GSM-R protocol dissector

Dissector for GSM-R protocol. Specification ETSI TS 102 610.
Trace example in https://wiki.wireshark.org/SampleCaptures [[attachment:gsm-r.uus1.pcap]]

Change-Id: I7496bfa141d75b3460f7c3bdbb791e24d4810231
Reviewed-on: https://code.wireshark.org/review/26929
Petri-Dish: Anders Broman <a.broman58@gmail.com>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>

1 files changed, 934 insertions, 0 deletions

diff --git a/epan/dissectors/packet-gsm_r_uus1.c b/epan/dissectors/packet-gsm_r_uus1.c
new file mode 100644
index 0000000000..faa3d6a55a
--- /dev/null
+++ b/epan/dissectors/packet-gsm_r_uus1.c
@@ -0,0 +1,934 @@
+/* packet-gsm_r_uus1.c
+ * Routines for GSM-R UUS1 dissection
+ *
+ * Copyright 2018, Michail Koreshkov <michail.koreshkov [at] bk.ru
+ *
+ * Reference [1]
+ * Railways Telecommunications (RT);
+ * Global System for Mobile communications (GSM);
+ * Usage of the User-to-User Information Element
+ * for GSM Operation on Railways
+ * (ETSI TS 102 610 V1.2.0 (2012-08))
+ *
+ * Reference [2]
+ * EIRENE SRS: "UIC Project EIRENE System Requirements Specification".
+ *
+ * Reference [3]
+ * MORANE F 10 T 6003 4: "FFFS for Presentation of Functional Numbers
+ * to Called and Calling Parties".
+ *
+ * Reference [4]
+ * eLDA IRS (V5.0): "Interface Requirements Specification
+ * enhanced Location Dependent Addressing".
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "config.h"
+
+#include <epan/packet.h>
+#include <epan/expert.h>
+#include <epan/tap.h>
+#include <epan/prefs.h>
+#include <epan/strutil.h>
+
+/* forward reference */
+void proto_register_gsm_r_uus1(void);
+void proto_reg_handoff_gsm_r_uus1(void);
+
+
+/* Initialize the protocol and registered fields */
+static int proto_gsm_r_uus1 = -1;
+
+static int hf_gsm_r_uus1_elem_tag                    = -1;
+static int hf_gsm_r_uus1_elem_len                    = -1;
+static int hf_gsm_r_uus1_pfn                         = -1;
+static int hf_gsm_r_uus1_pfn_digits                  = -1;
+
+/* 5.2 and 5.3 */
+static int hf_gsm_r_uus1_chpc                        = -1;
+static int hf_gsm_r_uus1_chpc_t_dur                  = -1;
+static int hf_gsm_r_uus1_chpc_t_rel                  = -1;
+static int hf_gsm_r_uus1_chpc_pl_call                = -1;
+static int hf_gsm_r_uus1_chpc_cause                  = -1;
+static int hf_gsm_r_uus1_chpc_cause_power            = -1;
+static int hf_gsm_r_uus1_chpc_cause_radio            = -1;
+static int hf_gsm_r_uus1_chpc_cause_reserved3        = -1;
+static int hf_gsm_r_uus1_chpc_cause_reserved4        = -1;
+static int hf_gsm_r_uus1_chpc_cause_user_command     = -1;
+static int hf_gsm_r_uus1_chpc_cause_reserved6        = -1;
+static int hf_gsm_r_uus1_chpc_cause_reserved7        = -1;
+static int hf_gsm_r_uus1_chpc_cause_reserved8        = -1;
+static int hf_gsm_r_uus1_chpc_gref                   = -1;
+static int hf_gsm_r_uus1_chpc_ack_cause              = -1;
+
+/* 5.4 */
+static int hf_gsm_r_uus1_epfn                        = -1;
+
+/* 5.5 */
+static int hf_gsm_r_uus1_present_text_str            = -1;
+
+/* 5.6 */
+static int hf_gsm_r_uus1_elda          = -1;
+static int hf_gsm_r_uus1_elda_lat      = -1;
+static int hf_gsm_r_uus1_elda_lat_deg  = -1;
+static int hf_gsm_r_uus1_elda_lat_min  = -1;
+static int hf_gsm_r_uus1_elda_lat_sec  = -1;
+static int hf_gsm_r_uus1_elda_lat_hem  = -1;
+static int hf_gsm_r_uus1_elda_long     = -1;
+static int hf_gsm_r_uus1_elda_long_deg = -1;
+static int hf_gsm_r_uus1_elda_long_min = -1;
+static int hf_gsm_r_uus1_elda_long_sec = -1;
+static int hf_gsm_r_uus1_elda_long_hem = -1;
+static int hf_gsm_r_uus1_elda_height   = -1;
+static int hf_gsm_r_uus1_elda_speed    = -1;
+static int hf_gsm_r_uus1_elda_heading  = -1;
+static int hf_gsm_r_uus1_elda_e_time   = -1;
+static int hf_gsm_r_uus1_elda_distance = -1;
+static int hf_gsm_r_uus1_elda_scale    = -1;
+static int hf_gsm_r_uus1_elda_spare    = -1;
+
+/* 5.7 */
+static int hf_gsm_r_uus1_present_dsd_alarm               = -1;
+static int hf_gsm_r_uus1_present_dsd_alarm_loco_number   = -1;
+
+/* 5.8 */
+static int hf_gsm_r_uus1_alert_controller        = -1;
+static int hf_gsm_r_uus1_alert_controller_gref   = -1;
+
+/* Initialize the subtree pointers */
+static gint ett_gsm_r_uus1                   = -1;
+static gint ett_gsm_r_uus1_pfn               = -1;
+static gint ett_gsm_r_uus1_chpc              = -1;
+static gint ett_gsm_r_uus1_chpc_cause        = -1;
+static gint ett_gsm_r_uus1_epfn              = -1;
+static gint ett_gsm_r_uus1_present_text_str  = -1;
+static gint ett_gsm_r_uus1_elda              = -1;
+static gint ett_gsm_r_uus1_elda_lat          = -1;
+static gint ett_gsm_r_uus1_elda_long         = -1;
+static gint ett_gsm_r_uus1_present_dsd_alarm = -1;
+static gint ett_gsm_r_uus1_alert_controller  = -1;
+
+
+/* Preferences */
+static gboolean q931_u2u  = FALSE;
+static gboolean gsm_a_u2u = TRUE;
+
+
+static expert_field ei_gsm_r_uus1_not_implemented_yet = EI_INIT;
+
+const value_string gsm_r_uus1_tags[] = {
+    { 2,  "Acknowledgement by Receiver of a HPC and response from device accepting the acknowledgement" },
+    { 3,  "Acknowledgement by Initiator of a HPC" },
+    { 5,  "Presentation of Functional Number" },
+    { 6,  "enhanced Location Dependent Addressing" },
+    { 7,  "enhanced Location Dependent Addressing (Reserved for future use)" },
+    { 8,  "enhanced Location Dependent Addressing (Reserved for future use)" },
+    { 9,  "ePFN Information" },
+    { 10, "User specific plain text according to alphabet indicator" },
+    { 11, "DSD Alarm Notification" },
+    { 12, "Alerting of a Controller Notification and Response" },
+    { 0, NULL }
+};
+
+
+/*
+ * 5.1 Presentation of functional number
+ *
+ */
+static guint16
+de_gsm_r_uus1_pfn(tvbuff_t *tvb, proto_tree *tree, guint32 offset)
+{
+    guint32	curr_offset;
+    guint32	len;
+    const gchar *fn_str;
+    proto_item *item;
+    proto_tree *sub_tree;
+
+    curr_offset = offset;
+
+    len = tvb_get_guint8(tvb, offset+1);
+
+    item = proto_tree_add_item(tree, hf_gsm_r_uus1_pfn, tvb, curr_offset, len+2, ENC_NA);
+    sub_tree = proto_item_add_subtree(item, ett_gsm_r_uus1_pfn);
+
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_tag, tvb, curr_offset, 1, ENC_NA);
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_len, tvb, curr_offset+1, 1, ENC_NA);
+    curr_offset += 2;
+
+    if(len == 0) {
+        proto_item_append_text(item, ": No FN Available");
+    }else {
+        fn_str = tvb_bcd_dig_to_wmem_packet_str(tvb, offset+2, len, NULL, FALSE);
+        proto_tree_add_string(sub_tree, hf_gsm_r_uus1_pfn_digits, tvb, curr_offset, len, fn_str);
+        proto_item_append_text(item, ": %s", fn_str);
+
+        curr_offset += len;
+    }
+
+    return (curr_offset - offset);
+}
+
+
+/*
+ * 5.2 Confirmation of High Priority Calls
+ *
+ */
+static const range_string gsm_r_uus1_chpc_priority_vals[] = {
+    { 0x00, 0x00, "no priority specified in call"},
+    { 0x01, 0x01, "eMLPP priority of 4 (Railway Information)"},
+    { 0x02, 0x02, "eMLPP priority of 3 (Railway Operation)"},
+    { 0x03, 0x03, "eMLPP priority of 2 (Public Emergency/Group Calls)"},
+    { 0x04, 0x04, "eMLPP priority of 1 (Command and Control)"},
+    { 0x05, 0x05, "eMLPP priority of 0 (Railway Emergency)"},
+    { 0x06, 0x07, "unknown" },
+    { 0, 0, NULL }
+};
+
+static guint16
+de_gsm_r_uus1_chpc_forward(tvbuff_t *tvb, proto_tree *tree, guint32 offset)
+{
+    guint32	curr_offset;
+    guint32	len;
+    guint32 t_dur;
+    guint32 t_rel;
+    const gchar *gref_str;
+    proto_item *item;
+    proto_tree *sub_tree;
+
+    curr_offset = offset;
+
+    len = tvb_get_guint8(tvb, offset+1);
+
+    item = proto_tree_add_item(tree, hf_gsm_r_uus1_chpc, tvb, curr_offset, len+2, ENC_NA);
+    sub_tree = proto_item_add_subtree(item, ett_gsm_r_uus1_chpc);
+
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_tag, tvb, curr_offset, 1, ENC_NA);
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_len, tvb, curr_offset+1, 1, ENC_NA);
+    curr_offset += 2;
+
+    t_dur = tvb_get_guint24(tvb, curr_offset, ENC_LITTLE_ENDIAN);
+    proto_tree_add_uint_format_value(sub_tree, hf_gsm_r_uus1_chpc_t_dur, tvb, curr_offset, 3, t_dur, "%d ms", t_dur*100);
+    curr_offset += 3;
+
+    t_rel = tvb_get_guint32(tvb, curr_offset, ENC_LITTLE_ENDIAN);
+    proto_tree_add_uint_format_value(sub_tree, hf_gsm_r_uus1_chpc_t_rel, tvb, curr_offset, 4, t_rel, "%d ms", t_rel*100);
+    curr_offset += 4;
+
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_chpc_pl_call, tvb, curr_offset, 1, ENC_NA);
+    curr_offset += 1;
+
+    static const int * cause_flags[] = {
+        &hf_gsm_r_uus1_chpc_cause_power,
+        &hf_gsm_r_uus1_chpc_cause_radio,
+        &hf_gsm_r_uus1_chpc_cause_reserved3,
+        &hf_gsm_r_uus1_chpc_cause_reserved4,
+        &hf_gsm_r_uus1_chpc_cause_user_command,
+        &hf_gsm_r_uus1_chpc_cause_reserved6,
+        &hf_gsm_r_uus1_chpc_cause_reserved7,
+        &hf_gsm_r_uus1_chpc_cause_reserved8,
+        NULL
+    };
+
+    proto_tree_add_bitmask(sub_tree, tvb, curr_offset, hf_gsm_r_uus1_chpc_cause, ett_gsm_r_uus1_chpc_cause, cause_flags, ENC_NA);
+    curr_offset += 1;
+
+    gref_str = tvb_bcd_dig_to_wmem_packet_str(tvb, curr_offset, 4, NULL, FALSE);
+    proto_tree_add_string(sub_tree, hf_gsm_r_uus1_chpc_gref, tvb, curr_offset, 4, gref_str);
+    curr_offset += 4;
+
+    return (curr_offset - offset);
+}
+
+/*
+ * 5.3 CHPC tag definition for collecting network device
+ *
+ * The tag is included in a RELEASE_COMPLETE message
+ * which shall have the release cause value of "Normal Call Clearing".
+ *
+ * gsm_a.dtap.msg_cc_type == 0x2a
+ */
+static const range_string gsm_r_uus1_chpc_ack_cause_vals[] = {
+    { 0x00, 0x00, "ACK (no error)" },
+    { 0x01, 0x01, "NACK-1 (error, repetition should take place)" },
+    { 0x02, 0x7f, "Reserved for internal use" },
+    { 0x80, 0x80, "NACK-2 (fatal error, NO repetition to take place)" },
+    { 0x81, 0xff, "Reserved" },
+    { 0, 0, NULL }
+};
+
+static guint16
+de_gsm_r_uus1_chpc_collect(tvbuff_t *tvb, proto_tree *tree, guint32 offset)
+{
+    proto_item *item;
+    proto_tree *sub_tree;
+
+    item = proto_tree_add_item(tree, hf_gsm_r_uus1_chpc, tvb, offset, 2, ENC_NA);
+    proto_item_set_text(item, "CHPC for collecting network device");
+    sub_tree = proto_item_add_subtree(item, ett_gsm_r_uus1_chpc);
+
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_tag, tvb, offset, 1, ENC_NA);
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_chpc_ack_cause, tvb, offset+1, 1, ENC_NA);
+
+    return 2;
+}
+
+/*
+ * Type of field depends on BSSAP message type. SETUP or RELEASE_COMPLETE
+ * But I don't know how to verify message type.
+ * That is why use length variable to find type of field
+ */
+static guint16
+de_gsm_r_uus1_chpc(tvbuff_t *tvb, proto_tree *tree, guint32 offset)
+{
+    guint8 field_length;
+    field_length = tvb_get_guint8(tvb, offset+1);
+    if(field_length == 13)
+        return de_gsm_r_uus1_chpc_forward(tvb, tree, offset);
+    else
+        return de_gsm_r_uus1_chpc_collect(tvb, tree, offset);
+}
+
+/*
+ * 5.4 Enhanced presentation of functional number
+ * (not implemented now)
+ */
+static guint16
+de_gsm_r_uus1_epfn(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo, guint32 offset)
+{
+    guint32	curr_offset;
+    guint32	len;
+    proto_item *item;
+    proto_tree *sub_tree;
+
+    curr_offset = offset;
+
+    len = tvb_get_guint8(tvb, offset+1);
+
+    item = proto_tree_add_item(tree, hf_gsm_r_uus1_epfn, tvb, curr_offset, len+2, ENC_NA);
+    sub_tree = proto_item_add_subtree(item, ett_gsm_r_uus1_epfn);
+
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_tag, tvb, curr_offset, 1, ENC_NA);
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_len, tvb, curr_offset+1, 1, ENC_NA);
+    curr_offset += 2;
+
+    proto_tree_add_expert(sub_tree, pinfo, &ei_gsm_r_uus1_not_implemented_yet, tvb, curr_offset, len);
+    curr_offset += len;
+
+    return (curr_offset - offset);
+}
+
+/*
+ * 5.5 Presentation of text strings
+ * (not implemented now)
+ */
+static guint16
+de_gsm_r_uus1_text_str(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo, guint32 offset)
+{
+    guint32	curr_offset;
+    guint32	len;
+    proto_item *item;
+    proto_tree *sub_tree;
+
+    curr_offset = offset;
+
+    len = tvb_get_guint8(tvb, offset+1);
+
+    item = proto_tree_add_item(tree, hf_gsm_r_uus1_present_text_str, tvb, curr_offset, len+2, ENC_NA);
+    sub_tree = proto_item_add_subtree(item, ett_gsm_r_uus1_present_text_str);
+
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_tag, tvb, curr_offset, 1, ENC_NA);
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_len, tvb, curr_offset+1, 1, ENC_NA);
+    curr_offset += 2;
+
+    proto_tree_add_expert(sub_tree, pinfo, &ei_gsm_r_uus1_not_implemented_yet, tvb, curr_offset, len);
+    curr_offset += len;
+
+    return (curr_offset - offset);
+}
+
+/*
+ * 5.6 Transfer of train position (eLDA)
+ *
+ */
+static const true_false_string gsm_r_uus1_elda_lat_hem = {
+    "North",
+    "South"
+};
+
+static const true_false_string gsm_r_uus1_elda_long_hem = {
+    "West",
+    "East"
+};
+
+const value_string gsm_r_uus1_elda_scale_vals[] = {
+    { 0,  "10 cm resolution" },
+    { 1,  "1 metre resolution" },
+    { 2,  "10 metre resolution" },
+    { 3,  "Odometry information not valid" },
+    { 0, NULL }
+};
+
+
+static guint16
+de_gsm_r_uus1_elda(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo _U_, guint32 offset)
+{
+    guint32	curr_offset;
+    guint   bit_offset;
+
+    guint32 val;
+    guint32 lat_deg_val;
+    guint32 lat_min_val;
+    guint32 lat_sec_val;
+    guint32 lat_hem_val;
+
+    guint32 long_deg_val;
+    guint32 long_min_val;
+    guint32 long_sec_val;
+    guint32 long_hem_val;
+
+    guint32 t_val;
+
+    proto_item *item;
+    proto_tree *sub_tree;
+
+    proto_item *lat_item;
+    proto_item *long_item;
+    proto_tree *lat_tree;
+    proto_tree *long_tree;
+
+    curr_offset = offset;
+
+    item = proto_tree_add_item(tree, hf_gsm_r_uus1_elda, tvb, curr_offset, 16, ENC_NA);
+    sub_tree = proto_item_add_subtree(item, ett_gsm_r_uus1_elda);
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_tag, tvb, curr_offset, 1, ENC_NA);
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_len, tvb, curr_offset+1, 1, ENC_NA);
+    curr_offset += 2;
+
+    bit_offset = curr_offset * 8;
+
+    /* Latitude */
+    lat_item = proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elda_lat, tvb, curr_offset, 4, ENC_NA);
+    lat_tree = proto_item_add_subtree(lat_item, ett_gsm_r_uus1_elda_lat);
+
+    val = tvb_get_guint32(tvb, curr_offset, ENC_NA);
+    lat_deg_val = tvb_get_bits(tvb, bit_offset, 7, ENC_NA);
+    bit_offset += 7;
+    lat_min_val = tvb_get_bits(tvb, bit_offset, 6, ENC_NA);
+    bit_offset += 6;
+    lat_sec_val = tvb_get_bits(tvb, bit_offset, 13, ENC_NA);
+    bit_offset += 13;
+    lat_hem_val = tvb_get_bits(tvb, bit_offset, 1, ENC_NA);
+    bit_offset += 1;
+
+    proto_tree_add_uint(lat_tree, hf_gsm_r_uus1_elda_lat_deg, tvb, curr_offset, 4, val);
+    proto_tree_add_uint(lat_tree, hf_gsm_r_uus1_elda_lat_min, tvb, curr_offset, 4, val);
+    proto_tree_add_uint_format_value(lat_tree, hf_gsm_r_uus1_elda_lat_sec, tvb, curr_offset, 4, val, "%.2f", (float)(lat_sec_val)/100);
+    proto_tree_add_boolean(lat_tree, hf_gsm_r_uus1_elda_lat_hem, tvb, curr_offset, 4, val);
+
+    proto_item_set_text(lat_item, "Latitude: %d %d\'%.2f\"%s", lat_deg_val, lat_min_val, (float)(lat_sec_val)/100,
+        lat_hem_val ? "N" : "S");
+
+    curr_offset += 3;
+
+    /* Longtitude */
+    long_item = proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elda_long, tvb, curr_offset, 4, ENC_NA);
+    long_tree = proto_item_add_subtree(long_item, ett_gsm_r_uus1_elda_long);
+
+    val = tvb_get_guint32(tvb, curr_offset, ENC_NA);
+    long_deg_val = tvb_get_bits(tvb, bit_offset, 8, ENC_NA);
+    bit_offset += 8;
+    long_min_val = tvb_get_bits(tvb, bit_offset, 6, ENC_NA);
+    bit_offset += 6;
+    long_sec_val = tvb_get_bits(tvb, bit_offset, 13, ENC_NA);
+    bit_offset += 13;
+    long_hem_val = tvb_get_bits(tvb, bit_offset, 1, ENC_NA);
+    bit_offset += 1;
+
+    proto_tree_add_uint(long_tree, hf_gsm_r_uus1_elda_long_deg, tvb, curr_offset, 4, val);
+    proto_tree_add_uint(long_tree, hf_gsm_r_uus1_elda_long_min, tvb, curr_offset, 4, val);
+    proto_tree_add_uint_format_value(long_tree, hf_gsm_r_uus1_elda_long_sec, tvb, curr_offset, 4, val, "%.2f", (float)(long_sec_val)/100);
+    proto_tree_add_boolean(long_tree, hf_gsm_r_uus1_elda_long_hem, tvb, curr_offset, 4, val);
+
+    proto_item_set_text(long_item, "Longtitude: %d %d\'%.2f\"%s", long_deg_val, long_min_val, (float)(long_sec_val)/100,
+        long_hem_val ? "W" : "E");
+
+    curr_offset += 3;
+
+    /* Height, Speed, Heading */
+
+    // height step 1m. Range: -100m...+4500m
+    t_val = tvb_get_bits(tvb, bit_offset, 13, ENC_NA) - 100;
+    proto_tree_add_int(sub_tree, hf_gsm_r_uus1_elda_height, tvb, curr_offset, 4, t_val);
+    bit_offset += 13;
+
+    // speed step 10 km/h
+    t_val = tvb_get_bits(tvb, bit_offset, 6, ENC_NA) * 10;
+    proto_tree_add_uint(sub_tree, hf_gsm_r_uus1_elda_speed, tvb, curr_offset, 4, t_val);
+    bit_offset += 6;
+
+    // heading step 10 deg
+    t_val = tvb_get_bits(tvb, bit_offset, 6, ENC_NA) * 10;
+    proto_tree_add_uint(sub_tree, hf_gsm_r_uus1_elda_heading, tvb, curr_offset, 4, t_val);
+    bit_offset += 6;
+
+    curr_offset += 4;
+
+    /* Elapsed Time, Distance, Scale, Spare */
+
+    // time step 1 second. Range: 0...2047
+    t_val = tvb_get_bits(tvb, bit_offset, 11, ENC_NA);
+    proto_tree_add_uint(sub_tree, hf_gsm_r_uus1_elda_e_time, tvb, curr_offset, 4, t_val);
+    bit_offset += 11;
+
+    // distance step = 10 cm, 1 m or 10 m depending on the parameter Scale
+    t_val = tvb_get_bits(tvb, bit_offset, 14, ENC_NA);
+    proto_tree_add_uint(sub_tree, hf_gsm_r_uus1_elda_distance, tvb, curr_offset, 4, t_val);
+    bit_offset += 14;
+
+    // scale
+    t_val = tvb_get_bits(tvb, bit_offset, 2, ENC_NA);
+    proto_tree_add_uint(sub_tree, hf_gsm_r_uus1_elda_scale, tvb, curr_offset, 4, t_val);
+    bit_offset += 2;
+
+    // spare
+    t_val = tvb_get_bits(tvb, bit_offset, 5, ENC_NA);
+    proto_tree_add_uint(sub_tree, hf_gsm_r_uus1_elda_spare, tvb, curr_offset, 4, t_val);
+    bit_offset += 5;
+
+    return 16;
+}
+
+/*
+ * 5.7 Notification DSD alarm condition
+ *
+ */
+static guint16
+de_gsm_r_uus1_dsd_alarm(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo _U_, guint32 offset)
+{
+    guint32	curr_offset;
+    guint32	len;
+    const gchar *loco_engine_number;
+    proto_item *item;
+    proto_tree *sub_tree;
+
+    curr_offset = offset;
+
+    len = tvb_get_guint8(tvb, offset+1);
+
+    item = proto_tree_add_item(tree, hf_gsm_r_uus1_present_dsd_alarm, tvb, curr_offset, len+2, ENC_NA);
+    sub_tree = proto_item_add_subtree(item, ett_gsm_r_uus1_present_dsd_alarm);
+
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_tag, tvb, curr_offset, 1, ENC_NA);
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_len, tvb, curr_offset+1, 1, ENC_NA);
+    curr_offset += 2;
+
+    loco_engine_number = tvb_bcd_dig_to_wmem_packet_str(tvb, offset+2, len, NULL, FALSE);
+    proto_tree_add_string(sub_tree, hf_gsm_r_uus1_present_dsd_alarm_loco_number, tvb, curr_offset, len, loco_engine_number);
+    proto_item_append_text(item, ": %s", loco_engine_number);
+    curr_offset += len;
+
+    return (curr_offset - offset);
+}
+
+
+/*
+ * 5.8 Notification of a request to alert a controller
+ *
+ */
+static guint16
+de_gsm_r_uus1_alert_controller(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo _U_, guint32 offset)
+{
+    guint32	curr_offset;
+    guint32	len;
+    const gchar *gref_str;
+    proto_item *item;
+    proto_tree *sub_tree;
+
+    curr_offset = offset;
+
+    len = tvb_get_guint8(tvb, offset+1);
+
+    item = proto_tree_add_item(tree, hf_gsm_r_uus1_alert_controller, tvb, curr_offset+2, len, ENC_NA);
+    sub_tree = proto_item_add_subtree(item, ett_gsm_r_uus1_alert_controller);
+
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_tag, tvb, curr_offset, 1, ENC_NA);
+    proto_tree_add_item(sub_tree, hf_gsm_r_uus1_elem_len, tvb, curr_offset+1, 1, ENC_NA);
+    curr_offset += 2;
+
+    gref_str = tvb_bcd_dig_to_wmem_packet_str(tvb, curr_offset, 4, NULL, FALSE);
+    proto_tree_add_string(sub_tree, hf_gsm_r_uus1_alert_controller_gref, tvb, curr_offset, 4, gref_str);
+    proto_item_append_text(item, ": %s", gref_str);
+    curr_offset += 4;
+
+    return (curr_offset - offset);
+}
+
+
+static int
+dissect_gsm_r_uus1(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
+{
+    guint8  elem_tag;
+    guint32	offset;
+    guint32	len;
+    proto_item   *gsm_r_uus1_item   = NULL;
+    proto_tree   *gsm_r_uus1_tree   = NULL;
+
+    offset = 0;
+    len = tvb_captured_length(tvb);
+
+    gsm_r_uus1_item =
+        proto_tree_add_protocol_format(tree, proto_gsm_r_uus1, tvb, 0, len, "GSM-R User-to-User Signaling");
+
+    gsm_r_uus1_tree = proto_item_add_subtree(gsm_r_uus1_item, ett_gsm_r_uus1);
+
+    while (offset < len){
+        elem_tag = tvb_get_guint8(tvb, offset);
+        switch (elem_tag) {
+        case 2:
+        case 3:
+            offset += de_gsm_r_uus1_chpc(tvb, gsm_r_uus1_tree, offset);
+            break;
+        case 5:
+            offset += de_gsm_r_uus1_pfn(tvb, gsm_r_uus1_tree, offset);
+            break;
+        case 6:
+        case 7:
+        case 8:
+            offset += de_gsm_r_uus1_elda(tvb, gsm_r_uus1_tree, pinfo, offset);
+            break;
+        case 9:
+            offset += de_gsm_r_uus1_epfn(tvb, gsm_r_uus1_tree, pinfo, offset);
+            break;
+        case 10:
+            offset += de_gsm_r_uus1_text_str(tvb, gsm_r_uus1_tree, pinfo, offset);
+            break;
+        case 11:
+             offset += de_gsm_r_uus1_dsd_alarm(tvb, gsm_r_uus1_tree, pinfo, offset);
+            break;
+        case 12:
+            offset += de_gsm_r_uus1_alert_controller(tvb, gsm_r_uus1_tree, pinfo, offset);
+            break;
+        default:
+            return offset;
+        }
+    }
+
+    return offset;
+}
+
+/* heuristic dissector */
+static gboolean
+dissect_gsm_r_uus1_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
+{
+    if (dissect_gsm_r_uus1(tvb, pinfo, tree, NULL) > 0)
+        return FALSE;
+
+    return TRUE;
+}
+
+
+/* Register the protocol with Wireshark */
+void
+proto_register_gsm_r_uus1(void)
+{
+    /* Setup list of header fields */
+
+    static hf_register_info hf[] = {
+        { &hf_gsm_r_uus1_elem_tag,
+          { "Element tag", "gsm-r-uus1.elem_tag",
+            FT_UINT8, BASE_DEC, VALS(gsm_r_uus1_tags), 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elem_len,
+          { "Length", "gsm-r-uus1.elem_len",
+            FT_UINT8, BASE_DEC, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_pfn,
+          { "Presentation of Functional Number (PFN)", "gsm-r-uus1.pfn",
+            FT_NONE, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_pfn_digits,
+          { "Digits", "gsm-r-uus1.pfn.digits",
+            FT_STRING, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc,
+          { "Confirmation of High Priority Calls (CHPC)", "gsm-r-uus1.chpc",
+            FT_NONE, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_t_dur,
+          { "Duration of the call", "gsm-r-uus1.chpc.t_dur",
+            FT_UINT24, BASE_DEC, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_t_rel,
+          { "Interval between the end of the call and the transmission of the confirmation message", "gsm-r-uus1.chpc.t_rel",
+            FT_UINT32, BASE_DEC, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_pl_call,
+          { "Priority level of the call", "gsm-r-uus1.chpc.pl_call",
+            FT_UINT8, BASE_DEC|BASE_RANGE_STRING, RVALS(gsm_r_uus1_chpc_priority_vals), 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_cause,
+          { "Reason for termination of the call", "gsm-r-uus1.chpc.cause",
+            FT_UINT8, BASE_HEX, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_cause_power,
+          { "Mobile was powered off when receiving (power fail)", "gsm-r-uus1.chpc.cause.power",
+            FT_BOOLEAN, 8, NULL, 0x01,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_cause_radio,
+          { "Call was interrupted due to radio link error", "gsm-r-uus1.chpc.cause.radio",
+            FT_BOOLEAN, 8, NULL, 0x02,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_cause_reserved3,
+          { "Reserved", "gsm-r-uus1.chpc.cause.reserved3",
+            FT_BOOLEAN, 8, NULL, 0x04,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_cause_reserved4,
+          { "Reserved", "gsm-r-uus1.chpc.cause.reserved4",
+            FT_BOOLEAN, 8, NULL, 0x08,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_cause_user_command,
+          { "Call was left on user command", "gsm-r-uus1.chpc.cause.user_command",
+            FT_BOOLEAN, 8, NULL, 0x10,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_cause_reserved6,
+          { "Reserved", "gsm-r-uus1.chpc.cause.reserved6",
+            FT_BOOLEAN, 8, NULL, 0x20,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_cause_reserved7,
+          { "Reserved", "gsm-r-uus1.chpc.cause.reserved7",
+            FT_BOOLEAN, 8, NULL, 0x40,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_cause_reserved8,
+          { "Reserved", "gsm-r-uus1.chpc.cause.reserved8",
+            FT_BOOLEAN, 8, NULL, 0x80,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_gref,
+          { "Group call reference", "gsm-r-uus1.chpc.gref",
+            FT_STRING, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_chpc_ack_cause,
+          { "ACK/CAUSE", "gsm-r-uus1.chpc.ack_cause",
+            FT_UINT8, BASE_DEC|BASE_RANGE_STRING, RVALS(gsm_r_uus1_chpc_ack_cause_vals), 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_epfn,
+          { "Enhanced presentation of functional number (ePFN)", "gsm-r-uus1.epfn",
+            FT_BYTES, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_present_text_str,
+          { "Presentation of text strings", "gsm-r-uus1.present_text_str",
+            FT_BYTES, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda,
+          { "Train position (eLDA)", "gsm-r-uus1.elda",
+            FT_NONE, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_lat,
+          { "Lattitude", "gsm-r-uus1.elda.lat",
+            FT_NONE, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_lat_deg,
+          { "Degrees", "gsm-r-uus1.elda.lat.deg",
+            FT_UINT32, BASE_DEC, NULL, 0xFE000000,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_lat_min,
+          { "Minutes", "gsm-r-uus1.elda.lat.min",
+            FT_UINT32, BASE_DEC, NULL, 0x01F80000,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_lat_sec,
+          { "Seconds", "gsm-r-uus1.elda.lat.sec",
+            FT_UINT32, BASE_DEC, NULL, 0x0007FFC0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_lat_hem,
+          { "Hemisphere", "gsm-r-uus1.elda.lat.hem",
+            FT_BOOLEAN, 32, TFS(&gsm_r_uus1_elda_lat_hem), 0x00000020,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_long,
+          { "Lattitude", "gsm-r-uus1.elda.long",
+            FT_NONE, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_long_deg,
+          { "Degrees", "gsm-r-uus1.elda.long.deg",
+            FT_UINT32, BASE_DEC, NULL, 0x1FE00000,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_long_min,
+          { "Minutes", "gsm-r-uus1.elda.long.min",
+            FT_UINT32, BASE_DEC, NULL, 0x001F8000,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_long_sec,
+          { "Seconds", "gsm-r-uus1.elda_long.sec",
+            FT_UINT32, BASE_DEC, NULL, 0x00007FFC,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_long_hem,
+          { "Hemisphere", "gsm-r-uus1.elda_long.hem",
+            FT_BOOLEAN, 32, TFS(&gsm_r_uus1_elda_long_hem), 0x00000002,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_height,
+          { "Height (m)", "gsm-r-uus1.elda.height",
+            FT_INT32, BASE_DEC, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_speed,
+          { "Speed (km/h)", "gsm-r-uus1.elda.speed",
+            FT_UINT32, BASE_DEC, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_heading,
+          { "Heading (deg)", "gsm-r-uus1.elda.heading",
+            FT_UINT8, BASE_DEC, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_e_time,
+          { "Elapsed Time (sec)", "gsm-r-uus1.elda.e_time",
+            FT_UINT32, BASE_DEC, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_distance,
+          { "Distance", "gsm-r-uus1.elda.distance",
+            FT_UINT32, BASE_DEC, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_scale,
+          { "Scale", "gsm-r-uus1.elda.scale",
+            FT_UINT32, BASE_DEC, VALS(gsm_r_uus1_elda_scale_vals), 0x00,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_elda_spare,
+          { "Spare", "gsm-r-uus1.elda.spare",
+            FT_UINT32, BASE_DEC, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_present_dsd_alarm,
+          { "Notification DSD alarm condition", "gsm-r-uus1.present_dsd_alarm",
+            FT_NONE, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_present_dsd_alarm_loco_number,
+          { "Locomotive engine number", "gsm-r-uus1.present_dsd_alarm.loco_number",
+            FT_STRING, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_alert_controller,
+          { "Notification of a request to alert a controller", "gsm-r-uus1.alert_controller",
+            FT_NONE, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_gsm_r_uus1_alert_controller_gref,
+          { "Group call reference", "gsm-r-uus1.alert_controller.gref",
+            FT_STRING, BASE_NONE, NULL, 0x0,
+            NULL, HFILL }
+        },
+    };
+
+    static ei_register_info ei[] = {
+        { &ei_gsm_r_uus1_not_implemented_yet, { "gsm-r-uus1.not_implemented_yet", PI_PROTOCOL, PI_UNDECODED, "Not implemented yet", EXPFILL }},
+    };
+
+    expert_module_t* expert_gsm_r_uus1;
+
+    static gint *ett[] = {
+        &ett_gsm_r_uus1,
+        &ett_gsm_r_uus1_pfn,
+        &ett_gsm_r_uus1_chpc,
+        &ett_gsm_r_uus1_chpc_cause,
+        &ett_gsm_r_uus1_epfn,
+        &ett_gsm_r_uus1_present_text_str,
+        &ett_gsm_r_uus1_elda,
+        &ett_gsm_r_uus1_elda_lat,
+        &ett_gsm_r_uus1_elda_long,
+        &ett_gsm_r_uus1_present_dsd_alarm,
+        &ett_gsm_r_uus1_alert_controller
+    };
+
+    module_t *gsm_r_uus1_module;
+
+    /* Register the protocol name and description */
+    proto_gsm_r_uus1 =
+        proto_register_protocol("GSM-R User-to-User Signaling", "GSM-R", "gsm-r-uus1");
+
+    proto_register_field_array(proto_gsm_r_uus1, hf, array_length(hf));
+
+    proto_register_subtree_array(ett, array_length(ett));
+
+    expert_gsm_r_uus1 = expert_register_protocol(proto_gsm_r_uus1);
+    expert_register_field_array(expert_gsm_r_uus1, ei, array_length(ei));
+
+    /* subdissector code */
+    register_dissector("gsm-r-uus1", dissect_gsm_r_uus1, proto_gsm_r_uus1);
+
+    gsm_r_uus1_module = prefs_register_protocol(proto_gsm_r_uus1, proto_reg_handoff_gsm_r_uus1);
+    prefs_register_bool_preference(gsm_r_uus1_module, "dissect_q931_u2u",
+        "Dissect Q.931 User-To-User information",
+        "Dissect Q.931 User-To-User information",
+        &q931_u2u);
+    prefs_register_bool_preference(gsm_r_uus1_module, "dissect_gsm_a_u2u",
+        "Dissect GSM-A User-To-User information",
+        "Dissect GSM-A User-To-User information",
+        &gsm_a_u2u);
+}
+
+void
+proto_reg_handoff_gsm_r_uus1(void)
+{
+    dissector_handle_t gsm_r_uus1_handle;
+
+    gsm_r_uus1_handle = find_dissector("gsm-r-uus1");
+
+    if(q931_u2u){
+        heur_dissector_add("q931_user", dissect_gsm_r_uus1_heur, "GSM-R over UUS1", "gsm_r_uus1", proto_gsm_r_uus1, HEURISTIC_ENABLE);
+    } else {
+        heur_dissector_delete("q931_user", dissect_gsm_r_uus1_heur, proto_gsm_r_uus1);
+    }
+
+
+    if(gsm_a_u2u){
+        dissector_add_uint("gsm_a.dtap.u2u_prot_discr", 0, gsm_r_uus1_handle);
+    } else {
+        dissector_delete_uint("gsm_a.dtap.u2u_prot_discr", 0, gsm_r_uus1_handle);
+    }
+}
+
+/*
+ * Editor modelines  -  http://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:
+ */