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/net/dccp/ackvec.h

http://github.com/mirrors/linux
C Header | 136 lines | 64 code | 15 blank | 57 comment | 3 complexity | ecd9e1b941d50c6e76aa5981bfc0b56f MD5 | raw file
  1/* SPDX-License-Identifier: GPL-2.0-only */
  2#ifndef _ACKVEC_H
  3#define _ACKVEC_H
  4/*
  5 *  net/dccp/ackvec.h
  6 *
  7 *  An implementation of Ack Vectors for the DCCP protocol
  8 *  Copyright (c) 2007 University of Aberdeen, Scotland, UK
  9 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@mandriva.com>
 10 */
 11
 12#include <linux/dccp.h>
 13#include <linux/compiler.h>
 14#include <linux/list.h>
 15#include <linux/types.h>
 16
 17/*
 18 * Ack Vector buffer space is static, in multiples of %DCCP_SINGLE_OPT_MAXLEN,
 19 * the maximum size of a single Ack Vector. Setting %DCCPAV_NUM_ACKVECS to 1
 20 * will be sufficient for most cases of low Ack Ratios, using a value of 2 gives
 21 * more headroom if Ack Ratio is higher or when the sender acknowledges slowly.
 22 * The maximum value is bounded by the u16 types for indices and functions.
 23 */
 24#define DCCPAV_NUM_ACKVECS	2
 25#define DCCPAV_MAX_ACKVEC_LEN	(DCCP_SINGLE_OPT_MAXLEN * DCCPAV_NUM_ACKVECS)
 26
 27/* Estimated minimum average Ack Vector length - used for updating MPS */
 28#define DCCPAV_MIN_OPTLEN	16
 29
 30/* Threshold for coping with large bursts of losses */
 31#define DCCPAV_BURST_THRESH	(DCCPAV_MAX_ACKVEC_LEN / 8)
 32
 33enum dccp_ackvec_states {
 34	DCCPAV_RECEIVED =	0x00,
 35	DCCPAV_ECN_MARKED =	0x40,
 36	DCCPAV_RESERVED =	0x80,
 37	DCCPAV_NOT_RECEIVED =	0xC0
 38};
 39#define DCCPAV_MAX_RUNLEN	0x3F
 40
 41static inline u8 dccp_ackvec_runlen(const u8 *cell)
 42{
 43	return *cell & DCCPAV_MAX_RUNLEN;
 44}
 45
 46static inline u8 dccp_ackvec_state(const u8 *cell)
 47{
 48	return *cell & ~DCCPAV_MAX_RUNLEN;
 49}
 50
 51/**
 52 * struct dccp_ackvec - Ack Vector main data structure
 53 *
 54 * This implements a fixed-size circular buffer within an array and is largely
 55 * based on Appendix A of RFC 4340.
 56 *
 57 * @av_buf:	   circular buffer storage area
 58 * @av_buf_head:   head index; begin of live portion in @av_buf
 59 * @av_buf_tail:   tail index; first index _after_ the live portion in @av_buf
 60 * @av_buf_ackno:  highest seqno of acknowledgeable packet recorded in @av_buf
 61 * @av_tail_ackno: lowest  seqno of acknowledgeable packet recorded in @av_buf
 62 * @av_buf_nonce:  ECN nonce sums, each covering subsequent segments of up to
 63 *		   %DCCP_SINGLE_OPT_MAXLEN cells in the live portion of @av_buf
 64 * @av_overflow:   if 1 then buf_head == buf_tail indicates buffer wraparound
 65 * @av_records:	   list of %dccp_ackvec_record (Ack Vectors sent previously)
 66 */
 67struct dccp_ackvec {
 68	u8			av_buf[DCCPAV_MAX_ACKVEC_LEN];
 69	u16			av_buf_head;
 70	u16			av_buf_tail;
 71	u64			av_buf_ackno:48;
 72	u64			av_tail_ackno:48;
 73	bool			av_buf_nonce[DCCPAV_NUM_ACKVECS];
 74	u8			av_overflow:1;
 75	struct list_head	av_records;
 76};
 77
 78/**
 79 * struct dccp_ackvec_record - Records information about sent Ack Vectors
 80 *
 81 * These list entries define the additional information which the HC-Receiver
 82 * keeps about recently-sent Ack Vectors; again refer to RFC 4340, Appendix A.
 83 *
 84 * @avr_node:	    the list node in @av_records
 85 * @avr_ack_seqno:  sequence number of the packet the Ack Vector was sent on
 86 * @avr_ack_ackno:  the Ack number that this record/Ack Vector refers to
 87 * @avr_ack_ptr:    pointer into @av_buf where this record starts
 88 * @avr_ack_runlen: run length of @avr_ack_ptr at the time of sending
 89 * @avr_ack_nonce:  the sum of @av_buf_nonce's at the time this record was sent
 90 *
 91 * The list as a whole is sorted in descending order by @avr_ack_seqno.
 92 */
 93struct dccp_ackvec_record {
 94	struct list_head avr_node;
 95	u64		 avr_ack_seqno:48;
 96	u64		 avr_ack_ackno:48;
 97	u16		 avr_ack_ptr;
 98	u8		 avr_ack_runlen;
 99	u8		 avr_ack_nonce:1;
100};
101
102int dccp_ackvec_init(void);
103void dccp_ackvec_exit(void);
104
105struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority);
106void dccp_ackvec_free(struct dccp_ackvec *av);
107
108void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb);
109int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seq, u8 sum);
110void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno);
111u16 dccp_ackvec_buflen(const struct dccp_ackvec *av);
112
113static inline bool dccp_ackvec_is_empty(const struct dccp_ackvec *av)
114{
115	return av->av_overflow == 0 && av->av_buf_head == av->av_buf_tail;
116}
117
118/**
119 * struct dccp_ackvec_parsed  -  Record offsets of Ack Vectors in skb
120 * @vec:	start of vector (offset into skb)
121 * @len:	length of @vec
122 * @nonce:	whether @vec had an ECN nonce of 0 or 1
123 * @node:	FIFO - arranged in descending order of ack_ackno
124 *
125 * This structure is used by CCIDs to access Ack Vectors in a received skb.
126 */
127struct dccp_ackvec_parsed {
128	u8		 *vec,
129			 len,
130			 nonce:1;
131	struct list_head node;
132};
133
134int dccp_ackvec_parsed_add(struct list_head *head, u8 *vec, u8 len, u8 nonce);
135void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks);
136#endif /* _ACKVEC_H */