[PATCH mptcp-next v2 1/9] mptcp: add noncontiguous flag

[Geliang Tang <geliangtang@gmail.com>]

From: Geliang Tang <geliangtang@xiaomi.com>

This patch added a "noncontiguous" flag in the msk to track whether the
data is contiguous on a subflow. When retransmission happens, we could
set this flag, and once all retransmissions are DATA_ACK'd that flag
could be cleared.

When a bad checksum is detected and a single contiguous subflow is in
use, don't send RST + MP_FAIL, send data_ack + MP_FAIL instead.

Signed-off-by: Geliang Tang <geliangtang@xiaomi.com>
---
 net/mptcp/protocol.c |  7 +++++++
 net/mptcp/protocol.h |  2 ++
 net/mptcp/subflow.c  | 12 ++++++------
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index bb8a2a231479..81ea03b9fff6 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1095,6 +1095,9 @@ static void __mptcp_clean_una(struct sock *sk)
 
 		dfrag_uncharge(sk, delta);
 		cleaned = true;
+
+		if (dfrag->resend_count == 0)
+			WRITE_ONCE(msk->noncontiguous, false);
 	}
 
 	/* all retransmitted data acked, recovery completed */
@@ -1171,6 +1174,7 @@ mptcp_carve_data_frag(const struct mptcp_sock *msk, struct page_frag *pfrag,
 	dfrag->overhead = offset - orig_offset + sizeof(struct mptcp_data_frag);
 	dfrag->offset = offset + sizeof(struct mptcp_data_frag);
 	dfrag->already_sent = 0;
+	dfrag->resend_count = 0;
 	dfrag->page = pfrag->page;
 
 	return dfrag;
@@ -2454,6 +2458,8 @@ static void __mptcp_retrans(struct sock *sk)
 		dfrag->already_sent = max(dfrag->already_sent, info.sent);
 		tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
 			 info.size_goal);
+		dfrag->resend_count++;
+		WRITE_ONCE(msk->noncontiguous, true);
 	}
 
 	release_sock(ssk);
@@ -2872,6 +2878,7 @@ struct sock *mptcp_sk_clone(const struct sock *sk,
 	WRITE_ONCE(msk->fully_established, false);
 	if (mp_opt->suboptions & OPTION_MPTCP_CSUMREQD)
 		WRITE_ONCE(msk->csum_enabled, true);
+	WRITE_ONCE(msk->noncontiguous, false);
 
 	msk->write_seq = subflow_req->idsn + 1;
 	msk->snd_nxt = msk->write_seq;
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index d3e6fd1615f1..011f84ae1593 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -213,6 +213,7 @@ struct mptcp_data_frag {
 	u16 offset;
 	u16 overhead;
 	u16 already_sent;
+	u16 resend_count;
 	struct page *page;
 };
 
@@ -249,6 +250,7 @@ struct mptcp_sock {
 	bool		rcv_fastclose;
 	bool		use_64bit_ack; /* Set when we received a 64-bit DSN */
 	bool		csum_enabled;
+	bool		noncontiguous;
 	spinlock_t	join_list_lock;
 	struct work_struct work;
 	struct sk_buff  *ooo_last_skb;
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 1de7ce883c37..951aafb6021e 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1166,15 +1166,15 @@ static bool subflow_check_data_avail(struct sock *ssk)
 fallback:
 	/* RFC 8684 section 3.7. */
 	if (subflow->send_mp_fail) {
-		if (mptcp_has_another_subflow(ssk)) {
+		if (mptcp_has_another_subflow(ssk) || READ_ONCE(msk->noncontiguous)) {
+			ssk->sk_err = EBADMSG;
+			tcp_set_state(ssk, TCP_CLOSE);
+			subflow->reset_transient = 0;
+			subflow->reset_reason = MPTCP_RST_EMIDDLEBOX;
+			tcp_send_active_reset(ssk, GFP_ATOMIC);
 			while ((skb = skb_peek(&ssk->sk_receive_queue)))
 				sk_eat_skb(ssk, skb);
 		}
-		ssk->sk_err = EBADMSG;
-		tcp_set_state(ssk, TCP_CLOSE);
-		subflow->reset_transient = 0;
-		subflow->reset_reason = MPTCP_RST_EMIDDLEBOX;
-		tcp_send_active_reset(ssk, GFP_ATOMIC);
 		WRITE_ONCE(subflow->data_avail, 0);
 		return true;
 	}
-- 
2.31.1