MTU blackhole discovery for IPv6 ?

MTU blackhole discovery for IPv6 ?

[David Madore]

Hi,

There's a sysctl called net.ipv4.tcp_mtu_probing: has there been any
work done on the analogous key for IPv6?

I'm encountering a number of asinine network providers who either
discard ICMPs (whether v4 or v6...) or simply don't emit them.  The
IPv6 picture is even bleaker than IPv4 because so much traffic goes
through tunnels like 6to4.  An IPv6 MTU blackhole discovery
implementation would truly save my day.

I understand that RFC 4821 specifies the same algorithms for
packetization layer path MTU discovery in IPv4 and IPv6.  Did Linux
implement this in IPv4 only because there is some difficulty in doing
the same thing for IPv6, or simply because nobody was asking for it?

Happy hacking,

--
     David A. Madore
   ( http://www.madore.org/~david/ )

Re: MTU blackhole discovery for IPv6 ?

[David Miller]

From: David Madore <david+ml@madore.org>
Date: Thu, 7 May 2009 23:19:26 +0200

> There's a sysctl called net.ipv4.tcp_mtu_probing: has there been any
> work done on the analogous key for IPv6?

Just because the sysctl only appears under ipv4/ doesn't mean
that it only controls ipv4 operations.

This applies to all of the TCP controls especially.