selftests: drv-net: add a Python version of the GRO test

Rewrite the existing gro.sh test in Python. The conversion
not exact, the changes are related to integrating the test
with our "remote endpoint" paradigm. The test now reads
the IP addresses from the user config. It resolves the MAC
address (including running over Layer 3 networks).

Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20251120021024.2944527-10-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/drivers/net/Makefile

@@ -11,7 +11,7 @@ TEST_GEN_FILES := \
 # end of TEST_GEN_FILES
 
 TEST_PROGS := \
-	gro.sh \
+	gro.py \
 	hds.py \
 	napi_id.py \
 	napi_threaded.py \

tools/testing/selftests/drivers/net/gro.c

@@ -58,6 +58,7 @@
 #include <unistd.h>
 
 #include "../../kselftest.h"
+#include "../../net/lib/ksft.h"
 
 #define DPORT 8000
 #define SPORT 1500
@@ -1127,6 +1128,8 @@ static void gro_receiver(void)
 	set_timeout(rxfd);
 	bind_packetsocket(rxfd);
 
+	ksft_ready();
+
 	memset(correct_payload, 0, sizeof(correct_payload));
 
 	if (strcmp(testname, "data") == 0) {

tools/testing/selftests/drivers/net/gro.py

@@ -0,0 +1,164 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""
+GRO (Generic Receive Offload) conformance tests.
+
+Validates that GRO coalescing works correctly by running the gro
+binary in different configurations and checking for correct packet
+coalescing behavior.
+
+Test cases:
+  - data: Data packets with same size/headers and correct seq numbers coalesce
+  - ack: Pure ACK packets do not coalesce
+  - flags: Packets with PSH, SYN, URG, RST flags do not coalesce
+  - tcp: Packets with incorrect checksum, non-consecutive seqno don't coalesce
+  - ip: Packets with different ECN, TTL, TOS, or IP options don't coalesce
+  - large: Packets larger than GRO_MAX_SIZE don't coalesce
+"""
+
+import os
+from lib.py import ksft_run, ksft_exit, ksft_pr
+from lib.py import NetDrvEpEnv, KsftXfailEx
+from lib.py import cmd, defer, bkg, ip
+from lib.py import ksft_variants
+
+
+def _resolve_dmac(cfg, ipver):
+    """
+    Find the destination MAC address remote host should use to send packets
+    towards the local host. It may be a router / gateway address.
+    """
+
+    attr = "dmac" + ipver
+    # Cache the response across test cases
+    if hasattr(cfg, attr):
+        return getattr(cfg, attr)
+
+    route = ip(f"-{ipver} route get {cfg.addr_v[ipver]}",
+               json=True, host=cfg.remote)[0]
+    gw = route.get("gateway")
+    # Local L2 segment, address directly
+    if not gw:
+        setattr(cfg, attr, cfg.dev['address'])
+        return getattr(cfg, attr)
+
+    # ping to make sure neighbor is resolved,
+    # bind to an interface, for v6 the GW is likely link local
+    cmd(f"ping -c1 -W0 -I{cfg.remote_ifname} {gw}", host=cfg.remote)
+
+    neigh = ip(f"neigh get {gw} dev {cfg.remote_ifname}",
+               json=True, host=cfg.remote)[0]
+    setattr(cfg, attr, neigh['lladdr'])
+    return getattr(cfg, attr)
+
+
+def _write_defer_restore(cfg, path, val, defer_undo=False):
+    with open(path, "r", encoding="utf-8") as fp:
+        orig_val = fp.read().strip()
+        if str(val) == orig_val:
+            return
+    with open(path, "w", encoding="utf-8") as fp:
+        fp.write(val)
+    if defer_undo:
+        defer(_write_defer_restore, cfg, path, orig_val)
+
+
+def _set_mtu_restore(dev, mtu, host):
+    if dev['mtu'] < mtu:
+        ip(f"link set dev {dev['ifname']} mtu {mtu}", host=host)
+        defer(ip, f"link set dev {dev['ifname']} mtu {dev['mtu']}", host=host)
+
+
+def _setup(cfg, test_name):
+    """ Setup hardware loopback mode for GRO testing. """
+
+    if not hasattr(cfg, "bin_remote"):
+        cfg.bin_local = cfg.test_dir / "gro"
+        cfg.bin_remote = cfg.remote.deploy(cfg.bin_local)
+
+    # "large" test needs at least 4k MTU
+    if test_name == "large":
+        _set_mtu_restore(cfg.dev, 4096, None)
+        _set_mtu_restore(cfg.remote_dev, 4096, cfg.remote)
+
+    flush_path = f"/sys/class/net/{cfg.ifname}/gro_flush_timeout"
+    irq_path = f"/sys/class/net/{cfg.ifname}/napi_defer_hard_irqs"
+
+    _write_defer_restore(cfg, flush_path, "200000", defer_undo=True)
+    _write_defer_restore(cfg, irq_path, "10", defer_undo=True)
+
+    try:
+        # Disable TSO for local tests
+        cfg.require_nsim()  # will raise KsftXfailEx if not running on nsim
+
+        cmd(f"ethtool -K {cfg.ifname} gro on tso off")
+        cmd(f"ethtool -K {cfg.remote_ifname} gro on tso off", host=cfg.remote)
+    except KsftXfailEx:
+        pass
+
+def _gro_variants():
+    """Generator that yields all combinations of protocol and test types."""
+
+    for protocol in ["ipv4", "ipv6", "ipip"]:
+        for test_name in ["data", "ack", "flags", "tcp", "ip", "large"]:
+            yield protocol, test_name
+
+
+@ksft_variants(_gro_variants())
+def test(cfg, protocol, test_name):
+    """Run a single GRO test with retries."""
+
+    ipver = "6" if protocol[-1] == "6" else "4"
+    cfg.require_ipver(ipver)
+
+    _setup(cfg, test_name)
+
+    base_cmd_args = [
+        f"--{protocol}",
+        f"--dmac {_resolve_dmac(cfg, ipver)}",
+        f"--smac {cfg.remote_dev['address']}",
+        f"--daddr {cfg.addr_v[ipver]}",
+        f"--saddr {cfg.remote_addr_v[ipver]}",
+        f"--test {test_name}",
+        "--verbose"
+    ]
+    base_args = " ".join(base_cmd_args)
+
+    # Each test is run 6 times to deflake, because given the receive timing,
+    # not all packets that should coalesce will be considered in the same flow
+    # on every try.
+    max_retries = 6
+    for attempt in range(max_retries):
+        rx_cmd = f"{cfg.bin_local} {base_args} --rx --iface {cfg.ifname}"
+        tx_cmd = f"{cfg.bin_remote} {base_args} --iface {cfg.remote_ifname}"
+
+        fail_now = attempt >= max_retries - 1
+
+        with bkg(rx_cmd, ksft_ready=True, exit_wait=True,
+                 fail=fail_now) as rx_proc:
+            cmd(tx_cmd, host=cfg.remote)
+
+        if rx_proc.ret == 0:
+            return
+
+        ksft_pr(rx_proc.stdout.strip().replace('\n', '\n# '))
+        ksft_pr(rx_proc.stderr.strip().replace('\n', '\n# '))
+
+        if test_name == "large" and os.environ.get("KSFT_MACHINE_SLOW"):
+            ksft_pr(f"Ignoring {protocol}/{test_name} failure due to slow environment")
+            return
+
+        ksft_pr(f"Attempt {attempt + 1}/{max_retries} failed, retrying...")
+
+
+def main() -> None:
+    """ Ksft boiler plate main """
+
+    with NetDrvEpEnv(__file__) as cfg:
+        ksft_run(cases=[test], args=(cfg,))
+    ksft_exit()
+
+
+if __name__ == "__main__":
+    main()

tools/testing/selftests/drivers/net/gro.sh

@@ -1,105 +0,0 @@
-#!/bin/bash
-# SPDX-License-Identifier: GPL-2.0
-
-readonly SERVER_MAC="aa:00:00:00:00:02"
-readonly CLIENT_MAC="aa:00:00:00:00:01"
-readonly TESTS=("data" "ack" "flags" "tcp" "ip" "large")
-readonly PROTOS=("ipv4" "ipv6" "ipip")
-dev=""
-test="all"
-proto="ipv4"
-
-run_test() {
-  local server_pid=0
-  local exit_code=0
-  local protocol=$1
-  local test=$2
-  local ARGS=( "--${protocol}" "--dmac" "${SERVER_MAC}" \
-  "--smac" "${CLIENT_MAC}" "--test" "${test}" "--verbose" )
-
-  setup_ns
-  # Each test is run 6 times to deflake, because given the receive timing,
-  # not all packets that should coalesce will be considered in the same flow
-  # on every try.
-  for tries in {1..6}; do
-    # Actual test starts here
-    ip netns exec $server_ns ./gro "${ARGS[@]}" "--rx" "--iface" "server" \
-      1>>log.txt &
-    server_pid=$!
-    sleep 0.5  # to allow for socket init
-    ip netns exec $client_ns ./gro "${ARGS[@]}" "--iface" "client" \
-      1>>log.txt
-    wait "${server_pid}"
-    exit_code=$?
-    if [[ ${test} == "large" && -n "${KSFT_MACHINE_SLOW}" && \
-          ${exit_code} -ne 0 ]]; then
-        echo "Ignoring errors due to slow environment" 1>&2
-        exit_code=0
-    fi
-    if [[ "${exit_code}" -eq 0 ]]; then
-        break;
-    fi
-  done
-  cleanup_ns
-  echo ${exit_code}
-}
-
-run_all_tests() {
-  local failed_tests=()
-  for proto in "${PROTOS[@]}"; do
-    for test in "${TESTS[@]}"; do
-      echo "running test ${proto} ${test}" >&2
-      exit_code=$(run_test $proto $test)
-      if [[ "${exit_code}" -ne 0 ]]; then
-        failed_tests+=("${proto}_${test}")
-      fi;
-    done;
-  done
-  if [[ ${#failed_tests[@]} -ne 0 ]]; then
-    echo "failed tests: ${failed_tests[*]}. \
-    Please see log.txt for more logs"
-    exit 1
-  else
-    echo "All Tests Succeeded!"
-  fi;
-}
-
-usage() {
-  echo "Usage: $0 \
-  [-i <DEV>] \
-  [-t data|ack|flags|tcp|ip|large] \
-  [-p <ipv4|ipv6>]" 1>&2;
-  exit 1;
-}
-
-while getopts "i:t:p:" opt; do
-  case "${opt}" in
-    i)
-      dev="${OPTARG}"
-      ;;
-    t)
-      test="${OPTARG}"
-      ;;
-    p)
-      proto="${OPTARG}"
-      ;;
-    *)
-      usage
-      ;;
-  esac
-done
-
-if [ -n "$dev" ]; then
-	source $(dirname $0)/../../net/lib/setup_loopback.sh
-else
-	source $(dirname $0)/../../net/lib/setup_veth.sh
-fi
-
-setup
-trap cleanup EXIT
-if [[ "${test}" == "all" ]]; then
-  run_all_tests
-else
-  exit_code=$(run_test "${proto}" "${test}")
-  exit $exit_code
-fi;