[PATCH net-next 09/11] selftests: drv-net: refactor devmem command builders into lib module

Bobby Eshleman
2026-04-28T22:42:24Z

Adding netkit-based devmem tests is a straight-forward copy of devmem
test commands plus some args for the nk cases, so this patch breaks out
these command builders into helpers used by both.

Though we tried to avoid libraries to avoid increasing the barrier of
entry/complexity (see selftests/drivers/net/README.md, section "Avoid
libraries and frameworks"), factoring out these functions seemed like
the lesser of two evils in this case of using the same commands, just
with slightly different args per environment.

I experimented with just having all of the tests in the same file to
avoid having helpers in a library file, but because ksft_run() is
limited to a single call per file, and the new tests will require
different environments (NetDrvContEnv/NetDrvEpEnv), it would have been
necessary to have each test set up its own environment instead of
sharing one for the entire ksft_run() run. This came at the cost of
ballooning the test time (from under 5s to 30s on my test system), so to
strike a balance these tests were placed in separate files so they could
keep a shared environment across a single ksft_run() run shared across
all tests using the same env type (introduced in subsequent patches).

The helpers work transparently with both plain and netkit environments
by inspecting cfg for netkit-specific attributes (netns, nk_queue,
etc...).

No functional change to the existing devmem.py tests.

Assisted-by: Claude Code:claude-sonnet-4-6
Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
---
tools/testing/selftests/drivers/net/hw/devmem.py | 73 +------
.../selftests/drivers/net/hw/lib/py/devmem.py | 215 +++++++++++++++++++++
2 files changed, 224 insertions(+), 64 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/hw/devmem.py b/tools/testing/selftests/drivers/net/hw/devmem.py
index ee863e90d1e0..33648e39577a 100755
--- a/tools/testing/selftests/drivers/net/hw/devmem.py
+++ b/tools/testing/selftests/drivers/net/hw/devmem.py
@@ -1,92 +1,37 @@
#!/usr/bin/env python3
# SPDX-License-Identifier: GPL-2.0
+"""Test devmem TCP."""

from os import path
-from lib.py import ksft_run, ksft_exit
-from lib.py import ksft_eq, KsftSkipEx
+from lib.py import ksft_run, ksft_exit, ksft_disruptive
from lib.py import NetDrvEpEnv
-from lib.py import bkg, cmd, rand_port, wait_port_listen
-from lib.py import ksft_disruptive
-
-
-def require_devmem(cfg):
- if not hasattr(cfg, "_devmem_probed"):
- probe_command = f"{cfg.bin_local} -f {cfg.ifname}"
- cfg._devmem_supported = cmd(probe_command, fail=False, shell=True).ret == 0
- cfg._devmem_probed = True
-
- if not cfg._devmem_supported:
- raise KsftSkipEx("Test requires devmem support")
+from lib.py.devmem import setup_test, run_rx, run_tx, run_tx_chunks, run_rx_hds

@ksft_disruptive
def check_rx(cfg) -> None:
- require_devmem(cfg)
-
- port = rand_port()
- socat = f"socat -u - TCP{cfg.addr_ipver}:{cfg.baddr}:{port},bind={cfg.remote_baddr}:{port}"
- listen_cmd = f"{cfg.bin_local} -l -f {cfg.ifname} -s {cfg.addr} -p {port} -c {cfg.remote_addr} -v 7"
-
- with bkg(listen_cmd, exit_wait=True) as ncdevmem:
- wait_port_listen(port)
- cmd(f"yes $(echo -e \x01\x02\x03\x04\x05\x06) | \
- head -c 1K | {socat}", host=cfg.remote, shell=True)
-
- ksft_eq(ncdevmem.ret, 0)
+ run_rx(cfg)

@ksft_disruptive
def check_tx(cfg) -> None:
- require_devmem(cfg)
-
- port = rand_port()
- listen_cmd = f"socat -U - TCP{cfg.addr_ipver}-LISTEN:{port}"
-
- with bkg(listen_cmd, host=cfg.remote, exit_wait=True) as socat:
- wait_port_listen(port, host=cfg.remote)
- cmd(f"echo -e \"hello\\nworld\"| {cfg.bin_local} -f {cfg.ifname} -s {cfg.remote_addr} -p {port}", shell=True)
-
- ksft_eq(socat.stdout.strip(), "hello\nworld")
+ run_tx(cfg)

@ksft_disruptive
def check_tx_chunks(cfg) -> None:
- require_devmem(cfg)
-
- port = rand_port()
- listen_cmd = f"socat -U - TCP{cfg.addr_ipver}-LISTEN:{port}"
-
- with bkg(listen_cmd, host=cfg.remote, exit_wait=True) as socat:
- wait_port_listen(port, host=cfg.remote)
- cmd(f"echo -e \"hello\\nworld\"| {cfg.bin_local} -f {cfg.ifname} -s {cfg.remote_addr} -p {port} -z 3", shell=True)
-
- ksft_eq(socat.stdout.strip(), "hello\nworld")
+ run_tx_chunks(cfg)

def check_rx_hds(cfg) -> None:
- """Test HDS splitting across payload sizes."""
- require_devmem(cfg)
-
- for size in [1, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192]:
- port = rand_port()
- listen_cmd = f"{cfg.bin_local} -L -l -f {cfg.ifname} -s {cfg.addr} -p {port}"
-
- with bkg(listen_cmd, exit_wait=True) as ncdevmem:
- wait_port_listen(port)
- cmd(f"dd if=/dev/zero bs={size} count=1 2>/dev/null | " +
- f"socat -b {size} -u - TCP{cfg.addr_ipver}:{cfg.baddr}:{port},nodelay",
- host=cfg.remote, shell=True)
-
- ksft_eq(ncdevmem.ret, 0, f"HDS failed for payload size {size}")
+ run_rx_hds(cfg)

def main() -> None:
with NetDrvEpEnv(__file__) as cfg:
- cfg.bin_local = path.abspath(path.dirname(__file__) + "/ncdevmem")
- cfg.bin_remote = cfg.remote.deploy(cfg.bin_local)
-
+ setup_test(cfg, path.abspath(path.dirname(__file__) + "/ncdevmem"))
ksft_run([check_rx, check_tx, check_tx_chunks, check_rx_hds],
- args=(cfg, ))
+ args=(cfg,))
ksft_exit()

diff --git a/tools/testing/selftests/drivers/net/hw/lib/py/devmem.py b/tools/testing/selftests/drivers/net/hw/lib/py/devmem.py
new file mode 100644
index 000000000000..e95fc38337fa
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/hw/lib/py/devmem.py
@@ -0,0 +1,215 @@
+# SPDX-License-Identifier: GPL-2.0
+"""Shared helpers for devmem TCP selftests."""
+
+import re
+
+from net.lib.py import (bkg, cmd, defer, ethtool, rand_port, wait_port_listen,
+ ksft_eq, KsftSkipEx, NetNSEnter, EthtoolFamily,
+ NetdevFamily)
+
+
+def require_devmem(cfg):
+ if not hasattr(cfg, "_devmem_probed"):
+ probe_command = f"{cfg.bin_local} -f {cfg.ifname}"
+ cfg._devmem_supported = cmd(probe_command, fail=False, shell=True).ret == 0
+ cfg._devmem_probed = True
+
+ if not cfg._devmem_supported:
+ raise KsftSkipEx("Test requires devmem support")
+
+
+def configure_nic(cfg):
+ """Channels, rings, RSS, queue lease for netkit devmem.
+
+ Rings and RSS are re-applied each call because per-test defers restore
+ them after every test case. The queue lease is created only once.
+ """
+ cfg.require_ipver('6')
+ ethnl = EthtoolFamily()
+
+ channels = ethnl.channels_get({'header': {'dev-index': cfg.ifindex}})
+ channels = channels['combined-count']
+ if channels < 2:
+ raise KsftSkipEx(
+ 'Test requires NETIF with at least 2 combined channels'
+ )
+
+ rings = ethnl.rings_get({'header': {'dev-index': cfg.ifindex}})
+ rx_rings = rings['rx']
+ hds_thresh = rings.get('hds-thresh', 0)
+ orig_data_split = rings.get('tcp-data-split', 'unknown')
+
+ ethnl.rings_set({'header': {'dev-index': cfg.ifindex},
+ 'tcp-data-split': 'enabled',
+ 'hds-thresh': 0,
+ 'rx': min(64, rx_rings)})
+ defer(ethnl.rings_set, {'header': {'dev-index': cfg.ifindex},
+ 'tcp-data-split': orig_data_split,
+ 'hds-thresh': hds_thresh,
+ 'rx': rx_rings})
+
+ cfg.src_queue = channels - 1
+ ethtool(f"-X {cfg.ifname} equal {cfg.src_queue}")
+ defer(ethtool, f"-X {cfg.ifname} default")
+
+ if not hasattr(cfg, 'nk_queue'):
+ with NetNSEnter(str(cfg.netns)):
+ netdevnl = NetdevFamily()
+ lease_result = netdevnl.queue_create({
+ "ifindex": cfg.nk_guest_ifindex,
+ "type": "rx",
+ "lease": {
+ "ifindex": cfg.ifindex,
+ "queue": {"id": cfg.src_queue, "type": "rx"},
+ "netns-id": 0,
+ },
+ })
+ cfg.nk_queue = lease_result['id']
+
+
+def set_flow_rule(cfg, port):
+ output = ethtool(
+ f"-N {cfg.ifname} flow-type tcp6 dst-port {port}"
+ f" action {cfg.src_queue}"
+ ).stdout
+ return int(re.search(r'ID (\d+)', output).group(1))
+
+
+def ncdevmem_rx(cfg, port, verify=True, fail_on_linear=False):
+ if hasattr(cfg, 'netns'):
+ flow_rule_id = set_flow_rule(cfg, port)
+ defer(ethtool, f"-N {cfg.ifname} delete {flow_rule_id}")
+
+ ifname = cfg._nk_guest_ifname
+ addr = cfg.nk_guest_ipv6
+ extras = f" -t {cfg.nk_queue} -q 1 -n"
+ if verify:
+ extras += " -v 7"
+ else:
+ ifname = cfg.ifname
+ addr = cfg.addr
+ extras = ""
+
+ if fail_on_linear:
+ extras += " -L"
+
+ return f"{cfg.bin_local} -l -f {ifname} -s {addr} -p {port} {extras}"
+
+
+def ncdevmem_tx(cfg, port, chunk_size=0):
+ """ncdevmem TX send command (without stdin pipe)."""
+ if hasattr(cfg, 'netns'):
+ ifname = cfg._nk_guest_ifname
+ addr = cfg.remote_addr_v['6']
+ nk_args = "-t 0 -q 1 -n"
+ else:
+ ifname = cfg.ifname
+ addr = cfg.remote_addr
+ nk_args = ""
+
+ chunk = f"-z {chunk_size}" if chunk_size else ""
+
+ return (f"{cfg.bin_local} -f {ifname} -s {addr} -p {port}"
+ f" {nk_args} {chunk}").rstrip()
+
+
+def socat_send(cfg, port, buf_size=0, nodelay=False, bind=False):
+ """Socat command for sending to the devmem listener."""
+ proto = f"TCP{cfg.addr_ipver}"
+
+ if hasattr(cfg, 'netns'):
+ addr = f"[{cfg.nk_guest_ipv6}]"
+ else:
+ addr = cfg.baddr
+
+ buf = f"-b {buf_size} " if buf_size else ""
+
+ suffix = ""
+ if nodelay:
+ suffix += ",nodelay"
+ # Match the 5-tuple flow rule ncdevmem installs when given -c.
+ if bind:
+ suffix += f",bind={cfg.remote_baddr}:{port}"
+
+ return f"socat {buf}-u - {proto}:{addr}:{port}{suffix}"
+
+
+def socat_listen(cfg, port):
+ """Socat listen command for TX tests."""
+ proto = f"TCP{cfg.addr_ipver}"
+
+ if hasattr(cfg, 'netns'):
+ opts = ",reuseaddr"
+ else:
+ opts = ""
+
+ return f"socat -U - {proto}-LISTEN:{port}{opts}"
+
+
+def setup_test(cfg, bin_local):
+ cfg.bin_local = bin_local
+ cfg.bin_remote = cfg.remote.deploy(cfg.bin_local)
+ cfg.listen_ns = getattr(cfg, 'netns', None)
+ require_devmem(cfg)
+
+
+def run_rx(cfg):
+ if hasattr(cfg, 'netns'):
+ configure_nic(cfg)
+ port = rand_port()
+ socat = socat_send(cfg, port)
+ data_pipe = (f"yes $(echo -e \x01\x02\x03\x04\x05\x06) | head -c 1K"
+ f" | {socat}")
+ ns = getattr(cfg, "netns", None)
+
+ listen_cmd = ncdevmem_rx(cfg, port)
+ with bkg(listen_cmd, exit_wait=True, ns=ns) as ncdevmem:
+ wait_port_listen(port, proto="tcp", ns=ns)
+ cmd(data_pipe, host=cfg.remote, shell=True)
+ ksft_eq(ncdevmem.ret, 0)
+
+
+def run_tx(cfg):
+ if hasattr(cfg, 'netns'):
+ configure_nic(cfg)
+ ns = getattr(cfg, "netns", None)
+ port = rand_port()
+ tx = ncdevmem_tx(cfg, port)
+ listen_cmd = socat_listen(cfg, port)
+
+ with bkg(listen_cmd, host=cfg.remote, exit_wait=True) as socat:
+ wait_port_listen(port, host=cfg.remote)
+ cmd(f"bash -c 'echo -e \"hello\\nworld\" | {tx}'", ns=ns, shell=True)
+ ksft_eq(socat.stdout.strip(), "hello\nworld")
+
+
+def run_tx_chunks(cfg):
+ if hasattr(cfg, 'netns'):
+ configure_nic(cfg)
+ ns = getattr(cfg, "netns", None)
+ port = rand_port()
+ tx = ncdevmem_tx(cfg, port, chunk_size=3)
+ listen_cmd = socat_listen(cfg, port)
+
+ with bkg(listen_cmd, host=cfg.remote, exit_wait=True) as socat:
+ wait_port_listen(port, host=cfg.remote)
+ cmd(f"bash -c 'echo -e \"hello\\nworld\" | {tx}'", ns=ns, shell=True)
+ ksft_eq(socat.stdout.strip(), "hello\nworld")
+
+
+def run_rx_hds(cfg):
+ if hasattr(cfg, 'netns'):
+ configure_nic(cfg)
+ ns = getattr(cfg, "netns", None)
+
+ for size in [1, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192]:
+ port = rand_port()
+
+ listen_cmd = ncdevmem_rx(cfg, port, verify=False, fail_on_linear=True)
+ socat = socat_send(cfg, port, buf_size=size, nodelay=True)
+
+ with bkg(listen_cmd, exit_wait=True, ns=ns) as ncdevmem:
+ wait_port_listen(port, proto="tcp", ns=ns)
+ cmd(f"dd if=/dev/zero bs={size} count=1 2>/dev/null | "
+ f"{socat}", host=cfg.remote, shell=True)
+ ksft_eq(ncdevmem.ret, 0, f"HDS failed for payload size {size}")

--
2.52.0