daemon: check source in udp answer

daemon/io.c

@@ -160,6 +160,12 @@ void udp_recv(uv_udp_t *handle, ssize_t nread, const uv_buf_t *buf,
 	if (addr->sa_family == AF_UNSPEC) {
 		return;
 	}
+	if (s->outgoing) {
+		assert(s->peer.ip.sa_family != AF_UNSPEC);
+		if (kr_sockaddr_cmp(&s->peer.ip, addr) != 0) {
+			return;
+		}
+	}
 	knot_pkt_t *query = knot_pkt_new(buf->base, nread, &worker->pkt_pool);
 	if (query) {
 		query->max_size = KNOT_WIRE_MAX_PKTSIZE;

daemon/worker.c

@@ -1384,8 +1384,15 @@ static uv_handle_t *retransmit(struct qr_task *task)
 			return ret;
 		}
 		ret = ioreq_spawn(task, SOCK_DGRAM, choice->sin6_family);
-		if (ret &&
-		    qr_task_send(task, ret, (struct sockaddr *)choice,
+		if (!ret) {
+			return ret;
+		}
+		struct sockaddr *addr = (struct sockaddr *)choice;
+		struct session *session = ret->data;
+		assert (session->peer.ip.sa_family == AF_UNSPEC);
+		session->outgoing = true;
+		memcpy(&session->peer, addr, sizeof(session->peer));
+		if (qr_task_send(task, ret, (struct sockaddr *)choice,
 				 task->pktbuf) == 0) {
 			task->addrlist_turn = (task->addrlist_turn + 1) %
 					      task->addrlist_count; /* Round robin */

lib/utils.c

@@ -365,6 +365,33 @@ int kr_sockaddr_len(const struct sockaddr *addr)
 	}
 }
 
+int kr_sockaddr_cmp(const struct sockaddr *left, const struct sockaddr *right)
+{
+	if (!left || !right) {
+		return kr_error(EINVAL);
+	}
+	if (left->sa_family != right->sa_family) {
+		return kr_error(EFAULT);
+	}
+	if (left->sa_family == AF_INET) {
+		struct sockaddr_in *left_in = (struct sockaddr_in *)left;
+		struct sockaddr_in *right_in = (struct sockaddr_in *)right;
+		if (left_in->sin_addr.s_addr != right_in->sin_addr.s_addr) {
+			return kr_error(EFAULT);
+		}
+	} else if (left->sa_family == AF_INET6) {
+		struct sockaddr_in6 *left_in6 = (struct sockaddr_in6 *)left;
+		struct sockaddr_in6 *right_in6 = (struct sockaddr_in6 *)right;
+		if (memcmp(&left_in6->sin6_addr, &right_in6->sin6_addr,
+			   sizeof(struct in6_addr)) != 0) {
+			return kr_error(EFAULT);
+		}
+	} else {
+		return kr_error(ENOENT);
+	}
+	return kr_ok();
+}
+
 uint16_t kr_inaddr_port(const struct sockaddr *addr)
 {
 	if (!addr) {

lib/utils.h

@@ -233,6 +233,11 @@ int kr_inaddr_len(const struct sockaddr *addr);
 /** Sockaddr length for given family, i.e. sizeof(struct sockaddr_in*). */
 KR_EXPORT KR_PURE
 int kr_sockaddr_len(const struct sockaddr *addr);
+/** Compare two given sockaddr.
+ * return 0 - addresses are equal, error code otherwise.
+ */
+KR_EXPORT KR_PURE
+int kr_sockaddr_cmp(const struct sockaddr *left, const struct sockaddr *right);
 /** Port. */
 KR_EXPORT KR_PURE
 uint16_t kr_inaddr_port(const struct sockaddr *addr);