ip_gre: increase inner ip header ID during segmentation

According to the previous discussion [1] on netdev list, DaveM insists
we should increase the IP header ID for each segmented packets.
This patch fixes it.

Cc: Pravin B Shelar <pshelar@nicira.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>

1. http://marc.info/?t=136384172700001&r=1&w=2
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 1 deletions

diff --git a/net/ipv4/gre.c b/net/ipv4/gre.c
index 7a4c710c4cdd..e20631cb4185 100644
--- a/net/ipv4/gre.c
+++ b/net/ipv4/gre.c
@@ -125,8 +125,9 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
         netdev_features_t enc_features;
         int ghl = GRE_HEADER_SECTION;
         struct gre_base_hdr *greh;
+        struct iphdr *iph;
         int mac_len = skb->mac_len;
-        int tnl_hlen;
+        int tnl_hlen, id;
         bool csum;
 
         if (unlikely(skb_shinfo(skb)->gso_type &
@@ -170,6 +171,8 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
         skb_set_network_header(skb, skb_inner_network_offset(skb));
         skb->mac_len = skb_inner_network_offset(skb);
 
+        iph = ip_hdr(skb);
+        id = ntohs(iph->id);
         /* segment inner packet. */
         enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
         segs = skb_mac_gso_segment(skb, enc_features);
@@ -179,6 +182,8 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
         skb = segs;
         tnl_hlen = skb_tnl_header_len(skb);
         do {
+                iph = (struct iphdr *)skb->data;
+                iph->id = htons(id++);
                 __skb_push(skb, ghl);
                 if (csum) {
                         __be32 *pcsum;