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Testing a network device that has large numbers of bytes/packets may
overflow. Using stats64 when comparing fixes this problem.
I tripped on this while iterating on a qstats patch for mlx5. See below
for confirmation without my added code that this is a bug.
Before this patch (with added debugging output):
$ NETIF=eth0 tools/testing/selftests/drivers/net/stats.py
KTAP version 1
1..4
ok 1 stats.check_pause
ok 2 stats.check_fec
rstat: 481708634 qstat: 666201639514 key: tx-bytes
not ok 3 stats.pkt_byte_sum
ok 4 stats.qstat_by_ifindex
Note the huge delta above ^^^ in the rtnl vs qstats.
After this patch:
$ NETIF=eth0 tools/testing/selftests/drivers/net/stats.py
KTAP version 1
1..4
ok 1 stats.check_pause
ok 2 stats.check_fec
ok 3 stats.pkt_byte_sum
ok 4 stats.qstat_by_ifindex
It looks like rtnl_fill_stats in net/core/rtnetlink.c will attempt to
copy the 64bit stats into a 32bit structure which is probably why this
behavior is occurring.
To show this is happening, you can get the underlying stats that the
stats.py test uses like this:
$ ./cli.py --spec ../../../Documentation/netlink/specs/rt_link.yaml \
--do getlink --json '{"ifi-index": 7}'
And examine the output (heavily snipped to show relevant fields):
'stats': {
'multicast': 3739197,
'rx-bytes': 1201525399,
'rx-packets': 56807158,
'tx-bytes': 492404458,
'tx-packets': 1200285371,
'stats64': {
'multicast': 3739197,
'rx-bytes': 35561263767,
'rx-packets': 56807158,
'tx-bytes': 666212335338,
'tx-packets': 1200285371,
The stats.py test prior to this patch was using the 'stats' structure
above, which matches the failure output on my system.
Comparing side by side, rx-bytes and tx-bytes, and getting ethtool -S
output:
rx-bytes stats: 1201525399
rx-bytes stats64: 35561263767
rx-bytes ethtool: 36203402638
tx-bytes stats: 492404458
tx-bytes stats64: 666212335338
tx-bytes ethtool: 666215360113
Note that the above was taken from a system with an mlx5 NIC, which only
exposes ndo_get_stats64.
Based on the ethtool output and qstat output, it appears that stats.py
should be updated to use the 'stats64' structure for accurate
comparisons when packet/byte counters get very large.
To confirm that this was not related to the qstats code I was iterating
on, I booted a kernel without my driver changes and re-ran the test
which shows the qstats are skipped (as they don't exist for mlx5):
NETIF=eth0 tools/testing/selftests/drivers/net/stats.py
KTAP version 1
1..4
ok 1 stats.check_pause
ok 2 stats.check_fec
ok 3 stats.pkt_byte_sum # SKIP qstats not supported by the device
ok 4 stats.qstat_by_ifindex # SKIP No ifindex supports qstats
But, fetching the stats using the CLI
$ ./cli.py --spec ../../../Documentation/netlink/specs/rt_link.yaml \
--do getlink --json '{"ifi-index": 7}'
Shows the same issue (heavily snipped for relevant fields only):
'stats': {
'multicast': 105489,
'rx-bytes': 530879526,
'rx-packets': 751415,
'tx-bytes': 2510191396,
'tx-packets': 27700323,
'stats64': {
'multicast': 105489,
'rx-bytes': 530879526,
'rx-packets': 751415,
'tx-bytes': 15395093284,
'tx-packets': 27700323,
Comparing side by side with ethtool -S on the unmodified mlx5 driver:
tx-bytes stats: 2510191396
tx-bytes stats64: 15395093284
tx-bytes ethtool: 17718435810
Fixes: f0e6c86e4b ("testing: net-drv: add a driver test for stats reporting")
Signed-off-by: Joe Damato <jdamato@fastly.com>
Link: https://lore.kernel.org/r/20240520235850.190041-1-jdamato@fastly.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
145 lines
4.5 KiB
Python
Executable File
145 lines
4.5 KiB
Python
Executable File
#!/usr/bin/env python3
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# SPDX-License-Identifier: GPL-2.0
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from lib.py import ksft_run, ksft_exit, ksft_pr
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from lib.py import ksft_ge, ksft_eq, ksft_in, ksft_true, ksft_raises, KsftSkipEx, KsftXfailEx
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from lib.py import EthtoolFamily, NetdevFamily, RtnlFamily, NlError
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from lib.py import NetDrvEnv
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ethnl = EthtoolFamily()
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netfam = NetdevFamily()
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rtnl = RtnlFamily()
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def check_pause(cfg) -> None:
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global ethnl
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try:
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ethnl.pause_get({"header": {"dev-index": cfg.ifindex}})
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except NlError as e:
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if e.error == 95:
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raise KsftXfailEx("pause not supported by the device")
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raise
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data = ethnl.pause_get({"header": {"dev-index": cfg.ifindex,
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"flags": {'stats'}}})
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ksft_true(data['stats'], "driver does not report stats")
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def check_fec(cfg) -> None:
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global ethnl
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try:
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ethnl.fec_get({"header": {"dev-index": cfg.ifindex}})
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except NlError as e:
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if e.error == 95:
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raise KsftXfailEx("FEC not supported by the device")
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raise
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data = ethnl.fec_get({"header": {"dev-index": cfg.ifindex,
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"flags": {'stats'}}})
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ksft_true(data['stats'], "driver does not report stats")
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def pkt_byte_sum(cfg) -> None:
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global netfam, rtnl
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def get_qstat(test):
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global netfam
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stats = netfam.qstats_get({}, dump=True)
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if stats:
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for qs in stats:
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if qs["ifindex"]== test.ifindex:
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return qs
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qstat = get_qstat(cfg)
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if qstat is None:
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raise KsftSkipEx("qstats not supported by the device")
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for key in ['tx-packets', 'tx-bytes', 'rx-packets', 'rx-bytes']:
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ksft_in(key, qstat, "Drivers should always report basic keys")
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# Compare stats, rtnl stats and qstats must match,
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# but the interface may be up, so do a series of dumps
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# each time the more "recent" stats must be higher or same.
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def stat_cmp(rstat, qstat):
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for key in ['tx-packets', 'tx-bytes', 'rx-packets', 'rx-bytes']:
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if rstat[key] != qstat[key]:
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return rstat[key] - qstat[key]
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return 0
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for _ in range(10):
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rtstat = rtnl.getlink({"ifi-index": cfg.ifindex})['stats64']
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if stat_cmp(rtstat, qstat) < 0:
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raise Exception("RTNL stats are lower, fetched later")
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qstat = get_qstat(cfg)
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if stat_cmp(rtstat, qstat) > 0:
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raise Exception("Qstats are lower, fetched later")
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def qstat_by_ifindex(cfg) -> None:
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global netfam
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global rtnl
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# Construct a map ifindex -> [dump, by-index, dump]
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ifindexes = {}
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stats = netfam.qstats_get({}, dump=True)
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for entry in stats:
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ifindexes[entry['ifindex']] = [entry, None, None]
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for ifindex in ifindexes.keys():
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entry = netfam.qstats_get({"ifindex": ifindex}, dump=True)
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ksft_eq(len(entry), 1)
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ifindexes[entry[0]['ifindex']][1] = entry[0]
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stats = netfam.qstats_get({}, dump=True)
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for entry in stats:
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ifindexes[entry['ifindex']][2] = entry
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if len(ifindexes) == 0:
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raise KsftSkipEx("No ifindex supports qstats")
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# Now make sure the stats match/make sense
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for ifindex, triple in ifindexes.items():
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all_keys = triple[0].keys() | triple[1].keys() | triple[2].keys()
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for key in all_keys:
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ksft_ge(triple[1][key], triple[0][key], comment="bad key: " + key)
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ksft_ge(triple[2][key], triple[1][key], comment="bad key: " + key)
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# Test invalid dumps
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# 0 is invalid
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with ksft_raises(NlError) as cm:
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netfam.qstats_get({"ifindex": 0}, dump=True)
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ksft_eq(cm.exception.nl_msg.error, -34)
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ksft_eq(cm.exception.nl_msg.extack['bad-attr'], '.ifindex')
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# loopback has no stats
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with ksft_raises(NlError) as cm:
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netfam.qstats_get({"ifindex": 1}, dump=True)
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ksft_eq(cm.exception.nl_msg.error, -95)
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ksft_eq(cm.exception.nl_msg.extack['bad-attr'], '.ifindex')
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# Try to get stats for lowest unused ifindex but not 0
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devs = rtnl.getlink({}, dump=True)
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all_ifindexes = set([dev["ifi-index"] for dev in devs])
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lowest = 2
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while lowest in all_ifindexes:
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lowest += 1
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with ksft_raises(NlError) as cm:
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netfam.qstats_get({"ifindex": lowest}, dump=True)
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ksft_eq(cm.exception.nl_msg.error, -19)
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ksft_eq(cm.exception.nl_msg.extack['bad-attr'], '.ifindex')
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def main() -> None:
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with NetDrvEnv(__file__) as cfg:
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ksft_run([check_pause, check_fec, pkt_byte_sum, qstat_by_ifindex],
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args=(cfg, ))
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ksft_exit()
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if __name__ == "__main__":
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main()
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