net: gro: parse ipv6 ext headers without frag0 invalidation

The existing code always pulls the IPv6 header and sets the transport
offset initially. Then optionally again pulls any extension headers in
ipv6_gso_pull_exthdrs and sets the transport offset again on return from
that call. skb->data is set at the start of the first extension header
before calling ipv6_gso_pull_exthdrs, and must disable the frag0
optimization because that function uses pskb_may_pull/pskb_pull instead of
skb_gro_ helpers. It sets the GRO offset to the TCP header with
skb_gro_pull and sets the transport header. Then returns skb->data to its
position before this block.

This commit introduces a new helper function - ipv6_gro_pull_exthdrs -
which is used in ipv6_gro_receive to pull ipv6 ext headers instead of
ipv6_gso_pull_exthdrs. Thus, there is no modification of skb->data, all
operations use skb_gro_* helpers, and the frag0 fast path can be taken for
IPv6 packets with ext headers.

Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/504130f6-b56c-4dcc-882c-97942c59f5b7@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
index 0e0b5fed0995254d6966d0d592a4d4d53e11fa5e..cca64c7809bee9a0360cbfab6a645d3f8d2ffea3 100644 (file)
--- a/net/ipv6/ip6_offload.c
+++ b/net/ipv6/ip6_offload.c
@@ -37,6 +37,40 @@
                INDIRECT_CALL_L4(cb, f2, f1, head, skb);        \
 })
 
+static int ipv6_gro_pull_exthdrs(struct sk_buff *skb, int off, int proto)
+{
+       const struct net_offload *ops = NULL;
+       struct ipv6_opt_hdr *opth;
+
+       for (;;) {
+               int len;
+
+               ops = rcu_dereference(inet6_offloads[proto]);
+
+               if (unlikely(!ops))
+                       break;
+
+               if (!(ops->flags & INET6_PROTO_GSO_EXTHDR))
+                       break;
+
+               opth = skb_gro_header(skb, off + sizeof(*opth), off);
+               if (unlikely(!opth))
+                       break;
+
+               len = ipv6_optlen(opth);
+
+               opth = skb_gro_header(skb, off + len, off);
+               if (unlikely(!opth))
+                       break;
+               proto = opth->nexthdr;
+
+               off += len;
+       }
+
+       skb_gro_pull(skb, off - skb_network_offset(skb));
+       return proto;
+}
+
 static int ipv6_gso_pull_exthdrs(struct sk_buff *skb, int proto)
 {
        const struct net_offload *ops = NULL;
@@ -203,28 +237,25 @@ INDIRECT_CALLABLE_SCOPE struct sk_buff *ipv6_gro_receive(struct list_head *head,
                goto out;
 
        skb_set_network_header(skb, off);
-       skb_gro_pull(skb, sizeof(*iph));
-       skb_set_transport_header(skb, skb_gro_offset(skb));
 
-       flush += ntohs(iph->payload_len) != skb_gro_len(skb);
+       flush += ntohs(iph->payload_len) != skb->len - hlen;
 
        proto = iph->nexthdr;
        ops = rcu_dereference(inet6_offloads[proto]);
        if (!ops || !ops->callbacks.gro_receive) {
-               pskb_pull(skb, skb_gro_offset(skb));
-               skb_gro_frag0_invalidate(skb);
-               proto = ipv6_gso_pull_exthdrs(skb, proto);
-               skb_gro_pull(skb, -skb_transport_offset(skb));
-               skb_reset_transport_header(skb);
-               __skb_push(skb, skb_gro_offset(skb));
+               proto = ipv6_gro_pull_exthdrs(skb, hlen, proto);
 
                ops = rcu_dereference(inet6_offloads[proto]);
                if (!ops || !ops->callbacks.gro_receive)
                        goto out;
 
-               iph = ipv6_hdr(skb);
+               iph = skb_gro_network_header(skb);
+       } else {
+               skb_gro_pull(skb, sizeof(*iph));
        }
 
+       skb_set_transport_header(skb, skb_gro_offset(skb));
+
        NAPI_GRO_CB(skb)->proto = proto;
 
        flush--;