MFC r317755, r317758

r317755:
Various Coverity fixes in ifconfig(8)

* Exit early if kldload(2) fails (1011259). This is the only change that
affects ifconfig's behavior.
* Close memory and resource leaks (1305624, 1305205, 1007100)
* Mark usage() as _Noreturn (1305806, 1305750)
* Fix some dereference after null checks (1011474, 270774)

Reported by: Coverity
CID: 1305624, 1305205, 1007100, 1305806, 1305750, 1011474,
CID: 270774, 1011259
Reviewed by: cem
Sponsored by: Spectra Logic Corp
Differential Revision: https://reviews.freebsd.org/D10587

r317758:
Unbreak ifconfig for mlx4en(4) after r317755

ifconfig doesn't correctly infer mlx interfaces' module names, so it will
attempt to load the mlx(4) module even when not necessary.

Reported by: rstone
X-MFC-With: 317755
Sponsored by: Spectra Logic Corp

MFC r299873

Use strlcpy() instead of strncpy() when copying ifname to ensure
that it is NUL terminated. Additional NUL padding is not required
for short names.

Use sizeof(destination) in a few places instead of IFNAMSIZ.

Cast afp->af_ridreq and afp->af_addreq to make the intent of
the code more obvious.

Reported by: Coverity
CID: 1009628, 1009630, 1009631, 1009632, 1009633, 1009635, 1009638
CID: 1009639, 1009640, 1009641, 1009642, 1009643, 1009644, 1009645
CID: 1009646, 1009647, 1010049, 1010050, 1010051, 1010052, 1010053
CID: 1010054, 1011293, 1011294, 1011295, 1011296, 1011297, 1011298
CID: 1011299, 1305821, 1351720, 1351721

MFC r288305:

Replace N #defines with nitems to simplify ifconfig code slightly

MFC r282805:

- Remove ND6_IFF_IGNORELOOP. This functionality was useless in practice
because a link where looped back NS messages are permanently observed
does not work with either NDP or ARP for IPv4.

- draft-ietf-6man-enhanced-dad is now RFC 7527.

Approved by: re (gjb)

MFC r261708, r261847, r268525, r274316, r274347, r275593,
r276844, r276847, r279531, r279559, r279564, r279676

A bunch of IPv6 fixes by melifaro, hrs and ae

Major changes:
Simplify nd6_output_lle()
Add refcounting to DAD and fix races and other errors
Implement Enhanced DAD algorithm for IPv6

Suggested by: ae
Tested by: Jason Wolfe <j at nitrology.com>
Sponsored by: Limelight Networks

MFC r271307:
Add the ability to set `prefer_source' flag to an IPv6 address.
It affects the IPv6 source address selection algorithm (RFC 6724)
and allows override the last rule ("longest matching prefix") for
choosing among equivalent addresses. The address with `prefer_source'
will be preferred source address.

MFC r268049:
Fix ifconfig to show pltime and vltime with -L option,
again after usage change from time_second to time_uptime.

PR: 188520
Submitted by: Guy Yur <guyyur__at__gmail.com>

MFC r282805:

- Remove ND6_IFF_IGNORELOOP. This functionality was useless in practice
because a link where looped back NS messages are permanently observed
does not work with either NDP or ARP for IPv4.

- draft-ietf-6man-enhanced-dad is now RFC 7527.

Approved by: re (gjb)

MFC r261708, r261847, r268525, r274316, r274347, r275593,
r276844, r276847, r279531, r279559, r279564, r279676

A bunch of IPv6 fixes by melifaro, hrs and ae

Major changes:
Simplify nd6_output_lle()
Add refcounting to DAD and fix races and other errors
Implement Enhanced DAD algorithm for IPv6

Suggested by: ae
Tested by: Jason Wolfe <j at nitrology.com>
Sponsored by: Limelight Networks

MFC r271307:
Add the ability to set `prefer_source' flag to an IPv6 address.
It affects the IPv6 source address selection algorithm (RFC 6724)
and allows override the last rule ("longest matching prefix") for
choosing among equivalent addresses. The address with `prefer_source'
will be preferred source address.

MFC r268049:
Fix ifconfig to show pltime and vltime with -L option,
again after usage change from time_second to time_uptime.

PR: 188520
Submitted by: Guy Yur <guyyur__at__gmail.com>