mptcp: consolidate initial ack seq generation

Currently the initial ack sequence is generated on demand whenever
it's requested and the remote key is handy. The relevant code is
scattered in different places and can lead to multiple, unneeded,
crypto operations.

This change consolidates the ack sequence generation code in a single
helper, storing the sequence number at the subflow level.

The above additionally saves a few conditional in fast-path and will
simplify the upcoming fast-open implementation.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 35 insertions, 22 deletions

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index f3c336872475..eca4de08ca9c 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -392,11 +392,33 @@ static void mptcp_set_connected(struct sock *sk)
 	mptcp_data_unlock(sk);
 }
 
+static void subflow_set_remote_key(struct mptcp_sock *msk,
+				   struct mptcp_subflow_context *subflow,
+				   const struct mptcp_options_received *mp_opt)
+{
+	/* active MPC subflow will reach here multiple times:
+	 * at subflow_finish_connect() time and at 4th ack time
+	 */
+	if (subflow->remote_key_valid)
+		return;
+
+	subflow->remote_key_valid = 1;
+	subflow->remote_key = mp_opt->sndr_key;
+	mptcp_crypto_key_sha(subflow->remote_key, NULL, &subflow->iasn);
+	subflow->iasn++;
+
+	WRITE_ONCE(msk->remote_key, subflow->remote_key);
+	WRITE_ONCE(msk->ack_seq, subflow->iasn);
+	WRITE_ONCE(msk->can_ack, true);
+	atomic64_set(&msk->rcv_wnd_sent, subflow->iasn);
+}
+
 static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 	struct mptcp_options_received mp_opt;
 	struct sock *parent = subflow->conn;
+	struct mptcp_sock *msk;
 
 	subflow->icsk_af_ops->sk_rx_dst_set(sk, skb);
 
@@ -404,6 +426,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 	if (subflow->conn_finished)
 		return;
 
+	msk = mptcp_sk(parent);
 	mptcp_propagate_sndbuf(parent, sk);
 	subflow->rel_write_seq = 1;
 	subflow->conn_finished = 1;
@@ -416,19 +439,16 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 			MPTCP_INC_STATS(sock_net(sk),
 					MPTCP_MIB_MPCAPABLEACTIVEFALLBACK);
 			mptcp_do_fallback(sk);
-			pr_fallback(mptcp_sk(subflow->conn));
+			pr_fallback(msk);
 			goto fallback;
 		}
 
 		if (mp_opt.suboptions & OPTION_MPTCP_CSUMREQD)
-			WRITE_ONCE(mptcp_sk(parent)->csum_enabled, true);
+			WRITE_ONCE(msk->csum_enabled, true);
 		if (mp_opt.deny_join_id0)
-			WRITE_ONCE(mptcp_sk(parent)->pm.remote_deny_join_id0, true);
+			WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
 		subflow->mp_capable = 1;
-		subflow->can_ack = 1;
-		subflow->remote_key = mp_opt.sndr_key;
-		pr_debug("subflow=%p, remote_key=%llu", subflow,
-			 subflow->remote_key);
+		subflow_set_remote_key(msk, subflow, &mp_opt);
 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVEACK);
 		mptcp_finish_connect(sk);
 		mptcp_set_connected(parent);
@@ -466,7 +486,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 		subflow->mp_join = 1;
 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKRX);
 
-		if (subflow_use_different_dport(mptcp_sk(parent), sk)) {
+		if (subflow_use_different_dport(msk, sk)) {
 			pr_debug("synack inet_dport=%d %d",
 				 ntohs(inet_sk(sk)->inet_dport),
 				 ntohs(inet_sk(parent)->inet_dport));
@@ -474,7 +494,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 		}
 	} else if (mptcp_check_fallback(sk)) {
 fallback:
-		mptcp_rcv_space_init(mptcp_sk(parent), sk);
+		mptcp_rcv_space_init(msk, sk);
 		mptcp_set_connected(parent);
 	}
 	return;
@@ -637,13 +657,12 @@ static void subflow_drop_ctx(struct sock *ssk)
 }
 
 void mptcp_subflow_fully_established(struct mptcp_subflow_context *subflow,
-				     struct mptcp_options_received *mp_opt)
+				     const struct mptcp_options_received *mp_opt)
 {
 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 
-	subflow->remote_key = mp_opt->sndr_key;
+	subflow_set_remote_key(msk, subflow, mp_opt);
 	subflow->fully_established = 1;
-	subflow->can_ack = 1;
 	WRITE_ONCE(msk->fully_established, true);
 }
 
@@ -1198,16 +1217,8 @@ static bool subflow_check_data_avail(struct sock *ssk)
 		if (WARN_ON_ONCE(!skb))
 			goto no_data;
 
-		/* if msk lacks the remote key, this subflow must provide an
-		 * MP_CAPABLE-based mapping
-		 */
-		if (unlikely(!READ_ONCE(msk->can_ack))) {
-			if (!subflow->mpc_map)
-				goto fallback;
-			WRITE_ONCE(msk->remote_key, subflow->remote_key);
-			WRITE_ONCE(msk->ack_seq, subflow->map_seq);
-			WRITE_ONCE(msk->can_ack, true);
-		}
+		if (unlikely(!READ_ONCE(msk->can_ack)))
+			goto fallback;
 
 		old_ack = READ_ONCE(msk->ack_seq);
 		ack_seq = mptcp_subflow_get_mapped_dsn(subflow);
@@ -1480,6 +1491,7 @@ int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
 
 	mptcp_pm_get_flags_and_ifindex_by_id(msk, local_id,
 					     &flags, &ifindex);
+	subflow->remote_key_valid = 1;
 	subflow->remote_key = msk->remote_key;
 	subflow->local_key = msk->local_key;
 	subflow->token = msk->token;
@@ -1873,6 +1885,7 @@ static void subflow_ulp_clone(const struct request_sock *req,
 		new_ctx->ssn_offset = subflow_req->ssn_offset;
 		new_ctx->mp_join = 1;
 		new_ctx->fully_established = 1;
+		new_ctx->remote_key_valid = 1;
 		new_ctx->backup = subflow_req->backup;
 		new_ctx->remote_id = subflow_req->remote_id;
 		new_ctx->token = subflow_req->token;