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 1802bc5435a1aaabc81e28152b0bac5656e3b828..d77a2e374a7ae888e1ad8f65687f354e35daad19 100644 (file)
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -882,6 +882,10 @@ create_child:
 
                        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