inet: restore gso for vxlan

Alexei reported a performance regression on vxlan, caused
by commit 3347c9602955 "ipv4: gso: make inet_gso_segment() stackable"

GSO vxlan packets were not properly segmented, adding IP fragments
while they were not expected.

Rename 'bool tunnel' to 'bool encap', and add a new boolean
to express the fact that UDP should be fragmented.
This fragmentation is triggered by skb->encapsulation being set.

Remove a "skb->encapsulation = 1" added in above commit,
as its not needed, as frags inherit skb->frag from original
GSO skb.

Reported-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 8 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index f4a159e705c0..09d78d4a3cff 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1251,8 +1251,8 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
         struct sk_buff *segs = ERR_PTR(-EINVAL);
         const struct net_offload *ops;
         unsigned int offset = 0;
+        bool udpfrag, encap;
         struct iphdr *iph;
-        bool tunnel;
         int proto;
         int nhoff;
         int ihl;
@@ -1290,8 +1290,8 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
                 goto out;
         __skb_pull(skb, ihl);
 
-        tunnel = SKB_GSO_CB(skb)->encap_level > 0;
-        if (tunnel)
+        encap = SKB_GSO_CB(skb)->encap_level > 0;
+        if (encap)
                 features = skb->dev->hw_enc_features & netif_skb_features(skb);
         SKB_GSO_CB(skb)->encap_level += ihl;
 
@@ -1306,24 +1306,23 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
         if (IS_ERR_OR_NULL(segs))
                 goto out;
 
+        udpfrag = !!skb->encapsulation && proto == IPPROTO_UDP;
         skb = segs;
         do {
                 iph = (struct iphdr *)(skb_mac_header(skb) + nhoff);
-                if (!tunnel && proto == IPPROTO_UDP) {
+                if (udpfrag) {
                         iph->id = htons(id);
                         iph->frag_off = htons(offset >> 3);
                         if (skb->next != NULL)
                                 iph->frag_off |= htons(IP_MF);
                         offset += skb->len - nhoff - ihl;
-                } else  {
+                } else {
                         iph->id = htons(id++);
                 }
                 iph->tot_len = htons(skb->len - nhoff);
                 ip_send_check(iph);
-                if (tunnel) {
+                if (encap)
                         skb_reset_inner_headers(skb);
-                        skb->encapsulation = 1;
-                }
                 skb->network_header = (u8 *)iph - skb->head;
         } while ((skb = skb->next));