1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
|
/*
* rdbx.h
*
* replay database with extended packet indices, using a rollover counter
*
* David A. McGrew
* Cisco Systems, Inc.
*
*/
#ifndef RDBX_H
#define RDBX_H
#include "datatypes.h"
#include "err.h"
/* #define ROC_TEST */
#ifndef ROC_TEST
typedef uint16_t sequence_number_t; /* 16 bit sequence number */
typedef uint32_t rollover_counter_t; /* 32 bit rollover counter */
#else /* use small seq_num and roc datatypes for testing purposes */
typedef unsigned char sequence_number_t; /* 8 bit sequence number */
typedef uint16_t rollover_counter_t; /* 16 bit rollover counter */
#endif
#define seq_num_median (1 << (8*sizeof(sequence_number_t) - 1))
#define seq_num_max (1 << (8*sizeof(sequence_number_t)))
/*
* An xtd_seq_num_t is a 64-bit unsigned integer used as an 'extended'
* sequence number.
*/
typedef uint64_t xtd_seq_num_t;
/*
* An rdbx_t is a replay database with extended range; it uses an
* xtd_seq_num_t and a bitmask of recently received indices.
*/
typedef struct {
xtd_seq_num_t index;
bitvector_t bitmask;
} rdbx_t;
/*
* rdbx_init(rdbx_ptr, ws)
*
* initializes the rdbx pointed to by its argument with the window size ws,
* setting the rollover counter and sequence number to zero
*/
err_status_t
rdbx_init(rdbx_t *rdbx, unsigned long ws);
/*
* rdbx_dealloc(rdbx_ptr)
*
* frees memory associated with the rdbx
*/
err_status_t
rdbx_dealloc(rdbx_t *rdbx);
/*
* rdbx_estimate_index(rdbx, guess, s)
*
* given an rdbx and a sequence number s (from a newly arrived packet),
* sets the contents of *guess to contain the best guess of the packet
* index to which s corresponds, and returns the difference between
* *guess and the locally stored synch info
*/
int
rdbx_estimate_index(const rdbx_t *rdbx,
xtd_seq_num_t *guess,
sequence_number_t s);
/*
* rdbx_check(rdbx, delta);
*
* rdbx_check(&r, delta) checks to see if the xtd_seq_num_t
* which is at rdbx->window_start + delta is in the rdb
*
*/
err_status_t
rdbx_check(const rdbx_t *rdbx, int difference);
/*
* replay_add_index(rdbx, delta)
*
* adds the xtd_seq_num_t at rdbx->window_start + delta to replay_db
* (and does *not* check if that xtd_seq_num_t appears in db)
*
* this function should be called *only* after replay_check has
* indicated that the index does not appear in the rdbx, and a mutex
* should protect the rdbx between these calls if necessary.
*/
err_status_t
rdbx_add_index(rdbx_t *rdbx, int delta);
/*
* rdbx_set_roc(rdbx, roc) initalizes the rdbx_t at the location rdbx
* to have the rollover counter value roc. If that value is less than
* the current rollover counter value, then the function returns
* err_status_replay_old; otherwise, err_status_ok is returned.
*
*/
err_status_t
rdbx_set_roc(rdbx_t *rdbx, uint32_t roc);
/*
* rdbx_get_roc(rdbx) returns the value of the rollover counter for
* the rdbx_t pointed to by rdbx
*
*/
xtd_seq_num_t
rdbx_get_packet_index(const rdbx_t *rdbx);
/*
* xtd_seq_num_t functions - these are *internal* functions of rdbx, and
* shouldn't be used to manipulate rdbx internal values. use the rdbx
* api instead!
*/
/*
* rdbx_get_ws(rdbx_ptr)
*
* gets the window size which was used to initialize the rdbx
*/
unsigned long
rdbx_get_window_size(const rdbx_t *rdbx);
/* index_init(&pi) initializes a packet index pi (sets it to zero) */
void
index_init(xtd_seq_num_t *pi);
/* index_advance(&pi, s) advances a xtd_seq_num_t forward by s */
void
index_advance(xtd_seq_num_t *pi, sequence_number_t s);
/*
* index_guess(local, guess, s)
*
* given a xtd_seq_num_t local (which represents the highest
* known-to-be-good index) and a sequence number s (from a newly
* arrived packet), sets the contents of *guess to contain the best
* guess of the packet index to which s corresponds, and returns the
* difference between *guess and *local
*/
int
index_guess(const xtd_seq_num_t *local,
xtd_seq_num_t *guess,
sequence_number_t s);
#endif /* RDBX_H */
|
