Subject: [PATCH net-next v5 3/3] selftests: drv-net: convert so_txtime to drv-net

From: Willem de Bruijn <[email-masked]>
Date: Mon, 27 Apr 2026 16:14:35 -0400

From: Willem de Bruijn <[email-masked]>

In preparation for extending to pacing hardware offload, convert the
so_txtime.sh test to a drv-net test that can be run against netdevsim
and real hardware.

Also update so_txtime.c to not exit on first failure, but run to
completion and report exit code there. This helps with debugging
unexpected results, especially when processing multiple packets,
as happens in the "reverse_order" testcase.

Signed-off-by: Willem de Bruijn <[email-masked]>

----

v4 -> v5

- move qdisc setup/restore into each test
- add tc to utils.py (separate patch)
- test expected failure (separate patch)
- fix pylint
- convert fail to pass for timing errors if KSFT_MACHINE_SLOW
  (cmd does not special case KSFT_SKIP process returncode yet)

Responses to sashiko review

- The test converts per packet failure to errors, to continue
  testing other packets, but other error() cases are not in scope.
- The test starts sender and receiver at an absolute future time,
  like the original test. This assumes ~msec scale sync'ed clocks.
- The tc qdisc replace command works fine with noqueue. Tested
  manually.

v4: https://lore.kernel.org/netdev/[email-masked]/

v3 -> v4

- restore original qdisc after test
- drop unnecessary underscore in tap test names

v3: https://lore.kernel.org/netdev/[email-masked]/

v2 -> v3

- Makefile: so_txtime from YNL_GEN_FILES to TEST_GEN_FILES (Sashiko, NIPA)

v2: https://lore.kernel.org/netdev/[email-masked]/

v1 -> v2
- move so_txtime.c for net/lib to drivers/net (Jakub)
- fix drivers/net/config order (Jakub)
- detect passing when failure is expected (Jakub, Sashiko)
- pass pylint --disable=R (Jakub)
- only call ksft_run once (Jakub)
- do not sleep if waiting time is negative (Sashiko)
- add \n when converting error() to fprintf() (Sashiko)
- 4 space indentation, instead of 2 space
- increase sync delay from 100 to 200ms, to fix rare vng flakes

v1: https://lore.kernel.org/netdev/[email-masked]/
---
 .../testing/selftests/drivers/net/.gitignore  |   1 +
 tools/testing/selftests/drivers/net/Makefile  |   2 +
 tools/testing/selftests/drivers/net/config    |   2 +
 .../selftests/{ => drivers}/net/so_txtime.c   |  25 +++-
 .../selftests/drivers/net/so_txtime.py        |  95 +++++++++++++++
 tools/testing/selftests/net/.gitignore        |   1 -
 tools/testing/selftests/net/Makefile          |   2 -
 tools/testing/selftests/net/so_txtime.sh      | 110 ------------------
 8 files changed, 120 insertions(+), 118 deletions(-)
 rename tools/testing/selftests/{ => drivers}/net/so_txtime.c (96%)
 create mode 100755 tools/testing/selftests/drivers/net/so_txtime.py
 delete mode 100755 tools/testing/selftests/net/so_txtime.sh

diff --git a/tools/testing/selftests/drivers/net/.gitignore b/tools/testing/selftests/drivers/net/.gitignore
index 585ecb4d5dc4..e5314ce4bb2d 100644
--- a/tools/testing/selftests/drivers/net/.gitignore
+++ b/tools/testing/selftests/drivers/net/.gitignore
@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0-only
 napi_id_helper
 psp_responder
+so_txtime
diff --git a/tools/testing/selftests/drivers/net/Makefile b/tools/testing/selftests/drivers/net/Makefile
index b72080c6d06b..d5bf4cb638a8 100644
--- a/tools/testing/selftests/drivers/net/Makefile
+++ b/tools/testing/selftests/drivers/net/Makefile
@@ -7,6 +7,7 @@ TEST_INCLUDES := $(wildcard lib/py/*.py) \
 
 TEST_GEN_FILES := \
 	napi_id_helper \
+	so_txtime \
 # end of TEST_GEN_FILES
 
 TEST_PROGS := \
@@ -21,6 +22,7 @@ TEST_PROGS := \
 	queues.py \
 	ring_reconfig.py \
 	shaper.py \
+	so_txtime.py \
 	stats.py \
 	xdp.py \
 # end of TEST_PROGS
diff --git a/tools/testing/selftests/drivers/net/config b/tools/testing/selftests/drivers/net/config
index fd16994366f4..92907be9c31e 100644
--- a/tools/testing/selftests/drivers/net/config
+++ b/tools/testing/selftests/drivers/net/config
@@ -9,4 +9,6 @@ CONFIG_NETCONSOLE_DYNAMIC=y
 CONFIG_NETCONSOLE_EXTENDED_LOG=y
 CONFIG_NETDEVSIM=m
 CONFIG_VLAN_8021Q=m
+CONFIG_NET_SCH_ETF=m
+CONFIG_NET_SCH_FQ=m
 CONFIG_XDP_SOCKETS=y
diff --git a/tools/testing/selftests/net/so_txtime.c b/tools/testing/selftests/drivers/net/so_txtime.c
similarity index 96%
rename from tools/testing/selftests/net/so_txtime.c
rename to tools/testing/selftests/drivers/net/so_txtime.c
index b76df1efc2ef..b6930883569b 100644
--- a/tools/testing/selftests/net/so_txtime.c
+++ b/tools/testing/selftests/drivers/net/so_txtime.c
@@ -33,6 +33,8 @@
 #include <unistd.h>
 #include <poll.h>
 
+#include "kselftest.h"
+
 static int	cfg_clockid	= CLOCK_TAI;
 static uint16_t	cfg_port	= 8000;
 static int	cfg_variance_us	= 4000;
@@ -43,6 +45,8 @@ static bool	cfg_rx;
 static uint64_t glob_tstart;
 static uint64_t tdeliver_max;
 
+static int errors;
+
 /* encode one timed transmission (of a 1B payload) */
 struct timed_send {
 	char	data;
@@ -131,13 +135,15 @@ static void do_recv_one(int fdr, struct timed_send *ts)
 	fprintf(stderr, "payload:%c delay:%lld expected:%lld (us)\n",
 			rbuf[0], (long long)tstop, (long long)texpect);
 
-	if (rbuf[0] != ts->data)
-		error(1, 0, "payload mismatch. expected %c", ts->data);
+	if (rbuf[0] != ts->data) {
+		fprintf(stderr, "payload mismatch. expected %c\n", ts->data);
+		errors++;
+	}
 
 	if (llabs(tstop - texpect) > cfg_variance_us) {
 		fprintf(stderr, "exceeds variance (%d us)\n", cfg_variance_us);
 		if (!getenv("KSFT_MACHINE_SLOW"))
-			exit(1);
+			errors++;
 	}
 }
 
@@ -255,8 +261,12 @@ static void start_time_wait(void)
 		return;
 
 	now = gettime_ns(CLOCK_REALTIME);
-	if (cfg_start_time_ns < now)
+	if (cfg_start_time_ns < now) {
+		fprintf(stderr, "FAIL: start time already passed\n");
+		if (!getenv("KSFT_MACHINE_SLOW"))
+			errors++;
 		return;
+	}
 
 	err = usleep((cfg_start_time_ns - now) / 1000);
 	if (err)
@@ -513,5 +523,10 @@ int main(int argc, char **argv)
 	else
 		do_test_tx((void *)&cfg_src_addr, cfg_alen);
 
-	return 0;
+	if (errors) {
+		fprintf(stderr, "FAIL: %d errors\n", errors);
+		return KSFT_FAIL;
+	}
+
+	return KSFT_PASS;
 }
diff --git a/tools/testing/selftests/drivers/net/so_txtime.py b/tools/testing/selftests/drivers/net/so_txtime.py
new file mode 100755
index 000000000000..c2bbeea45a61
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/so_txtime.py
@@ -0,0 +1,95 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""Regression tests for the SO_TXTIME interface.
+
+Test delivery time in FQ and ETF qdiscs.
+"""
+
+import time
+
+from lib.py import ksft_exit, ksft_run, ksft_variants
+from lib.py import KsftNamedVariant, KsftSkipEx
+from lib.py import NetDrvEpEnv, bkg, cmd, defer, tc
+
+
+def test_so_txtime(cfg, clockid, ipver, args_tx, args_rx, test_failure):
+    """Main function. Run so_txtime as sender and receiver."""
+    bin_path = cfg.test_dir / "so_txtime"
+
+    tstart = time.time_ns() + 200_000_000
+
+    cmd_addr = f"-S {cfg.addr_v[ipver]} -D {cfg.remote_addr_v[ipver]}"
+    cmd_base = f"{bin_path} -{ipver} -c {clockid} -t {tstart} {cmd_addr}"
+    cmd_rx = f"{cmd_base} {args_rx} -r"
+    cmd_tx = f"{cmd_base} {args_tx}"
+
+    with bkg(cmd_rx, host=cfg.remote, fail=test_failure, exit_wait=True):
+        cmd(cmd_tx)
+
+
+def _qdisc_setup(ifname, qdisc, optargs=""):
+    """Replace root qdisc. Restore the original after the test.
+
+    If the original is mq, children will be of type default_qdisc.
+    """
+    orig = tc(f"qdisc show dev {ifname} root", json=True)[0].get("kind", None)
+    defer(tc, f"qdisc replace dev {ifname} root {orig}")
+    tc(f"qdisc replace dev {ifname} root {qdisc} {optargs}")
+
+
+def _test_variants_mono():
+    for ipver in ["4", "6"]:
+        for testcase in [
+            ["no_delay", "a,-1", "a,-1"],
+            ["zero_delay", "a,0", "a,0"],
+            ["one_pkt", "a,10", "a,10"],
+            ["in_order", "a,10,b,20", "a,10,b,20"],
+            ["reverse_order", "a,20,b,10", "b,20,a,20"],
+        ]:
+            name = f"v{ipver}_{testcase[0]}"
+            yield KsftNamedVariant(name, ipver, testcase[1], testcase[2])
+
+
+@ksft_variants(_test_variants_mono())
+def test_so_txtime_mono(cfg, ipver, args_tx, args_rx):
+    """Run all variants of monotonic (fq) tests."""
+    _qdisc_setup(cfg.ifname, "fq")
+    test_so_txtime(cfg, "mono", ipver, args_tx, args_rx, True)
+
+
+def _test_variants_etf():
+    for ipver in ["4", "6"]:
+        for testcase in [
+            ["no_delay", "a,-1", "a,-1", 'verify_failed'],
+            ["zero_delay", "a,0", "a,0", 'verify_failed'],
+            ["one_pkt", "a,10", "a,10", True],
+            ["in_order", "a,10,b,20", "a,10,b,20", True],
+            ["reverse_order", "a,20,b,10", "b,10,a,20", True],
+        ]:
+            name = f"v{ipver}_{testcase[0]}"
+            yield KsftNamedVariant(
+                name, ipver, testcase[1], testcase[2], testcase[3]
+            )
+
+
+@ksft_variants(_test_variants_etf())
+def test_so_txtime_etf(cfg, ipver, args_tx, args_rx, expect_fail):
+    """Run all variants of etf tests."""
+    try:
+        _qdisc_setup(cfg.ifname, "etf", "clockid CLOCK_TAI delta 400000")
+    except Exception as e:
+        raise KsftSkipEx("tc does not support qdisc etf. skipping") from e
+
+    test_so_txtime(cfg, "tai", ipver, args_tx, args_rx, expect_fail)
+
+
+def main() -> None:
+    """Boilerplate ksft main."""
+    with NetDrvEpEnv(__file__) as cfg:
+        ksft_run([test_so_txtime_mono, test_so_txtime_etf], args=(cfg,))
+    ksft_exit()
+
+
+if __name__ == "__main__":
+    main()
diff --git a/tools/testing/selftests/net/.gitignore b/tools/testing/selftests/net/.gitignore
index 97ad4d551d44..02ad4c99a2b4 100644
--- a/tools/testing/selftests/net/.gitignore
+++ b/tools/testing/selftests/net/.gitignore
@@ -40,7 +40,6 @@ skf_net_off
 socket
 so_incoming_cpu
 so_netns_cookie
-so_txtime
 so_rcv_listener
 stress_reuseport_listen
 tap
diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index a275ed584026..d53670c0d7a2 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -83,7 +83,6 @@ TEST_PROGS := \
 	rxtimestamp.sh \
 	sctp_vrf.sh \
 	skf_net_off.sh \
-	so_txtime.sh \
 	srv6_end_dt46_l3vpn_test.sh \
 	srv6_end_dt4_l3vpn_test.sh \
 	srv6_end_dt6_l3vpn_test.sh \
@@ -157,7 +156,6 @@ TEST_GEN_FILES := \
 	skf_net_off \
 	so_netns_cookie \
 	so_rcv_listener \
-	so_txtime \
 	socket \
 	stress_reuseport_listen \
 	tcp_fastopen_backup_key \
diff --git a/tools/testing/selftests/net/so_txtime.sh b/tools/testing/selftests/net/so_txtime.sh
deleted file mode 100755
index 5e861ad32a42..000000000000
--- a/tools/testing/selftests/net/so_txtime.sh
+++ /dev/null
@@ -1,110 +0,0 @@
-#!/bin/bash
-# SPDX-License-Identifier: GPL-2.0
-#
-# Regression tests for the SO_TXTIME interface
-
-set -e
-
-readonly ksft_skip=4
-readonly DEV="veth0"
-readonly BIN="./so_txtime"
-
-readonly RAND="$(mktemp -u XXXXXX)"
-readonly NSPREFIX="ns-${RAND}"
-readonly NS1="${NSPREFIX}1"
-readonly NS2="${NSPREFIX}2"
-
-readonly SADDR4='192.168.1.1'
-readonly DADDR4='192.168.1.2'
-readonly SADDR6='fd::1'
-readonly DADDR6='fd::2'
-
-cleanup() {
-	ip netns del "${NS2}"
-	ip netns del "${NS1}"
-}
-
-trap cleanup EXIT
-
-# Create virtual ethernet pair between network namespaces
-ip netns add "${NS1}"
-ip netns add "${NS2}"
-
-ip link add "${DEV}" netns "${NS1}" type veth \
-  peer name "${DEV}" netns "${NS2}"
-
-# Bring the devices up
-ip -netns "${NS1}" link set "${DEV}" up
-ip -netns "${NS2}" link set "${DEV}" up
-
-# Set fixed MAC addresses on the devices
-ip -netns "${NS1}" link set dev "${DEV}" address 02:02:02:02:02:02
-ip -netns "${NS2}" link set dev "${DEV}" address 06:06:06:06:06:06
-
-# Add fixed IP addresses to the devices
-ip -netns "${NS1}" addr add 192.168.1.1/24 dev "${DEV}"
-ip -netns "${NS2}" addr add 192.168.1.2/24 dev "${DEV}"
-ip -netns "${NS1}" addr add       fd::1/64 dev "${DEV}" nodad
-ip -netns "${NS2}" addr add       fd::2/64 dev "${DEV}" nodad
-
-run_test() {
-	local readonly IP="$1"
-	local readonly CLOCK="$2"
-	local readonly TXARGS="$3"
-	local readonly RXARGS="$4"
-
-	if [[ "${IP}" == "4" ]]; then
-		local readonly SADDR="${SADDR4}"
-		local readonly DADDR="${DADDR4}"
-	elif [[ "${IP}" == "6" ]]; then
-		local readonly SADDR="${SADDR6}"
-		local readonly DADDR="${DADDR6}"
-	else
-		echo "Invalid IP version ${IP}"
-		exit 1
-	fi
-
-	local readonly START="$(date +%s%N --date="+ 0.1 seconds")"
-
-	ip netns exec "${NS2}" "${BIN}" -"${IP}" -c "${CLOCK}" -t "${START}" -S "${SADDR}" -D "${DADDR}" "${RXARGS}" -r &
-	ip netns exec "${NS1}" "${BIN}" -"${IP}" -c "${CLOCK}" -t "${START}" -S "${SADDR}" -D "${DADDR}" "${TXARGS}"
-	wait "$!"
-}
-
-do_test() {
-	run_test $@
-	[ $? -ne 0 ] && ret=1
-}
-
-do_fail_test() {
-	run_test $@
-	[ $? -eq 0 ] && ret=1
-}
-
-ip netns exec "${NS1}" tc qdisc add dev "${DEV}" root fq
-set +e
-ret=0
-do_test 4 mono a,-1 a,-1
-do_test 6 mono a,0 a,0
-do_test 6 mono a,10 a,10
-do_test 4 mono a,10,b,20 a,10,b,20
-do_test 6 mono a,20,b,10 b,20,a,20
-
-if ip netns exec "${NS1}" tc qdisc replace dev "${DEV}" root etf clockid CLOCK_TAI delta 400000; then
-	do_fail_test 4 tai a,-1 a,-1
-	do_fail_test 6 tai a,0 a,0
-	do_test 6 tai a,10 a,10
-	do_test 4 tai a,10,b,20 a,10,b,20
-	do_test 6 tai a,20,b,10 b,10,a,20
-else
-	echo "tc ($(tc -V)) does not support qdisc etf. skipping"
-	[ $ret -eq 0 ] && ret=$ksft_skip
-fi
-
-if [ $ret -eq 0 ]; then
-	echo OK. All tests passed
-elif [[ $ret -ne $ksft_skip && -n "$KSFT_MACHINE_SLOW" ]]; then
-	echo "Ignoring errors due to slow environment" 1>&2
-	ret=0
-fi
-exit $ret
-- 
2.54.0.545.g6539524ca2-goog