7 files changed, 756 insertions, 573 deletions

diff --git a/net/dccp/ccids/lib/Makefile b/net/dccp/ccids/lib/Makefile
index 5f940a6cbac..68c93e3d89d 100644
--- a/net/dccp/ccids/lib/Makefile
+++ b/net/dccp/ccids/lib/Makefile
@@ -1,3 +1,3 @@
 obj-$(CONFIG_IP_DCCP_TFRC_LIB) += dccp_tfrc_lib.o
 
-dccp_tfrc_lib-y := loss_interval.o packet_history.o tfrc_equation.o
+dccp_tfrc_lib-y := tfrc.o tfrc_equation.o packet_history.o loss_interval.o
diff --git a/net/dccp/ccids/lib/loss_interval.c b/net/dccp/ccids/lib/loss_interval.c
index d26b88dbbb4..849e181e698 100644
--- a/net/dccp/ccids/lib/loss_interval.c
+++ b/net/dccp/ccids/lib/loss_interval.c
@@ -1,6 +1,7 @@
 /*
  *  net/dccp/ccids/lib/loss_interval.c
  *
+ *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
  *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
  *  Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
@@ -10,285 +11,176 @@
  *  the Free Software Foundation; either version 2 of the License, or
  *  (at your option) any later version.
  */
-
-#include <linux/module.h>
 #include <net/sock.h>
-#include "../../dccp.h"
-#include "loss_interval.h"
-#include "packet_history.h"
 #include "tfrc.h"
 
-#define DCCP_LI_HIST_IVAL_F_LENGTH  8
-
-struct dccp_li_hist_entry {
-	struct list_head dccplih_node;
-	u64		 dccplih_seqno:48,
-			 dccplih_win_count:4;
-	u32		 dccplih_interval;
-};
+static struct kmem_cache  *tfrc_lh_slab  __read_mostly;
+/* Loss Interval weights from [RFC 3448, 5.4], scaled by 10 */
+static const int tfrc_lh_weights[NINTERVAL] = { 10, 10, 10, 10, 8, 6, 4, 2 };
 
-static struct kmem_cache *dccp_li_cachep __read_mostly;
-
-static inline struct dccp_li_hist_entry *dccp_li_hist_entry_new(const gfp_t prio)
+/* implements LIFO semantics on the array */
+static inline u8 LIH_INDEX(const u8 ctr)
 {
-	return kmem_cache_alloc(dccp_li_cachep, prio);
+	return (LIH_SIZE - 1 - (ctr % LIH_SIZE));
 }
 
-static inline void dccp_li_hist_entry_delete(struct dccp_li_hist_entry *entry)
+/* the `counter' index always points at the next entry to be populated */
+static inline struct tfrc_loss_interval *tfrc_lh_peek(struct tfrc_loss_hist *lh)
 {
-	if (entry != NULL)
-		kmem_cache_free(dccp_li_cachep, entry);
+	return lh->counter ? lh->ring[LIH_INDEX(lh->counter - 1)] : NULL;
 }
 
-void dccp_li_hist_purge(struct list_head *list)
+/* given i with 0 <= i <= k, return I_i as per the rfc3448bis notation */
+static inline u32 tfrc_lh_get_interval(struct tfrc_loss_hist *lh, const u8 i)
 {
-	struct dccp_li_hist_entry *entry, *next;
-
-	list_for_each_entry_safe(entry, next, list, dccplih_node) {
-		list_del_init(&entry->dccplih_node);
-		kmem_cache_free(dccp_li_cachep, entry);
-	}
+	BUG_ON(i >= lh->counter);
+	return lh->ring[LIH_INDEX(lh->counter - i - 1)]->li_length;
 }
 
-EXPORT_SYMBOL_GPL(dccp_li_hist_purge);
-
-/* Weights used to calculate loss event rate */
 /*
- * These are integers as per section 8 of RFC3448. We can then divide by 4 *
- * when we use it.
+ *	On-demand allocation and de-allocation of entries
  */
-static const int dccp_li_hist_w[DCCP_LI_HIST_IVAL_F_LENGTH] = {
-	4, 4, 4, 4, 3, 2, 1, 1,
-};
-
-u32 dccp_li_hist_calc_i_mean(struct list_head *list)
+static struct tfrc_loss_interval *tfrc_lh_demand_next(struct tfrc_loss_hist *lh)
 {
-	struct dccp_li_hist_entry *li_entry, *li_next;
-	int i = 0;
-	u32 i_tot;
-	u32 i_tot0 = 0;
-	u32 i_tot1 = 0;
-	u32 w_tot  = 0;
-
-	list_for_each_entry_safe(li_entry, li_next, list, dccplih_node) {
-		if (li_entry->dccplih_interval != ~0U) {
-			i_tot0 += li_entry->dccplih_interval * dccp_li_hist_w[i];
-			w_tot  += dccp_li_hist_w[i];
-			if (i != 0)
-				i_tot1 += li_entry->dccplih_interval * dccp_li_hist_w[i - 1];
-		}
-
-
-		if (++i > DCCP_LI_HIST_IVAL_F_LENGTH)
-			break;
-	}
-
-	if (i != DCCP_LI_HIST_IVAL_F_LENGTH)
-		return 0;
-
-	i_tot = max(i_tot0, i_tot1);
-
-	if (!w_tot) {
-		DCCP_WARN("w_tot = 0\n");
-		return 1;
-	}
-
-	return i_tot / w_tot;
+	if (lh->ring[LIH_INDEX(lh->counter)] == NULL)
+		lh->ring[LIH_INDEX(lh->counter)] = kmem_cache_alloc(tfrc_lh_slab,
+								    GFP_ATOMIC);
+	return lh->ring[LIH_INDEX(lh->counter)];
 }
 
-EXPORT_SYMBOL_GPL(dccp_li_hist_calc_i_mean);
-
-static int dccp_li_hist_interval_new(struct list_head *list,
-				     const u64 seq_loss, const u8 win_loss)
+void tfrc_lh_cleanup(struct tfrc_loss_hist *lh)
 {
-	struct dccp_li_hist_entry *entry;
-	int i;
-
-	for (i = 0; i < DCCP_LI_HIST_IVAL_F_LENGTH; i++) {
-		entry = dccp_li_hist_entry_new(GFP_ATOMIC);
-		if (entry == NULL) {
-			dccp_li_hist_purge(list);
-			DCCP_BUG("loss interval list entry is NULL");
-			return 0;
+	if (!tfrc_lh_is_initialised(lh))
+		return;
+
+	for (lh->counter = 0; lh->counter < LIH_SIZE; lh->counter++)
+		if (lh->ring[LIH_INDEX(lh->counter)] != NULL) {
+			kmem_cache_free(tfrc_lh_slab,
+					lh->ring[LIH_INDEX(lh->counter)]);
+			lh->ring[LIH_INDEX(lh->counter)] = NULL;
 		}
-		entry->dccplih_interval = ~0;
-		list_add(&entry->dccplih_node, list);
-	}
-
-	entry->dccplih_seqno     = seq_loss;
-	entry->dccplih_win_count = win_loss;
-	return 1;
 }
+EXPORT_SYMBOL_GPL(tfrc_lh_cleanup);
 
-/* calculate first loss interval
- *
- * returns estimated loss interval in usecs */
-static u32 dccp_li_calc_first_li(struct sock *sk,
-				 struct list_head *hist_list,
-				 ktime_t last_feedback,
-				 u16 s, u32 bytes_recv,
-				 u32 previous_x_recv)
+static void tfrc_lh_calc_i_mean(struct tfrc_loss_hist *lh)
 {
-	struct dccp_rx_hist_entry *entry, *next, *tail = NULL;
-	u32 x_recv, p;
-	suseconds_t rtt, delta;
-	ktime_t tstamp = ktime_set(0, 0);
-	int interval = 0;
-	int win_count = 0;
-	int step = 0;
-	u64 fval;
+	u32 i_i, i_tot0 = 0, i_tot1 = 0, w_tot = 0;
+	int i, k = tfrc_lh_length(lh) - 1; /* k is as in rfc3448bis, 5.4 */
 
-	list_for_each_entry_safe(entry, next, hist_list, dccphrx_node) {
-		if (dccp_rx_hist_entry_data_packet(entry)) {
-			tail = entry;
+	for (i=0; i <= k; i++) {
+		i_i = tfrc_lh_get_interval(lh, i);
 
-			switch (step) {
-			case 0:
-				tstamp	  = entry->dccphrx_tstamp;
-				win_count = entry->dccphrx_ccval;
-				step = 1;
-				break;
-			case 1:
-				interval = win_count - entry->dccphrx_ccval;
-				if (interval < 0)
-					interval += TFRC_WIN_COUNT_LIMIT;
-				if (interval > 4)
-					goto found;
-				break;
-			}
+		if (i < k) {
+			i_tot0 += i_i * tfrc_lh_weights[i];
+			w_tot  += tfrc_lh_weights[i];
 		}
+		if (i > 0)
+			i_tot1 += i_i * tfrc_lh_weights[i-1];
 	}
 
-	if (unlikely(step == 0)) {
-		DCCP_WARN("%s(%p), packet history has no data packets!\n",
-			  dccp_role(sk), sk);
-		return ~0;
-	}
-
-	if (unlikely(interval == 0)) {
-		DCCP_WARN("%s(%p), Could not find a win_count interval > 0. "
-			  "Defaulting to 1\n", dccp_role(sk), sk);
-		interval = 1;
-	}
-found:
-	if (!tail) {
-		DCCP_CRIT("tail is null\n");
-		return ~0;
-	}
-
-	delta = ktime_us_delta(tstamp, tail->dccphrx_tstamp);
-	DCCP_BUG_ON(delta < 0);
+	BUG_ON(w_tot == 0);
+	lh->i_mean = max(i_tot0, i_tot1) / w_tot;
+}
 
-	rtt = delta * 4 / interval;
-	dccp_pr_debug("%s(%p), approximated RTT to %dus\n",
-		      dccp_role(sk), sk, (int)rtt);
+/**
+ * tfrc_lh_update_i_mean  -  Update the `open' loss interval I_0
+ * For recomputing p: returns `true' if p > p_prev  <=>  1/p < 1/p_prev
+ */
+u8 tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *skb)
+{
+	struct tfrc_loss_interval *cur = tfrc_lh_peek(lh);
+	u32 old_i_mean = lh->i_mean;
+	s64 length;
 
-	/*
-	 * Determine the length of the first loss interval via inverse lookup.
-	 * Assume that X_recv can be computed by the throughput equation
-	 *		    s
-	 *	X_recv = --------
-	 *		 R * fval
-	 * Find some p such that f(p) = fval; return 1/p [RFC 3448, 6.3.1].
-	 */
-	if (rtt == 0) {			/* would result in divide-by-zero */
-		DCCP_WARN("RTT==0\n");
-		return ~0;
-	}
+	if (cur == NULL)			/* not initialised */
+		return 0;
 
-	delta = ktime_us_delta(ktime_get_real(), last_feedback);
-	DCCP_BUG_ON(delta <= 0);
+	length = dccp_delta_seqno(cur->li_seqno, DCCP_SKB_CB(skb)->dccpd_seq);
 
-	x_recv = scaled_div32(bytes_recv, delta);
-	if (x_recv == 0) {		/* would also trigger divide-by-zero */
-		DCCP_WARN("X_recv==0\n");
-		if (previous_x_recv == 0) {
-			DCCP_BUG("stored value of X_recv is zero");
-			return ~0;
-		}
-		x_recv = previous_x_recv;
-	}
+	if (length - cur->li_length <= 0)	/* duplicate or reordered */
+		return 0;
 
-	fval = scaled_div(s, rtt);
-	fval = scaled_div32(fval, x_recv);
-	p = tfrc_calc_x_reverse_lookup(fval);
+	if (SUB16(dccp_hdr(skb)->dccph_ccval, cur->li_ccval) > 4)
+		/*
+		 * Implements RFC 4342, 10.2:
+		 * If a packet S (skb) exists whose seqno comes `after' the one
+		 * starting the current loss interval (cur) and if the modulo-16
+		 * distance from C(cur) to C(S) is greater than 4, consider all
+		 * subsequent packets as belonging to a new loss interval. This
+		 * test is necessary since CCVal may wrap between intervals.
+		 */
+		cur->li_is_closed = 1;
+
+	if (tfrc_lh_length(lh) == 1)		/* due to RFC 3448, 6.3.1 */
+		return 0;
 
-	dccp_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
-		      "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
+	cur->li_length = length;
+	tfrc_lh_calc_i_mean(lh);
 
-	if (p == 0)
-		return ~0;
-	else
-		return 1000000 / p;
+	return (lh->i_mean < old_i_mean);
 }
+EXPORT_SYMBOL_GPL(tfrc_lh_update_i_mean);
 
-void dccp_li_update_li(struct sock *sk,
-		       struct list_head *li_hist_list,
-		       struct list_head *hist_list,
-		       ktime_t last_feedback, u16 s, u32 bytes_recv,
-		       u32 previous_x_recv, u64 seq_loss, u8 win_loss)
+/* Determine if `new_loss' does begin a new loss interval [RFC 4342, 10.2] */
+static inline u8 tfrc_lh_is_new_loss(struct tfrc_loss_interval *cur,
+				     struct tfrc_rx_hist_entry *new_loss)
 {
-	struct dccp_li_hist_entry *head;
-	u64 seq_temp;
-
-	if (list_empty(li_hist_list)) {
-		if (!dccp_li_hist_interval_new(li_hist_list, seq_loss,
-					       win_loss))
-			return;
-
-		head = list_entry(li_hist_list->next, struct dccp_li_hist_entry,
-				  dccplih_node);
-		head->dccplih_interval = dccp_li_calc_first_li(sk, hist_list,
-							       last_feedback,
-							       s, bytes_recv,
-							       previous_x_recv);
-	} else {
-		struct dccp_li_hist_entry *entry;
-		struct list_head *tail;
+	return	dccp_delta_seqno(cur->li_seqno, new_loss->tfrchrx_seqno) > 0 &&
+		(cur->li_is_closed || SUB16(new_loss->tfrchrx_ccval, cur->li_ccval) > 4);
+}
 
-		head = list_entry(li_hist_list->next, struct dccp_li_hist_entry,
-				  dccplih_node);
-		/* FIXME win count check removed as was wrong */
-		/* should make this check with receive history */
-		/* and compare there as per section 10.2 of RFC4342 */
+/** tfrc_lh_interval_add  -  Insert new record into the Loss Interval database
+ * @lh:		   Loss Interval database
+ * @rh:		   Receive history containing a fresh loss event
+ * @calc_first_li: Caller-dependent routine to compute length of first interval
+ * @sk:		   Used by @calc_first_li in caller-specific way (subtyping)
+ * Updates I_mean and returns 1 if a new interval has in fact been added to @lh.
+ */
+int tfrc_lh_interval_add(struct tfrc_loss_hist *lh, struct tfrc_rx_hist *rh,
+			 u32 (*calc_first_li)(struct sock *), struct sock *sk)
+{
+	struct tfrc_loss_interval *cur = tfrc_lh_peek(lh), *new;
 
-		/* new loss event detected */
-		/* calculate last interval length */
-		seq_temp = dccp_delta_seqno(head->dccplih_seqno, seq_loss);
-		entry = dccp_li_hist_entry_new(GFP_ATOMIC);
+	if (cur != NULL && !tfrc_lh_is_new_loss(cur, tfrc_rx_hist_loss_prev(rh)))
+		return 0;
 
-		if (entry == NULL) {
-			DCCP_BUG("out of memory - can not allocate entry");
-			return;
-		}
+	new = tfrc_lh_demand_next(lh);
+	if (unlikely(new == NULL)) {
+		DCCP_CRIT("Cannot allocate/add loss record.");
+		return 0;
+	}
 
-		list_add(&entry->dccplih_node, li_hist_list);
+	new->li_seqno	  = tfrc_rx_hist_loss_prev(rh)->tfrchrx_seqno;
+	new->li_ccval	  = tfrc_rx_hist_loss_prev(rh)->tfrchrx_ccval;
+	new->li_is_closed = 0;
 
-		tail = li_hist_list->prev;
-		list_del(tail);
-		kmem_cache_free(dccp_li_cachep, tail);
+	if (++lh->counter == 1)
+		lh->i_mean = new->li_length = (*calc_first_li)(sk);
+	else {
+		cur->li_length = dccp_delta_seqno(cur->li_seqno, new->li_seqno);
+		new->li_length = dccp_delta_seqno(new->li_seqno,
+				  tfrc_rx_hist_last_rcv(rh)->tfrchrx_seqno);
+		if (lh->counter > (2*LIH_SIZE))
+			lh->counter -= LIH_SIZE;
 
-		/* Create the newest interval */
-		entry->dccplih_seqno = seq_loss;
-		entry->dccplih_interval = seq_temp;
-		entry->dccplih_win_count = win_loss;
+		tfrc_lh_calc_i_mean(lh);
 	}
+	return 1;
 }
+EXPORT_SYMBOL_GPL(tfrc_lh_interval_add);
 
-EXPORT_SYMBOL_GPL(dccp_li_update_li);
-
-static __init int dccp_li_init(void)
+int __init tfrc_li_init(void)
 {
-	dccp_li_cachep = kmem_cache_create("dccp_li_hist",
-					   sizeof(struct dccp_li_hist_entry),
-					   0, SLAB_HWCACHE_ALIGN, NULL);
-	return dccp_li_cachep == NULL ? -ENOBUFS : 0;
+	tfrc_lh_slab = kmem_cache_create("tfrc_li_hist",
+					 sizeof(struct tfrc_loss_interval), 0,
+					 SLAB_HWCACHE_ALIGN, NULL);
+	return tfrc_lh_slab == NULL ? -ENOBUFS : 0;
 }
 
-static __exit void dccp_li_exit(void)
+void tfrc_li_exit(void)
 {
-	kmem_cache_destroy(dccp_li_cachep);
+	if (tfrc_lh_slab != NULL) {
+		kmem_cache_destroy(tfrc_lh_slab);
+		tfrc_lh_slab = NULL;
+	}
 }
-
-module_init(dccp_li_init);
-module_exit(dccp_li_exit);
diff --git a/net/dccp/ccids/lib/loss_interval.h b/net/dccp/ccids/lib/loss_interval.h
index 27bee92dae1..246018a3b26 100644
--- a/net/dccp/ccids/lib/loss_interval.h
+++ b/net/dccp/ccids/lib/loss_interval.h
@@ -3,6 +3,7 @@
 /*
  *  net/dccp/ccids/lib/loss_interval.h
  *
+ *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
  *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
  *  Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
@@ -12,18 +13,63 @@
  *  Software Foundation; either version 2 of the License, or (at your option)
  *  any later version.
  */
-
 #include <linux/ktime.h>
 #include <linux/list.h>
+#include <linux/slab.h>
+
+/*
+ * Number of loss intervals (RFC 4342, 8.6.1). The history size is one more than
+ * NINTERVAL, since the `open' interval I_0 is always stored as the first entry.
+ */
+#define NINTERVAL	8
+#define LIH_SIZE	(NINTERVAL + 1)
+
+/**
+ *  tfrc_loss_interval  -  Loss history record for TFRC-based protocols
+ *  @li_seqno:		Highest received seqno before the start of loss
+ *  @li_ccval:		The CCVal belonging to @li_seqno
+ *  @li_is_closed:	Whether @li_seqno is older than 1 RTT
+ *  @li_length:		Loss interval sequence length
+ */
+struct tfrc_loss_interval {
+	u64		 li_seqno:48,
+			 li_ccval:4,
+			 li_is_closed:1;
+	u32		 li_length;
+};
+
+/**
+ *  tfrc_loss_hist  -  Loss record database
+ *  @ring:	Circular queue managed in LIFO manner
+ *  @counter:	Current count of entries (can be more than %LIH_SIZE)
+ *  @i_mean:	Current Average Loss Interval [RFC 3448, 5.4]
+ */
+struct tfrc_loss_hist {
+	struct tfrc_loss_interval	*ring[LIH_SIZE];
+	u8				counter;
+	u32				i_mean;
+};
+
+static inline void tfrc_lh_init(struct tfrc_loss_hist *lh)
+{
+	memset(lh, 0, sizeof(struct tfrc_loss_hist));
+}
+
+static inline u8 tfrc_lh_is_initialised(struct tfrc_loss_hist *lh)
+{
+	return lh->counter > 0;
+}
+
+static inline u8 tfrc_lh_length(struct tfrc_loss_hist *lh)
+{
+	return min(lh->counter, (u8)LIH_SIZE);
+}
 
-extern void dccp_li_hist_purge(struct list_head *list);
+struct tfrc_rx_hist;
 
-extern u32 dccp_li_hist_calc_i_mean(struct list_head *list);
+extern int  tfrc_lh_interval_add(struct tfrc_loss_hist *, struct tfrc_rx_hist *,
+				 u32 (*first_li)(struct sock *), struct sock *);
+extern u8   tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *);
+extern void tfrc_lh_cleanup(struct tfrc_loss_hist *lh);
 
-extern void dccp_li_update_li(struct sock *sk,
-			      struct list_head *li_hist_list,
-			      struct list_head *hist_list,
-			      ktime_t last_feedback, u16 s,
-			      u32 bytes_recv, u32 previous_x_recv,
-			      u64 seq_loss, u8 win_loss);
 #endif /* _DCCP_LI_HIST_ */
diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c
index 34c4f604772..20af1a69342 100644
--- a/net/dccp/ccids/lib/packet_history.c
+++ b/net/dccp/ccids/lib/packet_history.c
@@ -1,7 +1,8 @@
 /*
  *  net/dccp/packet_history.c
  *
- *  Copyright (c) 2005-6 The University of Waikato, Hamilton, New Zealand.
+ *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
+ *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
  *
  *  An implementation of the DCCP protocol
  *
@@ -34,267 +35,465 @@
  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
-#include <linux/module.h>
 #include <linux/string.h>
+#include <linux/slab.h>
 #include "packet_history.h"
+#include "../../dccp.h"
+
+/**
+ *  tfrc_tx_hist_entry  -  Simple singly-linked TX history list
+ *  @next:  next oldest entry (LIFO order)
+ *  @seqno: sequence number of this entry
+ *  @stamp: send time of packet with sequence number @seqno
+ */
+struct tfrc_tx_hist_entry {
+	struct tfrc_tx_hist_entry *next;
+	u64			  seqno;
+	ktime_t			  stamp;
+};
 
 /*
- * 	Transmitter History Routines
+ * Transmitter History Routines
  */
-struct dccp_tx_hist *dccp_tx_hist_new(const char *name)
+static struct kmem_cache *tfrc_tx_hist_slab;
+
+int __init tfrc_tx_packet_history_init(void)
 {
-	struct dccp_tx_hist *hist = kmalloc(sizeof(*hist), GFP_ATOMIC);
-	static const char dccp_tx_hist_mask[] = "tx_hist_%s";
-	char *slab_name;
-
-	if (hist == NULL)
-		goto out;
-
-	slab_name = kmalloc(strlen(name) + sizeof(dccp_tx_hist_mask) - 1,
-			    GFP_ATOMIC);
-	if (slab_name == NULL)
-		goto out_free_hist;
-
-	sprintf(slab_name, dccp_tx_hist_mask, name);
-	hist->dccptxh_slab = kmem_cache_create(slab_name,
-					     sizeof(struct dccp_tx_hist_entry),
-					       0, SLAB_HWCACHE_ALIGN,
-					       NULL);
-	if (hist->dccptxh_slab == NULL)
-		goto out_free_slab_name;
-out:
-	return hist;
-out_free_slab_name:
-	kfree(slab_name);
-out_free_hist:
-	kfree(hist);
-	hist = NULL;
-	goto out;
+	tfrc_tx_hist_slab = kmem_cache_create("tfrc_tx_hist",
+					      sizeof(struct tfrc_tx_hist_entry),
+					      0, SLAB_HWCACHE_ALIGN, NULL);
+	return tfrc_tx_hist_slab == NULL ? -ENOBUFS : 0;
 }
 
-EXPORT_SYMBOL_GPL(dccp_tx_hist_new);
-
-void dccp_tx_hist_delete(struct dccp_tx_hist *hist)
+void tfrc_tx_packet_history_exit(void)
 {
-	const char* name = kmem_cache_name(hist->dccptxh_slab);
-
-	kmem_cache_destroy(hist->dccptxh_slab);
-	kfree(name);
-	kfree(hist);
+	if (tfrc_tx_hist_slab != NULL) {
+		kmem_cache_destroy(tfrc_tx_hist_slab);
+		tfrc_tx_hist_slab = NULL;
+	}
 }
 
-EXPORT_SYMBOL_GPL(dccp_tx_hist_delete);
-
-struct dccp_tx_hist_entry *
-	dccp_tx_hist_find_entry(const struct list_head *list, const u64 seq)
+static struct tfrc_tx_hist_entry *
+	tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
 {
-	struct dccp_tx_hist_entry *packet = NULL, *entry;
-
-	list_for_each_entry(entry, list, dccphtx_node)
-		if (entry->dccphtx_seqno == seq) {
-			packet = entry;
-			break;
-		}
+	while (head != NULL && head->seqno != seqno)
+		head = head->next;
 
-	return packet;
+	return head;
 }
 
-EXPORT_SYMBOL_GPL(dccp_tx_hist_find_entry);
+int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
+{
+	struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());
+
+	if (entry == NULL)
+		return -ENOBUFS;
+	entry->seqno = seqno;
+	entry->stamp = ktime_get_real();
+	entry->next  = *headp;
+	*headp	     = entry;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tfrc_tx_hist_add);
 
-void dccp_tx_hist_purge(struct dccp_tx_hist *hist, struct list_head *list)
+void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
 {
-	struct dccp_tx_hist_entry *entry, *next;
+	struct tfrc_tx_hist_entry *head = *headp;
+
+	while (head != NULL) {
+		struct tfrc_tx_hist_entry *next = head->next;
 
-	list_for_each_entry_safe(entry, next, list, dccphtx_node) {
-		list_del_init(&entry->dccphtx_node);
-		dccp_tx_hist_entry_delete(hist, entry);
+		kmem_cache_free(tfrc_tx_hist_slab, head);
+		head = next;
 	}
-}
 
-EXPORT_SYMBOL_GPL(dccp_tx_hist_purge);
+	*headp = NULL;
+}
+EXPORT_SYMBOL_GPL(tfrc_tx_hist_purge);
 
-void dccp_tx_hist_purge_older(struct dccp_tx_hist *hist,
-			      struct list_head *list,
-			      struct dccp_tx_hist_entry *packet)
+u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno,
+		     const ktime_t now)
 {
-	struct dccp_tx_hist_entry *next;
+	u32 rtt = 0;
+	struct tfrc_tx_hist_entry *packet = tfrc_tx_hist_find_entry(head, seqno);
 
-	list_for_each_entry_safe_continue(packet, next, list, dccphtx_node) {
-		list_del_init(&packet->dccphtx_node);
-		dccp_tx_hist_entry_delete(hist, packet);
+	if (packet != NULL) {
+		rtt = ktime_us_delta(now, packet->stamp);
+		/*
+		 * Garbage-collect older (irrelevant) entries:
+		 */
+		tfrc_tx_hist_purge(&packet->next);
 	}
+
+	return rtt;
 }
+EXPORT_SYMBOL_GPL(tfrc_tx_hist_rtt);
 
-EXPORT_SYMBOL_GPL(dccp_tx_hist_purge_older);
 
 /*
  * 	Receiver History Routines
  */
-struct dccp_rx_hist *dccp_rx_hist_new(const char *name)
+static struct kmem_cache *tfrc_rx_hist_slab;
+
+int __init tfrc_rx_packet_history_init(void)
 {
-	struct dccp_rx_hist *hist = kmalloc(sizeof(*hist), GFP_ATOMIC);
-	static const char dccp_rx_hist_mask[] = "rx_hist_%s";
-	char *slab_name;
-
-	if (hist == NULL)
-		goto out;
-
-	slab_name = kmalloc(strlen(name) + sizeof(dccp_rx_hist_mask) - 1,
-			    GFP_ATOMIC);
-	if (slab_name == NULL)
-		goto out_free_hist;
-
-	sprintf(slab_name, dccp_rx_hist_mask, name);
-	hist->dccprxh_slab = kmem_cache_create(slab_name,
-					     sizeof(struct dccp_rx_hist_entry),
-					       0, SLAB_HWCACHE_ALIGN,
-					       NULL);
-	if (hist->dccprxh_slab == NULL)
-		goto out_free_slab_name;
-out:
-	return hist;
-out_free_slab_name:
-	kfree(slab_name);
-out_free_hist:
-	kfree(hist);
-	hist = NULL;
-	goto out;
+	tfrc_rx_hist_slab = kmem_cache_create("tfrc_rxh_cache",
+					      sizeof(struct tfrc_rx_hist_entry),
+					      0, SLAB_HWCACHE_ALIGN, NULL);
+	return tfrc_rx_hist_slab == NULL ? -ENOBUFS : 0;
 }
 
-EXPORT_SYMBOL_GPL(dccp_rx_hist_new);
+void tfrc_rx_packet_history_exit(void)
+{
+	if (tfrc_rx_hist_slab != NULL) {
+		kmem_cache_destroy(tfrc_rx_hist_slab);
+		tfrc_rx_hist_slab = NULL;
+	}
+}
 
-void dccp_rx_hist_delete(struct dccp_rx_hist *hist)
+static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry,
+					       const struct sk_buff *skb,
+					       const u32 ndp)
 {
-	const char* name = kmem_cache_name(hist->dccprxh_slab);
+	const struct dccp_hdr *dh = dccp_hdr(skb);
 
-	kmem_cache_destroy(hist->dccprxh_slab);
-	kfree(name);
-	kfree(hist);
+	entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
+	entry->tfrchrx_ccval = dh->dccph_ccval;
+	entry->tfrchrx_type  = dh->dccph_type;
+	entry->tfrchrx_ndp   = ndp;
+	entry->tfrchrx_tstamp = ktime_get_real();
 }
 
-EXPORT_SYMBOL_GPL(dccp_rx_hist_delete);
+void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
+			     const struct sk_buff *skb,
+			     const u32 ndp)
+{
+	struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h);
+
+	tfrc_rx_hist_entry_from_skb(entry, skb, ndp);
+}
+EXPORT_SYMBOL_GPL(tfrc_rx_hist_add_packet);
 
-int dccp_rx_hist_find_entry(const struct list_head *list, const u64 seq,
-			    u8 *ccval)
+/* has the packet contained in skb been seen before? */
+int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb)
 {
-	struct dccp_rx_hist_entry *packet = NULL, *entry;
+	const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq;
+	int i;
 
-	list_for_each_entry(entry, list, dccphrx_node)
-		if (entry->dccphrx_seqno == seq) {
-			packet = entry;
-			break;
-		}
+	if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0)
+		return 1;
 
-	if (packet)
-		*ccval = packet->dccphrx_ccval;
+	for (i = 1; i <= h->loss_count; i++)
+		if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq)
+			return 1;
 
-	return packet != NULL;
+	return 0;
 }
+EXPORT_SYMBOL_GPL(tfrc_rx_hist_duplicate);
 
-EXPORT_SYMBOL_GPL(dccp_rx_hist_find_entry);
-struct dccp_rx_hist_entry *
-		dccp_rx_hist_find_data_packet(const struct list_head *list)
+static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
 {
-	struct dccp_rx_hist_entry *entry, *packet = NULL;
-
-	list_for_each_entry(entry, list, dccphrx_node)
-		if (entry->dccphrx_type == DCCP_PKT_DATA ||
-		    entry->dccphrx_type == DCCP_PKT_DATAACK) {
-			packet = entry;
-			break;
-		}
+	const u8 idx_a = tfrc_rx_hist_index(h, a),
+		 idx_b = tfrc_rx_hist_index(h, b);
+	struct tfrc_rx_hist_entry *tmp = h->ring[idx_a];
 
-	return packet;
+	h->ring[idx_a] = h->ring[idx_b];
+	h->ring[idx_b] = tmp;
 }
 
-EXPORT_SYMBOL_GPL(dccp_rx_hist_find_data_packet);
+/*
+ * Private helper functions for loss detection.
+ *
+ * In the descriptions, `Si' refers to the sequence number of entry number i,
+ * whose NDP count is `Ni' (lower case is used for variables).
+ * Note: All __after_loss functions expect that a test against duplicates has
+ *       been performed already: the seqno of the skb must not be less than the
+ *       seqno of loss_prev; and it must not equal that of any valid hist_entry.
+ */
+static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
+{
+	u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
+	    s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
+	    s2 = DCCP_SKB_CB(skb)->dccpd_seq;
+	int n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp,
+	   d12 = dccp_delta_seqno(s1, s2), d2;
+
+	if (d12 > 0) {			/* S1  <  S2 */
+		h->loss_count = 2;
+		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2);
+		return;
+	}
+
+	/* S0  <  S2  <  S1 */
+	d2 = dccp_delta_seqno(s0, s2);
 
-void dccp_rx_hist_add_packet(struct dccp_rx_hist *hist,
-			    struct list_head *rx_list,
-			    struct list_head *li_list,
-			    struct dccp_rx_hist_entry *packet,
-			    u64 nonloss_seqno)
+	if (d2 == 1 || n2 >= d2) {	/* S2 is direct successor of S0 */
+		int d21 = -d12;
+
+		if (d21 == 1 || n1 >= d21) {
+			/* hole is filled: S0, S2, and S1 are consecutive */
+			h->loss_count = 0;
+			h->loss_start = tfrc_rx_hist_index(h, 1);
+		} else
+			/* gap between S2 and S1: just update loss_prev */
+			tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2);
+
+	} else {			/* hole between S0 and S2 */
+		/*
+		 * Reorder history to insert S2 between S0 and s1
+		 */
+		tfrc_rx_hist_swap(h, 0, 3);
+		h->loss_start = tfrc_rx_hist_index(h, 3);
+		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n2);
+		h->loss_count = 2;
+	}
+}
+
+/* return 1 if a new loss event has been identified */
+static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
 {
-	struct dccp_rx_hist_entry *entry, *next;
-	u8 num_later = 0;
-
-	list_add(&packet->dccphrx_node, rx_list);
-
-	num_later = TFRC_RECV_NUM_LATE_LOSS + 1;
-
-	if (!list_empty(li_list)) {
-		list_for_each_entry_safe(entry, next, rx_list, dccphrx_node) {
-			if (num_later == 0) {
-				if (after48(nonloss_seqno,
-				   entry->dccphrx_seqno)) {
-					list_del_init(&entry->dccphrx_node);
-					dccp_rx_hist_entry_delete(hist, entry);
-				}
-			} else if (dccp_rx_hist_entry_data_packet(entry))
-				--num_later;
-		}
-	} else {
-		int step = 0;
-		u8 win_count = 0; /* Not needed, but lets shut up gcc */
-		int tmp;
+	u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
+	    s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
+	    s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
+	    s3 = DCCP_SKB_CB(skb)->dccpd_seq;
+	int n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp,
+	   d23 = dccp_delta_seqno(s2, s3), d13, d3, d31;
+
+	if (d23 > 0) {			/* S2  <  S3 */
+		h->loss_count = 3;
+		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3);
+		return 1;
+	}
+
+	/* S3  <  S2 */
+	d13 = dccp_delta_seqno(s1, s3);
+
+	if (d13 > 0) {
 		/*
-		 * We have no loss interval history so we need at least one
-		 * rtt:s of data packets to approximate rtt.
+		 * The sequence number order is S1, S3, S2
+		 * Reorder history to insert entry between S1 and S2
 		 */
-		list_for_each_entry_safe(entry, next, rx_list, dccphrx_node) {
-			if (num_later == 0) {
-				switch (step) {
-				case 0:
-					step = 1;
-					/* OK, find next data packet */
-					num_later = 1;
-					break;
-				case 1:
-					step = 2;
-					/* OK, find next data packet */
-					num_later = 1;
-					win_count = entry->dccphrx_ccval;
-					break;
-				case 2:
-					tmp = win_count - entry->dccphrx_ccval;
-					if (tmp < 0)
-						tmp += TFRC_WIN_COUNT_LIMIT;
-					if (tmp > TFRC_WIN_COUNT_PER_RTT + 1) {
-						/*
-						 * We have found a packet older
-						 * than one rtt remove the rest
-						 */
-						step = 3;
-					} else /* OK, find next data packet */
-						num_later = 1;
-					break;
-				case 3:
-					list_del_init(&entry->dccphrx_node);
-					dccp_rx_hist_entry_delete(hist, entry);
-					break;
-				}
-			} else if (dccp_rx_hist_entry_data_packet(entry))
-				--num_later;
+		tfrc_rx_hist_swap(h, 2, 3);
+		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3);
+		h->loss_count = 3;
+		return 1;
+	}
+
+	/* S0  <  S3  <  S1 */
+	d31 = -d13;
+	d3  = dccp_delta_seqno(s0, s3);
+
+	if (d3 == 1 || n3 >= d3) {	/* S3 is a successor of S0 */
+
+		if (d31 == 1 || n1 >= d31) {
+			/* hole between S0 and S1 filled by S3 */
+			int  d2 = dccp_delta_seqno(s1, s2),
+			     n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp;
+
+			if (d2 == 1 || n2 >= d2) {
+				/* entire hole filled by S0, S3, S1, S2 */
+				h->loss_start = tfrc_rx_hist_index(h, 2);
+				h->loss_count = 0;
+			} else {
+				/* gap remains between S1 and S2 */
+				h->loss_start = tfrc_rx_hist_index(h, 1);
+				h->loss_count = 1;
+			}
+
+		} else /* gap exists between S3 and S1, loss_count stays at 2 */
+			tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n3);
+
+		return 0;
+	}
+
+	/*
+	 * The remaining case: S3 is not a successor of S0.
+	 * Sequence order is S0, S3, S1, S2; reorder to insert between S0 and S1
+	 */
+	tfrc_rx_hist_swap(h, 0, 3);
+	h->loss_start = tfrc_rx_hist_index(h, 3);
+	tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n3);
+	h->loss_count = 3;
+
+	return 1;
+}
+
+/* return the signed modulo-2^48 sequence number distance from entry e1 to e2 */
+static s64 tfrc_rx_hist_delta_seqno(struct tfrc_rx_hist *h, u8 e1, u8 e2)
+{
+	DCCP_BUG_ON(e1 > h->loss_count || e2 > h->loss_count);
+
+	return dccp_delta_seqno(tfrc_rx_hist_entry(h, e1)->tfrchrx_seqno,
+				tfrc_rx_hist_entry(h, e2)->tfrchrx_seqno);
+}
+
+/* recycle RX history records to continue loss detection if necessary */
+static void __three_after_loss(struct tfrc_rx_hist *h)
+{
+	/*
+	 * The distance between S0 and S1 is always greater than 1 and the NDP
+	 * count of S1 is smaller than this distance. Otherwise there would
+	 * have been no loss. Hence it is only necessary to see whether there
+	 * are further missing data packets between S1/S2 and S2/S3.
+	 */
+	int d2 = tfrc_rx_hist_delta_seqno(h, 1, 2),
+	    d3 = tfrc_rx_hist_delta_seqno(h, 2, 3),
+	    n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp,
+	    n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp;
+
+	if (d2 == 1 || n2 >= d2) {	/* S2 is successor to S1 */
+
+		if (d3 == 1 || n3 >= d3) {
+			/* S3 is successor of S2: entire hole is filled */
+			h->loss_start = tfrc_rx_hist_index(h, 3);
+			h->loss_count = 0;
+		} else {
+			/* gap between S2 and S3 */
+			h->loss_start = tfrc_rx_hist_index(h, 2);
+			h->loss_count = 1;
 		}
+
+	} else {			/* gap between S1 and S2 */
+		h->loss_start = tfrc_rx_hist_index(h, 1);
+		h->loss_count = 2;
 	}
 }
 
-EXPORT_SYMBOL_GPL(dccp_rx_hist_add_packet);
+/**
+ *  tfrc_rx_handle_loss  -  Loss detection and further processing
+ *  @h:		    The non-empty RX history object
+ *  @lh:	    Loss Intervals database to update
+ *  @skb:	    Currently received packet
+ *  @ndp:	    The NDP count belonging to @skb
+ *  @calc_first_li: Caller-dependent computation of first loss interval in @lh
+ *  @sk:	    Used by @calc_first_li (see tfrc_lh_interval_add)
+ *  Chooses action according to pending loss, updates LI database when a new
+ *  loss was detected, and does required post-processing. Returns 1 when caller
+ *  should send feedback, 0 otherwise.
+ */
+int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
+			struct tfrc_loss_hist *lh,
+			struct sk_buff *skb, u32 ndp,
+			u32 (*calc_first_li)(struct sock *), struct sock *sk)
+{
+	int is_new_loss = 0;
 
-void dccp_rx_hist_purge(struct dccp_rx_hist *hist, struct list_head *list)
+	if (h->loss_count == 1) {
+		__one_after_loss(h, skb, ndp);
+	} else if (h->loss_count != 2) {
+		DCCP_BUG("invalid loss_count %d", h->loss_count);
+	} else if (__two_after_loss(h, skb, ndp)) {
+		/*
+		 * Update Loss Interval database and recycle RX records
+		 */
+		is_new_loss = tfrc_lh_interval_add(lh, h, calc_first_li, sk);
+		__three_after_loss(h);
+	}
+	return is_new_loss;
+}
+EXPORT_SYMBOL_GPL(tfrc_rx_handle_loss);
+
+int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
 {
-	struct dccp_rx_hist_entry *entry, *next;
+	int i;
+
+	for (i = 0; i <= TFRC_NDUPACK; i++) {
+		h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
+		if (h->ring[i] == NULL)
+			goto out_free;
+	}
+
+	h->loss_count = h->loss_start = 0;
+	return 0;
 
-	list_for_each_entry_safe(entry, next, list, dccphrx_node) {
-		list_del_init(&entry->dccphrx_node);
-		kmem_cache_free(hist->dccprxh_slab, entry);
+out_free:
+	while (i-- != 0) {
+		kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
+		h->ring[i] = NULL;
 	}
+	return -ENOBUFS;
 }
+EXPORT_SYMBOL_GPL(tfrc_rx_hist_alloc);
+
+void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
+{
+	int i;
 
-EXPORT_SYMBOL_GPL(dccp_rx_hist_purge);
+	for (i = 0; i <= TFRC_NDUPACK; ++i)
+		if (h->ring[i] != NULL) {
+			kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
+			h->ring[i] = NULL;
+		}
+}
+EXPORT_SYMBOL_GPL(tfrc_rx_hist_purge);
 
+/**
+ * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
+ */
+static inline struct tfrc_rx_hist_entry *
+			tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
+{
+	return h->ring[0];
+}
 
-MODULE_AUTHOR("Ian McDonald <ian.mcdonald@jandi.co.nz>, "
-	      "Arnaldo Carvalho de Melo <acme@ghostprotocols.net>");
-MODULE_DESCRIPTION("DCCP TFRC library");
-MODULE_LICENSE("GPL");
+/**
+ * tfrc_rx_hist_rtt_prev_s: previously suitable (wrt rtt_last_s) RTT-sampling entry
+ */
+static inline struct tfrc_rx_hist_entry *
+			tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
+{
+	return h->ring[h->rtt_sample_prev];
+}
+
+/**
+ * tfrc_rx_hist_sample_rtt  -  Sample RTT from timestamp / CCVal
+ * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
+ * to compute a sample with given data - calling function should check this.
+ */
+u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
+{
+	u32 sample = 0,
+	    delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
+			    tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
+
+	if (delta_v < 1 || delta_v > 4) {	/* unsuitable CCVal delta */
+		if (h->rtt_sample_prev == 2) {	/* previous candidate stored */
+			sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
+				       tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
+			if (sample)
+				sample = 4 / sample *
+				         ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
+							tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
+			else    /*
+				 * FIXME: This condition is in principle not
+				 * possible but occurs when CCID is used for
+				 * two-way data traffic. I have tried to trace
+				 * it, but the cause does not seem to be here.
+				 */
+				DCCP_BUG("please report to dccp@vger.kernel.org"
+					 " => prev = %u, last = %u",
+					 tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
+					 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
+		} else if (delta_v < 1) {
+			h->rtt_sample_prev = 1;
+			goto keep_ref_for_next_time;
+		}
+
+	} else if (delta_v == 4) /* optimal match */
+		sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
+	else {			 /* suboptimal match */
+		h->rtt_sample_prev = 2;
+		goto keep_ref_for_next_time;
+	}
+
+	if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
+		DCCP_WARN("RTT sample %u too large, using max\n", sample);
+		sample = DCCP_SANE_RTT_MAX;
+	}
+
+	h->rtt_sample_prev = 0;	       /* use current entry as next reference */
+keep_ref_for_next_time:
+
+	return sample;
+}
+EXPORT_SYMBOL_GPL(tfrc_rx_hist_sample_rtt);
diff --git a/net/dccp/ccids/lib/packet_history.h b/net/dccp/ccids/lib/packet_history.h
index 032bb61c6e3..c7eeda49cb2 100644
--- a/net/dccp/ccids/lib/packet_history.h
+++ b/net/dccp/ccids/lib/packet_history.h
@@ -1,10 +1,9 @@
 /*
- *  net/dccp/packet_history.h
+ *  Packet RX/TX history data structures and routines for TFRC-based protocols.
  *
+ *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
  *  Copyright (c) 2005-6 The University of Waikato, Hamilton, New Zealand.
  *
- *  An implementation of the DCCP protocol
- *
  *  This code has been developed by the University of Waikato WAND
  *  research group. For further information please see http://www.wand.net.nz/
  *  or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
@@ -37,165 +36,128 @@
 #ifndef _DCCP_PKT_HIST_
 #define _DCCP_PKT_HIST_
 
-#include <linux/ktime.h>
 #include <linux/list.h>
 #include <linux/slab.h>
+#include "tfrc.h"
 
-#include "../../dccp.h"
+struct tfrc_tx_hist_entry;
 
-/* Number of later packets received before one is considered lost */
-#define TFRC_RECV_NUM_LATE_LOSS	 3
+extern int  tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno);
+extern void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp);
+extern u32  tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head,
+			     const u64 seqno, const ktime_t now);
 
-#define TFRC_WIN_COUNT_PER_RTT	 4
-#define TFRC_WIN_COUNT_LIMIT	16
+/* Subtraction a-b modulo-16, respects circular wrap-around */
+#define SUB16(a, b) (((a) + 16 - (b)) & 0xF)
 
-/*
- * 	Transmitter History data structures and declarations
+/* Number of packets to wait after a missing packet (RFC 4342, 6.1) */
+#define TFRC_NDUPACK 3
+
+/**
+ * tfrc_rx_hist_entry - Store information about a single received packet
+ * @tfrchrx_seqno:	DCCP packet sequence number
+ * @tfrchrx_ccval:	window counter value of packet (RFC 4342, 8.1)
+ * @tfrchrx_ndp:	the NDP count (if any) of the packet
+ * @tfrchrx_tstamp:	actual receive time of packet
  */
-struct dccp_tx_hist_entry {
-	struct list_head dccphtx_node;
-	u64		 dccphtx_seqno:48,
-			 dccphtx_sent:1;
-	u32		 dccphtx_rtt;
-	ktime_t		 dccphtx_tstamp;
+struct tfrc_rx_hist_entry {
+	u64		 tfrchrx_seqno:48,
+			 tfrchrx_ccval:4,
+			 tfrchrx_type:4;
+	u32		 tfrchrx_ndp; /* In fact it is from 8 to 24 bits */
+	ktime_t		 tfrchrx_tstamp;
 };
 
-struct dccp_tx_hist {
-	struct kmem_cache *dccptxh_slab;
+/**
+ * tfrc_rx_hist  -  RX history structure for TFRC-based protocols
+ *
+ * @ring:		Packet history for RTT sampling and loss detection
+ * @loss_count:		Number of entries in circular history
+ * @loss_start:		Movable index (for loss detection)
+ * @rtt_sample_prev:	Used during RTT sampling, points to candidate entry
+ */
+struct tfrc_rx_hist {
+	struct tfrc_rx_hist_entry *ring[TFRC_NDUPACK + 1];
+	u8			  loss_count:2,
+				  loss_start:2;
+#define rtt_sample_prev		  loss_start
 };
 
-extern struct dccp_tx_hist *dccp_tx_hist_new(const char *name);
-extern void 		    dccp_tx_hist_delete(struct dccp_tx_hist *hist);
-
-static inline struct dccp_tx_hist_entry *
-			dccp_tx_hist_entry_new(struct dccp_tx_hist *hist,
-					       const gfp_t prio)
+/**
+ * tfrc_rx_hist_index - index to reach n-th entry after loss_start
+ */
+static inline u8 tfrc_rx_hist_index(const struct tfrc_rx_hist *h, const u8 n)
 {
-	struct dccp_tx_hist_entry *entry = kmem_cache_alloc(hist->dccptxh_slab,
-							    prio);
-
-	if (entry != NULL)
-		entry->dccphtx_sent = 0;
-
-	return entry;
+	return (h->loss_start + n) & TFRC_NDUPACK;
 }
 
-static inline struct dccp_tx_hist_entry *
-			dccp_tx_hist_head(struct list_head *list)
+/**
+ * tfrc_rx_hist_last_rcv - entry with highest-received-seqno so far
+ */
+static inline struct tfrc_rx_hist_entry *
+			tfrc_rx_hist_last_rcv(const struct tfrc_rx_hist *h)
 {
-	struct dccp_tx_hist_entry *head = NULL;
-
-	if (!list_empty(list))
-		head = list_entry(list->next, struct dccp_tx_hist_entry,
-				  dccphtx_node);
-	return head;
+	return h->ring[tfrc_rx_hist_index(h, h->loss_count)];
 }
 
-extern struct dccp_tx_hist_entry *
-			dccp_tx_hist_find_entry(const struct list_head *list,
-						const u64 seq);
-
-static inline void dccp_tx_hist_add_entry(struct list_head *list,
-					  struct dccp_tx_hist_entry *entry)
+/**
+ * tfrc_rx_hist_entry - return the n-th history entry after loss_start
+ */
+static inline struct tfrc_rx_hist_entry *
+			tfrc_rx_hist_entry(const struct tfrc_rx_hist *h, const u8 n)
 {
-	list_add(&entry->dccphtx_node, list);
+	return h->ring[tfrc_rx_hist_index(h, n)];
 }
 
-static inline void dccp_tx_hist_entry_delete(struct dccp_tx_hist *hist,
-					     struct dccp_tx_hist_entry *entry)
+/**
+ * tfrc_rx_hist_loss_prev - entry with highest-received-seqno before loss was detected
+ */
+static inline struct tfrc_rx_hist_entry *
+			tfrc_rx_hist_loss_prev(const struct tfrc_rx_hist *h)
 {
-	if (entry != NULL)
-		kmem_cache_free(hist->dccptxh_slab, entry);
+	return h->ring[h->loss_start];
 }
 
-extern void dccp_tx_hist_purge(struct dccp_tx_hist *hist,
-			       struct list_head *list);
-
-extern void dccp_tx_hist_purge_older(struct dccp_tx_hist *hist,
-				     struct list_head *list,
-				     struct dccp_tx_hist_entry *next);
-
-/*
- * 	Receiver History data structures and declarations
- */
-struct dccp_rx_hist_entry {
-	struct list_head dccphrx_node;
-	u64		 dccphrx_seqno:48,
-			 dccphrx_ccval:4,
-			 dccphrx_type:4;
-	u32		 dccphrx_ndp; /* In fact it is from 8 to 24 bits */
-	ktime_t		 dccphrx_tstamp;
-};
-
-struct dccp_rx_hist {
-	struct kmem_cache *dccprxh_slab;
-};
-
-extern struct dccp_rx_hist *dccp_rx_hist_new(const char *name);
-extern void 		dccp_rx_hist_delete(struct dccp_rx_hist *hist);
-
-static inline struct dccp_rx_hist_entry *
-			dccp_rx_hist_entry_new(struct dccp_rx_hist *hist,
-					       const u32 ndp,
-					       const struct sk_buff *skb,
-					       const gfp_t prio)
+/* initialise loss detection and disable RTT sampling */
+static inline void tfrc_rx_hist_loss_indicated(struct tfrc_rx_hist *h)
 {
-	struct dccp_rx_hist_entry *entry = kmem_cache_alloc(hist->dccprxh_slab,
-							    prio);
-
-	if (entry != NULL) {
-		const struct dccp_hdr *dh = dccp_hdr(skb);
-
-		entry->dccphrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
-		entry->dccphrx_ccval = dh->dccph_ccval;
-		entry->dccphrx_type  = dh->dccph_type;
-		entry->dccphrx_ndp   = ndp;
-		entry->dccphrx_tstamp = ktime_get_real();
-	}
-
-	return entry;
+	h->loss_count = 1;
 }
 
-static inline struct dccp_rx_hist_entry *
-			dccp_rx_hist_head(struct list_head *list)
+/* indicate whether previously a packet was detected missing */
+static inline int tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
 {
-	struct dccp_rx_hist_entry *head = NULL;
-
-	if (!list_empty(list))
-		head = list_entry(list->next, struct dccp_rx_hist_entry,
-				  dccphrx_node);
-	return head;
+	return h->loss_count;
 }
 
-extern int dccp_rx_hist_find_entry(const struct list_head *list, const u64 seq,
-				   u8 *ccval);
-extern struct dccp_rx_hist_entry *
-		dccp_rx_hist_find_data_packet(const struct list_head *list);
-
-extern void dccp_rx_hist_add_packet(struct dccp_rx_hist *hist,
-				    struct list_head *rx_list,
-				    struct list_head *li_list,
-				    struct dccp_rx_hist_entry *packet,
-				    u64 nonloss_seqno);
-
-static inline void dccp_rx_hist_entry_delete(struct dccp_rx_hist *hist,
-					     struct dccp_rx_hist_entry *entry)
+/* any data packets missing between last reception and skb ? */
+static inline int tfrc_rx_hist_new_loss_indicated(struct tfrc_rx_hist *h,
+						  const struct sk_buff *skb,
+						  u32 ndp)
 {
-	if (entry != NULL)
-		kmem_cache_free(hist->dccprxh_slab, entry);
-}
+	int delta = dccp_delta_seqno(tfrc_rx_hist_last_rcv(h)->tfrchrx_seqno,
+				     DCCP_SKB_CB(skb)->dccpd_seq);
 
-extern void dccp_rx_hist_purge(struct dccp_rx_hist *hist,
-			       struct list_head *list);
+	if (delta > 1 && ndp < delta)
+		tfrc_rx_hist_loss_indicated(h);
 
-static inline int
-	dccp_rx_hist_entry_data_packet(const struct dccp_rx_hist_entry *entry)
-{
-	return entry->dccphrx_type == DCCP_PKT_DATA ||
-	       entry->dccphrx_type == DCCP_PKT_DATAACK;
+	return tfrc_rx_hist_loss_pending(h);
 }
 
-extern u64 dccp_rx_hist_detect_loss(struct list_head *rx_list,
-				    struct list_head *li_list, u8 *win_loss);
+extern void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
+				    const struct sk_buff *skb, const u32 ndp);
+
+extern int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb);
+
+struct tfrc_loss_hist;
+extern int  tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
+				struct tfrc_loss_hist *lh,
+				struct sk_buff *skb, u32 ndp,
+				u32 (*first_li)(struct sock *sk),
+				struct sock *sk);
+extern u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h,
+				   const struct sk_buff *skb);
+extern int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h);
+extern void tfrc_rx_hist_purge(struct tfrc_rx_hist *h);
 
 #endif /* _DCCP_PKT_HIST_ */
diff --git a/net/dccp/ccids/lib/tfrc.c b/net/dccp/ccids/lib/tfrc.c
new file mode 100644
index 00000000000..d1dfbb8de64
--- /dev/null
+++ b/net/dccp/ccids/lib/tfrc.c
@@ -0,0 +1,63 @@
+/*
+ * TFRC: main module holding the pieces of the TFRC library together
+ *
+ * Copyright (c) 2007 The University of Aberdeen, Scotland, UK
+ * Copyright (c) 2007 Arnaldo Carvalho de Melo <acme@redhat.com>
+ */
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include "tfrc.h"
+
+#ifdef CONFIG_IP_DCCP_TFRC_DEBUG
+int tfrc_debug;
+module_param(tfrc_debug, bool, 0444);
+MODULE_PARM_DESC(tfrc_debug, "Enable debug messages");
+#endif
+
+extern int  tfrc_tx_packet_history_init(void);
+extern void tfrc_tx_packet_history_exit(void);
+extern int  tfrc_rx_packet_history_init(void);
+extern void tfrc_rx_packet_history_exit(void);
+
+extern int  tfrc_li_init(void);
+extern void tfrc_li_exit(void);
+
+static int __init tfrc_module_init(void)
+{
+	int rc = tfrc_li_init();
+
+	if (rc)
+		goto out;
+
+	rc = tfrc_tx_packet_history_init();
+	if (rc)
+		goto out_free_loss_intervals;
+
+	rc = tfrc_rx_packet_history_init();
+	if (rc)
+		goto out_free_tx_history;
+	return 0;
+
+out_free_tx_history:
+	tfrc_tx_packet_history_exit();
+out_free_loss_intervals:
+	tfrc_li_exit();
+out:
+	return rc;
+}
+
+static void __exit tfrc_module_exit(void)
+{
+	tfrc_rx_packet_history_exit();
+	tfrc_tx_packet_history_exit();
+	tfrc_li_exit();
+}
+
+module_init(tfrc_module_init);
+module_exit(tfrc_module_exit);
+
+MODULE_AUTHOR("Gerrit Renker <gerrit@erg.abdn.ac.uk>, "
+	      "Ian McDonald <ian.mcdonald@jandi.co.nz>, "
+	      "Arnaldo Carvalho de Melo <acme@redhat.com>");
+MODULE_DESCRIPTION("DCCP TFRC library");
+MODULE_LICENSE("GPL");
diff --git a/net/dccp/ccids/lib/tfrc.h b/net/dccp/ccids/lib/tfrc.h
index faf5f7e219e..1fb1187bbf1 100644
--- a/net/dccp/ccids/lib/tfrc.h
+++ b/net/dccp/ccids/lib/tfrc.h
@@ -3,10 +3,11 @@
 /*
  *  net/dccp/ccids/lib/tfrc.h
  *
- *  Copyright (c) 2005 The University of Waikato, Hamilton, New Zealand.
- *  Copyright (c) 2005 Ian McDonald <ian.mcdonald@jandi.co.nz>
- *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
- *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
+ *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
+ *  Copyright (c) 2005-6 The University of Waikato, Hamilton, New Zealand.
+ *  Copyright (c) 2005-6 Ian McDonald <ian.mcdonald@jandi.co.nz>
+ *  Copyright (c) 2005   Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ *  Copyright (c) 2003   Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -15,6 +16,17 @@
  */
 #include <linux/types.h>
 #include <asm/div64.h>
+#include "../../dccp.h"
+/* internal includes that this module exports: */
+#include "loss_interval.h"
+#include "packet_history.h"
+
+#ifdef CONFIG_IP_DCCP_TFRC_DEBUG
+extern int tfrc_debug;
+#define tfrc_pr_debug(format, a...)	DCCP_PR_DEBUG(tfrc_debug, format, ##a)
+#else
+#define tfrc_pr_debug(format, a...)
+#endif
 
 /* integer-arithmetic divisions of type (a * 1000000)/b */
 static inline u64 scaled_div(u64 a, u32 b)
@@ -37,6 +49,15 @@ static inline u32 scaled_div32(u64 a, u32 b)
 	return result;
 }
 
+/**
+ * tfrc_ewma  -  Exponentially weighted moving average
+ * @weight: Weight to be used as damping factor, in units of 1/10
+ */
+static inline u32 tfrc_ewma(const u32 avg, const u32 newval, const u8 weight)
+{
+	return avg ? (weight * avg + (10 - weight) * newval) / 10 : newval;
+}
+
 extern u32 tfrc_calc_x(u16 s, u32 R, u32 p);
 extern u32 tfrc_calc_x_reverse_lookup(u32 fvalue);