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
104int dccp_ackvec_init(void);
105void dccp_ackvec_exit(void);
106
107struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority);
108void dccp_ackvec_free(struct dccp_ackvec *av);
109
110void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb);
111int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seq, u8 sum);
112void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno);
113u16 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
136int dccp_ackvec_parsed_add(struct list_head *head, u8 *vec, u8 len, u8 nonce);
137void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks);
138#endif /* _ACKVEC_H */
139