linux-kernel - [PATCH net-next 2/6] mptcp: pm: netlink: announce server-side flag

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Message-Id: <20250919-net-next-mptcp-server-side-flag-v1-2-a97a5d561a8b@kernel.org>
Date: Fri, 19 Sep 2025 14:08:59 +0200
From: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
To: Mat Martineau <martineau@...nel.org>, Geliang Tang <geliang@...nel.org>, 
 Donald Hunter <donald.hunter@...il.com>, Jakub Kicinski <kuba@...nel.org>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
 Shuah Khan <shuah@...nel.org>
Cc: netdev@...r.kernel.org, mptcp@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
Subject: [PATCH net-next 2/6] mptcp: pm: netlink: announce server-side flag

Now that the 'flags' attribute is used, it seems interesting to add one
flag for 'server-side', a boolean value.

This is duplicating the info from the dedicated 'server-side' attribute,
but it will be deprecated in the next commit, and removed in a few
versions.

Reviewed-by: Geliang Tang <geliang@...nel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
---
 include/uapi/linux/mptcp.h |  1 +
 net/mptcp/pm_netlink.c     | 11 +++++++----
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/mptcp.h b/include/uapi/linux/mptcp.h
index 5fd5b4cf75ca1e0099e0effa351507d3ab002f1e..95d621f6d59810126cbc37b1d6baf896a40dd9bc 100644
--- a/include/uapi/linux/mptcp.h
+++ b/include/uapi/linux/mptcp.h
@@ -32,6 +32,7 @@
 #define MPTCP_INFO_FLAG_REMOTE_KEY_RECEIVED	_BITUL(1)

 #define MPTCP_PM_EV_FLAG_DENY_JOIN_ID0		_BITUL(0)
+#define MPTCP_PM_EV_FLAG_SERVER_SIDE		_BITUL(1)

 #define MPTCP_PM_ADDR_FLAG_SIGNAL                      (1 << 0)
 #define MPTCP_PM_ADDR_FLAG_SUBFLOW                     (1 << 1)
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 33a6bf536c020b59717472aca2d38add26255419..aa0c73faaa6acad3fd66ea0942726ecd4d0abcc0 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -413,10 +413,13 @@ static int mptcp_event_created(struct sk_buff *skb,
 	if (err)
 		return err;

-	/* only set when it is the server side */
-	if (READ_ONCE(msk->pm.server_side) &&
-	    nla_put_u8(skb, MPTCP_ATTR_SERVER_SIDE, 1))
-		return -EMSGSIZE;
+	if (READ_ONCE(msk->pm.server_side)) {
+		flags |= MPTCP_PM_EV_FLAG_SERVER_SIDE;
+
+		/* only set when it is the server side */
+		if (nla_put_u8(skb, MPTCP_ATTR_SERVER_SIDE, 1))
+			return -EMSGSIZE;
+	}

 	if (READ_ONCE(msk->pm.remote_deny_join_id0))
 		flags |= MPTCP_PM_EV_FLAG_DENY_JOIN_ID0;

-- 
2.51.0