Subject: Re: [PATCH v3 net-next 09/10] selftests/tc-testing: test that taprio can only be attached as root

From: Vinicius Costa Gomes <[email-masked]>
Date: Wed, 02 Aug 2023 16:29:55 -0700

Vladimir Oltean <[email-masked]> writes:

> Check that the "Can only be attached as root qdisc" error message from
> taprio is effective by attempting to attach it to a class of another
> taprio qdisc. That operation should fail.
>
> In the bug that was squashed by change "net/sched: taprio: try again to
> report q->qdiscs[] to qdisc_leaf()", grafting a child taprio to a root
> software taprio would be misinterpreted as a change() to the root
> taprio. Catch this by looking at whether the base-time of the root
> taprio has changed to follow the base-time of the child taprio,
> something which should have absolutely never happened assuming correct
> semantics.
>

This test is somehow flaky (all others are fine), 1 in ~4 times, it fails.

Taking a look at the test I couldn't quickly find out the reason for the
flakyness.

Here's the verbose output of one of the failures:

vcgomes@otc-cfl-clr-30 ~/src/net-next/tools/testing/selftests/tc-testing $ sudo ./tdc.py -e 39b4 -v
 -- ns/SubPlugin.__init__
ns/SubPlugin.adjust_command
adjust_command:  return command [/sbin/ip link add v0p0 type veth peer name v0p1]
_exec_cmd:  command "/sbin/ip link add v0p0 type veth peer name v0p1"
ns/SubPlugin.adjust_command
adjust_command:  return command [/sbin/ip link set v0p0 up]
_exec_cmd:  command "/sbin/ip link set v0p0 up"
ns/SubPlugin.adjust_command
adjust_command:  return command [/sbin/ip netns add tcut]
_exec_cmd:  command "/sbin/ip netns add tcut"
ns/SubPlugin.adjust_command
adjust_command:  return command [/sbin/ip link set v0p1 netns tcut]
_exec_cmd:  command "/sbin/ip link set v0p1 netns tcut"
ns/SubPlugin.adjust_command
adjust_command:  return command [/sbin/ip -n tcut link set v0p1 up]
_exec_cmd:  command "/sbin/ip -n tcut link set v0p1 up"
	====================
=====> Test 39b4: Reject grafting taprio as child qdisc of software taprio
-----> prepare stage
ns/SubPlugin.adjust_command
adjust_command:  stage is setup; inserting netns stuff in command [echo "1 1 8" > /sys/bus/netdevsim/new_device] list [['echo', '"1', '1', '8"', '>', '/sys/bus/netdevsim/new_device']]
adjust_command:  return command [/sbin/ip netns exec tcut echo "1 1 8" > /sys/bus/netdevsim/new_device]
command "/sbin/ip netns exec tcut echo "1 1 8" > /sys/bus/netdevsim/new_device"
ns/SubPlugin.adjust_command
adjust_command:  stage is setup; inserting netns stuff in command [/sbin/tc qdisc replace dev eth0 handle 8001: parent root stab overhead 24 taprio num_tc 8 map 0 1 2 3 4 5 6 7 queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 base-time 0 sched-entry S ff 20000000 clockid CLOCK_TAI] list [['/sbin/tc', 'qdisc', 'replace', 'dev', 'eth0', 'handle', '8001:', 'parent', 'root', 'stab', 'overhead', '24', 'taprio', 'num_tc', '8', 'map', '0', '1', '2', '3', '4', '5', '6', '7', 'queues', '1@0', '1@1', '1@2', '1@3', '1@4', '1@5', '1@6', '1@7', 'base-time', '0', 'sched-entry', 'S', 'ff', '20000000', 'clockid', 'CLOCK_TAI']]
adjust_command:  return command [/sbin/ip netns exec tcut /sbin/tc qdisc replace dev eth0 handle 8001: parent root stab overhead 24 taprio num_tc 8 map 0 1 2 3 4 5 6 7 queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 base-time 0 sched-entry S ff 20000000 clockid CLOCK_TAI]
command "/sbin/ip netns exec tcut /sbin/tc qdisc replace dev eth0 handle 8001: parent root stab overhead 24 taprio num_tc 8 map 0 1 2 3 4 5 6 7 queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 base-time 0 sched-entry S ff 20000000 clockid CLOCK_TAI"
-----> execute stage
ns/SubPlugin.adjust_command
adjust_command:  stage is execute; inserting netns stuff in command [/sbin/tc qdisc replace dev eth0 parent 8001:7 taprio num_tc 8 map 0 1 2 3 4 5 6 7 queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 base-time 200 sched-entry S ff 20000000 clockid CLOCK_TAI] list [['/sbin/tc', 'qdisc', 'replace', 'dev', 'eth0', 'parent', '8001:7', 'taprio', 'num_tc', '8', 'map', '0', '1', '2', '3', '4', '5', '6', '7', 'queues', '1@0', '1@1', '1@2', '1@3', '1@4', '1@5', '1@6', '1@7', 'base-time', '200', 'sched-entry', 'S', 'ff', '20000000', 'clockid', 'CLOCK_TAI']]
adjust_command:  return command [/sbin/ip netns exec tcut /sbin/tc qdisc replace dev eth0 parent 8001:7 taprio num_tc 8 map 0 1 2 3 4 5 6 7 queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 base-time 200 sched-entry S ff 20000000 clockid CLOCK_TAI]
command "/sbin/ip netns exec tcut /sbin/tc qdisc replace dev eth0 parent 8001:7 taprio num_tc 8 map 0 1 2 3 4 5 6 7 queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 base-time 200 sched-entry S ff 20000000 clockid CLOCK_TAI"
-----> verify stage
ns/SubPlugin.adjust_command
adjust_command:  stage is verify; inserting netns stuff in command [/sbin/tc -j qdisc show dev eth0 root | jq '.[].options.base_time'] list [['/sbin/tc', '-j', 'qdisc', 'show', 'dev', 'eth0', 'root', '|', 'jq', "'.[].options.base_time'"]]
adjust_command:  return command [/sbin/ip netns exec tcut /sbin/tc -j qdisc show dev eth0 root | jq '.[].options.base_time']
command "/sbin/ip netns exec tcut /sbin/tc -j qdisc show dev eth0 root | jq '.[].options.base_time'"
-----> teardown stage
ns/SubPlugin.adjust_command
adjust_command:  stage is teardown; inserting netns stuff in command [/sbin/tc qdisc del dev eth0 root] list [['/sbin/tc', 'qdisc', 'del', 'dev', 'eth0', 'root']]
adjust_command:  return command [/sbin/ip netns exec tcut /sbin/tc qdisc del dev eth0 root]
command "/sbin/ip netns exec tcut /sbin/tc qdisc del dev eth0 root"
ns/SubPlugin.adjust_command
adjust_command:  stage is teardown; inserting netns stuff in command [echo "1" > /sys/bus/netdevsim/del_device] list [['echo', '"1"', '>', '/sys/bus/netdevsim/del_device']]
adjust_command:  return command [/sbin/ip netns exec tcut echo "1" > /sys/bus/netdevsim/del_device]
command "/sbin/ip netns exec tcut echo "1" > /sys/bus/netdevsim/del_device"
ns/SubPlugin.post_suite
ns/SubPlugin.adjust_command
adjust_command:  return command [/sbin/ip netns delete tcut]
_exec_cmd:  command "/sbin/ip netns delete tcut"

All test results:

1..1
not ok 1 39b4 - Reject grafting taprio as child qdisc of software taprio
	Could not match regex pattern. Verify command output:
parse error: Objects must consist of key:value pairs at line 1, column 334

Cheers,
-- 
Vinicius