net: lib: sntp: async query API

Add a variant of the SNTP API that does not block while waiting for a
response from the SNTP server. Instead it takes advantage of
`CONFIG_NET_SOCKETS_SERVICE` to read the response asynchronously when
the response is received.

Signed-off-by: Jordan Yates <[email protected]>

Author: JordanYates

include/zephyr/net/sntp.h

@@ -14,6 +14,7 @@
 #define ZEPHYR_INCLUDE_NET_SNTP_H_
 
 #include <zephyr/net/socket.h>
+#include <zephyr/net/socket_service.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -99,6 +100,52 @@ int sntp_recv_response(struct sntp_ctx *ctx, uint32_t timeout, struct sntp_time
  */
 void sntp_close(struct sntp_ctx *ctx);
 
+/**
+ * @brief Initialise SNTP context for async operation
+ *
+ * Asynchronous operation is powered by @kconfig{CONFIG_NET_SOCKETS_SERVICE}.
+ *
+ * @param service Socket service defined by @ref NET_SOCKET_SERVICE_SYNC_DEFINE
+ * @param ctx Address of sntp context.
+ * @param addr IP address of NTP/SNTP server.
+ * @param addr_len IP address length of NTP/SNTP server.
+ *
+ * @return 0 if ok, <0 if error.
+ */
+int sntp_init_async(const struct net_socket_service_desc *service,
+		    struct sntp_ctx *ctx, struct sockaddr *addr,
+		    socklen_t addr_len);
+
+/**
+ * @brief Send the SNTP query
+ *
+ * @param ctx Address of sntp context.
+ *
+ * @return 0 if ok, <0 if error.
+ */
+int sntp_send_async(struct sntp_ctx *ctx);
+
+/**
+ * @brief Read the result of the SNTP query
+ *
+ * Must be called from the callback attached to the @ref net_socket_service_desc
+ * context.
+ *
+ * @param event Event pointer extracted from the service work callback
+ * @param time Timestamp including integer and fractional seconds since
+ * 1 Jan 1970 (output).
+ *
+ * @return 0 if ok, <0 if error
+ */
+int sntp_read_async(struct net_socket_service_event *event, struct sntp_time *time);
+
+/**
+ * @brief Release SNTP context
+ *
+ * @param service Socket service defined by @ref NET_SOCKET_SERVICE_SYNC_DEFINE
+ */
+void sntp_close_async(const struct net_socket_service_desc *service);
+
 /**
  * @brief Convenience function to query SNTP in one-shot fashion
  *

subsys/net/lib/sntp/sntp.c

@@ -254,3 +254,72 @@ void sntp_close(struct sntp_ctx *ctx)
 		(void)zsock_close(ctx->sock.fd);
 	}
 }
+
+#ifdef CONFIG_NET_SOCKETS_SERVICE
+
+int sntp_init_async(const struct net_socket_service_desc *service, struct sntp_ctx *ctx,
+		    struct sockaddr *addr, socklen_t addr_len)
+{
+	int ret;
+
+	/* Standard init */
+	ret = sntp_init(ctx, addr, addr_len);
+	if (ret < 0) {
+		return ret;
+	}
+	/* Attach socket to socket service */
+	ret = net_socket_service_register(service, ctx->sock.fds, ctx->sock.nfds, ctx);
+	if (ret < 0) {
+		NET_ERR("Failed to register socket %d", ret);
+		/* Cleanup init on register failure*/
+		sntp_close(ctx);
+	}
+	return ret;
+}
+
+int sntp_send_async(struct sntp_ctx *ctx)
+{
+	int ret = 0;
+
+	if (!ctx) {
+		return -EFAULT;
+	}
+
+	ret = sntp_query_send(ctx);
+	if (ret < 0) {
+		NET_ERR("Failed to send over UDP socket %d", ret);
+		return ret;
+	}
+	return 0;
+}
+
+int sntp_read_async(struct net_socket_service_event *event, struct sntp_time *time)
+{
+	struct sntp_ctx *ctx = event->user_data;
+	struct sntp_pkt buf = {0};
+	int rcvd;
+
+	rcvd = zsock_recv(ctx->sock.fd, (uint8_t *)&buf, sizeof(buf), 0);
+	if (rcvd < 0) {
+		return -errno;
+	}
+
+	if (rcvd != sizeof(struct sntp_pkt)) {
+		return -EMSGSIZE;
+	}
+
+	return parse_response((uint8_t *)&buf, sizeof(buf), &ctx->expected_orig_ts, time);
+}
+
+void sntp_close_async(const struct net_socket_service_desc *service)
+{
+	struct sntp_ctx *ctx = service->pev->user_data;
+	/* Detach socket from socket service */
+	net_socket_service_unregister(service);
+	/* CLose the socket */
+	if (ctx) {
+		(void)zsock_close(ctx->sock.fd);
+	}
+}
+
+#endif /* CONFIG_NET_SOCKETS_SERVICE */