Date: Sun, 05 Mar 2000 03:49:23 +0000 From: Brian Somers <brian@Awfulhak.org> To: Brian Somers <brian@Awfulhak.org> Cc: Dermot McNally <dermot@mcnally.de>, Dermot McNally <dermo@mcnally.de>, freebsd-net@FreeBSD.org, peter@FreeBSD.org, jkh@FreeBSD.org, joe@FreeBSD.org, brian@hak.lan.awfulhak.org, brian@hak.lan.awfulhak.org Subject: Re: NAT issues with ppp - a fix Message-ID: <200003050349.DAA03010@hak.lan.Awfulhak.org> In-Reply-To: Message from Brian Somers <brian@Awfulhak.org> of "Sun, 05 Mar 2000 02:20:15 GMT." <200003050220.CAA02369@hak.lan.Awfulhak.org>
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> > At 02:18 04.03.2000 +0000, Brian Somers wrote:
> > >Hi,
> > >
> > >Because of a recent change in the way I connect to the net
> > >(PPPoUDPoPPPoISDN), I'm now seeing this problem !
> > >
> > >Can you try the attached patch ? I believe this fixes the problem !
> >
> > Bad news on my side - it doesn't appear to have helped. My test case:
> > Before applying the patch, I cvsupped to today's current and rebuilt the
> > world. Then I set the gateway box and a FreeBSD alpha box on my internal
> > network back to an MTU of 1500. I connected to confirm that the problem was
> > still there (it was).
> >
> > Then I applied the patch, rebuilt and installed ppp. Same test. Same
> > problem - well, same symptoms anyway. My two tests were, using Lynx to
> > connect to effectively any WWW site and using fetch to download a biggish
> > file. Fetch determines the file size (which I don't recall it managing to
> > do before), but doesn't actually get any further with the download. Lynx
> > manages to look up the site to which I try to connect, but then hangs at
> > the "waiting for response" stage.
> >
> > I can packet sniff this if you think it will help - my setup is slightly
> > different to yours: PPPoE via a DSL "modem".
>
> Mine is even more tricky... I've been battling this for some time
> now.
>
> I've actually got
>
> laptop <mtu 1500>-ethernet-<mtu 1500>gate<mtu 1466>-PPPoUDPoPPPoISDN-<mtu 1466> - PPPoISDN gateway - <mtu 1500> 'net - <mtu 1500> - PPPoUDP gateway - 'net
>
> The tricky bit is that I have to run the PPPoUDP link in MP mode using
> a 1466 byte MRRU. This will make the IP layer fragment the traffic to
> 1466 bytes, allowing ppp to pile a UDP/IP header of 28 bytes back on
> the front (and to add the 2/4 byte MP header and 1/2 byte protocol
> header) before sending out the UDP datagram.
>
> It's vital that the PPP/UDP/IP packet is no more than 1500 bytes as
> it's going to pop up at my gateway and then must travel across the
> 'net to the PPP/UDP gateway before it's unpacked and reassembled into
> what was sent out originally.
>
> I *think* this should work now - assuming the fragmentation side of
> things is functional. I haven't proven things yet though.
>
> I'll follow up....
[.....]
This works (with the previous patch), but requires an MRRU of
1338.... as there can be up to 128 bytes of options (is this right
anyone ?).
This means three things. First, I get to play with doing MP over two
separate ISPs for real (soon). Second I get a compressed ISDN link
with a static IP despite the transport being brought up and down with
dynamic IP numbers :*P
And third, your problem must be something specific to PPPoE as it
looks like there are no NAT/fragmentation problems any more
(otherwise my setup can't work).
I guess I'm gonna have to try to set up a proper PPPoE environment
here. I'll follow-up when I can.
--
Brian <brian@Awfulhak.org> <brian@[uk.]FreeBSD.org>
<http://www.Awfulhak.org>; <brian@[uk.]OpenBSD.org>
Don't _EVER_ lose your sense of humour !
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