tests: can: add basic tests of CAN interface driver

The tests require the `vcan` kernel module to be available, and a
`vcan0` module must ve created manually before running the tests.

The `vcan` kernel module is not available in the Github Runner (azure)
images, but a request has been submitted to enable it in the Azure
kernel packages:
actions/runner-images#13991

Signed-off-by: Martin Hundebøll <martin@geanix.com>

Author: hundeboll

tests/test_can.py

@@ -0,0 +1,82 @@
+import socket
+
+import pytest
+
+from labgrid.driver import CanInterfaceDriver
+from labgrid.driver.caninterfacedriver import CanFdFrame, CanFilter, CanFrame
+from labgrid.resource import NetworkInterface
+
+
+FRAMES = (
+    CanFrame(0x123, b'\x01'),
+    CanFrame(0x456, b'\x11\x22\x33\x44\x55\x66\x77\x88'),
+    CanFrame(0x789, b'\x44\x33\x22\x11'),
+)
+
+
+FRAMES_FD = (
+    CanFdFrame(0x123, b'\x01'),
+    CanFdFrame(0x456, b'\x11\x22\x33\x44\x55\x66\x77\x88'),
+    CanFdFrame(0x789, b'\x44\x33\x22\x11', flags=CanFdFrame.BRS),
+    CanFdFrame(0x765, b'\xff' * 64),
+)
+
+
+def vcan0_exists():
+    try:
+        socket.if_nametoindex("vcan0")
+        return True
+    except OSError:
+        return False
+
+
+pytestmark = pytest.mark.skipif(not vcan0_exists(), reason="Virtual CAN interface not found")
+
+
+@pytest.fixture
+def vcan():
+    sock = socket.socket(socket.PF_CAN, socket.SOCK_RAW | socket.SOCK_NONBLOCK, socket.CAN_RAW)
+    sock.bind(("vcan0",))
+
+    return sock
+
+
+@pytest.mark.parametrize("frame", FRAMES)
+def test_can_frames(target, vcan, frame):
+    iface = NetworkInterface(target, "vcan", "vcan0")
+    can = CanInterfaceDriver(target, "vcan", "500000")
+    target.activate(can)
+
+    vcan.send(frame.to_bytes())
+    assert can.recv() == frame
+
+
+@pytest.mark.parametrize("frame", FRAMES_FD)
+def test_can_frames_fd(target, vcan, frame):
+    iface = NetworkInterface(target, "vcan", "vcan0")
+    can = CanInterfaceDriver(target, "vcan", "500000", "2000000")
+    target.activate(can)
+
+    vcan.setsockopt(socket.SOL_CAN_RAW, socket.CAN_RAW_FD_FRAMES, 1)
+
+    vcan.send(frame.to_bytes())
+    assert can.recv() == frame
+
+
+def test_can_filer(target, vcan):
+    iface = NetworkInterface(target, "vcan", "vcan0")
+    can = CanInterfaceDriver(target, "vcan", "500000")
+    target.activate(can)
+
+    can.filter([CanFilter(0x123), CanFilter(0x002, 0x003)])
+
+    frame = CanFrame(0x123, b'\x01')
+    vcan.send(frame.to_bytes())
+    assert can.recv() == frame
+
+    vcan.send(CanFrame(0x321, b'\x02').to_bytes())
+    vcan.send(frame.to_bytes())
+    assert can.recv() == frame
+
+    vcan.send(CanFrame(0x012, b'\x03').to_bytes())
+    assert can.recv()