ipv6: refactor ip6_finish_output for GSO handling

Separate GSO and non-GSO packets handling to make the logic cleaner. For
GSO packets, frag_max_size check can be omitted because it is only
useful for packets defragmented by netfilter hooks. Both local output
and GRO logic won't produce GSO packets when defragment is needed. This
also mirrors what IPv4 side code is doing.

Suggested-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Yan Zhai <yan@cloudflare.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/0e1d4599f858e2becff5c4fe0b5f843236bc3fe8.1698156966.git.yan@cloudflare.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 86efd901ee5a2bcbc4ee9822517401ba7aec9610..4010dd97aaf805072ae9c21538d1c38ed575ebf5 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -172,6 +172,16 @@ ip6_finish_output_gso_slowpath_drop(struct net *net, struct sock *sk,
        return ret;
 }
 
+static int ip6_finish_output_gso(struct net *net, struct sock *sk,
+                                struct sk_buff *skb, unsigned int mtu)
+{
+       if (!(IP6CB(skb)->flags & IP6SKB_FAKEJUMBO) &&
+           !skb_gso_validate_network_len(skb, mtu))
+               return ip6_finish_output_gso_slowpath_drop(net, sk, skb, mtu);
+
+       return ip6_finish_output2(net, sk, skb);
+}
+
 static int __ip6_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
        unsigned int mtu;
@@ -185,16 +195,14 @@ static int __ip6_finish_output(struct net *net, struct sock *sk, struct sk_buff
 #endif
 
        mtu = ip6_skb_dst_mtu(skb);
-       if (skb_is_gso(skb) &&
-           !(IP6CB(skb)->flags & IP6SKB_FAKEJUMBO) &&
-           !skb_gso_validate_network_len(skb, mtu))
-               return ip6_finish_output_gso_slowpath_drop(net, sk, skb, mtu);
+       if (skb_is_gso(skb))
+               return ip6_finish_output_gso(net, sk, skb, mtu);
 
-       if ((skb->len > mtu && !skb_is_gso(skb)) ||
+       if (skb->len > mtu ||
            (IP6CB(skb)->frag_max_size && skb->len > IP6CB(skb)->frag_max_size))
                return ip6_fragment(net, sk, skb, ip6_finish_output2);
-       else
-               return ip6_finish_output2(net, sk, skb);
+
+       return ip6_finish_output2(net, sk, skb);
 }
 
 static int ip6_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)