/usr/include/srtp/rdbx.h is in libsrtp0-dev 1.4.5~20130609~dfsg-2ubuntu1.
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* 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 */
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