From f2228f785a9d97307aa8ba709088cfda6c3df73f Mon Sep 17 00:00:00 2001 From: Shan Wei Date: Sun, 18 Apr 2010 16:58:22 +0000 Subject: [PATCH] ipv6: allow to send packet after receiving ICMPv6 Too Big message with MTU field less than IPV6_MIN_MTU According to RFC2460, PMTU is set to the IPv6 Minimum Link MTU (1280) and a fragment header should always be included after a node receiving Too Big message reporting PMTU is less than the IPv6 Minimum Link MTU. After receiving a ICMPv6 Too Big message reporting PMTU is less than the IPv6 Minimum Link MTU, sctp *can't* send any data/control chunk that total length including IPv6 head and IPv6 extend head is less than IPV6_MIN_MTU(1280 bytes). The failure occured in p6_fragment(), about reason see following(take SHUTDOWN chunk for example): sctp_packet_transmit (SHUTDOWN chunk, len=16 byte) |------sctp_v6_xmit (local_df=0) |------ip6_xmit |------ip6_output (dst_allfrag is ture) |------ip6_fragment In ip6_fragment(), for local_df=0, drops the the packet and returns EMSGSIZE. The patch fixes it with adding check length of skb->len. In this case, Ipv6 not to fragment upper protocol data, just only add a fragment header before it. Signed-off-by: Shan Wei Signed-off-by: David S. Miller --- 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 65f9c379df3..75d5ef83009 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -629,7 +629,7 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *)) /* We must not fragment if the socket is set to force MTU discovery * or if the skb it not generated by a local socket. */ - if (!skb->local_df) { + if (!skb->local_df && skb->len > mtu) { skb->dev = skb_dst(skb)->dev; icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu); IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), -- 2.20.1