Re: PPP connection corruption with Windows client, MPPE, and RDP

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2014-10-09 0:53 GMT+02:00 Michael Richardson <mcr@xxxxxxxxxxxx>:
>I suspect that RDP triggers it with a full-sized TCP packet.
[...]
>  Do you have appropriate
> patches/things-enabled, so that the esp/l2tp/ppp packets all stay in the
> kernel?  If not, then you might also get some debug from xl2tp.
>

I am not sure what esp is. PPP and MPPE are in the kernel. xl2tpd log
says: This binary does not support kernel L2TP. So I guess l2tp
traffic is not in the kernel with my build. I enabled all xl2tpd debug
options and get some results that seems to confirm what you say about
the full-sized TCP packet. A whole connect/troubles/disconnect session
is logged. Troubles start at "Unsupported protocol..." lines. I don't
know how to sort, though.

Log is attached.

> Can you tcpdump on the pppX interfaces on both sides?
> I suspect that RDP triggers it with a full-sized TCP packet.
>

I can't now but I'll do it tomorrow if the provided xl2tpd debug isn't enough.

>
>     > This initially seemed to me an IPSEC problem but, after much
>     > troubleshooting, removing the ppp option "require-mppe-128" option and
>     > adding "nomppe", effectively disabling MPPE, resulted in a extremely
>     > reliable connection again.
>
> MPPE and IPsec are not related. AFAIK, MPPE provides for encryption within
> PPP.  you would be double encrypting.
>

Yes, I knew. In fact I was more than satisfied with the reliability I
get with "nomppe". But maybe MS-CHAP v2 use MPPE for authentication
encryption? I don't know.

>     > client-server related: RDP it's just the trigger, after the whole
>     > connection TCP/IP connection is corrupted and must be reset; - It's not
>
> Does other traffic continue to function?
> Is one end Windows?
>
>

No, other traffic stops as well. VPN traffic is Windows-Windows.
ipsec-ppp-l2tp endpoints are Windows-Linux.

Attachment: log-xl2tpd-pppd
Description: Binary data


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