When a SYN containing the 'C' flag (deny join id0) was received, this
piece of information was not propagated to the path-manager.

Even if this flag is mainly set on the server side, a client can also
tell the server it cannot try to establish new subflows to the client's
initial IP address and port. The server's PM should then record such
info when received, and before sending events about the new connection.

Fixes: df377be38725 ("mptcp: add deny_join_id0 in mptcp_options_received")
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/subflow.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index c8a7e4b59db1150610f99d6e599a9d4cf7e137bc..e8325890a32238bd1fd558b955137a2fa32f66c2 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -883,6 +883,10 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 
 			ctx->subflow_id = 1;
 			owner = mptcp_sk(ctx->conn);
+
+			if (mp_opt.deny_join_id0)
+				WRITE_ONCE(owner->pm.remote_deny_join_id0, true);
+
 			mptcp_pm_new_connection(owner, child, 1);
 
 			/* with OoO packets we can reach here without ingress

-- 
2.51.0