selftests: net: add scaffolding for Netlink tests in Python

Add glue code for accessing the YNL library which lives under
tools/net and YAML spec files from under Documentation/.
Automatically figure out if tests are run in tree or not.
Since we'll want to use this library both from net and
drivers/net test targets make the library a target as well,
and automatically include it when net or drivers/net are
included. Making net/lib a target ensures that we end up
with only one copy of it, and saves us some path guessing.

Add a tiny bit of formatting support to be able to output KTAP
from the start.

Reviewed-by: Petr Machata <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

tools/testing/selftests/Makefile

···
 TARGETS_HOTPLUG = cpu-hotplug
 TARGETS_HOTPLUG += memory-hotplug
 
+# Networking tests want the net/lib target, include it automatically
+ifneq ($(filter net,$(TARGETS)),)
+ifeq ($(filter net/lib,$(TARGETS)),)
+	INSTALL_DEP_TARGETS := net/lib
+endif
+endif
+
 # User can optionally provide a TARGETS skiplist.  By default we skip
 # BPF since it has cutting edge build time dependencies which require
 # more effort to install.
···
 	install -m 744 run_kselftest.sh $(INSTALL_PATH)/
 	rm -f $(TEST_LIST)
 	@ret=1;	\
-	for TARGET in $(TARGETS); do \
+	for TARGET in $(TARGETS) $(INSTALL_DEP_TARGETS); do \
 		BUILD_TARGET=$$BUILD/$$TARGET;	\
 		$(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET install \
 				INSTALL_PATH=$(INSTALL_PATH)/$$TARGET \

tools/testing/selftests/net/lib/Makefile

···
+# SPDX-License-Identifier: GPL-2.0
+
+TEST_FILES := ../../../../../Documentation/netlink/specs
+TEST_FILES += ../../../../net/ynl
+
+TEST_INCLUDES := $(wildcard py/*.py)
+
+include ../../lib.mk

tools/testing/selftests/net/lib/py/__init__.py

···
+# SPDX-License-Identifier: GPL-2.0
+
+from .consts import KSRC
+from .ksft import *
+from .utils import *
+from .ynl import NlError, YnlFamily, EthtoolFamily, NetdevFamily, RtnlFamily

tools/testing/selftests/net/lib/py/consts.py

···
+# SPDX-License-Identifier: GPL-2.0
+
+import sys
+from pathlib import Path
+
+KSFT_DIR = (Path(__file__).parent / "../../..").resolve()
+KSRC = (Path(__file__).parent / "../../../../../..").resolve()
+
+KSFT_MAIN_NAME = Path(sys.argv[0]).with_suffix("").name

tools/testing/selftests/net/lib/py/ksft.py

···
+# SPDX-License-Identifier: GPL-2.0
+
+import builtins
+from .consts import KSFT_MAIN_NAME
+
+KSFT_RESULT = None
+
+
+class KsftSkipEx(Exception):
+    pass
+
+
+class KsftXfailEx(Exception):
+    pass
+
+
+def ksft_pr(*objs, **kwargs):
+    print("#", *objs, **kwargs)
+
+
+def ksft_eq(a, b, comment=""):
+    global KSFT_RESULT
+    if a != b:
+        KSFT_RESULT = False
+        ksft_pr("Check failed", a, "!=", b, comment)
+
+
+def ksft_true(a, comment=""):
+    global KSFT_RESULT
+    if not a:
+        KSFT_RESULT = False
+        ksft_pr("Check failed", a, "does not eval to True", comment)
+
+
+def ksft_in(a, b, comment=""):
+    global KSFT_RESULT
+    if a not in b:
+        KSFT_RESULT = False
+        ksft_pr("Check failed", a, "not in", b, comment)
+
+
+def ksft_ge(a, b, comment=""):
+    global KSFT_RESULT
+    if a < b:
+        KSFT_RESULT = False
+        ksft_pr("Check failed", a, "<", b, comment)
+
+
+def ktap_result(ok, cnt=1, case="", comment=""):
+    res = ""
+    if not ok:
+        res += "not "
+    res += "ok "
+    res += str(cnt) + " "
+    res += KSFT_MAIN_NAME
+    if case:
+        res += "." + str(case.__name__)
+    if comment:
+        res += " # " + comment
+    print(res)
+
+
+def ksft_run(cases, args=()):
+    totals = {"pass": 0, "fail": 0, "skip": 0, "xfail": 0}
+
+    print("KTAP version 1")
+    print("1.." + str(len(cases)))
+
+    global KSFT_RESULT
+    cnt = 0
+    for case in cases:
+        KSFT_RESULT = True
+        cnt += 1
+        try:
+            case(*args)
+        except KsftSkipEx as e:
+            ktap_result(True, cnt, case, comment="SKIP " + str(e))
+            totals['skip'] += 1
+            continue
+        except KsftXfailEx as e:
+            ktap_result(True, cnt, case, comment="XFAIL " + str(e))
+            totals['xfail'] += 1
+            continue
+        except Exception as e:
+            for line in str(e).split('\n'):
+                ksft_pr("Exception|", line)
+            ktap_result(False, cnt, case)
+            totals['fail'] += 1
+            continue
+
+        ktap_result(KSFT_RESULT, cnt, case)
+        totals['pass'] += 1
+
+    print(
+        f"# Totals: pass:{totals['pass']} fail:{totals['fail']} xfail:{totals['xfail']} xpass:0 skip:{totals['skip']} error:0"
+    )

tools/testing/selftests/net/lib/py/utils.py

···
+# SPDX-License-Identifier: GPL-2.0
+
+import json as _json
+import subprocess
+
+class cmd:
+    def __init__(self, comm, shell=True, fail=True, ns=None, background=False):
+        if ns:
+            if isinstance(ns, NetNS):
+                ns = ns.name
+            comm = f'ip netns exec {ns} ' + comm
+
+        self.stdout = None
+        self.stderr = None
+        self.ret = None
+
+        self.comm = comm
+        self.proc = subprocess.Popen(comm, shell=shell, stdout=subprocess.PIPE,
+                                     stderr=subprocess.PIPE)
+        if not background:
+            self.process(terminate=False, fail=fail)
+
+    def process(self, terminate=True, fail=None):
+        if terminate:
+            self.proc.terminate()
+        stdout, stderr = self.proc.communicate()
+        self.stdout = stdout.decode("utf-8")
+        self.stderr = stderr.decode("utf-8")
+        self.proc.stdout.close()
+        self.proc.stderr.close()
+        self.ret = self.proc.returncode
+
+        if self.proc.returncode != 0 and fail:
+            if len(stderr) > 0 and stderr[-1] == "\n":
+                stderr = stderr[:-1]
+            raise Exception("Command failed: %s\n%s" % (self.proc.args, stderr))
+
+
+def ip(args, json=None, ns=None):
+    cmd_str = "ip "
+    if json:
+        cmd_str += '-j '
+    cmd_str += args
+    cmd_obj = cmd(cmd_str, ns=ns)
+    if json:
+        return _json.loads(cmd_obj.stdout)
+    return cmd_obj

tools/testing/selftests/net/lib/py/ynl.py

···
+# SPDX-License-Identifier: GPL-2.0
+
+import sys
+from pathlib import Path
+from .consts import KSRC, KSFT_DIR
+from .ksft import ksft_pr, ktap_result
+
+# Resolve paths
+try:
+    if (KSFT_DIR / "kselftest-list.txt").exists():
+        # Running in "installed" selftests
+        tools_full_path = KSFT_DIR
+        SPEC_PATH = KSFT_DIR / "net/lib/specs"
+
+        sys.path.append(tools_full_path.as_posix())
+        from net.lib.ynl.lib import YnlFamily, NlError
+    else:
+        # Running in tree
+        tools_full_path = KSRC / "tools"
+        SPEC_PATH = KSRC / "Documentation/netlink/specs"
+
+        sys.path.append(tools_full_path.as_posix())
+        from net.ynl.lib import YnlFamily, NlError
+except ModuleNotFoundError as e:
+    ksft_pr("Failed importing `ynl` library from kernel sources")
+    ksft_pr(str(e))
+    ktap_result(True, comment="SKIP")
+    sys.exit(4)
+
+#
+# Wrapper classes, loading the right specs
+# Set schema='' to avoid jsonschema validation, it's slow
+#
+class EthtoolFamily(YnlFamily):
+    def __init__(self):
+        super().__init__((SPEC_PATH / Path('ethtool.yaml')).as_posix(),
+                         schema='')
+
+
+class RtnlFamily(YnlFamily):
+    def __init__(self):
+        super().__init__((SPEC_PATH / Path('rt_link.yaml')).as_posix(),
+                         schema='')
+
+
+class NetdevFamily(YnlFamily):
+    def __init__(self):
+        super().__init__((SPEC_PATH / Path('netdev.yaml')).as_posix(),
+                         schema='')