[PATCH BUG-FIX] ipv6: allow to send packet after receiving ICMPv6

[PATCH BUG-FIX] ipv6: allow to send packet after receiving ICMPv6

[Shan Wei]

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\x16 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(-)

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 

[PATCH BUG-FIX] ipv6: allow to send packet after receiving ICMPv6 Too Big message with MTU field less than IPV6_MIN_MTU

[Shan Wei]

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(-)

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 

Re: [PATCH BUG-FIX] ipv6: allow to send packet after receiving

[Herbert Xu]

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\x16 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,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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Re: [PATCH BUG-FIX] ipv6: allow to send packet after receiving ICMPv6 Too Big message with MTU field less than IPV6_MIN_MTU

[Herbert Xu]

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,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH BUG-FIX] ipv6: allow to send packet after receiving ICMPv6

[Shan Wei]

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. 

-- 
Best Regards
-----
Shan Wei


> 
> Thanks,

Re: [PATCH BUG-FIX] ipv6: allow to send packet after receiving ICMPv6 Too Big message with MTU field less than IPV6_MIN_MTU

[Shan Wei]

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. 

-- 
Best Regards
-----
Shan Wei


> 
> Thanks,

Re: [PATCH BUG-FIX] ipv6: allow to send packet after receiving

[David Miller]

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\x16 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.

Re: [PATCH BUG-FIX] ipv6: allow to send packet after receiving ICMPv6 Too Big message with MTU field less than IPV6_MIN_MTU

[David Miller]

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.