Commit 21d1196a authored Jul 15, 2013 by Eric Dumazet Committed by David S. Miller Jul 16, 2013

ipv4: set transport header earlier



commit 45f00f99 ("ipv4: tcp: clean up tcp_v4_early_demux()") added a
performance regression for non GRO traffic, basically disabling
IP early demux.

IPv6 stack resets transport header in ip6_rcv() before calling
IP early demux in ip6_rcv_finish(), while IPv4 does this only in
ip_local_deliver_finish(), _after_ IP early demux.

GRO traffic happened to enable IP early demux because transport header
is also set in inet_gro_receive()

Instead of reverting the faulty commit, we can make IPv4/IPv6 behave the
same : transport_header should be set in ip_rcv() instead of
ip_local_deliver_finish()

ip_local_deliver_finish() can also use skb_network_header_len() which is
faster than ip_hdrlen()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 9a0f06fe

net/ipv4/ip_input.c

+3 −4

Original line number	Diff line number	Diff line
		@@ -190,10 +190,7 @@ static int ip_local_deliver_finish(struct sk_buff *skb)
		{
		struct net *net = dev_net(skb->dev);

		__skb_pull(skb, ip_hdrlen(skb));

		/* Point into the IP datagram, just past the header. */
		skb_reset_transport_header(skb);
		__skb_pull(skb, skb_network_header_len(skb));

		rcu_read_lock();
		{
		@@ -437,6 +434,8 @@ int ip_rcv(struct sk_buff skb, struct net_device dev, struct packet_type *pt,
		goto drop;
		}

		skb->transport_header = skb->network_header + iph->ihl*4;

		/* Remove any debris in the socket control block */
		memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));

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