| Message ID | 4BCBC6CE.9020302@cn.fujitsu.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Mon, Apr 19, 2010 at 10:58:22AM +0800, Shan Wei wrote: > > 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@cn.fujitsu.com> The patch looks good to me. If we wanted to optimise the allfrags case it may be better to reserve the space beforehand and generate the fragment header at the same time as we're doing the IPv6 header. But it can't be all that important as it's been broken for so many years. Thanks,
Herbert Xu wrote, at 04/19/2010 11:55 AM: > > The patch looks good to me. Thanks for reviewing this patch. > If we wanted to optimise the allfrags case it may be better > to reserve the space beforehand and generate the fragment header > at the same time as we're doing the IPv6 header. > > But it can't be all that important as it's been broken for so > many years. If somebody needs one patch to fix the broken, I am pleased to do so.
From: Herbert Xu <herbert@gondor.apana.org.au> Date: Mon, 19 Apr 2010 11:55:35 +0800 > On Mon, Apr 19, 2010 at 10:58:22AM +0800, Shan Wei wrote: >> >> 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@cn.fujitsu.com> > > The patch looks good to me. > > If we wanted to optimise the allfrags case it may be better > to reserve the space beforehand and generate the fragment header > at the same time as we're doing the IPv6 header. > > But it can't be all that important as it's been broken for so > many years. Right, I've applied Shan's patch, thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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)),
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@cn.fujitsu.com> --- net/ipv6/ip6_output.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) -- 1.6.3.3 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html