net/dccp/ackvec.h

   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
  35 enum 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
  43 static inline u8 dccp_ackvec_runlen(const u8 *cell)
  44 {
  45         return *cell & DCCPAV_MAX_RUNLEN;
  46 }
  47
  48 static inline u8 dccp_ackvec_state(const u8 *cell)
  49 {
  50         return *cell & ~DCCPAV_MAX_RUNLEN;
  51 }
  52
  53 /** struct dccp_ackvec - Ack Vector main data structure
  54  *
  55  * This implements a fixed-size circular buffer within an array and is largely
  56  * based on Appendix A of RFC 4340.
  57  *
  58  * @av_buf:        circular buffer storage area
  59  * @av_buf_head:   head index; begin of live portion in @av_buf
  60  * @av_buf_tail:   tail index; first index _after_ the live portion in @av_buf
  61  * @av_buf_ackno:  highest seqno of acknowledgeable packet recorded in @av_buf
  62  * @av_tail_ackno: lowest  seqno of acknowledgeable packet recorded in @av_buf
  63  * @av_buf_nonce:  ECN nonce sums, each covering subsequent segments of up to
  64  *                 %DCCP_SINGLE_OPT_MAXLEN cells in the live portion of @av_buf
  65  * @av_overflow:   if 1 then buf_head == buf_tail indicates buffer wraparound
  66  * @av_records:    list of %dccp_ackvec_record (Ack Vectors sent previously)
  67  */
  68 struct dccp_ackvec {
  69         u8                      av_buf[DCCPAV_MAX_ACKVEC_LEN];
  70         u16                     av_buf_head;
  71         u16                     av_buf_tail;
  72         u64                     av_buf_ackno:48;
  73         u64                     av_tail_ackno:48;
  74         bool                    av_buf_nonce[DCCPAV_NUM_ACKVECS];
  75         u8                      av_overflow:1;
  76         struct list_head        av_records;
  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  */
  93 struct 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
 102 extern int dccp_ackvec_init(void);
 103 extern void dccp_ackvec_exit(void);
 104
 105 extern struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority);
 106 extern void dccp_ackvec_free(struct dccp_ackvec *av);
 107
 108 extern void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb);
 109 extern int  dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seq, u8 sum);
 110 extern void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno);
 111 extern u16  dccp_ackvec_buflen(const struct dccp_ackvec *av);
 112
 113 static 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  * This structure is used by CCIDs to access Ack Vectors in a received skb.
 125  */
 126 struct dccp_ackvec_parsed {
 127         u8               *vec,
 128                          len,
 129                          nonce:1;
 130         struct list_head node;
 131 };
 132
 133 extern int dccp_ackvec_parsed_add(struct list_head *head,
 134                                   u8 *vec, u8 len, u8 nonce);
 135 extern void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks);
 136 #endif /* _ACKVEC_H */