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Subject[v2.6.34-stable 027/165] ipv6: Add GSO support on forwarding path
From: Herbert Xu <>

This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.

commit 0aa68271510ae2b221d4b60892103837be63afe4 upstream.

Currently we disallow GSO packets on the IPv6 forward path.
This patch fixes this.

Note that I discovered that our existing GSO MTU checks (e.g.,
IPv4 forwarding) are buggy in that they skip the check altogether,
when they really should be checking gso_size + header instead.

I have also been lazy here in that I haven't bothered to segment
the GSO packet by hand before generating an ICMP message. Someone
should add that to be 100% correct.

Reported-by: Ralf Baechle <>
Signed-off-by: Herbert Xu <>
Signed-off-by: David S. Miller <>
Signed-off-by: Paul Gortmaker <>
net/ipv6/ip6_output.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 60daecc..2d55954 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -514,7 +514,7 @@ int ip6_forward(struct sk_buff *skb)
if (mtu < IPV6_MIN_MTU)
mtu = IPV6_MIN_MTU;

- if (skb->len > mtu) {
+ if (skb->len > mtu && !skb_is_gso(skb)) {
/* Again, force OUTPUT device used as source address */
skb->dev = dst->dev;
icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);

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