187 lines
4.0 KiB
C
187 lines
4.0 KiB
C
/*
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* rdbx.h
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*
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* replay database with extended packet indices, using a rollover counter
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*
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* David A. McGrew
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* Cisco Systems, Inc.
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*
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*/
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#ifndef RDBX_H
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#define RDBX_H
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#include "datatypes.h"
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#include "err.h"
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/* #define ROC_TEST */
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#ifndef ROC_TEST
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typedef uint16_t sequence_number_t; /* 16 bit sequence number */
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typedef uint32_t rollover_counter_t; /* 32 bit rollover counter */
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#else /* use small seq_num and roc datatypes for testing purposes */
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typedef unsigned char sequence_number_t; /* 8 bit sequence number */
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typedef uint16_t rollover_counter_t; /* 16 bit rollover counter */
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#endif
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#define seq_num_median (1 << (8*sizeof(sequence_number_t) - 1))
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#define seq_num_max (1 << (8*sizeof(sequence_number_t)))
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/*
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* An xtd_seq_num_t is a 64-bit unsigned integer used as an 'extended'
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* sequence number.
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*/
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typedef uint64_t xtd_seq_num_t;
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/*
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* An rdbx_t is a replay database with extended range; it uses an
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* xtd_seq_num_t and a bitmask of recently received indices.
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*/
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typedef struct {
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xtd_seq_num_t index;
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bitvector_t bitmask;
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} rdbx_t;
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/*
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* rdbx_init(rdbx_ptr, ws)
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*
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* initializes the rdbx pointed to by its argument with the window size ws,
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* setting the rollover counter and sequence number to zero
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*/
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err_status_t
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rdbx_init(rdbx_t *rdbx, unsigned long ws);
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/*
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* rdbx_dealloc(rdbx_ptr)
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*
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* frees memory associated with the rdbx
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*/
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err_status_t
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rdbx_dealloc(rdbx_t *rdbx);
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/*
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* rdbx_estimate_index(rdbx, guess, s)
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*
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* given an rdbx and a sequence number s (from a newly arrived packet),
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* sets the contents of *guess to contain the best guess of the packet
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* index to which s corresponds, and returns the difference between
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* *guess and the locally stored synch info
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*/
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int
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rdbx_estimate_index(const rdbx_t *rdbx,
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xtd_seq_num_t *guess,
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sequence_number_t s);
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/*
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* rdbx_check(rdbx, delta);
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*
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* rdbx_check(&r, delta) checks to see if the xtd_seq_num_t
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* which is at rdbx->window_start + delta is in the rdb
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*
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*/
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err_status_t
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rdbx_check(const rdbx_t *rdbx, int difference);
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/*
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* replay_add_index(rdbx, delta)
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*
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* adds the xtd_seq_num_t at rdbx->window_start + delta to replay_db
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* (and does *not* check if that xtd_seq_num_t appears in db)
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*
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* this function should be called *only* after replay_check has
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* indicated that the index does not appear in the rdbx, and a mutex
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* should protect the rdbx between these calls if necessary.
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*/
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err_status_t
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rdbx_add_index(rdbx_t *rdbx, int delta);
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/*
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* rdbx_set_roc(rdbx, roc) initalizes the rdbx_t at the location rdbx
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* to have the rollover counter value roc. If that value is less than
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* the current rollover counter value, then the function returns
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* err_status_replay_old; otherwise, err_status_ok is returned.
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*
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*/
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err_status_t
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rdbx_set_roc(rdbx_t *rdbx, uint32_t roc);
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/*
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* rdbx_get_roc(rdbx) returns the value of the rollover counter for
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* the rdbx_t pointed to by rdbx
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*
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*/
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xtd_seq_num_t
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rdbx_get_packet_index(const rdbx_t *rdbx);
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/*
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* xtd_seq_num_t functions - these are *internal* functions of rdbx, and
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* shouldn't be used to manipulate rdbx internal values. use the rdbx
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* api instead!
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*/
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/*
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* rdbx_get_ws(rdbx_ptr)
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*
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* gets the window size which was used to initialize the rdbx
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*/
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unsigned long
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rdbx_get_window_size(const rdbx_t *rdbx);
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/* index_init(&pi) initializes a packet index pi (sets it to zero) */
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void
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index_init(xtd_seq_num_t *pi);
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/* index_advance(&pi, s) advances a xtd_seq_num_t forward by s */
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void
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index_advance(xtd_seq_num_t *pi, sequence_number_t s);
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/*
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* index_guess(local, guess, s)
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*
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* given a xtd_seq_num_t local (which represents the highest
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* known-to-be-good index) and a sequence number s (from a newly
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* arrived packet), sets the contents of *guess to contain the best
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* guess of the packet index to which s corresponds, and returns the
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* difference between *guess and *local
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*/
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int
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index_guess(const xtd_seq_num_t *local,
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xtd_seq_num_t *guess,
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sequence_number_t s);
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#endif /* RDBX_H */
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