Here are a few sub-tests for mptcp_join.sh, validating the new 'laminar'
endpoint type.

In a setup where subflows created using the routing rules would be
rejected by the listener, and where the latter announces one IP address,
some cases are verified:

- Without any 'laminar' endpoints: no new subflows are created.

- With one 'laminar' endpoint: a second subflow is created.

- With multiple 'laminar' endpoints: 2 IPv4 subflows are created.

- With one 'laminar' endpoint, but the server announcing a second IP
  address, only one subflow is created.

- With one 'laminar' + 'subflow' endpoint, the same endpoint is only
  used once.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 69 +++++++++++++++++++++++++
 tools/testing/selftests/net/mptcp/pm_nl_ctl.c   |  9 ++++
 2 files changed, 78 insertions(+)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index a94b3960ad5e009dbead66b6ff2aa01f70aa3e1f..c90d8e8b95cbb6ba80f79208d1cc844673f2c249 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -2320,6 +2320,74 @@ signal_address_tests()
 	fi
 }
 
+laminar_endp_tests()
+{
+	# no laminar endpoints: routing rules are used
+	if reset_with_tcp_filter "without a laminar endpoint" ns1 10.0.2.2 REJECT &&
+	   mptcp_lib_kallsyms_has "mptcp_pm_get_endp_laminar_max$"; then
+		pm_nl_set_limits $ns1 0 2
+		pm_nl_set_limits $ns2 2 2
+		pm_nl_add_endpoint $ns1 10.0.2.1 flags signal
+		run_tests $ns1 $ns2 10.0.1.1
+		join_syn_tx=1 \
+			chk_join_nr 0 0 0
+		chk_add_nr 1 1
+	fi
+
+	# laminar endpoints: this endpoint is used
+	if reset_with_tcp_filter "with a laminar endpoint" ns1 10.0.2.2 REJECT &&
+	   mptcp_lib_kallsyms_has "mptcp_pm_get_endp_laminar_max$"; then
+		pm_nl_set_limits $ns1 0 2
+		pm_nl_set_limits $ns2 2 2
+		pm_nl_add_endpoint $ns1 10.0.2.1 flags signal
+		pm_nl_add_endpoint $ns2 10.0.3.2 flags laminar
+		run_tests $ns1 $ns2 10.0.1.1
+		chk_join_nr 1 1 1
+		chk_add_nr 1 1
+	fi
+
+	# laminar endpoints: these endpoints are used
+	if reset_with_tcp_filter "with multiple laminar endpoints" ns1 10.0.2.2 REJECT &&
+	   mptcp_lib_kallsyms_has "mptcp_pm_get_endp_laminar_max$"; then
+		pm_nl_set_limits $ns1 0 2
+		pm_nl_set_limits $ns2 2 2
+		pm_nl_add_endpoint $ns1 10.0.2.1 flags signal
+		pm_nl_add_endpoint $ns1 10.0.3.1 flags signal
+		pm_nl_add_endpoint $ns2 dead:beef:3::2 flags laminar
+		pm_nl_add_endpoint $ns2 10.0.3.2 flags laminar
+		pm_nl_add_endpoint $ns2 10.0.4.2 flags laminar
+		run_tests $ns1 $ns2 10.0.1.1
+		chk_join_nr 2 2 2
+		chk_add_nr 2 2
+	fi
+
+	# laminar endpoints: only one endpoint is used
+	if reset_with_tcp_filter "single laminar endpoint" ns1 10.0.2.2 REJECT &&
+	   mptcp_lib_kallsyms_has "mptcp_pm_get_endp_laminar_max$"; then
+		pm_nl_set_limits $ns1 0 2
+		pm_nl_set_limits $ns2 2 2
+		pm_nl_add_endpoint $ns1 10.0.2.1 flags signal
+		pm_nl_add_endpoint $ns1 10.0.3.1 flags signal
+		pm_nl_add_endpoint $ns2 10.0.3.2 flags laminar
+		run_tests $ns1 $ns2 10.0.1.1
+		chk_join_nr 1 1 1
+		chk_add_nr 2 2
+	fi
+
+	# laminar endpoints: subflow and laminar flags
+	if reset_with_tcp_filter "sublow + laminar endpoints" ns1 10.0.2.2 REJECT &&
+	   mptcp_lib_kallsyms_has "mptcp_pm_get_endp_laminar_max$"; then
+		pm_nl_set_limits $ns1 0 4
+		pm_nl_set_limits $ns2 2 4
+		pm_nl_add_endpoint $ns1 10.0.2.1 flags signal
+		pm_nl_add_endpoint $ns2 10.0.1.2 flags subflow,laminar
+		pm_nl_add_endpoint $ns2 10.0.3.2 flags subflow,laminar
+		run_tests $ns1 $ns2 10.0.1.1
+		chk_join_nr 1 1 1
+		chk_add_nr 1 1
+	fi
+}
+
 link_failure_tests()
 {
 	# accept and use add_addr with additional subflows and link loss
@@ -4109,6 +4177,7 @@ all_tests_sorted=(
 	f@subflows_tests
 	e@subflows_error_tests
 	s@signal_address_tests
+	L@laminar_endp_tests
 	l@link_failure_tests
 	t@add_addr_timeout_tests
 	r@remove_tests
diff --git a/tools/testing/selftests/net/mptcp/pm_nl_ctl.c b/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
index d4981b76693bbddca74169437a540ad6294cf1d5..65b374232ff5ac06876dcd621fd2109c4d82cd12 100644
--- a/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
+++ b/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
@@ -830,6 +830,8 @@ int add_addr(int fd, int pm_family, int argc, char *argv[])
 					flags |= MPTCP_PM_ADDR_FLAG_SUBFLOW;
 				else if (!strcmp(tok, "signal"))
 					flags |= MPTCP_PM_ADDR_FLAG_SIGNAL;
+				else if (!strcmp(tok, "laminar"))
+					flags |= MPTCP_PM_ADDR_FLAG_LAMINAR;
 				else if (!strcmp(tok, "backup"))
 					flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
 				else if (!strcmp(tok, "fullmesh"))
@@ -1018,6 +1020,13 @@ static void print_addr(struct rtattr *attrs, int len)
 					printf(",");
 			}
 
+			if (flags & MPTCP_PM_ADDR_FLAG_LAMINAR) {
+				printf("laminar");
+				flags &= ~MPTCP_PM_ADDR_FLAG_LAMINAR;
+				if (flags)
+					printf(",");
+			}
+
 			if (flags & MPTCP_PM_ADDR_FLAG_BACKUP) {
 				printf("backup");
 				flags &= ~MPTCP_PM_ADDR_FLAG_BACKUP;

-- 
2.51.0