[linux.git] / net / dccp / ackvec.c

/*
 *  net/dccp/ackvec.c
 *
 *  An implementation of Ack Vectors for the DCCP protocol
 *  Copyright (c) 2007 University of Aberdeen, Scotland, UK
 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <[email protected]>
 *
 *      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 "dccp.h"
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/export.h>

static struct kmem_cache *dccp_ackvec_slab;
static struct kmem_cache *dccp_ackvec_record_slab;

struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
{
	struct dccp_ackvec *av = kmem_cache_zalloc(dccp_ackvec_slab, priority);

	if (av != NULL) {
		av->av_buf_head	= av->av_buf_tail = DCCPAV_MAX_ACKVEC_LEN - 1;
		INIT_LIST_HEAD(&av->av_records);
	}
	return av;
}

static void dccp_ackvec_purge_records(struct dccp_ackvec *av)
{
	struct dccp_ackvec_record *cur, *next;

	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);
}

void dccp_ackvec_free(struct dccp_ackvec *av)
{
	if (likely(av != NULL)) {
		dccp_ackvec_purge_records(av);
		kmem_cache_free(dccp_ackvec_slab, av);
	}
}

/**
 * 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;

	avr = kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
	if (avr == NULL)
		return -ENOBUFS;

	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);
	/*
	 * 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.
	 */
	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;
}

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.
 */
static inline u16 __ackvec_idx_add(const u16 a, const u16 b)
{
	return (a + b) % DCCPAV_MAX_ACKVEC_LEN;
}

static inline u16 __ackvec_idx_sub(const u16 a, const u16 b)
{
	return __ackvec_idx_add(a, DCCPAV_MAX_ACKVEC_LEN - b);
}

u16 dccp_ackvec_buflen(const struct dccp_ackvec *av)
{
	if (unlikely(av->av_overflow))
		return DCCPAV_MAX_ACKVEC_LEN;
	return __ackvec_idx_sub(av->av_buf_tail, av->av_buf_head);
}

/**
 * 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 void dccp_ackvec_update_old(struct dccp_ackvec *av, s64 distance,
				   u64 seqno, enum dccp_ackvec_states state)
{
	u16 ptr = av->av_buf_head;

	BUG_ON(distance > 0);
	if (unlikely(dccp_ackvec_is_empty(av)))
		return;

	do {
		u8 runlen = dccp_ackvec_runlen(av->av_buf + ptr);

		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;
		}

		distance += runlen + 1;
		ptr	  = __ackvec_idx_add(ptr, 1);

	} while (ptr != av->av_buf_tail);
}

/* 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);
}

/**
 * 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
 */
static void dccp_ackvec_add_new(struct dccp_ackvec *av, u32 num_packets,
				u64 seqno, enum dccp_ackvec_states state)
{
	u32 num_cells = num_packets;

	if (num_packets > DCCPAV_BURST_THRESH) {
		u32 lost_packets = num_packets - 1;

		DCCP_WARN("Warning: large burst loss (%u)\n", lost_packets);
		/*
		 * 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.
		 */
		for (num_packets = num_cells = 1; lost_packets; ++num_cells) {
			u8 len = min_t(u32, lost_packets, DCCPAV_MAX_RUNLEN);

			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;
		}
	}

	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;

	if (num_packets > 1)
		dccp_ackvec_reserve_seats(av, num_packets - 1);
}

/**
 * dccp_ackvec_input  -  Register incoming packet in the buffer
 */
void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb)
{
	u64 seqno = DCCP_SKB_CB(skb)->dccpd_seq;
	enum dccp_ackvec_states state = DCCPAV_RECEIVED;

	if (dccp_ackvec_is_empty(av)) {
		dccp_ackvec_add_new(av, 1, seqno, state);
		av->av_tail_ackno = seqno;

	} else {
		s64 num_packets = dccp_delta_seqno(av->av_buf_ackno, seqno);
		u8 *current_head = av->av_buf + av->av_buf_head;

		if (num_packets == 1 &&
		    dccp_ackvec_state(current_head) == state &&
		    dccp_ackvec_runlen(current_head) < DCCPAV_MAX_RUNLEN) {

			*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);
		}
	}
}

/**
 * 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;
	/*
	 * 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;

	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) {

		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;
		/*
		 * 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;
	}

	/*
	 * 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);
	}
}

/*
 *	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);

	if (new == NULL)
		return -ENOBUFS;
	new->vec   = vec;
	new->len   = len;
	new->nonce = nonce;

	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)
{
	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;

	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)
{
	kmem_cache_destroy(dccp_ackvec_slab);
	dccp_ackvec_slab = NULL;
	kmem_cache_destroy(dccp_ackvec_record_slab);
	dccp_ackvec_record_slab = NULL;
}
Commit	Line	Data
ae31c339 ACM	1	/*
	2	* net/dccp/ackvec.c
	3	*
f17a37c9 GR	4	* An implementation of Ack Vectors for the DCCP protocol
f17a37c9 GR	5	* Copyright (c) 2007 University of Aberdeen, Scotland, UK
ae31c339 ACM	6	* Copyright (c) 2005 Arnaldo Carvalho de Melo <[email protected]>
	7	*
	8	* This program is free software; you can redistribute it and/or modify it
	9	* under the terms of the GNU General Public License as published by the
	10	* Free Software Foundation; version 2 of the License;
	11	*/
ae31c339	12	#include "dccp.h"
9b07ef5d	13	#include <linux/kernel.h>
9b07ef5d	14	#include <linux/slab.h>
bc3b2d7f	15	#include <linux/export.h>
ae31c339	16
e18b890b CL	17	static struct kmem_cache *dccp_ackvec_slab;
e18b890b CL	18	static struct kmem_cache *dccp_ackvec_record_slab;
02bcf28c	19
f17a37c9	20	struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
02bcf28c	21	{
f17a37c9 GR	22	struct dccp_ackvec *av = kmem_cache_zalloc(dccp_ackvec_slab, priority);
	23
	24	if (av != NULL) {
b3d14bff	25	av->av_buf_head = av->av_buf_tail = DCCPAV_MAX_ACKVEC_LEN - 1;
f17a37c9 GR	26	INIT_LIST_HEAD(&av->av_records);
	27	}
	28	return av;
	29	}
02bcf28c	30
f17a37c9 GR	31	static void dccp_ackvec_purge_records(struct dccp_ackvec *av)
	32	{
	33	struct dccp_ackvec_record cur, next;
02bcf28c	34
f17a37c9 GR	35	list_for_each_entry_safe(cur, next, &av->av_records, avr_node)
	36	kmem_cache_free(dccp_ackvec_record_slab, cur);
	37	INIT_LIST_HEAD(&av->av_records);
02bcf28c AB	38	}
02bcf28c AB	39
f17a37c9	40	void dccp_ackvec_free(struct dccp_ackvec *av)
02bcf28c	41	{
f17a37c9 GR	42	if (likely(av != NULL)) {
	43	dccp_ackvec_purge_records(av);
	44	kmem_cache_free(dccp_ackvec_slab, av);
	45	}
02bcf28c AB	46	}
02bcf28c AB	47
7d870936 GR	48	/**
	49	* dccp_ackvec_update_records - Record information about sent Ack Vectors
	50	* @av: Ack Vector records to update
	51	* @seqno: Sequence number of the packet carrying the Ack Vector just sent
	52	* @nonce_sum: The sum of all buffer nonces contained in the Ack Vector
	53	*/
	54	int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seqno, u8 nonce_sum)
ae31c339	55	{
02bcf28c AB	56	struct dccp_ackvec_record *avr;
02bcf28c AB	57
f17a37c9	58	avr = kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
2d0817d1	59	if (avr == NULL)
7d870936	60	return -ENOBUFS;
ae31c339	61
7d870936	62	avr->avr_ack_seqno = seqno;
f17a37c9 GR	63	avr->avr_ack_ptr = av->av_buf_head;
f17a37c9 GR	64	avr->avr_ack_ackno = av->av_buf_ackno;
7d870936	65	avr->avr_ack_nonce = nonce_sum;
f17a37c9	66	avr->avr_ack_runlen = dccp_ackvec_runlen(av->av_buf + av->av_buf_head);
b3d14bff GR	67	/*
	68	* When the buffer overflows, we keep no more than one record. This is
	69	* the simplest way of disambiguating sender-Acks dating from before the
	70	* overflow from sender-Acks which refer to after the overflow; a simple
	71	* solution is preferable here since we are handling an exception.
	72	*/
	73	if (av->av_overflow)
	74	dccp_ackvec_purge_records(av);
7d870936 GR	75	/*
	76	* Since GSS is incremented for each packet, the list is automatically
	77	* arranged in descending order of @ack_seqno.
	78	*/
	79	list_add(&avr->avr_node, &av->av_records);
02bcf28c	80
7d870936	81	dccp_pr_debug("Added Vector, ack_seqno=%llu, ack_ackno=%llu (rl=%u)\n",
a47c5104	82	(unsigned long long)avr->avr_ack_seqno,
7d870936 GR	83	(unsigned long long)avr->avr_ack_ackno,
7d870936 GR	84	avr->avr_ack_runlen);
02bcf28c	85	return 0;
ae31c339 ACM	86	}
ae31c339 ACM	87
5753fdfe GR	88	static struct dccp_ackvec_record dccp_ackvec_lookup(struct list_head av_list,
	89	const u64 ackno)
	90	{
	91	struct dccp_ackvec_record *avr;
	92	/*
	93	* Exploit that records are inserted in descending order of sequence
	94	* number, start with the oldest record first. If @ackno is `before'
	95	* the earliest ack_ackno, the packet is too old to be considered.
	96	*/
	97	list_for_each_entry_reverse(avr, av_list, avr_node) {
	98	if (avr->avr_ack_seqno == ackno)
	99	return avr;
	100	if (before48(ackno, avr->avr_ack_seqno))
	101	break;
	102	}
	103	return NULL;
	104	}
	105
b3d14bff GR	106	/*
	107	* Buffer index and length computation using modulo-buffersize arithmetic.
	108	* Note that, as pointers move from right to left, head is `before' tail.
	109	*/
	110	static inline u16 __ackvec_idx_add(const u16 a, const u16 b)
	111	{
	112	return (a + b) % DCCPAV_MAX_ACKVEC_LEN;
	113	}
	114
	115	static inline u16 __ackvec_idx_sub(const u16 a, const u16 b)
	116	{
	117	return __ackvec_idx_add(a, DCCPAV_MAX_ACKVEC_LEN - b);
	118	}
	119
	120	u16 dccp_ackvec_buflen(const struct dccp_ackvec *av)
	121	{
	122	if (unlikely(av->av_overflow))
	123	return DCCPAV_MAX_ACKVEC_LEN;
	124	return __ackvec_idx_sub(av->av_buf_tail, av->av_buf_head);
	125	}
	126
38024086 GR	127	/**
	128	* dccp_ackvec_update_old - Update previous state as per RFC 4340, 11.4.1
	129	* @av: non-empty buffer to update
	130	* @distance: negative or zero distance of @seqno from buf_ackno downward
	131	* @seqno: the (old) sequence number whose record is to be updated
	132	* @state: state in which packet carrying @seqno was received
	133	*/
	134	static void dccp_ackvec_update_old(struct dccp_ackvec *av, s64 distance,
	135	u64 seqno, enum dccp_ackvec_states state)
	136	{
	137	u16 ptr = av->av_buf_head;
	138
	139	BUG_ON(distance > 0);
	140	if (unlikely(dccp_ackvec_is_empty(av)))
	141	return;
	142
	143	do {
	144	u8 runlen = dccp_ackvec_runlen(av->av_buf + ptr);
	145
	146	if (distance + runlen >= 0) {
	147	/*
	148	* Only update the state if packet has not been received
	149	* yet. This is OK as per the second table in RFC 4340,
	150	* 11.4.1; i.e. here we are using the following table:
	151	* RECEIVED
	152	* 0 1 3
	153	* S +---+---+---+
	154	* T 0 \| 0 \| 0 \| 0 \|
	155	* O +---+---+---+
	156	* R 1 \| 1 \| 1 \| 1 \|
	157	* E +---+---+---+
	158	* D 3 \| 0 \| 1 \| 3 \|
	159	* +---+---+---+
	160	* The "Not Received" state was set by reserve_seats().
	161	*/
	162	if (av->av_buf[ptr] == DCCPAV_NOT_RECEIVED)
	163	av->av_buf[ptr] = state;
	164	else
	165	dccp_pr_debug("Not changing %llu state to %u\n",
	166	(unsigned long long)seqno, state);
	167	break;
	168	}
	169
	170	distance += runlen + 1;
	171	ptr = __ackvec_idx_add(ptr, 1);
	172
	173	} while (ptr != av->av_buf_tail);
	174	}
	175
	176	/* Mark @num entries after buf_head as "Not yet received". */
	177	static void dccp_ackvec_reserve_seats(struct dccp_ackvec *av, u16 num)
	178	{
	179	u16 start = __ackvec_idx_add(av->av_buf_head, 1),
	180	len = DCCPAV_MAX_ACKVEC_LEN - start;
	181
	182	/* check for buffer wrap-around */
	183	if (num > len) {
	184	memset(av->av_buf + start, DCCPAV_NOT_RECEIVED, len);
	185	start = 0;
	186	num -= len;
	187	}
	188	if (num)
	189	memset(av->av_buf + start, DCCPAV_NOT_RECEIVED, num);
	190	}
191
192	/**
193	* dccp_ackvec_add_new - Record one or more new entries in Ack Vector buffer
194	* @av: container of buffer to update (can be empty or non-empty)
195	* @num_packets: number of packets to register (must be >= 1)
196	* @seqno: sequence number of the first packet in @num_packets
197	* @state: state in which packet carrying @seqno was received
198	*/
199	static void dccp_ackvec_add_new(struct dccp_ackvec *av, u32 num_packets,
200	u64 seqno, enum dccp_ackvec_states state)
201	{
202	u32 num_cells = num_packets;
203
204	if (num_packets > DCCPAV_BURST_THRESH) {
205	u32 lost_packets = num_packets - 1;
206
207	DCCP_WARN("Warning: large burst loss (%u)\n", lost_packets);
208	/*
209	* We received 1 packet and have a loss of size "num_packets-1"
210	* which we squeeze into num_cells-1 rather than reserving an
211	* entire byte for each lost packet.
212	* The reason is that the vector grows in O(burst_length); when
213	* it grows too large there will no room left for the payload.
214	* This is a trade-off: if a few packets out of the burst show
215	* up later, their state will not be changed; it is simply too
216	* costly to reshuffle/reallocate/copy the buffer each time.
217	* Should such problems persist, we will need to switch to a
218	* different underlying data structure.
219	*/
220	for (num_packets = num_cells = 1; lost_packets; ++num_cells) {
02c31d2e	221	u8 len = min_t(u32, lost_packets, DCCPAV_MAX_RUNLEN);
38024086 GR	222
	223	av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, 1);
	224	av->av_buf[av->av_buf_head] = DCCPAV_NOT_RECEIVED \| len;
	225
	226	lost_packets -= len;
	227	}
	228	}
	229
	230	if (num_cells + dccp_ackvec_buflen(av) >= DCCPAV_MAX_ACKVEC_LEN) {
	231	DCCP_CRIT("Ack Vector buffer overflow: dropping old entries\n");
	232	av->av_overflow = true;
	233	}
	234
	235	av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, num_packets);
	236	if (av->av_overflow)
	237	av->av_buf_tail = av->av_buf_head;
	238
	239	av->av_buf[av->av_buf_head] = state;
	240	av->av_buf_ackno = seqno;
	241
	242	if (num_packets > 1)
	243	dccp_ackvec_reserve_seats(av, num_packets - 1);
	244	}
	245
	246	/**
	247	* dccp_ackvec_input - Register incoming packet in the buffer
	248	*/
	249	void dccp_ackvec_input(struct dccp_ackvec av, struct sk_buff skb)
	250	{
	251	u64 seqno = DCCP_SKB_CB(skb)->dccpd_seq;
	252	enum dccp_ackvec_states state = DCCPAV_RECEIVED;
	253
	254	if (dccp_ackvec_is_empty(av)) {
	255	dccp_ackvec_add_new(av, 1, seqno, state);
	256	av->av_tail_ackno = seqno;
	257
	258	} else {
	259	s64 num_packets = dccp_delta_seqno(av->av_buf_ackno, seqno);
	260	u8 *current_head = av->av_buf + av->av_buf_head;
	261
	262	if (num_packets == 1 &&
	263	dccp_ackvec_state(current_head) == state &&
	264	dccp_ackvec_runlen(current_head) < DCCPAV_MAX_RUNLEN) {
	265
	266	*current_head += 1;
	267	av->av_buf_ackno = seqno;
	268
	269	} else if (num_packets > 0) {
	270	dccp_ackvec_add_new(av, num_packets, seqno, state);
	271	} else {
	272	dccp_ackvec_update_old(av, num_packets, seqno, state);
	273	}
	274	}
	275	}
	276
5753fdfe GR	277	/**
	278	* dccp_ackvec_clear_state - Perform house-keeping / garbage-collection
	279	* This routine is called when the peer acknowledges the receipt of Ack Vectors
	280	* up to and including @ackno. While based on on section A.3 of RFC 4340, here
	281	* are additional precautions to prevent corrupted buffer state. In particular,
	282	* we use tail_ackno to identify outdated records; it always marks the earliest
	283	* packet of group (2) in 11.4.2.
	284	*/
	285	void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno)
f72f2f4c	286	{
5753fdfe GR	287	struct dccp_ackvec_record avr, next;
	288	u8 runlen_now, eff_runlen;
	289	s64 delta;
	290
	291	avr = dccp_ackvec_lookup(&av->av_records, ackno);
	292	if (avr == NULL)
	293	return;
	294	/*
	295	* Deal with outdated acknowledgments: this arises when e.g. there are
	296	* several old records and the acks from the peer come in slowly. In
	297	* that case we may still have records that pre-date tail_ackno.
	298	*/
	299	delta = dccp_delta_seqno(av->av_tail_ackno, avr->avr_ack_ackno);
	300	if (delta < 0)
	301	goto free_records;
	302	/*
	303	* Deal with overlapping Ack Vectors: don't subtract more than the
	304	* number of packets between tail_ackno and ack_ackno.
	305	*/
	306	eff_runlen = delta < avr->avr_ack_runlen ? delta : avr->avr_ack_runlen;
	307
	308	runlen_now = dccp_ackvec_runlen(av->av_buf + avr->avr_ack_ptr);
	309	/*
	310	* The run length of Ack Vector cells does not decrease over time. If
	311	* the run length is the same as at the time the Ack Vector was sent, we
	312	* free the ack_ptr cell. That cell can however not be freed if the run
	313	* length has increased: in this case we need to move the tail pointer
	314	* backwards (towards higher indices), to its next-oldest neighbour.
	315	*/
	316	if (runlen_now > eff_runlen) {
	317
	318	av->av_buf[avr->avr_ack_ptr] -= eff_runlen + 1;
	319	av->av_buf_tail = __ackvec_idx_add(avr->avr_ack_ptr, 1);
	320
	321	/* This move may not have cleared the overflow flag. */
	322	if (av->av_overflow)
	323	av->av_overflow = (av->av_buf_head == av->av_buf_tail);
	324	} else {
	325	av->av_buf_tail = avr->avr_ack_ptr;
	326	/*
	327	* We have made sure that avr points to a valid cell within the
	328	* buffer. This cell is either older than head, or equals head
	329	* (empty buffer): in both cases we no longer have any overflow.
	330	*/
	331	av->av_overflow = 0;
	332	}
	333
	334	/*
	335	* The peer has acknowledged up to and including ack_ackno. Hence the
	336	* first packet in group (2) of 11.4.2 is the successor of ack_ackno.
	337	*/
	338	av->av_tail_ackno = ADD48(avr->avr_ack_ackno, 1);
	339
	340	free_records:
	341	list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) {
	342	list_del(&avr->avr_node);
	343	kmem_cache_free(dccp_ackvec_record_slab, avr);
	344	}
	345	}
	346
7e87fe84 GR	347	/*
	348	* Routines to keep track of Ack Vectors received in an skb
	349	*/
	350	int dccp_ackvec_parsed_add(struct list_head head, u8 vec, u8 len, u8 nonce)
	351	{
	352	struct dccp_ackvec_parsed new = kmalloc(sizeof(new), GFP_ATOMIC);
	353
	354	if (new == NULL)
	355	return -ENOBUFS;
	356	new->vec = vec;
	357	new->len = len;
	358	new->nonce = nonce;
	359
	360	list_add_tail(&new->node, head);
	361	return 0;
	362	}
	363	EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_add);
	364
	365	void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks)
	366	{
	367	struct dccp_ackvec_parsed cur, next;
	368
	369	list_for_each_entry_safe(cur, next, parsed_chunks, node)
	370	kfree(cur);
	371	INIT_LIST_HEAD(parsed_chunks);
	372	}
	373	EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_cleanup);
	374
9b07ef5d ACM	375	int __init dccp_ackvec_init(void)
	376	{
	377	dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
	378	sizeof(struct dccp_ackvec), 0,
20c2df83	379	SLAB_HWCACHE_ALIGN, NULL);
02bcf28c AB	380	if (dccp_ackvec_slab == NULL)
	381	goto out_err;
	382
f17a37c9 GR	383	dccp_ackvec_record_slab = kmem_cache_create("dccp_ackvec_record",
	384	sizeof(struct dccp_ackvec_record),
	385	0, SLAB_HWCACHE_ALIGN, NULL);
02bcf28c AB	386	if (dccp_ackvec_record_slab == NULL)
02bcf28c AB	387	goto out_destroy_slab;
9b07ef5d ACM	388
9b07ef5d ACM	389	return 0;
02bcf28c AB	390
	391	out_destroy_slab:
	392	kmem_cache_destroy(dccp_ackvec_slab);
	393	dccp_ackvec_slab = NULL;
	394	out_err:
59348b19	395	DCCP_CRIT("Unable to create Ack Vector slab cache");
02bcf28c	396	return -ENOBUFS;
9b07ef5d ACM	397	}
	398
	399	void dccp_ackvec_exit(void)
	400	{
20471ed4 JL	401	kmem_cache_destroy(dccp_ackvec_slab);
	402	dccp_ackvec_slab = NULL;
	403	kmem_cache_destroy(dccp_ackvec_record_slab);
	404	dccp_ackvec_record_slab = NULL;
9b07ef5d	405	}