SSH freeze when UFW is enabled

Posted by Cristian Vrabie on Server Fault See other posts from Server Fault or by Cristian Vrabie
Published on 2011-06-23T07:07:11Z Indexed on 2011/06/23 8:23 UTC
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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 hhtp (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

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