv6/udp: use sticky pktinfo egress ifindex on connect()

Currently, the egress interface index specified via IPV6_PKTINFO
is ignored by __ip6_datagram_connect(), so that RFC 3542 section 6.7
can be subverted when the user space application calls connect()
before sendmsg().
Fix it by initializing properly flowi6_oif in connect() before
performing the route lookup.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index 517c55b01ba8..428162155280 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -162,6 +162,9 @@ ipv4_connected:
         fl6.fl6_dport = inet->inet_dport;
         fl6.fl6_sport = inet->inet_sport;
 
+        if (!fl6.flowi6_oif)
+                fl6.flowi6_oif = np->sticky_pktinfo.ipi6_ifindex;
+
         if (!fl6.flowi6_oif && (addr_type&IPV6_ADDR_MULTICAST))
                 fl6.flowi6_oif = np->mcast_oif;