diff mbox

[net-next] ipv6: Use 1280 as min MTU for ipv6 forwarding

Message ID 20100226123244.GB9114@babylon
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Ulrich Weber Feb. 26, 2010, 12:32 p.m. UTC 
Clients will set their MTU to 1280 if they receive a
ICMPV6_PKT_TOOBIG message with an MTU less than 1280.

To allow encapsulating of packets over a 1280 link
we should always accept packets with a size of 1280
for forwarding even if the path has a lower MTU and
fragment the encapsulated packets afterwards.

In case a forwarded packet is not going to be encapsulated
a ICMPV6_PKT_TOOBIG msg will still be send by ip6_fragment()
with the correct MTU.

Signed-off-by: Ulrich Weber <uweber@astaro.com>
---
 net/ipv6/ip6_output.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)

Comments

David Miller Feb. 26, 2010, 12:34 p.m. UTC | #1 
From: Ulrich Weber <uweber@astaro.com>
Date: Fri, 26 Feb 2010 13:32:44 +0100

> Clients will set their MTU to 1280 if they receive a
> ICMPV6_PKT_TOOBIG message with an MTU less than 1280.
> 
> To allow encapsulating of packets over a 1280 link
> we should always accept packets with a size of 1280
> for forwarding even if the path has a lower MTU and
> fragment the encapsulated packets afterwards.
> 
> In case a forwarded packet is not going to be encapsulated
> a ICMPV6_PKT_TOOBIG msg will still be send by ip6_fragment()
> with the correct MTU.
> 
> Signed-off-by: Ulrich Weber <uweber@astaro.com>

Applied, thanks for fixing up this patch.
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diff mbox

Patch

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 1a5fe9a..dabf108 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -402,6 +402,7 @@  int ip6_forward(struct sk_buff *skb)
 	struct ipv6hdr *hdr = ipv6_hdr(skb);
 	struct inet6_skb_parm *opt = IP6CB(skb);
 	struct net *net = dev_net(dst->dev);
+	u32 mtu;
 
 	if (net->ipv6.devconf_all->forwarding == 0)
 		goto error;
@@ -508,10 +509,14 @@  int ip6_forward(struct sk_buff *skb)
 		}
 	}
 
-	if (skb->len > dst_mtu(dst)) {
+	mtu = dst_mtu(dst);
+	if (mtu < IPV6_MIN_MTU)
+		mtu = IPV6_MIN_MTU;
+
+	if (skb->len > mtu) {
 		/* Again, force OUTPUT device used as source address */
 		skb->dev = dst->dev;
-		icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, dst_mtu(dst));
+		icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
 		IP6_INC_STATS_BH(net,
 				 ip6_dst_idev(dst), IPSTATS_MIB_INTOOBIGERRORS);
 		IP6_INC_STATS_BH(net,
@@ -621,8 +626,7 @@  static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 	mtu = ip6_skb_dst_mtu(skb);
 
 	/* We must not fragment if the socket is set to force MTU discovery
-	 * or if the skb it not generated by a local socket.  (This last
-	 * check should be redundant, but it's free.)
+	 * or if the skb it not generated by a local socket.
 	 */
 	if (!skb->local_df) {
 		skb->dev = skb_dst(skb)->dev;