selftests: drv-net: test dumping qstats per device

Add a test for dumping qstats device by device.

ksft framework grows a ksft_raises() helper, to be used
under with, which should be familiar to unittest users.

Link: https://lore.kernel.org/r/20240420023543.3300306-5-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/drivers/net/stats.py

 #!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0
 
-from lib.py import ksft_run, ksft_exit
-from lib.py import ksft_in, ksft_true, KsftSkipEx, KsftXfailEx
+from lib.py import ksft_run, ksft_exit, ksft_pr
+from lib.py import ksft_ge, ksft_eq, ksft_in, ksft_true, ksft_raises, KsftSkipEx, KsftXfailEx
 from lib.py import EthtoolFamily, NetdevFamily, RtnlFamily, NlError
 from lib.py import NetDrvEnv
 
@@ -77,9 +77,65 @@ def pkt_byte_sum(cfg) -> None:
             raise Exception("Qstats are lower, fetched later")
 
 
+def qstat_by_ifindex(cfg) -> None:
+    global netfam
+    global rtnl
+
+    # Construct a map ifindex -> [dump, by-index, dump]
+    ifindexes = {}
+    stats = netfam.qstats_get({}, dump=True)
+    for entry in stats:
+        ifindexes[entry['ifindex']] = [entry, None, None]
+
+    for ifindex in ifindexes.keys():
+        entry = netfam.qstats_get({"ifindex": ifindex}, dump=True)
+        ksft_eq(len(entry), 1)
+        ifindexes[entry[0]['ifindex']][1] = entry[0]
+
+    stats = netfam.qstats_get({}, dump=True)
+    for entry in stats:
+        ifindexes[entry['ifindex']][2] = entry
+
+    if len(ifindexes) == 0:
+        raise KsftSkipEx("No ifindex supports qstats")
+
+    # Now make sure the stats match/make sense
+    for ifindex, triple in ifindexes.items():
+        all_keys = triple[0].keys() | triple[1].keys() | triple[2].keys()
+
+        for key in all_keys:
+            ksft_ge(triple[1][key], triple[0][key], comment="bad key: " + key)
+            ksft_ge(triple[2][key], triple[1][key], comment="bad key: " + key)
+
+    # Test invalid dumps
+    # 0 is invalid
+    with ksft_raises(NlError) as cm:
+        netfam.qstats_get({"ifindex": 0}, dump=True)
+    ksft_eq(cm.exception.nl_msg.error, -34)
+    ksft_eq(cm.exception.nl_msg.extack['bad-attr'], '.ifindex')
+
+    # loopback has no stats
+    with ksft_raises(NlError) as cm:
+        netfam.qstats_get({"ifindex": 1}, dump=True)
+    ksft_eq(cm.exception.nl_msg.error, -95)
+    ksft_eq(cm.exception.nl_msg.extack['bad-attr'], '.ifindex')
+
+    # Try to get stats for lowest unused ifindex but not 0
+    devs = rtnl.getlink({}, dump=True)
+    all_ifindexes = set([dev["ifi-index"] for dev in devs])
+    lowest = 2
+    while lowest in all_ifindexes:
+        lowest += 1
+
+    with ksft_raises(NlError) as cm:
+        netfam.qstats_get({"ifindex": lowest}, dump=True)
+    ksft_eq(cm.exception.nl_msg.error, -19)
+    ksft_eq(cm.exception.nl_msg.extack['bad-attr'], '.ifindex')
+
+
 def main() -> None:
     with NetDrvEnv(__file__) as cfg:
-        ksft_run([check_pause, check_fec, pkt_byte_sum],
+        ksft_run([check_pause, check_fec, pkt_byte_sum, qstat_by_ifindex],
                  args=(cfg, ))
     ksft_exit()
 

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

@@ -53,6 +53,24 @@ def ksft_ge(a, b, comment=""):
         _fail("Check failed", a, "<", b, comment)
 
 
+class ksft_raises:
+    def __init__(self, expected_type):
+        self.exception = None
+        self.expected_type = expected_type
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        if exc_type is None:
+            _fail(f"Expected exception {str(self.expected_type.__name__)}, none raised")
+        elif self.expected_type != exc_type:
+            _fail(f"Expected exception {str(self.expected_type.__name__)}, raised {str(exc_type.__name__)}")
+        self.exception = exc_val
+        # Suppress the exception if its the expected one
+        return self.expected_type == exc_type
+
+
 def ksft_busy_wait(cond, sleep=0.005, deadline=1, comment=""):
     end = time.monotonic() + deadline
     while True: