1/*
2 * rdbx.h
3 *
4 * replay database with extended packet indices, using a rollover counter
5 *
6 * David A. McGrew
7 * Cisco Systems, Inc.
8 *
9 */
10
11#ifndef RDBX_H
12#define RDBX_H
13
14#include "datatypes.h"
15#include "err.h"
16
17/* #define ROC_TEST */
18
19#ifndef ROC_TEST
20
21typedef uint16_t sequence_number_t; /* 16 bit sequence number */
22typedef uint32_t rollover_counter_t; /* 32 bit rollover counter */
23
24#else /* use small seq_num and roc datatypes for testing purposes */
25
26typedef unsigned char sequence_number_t; /* 8 bit sequence number */
27typedef uint16_t rollover_counter_t; /* 16 bit rollover counter */
28
29#endif
30
31#define seq_num_median (1 << (8*sizeof(sequence_number_t) - 1))
32#define seq_num_max (1 << (8*sizeof(sequence_number_t)))
33
34/*
35 * An xtd_seq_num_t is a 64-bit unsigned integer used as an 'extended'
36 * sequence number.
37 */
38
39typedef uint64_t xtd_seq_num_t;
40
41
42/*
43 * An rdbx_t is a replay database with extended range; it uses an
44 * xtd_seq_num_t and a bitmask of recently received indices.
45 */
46
47typedef struct {
48 xtd_seq_num_t index;
49 bitvector_t bitmask;
50} rdbx_t;
51
52
53/*
54 * rdbx_init(rdbx_ptr, ws)
55 *
56 * initializes the rdbx pointed to by its argument with the window size ws,
57 * setting the rollover counter and sequence number to zero
58 */
59
60err_status_t
61rdbx_init(rdbx_t *rdbx, unsigned long ws);
62
63
64/*
65 * rdbx_dealloc(rdbx_ptr)
66 *
67 * frees memory associated with the rdbx
68 */
69
70err_status_t
71rdbx_dealloc(rdbx_t *rdbx);
72
73
74/*
75 * rdbx_estimate_index(rdbx, guess, s)
76 *
77 * given an rdbx and a sequence number s (from a newly arrived packet),
78 * sets the contents of *guess to contain the best guess of the packet
79 * index to which s corresponds, and returns the difference between
80 * *guess and the locally stored synch info
81 */
82
83int
84rdbx_estimate_index(const rdbx_t *rdbx,
85 xtd_seq_num_t *guess,
86 sequence_number_t s);
87
88/*
89 * rdbx_check(rdbx, delta);
90 *
91 * rdbx_check(&r, delta) checks to see if the xtd_seq_num_t
92 * which is at rdbx->window_start + delta is in the rdb
93 *
94 */
95
96err_status_t
97rdbx_check(const rdbx_t *rdbx, int difference);
98
99/*
100 * replay_add_index(rdbx, delta)
101 *
102 * adds the xtd_seq_num_t at rdbx->window_start + delta to replay_db
103 * (and does *not* check if that xtd_seq_num_t appears in db)
104 *
105 * this function should be called *only* after replay_check has
106 * indicated that the index does not appear in the rdbx, and a mutex
107 * should protect the rdbx between these calls if necessary.
108 */
109
110err_status_t
111rdbx_add_index(rdbx_t *rdbx, int delta);
112
113
114/*
115 * rdbx_set_roc(rdbx, roc) initalizes the rdbx_t at the location rdbx
116 * to have the rollover counter value roc. If that value is less than
117 * the current rollover counter value, then the function returns
118 * err_status_replay_old; otherwise, err_status_ok is returned.
119 *
120 */
121
122err_status_t
123rdbx_set_roc(rdbx_t *rdbx, uint32_t roc);
124
125/*
126 * rdbx_get_roc(rdbx) returns the value of the rollover counter for
127 * the rdbx_t pointed to by rdbx
128 *
129 */
130
131xtd_seq_num_t
132rdbx_get_packet_index(const rdbx_t *rdbx);
133
134/*
135 * xtd_seq_num_t functions - these are *internal* functions of rdbx, and
136 * shouldn't be used to manipulate rdbx internal values. use the rdbx
137 * api instead!
138 */
139
140/*
141 * rdbx_get_ws(rdbx_ptr)
142 *
143 * gets the window size which was used to initialize the rdbx
144 */
145
146unsigned long
147rdbx_get_window_size(const rdbx_t *rdbx);
148
149
150/* index_init(&pi) initializes a packet index pi (sets it to zero) */
151
152void
153index_init(xtd_seq_num_t *pi);
154
155/* index_advance(&pi, s) advances a xtd_seq_num_t forward by s */
156
157void
158index_advance(xtd_seq_num_t *pi, sequence_number_t s);
159
160
161/*
162 * index_guess(local, guess, s)
163 *
164 * given a xtd_seq_num_t local (which represents the highest
165 * known-to-be-good index) and a sequence number s (from a newly
166 * arrived packet), sets the contents of *guess to contain the best
167 * guess of the packet index to which s corresponds, and returns the
168 * difference between *guess and *local
169 */
170
171int
172index_guess(const xtd_seq_num_t *local,
173 xtd_seq_num_t *guess,
174 sequence_number_t s);
175
176
177#endif /* RDBX_H */
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