/* *  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> * *      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(lost_packets, (u32)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){	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;	}}