Recently, some mib counters about fallback has been added, this patch
provides a method to check the expected behavior of these mib counters
during the test execution.

Link: https://github.com/multipath-tcp/mptcp_net-next/issues/571
Signed-off-by: Gang Yan <yangang@kylinos.cn>
------
Changelog:
  v4:
    - Modify the 'MD5_SIG' to 'md5_sig'.
    - Fix the warnings of shellcheck caused by 'rc={?}', it should be
      'rc=$?'
  v3:
    - Squash into a single patch.
    - Using 'fb_' as a prefix instead of the suffix for variables.
    - Adjust the order of mib counters to check, ensuring it matches the
      variable declaration.
    - The namespace('ns1'/'ns2') is included in the output of
      'chk_fallback_nr', like:
      "ns2 infinite map tx fallback        [IGNO] (flaky) got 1 infinite map tx fallback[s] in ns2 expected 0"
    - Add a new helper named 'chk_fallback_nr_all', which prints only
      when an error occurs.
    - Fix some code style issues.

  v2:
    - add a helper which can check all the fallback mib counters.
    - put the 'chk_fallback_nr' in 'chk_join_nr' like chk_join_tx_nr.
---
 .../testing/selftests/net/mptcp/mptcp_join.sh | 123 ++++++++++++++++++
 1 file changed, 123 insertions(+)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index b8af65373b3a..12b27c6e6566 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -74,6 +74,17 @@ unset join_create_err
 unset join_bind_err
 unset join_connect_err
 
+unset fb_ns1
+unset fb_ns2
+unset fb_infinite_map_tx
+unset fb_dss_corruption
+unset fb_simult_conn
+unset fb_mpc_passive
+unset fb_mpc_active
+unset fb_mpc_data
+unset fb_md5_sig
+unset fb_dss
+
 # generated using "nfbpf_compile '(ip && (ip[54] & 0xf0) == 0x30) ||
 #				  (ip6 && (ip6[74] & 0xf0) == 0x30)'"
 CBPF_MPTCP_SUBOPTION_ADD_ADDR="14,
@@ -1399,6 +1410,115 @@ chk_join_tx_nr()
 	print_results "join Tx" ${rc}
 }
 
+chk_fallback_nr()
+{
+	local infinite_map_tx=${fb_infinite_map_tx:-0}
+	local dss_corruption=${fb_dss_corruption:-0}
+	local simult_conn=${fb_simult_conn:-0}
+	local mpc_passive=${fb_mpc_passive:-0}
+	local mpc_active=${fb_mpc_active:-0}
+	local mpc_data=${fb_mpc_data:-0}
+	local md5_sig=${fb_md5_sig:-0}
+	local dss=${fb_dss:-0}
+	local rc=${KSFT_PASS}
+	local ns=$1
+	local count
+
+	count=$(mptcp_lib_get_counter ${!ns} "MPTcpExtInfiniteMapTx")
+	if [ -z "$count" ]; then
+		rc=${KSFT_SKIP}
+	elif [ "$count" != "$infinite_map_tx" ]; then
+		rc=${KSFT_FAIL}
+		print_check "$ns infinite map tx fallback"
+		fail_test "got $count infinite map tx fallback[s] in $ns expected $infinite_map_tx"
+	fi
+
+	count=$(mptcp_lib_get_counter ${!ns} "MPTcpExtDSSCorruptionFallback")
+	if [ -z "$count" ]; then
+		rc=${KSFT_SKIP}
+	elif [ "$count" != "$dss_corruption" ]; then
+		rc=${KSFT_FAIL}
+		print_check "$ns dss corruption fallback"
+		fail_test "got $count dss corruption fallback[s] in $ns expected $dss_corruption"
+	fi
+
+	count=$(mptcp_lib_get_counter ${!ns} "MPTcpExtSimultConnectFallback")
+	if [ -z "$count" ]; then
+		rc=${KSFT_SKIP}
+	elif [ "$count" != "$simult_conn" ]; then
+		rc=${KSFT_FAIL}
+		print_check "$ns simult conn fallback"
+		fail_test "got $count simult conn fallback[s] in $ns expected $simult_conn"
+	fi
+
+	count=$(mptcp_lib_get_counter ${!ns} "MPTcpExtMPCapableFallbackACK")
+	if [ -z "$count" ]; then
+		rc=${KSFT_SKIP}
+	elif [ "$count" != "$mpc_passive" ]; then
+		rc=${KSFT_FAIL}
+		print_check "$ns mpc passive fallback"
+		fail_test "got $count mpc passive fallback[s] in $ns expected $mpc_passive"
+	fi
+
+	count=$(mptcp_lib_get_counter ${!ns} "MPTcpExtMPCapableFallbackSYNACK")
+	if [ -z "$count" ]; then
+		rc=${KSFT_SKIP}
+	elif [ "$count" != "$mpc_active" ]; then
+		rc=${KSFT_FAIL}
+		print_check "$ns mpc active fallback"
+		fail_test "got $count mpc active fallback[s] in $ns expected $mpc_active"
+	fi
+
+	count=$(mptcp_lib_get_counter ${!ns} "MPTcpExtMPCapableDataFallback")
+	if [ -z "$count" ]; then
+		rc=${KSFT_SKIP}
+	elif [ "$count" != "$mpc_data" ]; then
+		rc=${KSFT_FAIL}
+		print_check "$ns mpc data fallback"
+		fail_test "got $count mpc data fallback[s] in $ns expected $mpc_data"
+	fi
+
+	count=$(mptcp_lib_get_counter ${!ns} "MPTcpExtMD5SigFallback")
+	if [ -z "$count" ]; then
+		rc=${KSFT_SKIP}
+	elif [ "$count" != "$md5_sig" ]; then
+		rc=${KSFT_FAIL}
+		print_check "$ns MD5 Sig fallback"
+		fail_test "got $count MD5 Sig fallback[s] in $ns expected $md5_sig"
+	fi
+
+	count=$(mptcp_lib_get_counter ${!ns} "MPTcpExtDssFallback")
+	if [ -z "$count" ]; then
+		rc=${KSFT_SKIP}
+	elif [ "$count" != "$dss" ]; then
+		rc=${KSFT_FAIL}
+		print_check "$ns dss fallback"
+		fail_test "got $count dss fallback[s] in $ns expected $dss"
+	fi
+
+	return $rc
+}
+
+chk_fallback_nr_all()
+{
+	local netns=("ns1" "ns2")
+	local fb_ns=("fb_ns1" "fb_ns2")
+	local rc=${KSFT_PASS}
+
+	for i in 0 1; do
+		if [ -n "${!fb_ns[i]}" ]; then
+			eval "${!fb_ns[i]}" \
+				chk_fallback_nr ${netns[i]} || rc=$?
+		else
+			chk_fallback_nr ${netns[i]} || rc=$?
+		fi
+	done
+
+	if [ "$rc" != "${KSFT_PASS}" ]; then
+		print_results "fallback" $rc
+	fi
+}
+
 chk_join_nr()
 {
 	local syn_nr=$1
@@ -1484,6 +1604,8 @@ chk_join_nr()
 	join_syn_tx="${join_syn_tx:-${syn_nr}}" \
 		chk_join_tx_nr
 
+	chk_fallback_nr_all
+
 	if $validate_checksum; then
 		chk_csum_nr $csum_ns1 $csum_ns2
 		chk_fail_nr $fail_nr $fail_nr
@@ -3337,6 +3459,7 @@ fail_tests()
 		join_csum_ns1=+1 join_csum_ns2=+0 \
 			join_fail_nr=1 join_rst_nr=0 join_infi_nr=1 \
 			join_corrupted_pkts="$(pedit_action_pkts)" \
+			fb_ns1="fb_dss=1" fb_ns2="fb_infinite_map_tx=1" \
 			chk_join_nr 0 0 0
 		chk_fail_nr 1 -1 invert
 	fi
-- 
2.43.0

Hi Gang,

On 16/08/2025 09:18, Gang Yan wrote:
> Recently, some mib counters about fallback has been added, this patch
> provides a method to check the expected behavior of these mib counters
> during the test execution.
> 
> Link: https://github.com/multipath-tcp/mptcp_net-next/issues/571
> Signed-off-by: Gang Yan <yangang@kylinos.cn>
> ------

Note: there should be only 3 dashes ("---") to be considered as a comment.

> Changelog:
>   v4:
>     - Modify the 'MD5_SIG' to 'md5_sig'.
>     - Fix the warnings of shellcheck caused by 'rc={?}', it should be
>       'rc=$?'

Thank you for the new version!

Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>

Now in our tree (I removed the extra 'net' prefix we don't usually add,
and used the "Closes" tag):

New patches for t/upstream:
- 8ac83ce766d6: selftests: mptcp: add checks for fallback counters
- Results: de0b36f41cae..27427f653031 (export)

Tests are now in progress:

- export:
https://github.com/multipath-tcp/mptcp_net-next/commit/9dc9ed97e819c1c4910cae46098ab65f0eb3e20e/checks

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.

Hi Gang,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal: Success! ✅
- KVM Validation: debug: Unstable: 1 failed test(s): selftest_mptcp_connect 🔴
- KVM Validation: btf-normal (only bpftest_all): Success! ✅
- KVM Validation: btf-debug (only bpftest_all): Success! ✅
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/17005894805

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/758610f062af
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=992117


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)