Merge branch 'dccp' of git://eden-feed.erg.abdn.ac.uk/net-next-2.6

7 files changed, 337 insertions, 343 deletions

diff --git a/net/dccp/ackvec.c b/net/dccp/ackvec.c
index abaf241c7353..41819848bdda 100644
--- a/net/dccp/ackvec.c
+++ b/net/dccp/ackvec.c
@@ -9,18 +9,10 @@
  *      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/init.h>
-#include <linux/errno.h>
 #include <linux/kernel.h>
-#include <linux/skbuff.h>
 #include <linux/slab.h>
 
-#include <net/sock.h>
-
 static struct kmem_cache *dccp_ackvec_slab;
 static struct kmem_cache *dccp_ackvec_record_slab;
 
@@ -92,6 +84,24 @@ int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seqno, u8 nonce_sum)
 	return 0;
 }
 
+static struct dccp_ackvec_record *dccp_ackvec_lookup(struct list_head *av_list,
+						     const u64 ackno)
+{
+	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 NULL;
+}
+
 /*
  * Buffer index and length computation using modulo-buffersize arithmetic.
  * Note that, as pointers move from right to left, head is `before' tail.
@@ -113,248 +123,253 @@ u16 dccp_ackvec_buflen(const struct dccp_ackvec *av)
 	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)
 {
-	long gap;
-	long new_head;
+	u16 ptr = av->av_buf_head;
 
-	if (av->av_vec_len + packets > DCCPAV_MAX_ACKVEC_LEN)
-		return -ENOBUFS;
+	BUG_ON(distance > 0);
+	if (unlikely(dccp_ackvec_is_empty(av)))
+		return;
 
-	gap	 = packets - 1;
-	new_head = av->av_buf_head - packets;
+	do {
+		u8 runlen = dccp_ackvec_runlen(av->av_buf + ptr);
 
-	if (new_head < 0) {
-		if (gap > 0) {
-			memset(av->av_buf, DCCPAV_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 += DCCPAV_MAX_ACKVEC_LEN;
-	}
 
-	av->av_buf_head = new_head;
+		distance += runlen + 1;
+		ptr	  = __ackvec_idx_add(ptr, 1);
 
-	if (gap > 0)
-		memset(av->av_buf + av->av_buf_head + 1,
-		       DCCPAV_NOT_RECEIVED, gap);
+	} while (ptr != av->av_buf_tail);
+}
 
-	av->av_buf[av->av_buf_head] = state;
-	av->av_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 RFC 4340, 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)
 {
-	u8 *cur_head = av->av_buf + av->av_buf_head,
-	   *buf_end  = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;
-	/*
-	 * 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 av_buf.
-	 *
-	 * We may well decide to do buffer compression, etc, but for now lets
-	 * just drop.
-	 *
-	 * From Appendix A.1.1 (`New Packets'):
-	 *
-	 *	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->av_vec_len == 0) {
-		*cur_head = state;
-		av->av_vec_len = 1;
-	} else if (after48(ackno, av->av_buf_ackno)) {
-		const u64 delta = dccp_delta_seqno(av->av_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.
+		 * 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.
 		 */
-		if (delta == 1 && dccp_ackvec_state(cur_head) == state &&
-		    dccp_ackvec_runlen(cur_head) < DCCPAV_MAX_RUNLEN)
-			*cur_head += 1;
-		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 <= buf_ackno
-		 *	arrives, the HC-Receiver will scan the table for
-		 *	the byte corresponding to S. (Indexing structures
-		 *	could reduce the complexity of this scan.)
-		 */
-		u64 delta = dccp_delta_seqno(ackno, av->av_buf_ackno);
+		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_runlen(cur_head);
-			/*
-			 * valid packets not yet in av_buf have a reserved
-			 * entry, with a len equal to 0.
-			 */
-			if (*cur_head == DCCPAV_NOT_RECEIVED && delta == 0) {
-				dccp_pr_debug("Found %llu reserved seat!\n",
-					      (unsigned long long)ackno);
-				*cur_head = state;
-				goto out;
-			}
-			/* len == 0 means one packet */
-			if (delta < len + 1)
-				goto out_duplicate;
-
-			delta -= len + 1;
-			if (++cur_head == buf_end)
-				cur_head = av->av_buf;
+			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->av_buf_ackno = ackno;
-out:
-	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;
+
+	av->av_buf[av->av_buf_head] = state;
+	av->av_buf_ackno	    = seqno;
 
-out_duplicate:
-	/* Duplicate packet */
-	dccp_pr_debug("Received a dup or already considered lost "
-		      "packet: %llu\n", (unsigned long long)ackno);
-	return -EILSEQ;
+	if (num_packets > 1)
+		dccp_ackvec_reserve_seats(av, num_packets - 1);
 }
 
-static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
-				     struct dccp_ackvec_record *avr)
+/**
+ * dccp_ackvec_input  -  Register incoming packet in the buffer
+ */
+void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb)
 {
-	struct dccp_ackvec_record *next;
+	u64 seqno = DCCP_SKB_CB(skb)->dccpd_seq;
+	enum dccp_ackvec_states state = DCCPAV_RECEIVED;
 
-	/* sort out vector length */
-	if (av->av_buf_head <= avr->avr_ack_ptr)
-		av->av_vec_len = avr->avr_ack_ptr - av->av_buf_head;
-	else
-		av->av_vec_len = DCCPAV_MAX_ACKVEC_LEN - 1 -
-				 av->av_buf_head + avr->avr_ack_ptr;
+	if (dccp_ackvec_is_empty(av)) {
+		dccp_ackvec_add_new(av, 1, seqno, state);
+		av->av_tail_ackno = seqno;
 
-	/* 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);
-	}
-}
+	} else {
+		s64 num_packets = dccp_delta_seqno(av->av_buf_ackno, seqno);
+		u8 *current_head = av->av_buf + av->av_buf_head;
 
-void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
-				 const u64 ackno)
-{
-	struct dccp_ackvec_record *avr;
+		if (num_packets == 1 &&
+		    dccp_ackvec_state(current_head) == state &&
+		    dccp_ackvec_runlen(current_head) < DCCPAV_MAX_RUNLEN) {
 
-	/*
-	 * If we traverse backwards, it should be faster when we have large
-	 * windows. We will be receiving ACKs for stuff we sent a while back
-	 * -sorbo.
-	 */
-	list_for_each_entry_reverse(avr, &av->av_records, avr_node) {
-		if (ackno == avr->avr_ack_seqno) {
-			dccp_pr_debug("%s ACK packet 0, len=%d, ack_seqno=%llu, "
-				      "ack_ackno=%llu, ACKED!\n",
-				      dccp_role(sk), avr->avr_ack_runlen,
-				      (unsigned long long)avr->avr_ack_seqno,
-				      (unsigned long long)avr->avr_ack_ackno);
-			dccp_ackvec_throw_record(av, avr);
-			break;
-		} else if (avr->avr_ack_seqno > ackno)
-			break; /* old news */
+			*current_head   += 1;
+			av->av_buf_ackno = seqno;
+
+		} else if (num_packets > 0) {
+			dccp_ackvec_add_new(av, num_packets, seqno, state);
+		} else {
+			dccp_ackvec_update_old(av, num_packets, seqno, state);
+		}
 	}
 }
 
-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;
-	struct dccp_ackvec_record *avr;
+/**
+ * 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;
 
-	/* Check if we actually sent an ACK vector */
-	if (list_empty(&av->av_records))
+	avr = dccp_ackvec_lookup(&av->av_records, ackno);
+	if (avr == NULL)
 		return;
+	/*
+	 * 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.
+	 */
+	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;
 
-	i = len;
+	runlen_now = dccp_ackvec_runlen(av->av_buf + avr->avr_ack_ptr);
 	/*
-	 * XXX
-	 * I think it might be more efficient to work backwards. See comment on
-	 * rcv_ackno. -sorbo.
+	 * 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.
 	 */
-	avr = list_entry(av->av_records.next, struct dccp_ackvec_record, avr_node);
-	while (i--) {
-		const u8 rl = dccp_ackvec_runlen(vector);
-		u64 ackno_end_rl;
+	if (runlen_now > eff_runlen) {
 
-		dccp_set_seqno(&ackno_end_rl, *ackno - rl);
+		av->av_buf[avr->avr_ack_ptr] -= eff_runlen + 1;
+		av->av_buf_tail = __ackvec_idx_add(avr->avr_ack_ptr, 1);
 
+		/* 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;
 		/*
-		 * If our AVR sequence number is greater than the ack, go
-		 * forward in the AVR list until it is not so.
+		 * 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.
 		 */
-		list_for_each_entry_from(avr, &av->av_records, avr_node) {
-			if (!after48(avr->avr_ack_seqno, *ackno))
-				goto found;
-		}
-		/* End of the av_records list, not found, exit */
-		break;
-found:
-		if (between48(avr->avr_ack_seqno, ackno_end_rl, *ackno)) {
-			if (dccp_ackvec_state(vector) != DCCPAV_NOT_RECEIVED) {
-				dccp_pr_debug("%s ACK vector 0, len=%d, "
-					      "ack_seqno=%llu, ack_ackno=%llu, "
-					      "ACKED!\n",
-					      dccp_role(sk), len,
-					      (unsigned long long)
-					      avr->avr_ack_seqno,
-					      (unsigned long long)
-					      avr->avr_ack_ackno);
-				dccp_ackvec_throw_record(av, avr);
-				break;
-			}
-			/*
-			 * If it wasn't received, continue scanning... we might
-			 * find another one.
-			 */
-		}
+		av->av_overflow	= 0;
+	}
 
-		dccp_set_seqno(ackno, ackno_end_rl - 1);
-		++vector;
+	/*
+	 * 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.
+	 */
+	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);
 	}
 }
 
-int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
-		      u64 *ackno, const u8 opt, const u8 *value, const u8 len)
+/*
+ *	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)
 {
-	if (len > DCCP_SINGLE_OPT_MAXLEN)
-		return -1;
+	struct dccp_ackvec_parsed *new = kmalloc(sizeof(*new), GFP_ATOMIC);
+
+	if (new == NULL)
+		return -ENOBUFS;
+	new->vec   = vec;
+	new->len   = len;
+	new->nonce = nonce;
 
-	/* 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,
-					ackno, len, value);
+	list_add_tail(&new->node, head);
 	return 0;
 }
+EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_add);
+
+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 __init dccp_ackvec_init(void)
 {
diff --git a/net/dccp/ackvec.h b/net/dccp/ackvec.h
index 23880be8fc29..e2ab0627a5ff 100644
--- a/net/dccp/ackvec.h
+++ b/net/dccp/ackvec.h
@@ -29,6 +29,9 @@
 /* Estimated minimum average Ack Vector length - used for updating MPS */
 #define DCCPAV_MIN_OPTLEN	16
 
+/* Threshold for coping with large bursts of losses */
+#define DCCPAV_BURST_THRESH	(DCCPAV_MAX_ACKVEC_LEN / 8)
+
 enum dccp_ackvec_states {
 	DCCPAV_RECEIVED =	0x00,
 	DCCPAV_ECN_MARKED =	0x40,
@@ -61,7 +64,6 @@ static inline u8 dccp_ackvec_state(const u8 *cell)
  *		   %DCCP_SINGLE_OPT_MAXLEN cells in the live portion of @av_buf
  * @av_overflow:   if 1 then buf_head == buf_tail indicates buffer wraparound
  * @av_records:	   list of %dccp_ackvec_record (Ack Vectors sent previously)
- * @av_veclen:	   length of the live portion of @av_buf
  */
 struct dccp_ackvec {
 	u8			av_buf[DCCPAV_MAX_ACKVEC_LEN];
@@ -72,7 +74,6 @@ struct dccp_ackvec {
 	bool			av_buf_nonce[DCCPAV_NUM_ACKVECS];
 	u8			av_overflow:1;
 	struct list_head	av_records;
-	u16			av_vec_len;
 };
 
 /** struct dccp_ackvec_record - Records information about sent Ack Vectors
@@ -98,29 +99,38 @@ struct dccp_ackvec_record {
 	u8		 avr_ack_nonce:1;
 };
 
-struct sock;
-struct sk_buff;
-
 extern int dccp_ackvec_init(void);
 extern void dccp_ackvec_exit(void);
 
 extern struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority);
 extern void dccp_ackvec_free(struct dccp_ackvec *av);
 
-extern int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
-			   const u64 ackno, const u8 state);
-
-extern void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av,
-					struct sock *sk, const u64 ackno);
-extern int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
-			     u64 *ackno, const u8 opt,
-			     const u8 *value, const u8 len);
-
+extern void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb);
 extern int  dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seq, u8 sum);
+extern void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno);
 extern u16  dccp_ackvec_buflen(const struct dccp_ackvec *av);
 
 static inline bool dccp_ackvec_is_empty(const struct dccp_ackvec *av)
 {
 	return av->av_overflow == 0 && av->av_buf_head == av->av_buf_tail;
 }
+
+/**
+ * struct dccp_ackvec_parsed  -  Record offsets of Ack Vectors in skb
+ * @vec:	start of vector (offset into skb)
+ * @len:	length of @vec
+ * @nonce:	whether @vec had an ECN nonce of 0 or 1
+ * @node:	FIFO - arranged in descending order of ack_ackno
+ * This structure is used by CCIDs to access Ack Vectors in a received skb.
+ */
+struct dccp_ackvec_parsed {
+	u8		 *vec,
+			 len,
+			 nonce:1;
+	struct list_head node;
+};
+
+extern int dccp_ackvec_parsed_add(struct list_head *head,
+				  u8 *vec, u8 len, u8 nonce);
+extern void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks);
 #endif /* _ACKVEC_H */
diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index cb1b4a0d1877..e96d5e810039 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -246,68 +246,6 @@ static void ccid2_hc_tx_packet_sent(struct sock *sk, unsigned int len)
 #endif
 }
 
-/* XXX Lame code duplication!
- * returns -1 if none was found.
- * else returns the next offset to use in the function call.
- */
-static int ccid2_ackvector(struct sock *sk, struct sk_buff *skb, int offset,
-			   unsigned char **vec, unsigned char *veclen)
-{
-	const struct dccp_hdr *dh = dccp_hdr(skb);
-	unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
-	unsigned char *opt_ptr;
-	const unsigned char *opt_end = (unsigned char *)dh +
-					(dh->dccph_doff * 4);
-	unsigned char opt, len;
-	unsigned char *value;
-
-	BUG_ON(offset < 0);
-	options += offset;
-	opt_ptr = options;
-	if (opt_ptr >= opt_end)
-		return -1;
-
-	while (opt_ptr != opt_end) {
-		opt   = *opt_ptr++;
-		len   = 0;
-		value = NULL;
-
-		/* Check if this isn't a single byte option */
-		if (opt > DCCPO_MAX_RESERVED) {
-			if (opt_ptr == opt_end)
-				goto out_invalid_option;
-
-			len = *opt_ptr++;
-			if (len < 3)
-				goto out_invalid_option;
-			/*
-			 * Remove the type and len fields, leaving
-			 * just the value size
-			 */
-			len     -= 2;
-			value   = opt_ptr;
-			opt_ptr += len;
-
-			if (opt_ptr > opt_end)
-				goto out_invalid_option;
-		}
-
-		switch (opt) {
-		case DCCPO_ACK_VECTOR_0:
-		case DCCPO_ACK_VECTOR_1:
-			*vec	= value;
-			*veclen = len;
-			return offset + (opt_ptr - options);
-		}
-	}
-
-	return -1;
-
-out_invalid_option:
-	DCCP_BUG("Invalid option - this should not happen (previous parsing)!");
-	return -1;
-}
-
 /**
  * ccid2_rtt_estimator - Sample RTT and compute RTO using RFC2988 algorithm
  * This code is almost identical with TCP's tcp_rtt_estimator(), since
@@ -432,16 +370,28 @@ static void ccid2_congestion_event(struct sock *sk, struct ccid2_seq *seqp)
 		ccid2_change_l_ack_ratio(sk, hc->tx_cwnd);
 }
 
+static int ccid2_hc_tx_parse_options(struct sock *sk, u8 packet_type,
+				     u8 option, u8 *optval, u8 optlen)
+{
+	struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
+
+	switch (option) {
+	case DCCPO_ACK_VECTOR_0:
+	case DCCPO_ACK_VECTOR_1:
+		return dccp_ackvec_parsed_add(&hc->tx_av_chunks, optval, optlen,
+					      option - DCCPO_ACK_VECTOR_0);
+	}
+	return 0;
+}
+
 static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
 	const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
+	struct dccp_ackvec_parsed *avp;
 	u64 ackno, seqno;
 	struct ccid2_seq *seqp;
-	unsigned char *vector;
-	unsigned char veclen;
-	int offset = 0;
 	int done = 0;
 	unsigned int maxincr = 0;
 
@@ -475,17 +425,12 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 	}
 
 	/* check forward path congestion */
-	/* still didn't send out new data packets */
-	if (hc->tx_seqh == hc->tx_seqt)
+	if (dccp_packet_without_ack(skb))
 		return;
 
-	switch (DCCP_SKB_CB(skb)->dccpd_type) {
-	case DCCP_PKT_ACK:
-	case DCCP_PKT_DATAACK:
-		break;
-	default:
-		return;
-	}
+	/* still didn't send out new data packets */
+	if (hc->tx_seqh == hc->tx_seqt)
+		goto done;
 
 	ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 	if (after48(ackno, hc->tx_high_ack))
@@ -509,15 +454,16 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 		maxincr = DIV_ROUND_UP(dp->dccps_l_ack_ratio, 2);
 
 	/* go through all ack vectors */
-	while ((offset = ccid2_ackvector(sk, skb, offset,
-					 &vector, &veclen)) != -1) {
+	list_for_each_entry(avp, &hc->tx_av_chunks, node) {
 		/* go through this ack vector */
-		while (veclen--) {
-			u64 ackno_end_rl = SUB48(ackno, dccp_ackvec_runlen(vector));
+		for (; avp->len--; avp->vec++) {
+			u64 ackno_end_rl = SUB48(ackno,
+						 dccp_ackvec_runlen(avp->vec));
 
-			ccid2_pr_debug("ackvec start:%llu end:%llu\n",
+			ccid2_pr_debug("ackvec %llu |%u,%u|\n",
 				       (unsigned long long)ackno,
-				       (unsigned long long)ackno_end_rl);
+				       dccp_ackvec_state(avp->vec) >> 6,
+				       dccp_ackvec_runlen(avp->vec));
 			/* if the seqno we are analyzing is larger than the
 			 * current ackno, then move towards the tail of our
 			 * seqnos.
@@ -536,7 +482,7 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 			 * run length
 			 */
 			while (between48(seqp->ccid2s_seq,ackno_end_rl,ackno)) {
-				const u8 state = dccp_ackvec_state(vector);
+				const u8 state = dccp_ackvec_state(avp->vec);
 
 				/* new packet received or marked */
 				if (state != DCCPAV_NOT_RECEIVED &&
@@ -563,7 +509,6 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 				break;
 
 			ackno = SUB48(ackno_end_rl, 1);
-			vector++;
 		}
 		if (done)
 			break;
@@ -631,10 +576,11 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 		sk_stop_timer(sk, &hc->tx_rtotimer);
 	else
 		sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
-
+done:
 	/* check if incoming Acks allow pending packets to be sent */
 	if (sender_was_blocked && !ccid2_cwnd_network_limited(hc))
 		tasklet_schedule(&dccp_sk(sk)->dccps_xmitlet);
+	dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
 }
 
 static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
@@ -663,6 +609,7 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
 	hc->tx_last_cong = ccid2_time_stamp;
 	setup_timer(&hc->tx_rtotimer, ccid2_hc_tx_rto_expire,
 			(unsigned long)sk);
+	INIT_LIST_HEAD(&hc->tx_av_chunks);
 	return 0;
 }
 
@@ -696,16 +643,17 @@ static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
 }
 
 struct ccid_operations ccid2_ops = {
-	.ccid_id		= DCCPC_CCID2,
-	.ccid_name		= "TCP-like",
-	.ccid_hc_tx_obj_size	= sizeof(struct ccid2_hc_tx_sock),
-	.ccid_hc_tx_init	= ccid2_hc_tx_init,
-	.ccid_hc_tx_exit	= ccid2_hc_tx_exit,
-	.ccid_hc_tx_send_packet	= ccid2_hc_tx_send_packet,
-	.ccid_hc_tx_packet_sent	= ccid2_hc_tx_packet_sent,
-	.ccid_hc_tx_packet_recv	= ccid2_hc_tx_packet_recv,
-	.ccid_hc_rx_obj_size	= sizeof(struct ccid2_hc_rx_sock),
-	.ccid_hc_rx_packet_recv	= ccid2_hc_rx_packet_recv,
+	.ccid_id		  = DCCPC_CCID2,
+	.ccid_name		  = "TCP-like",
+	.ccid_hc_tx_obj_size	  = sizeof(struct ccid2_hc_tx_sock),
+	.ccid_hc_tx_init	  = ccid2_hc_tx_init,
+	.ccid_hc_tx_exit	  = ccid2_hc_tx_exit,
+	.ccid_hc_tx_send_packet	  = ccid2_hc_tx_send_packet,
+	.ccid_hc_tx_packet_sent	  = ccid2_hc_tx_packet_sent,
+	.ccid_hc_tx_parse_options = ccid2_hc_tx_parse_options,
+	.ccid_hc_tx_packet_recv	  = ccid2_hc_tx_packet_recv,
+	.ccid_hc_rx_obj_size	  = sizeof(struct ccid2_hc_rx_sock),
+	.ccid_hc_rx_packet_recv	  = ccid2_hc_rx_packet_recv,
 };
 
 #ifdef CONFIG_IP_DCCP_CCID2_DEBUG
diff --git a/net/dccp/ccids/ccid2.h b/net/dccp/ccids/ccid2.h
index 25cb6b216eda..e9985dafc2c7 100644
--- a/net/dccp/ccids/ccid2.h
+++ b/net/dccp/ccids/ccid2.h
@@ -55,6 +55,7 @@ struct ccid2_seq {
  * @tx_rtt_seq:		     to decay RTTVAR at most once per flight
  * @tx_rpseq:		     last consecutive seqno
  * @tx_rpdupack:	     dupacks since rpseq
+ * @tx_av_chunks:	     list of Ack Vectors received on current skb
  */
 struct ccid2_hc_tx_sock {
 	u32			tx_cwnd;
@@ -79,6 +80,7 @@ struct ccid2_hc_tx_sock {
 	int			tx_rpdupack;
 	u32			tx_last_cong;
 	u64			tx_high_ack;
+	struct list_head	tx_av_chunks;
 };
 
 static inline bool ccid2_cwnd_network_limited(struct ccid2_hc_tx_sock *hc)
diff --git a/net/dccp/input.c b/net/dccp/input.c
index c7aeeba859d4..7d230d14ce22 100644
--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -160,13 +160,15 @@ static void dccp_rcv_reset(struct sock *sk, struct sk_buff *skb)
 	dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 }
 
-static void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
+static void dccp_handle_ackvec_processing(struct sock *sk, struct sk_buff *skb)
 {
-	struct dccp_sock *dp = dccp_sk(sk);
+	struct dccp_ackvec *av = dccp_sk(sk)->dccps_hc_rx_ackvec;
 
-	if (dp->dccps_hc_rx_ackvec != NULL)
-		dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
-					    DCCP_SKB_CB(skb)->dccpd_ack_seq);
+	if (av == NULL)
+		return;
+	if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
+		dccp_ackvec_clear_state(av, DCCP_SKB_CB(skb)->dccpd_ack_seq);
+	dccp_ackvec_input(av, skb);
 }
 
 static void dccp_deliver_input_to_ccids(struct sock *sk, struct sk_buff *skb)
@@ -365,21 +367,13 @@ discard:
 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 			 const struct dccp_hdr *dh, const unsigned len)
 {
-	struct dccp_sock *dp = dccp_sk(sk);
-
 	if (dccp_check_seqno(sk, skb))
 		goto discard;
 
 	if (dccp_parse_options(sk, NULL, skb))
 		return 1;
 
-	if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
-		dccp_event_ack_recv(sk, skb);
-
-	if (dp->dccps_hc_rx_ackvec != NULL &&
-	    dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
-			    DCCP_SKB_CB(skb)->dccpd_seq, DCCPAV_RECEIVED))
-		goto discard;
+	dccp_handle_ackvec_processing(sk, skb);
 	dccp_deliver_input_to_ccids(sk, skb);
 
 	return __dccp_rcv_established(sk, skb, dh, len);
@@ -631,14 +625,7 @@ int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 		if (dccp_parse_options(sk, NULL, skb))
 			return 1;
 
-		if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
-			dccp_event_ack_recv(sk, skb);
-
-		if (dp->dccps_hc_rx_ackvec != NULL &&
-		    dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
-				    DCCP_SKB_CB(skb)->dccpd_seq, DCCPAV_RECEIVED))
-			goto discard;
-
+		dccp_handle_ackvec_processing(sk, skb);
 		dccp_deliver_input_to_ccids(sk, skb);
 	}
 
diff --git a/net/dccp/options.c b/net/dccp/options.c
index 5adeeed5e0d2..f06ffcfc8d71 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -54,7 +54,6 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
 	struct dccp_sock *dp = dccp_sk(sk);
 	const struct dccp_hdr *dh = dccp_hdr(skb);
 	const u8 pkt_type = DCCP_SKB_CB(skb)->dccpd_type;
-	u64 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 	unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
 	unsigned char *opt_ptr = options;
 	const unsigned char *opt_end = (unsigned char *)dh +
@@ -129,14 +128,6 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
 			if (rc)
 				goto out_featneg_failed;
 			break;
-		case DCCPO_ACK_VECTOR_0:
-		case DCCPO_ACK_VECTOR_1:
-			if (dccp_packet_without_ack(skb))   /* RFC 4340, 11.4 */
-				break;
-			if (dp->dccps_hc_rx_ackvec != NULL &&
-			    dccp_ackvec_parse(sk, skb, &ackno, opt, value, len))
-				goto out_invalid_option;
-			break;
 		case DCCPO_TIMESTAMP:
 			if (len != 4)
 				goto out_invalid_option;
@@ -226,6 +217,16 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
 						     pkt_type, opt, value, len))
 				goto out_invalid_option;
 			break;
+		case DCCPO_ACK_VECTOR_0:
+		case DCCPO_ACK_VECTOR_1:
+			if (dccp_packet_without_ack(skb))   /* RFC 4340, 11.4 */
+				break;
+			/*
+			 * Ack vectors are processed by the TX CCID if it is
+			 * interested. The RX CCID need not parse Ack Vectors,
+			 * since it is only interested in clearing old state.
+			 * Fall through.
+			 */
 		case DCCPO_MIN_TX_CCID_SPECIFIC ... DCCPO_MAX_TX_CCID_SPECIFIC:
 			if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
 						     pkt_type, opt, value, len))
@@ -429,6 +430,7 @@ static int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
+	struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 	const u16 buflen = dccp_ackvec_buflen(av);
 	/* Figure out how many options do we need to represent the ackvec */
 	const u8 nr_opts = DIV_ROUND_UP(buflen, DCCP_SINGLE_OPT_MAXLEN);
@@ -437,10 +439,25 @@ static int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
 	const unsigned char *tail, *from;
 	unsigned char *to;
 
-	if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
+	if (dcb->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
+		DCCP_WARN("Lacking space for %u bytes on %s packet\n", len,
+			  dccp_packet_name(dcb->dccpd_type));
 		return -1;
-
-	DCCP_SKB_CB(skb)->dccpd_opt_len += len;
+	}
+	/*
+	 * Since Ack Vectors are variable-length, we can not always predict
+	 * their size. To catch exception cases where the space is running out
+	 * on the skb, a separate Sync is scheduled to carry the Ack Vector.
+	 */
+	if (len > DCCPAV_MIN_OPTLEN &&
+	    len + dcb->dccpd_opt_len + skb->len > dp->dccps_mss_cache) {
+		DCCP_WARN("No space left for Ack Vector (%u) on skb (%u+%u), "
+			  "MPS=%u ==> reduce payload size?\n", len, skb->len,
+			  dcb->dccpd_opt_len, dp->dccps_mss_cache);
+		dp->dccps_sync_scheduled = 1;
+		return 0;
+	}
+	dcb->dccpd_opt_len += len;
 
 	to   = skb_push(skb, len);
 	len  = buflen;
@@ -481,7 +498,7 @@ static int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
 	/*
 	 * Each sent Ack Vector is recorded in the list, as per A.2 of RFC 4340.
 	 */
-	if (dccp_ackvec_update_records(av, DCCP_SKB_CB(skb)->dccpd_seq, nonce))
+	if (dccp_ackvec_update_records(av, dcb->dccpd_seq, nonce))
 		return -ENOBUFS;
 	return 0;
 }
diff --git a/net/dccp/output.c b/net/dccp/output.c
index 45b91853f5ae..d96dd9d362ae 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -283,6 +283,15 @@ static void dccp_xmit_packet(struct sock *sk)
 	 * any local drop will eventually be reported via receiver feedback.
 	 */
 	ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len);
+
+	/*
+	 * If the CCID needs to transfer additional header options out-of-band
+	 * (e.g. Ack Vectors or feature-negotiation options), it activates this
+	 * flag to schedule a Sync. The Sync will automatically incorporate all
+	 * currently pending header options, thus clearing the backlog.
+	 */
+	if (dp->dccps_sync_scheduled)
+		dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
 }
 
 /**
@@ -636,6 +645,12 @@ void dccp_send_sync(struct sock *sk, const u64 ackno,
 	DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 	DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno;
 
+	/*
+	 * Clear the flag in case the Sync was scheduled for out-of-band data,
+	 * such as carrying a long Ack Vector.
+	 */
+	dccp_sk(sk)->dccps_sync_scheduled = 0;
+
 	dccp_transmit_skb(sk, skb);
 }