IP_GRE: Fix IP-Identification.

GRE-GSO generates ip fragments with id 0,2,3,4... for every
GSO packet, which is not correct. Following patch fixes it
by setting ip-header id unique id of fragments are allowed.
As Eric Dumazet suggested it is optimized by using inner ip-header
whenever inner packet is ipv4.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 0 deletions

diff --git a/include/net/ipip.h b/include/net/ipip.h
index 21947cf4fa46..fd19625ff99d 100644
--- a/include/net/ipip.h
+++ b/include/net/ipip.h
@@ -71,4 +71,21 @@ static inline void iptunnel_xmit(struct sk_buff *skb, struct net_device *dev)
         }
 }
 
+static inline void tunnel_ip_select_ident(struct sk_buff *skb,
+                                          const struct iphdr  *old_iph,
+                                          struct dst_entry *dst)
+{
+        struct iphdr *iph = ip_hdr(skb);
+
+        if (iph->frag_off & htons(IP_DF))
+                iph->id = 0;
+        else {
+                /* Use inner packet iph-id if possible. */
+                if (skb->protocol == htons(ETH_P_IP) && old_iph->id)
+                        iph->id = old_iph->id;
+                else
+                        __ip_select_ident(iph, dst,
+                                          (skb_shinfo(skb)->gso_segs ?: 1) - 1);
+        }
+}
 #endif