* [PATCH 1/2] ipv6: fix mss when it is bigger than IPV6_MAXPLEN - sizeof(struct tcphdr)
@ 2012-02-28 8:28 roy.qing.li
2012-02-28 8:28 ` [PATCH 2/2] ipv4: fix mss comparison roy.qing.li
2012-02-28 9:56 ` [PATCH 1/2] ipv6: fix mss when it is bigger than IPV6_MAXPLEN - sizeof(struct tcphdr) Eric Dumazet
0 siblings, 2 replies; 6+ messages in thread
From: roy.qing.li @ 2012-02-28 8:28 UTC (permalink / raw)
To: netdev
From: RongQing.Li <roy.qing.li@gmail.com>
When mss is bigger than IPV6_MAXPLEN - sizeof(struct tcphdr),
set mss to IPV6_MAXPLEN - sizeof(struct tcphdr), not IPV6_MAXPLEN.
Signed-off-by: RongQing.Li <roy.qing.li@gmail.com>
---
net/ipv6/route.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 92be12b..42cc16c 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1054,7 +1054,7 @@ static unsigned int ip6_default_advmss(const struct dst_entry *dst)
* rely only on pmtu discovery"
*/
if (mtu > IPV6_MAXPLEN - sizeof(struct tcphdr))
- mtu = IPV6_MAXPLEN;
+ mtu = IPV6_MAXPLEN - sizeof(struct tcphdr);
return mtu;
}
--
1.7.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 2/2] ipv4: fix mss comparison
2012-02-28 8:28 [PATCH 1/2] ipv6: fix mss when it is bigger than IPV6_MAXPLEN - sizeof(struct tcphdr) roy.qing.li
@ 2012-02-28 8:28 ` roy.qing.li
2012-02-28 9:34 ` Francois Romieu
2012-02-28 10:01 ` Eric Dumazet
2012-02-28 9:56 ` [PATCH 1/2] ipv6: fix mss when it is bigger than IPV6_MAXPLEN - sizeof(struct tcphdr) Eric Dumazet
1 sibling, 2 replies; 6+ messages in thread
From: roy.qing.li @ 2012-02-28 8:28 UTC (permalink / raw)
To: netdev
From: RongQing.Li <roy.qing.li@gmail.com>
mss should compare with 65535 - sizeof(struct tcphdr),
the largest mss is 65535 - sizeof(struct tcphdr).
40 is sum of sizeof(struct tcphdr) and sizeof(struct iphdr)
Signed-off-by: RongQing.Li <roy.qing.li@gmail.com>
---
net/ipv4/route.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 0489ced..c72f765 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1914,8 +1914,8 @@ static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
if (advmss == 0) {
advmss = max_t(unsigned int, dst->dev->mtu - 40,
ip_rt_min_advmss);
- if (advmss > 65535 - 40)
- advmss = 65535 - 40;
+ if (advmss > 65535 - sizeof(struct tcphdr))
+ advmss = 65535 - sizeof(struct tcphdr);
}
return advmss;
}
--
1.7.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH 2/2] ipv4: fix mss comparison
2012-02-28 8:28 ` [PATCH 2/2] ipv4: fix mss comparison roy.qing.li
@ 2012-02-28 9:34 ` Francois Romieu
2012-02-28 9:55 ` RongQing Li
2012-02-28 10:01 ` Eric Dumazet
1 sibling, 1 reply; 6+ messages in thread
From: Francois Romieu @ 2012-02-28 9:34 UTC (permalink / raw)
To: roy.qing.li; +Cc: netdev
roy.qing.li@gmail.com <roy.qing.li@gmail.com> :
[...]
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index 0489ced..c72f765 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -1914,8 +1914,8 @@ static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
> if (advmss == 0) {
> advmss = max_t(unsigned int, dst->dev->mtu - 40,
> ip_rt_min_advmss);
> - if (advmss > 65535 - 40)
> - advmss = 65535 - 40;
> + if (advmss > 65535 - sizeof(struct tcphdr))
> + advmss = 65535 - sizeof(struct tcphdr);
What would prevent net/ipv4/tcp_output.c::tcp_advertise_mss returning
a value beyond 65535 - 40 ?
--
Ueimor
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 2/2] ipv4: fix mss comparison
2012-02-28 9:34 ` Francois Romieu
@ 2012-02-28 9:55 ` RongQing Li
0 siblings, 0 replies; 6+ messages in thread
From: RongQing Li @ 2012-02-28 9:55 UTC (permalink / raw)
To: Francois Romieu; +Cc: netdev
2012/2/28 Francois Romieu <romieu@fr.zoreil.com>:
> roy.qing.li@gmail.com <roy.qing.li@gmail.com> :
> [...]
>> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
>> index 0489ced..c72f765 100644
>> --- a/net/ipv4/route.c
>> +++ b/net/ipv4/route.c
>> @@ -1914,8 +1914,8 @@ static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
>> if (advmss == 0) {
>> advmss = max_t(unsigned int, dst->dev->mtu - 40,
>> ip_rt_min_advmss);
>> - if (advmss > 65535 - 40)
>> - advmss = 65535 - 40;
>> + if (advmss > 65535 - sizeof(struct tcphdr))
>> + advmss = 65535 - sizeof(struct tcphdr);
>
> What would prevent net/ipv4/tcp_output.c::tcp_advertise_mss returning
> a value beyond 65535 - 40 ?
>
You are right, Please ignore this patch.
The biggest MSS should be (Total Length of ipv4 header -
sizeof(iphdr)- sizeof(tcphdr))
I mix up the Total Length of ipv4 header and Payload Length of ipv6 header.
> --
> Ueimor
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2] ipv4: fix mss comparison
2012-02-28 8:28 ` [PATCH 2/2] ipv4: fix mss comparison roy.qing.li
2012-02-28 9:34 ` Francois Romieu
@ 2012-02-28 10:01 ` Eric Dumazet
1 sibling, 0 replies; 6+ messages in thread
From: Eric Dumazet @ 2012-02-28 10:01 UTC (permalink / raw)
To: roy.qing.li; +Cc: netdev
Le mardi 28 février 2012 à 16:28 +0800, roy.qing.li@gmail.com a écrit :
> From: RongQing.Li <roy.qing.li@gmail.com>
>
> mss should compare with 65535 - sizeof(struct tcphdr),
> the largest mss is 65535 - sizeof(struct tcphdr).
> 40 is sum of sizeof(struct tcphdr) and sizeof(struct iphdr)
>
> Signed-off-by: RongQing.Li <roy.qing.li@gmail.com>
> ---
> net/ipv4/route.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index 0489ced..c72f765 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -1914,8 +1914,8 @@ static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
> if (advmss == 0) {
> advmss = max_t(unsigned int, dst->dev->mtu - 40,
> ip_rt_min_advmss);
> - if (advmss > 65535 - 40)
> - advmss = 65535 - 40;
> + if (advmss > 65535 - sizeof(struct tcphdr))
> + advmss = 65535 - sizeof(struct tcphdr);
> }
> return advmss;
> }
Hmm... I am puzzled.
1) If you touch this code, please use min_t() macro to be consistent
with prior line ? Please note I dont advocate a general use of these
min/max macros, just some consistency in the same page of code.
2) Prior line still has the magic 40 value.
(I personally like 40 more than sizeof(struct tcphdr) +
sizeof(struct iphdr)), its not like 40 is going to change one day :)
3) What is the maximum datagram size in ipv4.
(Say you name this IPV4_MAXPLEN)
4) What would be the meaning of having TCP MSS bigger than
IPV4_MAXPLEN - 40 ?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] ipv6: fix mss when it is bigger than IPV6_MAXPLEN - sizeof(struct tcphdr)
2012-02-28 8:28 [PATCH 1/2] ipv6: fix mss when it is bigger than IPV6_MAXPLEN - sizeof(struct tcphdr) roy.qing.li
2012-02-28 8:28 ` [PATCH 2/2] ipv4: fix mss comparison roy.qing.li
@ 2012-02-28 9:56 ` Eric Dumazet
1 sibling, 0 replies; 6+ messages in thread
From: Eric Dumazet @ 2012-02-28 9:56 UTC (permalink / raw)
To: roy.qing.li; +Cc: netdev
Le mardi 28 février 2012 à 16:28 +0800, roy.qing.li@gmail.com a écrit :
> From: RongQing.Li <roy.qing.li@gmail.com>
>
> When mss is bigger than IPV6_MAXPLEN - sizeof(struct tcphdr),
> set mss to IPV6_MAXPLEN - sizeof(struct tcphdr), not IPV6_MAXPLEN.
>
> Signed-off-by: RongQing.Li <roy.qing.li@gmail.com>
> ---
> net/ipv6/route.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 92be12b..42cc16c 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -1054,7 +1054,7 @@ static unsigned int ip6_default_advmss(const struct dst_entry *dst)
> * rely only on pmtu discovery"
> */
> if (mtu > IPV6_MAXPLEN - sizeof(struct tcphdr))
> - mtu = IPV6_MAXPLEN;
> + mtu = IPV6_MAXPLEN - sizeof(struct tcphdr);
> return mtu;
> }
>
Hmm... What about the comment above the code mentioning pmtu discovery ?
/*
* Maximal non-jumbo IPv6 payload is IPV6_MAXPLEN and
* corresponding MSS is IPV6_MAXPLEN - tcp_header_size.
* IPV6_MAXPLEN is also valid and means: "any MSS,
* rely only on pmtu discovery"
*/
Check out code from net/ipv6/ip6_output.c, ip6_append_data() :
if (mtu <= sizeof(struct ipv6hdr) + IPV6_MAXPLEN) {
if (cork->length + length > sizeof(struct ipv6hdr) + IPV6_MAXPLEN - fragheaderlen) {
ipv6_local_error(sk, EMSGSIZE, fl6, mtu-exthdrlen);
return -EMSGSIZE;
}
}
and __ip6_local_out()
if (len > IPV6_MAXPLEN)
len = 0;
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2012-02-28 10:01 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2012-02-28 8:28 [PATCH 1/2] ipv6: fix mss when it is bigger than IPV6_MAXPLEN - sizeof(struct tcphdr) roy.qing.li
2012-02-28 8:28 ` [PATCH 2/2] ipv4: fix mss comparison roy.qing.li
2012-02-28 9:34 ` Francois Romieu
2012-02-28 9:55 ` RongQing Li
2012-02-28 10:01 ` Eric Dumazet
2012-02-28 9:56 ` [PATCH 1/2] ipv6: fix mss when it is bigger than IPV6_MAXPLEN - sizeof(struct tcphdr) Eric Dumazet
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