[PATCH 3.16 008/370] net/sched: em_meta: Fix 'meta vlan' to correctly recognize zero VID frames

Ben Hutchings
2017-03-10T14:19:13Z

From: Shmulik Ladkani <shmulik.ladkani@gmail.com>

commit d65f2fa680d6f91438461df54c83a331b3a631c9 upstream.

META_COLLECTOR int_vlan_tag() assumes that if the accel tag (vlan_tci)
is zero, then no vlan accel tag is present.

This is incorrect for zero VID vlan accel packets, making the following
match fail:
tc filter add ... basic match 'meta(vlan mask 0xfff eq 0)' ...

Apparently 'int_vlan_tag' was implemented prior VLAN_TAG_PRESENT was
introduced in 05423b2 "vlan: allow null VLAN ID to be used"
(and at time introduced, the 'vlan_tx_tag_get' call in em_meta was not
adapted).

Fix, testing skb_vlan_tag_present instead of testing skb_vlan_tag_get's
value.

Fixes: 05423b2413 ("vlan: allow null VLAN ID to be used")
Fixes: 1a31f2042e ("netsched: Allow meta match on vlan tag on receive")

Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16: s/skb_vlan_tag/vlan_tx_tag/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/sched/em_meta.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

--- a/net/sched/em_meta.c
+++ b/net/sched/em_meta.c
@@ -176,11 +176,12 @@ META_COLLECTOR(int_vlan_tag)
{
unsigned short tag;

- tag = vlan_tx_tag_get(skb);
- if (!tag && __vlan_get_tag(skb, &tag))
- *err = -1;
- else
+ if (vlan_tx_tag_present(skb))
+ dst->value = vlan_tx_tag_get(skb);
+ else if (!__vlan_get_tag(skb, &tag))
dst->value = tag;
+ else
+ *err = -1;
}