linux/net/dccp/ackvec.h
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   1#ifndef _ACKVEC_H
   2#define _ACKVEC_H
   3/*
   4 *  net/dccp/ackvec.h
   5 *
   6 *  An implementation of Ack Vectors for the DCCP protocol
   7 *  Copyright (c) 2007 University of Aberdeen, Scotland, UK
   8 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@mandriva.com>
   9 *      This program is free software; you can redistribute it and/or modify it
  10 *      under the terms of the GNU General Public License version 2 as
  11 *      published by the Free Software Foundation.
  12 */
  13
  14#include <linux/dccp.h>
  15#include <linux/compiler.h>
  16#include <linux/list.h>
  17#include <linux/types.h>
  18
  19/*
  20 * Ack Vector buffer space is static, in multiples of %DCCP_SINGLE_OPT_MAXLEN,
  21 * the maximum size of a single Ack Vector. Setting %DCCPAV_NUM_ACKVECS to 1
  22 * will be sufficient for most cases of low Ack Ratios, using a value of 2 gives
  23 * more headroom if Ack Ratio is higher or when the sender acknowledges slowly.
  24 * The maximum value is bounded by the u16 types for indices and functions.
  25 */
  26#define DCCPAV_NUM_ACKVECS      2
  27#define DCCPAV_MAX_ACKVEC_LEN   (DCCP_SINGLE_OPT_MAXLEN * DCCPAV_NUM_ACKVECS)
  28
  29/* Estimated minimum average Ack Vector length - used for updating MPS */
  30#define DCCPAV_MIN_OPTLEN       16
  31
  32/* Threshold for coping with large bursts of losses */
  33#define DCCPAV_BURST_THRESH     (DCCPAV_MAX_ACKVEC_LEN / 8)
  34
  35enum dccp_ackvec_states {
  36        DCCPAV_RECEIVED =       0x00,
  37        DCCPAV_ECN_MARKED =     0x40,
  38        DCCPAV_RESERVED =       0x80,
  39        DCCPAV_NOT_RECEIVED =   0xC0
  40};
  41#define DCCPAV_MAX_RUNLEN       0x3F
  42
  43static inline u8 dccp_ackvec_runlen(const u8 *cell)
  44{
  45        return *cell & DCCPAV_MAX_RUNLEN;
  46}
  47
  48static inline u8 dccp_ackvec_state(const u8 *cell)
  49{
  50        return *cell & ~DCCPAV_MAX_RUNLEN;
  51}
  52
  53/**
  54 * struct dccp_ackvec - Ack Vector main data structure
  55 *
  56 * This implements a fixed-size circular buffer within an array and is largely
  57 * based on Appendix A of RFC 4340.
  58 *
  59 * @av_buf:        circular buffer storage area
  60 * @av_buf_head:   head index; begin of live portion in @av_buf
  61 * @av_buf_tail:   tail index; first index _after_ the live portion in @av_buf
  62 * @av_buf_ackno:  highest seqno of acknowledgeable packet recorded in @av_buf
  63 * @av_tail_ackno: lowest  seqno of acknowledgeable packet recorded in @av_buf
  64 * @av_buf_nonce:  ECN nonce sums, each covering subsequent segments of up to
  65 *                 %DCCP_SINGLE_OPT_MAXLEN cells in the live portion of @av_buf
  66 * @av_overflow:   if 1 then buf_head == buf_tail indicates buffer wraparound
  67 * @av_records:    list of %dccp_ackvec_record (Ack Vectors sent previously)
  68 */
  69struct dccp_ackvec {
  70        u8                      av_buf[DCCPAV_MAX_ACKVEC_LEN];
  71        u16                     av_buf_head;
  72        u16                     av_buf_tail;
  73        u64                     av_buf_ackno:48;
  74        u64                     av_tail_ackno:48;
  75        bool                    av_buf_nonce[DCCPAV_NUM_ACKVECS];
  76        u8                      av_overflow:1;
  77        struct list_head        av_records;
  78};
  79
  80/**
  81 * struct dccp_ackvec_record - Records information about sent Ack Vectors
  82 *
  83 * These list entries define the additional information which the HC-Receiver
  84 * keeps about recently-sent Ack Vectors; again refer to RFC 4340, Appendix A.
  85 *
  86 * @avr_node:       the list node in @av_records
  87 * @avr_ack_seqno:  sequence number of the packet the Ack Vector was sent on
  88 * @avr_ack_ackno:  the Ack number that this record/Ack Vector refers to
  89 * @avr_ack_ptr:    pointer into @av_buf where this record starts
  90 * @avr_ack_runlen: run length of @avr_ack_ptr at the time of sending
  91 * @avr_ack_nonce:  the sum of @av_buf_nonce's at the time this record was sent
  92 *
  93 * The list as a whole is sorted in descending order by @avr_ack_seqno.
  94 */
  95struct dccp_ackvec_record {
  96        struct list_head avr_node;
  97        u64              avr_ack_seqno:48;
  98        u64              avr_ack_ackno:48;
  99        u16              avr_ack_ptr;
 100        u8               avr_ack_runlen;
 101        u8               avr_ack_nonce:1;
 102};
 103
 104extern int dccp_ackvec_init(void);
 105extern void dccp_ackvec_exit(void);
 106
 107extern struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority);
 108extern void dccp_ackvec_free(struct dccp_ackvec *av);
 109
 110extern void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb);
 111extern int  dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seq, u8 sum);
 112extern void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno);
 113extern u16  dccp_ackvec_buflen(const struct dccp_ackvec *av);
 114
 115static inline bool dccp_ackvec_is_empty(const struct dccp_ackvec *av)
 116{
 117        return av->av_overflow == 0 && av->av_buf_head == av->av_buf_tail;
 118}
 119
 120/**
 121 * struct dccp_ackvec_parsed  -  Record offsets of Ack Vectors in skb
 122 * @vec:        start of vector (offset into skb)
 123 * @len:        length of @vec
 124 * @nonce:      whether @vec had an ECN nonce of 0 or 1
 125 * @node:       FIFO - arranged in descending order of ack_ackno
 126 *
 127 * This structure is used by CCIDs to access Ack Vectors in a received skb.
 128 */
 129struct dccp_ackvec_parsed {
 130        u8               *vec,
 131                         len,
 132                         nonce:1;
 133        struct list_head node;
 134};
 135
 136extern int dccp_ackvec_parsed_add(struct list_head *head,
 137                                  u8 *vec, u8 len, u8 nonce);
 138extern void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks);
 139#endif /* _ACKVEC_H */
 140
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