From: "Svenning Soerensen" <svenning@post5.tele.dk>
To: "David S. Miller" <davem@redhat.com>
Cc: <linux-kernel@vger.kernel.org>, <linux-ipsec@freeswan.org>
Subject: RE: Problem with PMTU discovery on ICMP packets
Date: Mon, 7 May 2001 02:19:02 +0200 [thread overview]
Message-ID: <016e01c0d68b$51da19a0$1400a8c0@sss.intermate.com> (raw)
In-Reply-To: <15092.31381.395563.889405@pizda.ninka.net>
> From: David S. Miller [mailto:davem@redhat.com]
> But I first want to know the real story behind this reboot anomaly.
> Then we will fix any new bug we discover, and apply the icmp patch as
> well.
I've done a bit more testing. The behaviour doesn't change across reboots.
Instead, it seems to be the case that:
If the packet fits within the MTU of the outgoing interface, DF is set.
If the packet doesn't fit, and thus gets fragmented, DF is clear on all
fragments.
Does this make sense?
I think the reason it looked like it changed across reboots might be caused
by the fact that it was influenced by a FreeS/WAN tunnel, which, after a
reboot, didn't always get started successfully.
If the tunnel was down, the packets (2 kB pings) would go out eth0 fragmented
and with DF clear.
If the tunnel was up, they would get routed through the ipsec0 interface
(with a MTU of 16kB) unfragmented and with DF set.
In the latter (normal) case, after arrival and decapsulation at the endpoint
of the tunnel, the packet is doomed because it needs fragmentation to travel
further, but DF is set.
Svenning
next prev parent reply other threads:[~2001-05-07 0:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-05-05 11:36 Problem with PMTU discovery on ICMP packets Svenning Soerensen
2001-05-05 11:44 ` David S. Miller
2001-05-05 14:23 ` Svenning Soerensen
2001-05-05 22:11 ` David S. Miller
2001-05-07 0:19 ` Svenning Soerensen [this message]
2001-05-10 1:21 ` David S. Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='016e01c0d68b$51da19a0$1400a8c0@sss.intermate.com' \
--to=svenning@post5.tele.dk \
--cc=davem@redhat.com \
--cc=linux-ipsec@freeswan.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox