UDP6 locking improvement

[Bjoern A. Zeeb]

Hi,

based on some work I have done a few years back I have updated an UDP6 locking change and it’s at the “it compiles” stage.  I have not re-read it yet.  I’ll have to split it up into a couple of changes for PB as it also fixes:
- some UDP-Lite bug(s)
- some control mbuf leak
- something else I forgot already

and then re-post the rest into PB as well.


The old description in p4 was like:

! MFp4 bz_ipv6_fast:
!
!   Migrate udp6_send v4mapped code to udp6_output saving us a re-lock and
!   further simplifying the af handling code by eliminating AF_INET checks
!   at the tail end of the function.
!
!   Rework output path locking similar to UDP4 allowing for better
!   parallelism (see r222488).
!
!   Cleanup early initializations, comments, …
!
!   Sponsored by:       The FreeBSD Foundation
!   Sponsored by:       iXsystems


The new version is here:

https://people.freebsd.org/~bz/20150828-01-udp6-locking.diff

Anyone who wants to give it a read-through or bashing it through a pps framework is welcome!   I’ll try to do some of that hopefully over the weekend myself.

Bjoern