clampmss only partially working on 2.6 kernelmode pppoe?

[Joris]

On Sat, 12 Feb 2005 09:14:51 -0500, Jason Opperisano <opie at 817west.com> wrote:
> On Sat, 2005-02-12 at 09:08, Jason Opperisano wrote:

> keep in mind that "--clamp-mss-to-pmtu" relies on the fact that PMTU
> discovery works along the path of your communication--this is not always
> a valid assumption these days.

Hmmmkay, but then why does it also not work when I manually set the
mss, even to silly low settings like 500?
iptables -I FORWARD -o ppp0 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS 
--set-mss 1300

Perhaps I'm looking in a totally wrong direction to find the cause?
When I reduce the mtu of the masqueraded host (on the local network)
to the mtu of the ppp connection, all problems disappear. (and no,
that's no real solution ;)


>   tcpdump -n -nn -p -i $EXTIF \
>     'icmp[icmptype] = icmp-unreach and icmp[icmpcode] = 4'

This does not match a single packet while testing the login.
I've done a tcpdump (-s0 -w), it's available at http://et.yi.org/hotmail.dump
Ethereal claims "unassembled packet" serveral times, but that may or
may not have anything to do with this problem, it doesn't seem
uncommon with ssl data.



Friendly greetings,
Joris