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selftests: tc-testing: add a lateral-drift hfsc classify-walk test

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The classify-loop fix bounds a walk's non-descending hops, so the guard
must not misfire on a legal walk that reaches its leaf through a
level-drift lateral chain. Add a case that builds exactly that chain and
asserts traffic still reaches the chain's own leaf.

A lateral hop can only exist because a bind was legal when it was made
and a later class add raised the target's level, so the setup binds each
hop while the target is still a leaf and only then deepens it: bind
1:1 -> 1:2 while 1:2 is a leaf, add 1:20 under 1:2, add 1:3 and bind
1:2 -> 1:3 while 1:3 is a leaf, then add 1:30 and 1:31 under 1:3 and
bind 1:3 -> 1:31. The walk root -> 1:1 -> 1:2 -> 1:3 -> 1:31 then takes
two lateral hops and must reach leaf 1:31.

The default class is 1:30, distinct from the asserted leaf, and the
verify pattern is anchored to the 1:31 stats line, so neither a
fall-through to the default nor a nonzero count on another class can
satisfy the check. On the patched kernel the test passes; with the bound
forced to zero the walk falls to the default and 1:31 stays idle, so the
test fails.

Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Tested-by: hybris <hybris@mojatatu.ai>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://patch.msgid.link/QDISC-CTUU.v3.20260916184908@mojatatu.com.2
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jamal Hadi Salim 2026-09-17 06:57:33 -04:00 committed by Jakub Kicinski
parent 8a60ade227
commit 1e24c4f2ee
1 changed files with 34 additions and 0 deletions
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34
tools/testing/selftests/tc-testing/tc-tests/qdiscs/hfsc.json
View File

@ -169,5 +169,39 @@
"teardown": [
"$TC qdisc del dev $DUMMY handle 1: root"
]
},
{
"id": "8c39",
"name": "HFSC classify walk still reaches leaf after lateral drift",
"category": [
"qdisc",
"hfsc"
],
"plugins": {
"requires": "nsPlugin"
},
"setup": [
"ip link set lo up",
"$TC qdisc add dev lo handle 1: root hfsc default 30",
"$TC class add dev lo parent 1: classid 1:1 hfsc rt m2 100kbit",
"$TC class add dev lo parent 1:1 classid 1:10 hfsc rt m2 50kbit",
"$TC class add dev lo parent 1: classid 1:2 hfsc rt m2 100kbit",
"$TC filter add dev lo parent 1: protocol ip prio 1 u32 match u8 0 0 at 0 flowid 1:1",
"$TC filter add dev lo parent 1:1 protocol ip prio 1 u32 match u8 0 0 at 0 flowid 1:2",
"$TC class add dev lo parent 1:2 classid 1:20 hfsc rt m2 10kbit",
"$TC class add dev lo parent 1: classid 1:3 hfsc rt m2 100kbit",
"$TC filter add dev lo parent 1:2 protocol ip prio 1 u32 match u8 0 0 at 0 flowid 1:3",
"$TC class add dev lo parent 1:3 classid 1:30 hfsc rt m2 10kbit",
"$TC class add dev lo parent 1:3 classid 1:31 hfsc rt m2 100kbit",
"$TC filter add dev lo parent 1:3 protocol ip prio 1 u32 match u8 0 0 at 0 flowid 1:31"
],
"cmdUnderTest": "ping -n -c 10 -W 1 127.0.0.1",
"expExitCode": "0",
"verifyCmd": "$TC -s class show dev lo",
"matchPattern": "class hfsc 1:31 parent 1:3 rt[^\\n]*\\n Sent [0-9]+ bytes [1-9][0-9]* pkt",
"matchCount": "1",
"teardown": [
"$TC qdisc del dev lo handle 1: root"
]
}
]