Le 07/29/14 20:57, Gert Doering a écrit : > On Tue, Jul 29, 2014 at 07:28:49PM +0200, Julien Muchembled wrote: >> Socket configuration of MTU discovery was done unconditionally at IP level, >> which has no effect for other protocols. This fixes the issue of OpenVPN >> sending fragmented tcp6/udp6 packets even when 'mtu-disc yes' option is >> passed. > > Sounds good. I'm not sure I understand what that socket option *does*, > though... will it make the kernel report back any ICMP packet too big > messages received? Or will it not honour those unless IPV6_MTU_DISCOVER > is set? > > Is there documentation for that socket option somewhere?
'man 7 ip' and 'man 7 ipv6'
For example:
A --[mtu=1500]-- B --[mtu=1400]-- C
Given a UDP6 socket on A with IPV6_MTU_DISCOVER=IP_PMTUDISC_DO,
sendto(1452 bytes, B) will succeed
but sendto(1452 bytes, C) will return EMSGSIZE (except for the first send to C)
Yes, at some point, there are icmp packets.
> (Last not least, because I'm too lazy to look: is that patch against
> git master or against release/2.3?)
master
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