Maintained by: NLnet Labs

[Unbound-users] TCP and/or UDP used by resolver?

Paul Wouters
Thu Aug 25 17:52:17 CEST 2011

On Thu, 25 Aug 2011, Patrik Fältström wrote:

> Hi, I use the pylons package and see that one can set the transport mechanism via the set_usevc call. The argument is boolean and one set whether a virtual circuit can be used or not. What makes me confused is that I feel such a value should have three states: UDP/TCP with fallback, UDP only and TCP only.
> I read the manual as if this (when true) uses TCP only, but if false uses UDP with fallback to TCP.
> Or is the value to use UDP with fallback to TCP, but UDP only if false?
> Can someone help with interpretation please?
>   Patrik
> P.S. In my code that test DNS I want to be able to set whether UDP or TCP is in use, with no fallback, but then I also have "normal" queries that can use whatever works (and I do not care what was used).
> P.P.S. This is my part of the testing of pylons with Python3 and so far it works!

I think the easiest is to configure multiple unbound instances. One with defaults, one with do-tcp:no

In svn there is also the tcp-upstream:yes|no option that controls if tcp can be used by the resolver to
obtain data (as opposed to the client method of accessing unbound itself)