[net-next] selftests: net: verify fq per-band packet limit

diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index 5b2aca4c5f10..9274edfb76ff 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -91,6 +91,7 @@  TEST_PROGS += test_bridge_neigh_suppress.sh
 TEST_PROGS += test_vxlan_nolocalbypass.sh
 TEST_PROGS += test_bridge_backup_port.sh
 TEST_PROGS += fdb_flush.sh
+TEST_PROGS += fq_band_pktlimit.sh
 
 TEST_FILES := settings
 
diff --git a/tools/testing/selftests/net/cmsg_sender.c b/tools/testing/selftests/net/cmsg_sender.c
index 24b21b15ed3f..8d7575389f58 100644
--- a/tools/testing/selftests/net/cmsg_sender.c
+++ b/tools/testing/selftests/net/cmsg_sender.c
@@ -45,11 +45,13 @@  struct options {
 	const char *host;
 	const char *service;
 	unsigned int size;
+	unsigned int num_pkt;
 	struct {
 		unsigned int mark;
 		unsigned int dontfrag;
 		unsigned int tclass;
 		unsigned int hlimit;
+		unsigned int priority;
 	} sockopt;
 	struct {
 		unsigned int family;
@@ -72,6 +74,7 @@  struct options {
 	} v6;
 } opt = {
 	.size = 13,
+	.num_pkt = 1,
 	.sock = {
 		.family	= AF_UNSPEC,
 		.type	= SOCK_DGRAM,
@@ -112,7 +115,7 @@  static void cs_parse_args(int argc, char *argv[])
 {
 	int o;
 
-	while ((o = getopt(argc, argv, "46sS:p:m:M:d:tf:F:c:C:l:L:H:")) != -1) {
+	while ((o = getopt(argc, argv, "46sS:p:P:m:M:n:d:tf:F:c:C:l:L:H:")) != -1) {
 		switch (o) {
 		case 's':
 			opt.silent_send = true;
@@ -138,7 +141,9 @@  static void cs_parse_args(int argc, char *argv[])
 				cs_usage(argv[0]);
 			}
 			break;
-
+		case 'P':
+			opt.sockopt.priority = atoi(optarg);
+			break;
 		case 'm':
 			opt.mark.ena = true;
 			opt.mark.val = atoi(optarg);
@@ -146,6 +151,9 @@  static void cs_parse_args(int argc, char *argv[])
 		case 'M':
 			opt.sockopt.mark = atoi(optarg);
 			break;
+		case 'n':
+			opt.num_pkt = atoi(optarg);
+			break;
 		case 'd':
 			opt.txtime.ena = true;
 			opt.txtime.delay = atoi(optarg);
@@ -410,6 +418,10 @@  static void ca_set_sockopts(int fd)
 	    setsockopt(fd, SOL_IPV6, IPV6_UNICAST_HOPS,
 		       &opt.sockopt.hlimit, sizeof(opt.sockopt.hlimit)))
 		error(ERN_SOCKOPT, errno, "setsockopt IPV6_HOPLIMIT");
+	if (opt.sockopt.priority &&
+	    setsockopt(fd, SOL_SOCKET, SO_PRIORITY,
+		       &opt.sockopt.priority, sizeof(opt.sockopt.priority)))
+		error(ERN_SOCKOPT, errno, "setsockopt SO_PRIORITY");
 }
 
 int main(int argc, char *argv[])
@@ -421,6 +433,7 @@  int main(int argc, char *argv[])
 	char *buf;
 	int err;
 	int fd;
+	int i;
 
 	cs_parse_args(argc, argv);
 
@@ -480,24 +493,27 @@  int main(int argc, char *argv[])
 
 	cs_write_cmsg(fd, &msg, cbuf, sizeof(cbuf));
 
-	err = sendmsg(fd, &msg, 0);
-	if (err < 0) {
-		if (!opt.silent_send)
-			fprintf(stderr, "send failed: %s\n", strerror(errno));
-		err = ERN_SEND;
-		goto err_out;
-	} else if (err != (int)opt.size) {
-		fprintf(stderr, "short send\n");
-		err = ERN_SEND_SHORT;
-		goto err_out;
-	} else {
-		err = ERN_SUCCESS;
+	for (i = 0; i < opt.num_pkt; i++) {
+		err = sendmsg(fd, &msg, 0);
+		if (err < 0) {
+			if (!opt.silent_send)
+				fprintf(stderr, "send failed: %s\n", strerror(errno));
+			err = ERN_SEND;
+			goto err_out;
+		} else if (err != (int)opt.size) {
+			fprintf(stderr, "short send\n");
+			err = ERN_SEND_SHORT;
+			goto err_out;
+		}
 	}
+	err = ERN_SUCCESS;
 
-	/* Make sure all timestamps have time to loop back */
-	usleep(opt.txtime.delay);
+	if (opt.ts.ena) {
+		/* Make sure all timestamps have time to loop back */
+		usleep(opt.txtime.delay);
 
-	cs_read_cmsg(fd, &msg, cbuf, sizeof(cbuf));
+		cs_read_cmsg(fd, &msg, cbuf, sizeof(cbuf));
+	}
 
 err_out:
 	close(fd);
diff --git a/tools/testing/selftests/net/fq_band_pktlimit.sh b/tools/testing/selftests/net/fq_band_pktlimit.sh
new file mode 100755
index 000000000000..24b77bdf41ff
--- /dev/null
+++ b/tools/testing/selftests/net/fq_band_pktlimit.sh
@@ -0,0 +1,57 @@ 
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Verify that FQ has a packet limit per band:
+#
+# 1. set the limit to 10 per band
+# 2. send 20 pkts on band A: verify that 10 are queued, 10 dropped
+# 3. send 20 pkts on band A: verify that  0 are queued, 20 dropped
+# 4. send 20 pkts on band B: verify that 10 are queued, 10 dropped
+#
+# Send packets with a 100ms delay to ensure that previously sent
+# packets are still queued when later ones are sent.
+# Use SO_TXTIME for this.
+
+die() {
+	echo "$1"
+	exit 1
+}
+
+# run inside private netns
+if [[ $# -eq 0 ]]; then
+	./in_netns.sh "$0" __subprocess
+	exit
+fi
+
+ip link add type dummy
+ip link set dev dummy0 up
+ip -6 addr add fdaa::1/128 dev dummy0
+ip -6 route add fdaa::/64 dev dummy0
+tc qdisc replace dev dummy0 root handle 1: fq quantum 1514 initial_quantum 1514 limit 10
+
+./cmsg_sender -6 -p u -d 100000 -n 20 fdaa::2 8000
+OUT1="$(tc -s qdisc show dev dummy0 | grep '^\ Sent')"
+
+./cmsg_sender -6 -p u -d 100000 -n 20 fdaa::2 8000
+OUT2="$(tc -s qdisc show dev dummy0 | grep '^\ Sent')"
+
+./cmsg_sender -6 -p u -d 100000 -n 20 -P 7 fdaa::2 8000
+OUT3="$(tc -s qdisc show dev dummy0 | grep '^\ Sent')"
+
+# Initial stats will report zero sent, as all packets are still
+# queued in FQ. Sleep for the delay period (100ms) and see that
+# twenty are now sent.
+sleep 0.1
+OUT4="$(tc -s qdisc show dev dummy0 | grep '^\ Sent')"
+
+# Log the output after the test
+echo "${OUT1}"
+echo "${OUT2}"
+echo "${OUT3}"
+echo "${OUT4}"
+
+# Test the output for expected values
+echo "${OUT1}" | grep -q '0\ pkt\ (dropped\ 10'  || die "unexpected drop count at 1"
+echo "${OUT2}" | grep -q '0\ pkt\ (dropped\ 30'  || die "unexpected drop count at 2"
+echo "${OUT3}" | grep -q '0\ pkt\ (dropped\ 40'  || die "unexpected drop count at 3"
+echo "${OUT4}" | grep -q '20\ pkt\ (dropped\ 40' || die "unexpected accept count at 4"