Check for sys/sockio.h in configure and include sys/sockio.h in tcpip.cc. This is where SIOCGIFCONF is on Solaris 9.

configure

@@ -3735,7 +3735,8 @@ done
 
 
 
-for ac_header in pwd.h termios.h
+
+for ac_header in pwd.h termios.h sys/sockio.h
 do
 as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
 if eval "test \"\${$as_ac_Header+set}\" = set"; then

configure.ac

@@ -166,7 +166,7 @@ esac
 AC_SUBST(LUAFLAGS)
 
 dnl Checks for header files.
-AC_CHECK_HEADERS(pwd.h termios.h)
+AC_CHECK_HEADERS(pwd.h termios.h sys/sockio.h)
 
 dnl If any socket libraries needed
 AC_SEARCH_LIBS(setsockopt, socket)

tcpip.cc

@@ -117,6 +117,10 @@
 #include <sys/resource.h>
 #endif
 
+#if HAVE_SYS_SOCKIO_H
+#include <sys/sockio.h>
+#endif
+
 #if HAVE_UNISTD_H
 /* #include <sys/unistd.h> */
 #include <unistd.h>