netmgr: retry binding with IP_FREEBIND when EADDRNOTAVAIL is returned.

When a new IPv6 interface/address appears it's first in a tentative
state - in which we cannot bind to it, yet it's already being reported
by the route socket. Because of that BIND9 is unable to listen on any
newly detected IPv6 addresses. Fix it by setting IP_FREEBIND option (or
equivalent option on other OSes) and then retrying bind() call.

lib/isc/netmgr/netmgr-int.h

@@ -821,3 +821,9 @@ isc__nm_decstats(isc_nm_t *mgr, isc_statscounter_t counterid);
 /*%<
  * Decrement socket-related statistics counters.
  */
+
+isc_result_t
+isc__nm_socket_freebind(const uv_handle_t *handle);
+/*%<
+ * Set the IP_FREEBIND (or equivalent) socket option on the uv_handle
+ */

lib/isc/netmgr/netmgr.c

@@ -1519,3 +1519,54 @@ isc__nm_decstats(isc_nm_t *mgr, isc_statscounter_t counterid) {
 		isc_stats_decrement(mgr->stats, counterid);
 	}
 }
+
+#define setsockopt_on(socket, level, name) \
+	setsockopt(socket, level, name, &(int){ 1 }, sizeof(int))
+
+isc_result_t
+isc__nm_socket_freebind(const uv_handle_t *handle) {
+	/*
+	 * Set the IP_FREEBIND (or equivalent option) on the uv_handle.
+	 */
+	isc_result_t result = ISC_R_SUCCESS;
+	uv_os_fd_t fd;
+	if (uv_fileno(handle, &fd) != 0) {
+		return (ISC_R_FAILURE);
+	}
+#ifdef IP_FREEBIND
+	if (setsockopt_on(fd, IPPROTO_IP, IP_FREEBIND) == -1) {
+		return (ISC_R_FAILURE);
+	}
+#elif defined(IP_BINDANY) || defined(IPV6_BINDANY)
+	struct sockaddr_in sockfd;
+
+	if (getsockname(fd, (struct sockaddr *)&sockfd,
+			&(socklen_t){ sizeof(sockfd) }) == -1)
+	{
+		return (ISC_R_FAILURE);
+	}
+#if defined(IP_BINDANY)
+	if (sockfd.sin_family == AF_INET) {
+		if (setsockopt_on(fd, IPPROTO_IP, IP_BINDANY) == -1) {
+			return (ISC_R_FAILURE);
+		}
+	}
+#endif
+#if defined(IPV6_BINDANY)
+	if (sockfd.sin_family == AF_INET6) {
+		if (setsockopt_on(fd, IPPROTO_IPV6, IPV6_BINDANY) == -1) {
+			return (ISC_R_FAILURE);
+		}
+	}
+#endif
+#elif defined(SO_BINDANY)
+	if (setsockopt_on(fd, SOL_SOCKET, SO_BINDANY) == -1) {
+		return (ISC_R_FAILURE);
+	}
+#else
+	UNUSED(handle);
+	UNUSED(fd);
+	result = ISC_R_NOTIMPLEMENTED;
+#endif
+	return (result);
+}

lib/isc/netmgr/tcp.c

@@ -340,6 +340,19 @@ isc__nm_async_tcplisten(isc__networker_t *worker, isc__netievent_t *ev0) {
 
 	r = uv_tcp_bind(&sock->uv_handle.tcp, &sock->iface->addr.type.sa,
 			flags);
+	if (r == UV_EADDRNOTAVAIL &&
+	    isc__nm_socket_freebind(&sock->uv_handle.handle) == ISC_R_SUCCESS)
+	{
+		/*
+		 * Retry binding with IP_FREEBIND (or equivalent option) if the
+		 * address is not available. This helps with IPv6 tentative
+		 * addresses which are reported by the route socket, although
+		 * named is not yet able to properly bind to them.
+		 */
+		r = uv_tcp_bind(&sock->uv_handle.tcp,
+				&sock->iface->addr.type.sa, flags);
+	}
+
 	if (r != 0) {
 		isc__nm_incstats(sock->mgr, sock->statsindex[STATID_BINDFAIL]);
 		uv_close(&sock->uv_handle.handle, tcp_close_cb);

lib/isc/netmgr/udp.c

@@ -168,6 +168,20 @@ isc__nm_async_udplisten(isc__networker_t *worker, isc__netievent_t *ev0) {
 
 	r = uv_udp_bind(&sock->uv_handle.udp,
 			&sock->parent->iface->addr.type.sa, uv_bind_flags);
+	if (r == UV_EADDRNOTAVAIL &&
+	    isc__nm_socket_freebind(&sock->uv_handle.handle) == ISC_R_SUCCESS)
+	{
+		/*
+		 * Retry binding with IP_FREEBIND (or equivalent option) if the
+		 * address is not available. This helps with IPv6 tentative
+		 * addresses which are reported by the route socket, although
+		 * named is not yet able to properly bind to them.
+		 */
+		r = uv_udp_bind(&sock->uv_handle.udp,
+				&sock->parent->iface->addr.type.sa,
+				uv_bind_flags);
+	}
+
 	if (r < 0) {
 		isc__nm_incstats(sock->mgr, sock->statsindex[STATID_BINDFAIL]);
 	}