[ 3.8.y.z extended stable ] Patch "ipv4: set transport header earlier" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ipv4: set transport header earlier

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.6.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 862fdc8f31a7d3cddb1027135600da36048fdebf Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet at google.com>
Date: Mon, 15 Jul 2013 20:03:19 -0700
Subject: ipv4: set transport header earlier

[ Upstream commit 21d1196a35f5686c4323e42a62fdb4b23b0ab4a3 ]

commit 45f00f99d6e ("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 at google.com>
Cc: Neal Cardwell <ncardwell at google.com>
Cc: Tom Herbert <therbert at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/ipv4/ip_input.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index f1395a6..e1e5a6a 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -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();
 	{
@@ -442,6 +439,8 @@ 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));

--
1.8.1.2