6.5-stable review patch. If anyone has any objections, please let me know.
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From: Geliang Tang geliang.tang@suse.com
commit 14c56686a64c65ba716ff48f1f4b19c85f4cb2a9 upstream.
When closing the first subflow, the MPTCP protocol unconditionally calls tcp_disconnect(), which in turn generates a reset if the subflow is established.
That is unexpected and different from what MPTCP does with MPJ subflows, where resets are generated only on FASTCLOSE and other edge scenarios.
We can't reuse for the first subflow the same code in place for MPJ subflows, as MPTCP clean them up completely via a tcp_close() call, while must keep the first subflow socket alive for later re-usage, due to implementation constraints.
This patch adds a new helper __mptcp_subflow_disconnect() that encapsulates, a logic similar to tcp_close, issuing a reset only when the MPTCP_CF_FASTCLOSE flag is set, and performing a clean shutdown otherwise.
Fixes: c2b2ae3925b6 ("mptcp: handle correctly disconnect() failures") Cc: stable@vger.kernel.org Reviewed-by: Matthieu Baerts matttbe@kernel.org Co-developed-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Geliang Tang geliang.tang@suse.com Signed-off-by: Mat Martineau martineau@kernel.org Link: https://lore.kernel.org/r/20231018-send-net-20231018-v1-4-17ecb002e41d@kerne... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Matthieu Baerts matttbe@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mptcp/protocol.c | 28 ++++++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-)
--- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2336,6 +2336,26 @@ bool __mptcp_retransmit_pending_data(str #define MPTCP_CF_PUSH BIT(1) #define MPTCP_CF_FASTCLOSE BIT(2)
+/* be sure to send a reset only if the caller asked for it, also + * clean completely the subflow status when the subflow reaches + * TCP_CLOSE state + */ +static void __mptcp_subflow_disconnect(struct sock *ssk, + struct mptcp_subflow_context *subflow, + unsigned int flags) +{ + if (((1 << ssk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || + (flags & MPTCP_CF_FASTCLOSE)) { + /* The MPTCP code never wait on the subflow sockets, TCP-level + * disconnect should never fail + */ + WARN_ON_ONCE(tcp_disconnect(ssk, 0)); + mptcp_subflow_ctx_reset(subflow); + } else { + tcp_shutdown(ssk, SEND_SHUTDOWN); + } +} + /* subflow sockets can be either outgoing (connect) or incoming * (accept). * @@ -2373,7 +2393,7 @@ static void __mptcp_close_ssk(struct soc lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);
if ((flags & MPTCP_CF_FASTCLOSE) && !__mptcp_check_fallback(msk)) { - /* be sure to force the tcp_disconnect() path, + /* be sure to force the tcp_close path * to generate the egress reset */ ssk->sk_lingertime = 0; @@ -2383,12 +2403,8 @@ static void __mptcp_close_ssk(struct soc
need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk); if (!dispose_it) { - /* The MPTCP code never wait on the subflow sockets, TCP-level - * disconnect should never fail - */ - WARN_ON_ONCE(tcp_disconnect(ssk, 0)); + __mptcp_subflow_disconnect(ssk, subflow, flags); msk->subflow->state = SS_UNCONNECTED; - mptcp_subflow_ctx_reset(subflow); release_sock(ssk);
goto out;