Re: [Libvir] PATCH: Prevent zombie ssh tunnels

On Tue, Sep 11, 2007 at 04:56:13AM -0400, Daniel Veillard wrote: > On Tue, Sep 11, 2007 at 12:59:59AM +0100, Daniel P. Berrange wrote: > > I noticed that when using the SSH tunnel for the remote driver I ended up > > with alot of zombie SSH processes. We simply forgot to waitpid() on the > > child when a connection attempt failed, or when shutting down an open remote > > connection. Attached is a possible patch > > Looks fine, like Rich maybe a bit of refactoring might be good. The > only worries I have is the following scenario: > - the ssh process dies > - libvirt based application takes some time to notice it > - the OS span a new process with the same PID after a PID rollabck > (not completely unlikely since the ssh may have been started a long > time ago) > - we end-up killing a random process in the system > > I think this is mostly avoidable by resetting priv->pid to -1 or 0 on > any child communication error, and before doing the kill in the patch. > Even better would be to be able to check that the process corresponding > to priv->pid is still a child of the current process, I wonder if this > can be achieved without blocking with an initial waitpid() After some testing I believe we can safely do away with kill() completely. If we simply close(priv->sock) which is our end of the socketpair used to talk to SSH, then SSH detects the end-of-file condition and exits of its on accord. So there's no need to kill() - just close the socket and waitpid() seems to do the trickm, unless I'm missing something bad.