syscall: support FreeBSD 10

[mikioh]

A few network interface APIs don't work on 32-bit FreeBSD 10, freebsd/386 and arm.

Looks like they changed if_data (see /usr/include/net/if.h) that is required to fetch
network interface facility information from the kernel. Seems they have a long term plan
to introduce TLV-style data representation over routing socket like netlink stuff, but
not in FreeBSD 10 (and probably 11).

We need to re-define if_data and also keep previous if_data internally, and then handle
both appropriately by using if_msghdrl (the 'l' version) instead of conventional
if_msghdr.

[mikioh]

Comment 2:

https://golang.org/cl/56770044/
https://golang.org/cl/56920043/
https://golang.org/cl/56930043/
https://golang.org/cl/56980043/
https://golang.org/cl/57210043/

[mikioh]

Comment 3:

Issue #7332 has been merged into this issue.

[mikioh]

Comment 4:

https://groups.google.com/d/msg/golang-dev/CSr0d5EIB4s/C2GapgkHH-YJ

[mikioh]

Comment 5:

The approach has beed slightly changed:
https://golang.org/cl/56770044/
https://golang.org/cl/56980043/
https://golang.org/cl/57210043/

[mikioh]

Comment 6:

This issue was updated by revision 737efeb.

FreeBSD 10 breaking changes:
r205792: Rename st_*timespec fields to st_*tim for POSIX 2008
compliance.
http://svnweb.freebsd.org/base?view=revision&revision=205792
r254804: Restructure the mbuf pkthdr to make it fit for upcoming
capabilities and features.
http://svnweb.freebsd.org/base?view=revision&revision=254804
r255219: Change the cap_rights_t type from uint64_t to a structure
that we can extend in the future in a backward compatible (API and
ABI) way.
http://svnweb.freebsd.org/base?view=revision&revision=255219
LGTM=iant
R=golang-codereviews, rsc, minux.ma, gobot, iant
CC=golang-codereviews
https://golang.org/cl/56770044

[mikioh]

Comment 7:

This issue was updated by revision d30d429.

LGTM=minux.ma
R=golang-codereviews, rsc, minux.ma, iant
CC=golang-codereviews
https://golang.org/cl/57210043

[mikioh]

Comment 8:

This issue was closed by revision 25668b9.

Status changed to Fixed.

[mikioh]

Comment 9:

This issue was updated by revision be8aa4b.

LGTM=bradfitz
R=golang-codereviews, dave, rsc, minux.ma, bradfitz
CC=golang-codereviews
https://golang.org/cl/64510043