[RFC PATCH mptcp-next v8 4/7] mptfo variables for msk, options. Fix loop retrans

[Dmytro Shytyi <dmytro@shytyi.net>]

Introduce mptfo variables for msk and options.
Also fix the infinite retransmissions in the end of second session.

The variable 2nd ack received in struct mptcp_options_received identifies the
received ack on the listener side during 3way handshake in mptfo context
and miningless alone if used alone. It is further used(checked)
in conjunction in the same "if" statement with variable is_mptfo
from struct mptcp_sock.

Signed-off-by: Dmytro Shytyi <dmytro@shytyi.net>
---
 net/mptcp/fastopen.c | 14 ++++++++++++++
 net/mptcp/options.c  |  4 ++++
 net/mptcp/protocol.h |  6 +++++-
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c
index 9ef49a2d2ea2..92885e459f93 100644
--- a/net/mptcp/fastopen.c
+++ b/net/mptcp/fastopen.c
@@ -30,3 +30,17 @@ int mptcp_setsockopt_sol_tcp_fastopen(struct mptcp_sock *msk, sockptr_t optval,
 
 	return ret;
 }
+
+void mptcp_gen_msk_ackseq_fastopen(struct mptcp_sock *msk, struct mptcp_subflow_context *subflow,
+				   struct mptcp_options_received mp_opt)
+{
+	u64 ack_seq;
+
+	msk->can_ack = true;
+	msk->remote_key = mp_opt.sndr_key;
+	mptcp_crypto_key_sha(msk->remote_key, NULL, &ack_seq);
+	ack_seq++;
+	WRITE_ONCE(msk->ack_seq, ack_seq);
+	pr_debug("ack_seq=%llu sndr_key=%llu", msk->ack_seq, mp_opt.sndr_key);
+	atomic64_set(&msk->rcv_wnd_sent, ack_seq);
+}
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 30d289044e71..8852a13cfe62 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -91,6 +91,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 			ptr += 8;
 		}
 		if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
+			mp_opt->hns_2nd_ack_rcvd = 1;
 			mp_opt->rcvr_key = get_unaligned_be64(ptr);
 			ptr += 8;
 		}
@@ -1124,6 +1125,9 @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 		return sk->sk_state != TCP_CLOSE;
 
 	if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) {
+		if (mp_opt.suboptions & OPTIONS_MPTCP_MPC && mp_opt.hns_2nd_ack_rcvd && msk->is_mptfo)
+			mptcp_gen_msk_ackseq_fastopen(msk, subflow, mp_opt);
+
 		if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) &&
 		    msk->local_key == mp_opt.rcvr_key) {
 			WRITE_ONCE(msk->rcv_fastclose, true);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 57596cdfb1f9..3b9a349a7080 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -155,7 +155,8 @@ struct mptcp_options_received {
 		echo:1,
 		backup:1,
 		deny_join_id0:1,
-		__unused:2;
+		__unused:1;
+	u8	hns_2nd_ack_rcvd:1;
 	u8	join_id;
 	u64	thmac;
 	u8	hmac[MPTCPOPT_HMAC_LEN];
@@ -282,6 +283,7 @@ struct mptcp_sock {
 	bool		use_64bit_ack; /* Set when we received a 64-bit DSN */
 	bool		csum_enabled;
 	bool		allow_infinite_fallback;
+	bool		is_mptfo;
 	u8		mpc_endpoint_id;
 	u8		recvmsg_inq:1,
 			cork:1,
@@ -842,6 +844,8 @@ int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr, int addr_l
 // Fast Open Mechanism functions begin
 int mptcp_setsockopt_sol_tcp_fastopen(struct mptcp_sock *msk, sockptr_t optval,
 				      unsigned int optlen);
+void mptcp_gen_msk_ackseq_fastopen(struct mptcp_sock *msk, struct mptcp_subflow_context *subflow,
+				   struct mptcp_options_received mp_opt);
 // Fast Open Mechanism functions end
 
 static inline bool mptcp_pm_should_add_signal(struct mptcp_sock *msk)
-- 
2.25.1