[dnsdist] 1.9.2 crashing in tcpClient

[Holger Hoffstätte]

Hi,

a quick PSA. I was delighted to see the release of 1.9.2; unfortunately that
delight quickly soured as it has now crashed twice in a row, within a few
minutes of each other. :(

Self-compiled with the exactly same build config as 1.9.0/1 and identical
runtime config:

[Apr 5 11:51] traps: dnsdist/tcpClie[25311] general protection fault ip:55c9ac5b1c43 sp:7fe47dfff650 error:0 in dnsdist[55c9ac22c000+496000]

I don't have a reproducer (and no time to debug this right now), but I
_exclusively_ use plain old UDP for my outgoing requests with a single
relevant config change related to TCP handling: setMaxTCPClientThreads(1).

I've seen the occasional TCP request being made presumably for fallback handling
of too-large requests, but this has been running fine since forever so it's
likely that one of the recent changes subtly broke this.
  
Sorry to be so vague but that's all I got right now.

Holger