1 files changed, 320 insertions, 337 deletions

diff --git a/net/dccp/ackvec.c b/net/dccp/ackvec.c
index 2c77dafbd09..ba07824af4c 100644
--- a/net/dccp/ackvec.c
+++ b/net/dccp/ackvec.c
@@ -1,426 +1,409 @@
 /*
  *  net/dccp/ackvec.c
  *
- *  An implementation of the DCCP protocol
+ *  An implementation of Ack Vectors for the DCCP protocol
+ *  Copyright (c) 2007 University of Aberdeen, Scotland, UK
  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
  *
  *      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 the
  *      Free Software Foundation; version 2 of the License;
  */
-
-#include "ackvec.h"
 #include "dccp.h"
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/export.h>
 
-#include <linux/dccp.h>
-#include <linux/skbuff.h>
-
-#include <net/sock.h>
+static struct kmem_cache *dccp_ackvec_slab;
+static struct kmem_cache *dccp_ackvec_record_slab;
 
-int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
+struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
 {
-	struct dccp_sock *dp = dccp_sk(sk);
-	struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
-	int len = av->dccpav_vec_len + 2;
-	struct timeval now;
-	u32 elapsed_time;
-	unsigned char *to, *from;
-
-	dccp_timestamp(sk, &now);
-	elapsed_time = timeval_delta(&now, &av->dccpav_time) / 10;
-
-	if (elapsed_time != 0)
-		dccp_insert_option_elapsed_time(sk, skb, elapsed_time);
+	struct dccp_ackvec *av = kmem_cache_zalloc(dccp_ackvec_slab, priority);
 
-	if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
-		return -1;
-
-	/*
-	 * XXX: now we have just one ack vector sent record, so
-	 * we have to wait for it to be cleared.
-	 *
-	 * Of course this is not acceptable, but this is just for
-	 * basic testing now.
-	 */
-	if (av->dccpav_ack_seqno != DCCP_MAX_SEQNO + 1)
-		return -1;
+	if (av != NULL) {
+		av->av_buf_head	= av->av_buf_tail = DCCPAV_MAX_ACKVEC_LEN - 1;
+		INIT_LIST_HEAD(&av->av_records);
+	}
+	return av;
+}
 
-	DCCP_SKB_CB(skb)->dccpd_opt_len += len;
+static void dccp_ackvec_purge_records(struct dccp_ackvec *av)
+{
+	struct dccp_ackvec_record *cur, *next;
 
-	to    = skb_push(skb, len);
-	*to++ = DCCPO_ACK_VECTOR_0;
-	*to++ = len;
+	list_for_each_entry_safe(cur, next, &av->av_records, avr_node)
+		kmem_cache_free(dccp_ackvec_record_slab, cur);
+	INIT_LIST_HEAD(&av->av_records);
+}
 
-	len  = av->dccpav_vec_len;
-	from = av->dccpav_buf + av->dccpav_buf_head;
+void dccp_ackvec_free(struct dccp_ackvec *av)
+{
+	if (likely(av != NULL)) {
+		dccp_ackvec_purge_records(av);
+		kmem_cache_free(dccp_ackvec_slab, av);
+	}
+}
 
-	/* Check if buf_head wraps */
-	if ((int)av->dccpav_buf_head + len > av->dccpav_vec_len) {
-		const u32 tailsize = av->dccpav_vec_len - av->dccpav_buf_head;
+/**
+ * dccp_ackvec_update_records  -  Record information about sent Ack Vectors
+ * @av:		Ack Vector records to update
+ * @seqno:	Sequence number of the packet carrying the Ack Vector just sent
+ * @nonce_sum:	The sum of all buffer nonces contained in the Ack Vector
+ */
+int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seqno, u8 nonce_sum)
+{
+	struct dccp_ackvec_record *avr;
 
-		memcpy(to, from, tailsize);
-		to   += tailsize;
-		len  -= tailsize;
-		from = av->dccpav_buf;
-	}
+	avr = kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
+	if (avr == NULL)
+		return -ENOBUFS;
 
-	memcpy(to, from, len);
+	avr->avr_ack_seqno  = seqno;
+	avr->avr_ack_ptr    = av->av_buf_head;
+	avr->avr_ack_ackno  = av->av_buf_ackno;
+	avr->avr_ack_nonce  = nonce_sum;
+	avr->avr_ack_runlen = dccp_ackvec_runlen(av->av_buf + av->av_buf_head);
 	/*
-	 *	From draft-ietf-dccp-spec-11.txt:
-	 *
-	 *	For each acknowledgement it sends, the HC-Receiver will add an
-	 *	acknowledgement record.  ack_seqno will equal the HC-Receiver
-	 *	sequence number it used for the ack packet; ack_ptr will equal
-	 *	buf_head; ack_ackno will equal buf_ackno; and ack_nonce will
-	 *	equal buf_nonce.
-	 *
-	 * This implemention uses just one ack record for now.
+	 * When the buffer overflows, we keep no more than one record. This is
+	 * the simplest way of disambiguating sender-Acks dating from before the
+	 * overflow from sender-Acks which refer to after the overflow; a simple
+	 * solution is preferable here since we are handling an exception.
 	 */
-	av->dccpav_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
-	av->dccpav_ack_ptr   = av->dccpav_buf_head;
-	av->dccpav_ack_ackno = av->dccpav_buf_ackno;
-	av->dccpav_ack_nonce = av->dccpav_buf_nonce;
-	av->dccpav_sent_len  = av->dccpav_vec_len;
-
-	dccp_pr_debug("%sACK Vector 0, len=%d, ack_seqno=%llu, "
-		      "ack_ackno=%llu\n",
-		      debug_prefix, av->dccpav_sent_len,
-		      (unsigned long long)av->dccpav_ack_seqno,
-		      (unsigned long long)av->dccpav_ack_ackno);
-	return -1;
+	if (av->av_overflow)
+		dccp_ackvec_purge_records(av);
+	/*
+	 * Since GSS is incremented for each packet, the list is automatically
+	 * arranged in descending order of @ack_seqno.
+	 */
+	list_add(&avr->avr_node, &av->av_records);
+
+	dccp_pr_debug("Added Vector, ack_seqno=%llu, ack_ackno=%llu (rl=%u)\n",
+		      (unsigned long long)avr->avr_ack_seqno,
+		      (unsigned long long)avr->avr_ack_ackno,
+		      avr->avr_ack_runlen);
+	return 0;
 }
 
-struct dccp_ackvec *dccp_ackvec_alloc(const unsigned int len,
-				      const gfp_t priority)
+static struct dccp_ackvec_record *dccp_ackvec_lookup(struct list_head *av_list,
+						     const u64 ackno)
 {
-	struct dccp_ackvec *av;
-
-	BUG_ON(len == 0);
-
-	if (len > DCCP_MAX_ACKVEC_LEN)
-		return NULL;
-
-	av = kmalloc(sizeof(*av) + len, priority);
-	if (av != NULL) {
-		av->dccpav_buf_len	= len;
-		av->dccpav_buf_head	=
-			av->dccpav_buf_tail = av->dccpav_buf_len - 1;
-		av->dccpav_buf_ackno	=
-			av->dccpav_ack_ackno = av->dccpav_ack_seqno = ~0LLU;
-		av->dccpav_buf_nonce = av->dccpav_buf_nonce = 0;
-		av->dccpav_ack_ptr	= 0;
-		av->dccpav_time.tv_sec	= 0;
-		av->dccpav_time.tv_usec	= 0;
-		av->dccpav_sent_len	= av->dccpav_vec_len = 0;
+	struct dccp_ackvec_record *avr;
+	/*
+	 * Exploit that records are inserted in descending order of sequence
+	 * number, start with the oldest record first. If @ackno is `before'
+	 * the earliest ack_ackno, the packet is too old to be considered.
+	 */
+	list_for_each_entry_reverse(avr, av_list, avr_node) {
+		if (avr->avr_ack_seqno == ackno)
+			return avr;
+		if (before48(ackno, avr->avr_ack_seqno))
+			break;
 	}
-
-	return av;
+	return NULL;
 }
 
-void dccp_ackvec_free(struct dccp_ackvec *av)
+/*
+ * Buffer index and length computation using modulo-buffersize arithmetic.
+ * Note that, as pointers move from right to left, head is `before' tail.
+ */
+static inline u16 __ackvec_idx_add(const u16 a, const u16 b)
 {
-	kfree(av);
+	return (a + b) % DCCPAV_MAX_ACKVEC_LEN;
 }
 
-static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
-				   const u8 index)
+static inline u16 __ackvec_idx_sub(const u16 a, const u16 b)
 {
-	return av->dccpav_buf[index] & DCCP_ACKVEC_STATE_MASK;
+	return __ackvec_idx_add(a, DCCPAV_MAX_ACKVEC_LEN - b);
 }
 
-static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
-				 const u8 index)
+u16 dccp_ackvec_buflen(const struct dccp_ackvec *av)
 {
-	return av->dccpav_buf[index] & DCCP_ACKVEC_LEN_MASK;
+	if (unlikely(av->av_overflow))
+		return DCCPAV_MAX_ACKVEC_LEN;
+	return __ackvec_idx_sub(av->av_buf_tail, av->av_buf_head);
 }
 
-/*
- * If several packets are missing, the HC-Receiver may prefer to enter multiple
- * bytes with run length 0, rather than a single byte with a larger run length;
- * this simplifies table updates if one of the missing packets arrives.
+/**
+ * dccp_ackvec_update_old  -  Update previous state as per RFC 4340, 11.4.1
+ * @av:		non-empty buffer to update
+ * @distance:   negative or zero distance of @seqno from buf_ackno downward
+ * @seqno:	the (old) sequence number whose record is to be updated
+ * @state:	state in which packet carrying @seqno was received
  */
-static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
-						 const unsigned int packets,
-						 const unsigned char state)
+static void dccp_ackvec_update_old(struct dccp_ackvec *av, s64 distance,
+				   u64 seqno, enum dccp_ackvec_states state)
 {
-	unsigned int gap;
-	long new_head;
+	u16 ptr = av->av_buf_head;
 
-	if (av->dccpav_vec_len + packets > av->dccpav_buf_len)
-		return -ENOBUFS;
+	BUG_ON(distance > 0);
+	if (unlikely(dccp_ackvec_is_empty(av)))
+		return;
 
-	gap	 = packets - 1;
-	new_head = av->dccpav_buf_head - packets;
+	do {
+		u8 runlen = dccp_ackvec_runlen(av->av_buf + ptr);
 
-	if (new_head < 0) {
-		if (gap > 0) {
-			memset(av->dccpav_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
-			       gap + new_head + 1);
-			gap = -new_head;
+		if (distance + runlen >= 0) {
+			/*
+			 * Only update the state if packet has not been received
+			 * yet. This is OK as per the second table in RFC 4340,
+			 * 11.4.1; i.e. here we are using the following table:
+			 *                     RECEIVED
+			 *                      0   1   3
+			 *              S     +---+---+---+
+			 *              T   0 | 0 | 0 | 0 |
+			 *              O     +---+---+---+
+			 *              R   1 | 1 | 1 | 1 |
+			 *              E     +---+---+---+
+			 *              D   3 | 0 | 1 | 3 |
+			 *                    +---+---+---+
+			 * The "Not Received" state was set by reserve_seats().
+			 */
+			if (av->av_buf[ptr] == DCCPAV_NOT_RECEIVED)
+				av->av_buf[ptr] = state;
+			else
+				dccp_pr_debug("Not changing %llu state to %u\n",
+					      (unsigned long long)seqno, state);
+			break;
 		}
-		new_head += av->dccpav_buf_len;
-	} 
 
-	av->dccpav_buf_head = new_head;
+		distance += runlen + 1;
+		ptr	  = __ackvec_idx_add(ptr, 1);
 
-	if (gap > 0)
-		memset(av->dccpav_buf + av->dccpav_buf_head + 1,
-		       DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
+	} while (ptr != av->av_buf_tail);
+}
 
-	av->dccpav_buf[av->dccpav_buf_head] = state;
-	av->dccpav_vec_len += packets;
-	return 0;
+/* Mark @num entries after buf_head as "Not yet received". */
+static void dccp_ackvec_reserve_seats(struct dccp_ackvec *av, u16 num)
+{
+	u16 start = __ackvec_idx_add(av->av_buf_head, 1),
+	    len	  = DCCPAV_MAX_ACKVEC_LEN - start;
+
+	/* check for buffer wrap-around */
+	if (num > len) {
+		memset(av->av_buf + start, DCCPAV_NOT_RECEIVED, len);
+		start = 0;
+		num  -= len;
+	}
+	if (num)
+		memset(av->av_buf + start, DCCPAV_NOT_RECEIVED, num);
 }
 
-/*
- * Implements the draft-ietf-dccp-spec-11.txt Appendix A
+/**
+ * dccp_ackvec_add_new  -  Record one or more new entries in Ack Vector buffer
+ * @av:		 container of buffer to update (can be empty or non-empty)
+ * @num_packets: number of packets to register (must be >= 1)
+ * @seqno:	 sequence number of the first packet in @num_packets
+ * @state:	 state in which packet carrying @seqno was received
  */
-int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
-		    const u64 ackno, const u8 state)
+static void dccp_ackvec_add_new(struct dccp_ackvec *av, u32 num_packets,
+				u64 seqno, enum dccp_ackvec_states state)
 {
-	/*
-	 * Check at the right places if the buffer is full, if it is, tell the
-	 * caller to start dropping packets till the HC-Sender acks our ACK
-	 * vectors, when we will free up space in dccpav_buf.
-	 *
-	 * We may well decide to do buffer compression, etc, but for now lets
-	 * just drop.
-	 *
-	 * From Appendix A:
-	 *
-	 *	Of course, the circular buffer may overflow, either when the
-	 *	HC-Sender is sending data at a very high rate, when the
-	 *	HC-Receiver's acknowledgements are not reaching the HC-Sender,
-	 *	or when the HC-Sender is forgetting to acknowledge those acks
-	 *	(so the HC-Receiver is unable to clean up old state). In this
-	 *	case, the HC-Receiver should either compress the buffer (by
-	 *	increasing run lengths when possible), transfer its state to
-	 *	a larger buffer, or, as a last resort, drop all received
-	 *	packets, without processing them whatsoever, until its buffer
-	 *	shrinks again.
-	 */
+	u32 num_cells = num_packets;
 
-	/* See if this is the first ackno being inserted */
-	if (av->dccpav_vec_len == 0) {
-		av->dccpav_buf[av->dccpav_buf_head] = state;
-		av->dccpav_vec_len = 1;
-	} else if (after48(ackno, av->dccpav_buf_ackno)) {
-		const u64 delta = dccp_delta_seqno(av->dccpav_buf_ackno,
-						   ackno);
+	if (num_packets > DCCPAV_BURST_THRESH) {
+		u32 lost_packets = num_packets - 1;
 
+		DCCP_WARN("Warning: large burst loss (%u)\n", lost_packets);
 		/*
-		 * Look if the state of this packet is the same as the
-		 * previous ackno and if so if we can bump the head len.
-		 */
-		if (delta == 1 &&
-		    dccp_ackvec_state(av, av->dccpav_buf_head) == state &&
-		    (dccp_ackvec_len(av, av->dccpav_buf_head) <
-		     DCCP_ACKVEC_LEN_MASK))
-			av->dccpav_buf[av->dccpav_buf_head]++;
-		else if (dccp_ackvec_set_buf_head_state(av, delta, state))
-			return -ENOBUFS;
-	} else {
-		/*
-		 * A.1.2.  Old Packets
-		 *
-		 *	When a packet with Sequence Number S arrives, and
-		 *	S <= buf_ackno, the HC-Receiver will scan the table
-		 *	for the byte corresponding to S. (Indexing structures
-		 *	could reduce the complexity of this scan.)
+		 * We received 1 packet and have a loss of size "num_packets-1"
+		 * which we squeeze into num_cells-1 rather than reserving an
+		 * entire byte for each lost packet.
+		 * The reason is that the vector grows in O(burst_length); when
+		 * it grows too large there will no room left for the payload.
+		 * This is a trade-off: if a few packets out of the burst show
+		 * up later, their state will not be changed; it is simply too
+		 * costly to reshuffle/reallocate/copy the buffer each time.
+		 * Should such problems persist, we will need to switch to a
+		 * different underlying data structure.
 		 */
-		u64 delta = dccp_delta_seqno(ackno, av->dccpav_buf_ackno);
-		u8 index = av->dccpav_buf_head;
+		for (num_packets = num_cells = 1; lost_packets; ++num_cells) {
+			u8 len = min(lost_packets, (u32)DCCPAV_MAX_RUNLEN);
 
-		while (1) {
-			const u8 len = dccp_ackvec_len(av, index);
-			const u8 state = dccp_ackvec_state(av, index);
-			/*
-			 * valid packets not yet in dccpav_buf have a reserved
-			 * entry, with a len equal to 0.
-			 */
-			if (state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
-			    len == 0 && delta == 0) { /* Found our
-							 reserved seat! */
-				dccp_pr_debug("Found %llu reserved seat!\n",
-					      (unsigned long long)ackno);
-				av->dccpav_buf[index] = state;
-				goto out;
-			}
-			/* len == 0 means one packet */
-			if (delta < len + 1)
-				goto out_duplicate;
-
-			delta -= len + 1;
-			if (++index == av->dccpav_buf_len)
-				index = 0;
+			av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, 1);
+			av->av_buf[av->av_buf_head] = DCCPAV_NOT_RECEIVED | len;
+
+			lost_packets -= len;
 		}
 	}
 
-	av->dccpav_buf_ackno = ackno;
-	dccp_timestamp(sk, &av->dccpav_time);
-out:
-	dccp_pr_debug("");
-	return 0;
+	if (num_cells + dccp_ackvec_buflen(av) >= DCCPAV_MAX_ACKVEC_LEN) {
+		DCCP_CRIT("Ack Vector buffer overflow: dropping old entries\n");
+		av->av_overflow = true;
+	}
+
+	av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, num_packets);
+	if (av->av_overflow)
+		av->av_buf_tail = av->av_buf_head;
 
-out_duplicate:
-	/* Duplicate packet */
-	dccp_pr_debug("Received a dup or already considered lost "
-		      "packet: %llu\n", (unsigned long long)ackno);
-	return -EILSEQ;
+	av->av_buf[av->av_buf_head] = state;
+	av->av_buf_ackno	    = seqno;
+
+	if (num_packets > 1)
+		dccp_ackvec_reserve_seats(av, num_packets - 1);
 }
 
-#ifdef CONFIG_IP_DCCP_DEBUG
-void dccp_ackvector_print(const u64 ackno, const unsigned char *vector, int len)
+/**
+ * dccp_ackvec_input  -  Register incoming packet in the buffer
+ */
+void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb)
 {
-	if (!dccp_debug)
-		return;
+	u64 seqno = DCCP_SKB_CB(skb)->dccpd_seq;
+	enum dccp_ackvec_states state = DCCPAV_RECEIVED;
 
-	printk("ACK vector len=%d, ackno=%llu |", len,
-	       (unsigned long long)ackno);
+	if (dccp_ackvec_is_empty(av)) {
+		dccp_ackvec_add_new(av, 1, seqno, state);
+		av->av_tail_ackno = seqno;
 
-	while (len--) {
-		const u8 state = (*vector & DCCP_ACKVEC_STATE_MASK) >> 6;
-		const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
+	} else {
+		s64 num_packets = dccp_delta_seqno(av->av_buf_ackno, seqno);
+		u8 *current_head = av->av_buf + av->av_buf_head;
 
-		printk("%d,%d|", state, rl);
-		++vector;
-	}
+		if (num_packets == 1 &&
+		    dccp_ackvec_state(current_head) == state &&
+		    dccp_ackvec_runlen(current_head) < DCCPAV_MAX_RUNLEN) {
 
-	printk("\n");
-}
+			*current_head   += 1;
+			av->av_buf_ackno = seqno;
 
-void dccp_ackvec_print(const struct dccp_ackvec *av)
-{
-	dccp_ackvector_print(av->dccpav_buf_ackno,
-			     av->dccpav_buf + av->dccpav_buf_head,
-			     av->dccpav_vec_len);
+		} else if (num_packets > 0) {
+			dccp_ackvec_add_new(av, num_packets, seqno, state);
+		} else {
+			dccp_ackvec_update_old(av, num_packets, seqno, state);
+		}
+	}
 }
-#endif
 
-static void dccp_ackvec_throw_away_ack_record(struct dccp_ackvec *av)
+/**
+ * dccp_ackvec_clear_state  -  Perform house-keeping / garbage-collection
+ * This routine is called when the peer acknowledges the receipt of Ack Vectors
+ * up to and including @ackno. While based on on section A.3 of RFC 4340, here
+ * are additional precautions to prevent corrupted buffer state. In particular,
+ * we use tail_ackno to identify outdated records; it always marks the earliest
+ * packet of group (2) in 11.4.2.
+ */
+void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno)
 {
+	struct dccp_ackvec_record *avr, *next;
+	u8 runlen_now, eff_runlen;
+	s64 delta;
+
+	avr = dccp_ackvec_lookup(&av->av_records, ackno);
+	if (avr == NULL)
+		return;
 	/*
-	 * As we're keeping track of the ack vector size (dccpav_vec_len) and
-	 * the sent ack vector size (dccpav_sent_len) we don't need
-	 * dccpav_buf_tail at all, but keep this code here as in the future
-	 * we'll implement a vector of ack records, as suggested in
-	 * draft-ietf-dccp-spec-11.txt Appendix A. -acme
+	 * Deal with outdated acknowledgments: this arises when e.g. there are
+	 * several old records and the acks from the peer come in slowly. In
+	 * that case we may still have records that pre-date tail_ackno.
 	 */
-#if 0
-	u32 new_buf_tail = av->dccpav_ack_ptr + 1;
-	if (new_buf_tail >= av->dccpav_vec_len)
-		new_buf_tail -= av->dccpav_vec_len;
-	av->dccpav_buf_tail = new_buf_tail;
-#endif
-	av->dccpav_vec_len -= av->dccpav_sent_len;
-}
+	delta = dccp_delta_seqno(av->av_tail_ackno, avr->avr_ack_ackno);
+	if (delta < 0)
+		goto free_records;
+	/*
+	 * Deal with overlapping Ack Vectors: don't subtract more than the
+	 * number of packets between tail_ackno and ack_ackno.
+	 */
+	eff_runlen = delta < avr->avr_ack_runlen ? delta : avr->avr_ack_runlen;
 
-void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
-				 const u64 ackno)
-{
-	/* Check if we actually sent an ACK vector */
-	if (av->dccpav_ack_seqno == DCCP_MAX_SEQNO + 1)
-		return;
+	runlen_now = dccp_ackvec_runlen(av->av_buf + avr->avr_ack_ptr);
+	/*
+	 * The run length of Ack Vector cells does not decrease over time. If
+	 * the run length is the same as at the time the Ack Vector was sent, we
+	 * free the ack_ptr cell. That cell can however not be freed if the run
+	 * length has increased: in this case we need to move the tail pointer
+	 * backwards (towards higher indices), to its next-oldest neighbour.
+	 */
+	if (runlen_now > eff_runlen) {
 
-	if (ackno == av->dccpav_ack_seqno) {
-#ifdef CONFIG_IP_DCCP_DEBUG
-		struct dccp_sock *dp = dccp_sk(sk);
-		const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
-					"CLIENT rx ack: " : "server rx ack: ";
-#endif
-		dccp_pr_debug("%sACK packet 0, len=%d, ack_seqno=%llu, "
-			      "ack_ackno=%llu, ACKED!\n",
-			      debug_prefix, 1,
-			      (unsigned long long)av->dccpav_ack_seqno,
-			      (unsigned long long)av->dccpav_ack_ackno);
-		dccp_ackvec_throw_away_ack_record(av);
-		av->dccpav_ack_seqno = DCCP_MAX_SEQNO + 1;
-	}
-}
+		av->av_buf[avr->avr_ack_ptr] -= eff_runlen + 1;
+		av->av_buf_tail = __ackvec_idx_add(avr->avr_ack_ptr, 1);
 
-static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
-					    struct sock *sk, u64 ackno,
-					    const unsigned char len,
-					    const unsigned char *vector)
-{
-	unsigned char i;
+		/* This move may not have cleared the overflow flag. */
+		if (av->av_overflow)
+			av->av_overflow = (av->av_buf_head == av->av_buf_tail);
+	} else {
+		av->av_buf_tail	= avr->avr_ack_ptr;
+		/*
+		 * We have made sure that avr points to a valid cell within the
+		 * buffer. This cell is either older than head, or equals head
+		 * (empty buffer): in both cases we no longer have any overflow.
+		 */
+		av->av_overflow	= 0;
+	}
 
-	/* Check if we actually sent an ACK vector */
-	if (av->dccpav_ack_seqno == DCCP_MAX_SEQNO + 1)
-		return;
 	/*
-	 * We're in the receiver half connection, so if the received an ACK
-	 * vector ackno (e.g. 50) before dccpav_ack_seqno (e.g. 52), we're
-	 * not interested.
-	 *
-	 * Extra explanation with example:
-	 * 
-	 * if we received an ACK vector with ackno 50, it can only be acking
-	 * 50, 49, 48, etc, not 52 (the seqno for the ACK vector we sent).
+	 * The peer has acknowledged up to and including ack_ackno. Hence the
+	 * first packet in group (2) of 11.4.2 is the successor of ack_ackno.
 	 */
-	/* dccp_pr_debug("is %llu < %llu? ", ackno, av->dccpav_ack_seqno); */
-	if (before48(ackno, av->dccpav_ack_seqno)) {
-		/* dccp_pr_debug_cat("yes\n"); */
-		return;
+	av->av_tail_ackno = ADD48(avr->avr_ack_ackno, 1);
+
+free_records:
+	list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) {
+		list_del(&avr->avr_node);
+		kmem_cache_free(dccp_ackvec_record_slab, avr);
 	}
-	/* dccp_pr_debug_cat("no\n"); */
+}
 
-	i = len;
-	while (i--) {
-		const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
-		u64 ackno_end_rl;
+/*
+ *	Routines to keep track of Ack Vectors received in an skb
+ */
+int dccp_ackvec_parsed_add(struct list_head *head, u8 *vec, u8 len, u8 nonce)
+{
+	struct dccp_ackvec_parsed *new = kmalloc(sizeof(*new), GFP_ATOMIC);
 
-		dccp_set_seqno(&ackno_end_rl, ackno - rl);
+	if (new == NULL)
+		return -ENOBUFS;
+	new->vec   = vec;
+	new->len   = len;
+	new->nonce = nonce;
 
-		/*
-		 * dccp_pr_debug("is %llu <= %llu <= %llu? ", ackno_end_rl,
-		 * av->dccpav_ack_seqno, ackno);
-		 */
-		if (between48(av->dccpav_ack_seqno, ackno_end_rl, ackno)) {
-			const u8 state = (*vector &
-					  DCCP_ACKVEC_STATE_MASK) >> 6;
-			/* dccp_pr_debug_cat("yes\n"); */
-
-			if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) {
-#ifdef CONFIG_IP_DCCP_DEBUG
-				struct dccp_sock *dp = dccp_sk(sk);
-				const char *debug_prefix =
-					dp->dccps_role == DCCP_ROLE_CLIENT ?
-					"CLIENT rx ack: " : "server rx ack: ";
-#endif
-				dccp_pr_debug("%sACK vector 0, len=%d, "
-					      "ack_seqno=%llu, ack_ackno=%llu, "
-					      "ACKED!\n",
-					      debug_prefix, len,
-					      (unsigned long long)
-					      av->dccpav_ack_seqno,
-					      (unsigned long long)
-					      av->dccpav_ack_ackno);
-				dccp_ackvec_throw_away_ack_record(av);
-			}
-			/*
-			 * If dccpav_ack_seqno was not received, no problem
-			 * we'll send another ACK vector.
-			 */
-			av->dccpav_ack_seqno = DCCP_MAX_SEQNO + 1;
-			break;
-		}
-		/* dccp_pr_debug_cat("no\n"); */
+	list_add_tail(&new->node, head);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_add);
 
-		dccp_set_seqno(&ackno, ackno_end_rl - 1);
-		++vector;
-	}
+void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks)
+{
+	struct dccp_ackvec_parsed *cur, *next;
+
+	list_for_each_entry_safe(cur, next, parsed_chunks, node)
+		kfree(cur);
+	INIT_LIST_HEAD(parsed_chunks);
 }
+EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_cleanup);
 
-int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
-		      const u8 opt, const u8 *value, const u8 len)
+int __init dccp_ackvec_init(void)
 {
-	if (len > DCCP_MAX_ACKVEC_LEN)
-		return -1;
+	dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
+					     sizeof(struct dccp_ackvec), 0,
+					     SLAB_HWCACHE_ALIGN, NULL);
+	if (dccp_ackvec_slab == NULL)
+		goto out_err;
+
+	dccp_ackvec_record_slab = kmem_cache_create("dccp_ackvec_record",
+					     sizeof(struct dccp_ackvec_record),
+					     0, SLAB_HWCACHE_ALIGN, NULL);
+	if (dccp_ackvec_record_slab == NULL)
+		goto out_destroy_slab;
 
-	/* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
-	dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
-					DCCP_SKB_CB(skb)->dccpd_ack_seq,
-				        len, value);
 	return 0;
+
+out_destroy_slab:
+	kmem_cache_destroy(dccp_ackvec_slab);
+	dccp_ackvec_slab = NULL;
+out_err:
+	DCCP_CRIT("Unable to create Ack Vector slab cache");
+	return -ENOBUFS;
+}
+
+void dccp_ackvec_exit(void)
+{
+	if (dccp_ackvec_slab != NULL) {
+		kmem_cache_destroy(dccp_ackvec_slab);
+		dccp_ackvec_slab = NULL;
+	}
+	if (dccp_ackvec_record_slab != NULL) {
+		kmem_cache_destroy(dccp_ackvec_record_slab);
+		dccp_ackvec_record_slab = NULL;
+	}
 }