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/* packet-sdlc.c
* Routines for SDLC frame disassembly
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <epan/packet.h>
#include <wiretap/wtap.h>
#include <epan/xdlc.h>
/*
* See:
*
* http://web.archive.org/web/20020206033700/http://www.wanresources.com/snacell.html
*
* http://web.archive.org/web/20150522015710/http://www.protocols.com/pbook/sna.htm
*
* Systems Network Architecture Formats, GA27-3136-20:
* https://publibz.boulder.ibm.com/cgi-bin/bookmgr/BOOKS/D50A5007/CCONTENTS
*/
void proto_register_sdlc(void);
void proto_reg_handoff_sdlc(void);
static dissector_handle_t sdlc_handle;
static int proto_sdlc;
static int hf_sdlc_address;
static int hf_sdlc_control;
static int hf_sdlc_n_r;
static int hf_sdlc_n_s;
static int hf_sdlc_p;
static int hf_sdlc_f;
static int hf_sdlc_s_ftype;
static int hf_sdlc_u_modifier_cmd;
static int hf_sdlc_u_modifier_resp;
static int hf_sdlc_ftype_i;
static int hf_sdlc_ftype_s_u;
static int ett_sdlc;
static int ett_sdlc_control;
static dissector_handle_t sna_handle;
static const xdlc_cf_items sdlc_cf_items = {
&hf_sdlc_n_r,
&hf_sdlc_n_s,
&hf_sdlc_p,
&hf_sdlc_f,
&hf_sdlc_s_ftype,
&hf_sdlc_u_modifier_cmd,
&hf_sdlc_u_modifier_resp,
&hf_sdlc_ftype_i,
&hf_sdlc_ftype_s_u
};
static int
dissect_sdlc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
proto_tree *sdlc_tree;
proto_item *sdlc_ti;
uint8_t addr;
uint16_t control;
int sdlc_header_len;
bool is_response;
tvbuff_t *next_tvb;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "SDLC");
col_clear(pinfo->cinfo, COL_INFO);
addr = tvb_get_uint8(tvb, 0);
sdlc_header_len = 1; /* address */
/*
* XXX - is there something in the SDLC header that indicates
* how to interpret "command vs. response" based on the
* direction?
*/
if (pinfo->p2p_dir == P2P_DIR_SENT) {
is_response = false;
col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DCE");
col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DTE");
}
else {
/* XXX - what if the direction is unknown? */
is_response = true;
col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DTE");
col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DCE");
}
sdlc_ti = proto_tree_add_item(tree, proto_sdlc, tvb, 0, -1,
ENC_NA);
sdlc_tree = proto_item_add_subtree(sdlc_ti, ett_sdlc);
proto_tree_add_uint(sdlc_tree, hf_sdlc_address, tvb, 0, 1,
addr);
/*
* XXX - SDLC has a mod-128 mode as well as a mod-7 mode.
* We can infer the mode from an SNRM/SRME frame, but if
* we don't see one of them, we may have to have a preference
* to control what to use.
*/
control = dissect_xdlc_control(tvb, 1, pinfo, sdlc_tree, hf_sdlc_control,
ett_sdlc_control, &sdlc_cf_items, NULL, NULL, NULL,
is_response, false, false);
sdlc_header_len += XDLC_CONTROL_LEN(control, false);
proto_item_set_len(sdlc_ti, sdlc_header_len);
/*
* XXX - is there an FCS at the end, at least in Sniffer
* captures? (There doesn't appear to be.)
*/
next_tvb = tvb_new_subset_remaining(tvb, sdlc_header_len);
if (XDLC_IS_INFORMATION(control)) {
/* call the SNA dissector */
call_dissector(sna_handle, next_tvb, pinfo, tree);
} else
call_data_dissector(next_tvb, pinfo, tree);
return tvb_captured_length(tvb);
}
void
proto_register_sdlc(void)
{
static hf_register_info hf[] = {
{ &hf_sdlc_address,
{ "Address Field", "sdlc.address", FT_UINT8, BASE_HEX,
NULL, 0x0, NULL, HFILL }},
{ &hf_sdlc_control,
{ "Control Field", "sdlc.control", FT_UINT16, BASE_HEX,
NULL, 0x0, NULL, HFILL }},
{ &hf_sdlc_n_r,
{ "N(R)", "sdlc.control.n_r", FT_UINT8, BASE_DEC,
NULL, XDLC_N_R_MASK, NULL, HFILL }},
{ &hf_sdlc_n_s,
{ "N(S)", "sdlc.control.n_s", FT_UINT8, BASE_DEC,
NULL, XDLC_N_S_MASK, NULL, HFILL }},
{ &hf_sdlc_p,
{ "Poll", "sdlc.control.p", FT_BOOLEAN, 8,
TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},
{ &hf_sdlc_f,
{ "Final", "sdlc.control.f", FT_BOOLEAN, 8,
TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},
{ &hf_sdlc_s_ftype,
{ "Supervisory frame type", "sdlc.control.s_ftype", FT_UINT8, BASE_HEX,
VALS(stype_vals), XDLC_S_FTYPE_MASK, NULL, HFILL }},
{ &hf_sdlc_u_modifier_cmd,
{ "Command", "sdlc.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
{ &hf_sdlc_u_modifier_resp,
{ "Response", "sdlc.control.u_modifier_resp", FT_UINT8, BASE_HEX,
VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
{ &hf_sdlc_ftype_i,
{ "Frame type", "sdlc.control.ftype", FT_UINT8, BASE_HEX,
VALS(ftype_vals), XDLC_I_MASK, NULL, HFILL }},
{ &hf_sdlc_ftype_s_u,
{ "Frame type", "sdlc.control.ftype", FT_UINT8, BASE_HEX,
VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},
};
static int *ett[] = {
&ett_sdlc,
&ett_sdlc_control,
};
proto_sdlc = proto_register_protocol("Synchronous Data Link Control (SDLC)", "SDLC", "sdlc");
proto_register_field_array(proto_sdlc, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
sdlc_handle = register_dissector("sdlc", dissect_sdlc, proto_sdlc);
}
void
proto_reg_handoff_sdlc(void)
{
/*
* Get handle for the SNA dissector.
*/
sna_handle = find_dissector_add_dependency("sna", proto_sdlc);
dissector_add_uint("wtap_encap", WTAP_ENCAP_SDLC, sdlc_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:
*/
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