Resolved

Using 1.3b16 though this issue was also in b15, and I'm sure a few earlier versions.

SSH and RDP sessions which are left idle for ~5 minutes or more are being dropped.

Others experiencing the same issue:
http://forum.m0n0.ch/index.php/topic,2887.0.html

I've done some testing myself today with 1.3b16, and can confirm that plain TCP connections (like SSH sessions) time out after 10 minutes without any traffic.

However, it looks more like a NAT translation timeout issue than a problem with the packet filter (but, of course, it would usually appear the same as the majority of setups use NAT). Specifically, ipfilter has a default NAT timeout of 10 minutes. IIRC there should be a mechanism to keep active entries alive, but I'll have to investigate further on why this does not work. I'll post updates here.

Looks like this problem is fixed with FreeBSD 6.4, which will be used in the next release. Please try again with 1.3b17 when it's out (should be in a couple of weeks). Thanks for the report!

Thanks Manuel.  I appreciate the hard work you put into this.

I can't speak to RDP sessions because I don't use them.  But I would consider SSH sessions fixed with 1.3b18!

Thanks Manuel!!