Cygwin, SSH, and Windows XP SP2

For about a month I’ve been struggling with an annoying problem using Cygwin’s SSH to communicate between my two PCs. In early September, several applications just stopped working, including Unison, rsync, and WinCVS. All of them would hang while trying to connect to the server computer via Cygwin’s SSH. But SSH at the command prompt still worked fine. I was mystified until today, when I came across this post:

It looks like a problem with a recent release of the cygwin engine – maybe in conflict with SP2. If I downgrade the cygwin engine from 1.5.11-1 to 1.5.10-3 unison works as expected. If I switch back to 1.5.11-1 unison freezes after I enter my ssh password.

So I also downgraded to 1.5.10-3 and it works fine now. Awesome!

Note that the problem is independent of SP2’s new firewall…I’m not running that. I eventually found more detail here, which suggests the problem was due to an update in Cygwin’s pipe handling code conflicting with SP2.

Can’t all these upgrades just get along?