selftests: net: udpgso_bench_tx: Cater for pending datagrams zerocopy benchmarking

The test tool can check that the zerocopy number of completions value is
valid taking into consideration the number of datagram send calls. This can
catch the system into a state where the datagrams are still in the system
(for example in a qdisk, waiting for the network interface to return a
completion notification, etc).

This change adds a retry logic of computing the number of completions up to
a configurable (via CLI) timeout (default: 2 seconds).

Fixes: 79ebc3c2 ("net/udpgso_bench_tx: options to exercise TX CMSG")
Signed-off-by: Andrei Gherzan <andrei.gherzan@canonical.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20230201001612.515730-4-andrei.gherzan@canonical.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

tools/testing/selftests/net/udpgso_bench_tx.c

@@ -62,6 +62,7 @@ static int	cfg_payload_len	= (1472 * 42);
 static int	cfg_port	= 8000;
 static int	cfg_runtime_ms	= -1;
 static bool	cfg_poll;
+static int	cfg_poll_loop_timeout_ms = 2000;
 static bool	cfg_segment;
 static bool	cfg_sendmmsg;
 static bool	cfg_tcp;
@@ -235,16 +236,17 @@ static void flush_errqueue_recv(int fd)
 	}
 }
 
-static void flush_errqueue(int fd, const bool do_poll)
+static void flush_errqueue(int fd, const bool do_poll,
+			   unsigned long poll_timeout, const bool poll_err)
 {
 	if (do_poll) {
 		struct pollfd fds = {0};
 		int ret;
 
 		fds.fd = fd;
-		ret = poll(&fds, 1, 500);
+		ret = poll(&fds, 1, poll_timeout);
 		if (ret == 0) {
-			if (cfg_verbose)
+			if ((cfg_verbose) && (poll_err))
 				fprintf(stderr, "poll timeout\n");
 		} else if (ret < 0) {
 			error(1, errno, "poll");
@@ -254,6 +256,20 @@ static void flush_errqueue(int fd, const bool do_poll)
 	flush_errqueue_recv(fd);
 }
 
+static void flush_errqueue_retry(int fd, unsigned long num_sends)
+{
+	unsigned long tnow, tstop;
+	bool first_try = true;
+
+	tnow = gettimeofday_ms();
+	tstop = tnow + cfg_poll_loop_timeout_ms;
+	do {
+		flush_errqueue(fd, true, tstop - tnow, first_try);
+		first_try = false;
+		tnow = gettimeofday_ms();
+	} while ((stat_zcopies != num_sends) && (tnow < tstop));
+}
+
 static int send_tcp(int fd, char *data)
 {
 	int ret, done = 0, count = 0;
@@ -413,7 +429,8 @@ static int send_udp_segment(int fd, char *data)
 
 static void usage(const char *filepath)
 {
-	error(1, 0, "Usage: %s [-46acmHPtTuvz] [-C cpu] [-D dst ip] [-l secs] [-M messagenr] [-p port] [-s sendsize] [-S gsosize]",
+	error(1, 0, "Usage: %s [-46acmHPtTuvz] [-C cpu] [-D dst ip] [-l secs] "
+		    "[-L secs] [-M messagenr] [-p port] [-s sendsize] [-S gsosize]",
 		    filepath);
 }
 
@@ -423,7 +440,7 @@ static void parse_opts(int argc, char **argv)
 	int max_len, hdrlen;
 	int c;
 
-	while ((c = getopt(argc, argv, "46acC:D:Hl:mM:p:s:PS:tTuvz")) != -1) {
+	while ((c = getopt(argc, argv, "46acC:D:Hl:L:mM:p:s:PS:tTuvz")) != -1) {
 		switch (c) {
 		case '4':
 			if (cfg_family != PF_UNSPEC)
@@ -452,6 +469,9 @@ static void parse_opts(int argc, char **argv)
 		case 'l':
 			cfg_runtime_ms = strtoul(optarg, NULL, 10) * 1000;
 			break;
+		case 'L':
+			cfg_poll_loop_timeout_ms = strtoul(optarg, NULL, 10) * 1000;
+			break;
 		case 'm':
 			cfg_sendmmsg = true;
 			break;
@@ -679,7 +699,7 @@ int main(int argc, char **argv)
 			num_sends += send_udp(fd, buf[i]);
 		num_msgs++;
 		if ((cfg_zerocopy && ((num_msgs & 0xF) == 0)) || cfg_tx_tstamp)
-			flush_errqueue(fd, cfg_poll);
+			flush_errqueue(fd, cfg_poll, 500, true);
 
 		if (cfg_msg_nr && num_msgs >= cfg_msg_nr)
 			break;
@@ -698,7 +718,7 @@ int main(int argc, char **argv)
 	} while (!interrupted && (cfg_runtime_ms == -1 || tnow < tstop));
 
 	if (cfg_zerocopy || cfg_tx_tstamp)
-		flush_errqueue(fd, true);
+		flush_errqueue_retry(fd, num_sends);
 
 	if (close(fd))
 		error(1, errno, "close");