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mptcp: grafting MPJ subflow earlier

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Later patches need to ensure that all MPJ subflows are grafted to the
msk socket before accept() completion.

Currently the grafting happens under the msk socket lock: potentially
at msk release_cb time which make satisfying the above condition a bit
tricky.

Move the MPJ subflow grafting earlier, under the msk data lock, so that
we can use such lock as a synchronization point.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20251121-net-next-mptcp-memcg-backlog-imp-v1-3-1f34b6c1e0b1@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Paolo Abeni
2025-11-21 18:02:02 +01:00
committed by Jakub Kicinski
parent bd92dd8e03
commit e777a7fb06
1 changed files with 23 additions and 7 deletions
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30
net/mptcp/protocol.c
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@@ -895,12 +895,6 @@ static bool __mptcp_finish_join(struct mptcp_sock *msk, struct sock *ssk)
mptcp_subflow_joined(msk, ssk);
spin_unlock_bh(&msk->fallback_lock);
/* attach to msk socket only after we are sure we will deal with it
* at close time
*/
if (sk->sk_socket && !ssk->sk_socket)
mptcp_sock_graft(ssk, sk->sk_socket);
mptcp_subflow_ctx(ssk)->subflow_id = msk->subflow_id++;
mptcp_sockopt_sync_locked(msk, ssk);
mptcp_stop_tout_timer(sk);
@@ -3647,6 +3641,20 @@ void mptcp_sock_graft(struct sock *sk, struct socket *parent)
write_unlock_bh(&sk->sk_callback_lock);
}
/* Can be called without holding the msk socket lock; use the callback lock
* to avoid {READ_,WRITE_}ONCE annotations on sk_socket.
*/
static void mptcp_sock_check_graft(struct sock *sk, struct sock *ssk)
{
struct socket *sock;
write_lock_bh(&sk->sk_callback_lock);
sock = sk->sk_socket;
write_unlock_bh(&sk->sk_callback_lock);
if (sock)
mptcp_sock_graft(ssk, sock);
}
bool mptcp_finish_join(struct sock *ssk)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
@@ -3662,7 +3670,9 @@ bool mptcp_finish_join(struct sock *ssk)
return false;
}
/* active subflow, already present inside the conn_list */
/* Active subflow, already present inside the conn_list; is grafted
* either by __mptcp_subflow_connect() or accept.
*/
if (!list_empty(&subflow->node)) {
spin_lock_bh(&msk->fallback_lock);
if (!msk->allow_subflows) {
@@ -3689,11 +3699,17 @@ bool mptcp_finish_join(struct sock *ssk)
if (ret) {
sock_hold(ssk);
list_add_tail(&subflow->node, &msk->conn_list);
mptcp_sock_check_graft(parent, ssk);
}
} else {
sock_hold(ssk);
list_add_tail(&subflow->node, &msk->join_list);
__set_bit(MPTCP_FLUSH_JOIN_LIST, &msk->cb_flags);
/* In case of later failures, __mptcp_flush_join_list() will
* properly orphan the ssk via mptcp_close_ssk().
*/
mptcp_sock_check_graft(parent, ssk);
}
mptcp_data_unlock(parent);