openvswitch: fix vport packet length check.

Upstream commit:
    commit 46e371f0e78a82186a83cbcb4f4b8850417c7dd5
    Author: William Tu <u9012063@gmail.com>
    Date:   Wed Mar 7 15:38:48 2018 -0800

    openvswitch: fix vport packet length check.

    When sending a packet to a tunnel device, the dev's hard_header_len
    could be larger than the skb->len in function packet_length().
    In the case of ip6gretap/erspan, hard_header_len = LL_MAX_HEADER + t_hlen,
    which is around 180, and an ARP packet sent to this tunnel has
    skb->len = 42.  This causes the 'unsign int length' to become super
    large because it is negative value, causing the later ovs_vport_send
    to drop it due to over-mtu size.  The patch fixes it by setting it to 0.

    Signed-off-by: William Tu <u9012063@gmail.com>
    Acked-by: Pravin B Shelar <pshelar@ovn.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: William Tu <u9012063@gmail.com>
Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: William Tu <u9012063@gmail.com>

diff --git a/datapath/vport.c b/datapath/vport.c
index f4131be2c038efd51f1898c1ae12b96eaac9be7d..184c8593e3fd4bcbf0d42c0a9e68e8c7d24ff98f 100644 (file)
--- a/datapath/vport.c
+++ b/datapath/vport.c
@@ -520,10 +520,10 @@ 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)
+static int packet_length(const struct sk_buff *skb,
+                        struct net_device *dev)
 {
-       unsigned int length = skb->len - dev->hard_header_len;
+       int length = skb->len - dev->hard_header_len;
 
        if (!skb_vlan_tag_present(skb) &&
            eth_type_vlan(skb->protocol))
@@ -534,7 +534,7 @@ static unsigned int packet_length(const struct sk_buff *skb,
         * account for 802.1ad. e.g. is_skb_forwardable().
         */
 
-       return length;
+       return length > 0 ? length: 0;
 }
 
 void ovs_vport_send(struct vport *vport, struct sk_buff *skb, u8 mac_proto)