[net-next,6/7] selftests: drivers: add scaffolding for Netlink tests in Python

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 0cffdfb4b116..d015ec14a85e 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -17,6 +17,7 @@  TARGETS += devices
 TARGETS += dmabuf-heaps
 TARGETS += drivers/dma-buf
 TARGETS += drivers/s390x/uvdevice
+TARGETS += drivers/net
 TARGETS += drivers/net/bonding
 TARGETS += drivers/net/team
 TARGETS += dt
@@ -117,7 +118,7 @@  TARGETS_HOTPLUG = cpu-hotplug
 TARGETS_HOTPLUG += memory-hotplug
 
 # Networking tests want the net/lib target, include it automatically
-ifneq ($(filter net ,$(TARGETS)),)
+ifneq ($(filter net drivers/net,$(TARGETS)),)
 ifeq ($(filter net/lib,$(TARGETS)),)
 	override TARGETS := $(TARGETS) net/lib
 endif
diff --git a/tools/testing/selftests/drivers/net/Makefile b/tools/testing/selftests/drivers/net/Makefile
new file mode 100644
index 000000000000..379cdb1960a7
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/Makefile
@@ -0,0 +1,7 @@ 
+# SPDX-License-Identifier: GPL-2.0
+
+TEST_INCLUDES := $(wildcard lib/py/*.py)
+
+TEST_PROGS := stats.py
+
+include ../../lib.mk
diff --git a/tools/testing/selftests/drivers/net/README.rst b/tools/testing/selftests/drivers/net/README.rst
new file mode 100644
index 000000000000..5ef7c417d431
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/README.rst
@@ -0,0 +1,30 @@ 
+Running tests
+=============
+
+Tests are executed within kselftest framework like any other tests.
+By default tests execute against software drivers such as netdevsim.
+All tests must support running against a real device (SW-only tests
+should instead be placed in net/ or drivers/net/netdevsim, HW-only
+tests in drivers/net/hw).
+
+Set appropriate variables to point the tests at a real device.
+
+Variables
+=========
+
+Variables can be set in the environment or by creating a net.config
+file in the same directory as this README file. Example::
+
+  $ NETIF=eth0 ./some_test.sh
+
+or::
+
+  $ cat tools/testing/selftests/drivers/net/net.config
+  # Variable set in a file
+  NETIF=eth0
+
+NETIF
+~~~~~
+
+Name of the netdevice against which the test should be executed.
+When empty or not set software devices will be used.
diff --git a/tools/testing/selftests/drivers/net/lib/py/__init__.py b/tools/testing/selftests/drivers/net/lib/py/__init__.py
new file mode 100644
index 000000000000..4653dffcd962
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/lib/py/__init__.py
@@ -0,0 +1,17 @@ 
+# SPDX-License-Identifier: GPL-2.0
+
+import sys
+from pathlib import Path
+
+KSFT_DIR = (Path(__file__).parent / "../../../..").resolve()
+
+try:
+    sys.path.append(KSFT_DIR.as_posix())
+    from net.lib.py import *
+except ModuleNotFoundError as e:
+    ksft_pr("Failed importing `net` library from kernel sources")
+    ksft_pr(str(e))
+    ktap_result(True, comment="SKIP")
+    sys.exit(4)
+
+from .env import *
diff --git a/tools/testing/selftests/drivers/net/lib/py/env.py b/tools/testing/selftests/drivers/net/lib/py/env.py
new file mode 100644
index 000000000000..ee4a44555d83
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/lib/py/env.py
@@ -0,0 +1,41 @@ 
+# SPDX-License-Identifier: GPL-2.0
+
+import os
+import shlex
+from pathlib import Path
+from lib.py import ip
+from lib.py import NetdevSimDev
+
+class NetDrvEnv:
+    def __init__(self, src_path):
+        self.env = os.environ.copy()
+        self._load_env_file(src_path)
+
+        if 'NETIF' in self.env:
+            self._ns = None
+            self.dev = ip("link show dev " + self.env['NETIF'], json=True)[0]
+        else:
+            self._ns = NetdevSimDev()
+            self.dev = self._ns.nsims[0].dev
+        self.ifindex = self.dev['ifindex']
+
+    def __del__(self):
+        if self._ns:
+            self._ns.remove()
+
+    def _load_env_file(self, src_path):
+        src_dir = Path(src_path).parent.resolve()
+        if not (src_dir / "net.config").exists():
+            return
+
+        lexer = shlex.shlex(open((src_dir / "net.config").as_posix(), 'r').read())
+        k = None
+        for token in lexer:
+            if k is None:
+                k = token
+                self.env[k] = ""
+            elif token == "=":
+                pass
+            else:
+                self.env[k] = token
+                k = None
diff --git a/tools/testing/selftests/net/lib/py/__init__.py b/tools/testing/selftests/net/lib/py/__init__.py
index 81a8d14b68f0..99cfc8dc4dca 100644
--- a/tools/testing/selftests/net/lib/py/__init__.py
+++ b/tools/testing/selftests/net/lib/py/__init__.py
@@ -3,4 +3,5 @@ 
 from .ksft import *
 from .ynl import NlError, YnlFamily, EthtoolFamily, NetdevFamily, RtnlFamily
 from .consts import KSRC
+from .nsim import *
 from .utils import *
diff --git a/tools/testing/selftests/net/lib/py/nsim.py b/tools/testing/selftests/net/lib/py/nsim.py
new file mode 100644
index 000000000000..13eb42c82829
--- /dev/null
+++ b/tools/testing/selftests/net/lib/py/nsim.py
@@ -0,0 +1,118 @@ 
+# SPDX-License-Identifier: GPL-2.0
+
+import json
+import os
+import random
+import re
+import time
+from .utils import cmd, ip
+
+
+class NetdevSim:
+    """
+    Class for netdevsim netdevice and its attributes.
+    """
+
+    def __init__(self, nsimdev, port_index, ifname, ns=None):
+        # In case udev renamed the netdev to according to new schema,
+        # check if the name matches the port_index.
+        nsimnamere = re.compile("eni\d+np(\d+)")
+        match = nsimnamere.match(ifname)
+        if match and int(match.groups()[0]) != port_index + 1:
+            raise Exception("netdevice name mismatches the expected one")
+
+        self.ifname = ifname
+        self.nsimdev = nsimdev
+        self.port_index = port_index
+        self.ns = ns
+        self.dfs_dir = "%s/ports/%u/" % (nsimdev.dfs_dir, port_index)
+        ret = ip("-j link show dev %s" % ifname, ns=ns)
+        self.dev = json.loads(ret.stdout)[0]
+
+    def dfs_write(self, path, val):
+        self.nsimdev.dfs_write(f'ports/{self.port_index}/' + path, val)
+
+
+class NetdevSimDev:
+    """
+    Class for netdevsim bus device and its attributes.
+    """
+    @staticmethod
+    def ctrl_write(path, val):
+        fullpath = os.path.join("/sys/bus/netdevsim/", path)
+        with open(fullpath, "w") as f:
+            f.write(val)
+
+    def dfs_write(self, path, val):
+        fullpath = os.path.join(f"/sys/kernel/debug/netdevsim/netdevsim{self.addr}/", path)
+        with open(fullpath, "w") as f:
+            f.write(val)
+
+    def __init__(self, port_count=1, ns=None):
+        # nsim will spawn in init_net, we'll set to actual ns once we switch it the.sre
+        self.ns = None
+
+        if not os.path.exists("/sys/bus/netdevsim"):
+            cmd("modprobe netdevsim")
+
+        addr = random.randrange(1 << 15)
+        while True:
+            try:
+                self.ctrl_write("new_device", "%u %u" % (addr, port_count))
+            except OSError as e:
+                if e.errno == errno.ENOSPC:
+                    addr = random.randrange(1 << 15)
+                    continue
+                raise e
+            break
+        self.addr = addr
+
+        # As probe of netdevsim device might happen from a workqueue,
+        # so wait here until all netdevs appear.
+        self.wait_for_netdevs(port_count)
+
+        if ns:
+            cmd(f"devlink dev reload netdevsim/netdevsim{addr} netns {ns.name}")
+            self.ns = ns
+
+        cmd("udevadm settle", ns=self.ns)
+        ifnames = self.get_ifnames()
+
+        self.dfs_dir = "/sys/kernel/debug/netdevsim/netdevsim%u/" % addr
+
+        self.nsims = []
+        for port_index in range(port_count):
+            self.nsims.append(NetdevSim(self, port_index, ifnames[port_index],
+                                        ns=ns))
+
+    def get_ifnames(self):
+        ifnames = []
+        listdir = cmd(f"ls /sys/bus/netdevsim/devices/netdevsim{self.addr}/net/",
+                      ns=self.ns).stdout.split()
+        for ifname in listdir:
+            ifnames.append(ifname)
+        ifnames.sort()
+        return ifnames
+
+    def wait_for_netdevs(self, port_count):
+        timeout = 5
+        timeout_start = time.time()
+
+        while True:
+            try:
+                ifnames = self.get_ifnames()
+            except FileNotFoundError as e:
+                ifnames = []
+            if len(ifnames) == port_count:
+                break
+            if time.time() < timeout_start + timeout:
+                continue
+            raise Exception("netdevices did not appear within timeout")
+
+    def remove(self):
+        self.ctrl_write("del_device", "%u" % (self.addr, ))
+
+    def remove_nsim(self, nsim):
+        self.nsims.remove(nsim)
+        self.ctrl_write("devices/netdevsim%u/del_port" % (self.addr, ),
+                        "%u" % (nsim.port_index, ))