[3.11.y.z extended stable] Patch "net: ipv4: ip_forward: fix inverted local_df test" has been added to staging queue

[Luis Henriques]

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

    net: ipv4: ip_forward: fix inverted local_df test

to the linux-3.11.y-queue branch of the 3.11.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-3.11.y-queue

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

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 2ec407c17b78e36eaf516fced73c067334d1dc66 Mon Sep 17 00:00:00 2001
From: Florian Westphal <fw at strlen.de>
Date: Sun, 4 May 2014 23:24:31 +0200
Subject: net: ipv4: ip_forward: fix inverted local_df test

commit ca6c5d4ad216d5942ae544bbf02503041bd802aa upstream.

local_df means 'ignore DF bit if set', so if its set we're
allowed to perform ip fragmentation.

This wasn't noticed earlier because the output path also drops such skbs
(and emits needed icmp error) and because netfilter ip defrag did not
set local_df until couple of days ago.

Only difference is that DF-packets-larger-than MTU now discarded
earlier (f.e. we avoid pointless netfilter postrouting trip).

While at it, drop the repeated test ip_exceeds_mtu, checking it once
is enough...

Fixes: fe6cc55f3a9 ("net: ip, ipv6: handle gso skbs in forwarding path")
Signed-off-by: Florian Westphal <fw at strlen.de>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/ipv4/ip_forward.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
index 98d7e53d2afd..bd1c5baf69be 100644
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -42,12 +42,12 @@
 static bool ip_may_fragment(const struct sk_buff *skb)
 {
 	return unlikely((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0) ||
-	       !skb->local_df;
+		skb->local_df;
 }

 static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
 {
-	if (skb->len <= mtu || skb->local_df)
+	if (skb->len <= mtu)
 		return false;

 	if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu)
--
1.9.1