Files:
tests/test-net_if.c
tests/signature.h

Depends-on:
net_if-c++-tests

configure.ac:
NET_IF_LIB=
gl_saved_libs="$LIBS"
AC_SEARCH_LIBS([if_nameindex], [socket],
  [AC_DEFINE([HAVE_IF_NAMEINDEX], [1], [Define if you have if_nameindex.])
   if test "$ac_cv_search_if_nameindex" != "none required"; then
     NET_IF_LIB="$ac_cv_search_if_nameindex"
   fi])
LIBS="$gl_saved_libs"
AC_SUBST([NET_IF_LIB])

Makefile.am:
TESTS += test-net_if
check_PROGRAMS += test-net_if
test_net_if_LDADD = $(LDADD) @NET_IF_LIB@