1.9.4: TCP queries when some threads are full

[Havard Eidnes]

> My second question is what the expected behaviour of unbound is for
> TCP connections that are idling. From unbound.conf(5) I see
> "tcp-idle-timeout" defaults to 30000ms, so this tells me a TCP
> connection being silent for 30 seconds will be dropped but maby this
> only matters until we have seen an initial query and will then leave
> the connection forever?
>
> I tracked down the file descriptor for one of the TCP connections to
> unbound, found it was created over 12 hours ago, and then filtered
> for traffic for the host and port that was holding the connection
> with tcpdump, and not a single packet appeared for the several
> minutes I was running it.

As you may have seen, I recently had an "encounter" with unbound
related to handling of TCP sessions, and it looks like there was a
bug that caused unbound with TCP client sessions which had seen an
initial query + response not to re-arm the TCP idle timeout for that
session.

The patch in the pull request at

  https://github.com/NLnetLabs/unbound/pull/122

should be a fix for this issue if I read the code correctly.  If you
are able to do some testing / validation of this, that would be
greatly appreciated.

Best regards,

- Håvard