ipv6: gso: make ipv6_gso_segment() stackable

In order to support GSO on SIT tunnels, 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, 17 insertions, 6 deletions

diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
index 5c2fc1d04196..f9b33d82bb9d 100644
--- a/net/ipv6/ip6_offload.c
+++ b/net/ipv6/ip6_offload.c
@@ -90,6 +90,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
         u8 *prevhdr;
         int offset = 0;
         bool tunnel;
+        int nhoff;
 
         if (unlikely(skb_shinfo(skb)->gso_type &
                      ~(SKB_GSO_UDP |
@@ -103,10 +104,16 @@ static struct sk_buff *ipv6_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(*ipv6h))))
                 goto out;
 
-        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 += sizeof(*ipv6h);
+
         ipv6h = ipv6_hdr(skb);
         __skb_pull(skb, sizeof(*ipv6h));
         segs = ERR_PTR(-EPROTONOSUPPORT);
@@ -123,13 +130,17 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
                 goto out;
 
         for (skb = segs; skb; skb = skb->next) {
-                ipv6h = ipv6_hdr(skb);
-                ipv6h->payload_len = htons(skb->len - skb->mac_len -
-                                           sizeof(*ipv6h));
+                ipv6h = (struct ipv6hdr *)(skb_mac_header(skb) + nhoff);
+                ipv6h->payload_len = htons(skb->len - nhoff - sizeof(*ipv6h));
+                if (tunnel) {
+                        skb_reset_inner_headers(skb);
+                        skb->encapsulation = 1;
+                }
+                skb->network_header = (u8 *)ipv6h - skb->head;
+
                 if (!tunnel && proto == IPPROTO_UDP) {
                         unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
-                        fptr = (struct frag_hdr *)(skb_network_header(skb) +
-                                unfrag_ip6hlen);
+                        fptr = (struct frag_hdr *)((u8 *)ipv6h + unfrag_ip6hlen);
                         fptr->frag_off = htons(offset);
                         if (skb->next != NULL)
                                 fptr->frag_off |= htons(IP6_MF);