[ovs-dev] [PATCH 26/41] openvswitch: fix vport packet length check.

[Greg Rose]

From: William Tu <u9012063 at gmail.com>

Upstream commit:
    commit 46e371f0e78a82186a83cbcb4f4b8850417c7dd5
    Author: William Tu <u9012063 at 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 at gmail.com>
    Acked-by: Pravin B Shelar <pshelar at ovn.org>
    Signed-off-by: David S. Miller <davem at davemloft.net>

Cc: William Tu <u9012063 at gmail.com>
Signed-off-by: Greg Rose <gvrose8192 at gmail.com>
---
 datapath/vport.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/datapath/vport.c b/datapath/vport.c
index f4131be..184c859 100644
--- 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)
-- 
1.8.3.1