I have a small Ubuntu 10.10 server and i recently noticed a weird behavior (not sure if it was happening before). If I have ufw enabled (with default deny all in, allow all out, allow all http, allow all on a random port i use for ssh) when i perform some actions in a ssh sesion, the ssh console completely freezes. The server continues to work and if i close the console i can start another ssh session. This happens no matter from where I log in (tried from another ubuntu and a mac). The actions are fairly reproducible, for example vim some config files (though vim-ing other files works), cat some other file, etc. The freeze never happens if ufw is disabled. Any idea what's going on? Thanks! Cristian

Addition: if you're wondering, yes, I have TcpKeepAlive on yes and I doubt is related (it would happen with ufw disabled too)

As requested: my ufw conf below. Also, i don't know if it has something to do but the server has 2 ips. On one is configured the ssh domain, and on one to serve http (via apache2)

Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing)
New profiles: skip

To                         Action      From
--                         ------      ----
19922/tcp                  ALLOW IN    Anywhere
9418/tcp                   ALLOW IN    Anywhere
80/tcp                     ALLOW IN    Anywhere
443/tcp                    ALLOW IN    Anywhere
  • It would help if you copy-pasted your ufw configuration, in case there's a typo you missed or something. – Gilles 'SO- stop being evil' Jun 23 '11 at 7:22
  • @Gilles : added ufw config in description. it's very basic, i doubt that there's something there. Hmm, now that i think about it, when i do ufw enable i always get "ERROR: problem running ufw-init". If I repeat the command, then it starts. – Cristian Vrabie Jun 23 '11 at 7:55
  • Never used ufw, but what you want to do is allow already established sessions (and future RELATED, of course). – 3molo Jun 23 '11 at 10:20

It seems that ufw has a problem with VPSs. Might be related to this: http://blog.bodhizazen.net/linux/how-to-use-ufw-in-openvz-templates/ I'll stick to using iptables.

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