netdev - [PATCH iproute2] mptcp: add new listener events

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Message-Id: <20230110-mptcp-events-listener-net-v1-1-88a946722fe7@tessares.net>
Date:   Tue, 10 Jan 2023 16:36:20 +0100
From:   Matthieu Baerts <matthieu.baerts@...sares.net>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org, mptcp@...ts.linux.dev,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        Geliang Tang <geliang.tang@...e.com>
Subject: [PATCH iproute2] mptcp: add new listener events

These new events have been added in kernel commit f8c9dfbd875b ("mptcp:
add pm listener events") by Geliang Tang.

Two new MPTCP Netlink event types for PM listening socket creation and
closure have been recently added. They will be available in the future
v6.2 kernel.

They have been added because MPTCP for Linux, when not using the
in-kernel PM, depends on the userspace PM to create extra listening
sockets -- called "PM listeners" -- before announcing addresses and
ports. With the existing MPTCP Netlink events, a userspace PM can create
PM listeners at startup time, or in response to an incoming connection.
Creating sockets in response to connections is not optimal: ADD_ADDRs
can't be sent until the sockets are created and listen()ed, and if all
connections are closed then it may not be clear to the userspace PM
daemon that PM listener sockets should be cleaned up. Hence these new
events: PM listening sockets can be managed based on application
activity.

Note that the maximum event string size has to be increased by 2 to be
able to display LISTENER_CREATED without truncated it.

Also, as pointed by Mat, this event doesn't have any "token" attribute
so this attribute is now printed only if it is available.

Link: https://github.com/multipath-tcp/mptcp_net-next/issues/313
Cc: Geliang Tang <geliang.tang@...e.com>
Acked-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
Signed-off-by: Matthieu Baerts <matthieu.baerts@...sares.net>
---
 ip/ipmptcp.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/ip/ipmptcp.c b/ip/ipmptcp.c
index ce62ab9a..beba7a41 100644
--- a/ip/ipmptcp.c
+++ b/ip/ipmptcp.c
@@ -454,6 +454,8 @@ static const char * const event_to_str[] = {
 	[MPTCP_EVENT_SUB_ESTABLISHED] = "SF_ESTABLISHED",
 	[MPTCP_EVENT_SUB_CLOSED] = "SF_CLOSED",
 	[MPTCP_EVENT_SUB_PRIORITY] = "SF_PRIO",
+	[MPTCP_EVENT_LISTENER_CREATED] = "LISTENER_CREATED",
+	[MPTCP_EVENT_LISTENER_CLOSED] = "LISTENER_CLOSED",
 };

 static void print_addr(const char *key, int af, struct rtattr *value)
@@ -492,11 +494,12 @@ static int mptcp_monitor_msg(struct rtnl_ctrl_data *ctrl,
 		goto out;
 	}

-	printf("[%14s]", event_to_str[ghdr->cmd]);
+	printf("[%16s]", event_to_str[ghdr->cmd]);

 	parse_rtattr(tb, MPTCP_ATTR_MAX, (void *) ghdr + GENL_HDRLEN, len);

-	printf(" token=%08x", rta_getattr_u32(tb[MPTCP_ATTR_TOKEN]));
+	if (tb[MPTCP_ATTR_TOKEN])
+		printf(" token=%08x", rta_getattr_u32(tb[MPTCP_ATTR_TOKEN]));

 	if (tb[MPTCP_ATTR_REM_ID])
 		printf(" remid=%u", rta_getattr_u8(tb[MPTCP_ATTR_REM_ID]));

---
base-commit: 1ba8021057acde2ea06f5b52c370f7cc86fb2b3e
change-id: 20230110-mptcp-events-listener-net-9cbe043ecd09

Best regards,
-- 
Matthieu Baerts <matthieu.baerts@...sares.net>