Hostap Hwsim Tests

The hostap project consists of wpa_supplicant and hostapd, used for WiFi clients and APs respectively. The project includes a number of tests, many of which are run under a hwsim-based test framework. They rely on the mac80211_hwsim kernel module, which provides support for simulated client and AP devices. See the upstream project documentation for more info.

The upstream test framework is integrated within Chrome OS to run via the wifi.HostapHwsim Tast test wrapper. This test has some limited software dependencies, which are installed via the USE=wifi_hostap_test feature flag. Currently, this USE flag is enabled only on BOARD=amd64-generic and those that inherit from it. The easiest way to use the tests is via a VM target, like BOARD=betty (Google-only).

See these slides (Google-only) for a rough primer on how and why they were integrated into Chrome OS.


Below is a walkthrough on building and running a VM test, and modifying the tests yourself. See the cros_vm docs for more thorough VM instructions.

# Build a board for a VM.
export BOARD=betty
./build_packages --board=${BOARD}
./build_image --board=${BOARD} test

# Start the VM.
cros_vm --start --board=${BOARD}

# Run the validity test.
tast -verbose run localhost:9222 wifi.HostapHwsim.validity

# Make modifications.
## Find the appropriate src/third_party/wpa_supplicant-*/
## source tree. See the hostap-test ebuild for its CROS_WORKON_LOCALNAME:
## That is, src/third_party/wpa_supplicant-2.8 as of May 2020.
## Make your modifications to, e.g., tests/hwsim/test_<relevant_module>.py, or
## wpa_supplicant/<foo>.c.

# Deploy modifications.
cros_workon-${BOARD} start hostap-test
emerge-${BOARD} hostap-test && cros deploy --root=/usr/local localhost:9222 hostap-test

# Rerun validity tests.
tast -verbose run localhost:9222 wifi.HostapHwsim.validity

# Run a specific module, the 'ap_roam' module.
tast -verbose run -var=wifi.HostapHwsim.runArgs='-f ap_roam' \
    localhost:9222 wifi.HostapHwsim.full


  • Pitfall: Tests are packaged via the net-wireless/hostap-test package, not the net-wireless/wpa_supplicant or net-wireless/hostapd packages. Be sure to cros_workon and cros deploy the correct one.
  • Pitfall: Until cros deploy learns to deploy to the correct root, remember to use --root=/usr/local with cros deploy. Test-image-only packages are installed at /usr/local, so you should deploy the hostap-test package there too.
  • Logs are stored to the Tast results directory (/tmp/tast/results/latest/tests/wifi.HostapHwsim.*/). These include kernel logs and logs for one or more hostapd or wpa_supplicant instance, as well as packet captures.
  • You can pass arbitrary arguments to the wifi.HostapHwsim.full variant via the -var=wifi.HostapHwsim.runArgs='...' parameter, to run specific tests, or to add extra debugging information. e.g., the -T parameter captures kernel tracing information via trace-cmd. See the --help descriptions for more info:
localhost ~ # /usr/local/libexec/hostap/tests/hwsim/ -h
/usr/local/libexec/hostap/tests/hwsim/ [-v | --valgrind | valgrind] [-t | --trace | trace]
	[-n <num> | --channels <num>] [-B | --build]
	[-c | --codecov ] [ parameters]
localhost ~ # /usr/local/libexec/hostap/tests/hwsim/ -h
usage: [-h] [--logdir <directory>] [-d | -q] [-S <sqlite3 db>]
                    [--prefill-tests] [--commit <commit id>] [-b <build>] [-L]
                    [-T] [-D] [--dbus] [--shuffle-tests] [--split SPLIT]
                    [--no-reset] [--long]
                    [-f <test module> [<test module> ...]] [-l <modules file>]
                    [<test> [<test> ...]]

hwsim test runner

positional arguments:
  <test>                tests to run (only valid without -f)

optional arguments:
  -h, --help            show this help message and exit
  --logdir <directory>  log output directory for all other options, must be
                        given if other log options are used
  -d                    verbose debug output
  -q                    be quiet
  -S <sqlite3 db>       database to write results to
  --prefill-tests       prefill test database with NOTRUN before all tests
  --commit <commit id>  commit ID, only for database
  -b <build>            build ID
  -L                    List tests (and update descriptions in DB)
  -T                    collect tracing per test case (in log directory)
  -D                    collect dmesg per test case (in log directory)
  --dbus                collect dbus per test case (in log directory)
  --shuffle-tests       Shuffle test cases to randomize order
  --split SPLIT         split tests for parallel execution (<server
                        number>/<total servers>)
  --no-reset            Do not reset devices at the end of the test
  --long                Include test cases that take long time
  -f <test module> [<test module> ...]
                        execute only tests from these test modules
  -l <modules file>     test modules file name
  -i                    stdin-controlled test case execution