/* packet-lsd.c

 * Local Service Discovery packet dissector

 *

 * From http://bittorrent.org/beps/bep_0014.html

 *

 * 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 <epan/packet.h>

#include <epan/expert.h>

#include <epan/strutil.h>

#include <wsutil/pint.h>

#include <wsutil/strtoi.h>

void proto_register_lsd(void);

void proto_reg_handoff_lsd(void);

#define LSD_MULTICAST_ADDRESS 0xEFC0988F /* 239.192.152.143 */

#define LSD_PORT 6771

static int proto_lsd;

static int hf_lsd_header;

static int hf_lsd_host;

static int hf_lsd_port;

static int hf_lsd_infohash;

static int hf_lsd_cookie;

static int ett_lsd;

static expert_field ei_lsd_field;

static bool

parse_string_field(proto_tree *tree, int hf, packet_info *pinfo, tvbuff_t *tvb, unsigned offset, unsigned* next_offset, unsigned* linelen)

{

  const char *str;

  header_field_info* hf_info = proto_registrar_get_nth(hf);

  char **field_and_value;

  proto_item* ti;

  char *p;

  if (!tvb_find_line_end_remaining(tvb, offset, linelen, next_offset))

    return false;

  str = (char*)tvb_get_string_enc(pinfo->pool, tvb, offset, *linelen, ENC_ASCII);

  if (g_ascii_strncasecmp(str, hf_info->name, strlen(hf_info->name)) == 0)

  {

      field_and_value = wmem_strsplit(pinfo->pool, str, ":", 2);

      p = field_and_value[1];

      if (p) {

        while(g_ascii_isspace(*p))

          p++;

        proto_tree_add_string(tree, hf, tvb, offset, *linelen, p);

        return true;

      }

  }

  ti = proto_tree_add_string(tree, hf, tvb, offset, *linelen, str);

  expert_add_info_format(pinfo, ti, &ei_lsd_field, "%s field malformed", hf_info->name);

  return true;

}

static int

dissect_lsd(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)

{

  proto_item *ti = NULL;

  proto_tree *lsd_tree;

  unsigned offset = 0, next_offset = 0, linelen;

  const char *str;

  char **field_and_value;

  uint16_t port;

  bool valid;

  if (!tvb_find_line_end_remaining(tvb, offset, &linelen, &next_offset))

      return 0;

  col_set_str(pinfo->cinfo, COL_PROTOCOL, "LSD");

  col_clear(pinfo->cinfo, COL_INFO);

  /* Create display subtree for the protocol */

  ti = proto_tree_add_item(tree, proto_lsd, tvb, 0, -1, ENC_NA);

  lsd_tree = proto_item_add_subtree(ti, ett_lsd);

  proto_tree_add_item(lsd_tree, hf_lsd_header, tvb, offset, linelen, ENC_ASCII);

  offset = next_offset;

  if (!parse_string_field(lsd_tree, hf_lsd_host, pinfo, tvb, offset, &next_offset, &linelen))

      return offset+linelen;

  offset = next_offset;

  if (!tvb_find_line_end_remaining(tvb, offset, &linelen, &next_offset))

      return offset+linelen;

  str = (char*)tvb_get_string_enc(pinfo->pool, tvb, offset, linelen, ENC_ASCII);

  if (g_ascii_strncasecmp(str, "Port", strlen("Port")) == 0)

  {

    field_and_value = wmem_strsplit(pinfo->pool, str, ":", 2);

    valid = ws_strtou16(field_and_value[1], NULL, &port);

    ti = proto_tree_add_uint(lsd_tree, hf_lsd_port, tvb, offset, linelen, port);

    if (!valid)

    {

      expert_add_info_format(pinfo, ti, &ei_lsd_field, "Port value malformed");

    }

  }

  else

  {

    ti = proto_tree_add_uint(lsd_tree, hf_lsd_port, tvb, offset, 0, 0xFFFF);

    expert_add_info_format(pinfo, ti, &ei_lsd_field, "Port field malformed");

  }

  proto_item_set_len(ti, linelen);

  offset = next_offset;

  if (!parse_string_field(lsd_tree, hf_lsd_infohash, pinfo, tvb, offset, &next_offset, &linelen))

      return offset+linelen;

  offset = next_offset;

  if (!tvb_find_line_end_remaining(tvb, offset, &linelen, &next_offset))

      return offset+linelen;

  /* Cookie is optional */

  if (tvb_strncaseeql(tvb, offset, "cookie", strlen("cookie")) == 0)

  {

    if (!parse_string_field(lsd_tree, hf_lsd_cookie, pinfo, tvb, offset, &next_offset, &linelen))

      return offset+linelen;

  }

  return tvb_captured_length(tvb);

}

static bool

dissect_lsd_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)

{

  if (pinfo->dst.type == AT_IPv4 && pntohu32(pinfo->dst.data) == LSD_MULTICAST_ADDRESS && pinfo->destport == LSD_PORT)

      return (dissect_lsd(tvb, pinfo, tree, data) != 0);

  if (pinfo->dst.type == AT_IPv6 && pinfo->destport == LSD_PORT)

      return (dissect_lsd(tvb, pinfo, tree, data) != 0);

  return false;

}

void

proto_register_lsd(void)

{

  static hf_register_info hf[] = {

    { &hf_lsd_header,

      { "Header", "lsd.header",

        FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }

    },

    { &hf_lsd_host,

      { "Host", "lsd.host",

        FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }

    },

    { &hf_lsd_port,

      { "Port", "lsd.port",

        FT_UINT32, BASE_DEC, NULL, 0, NULL, HFILL }

    },

    { &hf_lsd_infohash,

      { "Infohash", "lsd.infohash",

        FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }

    },

    { &hf_lsd_cookie,

      { "cookie", "lsd.cookie",

        FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }

    },

  };

  static int *ett[] = {

    &ett_lsd,

  };

  static ei_register_info ei[] = {

    { &ei_lsd_field, { "lsd.malformed_field", PI_MALFORMED, PI_ERROR, "Malformed LDS field", EXPFILL }},

  };

  expert_module_t* expert_lsd;

  proto_lsd = proto_register_protocol("Local Service Discovery", "LSD", "lsd");

  proto_register_field_array(proto_lsd, hf, array_length(hf));

  proto_register_subtree_array(ett, array_length(ett));

  expert_lsd = expert_register_protocol(proto_lsd);

  expert_register_field_array(expert_lsd, ei, array_length(ei));

}

void

proto_reg_handoff_lsd(void)

{

    heur_dissector_add( "udp", dissect_lsd_heur, "LSD over UDP", "lsd_udp", proto_lsd, HEURISTIC_ENABLE);

}

/*

 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html

 *

 * Local Variables:

 * c-basic-offset: 2

 * tab-width: 8

 * indent-tabs-mode: nil

 * End:

 *

 * ex: set shiftwidth=2 tabstop=8 expandtab:

 * :indentSize=2:tabSize=8:noTabs=true:

 */