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GSM A-bis/RSL: dissect and show RFN using parse_reduced_frame_number() 

3GPP came up with a special encoding of TDMA frame number, which reduces
the amount of bits needed to carry it from 32 to 16.  This encoding is
not only employed on the radio interface (GSM RR), but also on the
A-bis/RSL interface which is used between BTS and BSC nodes.

From the user perspective, parsed RFN value is a lot more meaningful
than the T1/T2/T3 variables used on the wire.  The GSM RR dissector
does show parsed RFN value together with these variables, while the RSL
dissector does not.  Let's show it in the RSL dissector too.
This commit is contained in:
Vadim Yanitskiy 2022-10-15 01:58:37 +07:00 committed by A Wireshark GitLab Utility
parent 269d3a9968
commit b93e8234f6
1 changed files with 17 additions and 0 deletions
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17
epan/dissectors/packet-rsl.c
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@ -33,6 +33,8 @@
void proto_register_rsl(void);
void proto_reg_handoff_rsl(void);
guint16 parse_reduced_frame_number(tvbuff_t *tvb, const gint offset);
/* Initialize the protocol and registered fields */
static int proto_rsl = -1;
@ -52,6 +54,7 @@ static int hf_rsl_req_ref_ra_est_cause = -1;
static int hf_rsl_req_ref_T1prim = -1;
static int hf_rsl_req_ref_T3 = -1;
static int hf_rsl_req_ref_T2 = -1;
static int hf_rsl_req_ref_rfn = -1;
static int hf_rsl_timing_adv = -1;
static int hf_rsl_ho_ref = -1;
static int hf_rsl_l1inf_power_lev = -1;
@ -1306,7 +1309,9 @@ static int
dissect_rsl_ie_frame_no(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree, int offset, gboolean is_mandatory)
{
proto_tree *ie_tree;
proto_item *ti;
guint8 ie_id;
guint16 rfn;
if (is_mandatory == FALSE) {
ie_id = tvb_get_guint8(tvb, offset);
@ -1320,11 +1325,14 @@ dissect_rsl_ie_frame_no(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree,
proto_tree_add_item(ie_tree, hf_rsl_ie_id, tvb, offset, 1, ENC_BIG_ENDIAN);
offset++;
rfn = parse_reduced_frame_number(tvb, offset);
proto_tree_add_item(ie_tree, hf_rsl_req_ref_T1prim, tvb, offset, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(ie_tree, hf_rsl_req_ref_T3, tvb, offset, 2, ENC_BIG_ENDIAN);
offset++;
proto_tree_add_item(ie_tree, hf_rsl_req_ref_T2, tvb, offset, 1, ENC_BIG_ENDIAN);
offset++;
ti = proto_tree_add_uint(ie_tree, hf_rsl_req_ref_rfn, tvb, offset - 2, 2, rfn);
proto_item_set_generated(ti);
return offset;
}
@ -1848,6 +1856,7 @@ dissect_rsl_ie_req_ref(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree,
{
proto_tree *ie_tree, *ra_tree;
guint8 ie_id;
guint16 rfn;
proto_item *ti;
if (is_mandatory == FALSE) {
@ -1865,11 +1874,14 @@ dissect_rsl_ie_req_ref(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree,
ra_tree = proto_item_add_subtree(ti, ett_ie_req_ref_ra);
proto_tree_add_item(ra_tree, hf_rsl_req_ref_ra_est_cause, tvb, offset, 1, ENC_BIG_ENDIAN);
offset++;
rfn = parse_reduced_frame_number(tvb, offset);
proto_tree_add_item(ie_tree, hf_rsl_req_ref_T1prim, tvb, offset, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(ie_tree, hf_rsl_req_ref_T3, tvb, offset, 2, ENC_BIG_ENDIAN);
offset++;
proto_tree_add_item(ie_tree, hf_rsl_req_ref_T2, tvb, offset, 1, ENC_BIG_ENDIAN);
offset++;
ti = proto_tree_add_uint(ie_tree, hf_rsl_req_ref_rfn, tvb, offset - 2, 2, rfn);
proto_item_set_generated(ti);
return offset;
}
@ -4801,6 +4813,11 @@ void proto_register_rsl(void)
FT_UINT8, BASE_DEC, NULL, 0x1f,
NULL, HFILL }
},
{ &hf_rsl_req_ref_rfn,
{ "RFN", "gsm_abis_rsl.req_ref_rfn",
FT_UINT16, BASE_DEC, NULL, 0x0,
"Reduced Frame Number", HFILL }
},
{ &hf_rsl_timing_adv,
{ "Timing Advance", "gsm_abis_rsl.timing_adv",
FT_UINT8, BASE_DEC, NULL, 0x0,