testing: net-drv: add a driver test for stats reporting

Add a very simple test to make sure drivers report expected
stats. Drivers which implement FEC or pause configuration
should report relevant stats. Qstats must be reported,
at least packet and byte counts, and they must match
total device stats.

Tested with netdevsim, bnxt, in-tree and installed.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+from lib.py import ksft_run, ksft_in, ksft_true, KsftSkipEx, KsftXfailEx
+from lib.py import EthtoolFamily, NetdevFamily, RtnlFamily, NlError
+from lib.py import NetDrvEnv
+
+ethnl = EthtoolFamily()
+netfam = NetdevFamily()
+rtnl = RtnlFamily()
+
+
+def check_pause(cfg) -> None:
+    global ethnl
+
+    try:
+        ethnl.pause_get({"header": {"dev-index": cfg.ifindex}})
+    except NlError as e:
+        if e.error == 95:
+            raise KsftXfailEx("pause not supported by the device")
+        raise
+
+    data = ethnl.pause_get({"header": {"dev-index": cfg.ifindex,
+                                       "flags": {'stats'}}})
+    ksft_true(data['stats'], "driver does not report stats")
+
+
+def check_fec(cfg) -> None:
+    global ethnl
+
+    try:
+        ethnl.fec_get({"header": {"dev-index": cfg.ifindex}})
+    except NlError as e:
+        if e.error == 95:
+            raise KsftXfailEx("FEC not supported by the device")
+        raise
+
+    data = ethnl.fec_get({"header": {"dev-index": cfg.ifindex,
+                                     "flags": {'stats'}}})
+    ksft_true(data['stats'], "driver does not report stats")
+
+
+def pkt_byte_sum(cfg) -> None:
+    global netfam, rtnl
+
+    def get_qstat(test):
+        global netfam
+        stats = netfam.qstats_get({}, dump=True)
+        if stats:
+            for qs in stats:
+                if qs["ifindex"]== test.ifindex:
+                    return qs
+
+    qstat = get_qstat(cfg)
+    if qstat is None:
+        raise KsftSkipEx("qstats not supported by the device")
+
+    for key in ['tx-packets', 'tx-bytes', 'rx-packets', 'rx-bytes']:
+        ksft_in(key, qstat, "Drivers should always report basic keys")
+
+    # Compare stats, rtnl stats and qstats must match,
+    # but the interface may be up, so do a series of dumps
+    # each time the more "recent" stats must be higher or same.
+    def stat_cmp(rstat, qstat):
+        for key in ['tx-packets', 'tx-bytes', 'rx-packets', 'rx-bytes']:
+            if rstat[key] != qstat[key]:
+                return rstat[key] - qstat[key]
+        return 0
+
+    for _ in range(10):
+        rtstat = rtnl.getlink({"ifi-index": cfg.ifindex})['stats']
+        if stat_cmp(rtstat, qstat) < 0:
+            raise Exception("RTNL stats are lower, fetched later")
+        qstat = get_qstat(cfg)
+        if stat_cmp(rtstat, qstat) > 0:
+            raise Exception("Qstats are lower, fetched later")
+
+
+def main() -> None:
+    with NetDrvEnv(__file__) as cfg:
+        ksft_run([check_pause, check_fec, pkt_byte_sum],
+                 args=(cfg, ))
+
+
+if __name__ == "__main__":
+    main()