[PATCH mptcp-next v7 5/6] selftests: mptcp: pm_nl_ctl: support the subflow-retries limit

[Anil Kaushik <anilkaushikwireless@gmail.com>]

'pm_nl_ctl limits' can now set the subflow-retries limit with a third
value, and shows it when the kernel supports it.

pm_netlink.sh checks its default value, that a value above the maximum
is refused, and that it can be set. This is only done with pm_nl_ctl
for the moment: iproute2 does not support this limit yet.

Assisted-by: LLM
Signed-off-by: Anil Kaushik <anilkaushikwireless@gmail.com>
---

Notes:
    v7:
     - also check that the maximum value, 127, is accepted (netdev
       Sashiko)
    v5:
     - new (Matthieu)

 .../testing/selftests/net/mptcp/pm_netlink.sh | 47 ++++++++++++++++++-
 tools/testing/selftests/net/mptcp/pm_nl_ctl.c | 34 +++++++++++---
 2 files changed, 72 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/pm_netlink.sh b/tools/testing/selftests/net/mptcp/pm_netlink.sh
index 21bfe1311f11..f06e4f61fa95 100755
--- a/tools/testing/selftests/net/mptcp/pm_netlink.sh
+++ b/tools/testing/selftests/net/mptcp/pm_netlink.sh
@@ -46,15 +46,20 @@ trap cleanup EXIT
 
 mptcp_lib_ns_init ns1
 
+# $3: subflow retries, only shown by pm_nl_ctl, if supported
 format_limits() {
 	local accept="${1}"
 	local subflows="${2}"
+	local retries="${3}"
 
 	if mptcp_lib_is_ip_mptcp; then
 		# with a space at the end
 		printf "add_addr_accepted %d subflows %d \n" "${accept}" "${subflows}"
 	else
 		printf "accept %d\nsubflows %d\n" "${accept}" "${subflows}"
+		if [ -n "${retries}" ]; then
+			printf "subflow_retries %d\n" "${retries}"
+		fi
 	fi
 }
 
@@ -75,6 +80,22 @@ get_limits_nb() {
 	fi
 }
 
+# The subflow retries limit is only set and shown with pm_nl_ctl for now.
+# Prints its default value if it is supported.
+get_default_retries() {
+	if mptcp_lib_is_ip_mptcp; then
+		return
+	fi
+
+	if ip netns exec "${ns1}" ./pm_nl_ctl limits |
+	   grep -q "^subflow_retries"; then
+		echo 15
+	elif mptcp_lib_expect_all_features; then
+		# missing feature: the defaults limits check will fail
+		echo 15
+	fi
+}
+
 format_endpoints() {
 	mptcp_lib_pm_nl_format_endpoints "${@}"
 }
@@ -154,8 +175,10 @@ mptcp_lib_subtests_last_ts_reset
 check "show_endpoints" "" "defaults addr list"
 
 default_limits="$(get_limits)"
+default_retries="$(get_default_retries)"
 if mptcp_lib_expect_all_features; then
-	check "get_limits" "$(format_limits 0 2)" "defaults limits"
+	check "get_limits" "$(format_limits 0 2 "${default_retries}")" \
+		"defaults limits"
 fi
 
 add_endpoint 10.0.1.1
@@ -224,7 +247,27 @@ check "get_limits" "${default_limits}" "subflows above hard limit"
 
 set_limits ${max_limits} ${max_limits}
 flush_endpoint  ## to make sure it doesn't affect the limits
-check "get_limits" "$(format_limits ${max_limits} ${max_limits})" "set limits"
+max_limits_out="$(format_limits ${max_limits} ${max_limits} \
+		 "${default_retries}")"
+check "get_limits" "${max_limits_out}" "set limits"
+
+if [ -n "${default_retries}" ]; then
+	ip netns exec "${ns1}" ./pm_nl_ctl limits ${max_limits} ${max_limits} \
+		128 2>/dev/null
+	check "get_limits" "${max_limits_out}" \
+		"subflow retries above hard limit"
+
+	ip netns exec "${ns1}" ./pm_nl_ctl limits ${max_limits} ${max_limits} 0
+	check "get_limits" "$(format_limits ${max_limits} ${max_limits} 0)" \
+		"set subflow retries"
+
+	ip netns exec "${ns1}" ./pm_nl_ctl limits ${max_limits} ${max_limits} \
+		127
+	check "get_limits" "$(format_limits ${max_limits} ${max_limits} 127)" \
+		"set max subflow retries"
+	ip netns exec "${ns1}" ./pm_nl_ctl limits ${max_limits} ${max_limits} \
+		"${default_retries}"
+fi
 
 flush_endpoint
 add_endpoint 10.0.1.1
diff --git a/tools/testing/selftests/net/mptcp/pm_nl_ctl.c b/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
index 78180da1efcc..41467b997018 100644
--- a/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
+++ b/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
@@ -39,7 +39,7 @@ static void syntax(char *argv[])
 	fprintf(stderr, "\tset [<ip>] [id <nr>] flags [no]backup|[no]fullmesh [port <nr>] [token <token>] [rip <ip>] [rport <port>]\n");
 	fprintf(stderr, "\tflush\n");
 	fprintf(stderr, "\tdump\n");
-	fprintf(stderr, "\tlimits [<rcv addr max> <subflow max>]\n");
+	fprintf(stderr, "\tlimits [<rcv addr max> <subflow max> [<retry>]]\n");
 	fprintf(stderr, "\tevents\n");
 	fprintf(stderr, "\tlisten <local-ip> <local-port>\n");
 	exit(0);
@@ -1217,6 +1217,7 @@ int flush_addrs(int fd, int pm_family, int argc, char *argv[])
 static void print_limits(struct nlmsghdr *nh, int pm_family, int total_len)
 {
 	struct rtattr *attrs;
+	const char *name;
 	uint32_t max;
 
 	for (; NLMSG_OK(nh, total_len); nh = NLMSG_NEXT(nh, total_len)) {
@@ -1235,13 +1236,22 @@ static void print_limits(struct nlmsghdr *nh, int pm_family, int total_len)
 		while (RTA_OK(attrs, len)) {
 			int type = attrs->rta_type;
 
-			if (type != MPTCP_PM_ATTR_RCV_ADD_ADDRS &&
-			    type != MPTCP_PM_ATTR_SUBFLOWS)
+			switch (type) {
+			case MPTCP_PM_ATTR_RCV_ADD_ADDRS:
+				name = "accept";
+				break;
+			case MPTCP_PM_ATTR_SUBFLOWS:
+				name = "subflows";
+				break;
+			case MPTCP_PM_ATTR_SUBFLOW_RETRIES:
+				name = "subflow_retries";
+				break;
+			default:
 				goto next;
+			}
 
 			memcpy(&max, RTA_DATA(attrs), 4);
-			printf("%s %u\n", type == MPTCP_PM_ATTR_SUBFLOWS ?
-					  "subflows" : "accept", max);
+			printf("%s %u\n", name, max);
 
 next:
 			attrs = RTA_NEXT(attrs, len);
@@ -1254,15 +1264,17 @@ int get_set_limits(int fd, int pm_family, int argc, char *argv[])
 	char data[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
 		  NLMSG_ALIGN(sizeof(struct genlmsghdr)) +
 		  1024];
-	uint32_t rcv_addr = 0, subflows = 0;
+	uint32_t rcv_addr = 0, subflows = 0, retries = 0;
 	int cmd, len = sizeof(data);
 	struct nlmsghdr *nh;
 	int off = 0;
 
 	/* limit */
-	if (argc == 4) {
+	if (argc == 4 || argc == 5) {
 		rcv_addr = atoi(argv[2]);
 		subflows = atoi(argv[3]);
+		if (argc == 5)
+			retries = atoi(argv[4]);
 		cmd = MPTCP_PM_CMD_SET_LIMITS;
 	} else {
 		cmd = MPTCP_PM_CMD_GET_LIMITS;
@@ -1287,6 +1299,14 @@ int get_set_limits(int fd, int pm_family, int argc, char *argv[])
 		memcpy(RTA_DATA(rta), &subflows, 4);
 		off += NLMSG_ALIGN(rta->rta_len);
 
+		if (argc == 5) {
+			rta = (void *)(data + off);
+			rta->rta_type = MPTCP_PM_ATTR_SUBFLOW_RETRIES;
+			rta->rta_len = RTA_LENGTH(4);
+			memcpy(RTA_DATA(rta), &retries, 4);
+			off += NLMSG_ALIGN(rta->rta_len);
+		}
+
 		/* do not expect a reply */
 		len = 0;
 	}
-- 
2.25.1