We have no use for the udphdr or this hlen local, just spell out the
addition inline.

MFC after:	3 days
Reviewed by:	grehan, markj
Differential Revision:	https://reviews.freebsd.org/D29142

This partially reverts df554850 but still fixes the leak. It was
overlooked (sigh) that some packets will exceed MHLEN and cannot be
physically contiguous without clustering, but we don't actually need
it to be. m_defrag() should pull up enough for any of the headers that
we do need to be accessible.

Fixes:	df554850
Pointy hat;	kevans

df554850 fixed a leak that I had initially fixed in a11009dc.

Fixes:	a11009dc

MFC after:	1 week
Sponsored by:	The FreeBSD Foundation

Reviewed by:	grehan
Sponsored by:	The FreeBSD Foundation
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D29011

m_defrag() will not free the chain on failure, leaking the mbuf.

Obtained from:	OpenBSD
MFC after:	3 days

Merge the following fixes from https://github.com/pfsense/FreeBSD-src
 1940e7d3  Save	address	of ingress packets to allow wg to work on HA
 8f5531f1  Fix connection to IPv6 endpoint
 825ed9ee  Fix tcpdump for wg IPv6 rx tunnel traffic
 2ec232d3  Fix issue with replying to INITIATION messages in server mode
 ec77593a  Return immediately in wg_init if in DETACH'd state
 0f0dde6f  Remove unnecessary wg debug printf on transmit
 2766dc94  Detect and fix case in wg_init() where sockets weren't cleaned up
 b62cc7ac  Close the UDP tunnel sockets when the interface has been stopped

Reviewed by:	kevans
Obtained from:	pfSense 2.5
MFC after:	3 days
Relnotes:	yes
Sponsored by:	Rubicon Communications, LLC ("Netgate")
Differential Revision:	https://reviews.freebsd.org/D28962

 - remove -ferror-limit option
 - quiet -Wredundant-decls

Reviewed by:	mmacy
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D27559

Data path largely shared with the OpenBSD implementation by
Matt Dunwoodie <ncon@nconroy.net>

Reviewed by:	grehan@freebsd.org
MFC after:	1 month
Sponsored by:	Rubicon LLC, (Netgate)
Differential Revision:	https://reviews.freebsd.org/D26137