[PATCH v3 net-next 2/3] openvswitch: Use is_skb_forwardable() for length check.

[Jarno Rajahalme]

Use is_skb_forwardable() instead of an explicit length check.  This
gets around the apparent MTU check failure in OVS test cases when
skb->protocol is not properly set in case of non-accelerated VLAN
skbs.

Suggested-by: Pravin Shelar <pshe...@ovn.org>
Fixes: 5108bbaddc ("openvswitch: add processing of L3 packets")
Signed-off-by: Jarno Rajahalme <ja...@ovn.org>
---
v3: New patch suggested by Pravin.

net/openvswitch/vport.c | 38 ++++++++++++++------------------------
 1 file changed, 14 insertions(+), 24 deletions(-)

diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index b6c8524..076b39f 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -464,27 +464,8 @@ int ovs_vport_receive(struct vport *vport, struct sk_buff 
*skb,
        return 0;
 }
 
-static unsigned int packet_length(const struct sk_buff *skb,
-                                 struct net_device *dev)
-{
-       unsigned int length = skb->len - dev->hard_header_len;
-
-       if (!skb_vlan_tag_present(skb) &&
-           eth_type_vlan(skb->protocol))
-               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().
-        */
-
-       return length;
-}
-
 void ovs_vport_send(struct vport *vport, struct sk_buff *skb, u8 mac_proto)
 {
-       int mtu = vport->dev->mtu;
-
        switch (vport->dev->type) {
        case ARPHRD_NONE:
                if (mac_proto == MAC_PROTO_ETHERNET) {
@@ -504,11 +485,20 @@ void ovs_vport_send(struct vport *vport, struct sk_buff 
*skb, u8 mac_proto)
                goto drop;
        }
 
-       if (unlikely(packet_length(skb, vport->dev) > mtu &&
-                    !skb_is_gso(skb))) {
-               net_warn_ratelimited("%s: dropped over-mtu packet: %d > %d\n",
-                                    vport->dev->name,
-                                    packet_length(skb, vport->dev), mtu);
+       if (unlikely(!is_skb_forwardable(vport->dev, skb))) {
+               /* Log only if the device is up. */
+               if (vport->dev->flags & IFF_UP) {
+                       unsigned int length = skb->len
+                               - vport->dev->hard_header_len;
+
+                       if (!skb_vlan_tag_present(skb)
+                           && eth_type_vlan(skb->protocol))
+                               length -= VLAN_HLEN;
+
+                       net_warn_ratelimited("%s: dropped over-mtu packet %d > 
%d\n",
+                                            vport->dev->name, length,
+                                            vport->dev->mtu);
+               }
                vport->dev->stats.tx_errors++;
                goto drop;
        }
-- 
2.1.4