[linux-2.6-block.git] / net / dccp / ackvec.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  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 <acme@ghostprotocols.net>
 */
#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");
		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
b886d83c	1	// SPDX-License-Identifier: GPL-2.0-only
ae31c339 ACM	2	/*
	3	* net/dccp/ackvec.c
	4	*
f17a37c9 GR	5	* An implementation of Ack Vectors for the DCCP protocol
f17a37c9 GR	6	* Copyright (c) 2007 University of Aberdeen, Scotland, UK
ae31c339	7	* Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
ae31c339	8	*/
ae31c339	9	#include "dccp.h"
9b07ef5d	10	#include <linux/kernel.h>
9b07ef5d	11	#include <linux/slab.h>
bc3b2d7f	12	#include <linux/export.h>
ae31c339	13
e18b890b CL	14	static struct kmem_cache *dccp_ackvec_slab;
e18b890b CL	15	static struct kmem_cache *dccp_ackvec_record_slab;
02bcf28c	16
f17a37c9	17	struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
02bcf28c	18	{
f17a37c9 GR	19	struct dccp_ackvec *av = kmem_cache_zalloc(dccp_ackvec_slab, priority);
	20
	21	if (av != NULL) {
b3d14bff	22	av->av_buf_head = av->av_buf_tail = DCCPAV_MAX_ACKVEC_LEN - 1;
f17a37c9 GR	23	INIT_LIST_HEAD(&av->av_records);
	24	}
	25	return av;
	26	}
02bcf28c	27
f17a37c9 GR	28	static void dccp_ackvec_purge_records(struct dccp_ackvec *av)
	29	{
	30	struct dccp_ackvec_record cur, next;
02bcf28c	31
f17a37c9 GR	32	list_for_each_entry_safe(cur, next, &av->av_records, avr_node)
	33	kmem_cache_free(dccp_ackvec_record_slab, cur);
	34	INIT_LIST_HEAD(&av->av_records);
02bcf28c AB	35	}
02bcf28c AB	36
f17a37c9	37	void dccp_ackvec_free(struct dccp_ackvec *av)
02bcf28c	38	{
f17a37c9 GR	39	if (likely(av != NULL)) {
	40	dccp_ackvec_purge_records(av);
	41	kmem_cache_free(dccp_ackvec_slab, av);
	42	}
02bcf28c AB	43	}
02bcf28c AB	44
7d870936 GR	45	/**
	46	* dccp_ackvec_update_records - Record information about sent Ack Vectors
	47	* @av: Ack Vector records to update
	48	* @seqno: Sequence number of the packet carrying the Ack Vector just sent
	49	* @nonce_sum: The sum of all buffer nonces contained in the Ack Vector
	50	*/
	51	int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seqno, u8 nonce_sum)
ae31c339	52	{
02bcf28c AB	53	struct dccp_ackvec_record *avr;
02bcf28c AB	54
f17a37c9	55	avr = kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
2d0817d1	56	if (avr == NULL)
7d870936	57	return -ENOBUFS;
ae31c339	58
7d870936	59	avr->avr_ack_seqno = seqno;
f17a37c9 GR	60	avr->avr_ack_ptr = av->av_buf_head;
f17a37c9 GR	61	avr->avr_ack_ackno = av->av_buf_ackno;
7d870936	62	avr->avr_ack_nonce = nonce_sum;
f17a37c9	63	avr->avr_ack_runlen = dccp_ackvec_runlen(av->av_buf + av->av_buf_head);
b3d14bff GR	64	/*
	65	* When the buffer overflows, we keep no more than one record. This is
	66	* the simplest way of disambiguating sender-Acks dating from before the
	67	* overflow from sender-Acks which refer to after the overflow; a simple
	68	* solution is preferable here since we are handling an exception.
	69	*/
	70	if (av->av_overflow)
	71	dccp_ackvec_purge_records(av);
7d870936 GR	72	/*
	73	* Since GSS is incremented for each packet, the list is automatically
	74	* arranged in descending order of @ack_seqno.
	75	*/
	76	list_add(&avr->avr_node, &av->av_records);
02bcf28c	77
7d870936	78	dccp_pr_debug("Added Vector, ack_seqno=%llu, ack_ackno=%llu (rl=%u)\n",
a47c5104	79	(unsigned long long)avr->avr_ack_seqno,
7d870936 GR	80	(unsigned long long)avr->avr_ack_ackno,
7d870936 GR	81	avr->avr_ack_runlen);
02bcf28c	82	return 0;
ae31c339 ACM	83	}
ae31c339 ACM	84
5753fdfe GR	85	static struct dccp_ackvec_record dccp_ackvec_lookup(struct list_head av_list,
	86	const u64 ackno)
	87	{
	88	struct dccp_ackvec_record *avr;
	89	/*
	90	* Exploit that records are inserted in descending order of sequence
	91	* number, start with the oldest record first. If @ackno is `before'
	92	* the earliest ack_ackno, the packet is too old to be considered.
	93	*/
	94	list_for_each_entry_reverse(avr, av_list, avr_node) {
	95	if (avr->avr_ack_seqno == ackno)
	96	return avr;
	97	if (before48(ackno, avr->avr_ack_seqno))
	98	break;
	99	}
	100	return NULL;
	101	}
	102
b3d14bff GR	103	/*
	104	* Buffer index and length computation using modulo-buffersize arithmetic.
	105	* Note that, as pointers move from right to left, head is `before' tail.
	106	*/
	107	static inline u16 __ackvec_idx_add(const u16 a, const u16 b)
	108	{
	109	return (a + b) % DCCPAV_MAX_ACKVEC_LEN;
	110	}
	111
	112	static inline u16 __ackvec_idx_sub(const u16 a, const u16 b)
	113	{
	114	return __ackvec_idx_add(a, DCCPAV_MAX_ACKVEC_LEN - b);
	115	}
	116
	117	u16 dccp_ackvec_buflen(const struct dccp_ackvec *av)
	118	{
	119	if (unlikely(av->av_overflow))
	120	return DCCPAV_MAX_ACKVEC_LEN;
	121	return __ackvec_idx_sub(av->av_buf_tail, av->av_buf_head);
	122	}
	123
38024086 GR	124	/**
	125	* dccp_ackvec_update_old - Update previous state as per RFC 4340, 11.4.1
	126	* @av: non-empty buffer to update
	127	* @distance: negative or zero distance of @seqno from buf_ackno downward
	128	* @seqno: the (old) sequence number whose record is to be updated
	129	* @state: state in which packet carrying @seqno was received
	130	*/
	131	static void dccp_ackvec_update_old(struct dccp_ackvec *av, s64 distance,
	132	u64 seqno, enum dccp_ackvec_states state)
	133	{
	134	u16 ptr = av->av_buf_head;
	135
	136	BUG_ON(distance > 0);
	137	if (unlikely(dccp_ackvec_is_empty(av)))
	138	return;
	139
	140	do {
	141	u8 runlen = dccp_ackvec_runlen(av->av_buf + ptr);
	142
	143	if (distance + runlen >= 0) {
	144	/*
	145	* Only update the state if packet has not been received
	146	* yet. This is OK as per the second table in RFC 4340,
	147	* 11.4.1; i.e. here we are using the following table:
	148	* RECEIVED
	149	* 0 1 3
	150	* S +---+---+---+
	151	* T 0 \| 0 \| 0 \| 0 \|
	152	* O +---+---+---+
	153	* R 1 \| 1 \| 1 \| 1 \|
	154	* E +---+---+---+
	155	* D 3 \| 0 \| 1 \| 3 \|
	156	* +---+---+---+
	157	* The "Not Received" state was set by reserve_seats().
	158	*/
	159	if (av->av_buf[ptr] == DCCPAV_NOT_RECEIVED)
	160	av->av_buf[ptr] = state;
	161	else
	162	dccp_pr_debug("Not changing %llu state to %u\n",
	163	(unsigned long long)seqno, state);
	164	break;
	165	}
	166
	167	distance += runlen + 1;
	168	ptr = __ackvec_idx_add(ptr, 1);
	169
	170	} while (ptr != av->av_buf_tail);
	171	}
	172
	173	/* Mark @num entries after buf_head as "Not yet received". */
	174	static void dccp_ackvec_reserve_seats(struct dccp_ackvec *av, u16 num)
	175	{
	176	u16 start = __ackvec_idx_add(av->av_buf_head, 1),
	177	len = DCCPAV_MAX_ACKVEC_LEN - start;
	178
	179	/* check for buffer wrap-around */
	180	if (num > len) {
	181	memset(av->av_buf + start, DCCPAV_NOT_RECEIVED, len);
	182	start = 0;
	183	num -= len;
	184	}
	185	if (num)
	186	memset(av->av_buf + start, DCCPAV_NOT_RECEIVED, num);
	187	}
188
189	/**
190	* dccp_ackvec_add_new - Record one or more new entries in Ack Vector buffer
191	* @av: container of buffer to update (can be empty or non-empty)
192	* @num_packets: number of packets to register (must be >= 1)
193	* @seqno: sequence number of the first packet in @num_packets
194	* @state: state in which packet carrying @seqno was received
195	*/
196	static void dccp_ackvec_add_new(struct dccp_ackvec *av, u32 num_packets,
197	u64 seqno, enum dccp_ackvec_states state)
198	{
199	u32 num_cells = num_packets;
200
201	if (num_packets > DCCPAV_BURST_THRESH) {
202	u32 lost_packets = num_packets - 1;
203
204	DCCP_WARN("Warning: large burst loss (%u)\n", lost_packets);
205	/*
206	* We received 1 packet and have a loss of size "num_packets-1"
207	* which we squeeze into num_cells-1 rather than reserving an
208	* entire byte for each lost packet.
209	* The reason is that the vector grows in O(burst_length); when
210	* it grows too large there will no room left for the payload.
211	* This is a trade-off: if a few packets out of the burst show
212	* up later, their state will not be changed; it is simply too
213	* costly to reshuffle/reallocate/copy the buffer each time.
214	* Should such problems persist, we will need to switch to a
215	* different underlying data structure.
216	*/
217	for (num_packets = num_cells = 1; lost_packets; ++num_cells) {
02c31d2e	218	u8 len = min_t(u32, lost_packets, DCCPAV_MAX_RUNLEN);
38024086 GR	219
	220	av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, 1);
	221	av->av_buf[av->av_buf_head] = DCCPAV_NOT_RECEIVED \| len;
	222
	223	lost_packets -= len;
	224	}
	225	}
	226
	227	if (num_cells + dccp_ackvec_buflen(av) >= DCCPAV_MAX_ACKVEC_LEN) {
62262ffd	228	DCCP_CRIT("Ack Vector buffer overflow: dropping old entries");
38024086 GR	229	av->av_overflow = true;
	230	}
	231
	232	av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, num_packets);
	233	if (av->av_overflow)
	234	av->av_buf_tail = av->av_buf_head;
	235
	236	av->av_buf[av->av_buf_head] = state;
	237	av->av_buf_ackno = seqno;
	238
	239	if (num_packets > 1)
	240	dccp_ackvec_reserve_seats(av, num_packets - 1);
	241	}
	242
	243	/**
	244	* dccp_ackvec_input - Register incoming packet in the buffer
	245	*/
	246	void dccp_ackvec_input(struct dccp_ackvec av, struct sk_buff skb)
	247	{
	248	u64 seqno = DCCP_SKB_CB(skb)->dccpd_seq;
	249	enum dccp_ackvec_states state = DCCPAV_RECEIVED;
	250
	251	if (dccp_ackvec_is_empty(av)) {
	252	dccp_ackvec_add_new(av, 1, seqno, state);
	253	av->av_tail_ackno = seqno;
	254
	255	} else {
	256	s64 num_packets = dccp_delta_seqno(av->av_buf_ackno, seqno);
	257	u8 *current_head = av->av_buf + av->av_buf_head;
	258
	259	if (num_packets == 1 &&
	260	dccp_ackvec_state(current_head) == state &&
	261	dccp_ackvec_runlen(current_head) < DCCPAV_MAX_RUNLEN) {
	262
	263	*current_head += 1;
	264	av->av_buf_ackno = seqno;
	265
	266	} else if (num_packets > 0) {
	267	dccp_ackvec_add_new(av, num_packets, seqno, state);
	268	} else {
	269	dccp_ackvec_update_old(av, num_packets, seqno, state);
	270	}
	271	}
	272	}
	273
5753fdfe GR	274	/**
	275	* dccp_ackvec_clear_state - Perform house-keeping / garbage-collection
	276	* This routine is called when the peer acknowledges the receipt of Ack Vectors
	277	* up to and including @ackno. While based on on section A.3 of RFC 4340, here
	278	* are additional precautions to prevent corrupted buffer state. In particular,
	279	* we use tail_ackno to identify outdated records; it always marks the earliest
	280	* packet of group (2) in 11.4.2.
	281	*/
	282	void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno)
f72f2f4c	283	{
5753fdfe GR	284	struct dccp_ackvec_record avr, next;
	285	u8 runlen_now, eff_runlen;
	286	s64 delta;
	287
	288	avr = dccp_ackvec_lookup(&av->av_records, ackno);
	289	if (avr == NULL)
	290	return;
	291	/*
	292	* Deal with outdated acknowledgments: this arises when e.g. there are
	293	* several old records and the acks from the peer come in slowly. In
	294	* that case we may still have records that pre-date tail_ackno.
	295	*/
	296	delta = dccp_delta_seqno(av->av_tail_ackno, avr->avr_ack_ackno);
	297	if (delta < 0)
	298	goto free_records;
	299	/*
	300	* Deal with overlapping Ack Vectors: don't subtract more than the
	301	* number of packets between tail_ackno and ack_ackno.
	302	*/
	303	eff_runlen = delta < avr->avr_ack_runlen ? delta : avr->avr_ack_runlen;
	304
	305	runlen_now = dccp_ackvec_runlen(av->av_buf + avr->avr_ack_ptr);
	306	/*
	307	* The run length of Ack Vector cells does not decrease over time. If
	308	* the run length is the same as at the time the Ack Vector was sent, we
	309	* free the ack_ptr cell. That cell can however not be freed if the run
	310	* length has increased: in this case we need to move the tail pointer
	311	* backwards (towards higher indices), to its next-oldest neighbour.
	312	*/
	313	if (runlen_now > eff_runlen) {
	314
	315	av->av_buf[avr->avr_ack_ptr] -= eff_runlen + 1;
	316	av->av_buf_tail = __ackvec_idx_add(avr->avr_ack_ptr, 1);
	317
	318	/* This move may not have cleared the overflow flag. */
	319	if (av->av_overflow)
	320	av->av_overflow = (av->av_buf_head == av->av_buf_tail);
	321	} else {
	322	av->av_buf_tail = avr->avr_ack_ptr;
	323	/*
	324	* We have made sure that avr points to a valid cell within the
	325	* buffer. This cell is either older than head, or equals head
	326	* (empty buffer): in both cases we no longer have any overflow.
	327	*/
	328	av->av_overflow = 0;
	329	}
	330
	331	/*
	332	* The peer has acknowledged up to and including ack_ackno. Hence the
	333	* first packet in group (2) of 11.4.2 is the successor of ack_ackno.
	334	*/
	335	av->av_tail_ackno = ADD48(avr->avr_ack_ackno, 1);
	336
	337	free_records:
	338	list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) {
	339	list_del(&avr->avr_node);
	340	kmem_cache_free(dccp_ackvec_record_slab, avr);
	341	}
	342	}
	343
7e87fe84 GR	344	/*
	345	* Routines to keep track of Ack Vectors received in an skb
	346	*/
	347	int dccp_ackvec_parsed_add(struct list_head head, u8 vec, u8 len, u8 nonce)
	348	{
	349	struct dccp_ackvec_parsed new = kmalloc(sizeof(new), GFP_ATOMIC);
	350
	351	if (new == NULL)
	352	return -ENOBUFS;
	353	new->vec = vec;
	354	new->len = len;
	355	new->nonce = nonce;
	356
	357	list_add_tail(&new->node, head);
	358	return 0;
	359	}
	360	EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_add);
	361
	362	void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks)
	363	{
	364	struct dccp_ackvec_parsed cur, next;
	365
	366	list_for_each_entry_safe(cur, next, parsed_chunks, node)
	367	kfree(cur);
	368	INIT_LIST_HEAD(parsed_chunks);
	369	}
	370	EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_cleanup);
	371
9b07ef5d ACM	372	int __init dccp_ackvec_init(void)
	373	{
	374	dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
	375	sizeof(struct dccp_ackvec), 0,
20c2df83	376	SLAB_HWCACHE_ALIGN, NULL);
02bcf28c AB	377	if (dccp_ackvec_slab == NULL)
	378	goto out_err;
	379
f17a37c9 GR	380	dccp_ackvec_record_slab = kmem_cache_create("dccp_ackvec_record",
	381	sizeof(struct dccp_ackvec_record),
	382	0, SLAB_HWCACHE_ALIGN, NULL);
02bcf28c AB	383	if (dccp_ackvec_record_slab == NULL)
02bcf28c AB	384	goto out_destroy_slab;
9b07ef5d ACM	385
9b07ef5d ACM	386	return 0;
02bcf28c AB	387
	388	out_destroy_slab:
	389	kmem_cache_destroy(dccp_ackvec_slab);
	390	dccp_ackvec_slab = NULL;
	391	out_err:
59348b19	392	DCCP_CRIT("Unable to create Ack Vector slab cache");
02bcf28c	393	return -ENOBUFS;
9b07ef5d ACM	394	}
	395
	396	void dccp_ackvec_exit(void)
	397	{
20471ed4 JL	398	kmem_cache_destroy(dccp_ackvec_slab);
	399	dccp_ackvec_slab = NULL;
	400	kmem_cache_destroy(dccp_ackvec_record_slab);
	401	dccp_ackvec_record_slab = NULL;
9b07ef5d	402	}