Breno Leitao wrote:
> Add a basic selftest for the netpoll polling mechanism, specifically
> targeting the netpoll poll() side.
>
> The test creates a scenario where network transmission is running at
> maximum speed, and netpoll needs to poll the NIC. This is achieved by:
>
> 1. Configuring a single RX/TX queue to create contention
> 2. Generating background traffic to saturate the interface
> 3. Sending netconsole messages to trigger netpoll polling
> 4. Using dynamic netconsole targets via configfs
> 5. Delete and create new netconsole targets after some messages
> 6. Start a bpftrace in parallel to make sure netpoll_poll_dev() is
> called
> 7. If bpftrace exists and netpoll_poll_dev() was called, stop.
>
> The test validates a critical netpoll code path by monitoring traffic
> flow and ensuring netpoll_poll_dev() is called when the normal TX path
> is blocked.
>
> This addresses a gap in netpoll test coverage for a path that is
> tricky for the network stack.
>
> Signed-off-by: Breno Leitao <lei...@debian.org>
> ---
> tools/testing/selftests/drivers/net/Makefile | 1 +
> .../testing/selftests/drivers/net/netpoll_basic.py | 345
> +++++++++++++++++++++
> 2 files changed, 346 insertions(+)
>
> diff --git a/tools/testing/selftests/drivers/net/Makefile
> b/tools/testing/selftests/drivers/net/Makefile
> index bd309b2d39095..9bd84d6b542e5 100644
> --- a/tools/testing/selftests/drivers/net/Makefile
> +++ b/tools/testing/selftests/drivers/net/Makefile
> @@ -16,6 +16,7 @@ TEST_PROGS := \
> netcons_fragmented_msg.sh \
> netcons_overflow.sh \
> netcons_sysdata.sh \
> + netpoll_basic.py \
> ping.py \
> queues.py \
> stats.py \
> diff --git a/tools/testing/selftests/drivers/net/netpoll_basic.py
> b/tools/testing/selftests/drivers/net/netpoll_basic.py
> new file mode 100755
> index 0000000000000..f523d5a1c707e
> --- /dev/null
> +++ b/tools/testing/selftests/drivers/net/netpoll_basic.py
> @@ -0,0 +1,345 @@
> +#!/usr/bin/env python3
> +# SPDX-License-Identifier: GPL-2.0
> +# Author: Breno Leitao <lei...@debian.org>
> +"""
> + This test aims to evaluate the netpoll polling mechanism (as in
> + netpoll_poll_dev()). It presents a complex scenario where the network
> + attempts to send a packet but fails, prompting it to poll the NIC from
> within
> + the netpoll TX side.
> +
> + This has been a crucial path in netpoll that was previously untested. Jakub
> + suggested using a single RX/TX queue, pushing traffic to the NIC, and then
> + sending netpoll messages (via netconsole) to trigger the poll.
> +
> + In parallel, bpftrace is used to detect if netpoll_poll_dev() was called. If
> + so, the test passes, otherwise it will be skipped. This test is very
> dependent on
> + the driver and environment, given we are trying to trigger a tricky
> scenario.
> +"""
> +
> +import errno
> +import logging
> +import os
> +import random
> +import string
> +import threading
> +import time
> +
> +from lib.py import (
> + bpftrace,
> + ethtool,
> + GenerateTraffic,
> + ksft_exit,
> + ksft_pr,
> + ksft_run,
> + KsftFailEx,
> + KsftSkipEx,
> + NetDrvEpEnv,
> +)
> +
> +# Configure logging
> +logging.basicConfig(
> + level=logging.INFO,
> + format="%(asctime)s - %(levelname)s - %(message)s",
> +)
> +
> +NETCONSOLE_CONFIGFS_PATH: str = "/sys/kernel/config/netconsole"
> +NETCONS_REMOTE_PORT: int = 6666
> +NETCONS_LOCAL_PORT: int = 1514
> +# Max number of netcons messages to send. Each iteration will setup
> +# netconsole and send 10 messages
> +ITERATIONS: int = 20
> +# MAPS contains the information coming from bpftrace
> +# it will have only one key: @hits, which tells the number of times
> +# netpoll_poll_dev() was called
nit: no longer has ampersand prefix
> +MAPS: dict[str, int] = {}
> +# Thread to run bpftrace in parallel
> +BPF_THREAD: threading.Thread = None
> +# Time bpftrace will be running in parallel.
> +BPFTRACE_TIMEOUT: int = 15
> +
> +
> +def ethtool_read_rx_tx_queue(interface_name: str) -> tuple[int, int]:
> + """
> + Read the number of RX and TX queues using ethtool. This will be used
> + to restore it after the test
> + """
> + rx_queue = 0
> + tx_queue = 0
> +
> + try:
> + ethtool_result = ethtool(f"-g {interface_name}").stdout
> + for line in ethtool_result.splitlines():
> + if line.startswith("RX:"):
> + rx_queue = int(line.split()[1])
> + if line.startswith("TX:"):
> + tx_queue = int(line.split()[1])
Does this work on devices that use combined?
> + except IndexError as exception:
> + raise KsftSkipEx(
> + f"Failed to read RX/TX queues numbers: {exception}. Not going to
> mess with them."
> + ) from exception
> +
> + if not rx_queue or not tx_queue:
> + raise KsftSkipEx(
> + "Failed to read RX/TX queues numbers. Not going to mess with
> them."
> + )
> + return rx_queue, tx_queue
> +
> +
> +def ethtool_set_rx_tx_queue(interface_name: str, rx_val: int, tx_val: int)
> -> None:
> + """Set the number of RX and TX queues to 1 using ethtool"""
> + try:
> + # This don't need to be reverted, since interfaces will be deleted
> after test
> + ethtool(f"-G {interface_name} rx {rx_val} tx {tx_val}")
> + except Exception as exception:
> + raise KsftSkipEx(
> + f"Failed to configure RX/TX queues: {exception}. Ethtool not
> available?"
> + ) from exception
> +
> +
> +def netcons_generate_random_target_name() -> str:
> + """Generate a random target name starting with 'netcons'"""
> + random_suffix = "".join(random.choices(string.ascii_lowercase +
> string.digits, k=8))
> + return f"netcons_{random_suffix}"
> +
> +
> +def netcons_create_target(
> + config_data: dict[str, str],
> + target_name: str,
> +) -> None:
> + """Create a netconsole dynamic target against the interfaces"""
> + logging.debug("Using netconsole name: %s", target_name)
> + try:
> + os.makedirs(f"{NETCONSOLE_CONFIGFS_PATH}/{target_name}",
> exist_ok=True)
> + logging.debug(
> + "Created target directory: %s/%s", NETCONSOLE_CONFIGFS_PATH,
> target_name
> + )
> + except OSError as exception:
> + if exception.errno != errno.EEXIST:
> + raise KsftFailEx(
> + f"Failed to create netconsole target directory: {exception}"
> + ) from exception
> +
> + try:
> + for key, value in config_data.items():
> + path = f"{NETCONSOLE_CONFIGFS_PATH}/{target_name}/{key}"
> + logging.debug("Writing %s to %s", key, path)
> + with open(path, "w", encoding="utf-8") as file:
> + # Always convert to string to write to file
> + file.write(str(value))
> + file.close()
> +
> + # Read all configuration values for debugging purposes
> + for debug_key in config_data.keys():
> + with open(
> + f"{NETCONSOLE_CONFIGFS_PATH}/{target_name}/{debug_key}",
> + "r",
> + encoding="utf-8",
> + ) as file:
> + content = file.read()
> + logging.debug(
> + "%s/%s/%s : %s",
> + NETCONSOLE_CONFIGFS_PATH,
> + target_name,
> + debug_key,
> + content,
> + )
> +
> + except Exception as exception:
> + raise KsftFailEx(
> + f"Failed to configure netconsole target: {exception}"
> + ) from exception
> +
> +
> +def netcons_configure_target(
> + cfg: NetDrvEpEnv, interface_name: str, target_name: str
> +) -> None:
> + """Configure netconsole on the interface with the given target name"""
> + config_data = {
> + "extended": "1",
> + "dev_name": interface_name,
> + "local_port": NETCONS_LOCAL_PORT,
> + "remote_port": NETCONS_REMOTE_PORT,
> + "local_ip": cfg.addr_v["4"] if cfg.addr_ipver == "4" else
> cfg.addr_v["6"],
> + "remote_ip": (
> + cfg.remote_addr_v["4"] if cfg.addr_ipver == "4" else
> cfg.remote_addr_v["6"]
> + ),
> + "remote_mac": "00:00:00:00:00:00", # Not important for this test
> + "enabled": "1",
> + }
> +
> + netcons_create_target(config_data, target_name)
> + logging.debug(
> + "Created netconsole target: %s on interface %s", target_name,
> interface_name
> + )
> +
> +
> +def netcons_delete_target(name: str) -> None:
> + """Delete a netconsole dynamic target"""
> + target_path = f"{NETCONSOLE_CONFIGFS_PATH}/{name}"
> + try:
> + if os.path.exists(target_path):
> + os.rmdir(target_path)
> + except OSError as exception:
> + raise KsftFailEx(
> + f"Failed to delete netconsole target: {exception}"
> + ) from exception
> +
> +
> +def netcons_load_module() -> None:
> + """Try to load the netconsole module"""
> + os.system("modprobe netconsole")
> +
> +
> +def bpftrace_call() -> None:
> + """Call bpftrace to find how many times netpoll_poll_dev() is called.
> + Output is saved in the global variable `maps`"""
> +
> + # This is going to update the global variable, that will be seen by the
> + # main function
> + global MAPS # pylint: disable=W0603
> +
> + # This will be passed to bpftrace as in bpftrace -e "expr"
> + expr = "kprobe:netpoll_poll_dev { @hits = count(); }"
> +
> + MAPS = bpftrace(expr, timeout=BPFTRACE_TIMEOUT, json=True)
> + logging.debug("BPFtrace output: %s", MAPS)
> +
> +
> +def bpftrace_start():
> + """Start a thread to call `call_bpf` in a parallel thread"""
> + global BPF_THREAD # pylint: disable=W0603
> +
> + BPF_THREAD = threading.Thread(target=bpftrace_call)
> + BPF_THREAD.start()
> + if not BPF_THREAD.is_alive():
> + raise KsftSkipEx("BPFtrace thread is not alive. Skipping test")
> +
> +
> +def bpftrace_stop() -> None:
> + """Stop the bpftrace thread"""
> + if BPF_THREAD:
> + BPF_THREAD.join()
> +
> +
> +def bpftrace_any_hit(join: bool) -> bool:
> + """Check if netpoll_poll_dev() was called by checking the global
> variable `maps`"""
> + if BPF_THREAD.is_alive():
> + if join:
> + # Wait for bpftrace to finish
> + BPF_THREAD.join()
> + else:
> + # bpftrace is still running, so, we will not check the result yet
> + return False
> +
> + logging.debug("MAPS coming from bpftrace = %s", MAPS)
> + if "hits" not in MAPS.keys():
> + raise KsftFailEx(f"bpftrace failed to run!?: {MAPS}")
> +
> + return MAPS["hits"] > 0
> +
> +
> +def do_netpoll_flush_monitored(cfg: NetDrvEpEnv, ifname: str, target_name:
> str) -> None:
> + """Print messages to the console, trying to trigger a netpoll poll"""
> + # Start bpftrace in parallel, so, it is watching
> + # netpoll_poll_dev() while we are sending netconsole messages
> + bpftrace_start()
> +
> + do_netpoll_flush(cfg, ifname, target_name)
> +
> + if bpftrace_any_hit(join=True):
> + ksft_pr("netpoll_poll_dev() was called. Success")
> + return
> +
> + raise KsftSkipEx("netpoll_poll_dev() was not called. Skipping test")
> +
> +
> +def do_netpoll_flush(cfg: NetDrvEpEnv, ifname: str, target_name: str) ->
> None:
> + """Print messages to the console, trying to trigger a netpoll poll"""
> + netcons_configure_target(cfg, ifname, target_name)
> + retry = 0
> +
> + for i in range(int(ITERATIONS)):
> + if not BPF_THREAD.is_alive():
> + # bpftrace is done, stop sending messages
> + break
> +
> + msg = f"netcons test #{i}"
> + with open("/dev/kmsg", "w", encoding="utf-8") as kmsg:
> + for j in range(10):
> + try:
> + kmsg.write(f"{msg}-{j}\n")
> + except OSError as exception:
> + # in some cases, kmsg can be busy, so, we will retry
> + time.sleep(1)
> + retry += 1
> + if retry < 5:
> + logging.info("Failed to write to kmsg. Retrying")
> + # Just retry a few times
> + continue
> + raise KsftFailEx(
> + f"Failed to write to kmsg: {exception}"
> + ) from exception
> +
> + if bpftrace_any_hit(join=False):
> + # Check if netpoll_poll_dev() was called, but do not wait
> for it
> + # to finish.
> + ksft_pr("netpoll_poll_dev() was called. Success")
> + return
> +
> + # Every 5 iterations, toggle netconsole
> + netcons_delete_target(target_name)
> + netcons_configure_target(cfg, ifname, target_name)
> + # If we sleep here, we will have a better chance of triggering
> + # This number is based on a few tests I ran while developing this
> test
> + time.sleep(0.4)
> +
> +
> +def test_netpoll(cfg: NetDrvEpEnv) -> None:
> + """
> + Test netpoll by sending traffic to the interface and then sending
> + netconsole messages to trigger a poll
> + """
> +
> + target_name = netcons_generate_random_target_name()
> + ifname = cfg.dev["ifname"]
> + traffic = None
> + original_queues = ethtool_read_rx_tx_queue(ifname)
> +
> + try:
> + # Set RX/TX queues to 1 to force congestion
> + ethtool_set_rx_tx_queue(ifname, 1, 1)
> +
> + traffic = GenerateTraffic(cfg)
> + do_netpoll_flush_monitored(cfg, ifname, target_name)
> + finally:
> + if traffic:
> + traffic.stop()
> +
> + # Revert RX/TX queues
> + ethtool_set_rx_tx_queue(ifname, original_queues[0],
> original_queues[1])
> + netcons_delete_target(target_name)
> + bpftrace_stop()
> +
> +
> +def test_check_dependencies() -> None:
> + """Check if the dependencies are met"""
> + if not os.path.exists(NETCONSOLE_CONFIGFS_PATH):
> + raise KsftSkipEx(
> + f"Directory {NETCONSOLE_CONFIGFS_PATH} does not exist.
> CONFIG_NETCONSOLE_DYNAMIC might not be set." # pylint: disable=C0301
> + )
> +
> +
> +def main() -> None:
> + """Main function to run the test"""
> + netcons_load_module()
> + test_check_dependencies()
> + with NetDrvEpEnv(__file__, nsim_test=True) as cfg:
> + ksft_run(
> + [test_netpoll],
> + args=(cfg,),
> + )
> + ksft_exit()
> +
> +
> +if __name__ == "__main__":
> + main()
>
> --
> 2.47.1
>
