dns.c: Load IPv6 DNS resolvers if configured.

IPv6 nameserver addresses are stored in different part of the
__res_state structure, so look there if we appear to have support for
it.

ASTERISK-28004 #close

Change-Id: I67067077d8a406ee996664518d9c8fbf11f6977d

configure

@@ -18657,6 +18657,17 @@ $as_echo "no" >&6; }
 fi
 rm -f core conftest.err conftest.$ac_objext \
     conftest$ac_exeext conftest.$ac_ext
+	ac_fn_c_check_member "$LINENO" "struct __res_state" "_u._ext.nsaddrs" "ac_cv_member_struct___res_state__u__ext_nsaddrs" "#include <resolv.h>
+"
+if test "x$ac_cv_member_struct___res_state__u__ext_nsaddrs" = xyes; then :
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_STRUCT___RES_STATE__U__EXT_NSADDRS 1
+_ACEOF
+
+
+fi
+
 else
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }

configure.ac

@@ -1459,7 +1459,8 @@ AC_LINK_IFELSE(
 		AC_MSG_RESULT(yes)
 		AC_DEFINE([HAVE_RES_CLOSE], 1, [Define to 1 if your system has the close resolver function.]),
 		AC_MSG_RESULT(no)
-	),
+	)
+	AC_CHECK_MEMBERS([struct __res_state._u._ext.nsaddrs], [], [], [[#include <resolv.h>]]),
 	AC_MSG_RESULT(no)
 )
 

include/asterisk/autoconfig.h.in

@@ -1052,6 +1052,9 @@
 /* Define to 1 if `uid' is a member of `struct ucred'. */
 #undef HAVE_STRUCT_UCRED_UID
 
+/* Define to 1 if `_u._ext.nsaddrs' is a member of `struct __res_state'. */
+#undef HAVE_STRUCT___RES_STATE__U__EXT_NSADDRS
+
 /* Define to 1 if you have the `swapctl' function. */
 #undef HAVE_SWAPCTL
 

main/dns.c

@@ -605,7 +605,22 @@ struct ao2_container *ast_dns_get_nameservers(void)
 #endif
 
 	for (i = 0; i < state->nscount; i++) {
-		ast_str_container_add(nameservers, ast_inet_ntoa(state->nsaddr_list[i].sin_addr));
+		char addr[INET6_ADDRSTRLEN];
+		const char *addrp = NULL;
+
+		/* glibc sets sin_family to 0 when the nameserver is an IPv6 address */
+		if (state->nsaddr_list[i].sin_family) {
+			addrp = inet_ntop(AF_INET, &state->nsaddr_list[i].sin_addr, addr, sizeof(addr));
+#if defined(HAVE_RES_NINIT) && defined(HAVE_STRUCT___RES_STATE__U__EXT_NSADDRS)
+		} else if (state->_u._ext.nsaddrs[i]) {
+			addrp = inet_ntop(AF_INET6, &state->_u._ext.nsaddrs[i]->sin6_addr, addr, sizeof(addr));
+#endif
+		}
+
+		if (addrp) {
+			ast_debug(1, "Discovered nameserver: %s\n", addrp);
+			ast_str_container_add(nameservers, addrp);
+		}
 	}
 
 #ifdef HAVE_RES_NINIT