[net-next v4 12/12] selftests: drv-net: Add USO test

[Joe Damato]

Add a simple test for USO. Can be used with netdevsim or real hardware.
Tests both ipv4 and ipv6 with several full segments and a partial
segment.

Suggested-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Joe Damato <joe@xxxxxxx>
---
 v4:
   - Fix python linter issues (unused imports, docstring, etc).

 rfcv2:
   - new in rfcv2

 tools/testing/selftests/drivers/net/Makefile |  1 +
 tools/testing/selftests/drivers/net/uso.py   | 96 ++++++++++++++++++++
 2 files changed, 97 insertions(+)
 create mode 100755 tools/testing/selftests/drivers/net/uso.py

diff --git a/tools/testing/selftests/drivers/net/Makefile b/tools/testing/selftests/drivers/net/Makefile
index 8154d6d429d3..800065fe443f 100644
--- a/tools/testing/selftests/drivers/net/Makefile
+++ b/tools/testing/selftests/drivers/net/Makefile
@@ -22,6 +22,7 @@ TEST_PROGS := \
 	ring_reconfig.py \
 	shaper.py \
 	stats.py \
+	uso.py \
 	xdp.py \
 # end of TEST_PROGS
 
diff --git a/tools/testing/selftests/drivers/net/uso.py b/tools/testing/selftests/drivers/net/uso.py
new file mode 100755
index 000000000000..2ddeae99b4d6
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/uso.py
@@ -0,0 +1,96 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""Test USO
+
+Sends large UDP datagrams with UDP_SEGMENT and verifies that the peer
+receives the correct number of individual segments with correct sizes.
+"""
+import socket
+import time
+
+from lib.py import ksft_run, ksft_exit, KsftSkipEx
+from lib.py import ksft_ge
+from lib.py import NetDrvEpEnv
+from lib.py import defer, ethtool, ip, rand_port
+
+# python doesn't expose this constant, so we need to hardcode it to enable UDP
+# segmentation for large payloads
+UDP_SEGMENT = 103
+
+
+def _send_uso(cfg, ipver, mss, total_payload, port):
+    if ipver == "4":
+        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        dst = (cfg.remote_addr_v["4"], port)
+    else:
+        sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
+        dst = (cfg.remote_addr_v["6"], port)
+
+    sock.setsockopt(socket.IPPROTO_UDP, UDP_SEGMENT, mss)
+    payload = bytes(range(256)) * ((total_payload // 256) + 1)
+    payload = payload[:total_payload]
+    sock.sendto(payload, dst)
+    sock.close()
+    return payload
+
+
+def _get_rx_packets(cfg):
+    stats = ip(f"-s link show dev {cfg.remote_ifname}",
+               json=True, host=cfg.remote)[0]
+    return stats['stats64']['rx']['packets']
+
+
+def _test_uso(cfg, ipver, mss, total_payload):
+    cfg.require_ipver(ipver)
+
+    try:
+        ethtool(f"-K {cfg.ifname} tx-udp-segmentation on")
+    except Exception as exc:
+        raise KsftSkipEx(
+            "Device does not support tx-udp-segmentation") from exc
+    defer(ethtool, f"-K {cfg.ifname} tx-udp-segmentation off")
+
+    expected_segs = (total_payload + mss - 1) // mss
+
+    rx_before = _get_rx_packets(cfg)
+
+    port = rand_port(stype=socket.SOCK_DGRAM)
+    _send_uso(cfg, ipver, mss, total_payload, port)
+
+    time.sleep(0.5)
+
+    rx_after = _get_rx_packets(cfg)
+    rx_delta = rx_after - rx_before
+
+    ksft_ge(rx_delta, expected_segs,
+            comment=f"Expected >= {expected_segs} rx packets, got {rx_delta}")
+
+
+def test_uso_v4(cfg):
+    """USO IPv4: 11 segments (10 full + 1 partial)."""
+    _test_uso(cfg, "4", 1400, 1400 * 10 + 500)
+
+
+def test_uso_v6(cfg):
+    """USO IPv6: 11 segments (10 full + 1 partial)."""
+    _test_uso(cfg, "6", 1400, 1400 * 10 + 500)
+
+
+def test_uso_v4_exact(cfg):
+    """USO IPv4: exact multiple of MSS (5 full segments)."""
+    _test_uso(cfg, "4", 1400, 1400 * 5)
+
+
+def main() -> None:
+    """Run USO tests."""
+    with NetDrvEpEnv(__file__) as cfg:
+        ksft_run([test_uso_v4,
+                  test_uso_v6,
+                  test_uso_v4_exact],
+                 args=(cfg, ))
+    ksft_exit()
+
+
+if __name__ == "__main__":
+    main()
-- 
2.52.0