[PATCH net-next 4/8] mptcp: implement delayed seq generation for passive fastopen

[Matthieu Baerts]

From: Dmytro Shytyi <dmytro@xxxxxxxxxx>

With fastopen in place, the first subflow socket is created before the
MPC handshake completes, and we need to properly initialize the sequence
numbers at MPC ACK reception.

Co-developed-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Co-developed-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
Signed-off-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
Signed-off-by: Dmytro Shytyi <dmytro@xxxxxxxxxx>
Signed-off-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
---
 net/mptcp/Makefile   |  2 +-
 net/mptcp/fastopen.c | 28 ++++++++++++++++++++++++++++
 net/mptcp/options.c  |  9 ++++++---
 net/mptcp/protocol.c |  9 ---------
 net/mptcp/protocol.h | 16 +++++++++++++++-
 net/mptcp/subflow.c  |  5 ++++-
 6 files changed, 54 insertions(+), 15 deletions(-)
 create mode 100644 net/mptcp/fastopen.c

diff --git a/net/mptcp/Makefile b/net/mptcp/Makefile
index 6e7df47c9584..a3829ce548f9 100644
--- a/net/mptcp/Makefile
+++ b/net/mptcp/Makefile
@@ -2,7 +2,7 @@
 obj-$(CONFIG_MPTCP) += mptcp.o
 
 mptcp-y := protocol.o subflow.o options.o token.o crypto.o ctrl.o pm.o diag.o \
-	   mib.o pm_netlink.o sockopt.o pm_userspace.o
+	   mib.o pm_netlink.o sockopt.o pm_userspace.o fastopen.o
 
 obj-$(CONFIG_SYN_COOKIES) += syncookies.o
 obj-$(CONFIG_INET_MPTCP_DIAG) += mptcp_diag.o
diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c
new file mode 100644
index 000000000000..19c332af0834
--- /dev/null
+++ b/net/mptcp/fastopen.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+/* MPTCP Fast Open Mechanism
+ *
+ * Copyright (c) 2021-2022, Dmytro SHYTYI
+ */
+
+#include "protocol.h"
+
+void mptcp_fastopen_gen_msk_ackseq(struct mptcp_sock *msk, struct mptcp_subflow_context *subflow,
+				   const struct mptcp_options_received *mp_opt)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct sk_buff *skb;
+
+	mptcp_data_lock(sk);
+	skb = skb_peek_tail(&sk->sk_receive_queue);
+	if (skb) {
+		WARN_ON_ONCE(MPTCP_SKB_CB(skb)->end_seq);
+		pr_debug("msk %p moving seq %llx -> %llx end_seq %llx -> %llx", sk,
+			 MPTCP_SKB_CB(skb)->map_seq, MPTCP_SKB_CB(skb)->map_seq + msk->ack_seq,
+			 MPTCP_SKB_CB(skb)->end_seq, MPTCP_SKB_CB(skb)->end_seq + msk->ack_seq);
+		MPTCP_SKB_CB(skb)->map_seq += msk->ack_seq;
+		MPTCP_SKB_CB(skb)->end_seq += msk->ack_seq;
+	}
+
+	pr_debug("msk=%p ack_seq=%llx", msk, msk->ack_seq);
+	mptcp_data_unlock(sk);
+}
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index ae076468fcb9..5ded85e2c374 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -939,7 +939,7 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 		    subflow->mp_join && (mp_opt->suboptions & OPTIONS_MPTCP_MPJ) &&
 		    !subflow->request_join)
 			tcp_send_ack(ssk);
-		goto fully_established;
+		goto check_notify;
 	}
 
 	/* we must process OoO packets before the first subflow is fully
@@ -950,6 +950,8 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 	if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
 		if (subflow->mp_join)
 			goto reset;
+		if (subflow->is_mptfo && mp_opt->suboptions & OPTION_MPTCP_MPC_ACK)
+			goto set_fully_established;
 		return subflow->mp_capable;
 	}
 
@@ -961,7 +963,7 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 		 */
 		subflow->fully_established = 1;
 		WRITE_ONCE(msk->fully_established, true);
-		goto fully_established;
+		goto check_notify;
 	}
 
 	/* If the first established packet does not contain MP_CAPABLE + data
@@ -980,11 +982,12 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 	if (mp_opt->deny_join_id0)
 		WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
 
+set_fully_established:
 	if (unlikely(!READ_ONCE(msk->pm.server_side)))
 		pr_warn_once("bogus mpc option on established client sk");
 	mptcp_subflow_fully_established(subflow, mp_opt);
 
-fully_established:
+check_notify:
 	/* if the subflow is not already linked into the conn_list, we can't
 	 * notify the PM: this subflow is still on the listener queue
 	 * and the PM possibly acquiring the subflow lock could race with
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 00de7f4fce10..a12ee763e52c 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -36,15 +36,6 @@ struct mptcp6_sock {
 };
 #endif
 
-struct mptcp_skb_cb {
-	u64 map_seq;
-	u64 end_seq;
-	u32 offset;
-	u8  has_rxtstamp:1;
-};
-
-#define MPTCP_SKB_CB(__skb)	((struct mptcp_skb_cb *)&((__skb)->cb[0]))
-
 enum {
 	MPTCP_CMSG_TS = BIT(0),
 	MPTCP_CMSG_INQ = BIT(1),
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index b5abea3d1a9c..618ac85abaaf 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -126,6 +126,15 @@
 #define MPTCP_CONNECTED		6
 #define MPTCP_RESET_SCHEDULER	7
 
+struct mptcp_skb_cb {
+	u64 map_seq;
+	u64 end_seq;
+	u32 offset;
+	u8  has_rxtstamp:1;
+};
+
+#define MPTCP_SKB_CB(__skb)	((struct mptcp_skb_cb *)&((__skb)->cb[0]))
+
 static inline bool before64(__u64 seq1, __u64 seq2)
 {
 	return (__s64)(seq1 - seq2) < 0;
@@ -471,7 +480,9 @@ struct mptcp_subflow_context {
 		disposable : 1,	    /* ctx can be free at ulp release time */
 		stale : 1,	    /* unable to snd/rcv data, do not use for xmit */
 		local_id_valid : 1, /* local_id is correctly initialized */
-		valid_csum_seen : 1;        /* at least one csum validated */
+		valid_csum_seen : 1,        /* at least one csum validated */
+		is_mptfo : 1,	    /* subflow is doing TFO */
+		__unused : 8;
 	enum mptcp_data_avail data_avail;
 	u32	remote_nonce;
 	u64	thmac;
@@ -829,6 +840,9 @@ void mptcp_event_addr_announced(const struct sock *ssk, const struct mptcp_addr_
 void mptcp_event_addr_removed(const struct mptcp_sock *msk, u8 id);
 bool mptcp_userspace_pm_active(const struct mptcp_sock *msk);
 
+void mptcp_fastopen_gen_msk_ackseq(struct mptcp_sock *msk, struct mptcp_subflow_context *subflow,
+				   const struct mptcp_options_received *mp_opt);
+
 static inline bool mptcp_pm_should_add_signal(struct mptcp_sock *msk)
 {
 	return READ_ONCE(msk->pm.addr_signal) &
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 470e12ce0950..21cf26edb79a 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -664,6 +664,9 @@ void mptcp_subflow_fully_established(struct mptcp_subflow_context *subflow,
 	subflow_set_remote_key(msk, subflow, mp_opt);
 	subflow->fully_established = 1;
 	WRITE_ONCE(msk->fully_established, true);
+
+	if (subflow->is_mptfo)
+		mptcp_fastopen_gen_msk_ackseq(msk, subflow, mp_opt);
 }
 
 static struct sock *subflow_syn_recv_sock(const struct sock *sk,
@@ -779,7 +782,7 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 			/* with OoO packets we can reach here without ingress
 			 * mpc option
 			 */
-			if (mp_opt.suboptions & OPTIONS_MPTCP_MPC)
+			if (mp_opt.suboptions & OPTION_MPTCP_MPC_ACK)
 				mptcp_subflow_fully_established(ctx, &mp_opt);
 		} else if (ctx->mp_join) {
 			struct mptcp_sock *owner;
-- 
2.37.2