epan/stream.h

   1 /** @file
   2  *
   3  * Definititions for handling circuit-switched protocols
   4  * which are handled as streams, and don't have lengths
   5  * and IDs such as are required for reassemble.h
   6  *
   7  * Wireshark - Network traffic analyzer
   8  * By Gerald Combs <gerald@wireshark.org>
   9  * Copyright 1998 Gerald Combs
  10  *
  11  * SPDX-License-Identifier: GPL-2.0-or-later
  12  */
  13
  14 #ifndef STREAM_H
  15 #define STREAM_H
  16
  17 #include <epan/tvbuff.h>
  18 #include <epan/reassemble.h>
  19 #include "ws_symbol_export.h"
  20
  21 struct _fragment_items;
  22
  23 /* A stream represents the concept of an arbitrary stream of data,
  24    divided up into frames for transmission, where the frames have
  25    little or no correspondence to the PDUs of the protocol being
  26    streamed, and those PDUs are just delineated by a magic number.
  27
  28    For example, we stream H.223 over IAX2. IAX2 has no concept of
  29    H.223 PDUs and just divides the H.223 stream into 160-byte
  30    frames. H.223 PDUs are delineated by two-byte magic numbers (which
  31    may, of course, straddle an IAX2 frame boundary).
  32
  33    Essentially we act as a wrapper to reassemble.h, by making up
  34    PDU ids and keeping some additional data on fragments to allow the
  35    PDUs to be defragmented again.
  36 */
  37
  38
  39 /* A stream_t represents a stream. There might be one or two streams
  40    in a circuit, depending on whether that circuit is mono- or bi-directional.
  41 */
  42 typedef struct stream stream_t;
  43
  44 /* Fragments in a PDU are represented using a stream_pdu_fragment_t,
  45    and placed in a linked-list with other fragments in the PDU.
  46
  47    (They're also placed in a hash so we can find them again later)
  48 */
  49 typedef struct stream_pdu_fragment stream_pdu_fragment_t;
  50
  51
  52 struct conversation;
  53
  54 /* initialise a new stream. Call this when you first identify a distinct
  55  * stream. The conversation pointer is just used as a key to look up the stream.
  56  */
  57 WS_DLL_PUBLIC stream_t *stream_new ( const struct conversation *conv, int p2p_dir );
  58
  59 /* retrieve a previously-created stream.
  60  *
  61  * Returns null if no matching stream was found.
  62  */
  63 WS_DLL_PUBLIC stream_t *find_stream ( const struct conversation *conv, int p2p_dir );
  64
  65
  66
  67 /* see if we've seen this fragment before.
  68
  69    The framenum and offset are just hash keys, so can be any values unique
  70    to this frame, but the idea is that you use the number of the frame being
  71    disassembled, and the byte-offset within that frame.
  72 */
  73 WS_DLL_PUBLIC stream_pdu_fragment_t *stream_find_frag( stream_t *stream, uint32_t framenum, uint32_t offset );
  74
  75 /* add a new fragment to the fragment tables for the stream. The framenum and
  76  * offset are keys allowing future access with stream_find_frag(), tvb is the
  77  * fragment to be added, and pinfo is the information for the frame containing
  78  * this fragment. more_frags should be set if this is the final fragment in the
  79  * PDU.
  80  *
  81  * * the fragment must be later in the stream than any previous fragment
  82  *   (ie, framenum.offset must be greater than those passed on the previous
  83  *   call)
  84  *
  85  * This essentially means that you can only add fragments on the first pass
  86  * through the stream.
  87  */
  88 WS_DLL_PUBLIC stream_pdu_fragment_t *stream_add_frag( stream_t *stream, uint32_t framenum, uint32_t offset,
  89                                         tvbuff_t *tvb, packet_info *pinfo, bool more_frags );
  90
  91 /* Get the length of a fragment previously found by stream_find_frag().
  92  */
  93 extern uint32_t stream_get_frag_length( const stream_pdu_fragment_t *frag);
  94
  95 /* Get a handle on the top of the chain of fragment_datas underlying this PDU
  96  * frag can be any fragment within a PDU, and it will always return the head of
  97  * the chain
  98  *
  99  * Returns NULL until the last fragment is added.
 100  */
 101 extern fragment_head *stream_get_frag_data( const stream_pdu_fragment_t *frag);
 102
 103 /*
 104  * Process reassembled data; if this is the last fragment, put the fragment
 105  * information into the protocol tree, and construct a tvbuff with the
 106  * reassembled data, otherwise just put a "reassembled in" item into the
 107  * protocol tree.
 108  */
 109 WS_DLL_PUBLIC tvbuff_t *stream_process_reassembled(
 110     tvbuff_t *tvb, int offset, packet_info *pinfo,
 111     const char *name, const stream_pdu_fragment_t *frag,
 112     const struct _fragment_items *fit,
 113     bool *update_col_infop, proto_tree *tree);
 114
 115 /* Get the PDU number. PDUs are numbered from zero within a stream.
 116  * frag can be any fragment within a PDU.
 117  */
 118 extern uint32_t stream_get_pdu_no( const stream_pdu_fragment_t *frag);
 119
 120 /* initialise the stream routines */
 121 void stream_init( void );
 122 void stream_cleanup( void );
 123
 124 #endif /* STREAM_H */