[nrf fromlist] net: zperf: Improve UDP multicast upload

UDP multicast uploads did not produce zperf-compatible server stats,
so the client waited for and tried to decode a non-existent reply,
causing “Unexpected response flags” and misleading
“LAST PACKET NOT RECEIVED!!!” output.

This change treats multicast as client-only: after sending
the negative-id FIN it does not wait for or decode server stats,
Instead transmits the FIN a few times to help receivers detect test end.
The shell prints a clear “Statistics (client only)” summary for multicast
and suppresses the error when client stats are valid.

Unicast behavior is unchanged.

Upstream PR #: 94344

Signed-off-by: Kapil Bhatt <[email protected]>

Author: kapbh

include/zephyr/net/zperf.h

@@ -90,6 +90,7 @@ struct zperf_results {
 	uint64_t client_time_in_us;   /**< Client connection time in microseconds */
 	uint32_t packet_size;         /**< Packet size */
 	uint32_t nb_packets_errors;   /**< Number of packet errors */
+	bool is_multicast;            /**< True if this session used IP multicast */
 };
 
 /**

subsys/net/lib/zperf/zperf_shell.c

@@ -516,41 +516,56 @@ static void shell_udp_upload_print_stats(const struct shell *sh,
 			client_rate_in_kbps = 0U;
 		}
 
-		if (!rate_in_kbps) {
+		/* Print warning if no server stats in unicast case; for multicast,
+		 * server stats are not expected.
+		 */
+		if (!rate_in_kbps && !results->is_multicast) {
 			shell_fprintf(sh, SHELL_ERROR,
 				      "LAST PACKET NOT RECEIVED!!!\n");
 		}
 
-		shell_fprintf(sh, SHELL_NORMAL,
-			      "Statistics:\t\tserver\t(client)\n");
-		shell_fprintf(sh, SHELL_NORMAL, "Duration:\t\t");
-		print_number_64(sh, results->time_in_us, TIME_US,
-			     TIME_US_UNIT);
-		shell_fprintf(sh, SHELL_NORMAL, "\t(");
-		print_number_64(sh, results->client_time_in_us, TIME_US,
-			     TIME_US_UNIT);
-		shell_fprintf(sh, SHELL_NORMAL, ")\n");
-
-		shell_fprintf(sh, SHELL_NORMAL, "Num packets:\t\t%u\t(%u)\n",
-			      results->nb_packets_rcvd,
-			      results->nb_packets_sent);
-
-		shell_fprintf(sh, SHELL_NORMAL,
-			      "Num packets out order:\t%u\n",
-			      results->nb_packets_outorder);
-		shell_fprintf(sh, SHELL_NORMAL, "Num packets lost:\t%u\n",
-			      results->nb_packets_lost);
-
-		shell_fprintf(sh, SHELL_NORMAL, "Jitter:\t\t\t");
-		print_number(sh, results->jitter_in_us, TIME_US,
-			     TIME_US_UNIT);
-		shell_fprintf(sh, SHELL_NORMAL, "\n");
+		if (results->is_multicast) {
+			shell_fprintf(sh, SHELL_NORMAL, "Statistics (client only)\n");
+			shell_fprintf(sh, SHELL_NORMAL, "Duration:\t\t");
+			print_number_64(sh, results->client_time_in_us, TIME_US, TIME_US_UNIT);
+			shell_fprintf(sh, SHELL_NORMAL, "\n");
+			shell_fprintf(sh, SHELL_NORMAL, "Num packets:\t\t%u\n",
+					results->nb_packets_sent);
+			shell_fprintf(sh, SHELL_NORMAL, "Rate:\t\t\t");
+			print_number(sh, client_rate_in_kbps, KBPS, KBPS_UNIT);
+			shell_fprintf(sh, SHELL_NORMAL, "\n");
+		} else {
+			shell_fprintf(sh, SHELL_NORMAL,
+					"Statistics:\t\tserver\t(client)\n");
+			shell_fprintf(sh, SHELL_NORMAL, "Duration:\t\t");
+			print_number_64(sh, results->time_in_us, TIME_US,
+					TIME_US_UNIT);
+			shell_fprintf(sh, SHELL_NORMAL, "\t(");
+			print_number_64(sh, results->client_time_in_us, TIME_US,
+					TIME_US_UNIT);
+			shell_fprintf(sh, SHELL_NORMAL, ")\n");
+
+			shell_fprintf(sh, SHELL_NORMAL, "Num packets:\t\t%u\t(%u)\n",
+					results->nb_packets_rcvd,
+					results->nb_packets_sent);
 
-		shell_fprintf(sh, SHELL_NORMAL, "Rate:\t\t\t");
-		print_number(sh, rate_in_kbps, KBPS, KBPS_UNIT);
-		shell_fprintf(sh, SHELL_NORMAL, "\t(");
-		print_number(sh, client_rate_in_kbps, KBPS, KBPS_UNIT);
-		shell_fprintf(sh, SHELL_NORMAL, ")\n");
+			shell_fprintf(sh, SHELL_NORMAL,
+					"Num packets out order:\t%u\n",
+					results->nb_packets_outorder);
+			shell_fprintf(sh, SHELL_NORMAL, "Num packets lost:\t%u\n",
+					results->nb_packets_lost);
+
+			shell_fprintf(sh, SHELL_NORMAL, "Jitter:\t\t\t");
+			print_number(sh, results->jitter_in_us, TIME_US,
+					TIME_US_UNIT);
+			shell_fprintf(sh, SHELL_NORMAL, "\n");
+
+			shell_fprintf(sh, SHELL_NORMAL, "Rate:\t\t\t");
+			print_number(sh, rate_in_kbps, KBPS, KBPS_UNIT);
+			shell_fprintf(sh, SHELL_NORMAL, "\t(");
+			print_number(sh, client_rate_in_kbps, KBPS, KBPS_UNIT);
+			shell_fprintf(sh, SHELL_NORMAL, ")\n");
+		}
 
 #ifdef CONFIG_ZPERF_SESSION_PER_THREAD
 		if (is_async) {

subsys/net/lib/zperf/zperf_udp_uploader.c

@@ -105,10 +105,14 @@ static inline int zperf_upload_fin(int sock,
 			continue;
 		}
 
-		/* Multicast only send the negative sequence number packet
-		 * and doesn't wait for a server ack
+		/* For multicast, do not wait for a server ack. Keep resending FIN
+		 * for the configured number of attempts by forcing another loop
+		 * iteration.
 		 */
-		if (!is_mcast_pkt) {
+		if (is_mcast_pkt) {
+			ret = 0;
+			continue;
+		} else {
 			/* Receive statistics */
 			ret = zsock_setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, &rcvtimeo,
 					       sizeof(rcvtimeo));
@@ -126,6 +130,11 @@ static inline int zperf_upload_fin(int sock,
 		}
 	}
 
+	/* In multicast, we never expect a stats reply. Stop here. */
+	if (is_mcast_pkt) {
+		return 0;
+	}
+
 	/* Decode statistics */
 	if (ret > 0) {
 		zperf_upload_decode_stat(stats, ret, results);
@@ -299,6 +308,7 @@ static int udp_upload(int sock, int port,
 	results->client_time_in_us =
 				k_ticks_to_us_ceil64(end_time - start_time);
 	results->packet_size = packet_size;
+	results->is_multicast = is_mcast_pkt;
 
 	return 0;
 }