epan/dissectors/packet-at-ldf.c

   1 /* packet-at-ldf.c
   2  * Dissector for Allied Telesis Loop Detection Frames
   3  *
   4  * Copyright (c) 2021-2024 by Martin Mayer <martin.mayer@m2-it-solutions.de>
   5  *
   6  * Wireshark - Network traffic analyzer
   7  * By Gerald Combs <gerald@wireshark.org>
   8  * Copyright 1998 Gerald Combs
   9  *
  10  * SPDX-License-Identifier: GPL-2.0-or-later
  11  */
  12
  13 #include "config.h"
  14 #include <epan/packet.h>
  15
  16 #define AT_LDF_LLC_CTRL 0xE3
  17
  18 #define AT_LDF_FRAME_LEN 79
  19
  20 void proto_register_at_ldf(void);
  21 void proto_reg_handoff_at_ldf(void);
  22
  23 static dissector_handle_t at_ldf_handle;
  24
  25 static int proto_at_ldf;
  26
  27 /* Fields */
  28 static int hf_at_ldf_version;
  29 static int hf_at_ldf_src_vlan;
  30 static int hf_at_ldf_src_port;
  31 static int hf_at_ldf_ttl;
  32 static int hf_at_ldf_id;
  33 static int hf_at_ldf_text;
  34
  35 static int ett_at_ldf;
  36
  37 static int
  38 dissect_at_ldf(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
  39 {
  40     /*
  41      * Packet description
  42      *
  43      * The frame is an LLC frame (non-SNAP) with DSAP=0, SSAP=0, Control=0xE3.
  44      * Ethernet destination address is the non-existing device address
  45      * with Allied Telesis OUI (00:00:f4:27:71:01).
  46      *
  47      * The payload contains information about protocol version, source VLAN and port,
  48      * TTL, random LDF identifier and an informational text.
  49      */
  50
  51
  52     /* Check if packet is destined to the Allied Telesis test address (00:00:F4:27:71:01) */
  53     uint8_t dst_mac[6] = {0x00, 0x00, 0xF4, 0x27, 0x71, 0x01};
  54     address dst_addr = ADDRESS_INIT_NONE;
  55     set_address(&dst_addr, AT_ETHER, sizeof(dst_mac), &dst_mac);
  56
  57     if(!addresses_equal(&pinfo->dl_dst, &dst_addr))
  58         return 0;
  59
  60     col_set_str(pinfo->cinfo, COL_PROTOCOL, "AT LDF");
  61     col_clear(pinfo->cinfo,COL_INFO);
  62     col_add_fstr(pinfo->cinfo, COL_INFO, "Source VLAN: %u, Port: %u",
  63                     tvb_get_uint16(tvb, 1, ENC_BIG_ENDIAN),
  64                     tvb_get_uint16(tvb, 5, ENC_BIG_ENDIAN));
  65
  66     /* Frame has fixed length, so we can directly set tree and reported length */
  67     tvb_set_reported_length(tvb, AT_LDF_FRAME_LEN);
  68
  69     proto_item *ti = proto_tree_add_item(tree, proto_at_ldf, tvb, 0, AT_LDF_FRAME_LEN, ENC_NA);
  70     proto_tree *at_ldf_tree = proto_item_add_subtree(ti, ett_at_ldf);
  71
  72     int offset = 0;
  73     proto_tree_add_item(at_ldf_tree, hf_at_ldf_version, tvb, offset, 1, ENC_BIG_ENDIAN);
  74     offset += 1;
  75     proto_tree_add_item(at_ldf_tree, hf_at_ldf_src_vlan, tvb, offset, 2, ENC_BIG_ENDIAN);
  76     offset += 2;
  77     proto_tree_add_item(at_ldf_tree, hf_at_ldf_src_port, tvb, offset, 4, ENC_BIG_ENDIAN);
  78     offset += 4;
  79     proto_tree_add_item(at_ldf_tree, hf_at_ldf_ttl, tvb, offset, 1, ENC_BIG_ENDIAN);
  80     offset += 1;
  81     proto_tree_add_item(at_ldf_tree, hf_at_ldf_id, tvb, offset, 7, ENC_NA);
  82     offset += 7;
  83     proto_tree_add_item(at_ldf_tree, hf_at_ldf_text, tvb, offset, 64, ENC_ASCII);
  84
  85     return AT_LDF_FRAME_LEN;
  86 }
  87
  88 void
  89 proto_register_at_ldf(void)
  90 {
  91     static hf_register_info hf[] = {
  92         { &hf_at_ldf_version,
  93             { "Version", "atldf.version",
  94             FT_UINT8, BASE_DEC,
  95             NULL, 0x0,
  96             NULL, HFILL }
  97         },
  98         { &hf_at_ldf_src_vlan,
  99             { "Source VLAN", "atldf.vlan",
 100             FT_UINT16, BASE_DEC,
 101             NULL, 0x0,
 102             NULL, HFILL }
 103         },
 104         { &hf_at_ldf_src_port,
 105             { "Source Port", "atldf.port",
 106             FT_UINT32, BASE_DEC,
 107             NULL, 0x0,
 108             NULL, HFILL }
 109         },
 110         { &hf_at_ldf_ttl,
 111             { "Time to Live", "atldf.ttl",
 112             FT_UINT8, BASE_DEC,
 113             NULL, 0x0,
 114             NULL, HFILL }
 115         },
 116         { &hf_at_ldf_id,
 117             { "Identifier", "atldf.id",
 118             FT_UINT56, BASE_HEX,
 119             NULL, 0x0,
 120             NULL, HFILL }
 121         },
 122         { &hf_at_ldf_text,
 123             { "Information", "atldf.info",
 124             FT_STRINGZPAD, BASE_NONE,
 125             NULL, 0x0,
 126             NULL, HFILL }
 127         }
 128     };
 129
 130     static int *ett[] = {
 131         &ett_at_ldf
 132     };
 133
 134     proto_at_ldf = proto_register_protocol ("Allied Telesis Loop Detection", "AT LDF", "atldf");
 135
 136     proto_register_field_array(proto_at_ldf, hf, array_length(hf));
 137     proto_register_subtree_array(ett, array_length(ett));
 138
 139     at_ldf_handle = register_dissector("atldf", dissect_at_ldf, proto_at_ldf);
 140 }
 141
 142 void
 143 proto_reg_handoff_at_ldf(void)
 144 {
 145     dissector_add_uint("llc.control", AT_LDF_LLC_CTRL, at_ldf_handle);
 146 }
 147
 148 /*
 149  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 150  *
 151  * Local variables:
 152  * c-basic-offset: 4
 153  * tab-width: 8
 154  * indent-tabs-mode: nil
 155  * End:
 156  *
 157  * vi: set shiftwidth=4 tabstop=8 expandtab:
 158  * :indentSize=4:tabSize=8:noTabs=true:
 159  */