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 <shanwei@xxxxxxxxxxxxxx>
---
net/ipv6/ip6_output.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 5129a16..c3edb6c 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -625,7 +625,7 @@ 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)),
--
1.6.3.3
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