ip_gre: make ipgre_tunnel_xmit() not parse network header as IP unconditionally

ipgre_tunnel_xmit() parses network header as IP unconditionally.
But transmitting packets are not always IP packet. For example such packet
can be sent by packet socket with sockaddr_ll.sll_protocol set.
So make the function check if skb->protocol is IP.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index a85ae2f7a21c..8fcf0ed76548 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -760,7 +760,10 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
 
         if (dev->header_ops && dev->type == ARPHRD_IPGRE) {
                 gre_hlen = 0;
-                tiph = (const struct iphdr *)skb->data;
+                if (skb->protocol == htons(ETH_P_IP))
+                        tiph = (const struct iphdr *)skb->data;
+                else
+                        tiph = &tunnel->parms.iph;
         } else {
                 gre_hlen = tunnel->hlen;
                 tiph = &tunnel->parms.iph;