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net: Do not drop to make_route if oif is l3mdev

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Commit deaa0a6a930 ("net: Lookup actual route when oif is VRF device")
exposed a bug in __ip_route_output_key_hash for VRF devices: on FIB lookup
failure if the oif is specified the current logic drops to make_route on
the assumption that the route tables are wrong. For VRF/L3 master devices
this leads to wrong dst entries and route lookups. For example:
    $ ip route ls table vrf-red
    unreachable default
    broadcast 10.2.1.0 dev eth1  proto kernel  scope link  src 10.2.1.2
    10.2.1.0/24 dev eth1  proto kernel  scope link  src 10.2.1.2
    local 10.2.1.2 dev eth1  proto kernel  scope host  src 10.2.1.2
    broadcast 10.2.1.255 dev eth1  proto kernel  scope link  src 10.2.1.2

    $ ip route get oif vrf-red 1.1.1.1
    1.1.1.1 dev vrf-red  src 10.0.0.2
        cache

With this patch:
    $  ip route get oif vrf-red 1.1.1.1
    RTNETLINK answers: No route to host

which is the correct response based on the default route

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Ahern 2015-10-07 08:40:13 -07:00 committed by David S. Miller
parent cfc81b5038
commit 28335a7445
1 changed files with 2 additions and 1 deletions
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3
net/ipv4/route.c
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@ -2196,7 +2196,8 @@ struct rtable *__ip_route_output_key_hash(struct net *net, struct flowi4 *fl4,
if (err) {
res.fi = NULL;
res.table = NULL;
if (fl4->flowi4_oif) {
if (fl4->flowi4_oif &&
!netif_index_is_l3_master(net, fl4->flowi4_oif)) {
/* Apparently, routing tables are wrong. Assume,
that the destination is on link.