net: skb_scrub_packet(): Scrub offload_fwd_mark

When a packet is trapped and the corresponding SKB marked as
already-forwarded, it retains this marking even after it is forwarded
across veth links into another bridge. There, since it ingresses the
bridge over veth, which doesn't have offload_fwd_mark, it triggers a
warning in nbp_switchdev_frame_mark().

Then nbp_switchdev_allowed_egress() decides not to allow egress from
this bridge through another veth, because the SKB is already marked, and
the mark (of 0) of course matches. Thus the packet is incorrectly
blocked.

Solve by resetting offload_fwd_mark() in skb_scrub_packet(). That
function is called from tunnels and also from veth, and thus catches the
cases where traffic is forwarded between bridges and transformed in a
way that invalidates the marking.

Fixes: 6bc506b4fb06 ("bridge: switchdev: Add forward mark support for stacked devices")
Fixes: abf4bb6b63d0 ("skbuff: Add the offload_mr_fwd_mark field")
Signed-off-by: Petr Machata <petrm@mellanox.com>
Suggested-by: Ido Schimmel <idosch@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b4ee5c8b928f07879b3c7ed08ed5e9b67b08fcb4..a8217e221e1954871f15d6ba160538939d9b53ff 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4854,6 +4854,11 @@ void skb_scrub_packet(struct sk_buff *skb, bool xnet)
        nf_reset(skb);
        nf_reset_trace(skb);
 
+#ifdef CONFIG_NET_SWITCHDEV
+       skb->offload_fwd_mark = 0;
+       skb->offload_mr_fwd_mark = 0;
+#endif
+
        if (!xnet)
                return;