ipv4: gso: make inet_gso_segment() stackable

In order to support GSO on IPIP, we need to make
inet_gso_segment() stackable.

It should not assume network header starts right after mac
header.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 7 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 4f8cd4fc451d..5783ab5b5ef8 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1273,16 +1273,17 @@ out:
 }
 
 static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
-        netdev_features_t features)
+                                        netdev_features_t features)
 {
         struct sk_buff *segs = ERR_PTR(-EINVAL);
         const struct net_offload *ops;
+        unsigned int offset = 0;
         struct iphdr *iph;
+        bool tunnel;
         int proto;
+        int nhoff;
         int ihl;
         int id;
-        unsigned int offset = 0;
-        bool tunnel;
 
         if (unlikely(skb_shinfo(skb)->gso_type &
                      ~(SKB_GSO_TCPV4 |
@@ -1296,6 +1297,8 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
                        0)))
                 goto out;
 
+        skb_reset_network_header(skb);
+        nhoff = skb_network_header(skb) - skb_mac_header(skb);
         if (unlikely(!pskb_may_pull(skb, sizeof(*iph))))
                 goto out;
 
@@ -1312,7 +1315,10 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
                 goto out;
         __skb_pull(skb, ihl);
 
-        tunnel = !!skb->encapsulation;
+        tunnel = SKB_GSO_CB(skb)->encap_level > 0;
+        if (tunnel)
+                features = skb->dev->hw_enc_features & netif_skb_features(skb);
+        SKB_GSO_CB(skb)->encap_level += ihl;
 
         skb_reset_transport_header(skb);
 
@@ -1327,18 +1333,23 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 
         skb = segs;
         do {
-                iph = ip_hdr(skb);
+                iph = (struct iphdr *)(skb_mac_header(skb) + nhoff);
                 if (!tunnel && proto == IPPROTO_UDP) {
                         iph->id = htons(id);
                         iph->frag_off = htons(offset >> 3);
                         if (skb->next != NULL)
                                 iph->frag_off |= htons(IP_MF);
-                        offset += (skb->len - skb->mac_len - iph->ihl * 4);
+                        offset += skb->len - nhoff - ihl;
                 } else  {
                         iph->id = htons(id++);
                 }
-                iph->tot_len = htons(skb->len - skb->mac_len);
+                iph->tot_len = htons(skb->len - nhoff);
                 ip_send_check(iph);
+                if (tunnel) {
+                        skb_reset_inner_headers(skb);
+                        skb->encapsulation = 1;
+                }
+                skb->network_header = (u8 *)iph - skb->head;
         } while ((skb = skb->next));
 
 out: