Commit 5e15395f authored by Paolo Abeni's avatar Paolo Abeni Committed by Jakub Kicinski
Browse files

mptcp: fix ack generation for fallback msk 

mptcp_cleanup_rbuf() needs to know the last most recent, mptcp-level
rcv_wnd sent, and such information is tracked into the msk->old_wspace
field, updated at ack transmission time by mptcp_write_options().

Fallback socket do not add any mptcp options, such helper is never
invoked, and msk->old_wspace value remain stale. That in turn makes
ack generation at recvmsg() time quite random.

Address the issue ensuring mptcp_write_options() is invoked even for
fallback sockets, and just update the needed info in such a case.

The issue went unnoticed for a long time, as mptcp currently overshots
the fallback socket receive buffer autotune significantly. It is going
to change in the near future.

Fixes: e3859603 ("mptcp: better msk receive window updates")
Cc: stable@vger.kernel.org
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/594


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Reviewed-by: default avatarGeliang Tang <geliang@kernel.org>
Reviewed-by: default avatarMatthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: default avatarMatthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20251118-net-mptcp-misc-fixes-6-18-rc6-v1-1-806d3781c95f@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent e31a11be

net/mptcp/options.c

+22 −1
Original line number Diff line number Diff line
@@ -838,8 +838,11 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb, 


	opts->suboptions = 0;



	/* Force later mptcp_write_options(), but do not use any actual

	 * option space.

	 */

	if (unlikely(__mptcp_check_fallback(msk) && !mptcp_check_infinite_map(skb)))

		return false;

		return true;



	if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {

		if (mptcp_established_options_fastclose(sk, &opt_size, remaining, opts) ||
@@ -1319,6 +1322,20 @@ static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th) 
	WRITE_ONCE(msk->old_wspace, tp->rcv_wnd);

}



static void mptcp_track_rwin(struct tcp_sock *tp)

{

	const struct sock *ssk = (const struct sock *)tp;

	struct mptcp_subflow_context *subflow;

	struct mptcp_sock *msk;



	if (!ssk)

		return;



	subflow = mptcp_subflow_ctx(ssk);

	msk = mptcp_sk(subflow->conn);

	WRITE_ONCE(msk->old_wspace, tp->rcv_wnd);

}



__sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)

{

	struct csum_pseudo_header header;
@@ -1611,6 +1628,10 @@ void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp, 
				      opts->reset_transient,

				      opts->reset_reason);

		return;

	} else if (unlikely(!opts->suboptions)) {

		/* Fallback to TCP */

		mptcp_track_rwin(tp);

		return;

	}



	if (OPTION_MPTCP_PRIO & opts->suboptions) {