[PATCH net 0/4] selftests: mptcp: mark unstable subtests as flaky

[PATCH net 0/4] selftests: mptcp: mark unstable subtests as flaky

[Matthieu Baerts (NGI0)]

Some subtests can be unstable, failing once every X runs. Fixing them
can take time: there could be an issue in the kernel or in the subtest,
and it is then important to do a proper analysis, not to hide real bugs.

To avoid creating noises on the different CIs where tests are more
unstable than on our side, some subtests have been marked as flaky. As a
result, errors with these subtests (if any) are ignored.

Note that the MPTCP CI will continue to track these flaky subtests. All
these unstable subtests are also tracked by our bug tracker.

These are fixes for the -net tree, because the instabilities are visible
there. The first patch introducing the flake support has no 'Fixes'
tags, mainly because it requires recent and important refactoring done
in all MPTCP selftests. Backporting that to old versions where the flaky
tests have been introduced would be too difficult, and probably not
worth it. The other patches, adding MPTCP_LIB_SUBTEST_FLAKY=1, have a
Fixes tag, simply to ease the backport of the future fixes removing them
along with the proper fix.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
Matthieu Baerts (NGI0) (4):
      selftests: mptcp: lib: support flaky subtests
      selftests: mptcp: simult flows: mark 'unbalanced' tests as flaky
      selftests: mptcp: join: mark 'fastclose' tests as flaky
      selftests: mptcp: join: mark 'fail' tests as flaky

 tools/testing/selftests/net/mptcp/mptcp_join.sh   | 10 +++++++-
 tools/testing/selftests/net/mptcp/mptcp_lib.sh    | 30 +++++++++++++++++++++--
 tools/testing/selftests/net/mptcp/simult_flows.sh |  6 ++---
 3 files changed, 40 insertions(+), 6 deletions(-)
---
base-commit: 0b4f5add9fa59bfd42c1030f572db2e4c395181b
change-id: 20240524-upstream-net-20240524-selftests-mptcp-flaky-5b6836a59f72

Best regards,
-- 
Matthieu Baerts (NGI0) <matttbe@kernel.org>

[PATCH net 1/4] selftests: mptcp: lib: support flaky subtests

[Matthieu Baerts (NGI0)]

Some subtests can be unstable, failing once every X runs. Fixing them
can take time: there could be an issue in the kernel or in the subtest,
and it is then important to do a proper analysis, not to hide real bugs.

To avoid creating noises on the different CIs, it is important to have a
simple way to mark subtests as flaky, and ignore the errors. This is
what this patch introduces: subtests can be marked as flaky by setting
MPTCP_LIB_SUBTEST_FLAKY env var to 1, e.g.

  MPTCP_LIB_SUBTEST_FLAKY=1 <run flaky subtest>

The subtest will be executed, and errors (if any) will be ignored. It is
still good to run these subtests, as it exercises code, and the results
can still be useful for the on-going investigations.

Note that the MPTCP CI will continue to track these flaky subtests by
setting SELFTESTS_MPTCP_LIB_OVERRIDE_FLAKY env var to 1, and a ticket
has to be created before marking subtests as flaky.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 tools/testing/selftests/net/mptcp/mptcp_lib.sh | 30 ++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_lib.sh b/tools/testing/selftests/net/mptcp/mptcp_lib.sh
index ad2ebda5cb64..6ffa9b7a3260 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_lib.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_lib.sh
@@ -21,6 +21,7 @@ declare -rx MPTCP_LIB_AF_INET6=10
 
 MPTCP_LIB_SUBTESTS=()
 MPTCP_LIB_SUBTESTS_DUPLICATED=0
+MPTCP_LIB_SUBTEST_FLAKY=0
 MPTCP_LIB_TEST_COUNTER=0
 MPTCP_LIB_TEST_FORMAT="%02u %-50s"
 MPTCP_LIB_IP_MPTCP=0
@@ -41,6 +42,16 @@ else
 	readonly MPTCP_LIB_COLOR_RESET=
 fi
 
+# SELFTESTS_MPTCP_LIB_OVERRIDE_FLAKY env var can be set not to ignore errors
+# from subtests marked as flaky
+mptcp_lib_override_flaky() {
+	[ "${SELFTESTS_MPTCP_LIB_OVERRIDE_FLAKY:-}" = 1 ]
+}
+
+mptcp_lib_subtest_is_flaky() {
+	[ "${MPTCP_LIB_SUBTEST_FLAKY}" = 1 ] && ! mptcp_lib_override_flaky
+}
+
 # $1: color, $2: text
 mptcp_lib_print_color() {
 	echo -e "${MPTCP_LIB_START_PRINT:-}${*}${MPTCP_LIB_COLOR_RESET}"
@@ -72,7 +83,16 @@ mptcp_lib_pr_skip() {
 }
 
 mptcp_lib_pr_fail() {
-	mptcp_lib_print_err "[FAIL]${1:+ ${*}}"
+	local title cmt
+
+	if mptcp_lib_subtest_is_flaky; then
+		title="IGNO"
+		cmt=" (flaky)"
+	else
+		title="FAIL"
+	fi
+
+	mptcp_lib_print_err "[${title}]${cmt}${1:+ ${*}}"
 }
 
 mptcp_lib_pr_info() {
@@ -208,7 +228,13 @@ mptcp_lib_result_pass() {
 
 # $1: test name
 mptcp_lib_result_fail() {
-	__mptcp_lib_result_add "not ok" "${1}"
+	if mptcp_lib_subtest_is_flaky; then
+		# It might sound better to use 'not ok # TODO' or 'ok # SKIP',
+		# but some CIs don't understand 'TODO' and treat SKIP as errors.
+		__mptcp_lib_result_add "ok" "${1} # IGNORE Flaky"
+	else
+		__mptcp_lib_result_add "not ok" "${1}"
+	fi
 }
 
 # $1: test name

-- 
2.43.0

[PATCH net 2/4] selftests: mptcp: simult flows: mark 'unbalanced' tests as flaky

[Matthieu Baerts (NGI0)]

These tests are flaky since their introduction. This might be less or
not visible depending on the CI running the tests, especially if it is
also busy doing other tasks in parallel.

A first analysis shown that the transfer can be slowed down when there
are some re-injections at the MPTCP level. Such re-injections can of
course happen, and disturb the transfer, but it looks strange to have
them in this lab. That could be caused by the kernel having access to
less CPU cycles -- e.g. when other activities are executed in parallel
-- or by a misinterpretation on the MPTCP packet scheduler side.

While this is being investigated, the tests are marked as flaky not to
create noises in other CIs.

Fixes: 219d04992b68 ("mptcp: push pending frames when subflow has free space")
Link: https://github.com/multipath-tcp/mptcp_net-next/issues/475
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 tools/testing/selftests/net/mptcp/simult_flows.sh | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/simult_flows.sh b/tools/testing/selftests/net/mptcp/simult_flows.sh
index 4b14b4412166..f74e1c3c126d 100755
--- a/tools/testing/selftests/net/mptcp/simult_flows.sh
+++ b/tools/testing/selftests/net/mptcp/simult_flows.sh
@@ -244,7 +244,7 @@ run_test()
 	do_transfer $small $large $time
 	lret=$?
 	mptcp_lib_result_code "${lret}" "${msg}"
-	if [ $lret -ne 0 ]; then
+	if [ $lret -ne 0 ] && ! mptcp_lib_subtest_is_flaky; then
 		ret=$lret
 		[ $bail -eq 0 ] || exit $ret
 	fi
@@ -254,7 +254,7 @@ run_test()
 	do_transfer $large $small $time
 	lret=$?
 	mptcp_lib_result_code "${lret}" "${msg}"
-	if [ $lret -ne 0 ]; then
+	if [ $lret -ne 0 ] && ! mptcp_lib_subtest_is_flaky; then
 		ret=$lret
 		[ $bail -eq 0 ] || exit $ret
 	fi
@@ -290,7 +290,7 @@ run_test 10 10 0 0 "balanced bwidth"
 run_test 10 10 1 25 "balanced bwidth with unbalanced delay"
 
 # we still need some additional infrastructure to pass the following test-cases
-run_test 10 3 0 0 "unbalanced bwidth"
+MPTCP_LIB_SUBTEST_FLAKY=1 run_test 10 3 0 0 "unbalanced bwidth"
 run_test 10 3 1 25 "unbalanced bwidth with unbalanced delay"
 run_test 10 3 25 1 "unbalanced bwidth with opposed, unbalanced delay"
 

-- 
2.43.0

[PATCH net 3/4] selftests: mptcp: join: mark 'fastclose' tests as flaky

[Matthieu Baerts (NGI0)]

These tests are flaky since their introduction. This might be less or
not visible depending on the CI running the tests, especially if it is
also busy doing other tasks in parallel, and if a debug kernel config is
being used.

It looks like this issue is often present with the NetDev CI. While this
is being investigated, the tests are marked as flaky not to create
noises on such CIs.

Fixes: 01542c9bf9ab ("selftests: mptcp: add fastclose testcase")
Link: https://github.com/multipath-tcp/mptcp_net-next/issues/324
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index fefa9173bdaa..b869b46823d7 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -261,6 +261,8 @@ reset()
 
 	TEST_NAME="${1}"
 
+	MPTCP_LIB_SUBTEST_FLAKY=0 # reset if modified
+
 	if skip_test; then
 		MPTCP_LIB_TEST_COUNTER=$((MPTCP_LIB_TEST_COUNTER+1))
 		last_test_ignored=1
@@ -448,7 +450,9 @@ reset_with_tcp_filter()
 # $1: err msg
 fail_test()
 {
-	ret=${KSFT_FAIL}
+	if ! mptcp_lib_subtest_is_flaky; then
+		ret=${KSFT_FAIL}
+	fi
 
 	if [ ${#} -gt 0 ]; then
 		print_fail "${@}"
@@ -3069,6 +3073,7 @@ fullmesh_tests()
 fastclose_tests()
 {
 	if reset_check_counter "fastclose test" "MPTcpExtMPFastcloseTx"; then
+		MPTCP_LIB_SUBTEST_FLAKY=1
 		test_linkfail=1024 fastclose=client \
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 0 0 0
@@ -3077,6 +3082,7 @@ fastclose_tests()
 	fi
 
 	if reset_check_counter "fastclose server test" "MPTcpExtMPFastcloseRx"; then
+		MPTCP_LIB_SUBTEST_FLAKY=1
 		test_linkfail=1024 fastclose=server \
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 0 0 0 0 0 0 1

-- 
2.43.0

[PATCH net 4/4] selftests: mptcp: join: mark 'fail' tests as flaky

[Matthieu Baerts (NGI0)]

These tests are rarely unstable. It depends on the CI running the tests,
especially if it is also busy doing other tasks in parallel, and if a
debug kernel config is being used.

It looks like this issue is sometimes present with the NetDev CI. While
this is being investigated, the tests are marked as flaky not to create
noises on such CIs.

Fixes: b6e074e171bc ("selftests: mptcp: add infinite map testcase")
Link: https://github.com/multipath-tcp/mptcp_net-next/issues/491
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index b869b46823d7..2b66c5fa71eb 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -3101,6 +3101,7 @@ fail_tests()
 {
 	# single subflow
 	if reset_with_fail "Infinite map" 1; then
+		MPTCP_LIB_SUBTEST_FLAKY=1
 		test_linkfail=128 \
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 0 0 0 +1 +0 1 0 1 "$(pedit_action_pkts)"
@@ -3109,6 +3110,7 @@ fail_tests()
 
 	# multiple subflows
 	if reset_with_fail "MP_FAIL MP_RST" 2; then
+		MPTCP_LIB_SUBTEST_FLAKY=1
 		tc -n $ns2 qdisc add dev ns2eth1 root netem rate 1mbit delay 5ms
 		pm_nl_set_limits $ns1 0 1
 		pm_nl_set_limits $ns2 0 1

-- 
2.43.0

Re: [PATCH net 0/4] selftests: mptcp: mark unstable subtests as flaky

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri, 24 May 2024 18:30:55 +0200 you wrote:
> Some subtests can be unstable, failing once every X runs. Fixing them
> can take time: there could be an issue in the kernel or in the subtest,
> and it is then important to do a proper analysis, not to hide real bugs.
> 
> To avoid creating noises on the different CIs where tests are more
> unstable than on our side, some subtests have been marked as flaky. As a
> result, errors with these subtests (if any) are ignored.
> 
> [...]

Here is the summary with links:
  - [net,1/4] selftests: mptcp: lib: support flaky subtests
    https://git.kernel.org/netdev/net/c/5597613fb3cf
  - [net,2/4] selftests: mptcp: simult flows: mark 'unbalanced' tests as flaky
    https://git.kernel.org/netdev/net/c/cc73a6577ae6
  - [net,3/4] selftests: mptcp: join: mark 'fastclose' tests as flaky
    https://git.kernel.org/netdev/net/c/8c06ac2178a9
  - [net,4/4] selftests: mptcp: join: mark 'fail' tests as flaky
    https://git.kernel.org/netdev/net/c/38af56e6668b

You are awesome, thank you!
-- 
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