check_include_file_concat_curl("libgen.h" HAVE_LIBGEN_H)
check_include_file("linux/tcp.h" HAVE_LINUX_TCP_H)
check_include_file("locale.h" HAVE_LOCALE_H)
-check_include_file("net/if.h" HAVE_NET_IF_H)
+check_include_file_concat_curl("net/if.h" HAVE_NET_IF_H) # sys/select.h (e.g. MS-DOS/Watt-32)
check_include_file_concat_curl("netdb.h" HAVE_NETDB_H)
check_include_file_concat_curl("netinet/in.h" HAVE_NETINET_IN_H)
check_include_file("netinet/in6.h" HAVE_NETINET_IN6_H)