netdev - [PATCH net-next v2 3/3] openvswitch: fix vlan subtraction from packet length

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Message-Id: <431c9af67a1012ce7ba8109b533e463dadfe5ab5.1475672569.git.jbenc@redhat.com>
Date:   Wed,  5 Oct 2016 15:07:28 +0200
From:   Jiri Benc <jbenc@...hat.com>
To:     netdev@...r.kernel.org
Cc:     pravin shelar <pshelar@....org>, Eric Garver <e@...g.me>
Subject: [PATCH net-next v2 3/3] openvswitch: fix vlan subtraction from packet length

When the packet has its vlan tag in skb->vlan_tci, the length of the VLAN
header is not counted in skb->len. It doesn't make sense to subtract it.

In addition, to honor the comment below the code, the VLAN header length
should not be subtracted if there's a vlan tag in skb->vlan_tci. This leads
to the code simply subtracting the Ethernet header length.

Signed-off-by: Jiri Benc <jbenc@...hat.com>
---
 net/openvswitch/vport.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index 8f198437c724..210bafc09bd8 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -483,17 +483,13 @@ EXPORT_SYMBOL_GPL(ovs_vport_deferred_free);
 
 static unsigned int packet_length(const struct sk_buff *skb)
 {
-	unsigned int length = skb->len - ETH_HLEN;
-
-	if (skb_vlan_tagged(skb))
-		length -= VLAN_HLEN;
-
 	/* Don't subtract for multiple VLAN tags. Most (all?) drivers allow
 	 * (ETH_LEN + VLAN_HLEN) in addition to the mtu value, but almost none
 	 * account for 802.1ad. e.g. is_skb_forwardable().
+	 * Note that the first VLAN tag is always in skb->vlan_tci, thus not
+	 * accounted for in skb->len.
 	 */
-
-	return length;
+	return skb->len - ETH_HLEN;
 }
 
 void ovs_vport_send(struct vport *vport, struct sk_buff *skb)
-- 
1.8.3.1