mptcp: set remote_deny_join_id0 on SYN recv

[ Upstream commit 96939cec994070aa5df852c10fad5fc303a97ea3 ]

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")
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250912-net-mptcp-pm-uspace-deny_join_id0-v1-1-40171884ade8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index cff23281069282114a2746dd50af0ddda0d27168..2ff72b7940fe95b89ee07d61715ff7fb84bb1548 100644 (file)
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -773,6 +773,10 @@ create_child:
                                goto fallback;
 
                        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