Re: [PATCH net-next] net/sched: em_meta: Fix 'meta vlan' to correctly recognize zero VID frames

[David Miller]

From: Shmulik Ladkani 
Date: Fri, 21 Oct 2016 00:18:08 +0300

> 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 

Applied, thanks.

[PATCH net-next] net/sched: em_meta: Fix 'meta vlan' to correctly recognize zero VID frames

[Shmulik Ladkani]

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 
Cc: Eric Dumazet 
Cc: Stephen Hemminger 
---
 net/sched/em_meta.c | 9 +
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/sched/em_meta.c b/net/sched/em_meta.c
index a309a07ccb..41c80b6c39 100644
--- 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 = skb_vlan_tag_get(skb);
-   if (!tag && __vlan_get_tag(skb, ))
-   *err = -1;
-   else
+   if (skb_vlan_tag_present(skb))
+   dst->value = skb_vlan_tag_get(skb);
+   else if (!__vlan_get_tag(skb, ))
dst->value = tag;
+   else
+   *err = -1;
 }
 
 
-- 
2.7.4