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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 
 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 /**
 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  */
 69 struct 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  */
 95 struct 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 
104 int dccp_ackvec_init(void);
105 void dccp_ackvec_exit(void);
106 
107 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority);
108 void dccp_ackvec_free(struct dccp_ackvec *av);
109 
110 void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb);
111 int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seq, u8 sum);
112 void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno);
113 u16 dccp_ackvec_buflen(const struct dccp_ackvec *av);
114 
115 static 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  */
129 struct dccp_ackvec_parsed {
130         u8               *vec,
131                          len,
132                          nonce:1;
133         struct list_head node;
134 };
135 
136 int dccp_ackvec_parsed_add(struct list_head *head, u8 *vec, u8 len, u8 nonce);
137 void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks);
138 #endif /* _ACKVEC_H */
139 

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