[FreeNX-kNX] Re: Connection error with ubuntu 10.04 & 10.10

[Arnaud Fenioux]

On Mon, Jan 3, 2011 at 11:28 AM,  <chris at ccburton.com> wrote:

> [SNIP]
>> I mean, it worked for windows, not for Linux event if I set the mtu to
>> 1500
>> >
>> >> why did it worked with previous version of ubuntu ( 9.10-  server-side
>> >> speaking) ?
>
> Something has changed somewhere !! Lets have a look.
>
>> > Sounds like something isn't letting ICMP through, so it is defaulting to
>> > 1500, and/or something just isn't working, like the 3G driver on 10.04
>> > thinks it should be set to 1500 when the link provided is actually
>> > lower.
>> >
>> > Try putting the server back up to 1500 and setting the 3G interface
>> > to something lower.
>>
>> I tried severals values on the 3G interface (500-1500), nothing worked,
>> the reason could be because I'm NATed/Proxyfied by my ISP...
>> I'm using a 10.x.x.x IP on a "point to point noarp multicast"  link
>
> That's not the issue else the windows connection to NX wouldn't work.
>
> I'd say that two things are broken.
>
> 1/ The 3G linux driver is not setting the MTU (it does in windows
>         so PMTUD isn't needed)
>
> 2/ The NX server is not getting ICMP, so it won't get pings, nor
> will it get PMTUD (I doubt only Type3-C4 packets are filtered).
>
> So, on the NX server run your favourite tcpdump :-
>         (sudo) tcpdump -vv icmp
> then
>         ping the NX server from :-
>         your 3G
>         your remote ADSL and
>         the NX-server segment
>
> This should help spot any ICMP filtering.
>
> Then leaving tcpdump running:-
>         connect an NX session
> watch for "Frag needed and DF set" as the session connects
> and see what sends them.
>
> I predict you won't see any, because something is filtering them
> out until you find and remove the filtering.
> So
> Do you run a firewall on the 10.04 server
> or
> do you have ICMP disabled on the edge router at the NX
> site
> (maybe 9.04 does something different from 10.04 - like not having
> a bug in PMTUD or maybe even not having PMTUD switched
> off as a default (unlikely), or maybe 9.04 automatically reduces
> the MTU if connections get interrupted, without waiting for ICMP
> to tell it that it needs to)
>

no filtering on icmp on my side, I "permit any icmp"...
but I didn't see any "Frag needed and DF set" packet...

But after a Fresh install of ubuntu 10.04 with the 3.3.0 backend (karmic pkg)
everything is OK even over 3G under linux

>>
>> Well, happy new year!
>
> And to you too !!
>
>> and BTW, do you have an idea, why 3.4.0 backend is (really) slower
>> than the 3.3.0 (even in ADSL) to establish the display connection? ;)
>
> I haven't noticed this difference. Check to see where your delay is
> occuring.
> Is it part of the NX ssh connection (eg sshd dns reverse lookups) or
> is it after the ssh connection is in place, at agent startup ??



I haven't this lag in lan, but only on the internet...
As you can see below there is a ~30seconds lag
I give up, and use the 3.3.0 backend.
thank you for your help, one more time

Arnaud

----
Fri Jan  7 14:41:11 CET 2011: startsession: starting with args ""
Fri Jan  7 14:41:11 CET 2011: startsession: generate
"/home/user/.nx/C-nx3-2001-FF27FE0E0CCE081A763B94D1CEE0AF45/options"
Fri Jan  7 14:41:11 CET 2011: startsession: write xauth script file
Fri Jan  7 14:41:11 CET 2011: startsession: call 'node_start_agent'
 [SNIP]
Fri Jan  7 14:41:11 CET 2011: node_start_applications: DISPLAY is 2001
Fri Jan  7 14:41:11 CET 2011: node_start_agent: env end
Fri Jan  7 14:41:11 CET 2011: node_start_agent: Start nxagent by
command: '/usr/bin/nxagent -persistent -D -name "NX -
user at nxserver:2001 - bounce (GPL Edition)" -option
"/home/user/.nx/C-nx3-2001-FF27FE0E0CCE081A763B94D1CEE0AF45/options"
-nolisten tcp :2001'
Fri Jan  7 14:41:11 CET 2011: node_start_agent: Wait for NODE_AGENT_PID (6604)
Fri Jan  7 14:41:40 CET 2011: node_find_application: starting with
args "unix-gnome"
Fri Jan  7 14:41:40 CET 2011: node_find_application: return
NODE_STARTX="gnome-session"
Fri Jan  7 14:41:40 CET 2011: node_find_application: end
Fri Jan  7 14:41:40 CET 2011: node_start_applications: Got
NODE_APPLICATION is "gnome-session"