bind 9.16 vs. 9.14 tcp client connections

[sthaug at nethelp.no]

> I believe this problem should be fixed in 9.16.1:
> 
> 5361.	[bug]		named might not accept new connections after
> 			hitting tcp-clients quota. [GL #1643]
> 
> However, we had two authoritative name servers running 9.16.1 which
> stopped accepting new TCP connections after the tcp-clients quota was
> reached. This is indicated when running "rndc status" and checking "TCP
> high-water" or in the bind logs:
> 
> general: error: TCP connection failed: quota reached

I had some of these too, until I explicitly set this named option:

  tcp-listen-queue 20;

Looks like the default is 10. The way I interpret this parameter is
that this sets the *operating system* listen queue, i.e. the backlog
argument for the listen() system call.

After changing this to 20, I had no more of the "quota reached" log
messages.

Platform: FreeBSD 12.1 on 64 bit Intel.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no