[RFC PATCH mptcp-next v6 6/9] mptfo variables for msk, options. Fix loop retrans

[Dmytro Shytyi <dmytro@shytyi.net>]

Introduce mptfo variables for msk and options. 
Also fixe the infinite retransmissions in the end of second session. 
Suggestion @palbeni (SEP 1) during the meting to 'look at data_ack'

Signed-off-by: Dmytro Shytyi <dmytro@shytyi.net>
---
 net/mptcp/fastopen.c | 16 ++++++++++++++++
 net/mptcp/options.c  |  3 +++
 net/mptcp/protocol.h |  6 +++++-
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c
index 436e773d798a..149a4b1d3dac 100644
--- a/net/mptcp/fastopen.c
+++ b/net/mptcp/fastopen.c
@@ -91,3 +91,19 @@ int mptcp_setsockopt_sol_tcp_fastopen(struct mptcp_sock *msk, sockptr_t optval,
 
 	return ret;
 }
+
+void mptcp_treat_hshake_ack_fastopen(struct mptcp_sock *msk, struct mptcp_subflow_context *subflow,
+				 struct mptcp_options_received mp_opt)
+{
+	u64 ack_seq;
+
+	if (mp_opt.suboptions & OPTIONS_MPTCP_MPC && mp_opt.is_mptfo && msk->is_mptfo) {
+		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..185b069e57f4 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->is_mptfo = 1;
 			mp_opt->rcvr_key = get_unaligned_be64(ptr);
 			ptr += 8;
 		}
@@ -1124,6 +1125,8 @@ 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)) {
+		mptcp_treat_hshake_ack_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 2a4b6dfb6f8f..c364616c2d56 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;
+		is_mptfo:1,
+		__unused: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,
@@ -848,6 +850,8 @@ int mptcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg,
 			   size_t *copied);
 int mptcp_setsockopt_sol_tcp_fastopen(struct mptcp_sock *msk, sockptr_t optval,
 				      unsigned int optlen);
+void mptcp_treat_hshake_ack_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