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 a05f201d194c52cf158f1cd7ff891ce8dfa282f9..17d1a9d8b0e98bff8d5f19405a2606488e80ae3e 100644 (file)
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -888,6 +888,10 @@ 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