stream.h

Go to the documentation of this file.

 
#ifndef STREAM_H
#define STREAM_H
 
#include <epan/tvbuff.h>
#include <epan/reassemble.h>
#include "ws_symbol_export.h"
 
struct _fragment_items;
 
/* A stream represents the concept of an arbitrary stream of data,
   divided up into frames for transmission, where the frames have
   little or no correspondence to the PDUs of the protocol being
   streamed, and those PDUs are just delineated by a magic number.
 
   For example, we stream H.223 over IAX2. IAX2 has no concept of
   H.223 PDUs and just divides the H.223 stream into 160-byte
   frames. H.223 PDUs are delineated by two-byte magic numbers (which
   may, of course, straddle an IAX2 frame boundary).
 
   Essentially we act as a wrapper to reassemble.h, by making up
   PDU ids and keeping some additional data on fragments to allow the
   PDUs to be defragmented again.
*/
 
 
/* A stream_t represents a stream. There might be one or two streams
   in a circuit, depending on whether that circuit is mono- or bi-directional.
*/
typedef struct stream stream_t;
 
/* Fragments in a PDU are represented using a stream_pdu_fragment_t,
   and placed in a linked-list with other fragments in the PDU.
 
   (They're also placed in a hash so we can find them again later)
*/
typedef struct stream_pdu_fragment stream_pdu_fragment_t;
 
 
struct conversation;
 
/* initialise a new stream. Call this when you first identify a distinct
 * stream. The conversation pointer is just used as a key to look up the stream.
 */
WS_DLL_PUBLIC stream_t *stream_new ( const struct conversation *conv, int p2p_dir );
 
/* retrieve a previously-created stream.
 *
 * Returns null if no matching stream was found.
 */
WS_DLL_PUBLIC stream_t *find_stream ( const struct conversation *conv, int p2p_dir );
 
 
 
/* see if we've seen this fragment before.
 
   The framenum and offset are just hash keys, so can be any values unique
   to this frame, but the idea is that you use the number of the frame being
   disassembled, and the byte-offset within that frame.
*/
WS_DLL_PUBLIC stream_pdu_fragment_t *stream_find_frag( stream_t *stream, uint32_t framenum, uint32_t offset );
 
/* add a new fragment to the fragment tables for the stream. The framenum and
 * offset are keys allowing future access with stream_find_frag(), tvb is the
 * fragment to be added, and pinfo is the information for the frame containing
 * this fragment. more_frags should be set if this is the final fragment in the
 * PDU.
 *
 * * the fragment must be later in the stream than any previous fragment
 *   (ie, framenum.offset must be greater than those passed on the previous
 *   call)
 *
 * This essentially means that you can only add fragments on the first pass
 * through the stream.
 */
WS_DLL_PUBLIC stream_pdu_fragment_t *stream_add_frag( stream_t *stream, uint32_t framenum, uint32_t offset,
                    tvbuff_t *tvb, packet_info *pinfo, bool more_frags );
 
/* Get the length of a fragment previously found by stream_find_frag().
 */
extern uint32_t stream_get_frag_length( const stream_pdu_fragment_t *frag);
 
/* Get a handle on the top of the chain of fragment_datas underlying this PDU
 * frag can be any fragment within a PDU, and it will always return the head of
 * the chain
 *
 * Returns NULL until the last fragment is added.
 */
extern fragment_head *stream_get_frag_data( const stream_pdu_fragment_t *frag);
 
/*
 * Process reassembled data; if this is the last fragment, put the fragment
 * information into the protocol tree, and construct a tvbuff with the
 * reassembled data, otherwise just put a "reassembled in" item into the
 * protocol tree.
 */
WS_DLL_PUBLIC tvbuff_t *stream_process_reassembled(
    tvbuff_t *tvb, int offset, packet_info *pinfo,
    const char *name, const stream_pdu_fragment_t *frag,
    const struct _fragment_items *fit,
    bool *update_col_infop, proto_tree *tree);
 
/* Get the PDU number. PDUs are numbered from zero within a stream.
 * frag can be any fragment within a PDU.
 */
extern uint32_t stream_get_pdu_no( const stream_pdu_fragment_t *frag);
 
/* initialise the stream routines */
void stream_init( void );
void stream_cleanup( void );
 
#endif /* STREAM_H */