diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
index 6d16a9070ff0..117fb093dcaf 100644
--- a/net/dccp/ccid.h
+++ b/net/dccp/ccid.h
@@ -73,7 +73,7 @@ struct ccid_operations {
 	int		(*ccid_hc_tx_send_packet)(struct sock *sk,
 						  struct sk_buff *skb);
 	void		(*ccid_hc_tx_packet_sent)(struct sock *sk,
-						  int more, unsigned int len);
+						  unsigned int len);
 	void		(*ccid_hc_rx_get_info)(struct sock *sk,
 					       struct tcp_info *info);
 	void		(*ccid_hc_tx_get_info)(struct sock *sk,
@@ -144,10 +144,10 @@ static inline int ccid_hc_tx_send_packet(struct ccid *ccid, struct sock *sk,
 }
 
 static inline void ccid_hc_tx_packet_sent(struct ccid *ccid, struct sock *sk,
-					  int more, unsigned int len)
+					  unsigned int len)
 {
 	if (ccid->ccid_ops->ccid_hc_tx_packet_sent != NULL)
-		ccid->ccid_ops->ccid_hc_tx_packet_sent(sk, more, len);
+		ccid->ccid_ops->ccid_hc_tx_packet_sent(sk, len);
 }
 
 static inline void ccid_hc_rx_packet_recv(struct ccid *ccid, struct sock *sk,
diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index dc18172b1e59..d850e291f87c 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -151,7 +151,7 @@ out:
 	sock_put(sk);
 }
 
-static void ccid2_hc_tx_packet_sent(struct sock *sk, int more, unsigned int len)
+static void ccid2_hc_tx_packet_sent(struct sock *sk, unsigned int len)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index c3f3a25bbd7a..3060a60ed5ab 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -351,8 +351,7 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
 	return 0;
 }
 
-static void ccid3_hc_tx_packet_sent(struct sock *sk, int more,
-				    unsigned int len)
+static void ccid3_hc_tx_packet_sent(struct sock *sk, unsigned int len)
 {
 	struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
 
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 019d6ffee354..3eb264b60823 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -153,18 +153,27 @@ static inline u64 max48(const u64 seq1, const u64 seq2)
 }
 
 /**
- * dccp_loss_free  -  Evaluates condition for data loss from RFC 4340, 7.7.1
- * @s1:	 start sequence number
- * @s2:  end sequence number
+ * dccp_loss_count - Approximate the number of lost data packets in a burst loss
+ * @s1:  last known sequence number before the loss ('hole')
+ * @s2:  first sequence number seen after the 'hole'
  * @ndp: NDP count on packet with sequence number @s2
- * Returns true if the sequence range s1...s2 has no data loss.
  */
-static inline bool dccp_loss_free(const u64 s1, const u64 s2, const u64 ndp)
+static inline u64 dccp_loss_count(const u64 s1, const u64 s2, const u64 ndp)
 {
 	s64 delta = dccp_delta_seqno(s1, s2);
 
 	WARN_ON(delta < 0);
-	return (u64)delta <= ndp + 1;
+	delta -= ndp + 1;
+
+	return delta > 0 ? delta : 0;
+}
+
+/**
+ * dccp_loss_free - Evaluate condition for data loss from RFC 4340, 7.7.1
+ */
+static inline bool dccp_loss_free(const u64 s1, const u64 s2, const u64 ndp)
+{
+	return dccp_loss_count(s1, s2, ndp) == 0;
 }
 
 enum {
@@ -414,6 +423,23 @@ static inline void dccp_update_gsr(struct sock *sk, u64 seq)
 	dp->dccps_gsr = seq;
 	/* Sequence validity window depends on remote Sequence Window (7.5.1) */
 	dp->dccps_swl = SUB48(ADD48(dp->dccps_gsr, 1), dp->dccps_r_seq_win / 4);
+	/*
+	 * Adjust SWL so that it is not below ISR. In contrast to RFC 4340,
+	 * 7.5.1 we perform this check beyond the initial handshake: W/W' are
+	 * always > 32, so for the first W/W' packets in the lifetime of a
+	 * connection we always have to adjust SWL.
+	 * A second reason why we are doing this is that the window depends on
+	 * the feature-remote value of Sequence Window: nothing stops the peer
+	 * from updating this value while we are busy adjusting SWL for the
+	 * first W packets (we would have to count from scratch again then).
+	 * Therefore it is safer to always make sure that the Sequence Window
+	 * is not artificially extended by a peer who grows SWL downwards by
+	 * continually updating the feature-remote Sequence-Window.
+	 * If sequence numbers wrap it is bad luck. But that will take a while
+	 * (48 bit), and this measure prevents Sequence-number attacks.
+	 */
+	if (before48(dp->dccps_swl, dp->dccps_isr))
+		dp->dccps_swl = dp->dccps_isr;
 	dp->dccps_swh = ADD48(dp->dccps_gsr, (3 * dp->dccps_r_seq_win) / 4);
 }
 
@@ -424,14 +450,16 @@ static inline void dccp_update_gss(struct sock *sk, u64 seq)
 	dp->dccps_gss = seq;
 	/* Ack validity window depends on local Sequence Window value (7.5.1) */
 	dp->dccps_awl = SUB48(ADD48(dp->dccps_gss, 1), dp->dccps_l_seq_win);
+	/* Adjust AWL so that it is not below ISS - see comment above for SWL */
+	if (before48(dp->dccps_awl, dp->dccps_iss))
+		dp->dccps_awl = dp->dccps_iss;
 	dp->dccps_awh = dp->dccps_gss;
 }
 
 static inline int dccp_ack_pending(const struct sock *sk)
 {
 	const struct dccp_sock *dp = dccp_sk(sk);
-	return dp->dccps_timestamp_echo != 0 ||
-	       (dp->dccps_hc_rx_ackvec != NULL &&
+	return (dp->dccps_hc_rx_ackvec != NULL &&
 		dccp_ackvec_pending(dp->dccps_hc_rx_ackvec)) ||
 	       inet_csk_ack_scheduled(sk);
 }
diff --git a/net/dccp/input.c b/net/dccp/input.c
index 10c957a88f4f..265985370fa1 100644
--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -259,7 +259,7 @@ static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
 				      sysctl_dccp_sync_ratelimit)))
 			return 0;
 
-		DCCP_WARN("DCCP: Step 6 failed for %s packet, "
+		DCCP_WARN("Step 6 failed for %s packet, "
 			  "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
 			  "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
 			  "sending SYNC...\n",  dccp_packet_name(dh->dccph_type),
@@ -441,20 +441,14 @@ static int dccp_rcv_request_sent_state_process(struct sock *sk,
 		kfree_skb(sk->sk_send_head);
 		sk->sk_send_head = NULL;
 
-		dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
-		dccp_update_gsr(sk, dp->dccps_isr);
 		/*
-		 * SWL and AWL are initially adjusted so that they are not less than
-		 * the initial Sequence Numbers received and sent, respectively:
-		 *	SWL := max(GSR + 1 - floor(W/4), ISR),
-		 *	AWL := max(GSS - W' + 1, ISS).
-		 * These adjustments MUST be applied only at the beginning of the
-		 * connection.
-		 *
-		 * AWL was adjusted in dccp_v4_connect -acme
+		 * Set ISR, GSR from packet. ISS was set in dccp_v{4,6}_connect
+		 * and GSS in dccp_transmit_skb(). Setting AWL/AWH and SWL/SWH
+		 * is done as part of activating the feature values below, since
+		 * these settings depend on the local/remote Sequence Window
+		 * features, which were undefined or not confirmed until now.
 		 */
-		dccp_set_seqno(&dp->dccps_swl,
-			       max48(dp->dccps_swl, dp->dccps_isr));
+		dp->dccps_gsr = dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 
 		dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index 128b089d3aef..d7041a0963af 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -121,30 +121,18 @@ struct sock *dccp_create_openreq_child(struct sock *sk,
 		 *
 		 *    Choose S.ISS (initial seqno) or set from Init Cookies
 		 *    Initialize S.GAR := S.ISS
-		 *    Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
+		 *    Set S.ISR, S.GSR from packet (or Init Cookies)
+		 *
+		 *    Setting AWL/AWH and SWL/SWH happens as part of the feature
+		 *    activation below, as these windows all depend on the local
+		 *    and remote Sequence Window feature values (7.5.2).
 		 */
-		newdp->dccps_gar = newdp->dccps_iss = dreq->dreq_iss;
-		dccp_update_gss(newsk, dreq->dreq_iss);
-
-		newdp->dccps_isr = dreq->dreq_isr;
-		dccp_update_gsr(newsk, dreq->dreq_isr);
+		newdp->dccps_gss = newdp->dccps_iss = dreq->dreq_iss;
+		newdp->dccps_gar = newdp->dccps_iss;
+		newdp->dccps_gsr = newdp->dccps_isr = dreq->dreq_isr;
 
 		/*
-		 * SWL and AWL are initially adjusted so that they are not less than
-		 * the initial Sequence Numbers received and sent, respectively:
-		 *	SWL := max(GSR + 1 - floor(W/4), ISR),
-		 *	AWL := max(GSS - W' + 1, ISS).
-		 * These adjustments MUST be applied only at the beginning of the
-		 * connection.
-		 */
-		dccp_set_seqno(&newdp->dccps_swl,
-			       max48(newdp->dccps_swl, newdp->dccps_isr));
-		dccp_set_seqno(&newdp->dccps_awl,
-			       max48(newdp->dccps_awl, newdp->dccps_iss));
-
-		/*
-		 * Activate features after initialising the sequence numbers,
-		 * since CCID initialisation may depend on GSS, ISR, ISS etc.
+		 * Activate features: initialise CCIDs, sequence windows etc.
 		 */
 		if (dccp_feat_activate_values(newsk, &dreq->dreq_featneg)) {
 			/* It is still raw copy of parent, so invalidate
diff --git a/net/dccp/options.c b/net/dccp/options.c
index d4b1ae0daacb..cd3061813009 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -163,6 +163,8 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
 				      dccp_role(sk), ntohl(opt_val),
 				      (unsigned long long)
 				      DCCP_SKB_CB(skb)->dccpd_ack_seq);
+			/* schedule an Ack in case this sender is quiescent */
+			inet_csk_schedule_ack(sk);
 			break;
 		case DCCPO_TIMESTAMP_ECHO:
 			if (len != 4 && len != 6 && len != 8)
diff --git a/net/dccp/output.c b/net/dccp/output.c
index aadbdb58758b..a988fe9ffcba 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -304,7 +304,7 @@ void dccp_write_xmit(struct sock *sk, int block)
 				dcb->dccpd_type = DCCP_PKT_DATA;
 
 			err = dccp_transmit_skb(sk, skb);
-			ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, 0, len);
+			ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len);
 			if (err)
 				DCCP_BUG("err=%d after ccid_hc_tx_packet_sent",
 					 err);
@@ -474,8 +474,9 @@ int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
 /*
  * Do all connect socket setups that can be done AF independent.
  */
-static inline void dccp_connect_init(struct sock *sk)
+int dccp_connect(struct sock *sk)
 {
+	struct sk_buff *skb;
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct dst_entry *dst = __sk_dst_get(sk);
 	struct inet_connection_sock *icsk = inet_csk(sk);
@@ -485,22 +486,12 @@ static inline void dccp_connect_init(struct sock *sk)
 
 	dccp_sync_mss(sk, dst_mtu(dst));
 
-	/* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */
-	dp->dccps_gar = dp->dccps_iss;
-
-	icsk->icsk_retransmits = 0;
-}
-
-int dccp_connect(struct sock *sk)
-{
-	struct sk_buff *skb;
-	struct inet_connection_sock *icsk = inet_csk(sk);
-
 	/* do not connect if feature negotiation setup fails */
 	if (dccp_feat_finalise_settings(dccp_sk(sk)))
 		return -EPROTO;
 
-	dccp_connect_init(sk);
+	/* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */
+	dp->dccps_gar = dp->dccps_iss;
 
 	skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
 	if (unlikely(skb == NULL))
@@ -516,6 +507,7 @@ int dccp_connect(struct sock *sk)
 	DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
 
 	/* Timer for repeating the REQUEST until an answer. */
+	icsk->icsk_retransmits = 0;
 	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 				  icsk->icsk_rto, DCCP_RTO_MAX);
 	return 0;
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index b054ba1f55d2..7e5fc04eb6d1 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -944,7 +944,7 @@ void dccp_close(struct sock *sk, long timeout)
 
 	if (data_was_unread) {
 		/* Unread data was tossed, send an appropriate Reset Code */
-		DCCP_WARN("DCCP: ABORT -- %u bytes unread\n", data_was_unread);
+		DCCP_WARN("ABORT with %u bytes unread\n", data_was_unread);
 		dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED);
 		dccp_set_state(sk, DCCP_CLOSED);
 	} else if (sock_flag(sk, SOCK_LINGER) && !sk->sk_lingertime) {