net_if: new module OpenBSD's <net/if.h> is not self-contained; this should compile: | #define _POSIX_C_SOURCE 200809L | #include <net/if.h> | struct if_nameindex i; but fails with: In file included from foo.c:2: /usr/include/net/if.h:112: error: expected specifier-qualifier-list before 'u_int' ... /usr/include/net/if.h:674: error: field 'dstaddr' has incomplete type In file included from /usr/include/net/if.h:691, from foo.c:2: /usr/include/net/if_arp.h:79: error: field 'arp_pa' has incomplete type /usr/include/net/if_arp.h:80: error: field 'arp_ha' has incomplete type *** Error code 1 We already had a test program for systems with the if_* functions (including OpenBSD); but in adding this module, I had to enhance that test to also work on platforms like mingw where we are now providing a new header. * modules/net_if: New module, borrowing ideas from netinet_in. * m4/net_if_h.m4: New file. * lib/net_if.in.h: Likewise. * doc/posix-headers/net_if.texi (net/if.h): Document it. * MODULES.html.sh (lacking POSIX:2008): Likewise. * tests/test-net_if.c: Make function checks conditional. Reported by Jasper Lievisse Adriaanse <jasper@humppa.nl>. Signed-off-by: Eric Blake <eblake@redhat.com>