Bug#327031: ifdown routine only works on Linux

[Petter Reinholdtsen]

[Robert Millan, 2005-09-15]
> Please let us know if you find out :)

I've consulted "UNIX Network programming" by Stevens, and found useful
info on the ifconf and ifreq struct in section 16.5 (page 428 and
429).  It claims that the <net/if.h> header is expected to have an
ifr_flags define to access the interface flags.  A quick look in the
POSIX standard, did not give any references, so I suspect these
structs are undefined by POSIX.  But as the Stevens books have
authority in the UNIX world, I would recommend having the kFreeBSD
headers fixed to confirm to the <net/if.h> content described in "UNIX
Network Programming".

> Please use the one I'm attaching instead.

I'll include it, with some comment about the misfeature with the
kFreeBSD header files.