1 files changed, 94 insertions, 14 deletions

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 8e2b2dbadf6d..20ba00865c55 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -328,6 +328,16 @@ bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 		opts->sndr_key = subflow->local_key;
 		*size = TCPOLEN_MPTCP_MPC_SYN;
 		return true;
+	} else if (subflow->request_join) {
+		pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
+			 subflow->local_nonce);
+		opts->suboptions = OPTION_MPTCP_MPJ_SYN;
+		opts->join_id = subflow->local_id;
+		opts->token = subflow->remote_token;
+		opts->nonce = subflow->local_nonce;
+		opts->backup = subflow->request_bkup;
+		*size = TCPOLEN_MPTCP_MPJ_SYN;
+		return true;
 	}
 	return false;
 }
@@ -337,16 +347,55 @@ void mptcp_rcv_synsent(struct sock *sk)
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
 
-	pr_debug("subflow=%p", subflow);
 	if (subflow->request_mptcp && tp->rx_opt.mptcp.mp_capable) {
 		subflow->mp_capable = 1;
 		subflow->can_ack = 1;
 		subflow->remote_key = tp->rx_opt.mptcp.sndr_key;
-	} else {
+		pr_debug("subflow=%p, remote_key=%llu", subflow,
+			 subflow->remote_key);
+	} else if (subflow->request_join && tp->rx_opt.mptcp.mp_join) {
+		subflow->mp_join = 1;
+		subflow->thmac = tp->rx_opt.mptcp.thmac;
+		subflow->remote_nonce = tp->rx_opt.mptcp.nonce;
+		pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u", subflow,
+			 subflow->thmac, subflow->remote_nonce);
+	} else if (subflow->request_mptcp) {
 		tcp_sk(sk)->is_mptcp = 0;
 	}
 }
 
+/* MP_JOIN client subflow must wait for 4th ack before sending any data:
+ * TCP can't schedule delack timer before the subflow is fully established.
+ * MPTCP uses the delack timer to do 3rd ack retransmissions
+ */
+static void schedule_3rdack_retransmission(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
+	unsigned long timeout;
+
+	/* reschedule with a timeout above RTT, as we must look only for drop */
+	if (tp->srtt_us)
+		timeout = tp->srtt_us << 1;
+	else
+		timeout = TCP_TIMEOUT_INIT;
+
+	WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
+	icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
+	icsk->icsk_ack.timeout = timeout;
+	sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
+}
+
+static void clear_3rdack_retransmission(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+
+	sk_stop_timer(sk, &icsk->icsk_delack_timer);
+	icsk->icsk_ack.timeout = 0;
+	icsk->icsk_ack.ato = 0;
+	icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
+}
+
 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 					 unsigned int *size,
 					 unsigned int remaining,
@@ -356,17 +405,21 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 	struct mptcp_ext *mpext;
 	unsigned int data_len;
 
-	pr_debug("subflow=%p fully established=%d seq=%x:%x remaining=%d",
-		 subflow, subflow->fully_established, subflow->snd_isn,
-		 skb ? TCP_SKB_CB(skb)->seq : 0, remaining);
+	/* When skb is not available, we better over-estimate the emitted
+	 * options len. A full DSS option (28 bytes) is longer than
+	 * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
+	 * tell the caller to defer the estimate to
+	 * mptcp_established_options_dss(), which will reserve enough space.
+	 */
+	if (!skb)
+		return false;
 
-	if (subflow->mp_capable && !subflow->fully_established && skb &&
-	    subflow->snd_isn == TCP_SKB_CB(skb)->seq) {
-		/* When skb is not available, we better over-estimate the
-		 * emitted options len. A full DSS option is longer than
-		 * TCPOLEN_MPTCP_MPC_ACK_DATA, so let's the caller try to fit
-		 * that.
-		 */
+	/* MPC/MPJ needed only on 3rd ack packet */
+	if (subflow->fully_established ||
+	    subflow->snd_isn != TCP_SKB_CB(skb)->seq)
+		return false;
+
+	if (subflow->mp_capable) {
 		mpext = mptcp_get_ext(skb);
 		data_len = mpext ? mpext->data_len : 0;
 
@@ -394,6 +447,14 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 			 data_len);
 
 		return true;
+	} else if (subflow->mp_join) {
+		opts->suboptions = OPTION_MPTCP_MPJ_ACK;
+		memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
+		*size = TCPOLEN_MPTCP_MPJ_ACK;
+		pr_debug("subflow=%p", subflow);
+
+		schedule_3rdack_retransmission(sk);
+		return true;
 	}
 	return false;
 }
@@ -674,10 +735,12 @@ fully_established:
 		return true;
 
 	subflow->pm_notified = 1;
-	if (subflow->mp_join)
+	if (subflow->mp_join) {
+		clear_3rdack_retransmission(sk);
 		mptcp_pm_subflow_established(msk, subflow);
-	else
+	} else {
 		mptcp_pm_fully_established(msk);
+	}
 	return true;
 }
 
@@ -860,6 +923,16 @@ mp_capable_done:
 				      0, opts->rm_id);
 	}
 
+	if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
+		*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
+				      TCPOLEN_MPTCP_MPJ_SYN,
+				      opts->backup, opts->join_id);
+		put_unaligned_be32(opts->token, ptr);
+		ptr += 1;
+		put_unaligned_be32(opts->nonce, ptr);
+		ptr += 1;
+	}
+
 	if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
 		*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
 				      TCPOLEN_MPTCP_MPJ_SYNACK,
@@ -870,6 +943,13 @@ mp_capable_done:
 		ptr += 1;
 	}
 
+	if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
+		*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
+				      TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
+		memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
+		ptr += 5;
+	}
+
 	if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
 		struct mptcp_ext *mpext = &opts->ext_copy;
 		u8 len = TCPOLEN_MPTCP_DSS_BASE;