PatchLog

I'm working on a patch for antinat, to make it do some cool/weird stuff that it can't do at the moment.

In case you're wondering antinat is a great implementation of a socks server. It supports socks4, socks5 with user/password authentication, accept/reject acls based on user or ip, easy configuration in an XML file and it's also multithreaded ( ok maybe this is not so great for some but I like it ).

I'm not going to write about the patch I'm working on but maybe I'll write about that in another post.

While I was looking over it's source code I found this funny comment right before a function that was used to handle the SIGPIPE signal:

 
/*
UNIX trivia - when is a problem a problem?  When you don't ignore it.
If you do nothing, well, you're not being ignorant enough.  You have
to be explicitly ignorant.
*/

This is funny but the comment has a good point. If you write an application and it tries to write to a connection that was closed, your program will receive a signal with the code SIGPIPE, which means ( according to the man page of the kill program) that if the proces does not have a default handler for SIGPIPE then it will just exit. So there you have a big problem.

The simple solution is to just set your own signal handler for SIGPIPE . So you have to set a function that will be called when the program receives a SIGPIPE and your function doesn't really have to do anything about it, so it will just ignore it and reset the handler to itself.

 
void
ignorer (int x)
{
        signal (x, ignorer);
}
 

But if you don't explicitly set this, your process will just die upon receiving a SIGPIPE and you really don't want that especially when writing server applications.

This entry was posted on Monday, October 1st, 2007 at 7:11 pm and is filed under nix. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.