path: root/epan/stream.c

/* stream.c
 *
 * Definititions for handling circuit-switched protocols
 * which are handled as streams, and don't have lengths
 * and IDs such as are required for reassemble.h
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "config.h"

#include <glib.h>
#include <epan/packet.h>
#include <epan/reassemble.h>
#include <epan/stream.h>
#include <epan/tvbuff.h>
#include <wsutil/ws_assert.h>


typedef struct {
    fragment_head *fd_head;          /* the reassembled data, NULL
                                      * until we add the last fragment */
    guint32 pdu_number;              /* Number of this PDU within the stream */

    /* id of this pdu (globally unique) */
    guint32 id;
} stream_pdu_t;


struct stream_pdu_fragment
{
    guint32 len;                     /* the length of this fragment */
    stream_pdu_t *pdu;
    gboolean final_fragment;
};

struct stream {
    /* the key used to add this stream to stream_hash */
    struct stream_key *key;

    /* pdu to add the next fragment to, or NULL if we need to start
     * a new PDU.
     */
    stream_pdu_t *current_pdu;

    /* number of PDUs added to this stream so far */
    guint32 pdu_counter;

    /* the framenumber and offset of the last fragment added;
       used for sanity-checking */
    guint32 lastfrag_framenum;
    guint32 lastfrag_offset;
};


/*****************************************************************************
 *
 * Stream hash
 */

/* key */
typedef struct stream_key {
    /* streams are attached to conversations */
    const struct conversation *conv;
    int p2p_dir;
} stream_key_t;


/* hash func */
static guint stream_hash_func(gconstpointer k)
{
    const stream_key_t *key = (const stream_key_t *)k;

    return (GPOINTER_TO_UINT(key->conv)) ^ key->p2p_dir;
}

/* compare func */
static gboolean stream_compare_func(gconstpointer a,
                             gconstpointer b)
{
    const stream_key_t *key1 = (const stream_key_t *)a;
    const stream_key_t *key2 = (const stream_key_t *)b;
    if( key1 -> p2p_dir != key2 -> p2p_dir)
        return FALSE;

    return (key1 -> conv == key2 -> conv );
}

/* the hash table */
static GHashTable *stream_hash;


/* cleanup reset function, call from stream_cleanup() */
static void cleanup_stream_hash( void ) {
    if( stream_hash != NULL ) {
        g_hash_table_destroy( stream_hash );
        stream_hash = NULL;
    }
}

/* init function, call from stream_init() */
static void init_stream_hash( void ) {
    ws_assert(stream_hash==NULL);
    stream_hash = g_hash_table_new(stream_hash_func,
                                   stream_compare_func);
}

/* lookup function, returns null if not found */
static stream_t *stream_hash_lookup( const struct conversation *conv, int p2p_dir )
{
    stream_key_t key;
    key.conv = conv;
    key.p2p_dir=p2p_dir;
    return (stream_t *)g_hash_table_lookup(stream_hash, &key);
}


static stream_t *new_stream( stream_key_t *key )
{
    stream_t *val;

    val = wmem_new(wmem_file_scope(), stream_t);
    val -> key = key;
    val -> pdu_counter = 0;
    val -> current_pdu = NULL;
    val -> lastfrag_framenum = 0;
    val -> lastfrag_offset = 0;
    g_hash_table_insert(stream_hash, key, val);

    return val;
}


/* insert function */
static stream_t *stream_hash_insert( const struct conversation *conv, int p2p_dir )
{
    stream_key_t *key;

    key = wmem_new(wmem_file_scope(), stream_key_t);
    key->conv = conv;
    key->p2p_dir = p2p_dir;

    return new_stream(key);
}


/******************************************************************************
 *
 * PDU data
 */

/* pdu counter, for generating unique pdu ids */
static guint32 pdu_counter;

static void stream_cleanup_pdu_data(void)
{
}

static void stream_init_pdu_data(void)
{
    pdu_counter = 0;
}


/* new pdu in this stream */
static stream_pdu_t *stream_new_pdu(stream_t *stream)
{
    stream_pdu_t *pdu;
    pdu = wmem_new(wmem_file_scope(), stream_pdu_t);
    pdu -> fd_head = NULL;
    pdu -> pdu_number = stream -> pdu_counter++;
    pdu -> id = pdu_counter++;
    return pdu;
}

/*****************************************************************************
 *
 * fragment hash
 */

/* key */
typedef struct fragment_key {
    const stream_t *stream;
    guint32 framenum;
    guint32 offset;
} fragment_key_t;


/* hash func */
static guint fragment_hash_func(gconstpointer k)
{
    const fragment_key_t *key = (const fragment_key_t *)k;
    return (GPOINTER_TO_UINT(key->stream)) + ((guint)key -> framenum) + ((guint)key->offset);
}

/* compare func */
static gboolean fragment_compare_func(gconstpointer a,
                               gconstpointer b)
{
    const fragment_key_t *key1 = (const fragment_key_t *)a;
    const fragment_key_t *key2 = (const fragment_key_t *)b;
    return (key1 -> stream == key2 -> stream &&
            key1 -> framenum == key2 -> framenum &&
            key1 -> offset == key2 -> offset );
}

/* the hash table */
static GHashTable *fragment_hash;


/* cleanup function, call from stream_cleanup() */
static void cleanup_fragment_hash( void ) {
    if( fragment_hash != NULL ) {
        g_hash_table_destroy( fragment_hash );
        fragment_hash = NULL;
    }
}

/* init function, call from stream_init() */
static void init_fragment_hash( void ) {
    ws_assert(fragment_hash==NULL);
    fragment_hash = g_hash_table_new(fragment_hash_func,
                                     fragment_compare_func);
}


/* lookup function, returns null if not found */
static stream_pdu_fragment_t *fragment_hash_lookup( const stream_t *stream, guint32 framenum, guint32 offset )
{
    fragment_key_t key;
    stream_pdu_fragment_t *val;

    key.stream = stream;
    key.framenum = framenum;
    key.offset = offset;
    val = (stream_pdu_fragment_t *)g_hash_table_lookup(fragment_hash, &key);

    return val;
}


/* insert function */
static stream_pdu_fragment_t *fragment_hash_insert( const stream_t *stream, guint32 framenum, guint32 offset,
                                                    guint32 length)
{
    fragment_key_t *key;
    stream_pdu_fragment_t *val;

    key = wmem_new(wmem_file_scope(), fragment_key_t);
    key->stream = stream;
    key->framenum = framenum;
    key->offset = offset;

    val = wmem_new(wmem_file_scope(), stream_pdu_fragment_t);
    val->len = length;
    val->pdu = NULL;
    val->final_fragment = FALSE;

    g_hash_table_insert(fragment_hash, key, val);
    return val;
}

/*****************************************************************************/

/* reassembly table */
static reassembly_table stream_reassembly_table;

/* Initialise a new stream. Call this when you first identify a distinct
 * stream. */
stream_t *stream_new ( const struct conversation *conv, int p2p_dir )
{
    stream_t * stream;

    /* we don't want to replace the previous data if we get called twice on the
       same conversation, so do a lookup first */
    stream = stream_hash_lookup(conv, p2p_dir);
    DISSECTOR_ASSERT( stream == NULL );

    stream = stream_hash_insert(conv, p2p_dir);
    return stream;
}


/* retrieve a previously-created stream.
 *
 * Returns null if no matching stream was found.
 */
stream_t *find_stream ( const struct conversation *conv, int p2p_dir )
{
    return stream_hash_lookup(conv,p2p_dir);
}

/* cleanup the stream routines */
/* Note: stream_cleanup must only be called when seasonal memory
 *       is also freed since the hash tables countain pointers to
 *       wmem_file_scoped memory.
 */
void stream_cleanup( void )
{
    cleanup_stream_hash();
    cleanup_fragment_hash();
    stream_cleanup_pdu_data();
    reassembly_table_destroy(&stream_reassembly_table);
}

/* initialise the stream routines */
void stream_init( void )
{
    init_stream_hash();
    init_fragment_hash();
    stream_init_pdu_data();

    reassembly_table_init(&stream_reassembly_table,
                          &addresses_reassembly_table_functions);
}

/*****************************************************************************/

stream_pdu_fragment_t *stream_find_frag( stream_t *stream, guint32 framenum, guint32 offset )
{
    return fragment_hash_lookup( stream, framenum, offset );
}

stream_pdu_fragment_t *stream_add_frag( stream_t *stream, guint32 framenum, guint32 offset,
                                        tvbuff_t *tvb, packet_info *pinfo, gboolean more_frags )
{
    fragment_head *fd_head;
    stream_pdu_t *pdu;
    stream_pdu_fragment_t *frag_data;

    DISSECTOR_ASSERT(stream);

    /* check that this fragment is at the end of the stream */
    DISSECTOR_ASSERT( framenum > stream->lastfrag_framenum ||
                      (framenum == stream->lastfrag_framenum && offset > stream->lastfrag_offset));


    pdu = stream->current_pdu;
    if( pdu == NULL ) {
        /* start a new pdu */
        pdu = stream->current_pdu = stream_new_pdu(stream);
    }

    /* add it to the reassembly tables */
    fd_head = fragment_add_seq_next(&stream_reassembly_table,
                                    tvb, 0, pinfo, pdu->id, NULL,
                                    tvb_reported_length(tvb), more_frags);
    /* add it to our hash */
    frag_data = fragment_hash_insert( stream, framenum, offset, tvb_reported_length(tvb));
    frag_data -> pdu = pdu;

    if( fd_head != NULL ) {
        /* if this was the last fragment, update the pdu data.
         */
        pdu -> fd_head = fd_head;

        /* start a new pdu next time */
        stream->current_pdu = NULL;

        frag_data -> final_fragment = TRUE;
    }

    /* stashing the framenum and offset permit future sanity checks */
    stream -> lastfrag_framenum = framenum;
    stream -> lastfrag_offset = offset;

    return frag_data;
}


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,
    gboolean *update_col_infop, proto_tree *tree)
{
    stream_pdu_t *pdu;
    DISSECTOR_ASSERT(frag);
    pdu = frag->pdu;

    /* we handle non-terminal fragments ourselves, because
       reassemble.c messes them up */
    if(!frag->final_fragment) {
        if (pdu->fd_head != NULL && fit->hf_reassembled_in != NULL) {
            proto_tree_add_uint(tree,
                                *(fit->hf_reassembled_in), tvb,
                                0, 0, pdu->fd_head->reassembled_in);
        }
        return NULL;
    }

    return process_reassembled_data(tvb, offset, pinfo, name, pdu->fd_head,
                                    fit, update_col_infop, tree);
}

guint32 stream_get_frag_length( const stream_pdu_fragment_t *frag)
{
    DISSECTOR_ASSERT( frag );
    return frag->len;
}

fragment_head *stream_get_frag_data( const stream_pdu_fragment_t *frag)
{
    DISSECTOR_ASSERT( frag );
    return frag->pdu->fd_head;
}

guint32 stream_get_pdu_no( const stream_pdu_fragment_t *frag)
{
    DISSECTOR_ASSERT( frag );
    return frag->pdu->pdu_number;
}

/*
 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 *
 * Local variables:
 * c-basic-offset: 4
 * tab-width: 8
 * indent-tabs-mode: nil
 * End:
 *
 * vi: set shiftwidth=4 tabstop=8 expandtab:
 * :indentSize=4:tabSize=8:noTabs=true:
 */