Michael DePaulo | 21 Jul 04:21 2014

Re: x2go client timeout when x2goagent cannot resolve ip

On Sun, Jul 20, 2014 at 7:05 AM, Nikolaos Kefalas <nkefalas@...> wrote:
> I have an Ubuntu 14.04 x64 system with x2go PPA, where certain users
> are restricted from accessing the Internet, but only local network and
> loopack access is allowed. When i try to login from a x2go-client from
> another system, the client connects to the x2goserver but after while
> it timeouts. I suspect that the x2goagent which runs with user uid
> tries to resolve the incoming ip and stalls there waiting the reverse
> dns lookup to be completed.
> Is any way to disable ip address reverse dns lookup for x2goagent?
> Best regards,
> Nikolaos Kefalas

Hi Nikolaos,

1st, can you explain what you mean by "the client connects to the
x2goserver but after while it timeout"? Does the desktop session even
open up, or does it hang during the connection process?

2nd, unless I'm mistaken, x2goagent/nxagent does not do a reverse DNS
lookup. x2goagent/nxagent receives a client connection from the
loopback address because of the SSH tunnel. a The X2Go-related
component that does do a reverse DNS lookup is the linux distro's
sshd. Can you trying SSH'ing into the Ubuntu system and seeing it it
hangs for that reverse DNS lookup?

3rd/also, whenever you are having trouble with reverse DNS lookups in
general on Linux or UNIX, you can do a test of adding the client to
/etc/hosts. This ensures that the reverse name lookup will work,
unless the application somehow hardcodes using DNS instead of using
nss. (name service switching) As long as /etc/nsswitch.conf's "hosts"
line specifes "files" before "dns" & "mdns4_minimal" (which is the
default on Ubuntu 14.04 and virtually every other Linux distro), then
/etc/hosts will be used instead of DNS for every host that exists in