osmocom/wireshark
14
0
Fork 1
Code Issues Pull requests Projects Releases Wiki Activity
wireshark/epan/dissectors/packet-ehdlc.c
John Thacker ee6519bca6 L2TP: Use the IANA assigned PW types for Decode As 
Instead of registering subdissectors to arbitrary Wireshark
assigned numbers, register them to the actual pseudowire type
number assigned by IANA and present in the Pseudowire Type AVP.
Half of the previously registered types were never used, because
the dissector table could not be called with their Wireshark
internal number.

This makes it easier to add dissectors to support currently
unsupported but assigned types, and also makes it more intuitive
to use Decode As when the PW Type AVP is not present. Previously,
the dissector for the "default" type of CHDLC had to be changed to
a different subdissector.
2022-08-10 21:23:38 -04:00

480 lines
12 KiB
C
Raw Blame History

/* packet-ehdlc.c
* Routines for packet dissection of Ericsson HDLC as used in A-bis over IP
* Copyright 2010-2012, 2016 by Harald Welte <laforge@gnumonks.org>
*
* This code is based on pure educational guesses while looking at protocol
* traces, as there is no publicly available protocol description by Ericsson.
* Even the name is a guess, since it looks quite a bit like HDLC and is used
* by Ericsson, I called it EHDLC.
*
* 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/xdlc.h>
#include "packet-l2tp.h"
void proto_register_ehdlc(void);
void proto_reg_handoff_ehdlc(void);
/* Initialize the protocol and registered fields */
static int proto_ehdlc = -1;
static int hf_ehdlc_data_len = -1;
static int hf_ehdlc_csapi = -1;
static int hf_ehdlc_ctei = -1;
static int hf_ehdlc_sapi = -1;
static int hf_ehdlc_tei = -1;
static int hf_ehdlc_c_r = -1;
static int hf_ehdlc_xid_payload = -1;
static int hf_ehdlc_xid_win_tx = -1;
static int hf_ehdlc_xid_win_rx = -1;
static int hf_ehdlc_xid_ack_tmr_ms = -1;
static int hf_ehdlc_xid_format_id = -1;
static int hf_ehdlc_xid_group_id = -1;
static int hf_ehdlc_xid_len = -1;
static int hf_ehdlc_control = -1;
static int hf_ehdlc_p = -1;
static int hf_ehdlc_f = -1;
static int hf_ehdlc_u_modifier_cmd = -1;
static int hf_ehdlc_u_modifier_resp = -1;
static int hf_ehdlc_ftype_s_u = -1;
static int hf_ehdlc_n_r = -1;
static int hf_ehdlc_n_s = -1;
static int hf_ehdlc_p_ext = -1;
static int hf_ehdlc_f_ext = -1;
static int hf_ehdlc_s_ftype = -1;
static int hf_ehdlc_ftype_i = -1;
static int hf_ehdlc_ftype_s_u_ext = -1;
static dissector_handle_t ehdlc_handle;
/* Used only for U frames */
static const xdlc_cf_items ehdlc_cf_items = {
NULL,
NULL,
&hf_ehdlc_p,
&hf_ehdlc_f,
NULL,
&hf_ehdlc_u_modifier_cmd,
&hf_ehdlc_u_modifier_resp,
NULL,
&hf_ehdlc_ftype_s_u
};
/* Used only for I and S frames */
static const xdlc_cf_items ehdlc_cf_items_ext = {
&hf_ehdlc_n_r,
&hf_ehdlc_n_s,
&hf_ehdlc_p_ext,
&hf_ehdlc_f_ext,
&hf_ehdlc_s_ftype,
NULL,
NULL,
&hf_ehdlc_ftype_i,
&hf_ehdlc_ftype_s_u_ext,
};
/* Initialize the subtree pointers */
static gint ett_ehdlc = -1;
static gint ett_ehdlc_xid = -1;
static gint ett_ehdlc_control = -1;
enum {
SUB_RSL,
SUB_OML,
SUB_TFP,
SUB_PGSL,
SUB_DATA,
SUB_MAX
};
/* Determine TEI from Compressed TEI */
static guint8 tei_from_ctei(guint8 ctei)
{
if (ctei < 12)
return ctei;
else
return 60 + (ctei - 12);
}
static guint8 c_r_from_csapi(guint8 csapi)
{
switch (csapi) {
case 1:
case 6:
return 1;
default:
return 0;
}
}
static guint8 sapi_from_csapi(guint8 csapi)
{
switch (csapi) {
case 0:
case 1: /* RSL */
return 0;
case 2: /* TFP */
return 10;
case 3: /* TFP */
return 11;
case 4: /* P-GSL */
return 12;
case 5:
case 6: /* OML */
return 62;
case 7:
default:
/* error! */
return 0;
}
}
static dissector_handle_t sub_handles[SUB_MAX];
static int
dissect_ehdlc_xid(proto_tree *tree, tvbuff_t *tvb, guint base_offset, guint len)
{
guint offset = base_offset;
proto_item *ti;
proto_tree *xid_tree;
/* XID is formatted like ISO 8885, typically we see
* something like
* 82 format identifier
* 80 group identifier
* 00 09 length
* 07 01 05 Window Size Tx
* 09 01 04 Ack Timer (msec)
* 08 01 05 Window Size Rx */
ti = proto_tree_add_item(tree, hf_ehdlc_xid_payload,
tvb, offset, len, ENC_NA);
xid_tree = proto_item_add_subtree(ti, ett_ehdlc_xid);
proto_tree_add_item(xid_tree, hf_ehdlc_xid_format_id, tvb, offset++, 1, ENC_NA);
proto_tree_add_item(xid_tree, hf_ehdlc_xid_group_id, tvb, offset++, 1, ENC_NA);
proto_tree_add_item(xid_tree, hf_ehdlc_xid_len, tvb, offset, 2, ENC_BIG_ENDIAN);
offset += 2;
while (tvb_reported_length_remaining(tvb, offset) >= 2) {
guint8 iei = tvb_get_guint8(tvb, offset++);
guint8 ie_len = tvb_get_guint8(tvb, offset++);
switch (iei) {
case 0x07:
proto_tree_add_item(xid_tree, hf_ehdlc_xid_win_tx, tvb,
offset, ie_len, ENC_NA);
break;
case 0x08:
proto_tree_add_item(xid_tree, hf_ehdlc_xid_win_rx, tvb,
offset, ie_len, ENC_NA);
break;
case 0x09:
proto_tree_add_item(xid_tree, hf_ehdlc_xid_ack_tmr_ms, tvb,
offset, ie_len, ENC_NA);
break;
}
offset += ie_len;
}
return offset - base_offset;
}
/* Code to actually dissect the packets */
static int
dissect_ehdlc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
int offset = 4;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "EHDLC");
col_clear(pinfo->cinfo, COL_INFO);
while (tvb_reported_length_remaining(tvb, offset) > 0) {
proto_item *ti = NULL;
proto_tree *ehdlc_tree = NULL;
guint16 len, hdr2;
guint8 csapi, ctei, sapi, tei, c_r;
tvbuff_t *next_tvb;
guint16 control;
gboolean is_response = FALSE, is_extended = TRUE;
gint header_length = 2; /* Address + Length field */
hdr2 = tvb_get_guint16(tvb, offset, ENC_BIG_ENDIAN);
len = hdr2 & 0x1FF;
csapi = hdr2 >> 13;
sapi = sapi_from_csapi(csapi);
c_r = c_r_from_csapi(csapi);
ctei = (hdr2 >> 9) & 0xF;
tei = tei_from_ctei(ctei);
/* Add TEI to INFO column */
col_append_fstr(pinfo->cinfo, COL_INFO, " | TEI:%02u | ", tei);
col_set_fence(pinfo->cinfo, COL_INFO);
if (tree) {
/* Use MIN(...,...) in the following to prevent a premature */
/* exception before we try to dissect whatever is available. */
ti = proto_tree_add_protocol_format(tree, proto_ehdlc,
tvb, offset, MIN(len, tvb_captured_length_remaining(tvb,offset)),
"Ericsson HDLC protocol");
ehdlc_tree = proto_item_add_subtree(ti, ett_ehdlc);
proto_tree_add_item(ehdlc_tree, hf_ehdlc_csapi,
tvb, offset, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(ehdlc_tree, hf_ehdlc_ctei,
tvb, offset, 1, ENC_BIG_ENDIAN);
ti = proto_tree_add_uint(ehdlc_tree, hf_ehdlc_c_r,
tvb, offset, 1, c_r);
proto_item_set_generated(ti);
ti = proto_tree_add_uint(ehdlc_tree, hf_ehdlc_sapi,
tvb, offset, 1, sapi);
proto_item_set_generated(ti);
ti = proto_tree_add_uint(ehdlc_tree, hf_ehdlc_tei,
tvb, offset, 1, tei);
proto_item_set_generated(ti);
proto_tree_add_item(ehdlc_tree, hf_ehdlc_data_len,
tvb, offset, 2, ENC_BIG_ENDIAN);
}
if (sapi == 10 || sapi == 11) {
/* Voice TRAU */
next_tvb = tvb_new_subset_length(tvb, offset+2, len-2);
call_dissector(sub_handles[SUB_TFP], next_tvb, pinfo, tree);
offset += len;
continue;
} else if (sapi == 12) {
/* GPRS TRAU */
next_tvb = tvb_new_subset_length(tvb, offset+2, len-2);
call_dissector(sub_handles[SUB_PGSL], next_tvb, pinfo, tree);
offset += len;
continue;
}
control = dissect_xdlc_control(tvb, offset+2, pinfo, ehdlc_tree, hf_ehdlc_control,
ett_ehdlc_control, &ehdlc_cf_items, &ehdlc_cf_items_ext,
NULL, NULL, is_response, is_extended, FALSE);
header_length += XDLC_CONTROL_LEN(control, is_extended);
if (XDLC_IS_INFORMATION(control)) {
next_tvb = tvb_new_subset_length(tvb, offset+header_length,
len-header_length);
switch (sapi) {
case 0:
/* len == 4 seems to be some kind of ACK */
if (len <= 4)
break;
call_dissector(sub_handles[SUB_RSL], next_tvb, pinfo, tree);
break;
case 62:
/* len == 4 seems to be some kind of ACK */
if (len <= 4)
break;
call_dissector(sub_handles[SUB_OML], next_tvb, pinfo, tree);
break;
default:
call_dissector(sub_handles[SUB_DATA], next_tvb, pinfo, tree);
break;
}
} else if (control == (XDLC_U | XDLC_XID)) {
dissect_ehdlc_xid(ehdlc_tree, tvb, offset+header_length,
len-header_length);
}
if (len == 0)
len = 1;
offset += len;
}
return tvb_captured_length(tvb);
}
void
proto_register_ehdlc(void)
{
static hf_register_info hf[] = {
{ &hf_ehdlc_data_len,
{ "DataLen", "ehdlc.data_len",
FT_UINT16, BASE_DEC, NULL, 0x1FF,
"The length of the data (in bytes)", HFILL }
},
{ &hf_ehdlc_csapi,
{ "Compressed SAPI", "ehdlc.csapi",
FT_UINT8, BASE_DEC, NULL, 0xE0,
NULL, HFILL}
},
{ &hf_ehdlc_ctei,
{ "Compressed TEI", "ehdlc.ctei",
FT_UINT8, BASE_DEC, NULL, 0x1E,
NULL, HFILL}
},
{ &hf_ehdlc_sapi,
{ "SAPI", "ehdlc.sapi",
FT_UINT8, BASE_DEC, NULL, 0,
NULL, HFILL }
},
{ &hf_ehdlc_tei,
{ "TEI", "ehdlc.tei",
FT_UINT8, BASE_DEC, NULL, 0,
NULL, HFILL }
},
{ &hf_ehdlc_c_r,
{ "C/R", "ehdlc.c_r",
FT_UINT8, BASE_DEC, NULL, 0,
NULL, HFILL }
},
{ &hf_ehdlc_xid_payload,
{ "XID Payload", "ehdlc.xid_payload",
FT_BYTES, BASE_NONE, NULL, 0,
NULL, HFILL }
},
{ &hf_ehdlc_xid_win_tx,
{ "Transmit Window", "ehdlc.xid.win_tx",
FT_UINT8, BASE_DEC, NULL, 0,
NULL, HFILL }
},
{ &hf_ehdlc_xid_win_rx,
{ "Receive Window", "ehdlc.xid.win_rx",
FT_UINT8, BASE_DEC, NULL, 0,
NULL, HFILL }
},
{ &hf_ehdlc_xid_ack_tmr_ms,
{ "Timer (ms)", "ehdlc.xid.ack_tmr_ms",
FT_UINT8, BASE_DEC, NULL, 0,
NULL, HFILL }
},
{ &hf_ehdlc_xid_format_id,
{ "Format Identifier", "ehdlc.xid.format_id",
FT_UINT8, BASE_HEX, NULL, 0,
NULL, HFILL }
},
{ &hf_ehdlc_xid_group_id,
{ "Group Identifier", "ehdlc.xid.group_id",
FT_UINT8, BASE_HEX, NULL, 0,
NULL, HFILL }
},
{ &hf_ehdlc_xid_len,
{ "XID Length", "ehdlc.xid.len",
FT_UINT16, BASE_DEC, NULL, 0,
NULL, HFILL }
},
{ &hf_ehdlc_control,
{ "Control Field", "ehdlc.control",
FT_UINT16, BASE_HEX, NULL, 0,
NULL, HFILL }
},
{ &hf_ehdlc_n_r,
{ "N(R)", "ehdlc.control.n_r",
FT_UINT16, BASE_DEC, NULL, XDLC_N_R_EXT_MASK,
NULL, HFILL }
},
{ &hf_ehdlc_n_s,
{ "N(S)", "ehdlc.control.n_s",
FT_UINT16, BASE_DEC, NULL, XDLC_N_S_EXT_MASK,
NULL, HFILL }
},
{ &hf_ehdlc_p,
{ "Poll", "ehdlc.control.p",
FT_BOOLEAN, 8, TFS(&tfs_set_notset), XDLC_P_F,
NULL, HFILL }
},
{ &hf_ehdlc_p_ext,
{ "Poll", "ehdlc.control.p",
FT_BOOLEAN, 16, TFS(&tfs_set_notset), XDLC_P_F_EXT,
NULL, HFILL }
},
{ &hf_ehdlc_f,
{ "Final", "ehdlc.control.f",
FT_BOOLEAN, 8, TFS(&tfs_set_notset), XDLC_P_F,
NULL, HFILL }
},
{ &hf_ehdlc_f_ext,
{ "Final", "ehdlc.control.f",
FT_BOOLEAN, 16, TFS(&tfs_set_notset), XDLC_P_F_EXT,
NULL, HFILL }
},
{ &hf_ehdlc_s_ftype,
{ "Supervisory frame type", "ehdlc.control.s_ftype",
FT_UINT16, BASE_HEX, VALS(stype_vals), XDLC_S_FTYPE_MASK,
NULL, HFILL }
},
{ &hf_ehdlc_u_modifier_cmd,
{ "Command", "ehdlc.control.u_modifier_cmd",
FT_UINT8, BASE_HEX, VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK,
NULL, HFILL }
},
{ &hf_ehdlc_u_modifier_resp,
{ "Response", "ehdlc.control.u_modifier_resp",
FT_UINT8, BASE_HEX, VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK,
NULL, HFILL }
},
{ &hf_ehdlc_ftype_i,
{ "Frame Type", "ehdlc.control.ftype",
FT_UINT16, BASE_HEX, VALS(ftype_vals), XDLC_I_MASK,
NULL, HFILL }
},
{ &hf_ehdlc_ftype_s_u,
{ "Frame Type", "ehdlc.control.ftype",
FT_UINT8, BASE_HEX, VALS(ftype_vals), XDLC_S_U_MASK,
NULL, HFILL }
},
{ &hf_ehdlc_ftype_s_u_ext,
{ "Frame Type", "ehdlc.control.ftype",
FT_UINT16, BASE_HEX, VALS(ftype_vals), XDLC_S_U_MASK,
NULL, HFILL }
},
};
static gint *ett[] = {
&ett_ehdlc,
&ett_ehdlc_xid,
&ett_ehdlc_control,
};
proto_ehdlc =
proto_register_protocol("Ericsson HDLC",
"Ericsson HDLC as used in A-bis over IP", "ehdlc");
proto_register_field_array(proto_ehdlc, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
ehdlc_handle = register_dissector("ehdlc", dissect_ehdlc, proto_ehdlc);
}
void
proto_reg_handoff_ehdlc(void)
{
sub_handles[SUB_RSL] = find_dissector_add_dependency("gsm_abis_rsl", proto_ehdlc);
sub_handles[SUB_OML] = find_dissector_add_dependency("gsm_abis_oml", proto_ehdlc);
sub_handles[SUB_TFP] = find_dissector_add_dependency("gsm_abis_tfp", proto_ehdlc);
sub_handles[SUB_PGSL] = find_dissector_add_dependency("gsm_abis_pgsl", proto_ehdlc);
sub_handles[SUB_DATA] = find_dissector("data");
dissector_add_for_decode_as("l2tp.pw_type", ehdlc_handle);
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 8
* tab-width: 8
* indent-tabs-mode: t
* End:
*
* vi: set shiftwidth=8 tabstop=8 noexpandtab:
* :indentSize=8:tabSize=8:noTabs=false:
*/
Reference in a new issue View git blame Copy permalink