1 files changed, 53 insertions, 1 deletions

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 1103b3341a70..f24ae7d40e88 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -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) ||
@@ -1041,6 +1044,31 @@ static void __mptcp_snd_una_update(struct mptcp_sock *msk, u64 new_snd_una)
 	WRITE_ONCE(msk->snd_una, new_snd_una);
 }
 
+static void rwin_update(struct mptcp_sock *msk, struct sock *ssk,
+			struct sk_buff *skb)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct tcp_sock *tp = tcp_sk(ssk);
+	u64 mptcp_rcv_wnd;
+
+	/* Avoid touching extra cachelines if TCP is going to accept this
+	 * skb without filling the TCP-level window even with a possibly
+	 * outdated mptcp-level rwin.
+	 */
+	if (!skb->len || skb->len < tcp_receive_window(tp))
+		return;
+
+	mptcp_rcv_wnd = atomic64_read(&msk->rcv_wnd_sent);
+	if (!after64(mptcp_rcv_wnd, subflow->rcv_wnd_sent))
+		return;
+
+	/* Some other subflow grew the mptcp-level rwin since rcv_wup,
+	 * resync.
+	 */
+	tp->rcv_wnd += mptcp_rcv_wnd - subflow->rcv_wnd_sent;
+	subflow->rcv_wnd_sent = mptcp_rcv_wnd;
+}
+
 static void ack_update_msk(struct mptcp_sock *msk,
 			   struct sock *ssk,
 			   struct mptcp_options_received *mp_opt)
@@ -1208,6 +1236,7 @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 	 */
 	if (mp_opt.use_ack)
 		ack_update_msk(msk, sk, &mp_opt);
+	rwin_update(msk, sk, skb);
 
 	/* Zero-data-length packets are dropped by the caller and not
 	 * propagated to the MPTCP layer, so the skb extension does not
@@ -1294,6 +1323,10 @@ static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th)
 
 	if (rcv_wnd_new != rcv_wnd_old) {
 raise_win:
+		/* The msk-level rcv wnd is after the tcp level one,
+		 * sync the latter.
+		 */
+		rcv_wnd_new = rcv_wnd_old;
 		win = rcv_wnd_old - ack_seq;
 		tp->rcv_wnd = min_t(u64, win, U32_MAX);
 		new_win = tp->rcv_wnd;
@@ -1317,6 +1350,21 @@ raise_win:
 
 update_wspace:
 	WRITE_ONCE(msk->old_wspace, tp->rcv_wnd);
+	subflow->rcv_wnd_sent = rcv_wnd_new;
+}
+
+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)
@@ -1611,6 +1659,10 @@ mp_rst:
 				      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) {