epan/dissectors/packet-at.c

   1 /* packet-at.c
   2  * Dissector for AT Commands
   3  *
   4  * Copyright 2011, Tyson Key <tyson.key@gmail.com>
   5  *
   6  * $Id$
   7  *
   8  * Wireshark - Network traffic analyzer
   9  * By Gerald Combs <gerald@wireshark.org>
  10  * Copyright 1998 Gerald Combs
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  25  *
  26  */
  27
  28 #include "config.h"
  29
  30 #include <glib.h>
  31 #include <epan/packet.h>
  32 #include <ctype.h>
  33
  34 void proto_register_at_command(void);
  35 void proto_reg_handoff_at_command(void);
  36
  37 static int proto_at = -1;
  38 static int hf_at_command = -1;
  39
  40 /* Forward-declare the dissector functions */
  41 static void dissect_at(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree);
  42
  43 /* Subtree handles: set by register_subtree_array */
  44 static gint ett_at = -1;
  45
  46 static gboolean allowed_chars(tvbuff_t *tvb)
  47 {
  48     gint offset, len;
  49     guint8 val;
  50
  51     len = tvb_length(tvb);
  52     for (offset = 0; offset < len; offset++) {
  53         val = tvb_get_guint8(tvb, offset);
  54         if (!(isprint(val) || (val == 0x0a) || (val == 0x0d)))
  55             return (FALSE);
  56     }
  57     return (TRUE);
  58 }
  59
  60 /* Experimental approach based upon the one used for PPP */
  61 static gboolean heur_dissect_at(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
  62 {
  63     const gchar at_magic1[2] = {0x0d, 0x0a};
  64     const gchar at_magic2[3] = {0x0d, 0x0d, 0x0a};
  65     const gchar at_magic3[2] = {'A', 'T'};
  66
  67     if (((tvb_memeql(tvb, 0, at_magic1, sizeof(at_magic1)) == 0) ||
  68          (tvb_memeql(tvb, 0, at_magic2, sizeof(at_magic2)) == 0) ||
  69          (tvb_memeql(tvb, 0, at_magic3, sizeof(at_magic3)) == 0)) &&
  70          allowed_chars(tvb)) {
  71         dissect_at(tvb, pinfo, tree);
  72         return (TRUE);
  73     }
  74     return (FALSE);
  75 }
  76
  77 /* The dissector itself */
  78 static void dissect_at(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
  79 {
  80     proto_item *item;
  81     proto_tree *at_tree;
  82     gint len;
  83
  84     len = tvb_reported_length(tvb);
  85     col_append_str(pinfo->cinfo, COL_PROTOCOL, "/AT");
  86     col_append_sep_fstr(pinfo->cinfo, COL_INFO, NULL, "AT Command: %s",
  87         tvb_format_text_wsp(tvb, 0, len));
  88
  89     if (tree) {
  90         /* Start with a top-level item to add everything else to */
  91         item = proto_tree_add_item(tree, proto_at, tvb, 0, -1, ENC_NA);
  92         at_tree = proto_item_add_subtree(item, ett_at);
  93
  94         /* Command */
  95         proto_tree_add_item(at_tree, hf_at_command, tvb, 0, len, ENC_ASCII|ENC_NA);
  96         proto_item_append_text(item, ": %s", tvb_format_text_wsp(tvb, 0, len));
  97     }
  98 }
  99
 100 void
 101 proto_register_at_command(void)
 102 {
 103     static hf_register_info hf[] = {
 104         { &hf_at_command,
 105             { "AT Command", "at.command", FT_STRING, BASE_NONE,
 106               NULL, 0x0, NULL, HFILL }}
 107     };
 108
 109     static gint *ett[] = {
 110         &ett_at
 111     };
 112
 113     proto_at = proto_register_protocol("AT Command", "AT", "at");
 114     proto_register_field_array(proto_at, hf, array_length(hf));
 115     proto_register_subtree_array(ett, array_length(ett));
 116     register_dissector("at", dissect_at, proto_at);
 117 }
 118
 119 /* Handler registration */
 120 void
 121 proto_reg_handoff_at_command(void)
 122 {
 123     heur_dissector_add("usb.bulk", heur_dissect_at, proto_at);
 124     heur_dissector_add("usb.control", heur_dissect_at, proto_at);
 125 }
 126