linux-kernel - [PATCH 3.10 140/250] net/sched: em_meta: Fix 'meta vlan' to correctly recognize zero VID frames

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Message-Id: <1496876436-32402-141-git-send-email-w@1wt.eu>
Date:   Thu,  8 Jun 2017 00:58:46 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Shmulik Ladkani <shmulik.ladkani@...il.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        "David S . Miller" <davem@...emloft.net>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 140/250] net/sched: em_meta: Fix 'meta vlan' to correctly recognize zero VID frames

From: Shmulik Ladkani <shmulik.ladkani@...il.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@...il.com>
Cc: Eric Dumazet <eric.dumazet@...il.com>
Cc: Stephen Hemminger <stephen@...workplumber.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Willy Tarreau <w@....eu>
---
 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 7c3de6f..eba9d1e 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 = 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;
 }
 
 
-- 
2.8.0.rc2.1.gbe9624a