Subject: Re: PMTUD blackhole detection
To: Jun-ichiro itojun Hagino <firstname.lastname@example.org>
From: Kevin Lahey <email@example.com>
Date: 05/01/2001 11:11:29
In message <20010501084913.3B8617D4@starfruit.itojun.org>Jun-ichiro itojun Hagi
> on PR 12790, I posted a simple patch for TCP PMTUD blackhole detection.
> if there's no ack for a while, the patch will do the following:
> - turn off path MTU discovery for IPv4
> - uses minimum MTU (1280) for IPv6
> the behavior will remedy path MTU discovery blackhole, if our side
> is the sender of bigger packet. it does not solve problems when
> the other side is sending bigger packet and choking with the lack
> of icmp too big messages.
> see RFC2923 section 2.1 for the exact description of the issue.
Cool. Is there some way that we could set a flag in the route,
rather than just having a per-connection flag? That way we only have
to pay the cost of the two timeouts once per black hole, rather
than once per connection...
> i have no environment to test, so i need your help.
I can try to test it, but I'm not sure how soon I'll have a chance.
I usually set up a test environment with a PPP link or something where
I can easily set the MTU, and then hack the PPP box to not return the
ICMP too big message.