ipv6: Fix redirect with VRF [Linux 5.2]

ipv6: Fix redirect with VRF [Linux 5.2]

This Linux kernel change "ipv6: Fix redirect with VRF" is included in the Linux 5.2 release. This change is authored by David Ahern <dsahern [at] gmail.com> on Wed May 22 15:12:18 2019 -0700. The commit for this change in Linux stable tree is 31680ac (patch).

ipv6: Fix redirect with VRF

IPv6 redirect is broken for VRF. __ip6_route_redirect walks the FIB
entries looking for an exact match on ifindex. With VRF the flowi6_oif
is updated by l3mdev_update_flow to the l3mdev index and the
FLOWI_FLAG_SKIP_NH_OIF set in the flags to tell the lookup to skip the
device match. For redirects the device match is requires so use that
flag to know when the oif needs to be reset to the skb device index.

Fixes: ca254490c8df ("net: Add VRF support to IPv6 stack")
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

There are 6 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 net/ipv6/route.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 7a014ca..848e944 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2512,6 +2512,12 @@ static struct rt6_info *__ip6_route_redirect(struct net *net,
    struct fib6_info *rt;
    struct fib6_node *fn;

+   /* l3mdev_update_flow overrides oif if the device is enslaved; in
+    * this case we must match on the real ingress device, so reset it
+    */
+   if (fl6->flowi6_flags & FLOWI_FLAG_SKIP_NH_OIF)
+       fl6->flowi6_oif = skb->dev->ifindex;
    /* Get the "current" route for this destination and
     * check if the redirect has come from appropriate router.

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