From 14f3ad6f4a12495b32b0dd743bc7179f36658208 Mon Sep 17 00:00:00 2001 From: Ulrich Weber Date: Fri, 26 Feb 2010 04:34:49 -0800 Subject: [PATCH] ipv6: Use 1280 as min MTU for ipv6 forwarding 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 Signed-off-by: David S. Miller --- net/ipv6/ip6_output.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 1a5fe9ad1947..dabf108ad811 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;