path: root/epan/dissectors/packet-dcc.c

/* packet-dcc.c
 * Routines for Distributed Checksum Clearinghouse packet dissection
 * DCC Home: http://www.rhyolite.com/anti-spam/dcc/
 *
 * Copyright 1999, Nathan Neulinger <nneul@umr.edu>
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * Copied from packet-tftp.c
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "config.h"

#include <epan/packet.h>
#include <epan/expert.h>

#include "packet-dcc.h"

void proto_register_dcc(void);
void proto_reg_handoff_dcc(void);

static int proto_dcc = -1;
static int hf_dcc_len = -1;
static int hf_dcc_pkt_vers = -1;
static int hf_dcc_op = -1;
static int hf_dcc_clientid = -1;
static int hf_dcc_opnums_host = -1;
static int hf_dcc_opnums_pid = -1;
static int hf_dcc_opnums_report = -1;
static int hf_dcc_opnums_retrans = -1;

static int hf_dcc_signature = -1;
static int hf_dcc_max_pkt_vers = -1;
static int hf_dcc_qdelay_ms = -1;
static int hf_dcc_brand = -1;

static int hf_dcc_ck_type = -1;
static int hf_dcc_ck_len = -1;
static int hf_dcc_ck_sum = -1;

static int hf_dcc_date = -1;

static int hf_dcc_target = -1;
static int hf_dcc_response_text = -1;

static int hf_dcc_adminop = -1;
static int hf_dcc_adminval = -1;
static int hf_dcc_floodop = -1;
static int hf_dcc_trace = -1;
static int hf_dcc_trace_admin = -1;
static int hf_dcc_trace_anon = -1;
static int hf_dcc_trace_client = -1;
static int hf_dcc_trace_rlim = -1;
static int hf_dcc_trace_query = -1;
static int hf_dcc_trace_ridc = -1;
static int hf_dcc_trace_flood = -1;

static int hf_dcc_addr = -1;
static int hf_dcc_id = -1;
static int hf_dcc_last_used = -1;
static int hf_dcc_requests = -1;
static int hf_dcc_pad = -1;
static int hf_dcc_unused = -1;

static gint ett_dcc = -1;
static gint ett_dcc_opnums = -1;
static gint ett_dcc_op = -1;
static gint ett_dcc_ck = -1;
static gint ett_dcc_trace = -1;

static expert_field ei_dcc_len = EI_INIT;

/* Utility macros */
#define D_SIGNATURE() \
	proto_tree_add_item(dcc_optree, hf_dcc_signature, tvb, \
		offset, (int)sizeof(DCC_SIGNATURE), ENC_NA); \
	offset += (int)sizeof(DCC_SIGNATURE);

#define D_LABEL(hf_label, len, encoding) \
	proto_tree_add_item(dcc_optree, hf_label, tvb, offset, len, encoding); \
	offset += len;

#define D_TEXT(hf_label, endpad) { \
	int next_offset,left; \
	while (tvb_offset_exists(tvb, offset+endpad)) { \
		left = tvb_reported_length_remaining(tvb,offset) - endpad; \
		tvb_find_line_end(tvb, offset, left, &next_offset, \
		    FALSE); \
		proto_tree_add_item(dcc_optree, hf_label, tvb, offset, \
			next_offset - offset, ENC_ASCII|ENC_NA); \
		offset = next_offset; \
	} \
}


#define D_TARGET() \
	proto_tree_add_item(dcc_tree, hf_dcc_target, tvb, \
		offset, (int)sizeof(DCC_TGTS), ENC_BIG_ENDIAN); \
	offset += (int)sizeof(DCC_TGTS);

#define D_DATE() { \
	proto_tree_add_item(dcc_optree, hf_dcc_date, tvb, offset, 4, ENC_TIME_SECS|ENC_BIG_ENDIAN); \
	offset += 4; \
}


#define D_CHECKSUM() { \
	proto_tree *cktree; \
	cktree = proto_tree_add_subtree_format(dcc_optree, tvb, offset, (int)sizeof(DCC_CK), \
		ett_dcc_ck, NULL, "Checksum - %s", val_to_str(tvb_get_guint8(tvb,offset), \
		dcc_cktype_vals, \
		"Unknown Type: %u")); \
	proto_tree_add_item(cktree, hf_dcc_ck_type, tvb, offset, 1, ENC_BIG_ENDIAN); \
	offset += 1; \
	proto_tree_add_item(cktree, hf_dcc_ck_len, tvb, offset, 1, ENC_BIG_ENDIAN); \
	offset += 1; \
	proto_tree_add_item(cktree, hf_dcc_ck_sum, tvb, offset, \
		(int)sizeof(DCC_SUM), ENC_NA); \
	offset += (int)sizeof(DCC_SUM); \
}


/* Lookup string tables */
static const value_string dcc_op_vals[] = {
	{DCC_OP_INVALID,    "Invalid Op"},
	{DCC_OP_NOP,	    "No-Op"},
	{DCC_OP_REPORT,	    "Report and Query"},
	{DCC_OP_QUERY,	    "Query"},
	{DCC_OP_QUERY_RESP, "Server Response"},
	{DCC_OP_ADMN,	    "Admin"},
	{DCC_OP_OK,	    "Ok"},
	{DCC_OP_ERROR,	    "Server Failing"},
	{DCC_OP_DELETE,	    "Delete Checksum(s)"},
	{0, NULL}
};

static const value_string dcc_cktype_vals[] = {
	{DCC_CK_INVALID,    "Invalid/Deleted from DB when seen"},
	{DCC_CK_IP,	    "MD5 of binary source IPv6 address"},
	{DCC_CK_ENV_FROM,   "MD5 of envelope Mail From value"},
	{DCC_CK_FROM,	    "MD5 of header From: line"},
	{DCC_CK_SUB,	    "MD5 of substitute header line"},
	{DCC_CK_MESSAGE_ID, "MD5 of header Message-ID: line"},
	{DCC_CK_RECEIVED,   "MD5 of last header Received: line"},
	{DCC_CK_BODY,	    "MD5 of body"},
	{DCC_CK_FUZ1,	    "MD5 of filtered body - FUZ1"},
	{DCC_CK_FUZ2,	    "MD5 of filtered body - FUZ2"},
	{DCC_CK_FUZ3,	    "MD5 of filtered body - FUZ3"},
	{DCC_CK_FUZ4,	    "MD5 of filtered body - FUZ4"},
	{DCC_CK_SRVR_ID,    "hostname for server-ID check "},
	{DCC_CK_ENV_TO,	    "MD5 of envelope Rcpt To value"},
	{0, NULL},
};

static const value_string dcc_adminop_vals[] = {
	{DCC_AOP_OK,	      "Never sent"},
	{DCC_AOP_STOP,	      "Stop Gracefully"},
	{DCC_AOP_NEW_IDS,     "Load keys and client IDs"},
	{DCC_AOP_FLOD,	      "Flood control"},
	{DCC_AOP_DB_UNLOCK,   "Start Switch to new database"},
	{DCC_AOP_DB_NEW,      "Finish Switch to new database"},
	{DCC_AOP_STATS,	      "Return counters"},
	{DCC_AOP_STATS_CLEAR, "Return and zero counters"},
	{DCC_AOP_TRACE_ON,    "Enable tracing"},
	{DCC_AOP_TRACE_OFF,   "Disable tracing"},
	{DCC_AOP_CUR_CLIENTS, "List clients"},
	{0, NULL},
};

static const value_string dcc_target_vals[] = {
	{DCC_TGTS_TOO_MANY, "Targets (>= 16777200)"},
	{DCC_TGTS_OK,	    "Certified not spam"},
	{DCC_TGTS_OK2,	    "Half certified not spam"},
	{DCC_TGTS_DEL,	    "Deleted checksum"},
	{DCC_TGTS_INVALID,  "Invalid"},
	{0, NULL},
};

static const value_string dcc_floodop_vals[] = {
	{DCC_AOP_FLOD_CHECK,	   "Check"},
	{DCC_AOP_FLOD_SHUTDOWN,	   "Shutdown"},
	{DCC_AOP_FLOD_HALT,	   "Halt"},
	{DCC_AOP_FLOD_RESUME,	   "Resume"},
	{DCC_AOP_FLOD_REWIND,	   "Rewind"},
	{DCC_AOP_FLOD_LIST,	   "List"},
	{DCC_AOP_FLOD_STATS,	   "Stats"},
	{DCC_AOP_FLOD_STATS_CLEAR, "Clear Stats"},
	{0,NULL},
};

static gboolean
dissect_dcc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
	proto_tree *dcc_tree, *dcc_optree, *dcc_opnumtree, *ti;
	proto_tree *dcc_tracetree;
	proto_item *len_item;
	int offset = 0;
	int client_is_le = 0;
	int op = 0;
	int i, is_response;

	if (pinfo->srcport != DCC_PORT && pinfo->destport != DCC_PORT) {
		/* Not the right port - not a DCC packet. */
		return FALSE;
	}

	/* get at least a full packet structure */
	if ( tvb_reported_length(tvb) < sizeof(DCC_HDR) ) {
		/* Doesn't have enough bytes to contain packet header. */
		return FALSE;
	}

	col_set_str(pinfo->cinfo, COL_PROTOCOL, "DCC");

	offset = 0;
	is_response = pinfo->srcport == DCC_PORT;

	col_add_fstr(pinfo->cinfo, COL_INFO,
		"%s: %s",
		is_response ? "Response" : "Request",
		val_to_str(tvb_get_guint8(tvb, offset+3),
			 dcc_op_vals, "Unknown Op: %u"));

	ti = proto_tree_add_item(tree, proto_dcc, tvb, offset, -1,
		ENC_NA);
	dcc_tree = proto_item_add_subtree(ti, ett_dcc);

	len_item = proto_tree_add_item(dcc_tree, hf_dcc_len, tvb,
		offset, 2, ENC_BIG_ENDIAN);

	if ( tvb_reported_length(tvb) < tvb_get_ntohs(tvb, offset)) {
		/* Doesn't have number of bytes that header claims. */
		expert_add_info(pinfo, len_item, &ei_dcc_len);
	}
	offset += 2;

	if (tree) {
		proto_tree_add_item(dcc_tree, hf_dcc_pkt_vers, tvb,
			offset, 1, ENC_BIG_ENDIAN);
		offset += 1;

		op = tvb_get_guint8(tvb, offset);
		proto_tree_add_item(dcc_tree, hf_dcc_op, tvb,
			offset, 1, ENC_BIG_ENDIAN);
		offset += 1;

		proto_tree_add_item(dcc_tree, hf_dcc_clientid, tvb,
			offset, 4, ENC_BIG_ENDIAN);
		offset += 4;

		dcc_opnumtree = proto_tree_add_subtree(dcc_tree, tvb, offset, -1, ett_dcc_opnums, NULL, "Operation Numbers (Opaque to Server)");

		/* Note - these are indeterminate - they are sortof considered opaque to the client */
		/* Make some attempt to figure out if this data is little endian, not guaranteed to be
		correct if connection went through a firewall or similar. */

		/* Very hokey check - if all three of pid/report/retrans look like little-endian
			numbers, host is probably little endian. Probably innacurate on super-heavily-used
			DCC clients though. This should be good enough for now. */
		client_is_le = ( (tvb_get_guint8(tvb, offset+4) | tvb_get_guint8(tvb, offset+5)) &&
						 (tvb_get_guint8(tvb, offset+8) | tvb_get_guint8(tvb, offset+9)) &&
						 (tvb_get_guint8(tvb, offset+12) | tvb_get_guint8(tvb, offset+13)) );

		proto_tree_add_item(dcc_opnumtree, hf_dcc_opnums_host, tvb,
			offset, 4, client_is_le);
		offset += 4;

		proto_tree_add_item(dcc_opnumtree, hf_dcc_opnums_pid, tvb,
			offset, 4, client_is_le);
		offset += 4;

		proto_tree_add_item(dcc_opnumtree, hf_dcc_opnums_report, tvb,
			offset, 4, client_is_le);
		offset += 4;

		proto_tree_add_item(dcc_opnumtree, hf_dcc_opnums_retrans, tvb,
			offset, 4, client_is_le);
		offset += 4;

		dcc_optree = proto_tree_add_subtree_format(dcc_tree, tvb, offset, -1, ett_dcc_op, NULL,
			"Operation: %s", val_to_str(op, dcc_op_vals, "Unknown Op: %u"));

		switch(op) {
			case DCC_OP_NOP:
				D_SIGNATURE();
				break;

			case DCC_OP_REPORT:
				D_TARGET();
				for (i=0; i<=DCC_QUERY_MAX &&
					tvb_bytes_exist(tvb, offset+(int)sizeof(DCC_SIGNATURE),1); i++)
				{
					D_CHECKSUM();
				}
				D_SIGNATURE();
				break;

			case DCC_OP_QUERY_RESP:
				for (i=0; i<=DCC_QUERY_MAX &&
					tvb_bytes_exist(tvb, offset+(int)sizeof(DCC_SIGNATURE),1); i++)
				{
					D_TARGET();
				}
				D_SIGNATURE();
				break;

			case DCC_OP_ADMN:
				if ( is_response )
				{
					int left_local = tvb_reported_length_remaining(tvb, offset) -
						(int)sizeof(DCC_SIGNATURE);
					if ( left_local == sizeof(DCC_ADMN_RESP_CLIENTS) )
					{
						D_LABEL(hf_dcc_addr, 16, ENC_NA);
						D_LABEL(hf_dcc_id, (int)sizeof(DCC_CLNT_ID), ENC_BIG_ENDIAN);
						D_LABEL(hf_dcc_last_used, 4, ENC_BIG_ENDIAN);
						D_LABEL(hf_dcc_requests, 4, ENC_BIG_ENDIAN);
					}
					else
					{
						D_TEXT(hf_dcc_response_text, (int)sizeof(DCC_SIGNATURE));
					}
					D_SIGNATURE();
				}
				else
				{
					int aop;

					D_DATE();

					aop = tvb_get_guint8(tvb, offset+4);
					proto_tree_add_item(dcc_optree, hf_dcc_adminop, tvb, offset+4,
						1, ENC_BIG_ENDIAN);
					col_append_fstr(pinfo->cinfo, COL_INFO, ", %s",
						val_to_str(tvb_get_guint8(tvb,offset+4),
						dcc_adminop_vals, "Unknown (%u)"));

					if (aop == DCC_AOP_TRACE_ON || aop == DCC_AOP_TRACE_OFF )
					{
						ti = proto_tree_add_item(dcc_optree, hf_dcc_trace, tvb, offset,
							4, ENC_BIG_ENDIAN);
						dcc_tracetree = proto_item_add_subtree(ti, ett_dcc_trace);
						proto_tree_add_item(dcc_tracetree, hf_dcc_trace_admin, tvb, offset, 4, ENC_BIG_ENDIAN);
						proto_tree_add_item(dcc_tracetree, hf_dcc_trace_anon, tvb, offset, 4, ENC_BIG_ENDIAN);
						proto_tree_add_item(dcc_tracetree, hf_dcc_trace_client, tvb, offset, 4, ENC_BIG_ENDIAN);
						proto_tree_add_item(dcc_tracetree, hf_dcc_trace_rlim, tvb, offset, 4, ENC_BIG_ENDIAN);
						proto_tree_add_item(dcc_tracetree, hf_dcc_trace_query, tvb, offset, 4, ENC_BIG_ENDIAN);
						proto_tree_add_item(dcc_tracetree, hf_dcc_trace_ridc, tvb, offset, 4, ENC_BIG_ENDIAN);
						proto_tree_add_item(dcc_tracetree, hf_dcc_trace_flood, tvb, offset, 4, ENC_BIG_ENDIAN);
					}
					else if ( aop == DCC_AOP_FLOD )
					{
						proto_tree_add_item(dcc_optree, hf_dcc_floodop,
							tvb, offset, 4, ENC_BIG_ENDIAN);
						col_append_fstr(pinfo->cinfo, COL_INFO, ", %s",
							val_to_str(tvb_get_ntohl(tvb,offset),
							dcc_floodop_vals, "Unknown (%u)"));
					}
					else
					{
						proto_tree_add_item(dcc_optree, hf_dcc_adminval,
							tvb, offset, 4, ENC_BIG_ENDIAN);
					}
					offset += 4;

					offset += 1; /* admin op we did in reverse order */
					D_LABEL(hf_dcc_pad, 3, ENC_NA);
					D_SIGNATURE();
				}
				break;

			case DCC_OP_OK:
				proto_tree_add_item(dcc_optree, hf_dcc_max_pkt_vers, tvb,
					offset, 1, ENC_BIG_ENDIAN);
				offset += 1;

				D_LABEL(hf_dcc_unused, 1, ENC_NA);

				proto_tree_add_item(dcc_optree, hf_dcc_qdelay_ms, tvb,
					offset, 2, ENC_BIG_ENDIAN);
				offset += 2;

				proto_tree_add_item(dcc_optree, hf_dcc_brand, tvb,
					offset, (int)sizeof(DCC_BRAND), ENC_ASCII);
				offset += (int)sizeof(DCC_BRAND);

				D_SIGNATURE();
				break;

			default:
				/* do nothing */
				break;
		}
	}

	return TRUE;
}

void
proto_register_dcc(void)
{
	static hf_register_info hf[] = {
			{ &hf_dcc_len, {
				"Packet Length", "dcc.len", FT_UINT16, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_pkt_vers, {
				"Packet Version", "dcc.pkt_vers", FT_UINT16, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_op, {
				"Operation Type", "dcc.op", FT_UINT8, BASE_DEC,
				VALS(dcc_op_vals), 0, NULL, HFILL }},

			{ &hf_dcc_clientid, {
				"Client ID", "dcc.clientid", FT_UINT32, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_opnums_host, {
				"Host", "dcc.opnums.host", FT_UINT32, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_opnums_pid, {
				"Process ID", "dcc.opnums.pid", FT_UINT32, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_opnums_report, {
				"Report", "dcc.opnums.report", FT_UINT32, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_opnums_retrans, {
				"Retransmission", "dcc.opnums.retrans", FT_UINT32, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_signature, {
				"Signature", "dcc.signature", FT_BYTES, BASE_NONE,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_max_pkt_vers, {
				"Maximum Packet Version", "dcc.max_pkt_vers", FT_UINT8, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_qdelay_ms, {
				"Client Delay", "dcc.qdelay_ms", FT_UINT16, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_brand, {
				"Server Brand", "dcc.brand", FT_STRING, BASE_NONE,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_ck_type, {
				"Type", "dcc.checksum.type", FT_UINT8, BASE_DEC,
				VALS(dcc_cktype_vals), 0, "Checksum Type", HFILL }},

			{ &hf_dcc_ck_len, {
				"Length", "dcc.checksum.length", FT_UINT8, BASE_DEC,
				NULL, 0, "Checksum Length", HFILL }},

			{ &hf_dcc_ck_sum, {
				"Sum", "dcc.checksum.sum", FT_BYTES, BASE_NONE,
				NULL, 0, "Checksum", HFILL }},

			{ &hf_dcc_target, {
				"Target", "dcc.target", FT_UINT32, BASE_HEX,
				VALS(dcc_target_vals), 0, NULL, HFILL }},

			{ &hf_dcc_response_text, {
				"Response Text", "dcc.response_text", FT_BYTES, BASE_NONE,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_date, {
				"Date", "dcc.date", FT_ABSOLUTE_TIME, ABSOLUTE_TIME_LOCAL,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_adminop, {
				"Admin Op", "dcc.adminop", FT_UINT8, BASE_DEC,
				VALS(dcc_adminop_vals), 0, NULL, HFILL }},

			{ &hf_dcc_adminval, {
				"Admin Value", "dcc.adminval", FT_UINT32, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_trace, {
				"Trace Bits", "dcc.trace", FT_UINT32, BASE_HEX,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_trace_admin, {
				"Admin Requests", "dcc.trace.admin", FT_BOOLEAN, 32,
				NULL, 0x00000001, NULL, HFILL }},

			{ &hf_dcc_trace_anon, {
				"Anonymous Requests", "dcc.trace.anon", FT_BOOLEAN, 32,
				NULL, 0x00000002, NULL, HFILL }},

			{ &hf_dcc_trace_client, {
				"Authenticated Client Requests", "dcc.trace.client", FT_BOOLEAN, 32,
				NULL, 0x00000004, NULL, HFILL }},

			{ &hf_dcc_trace_rlim, {
				"Rate-Limited Requests", "dcc.trace.rlim", FT_BOOLEAN, 32,
				NULL, 0x00000008, NULL, HFILL }},

			{ &hf_dcc_trace_query, {
				"Queries and Reports", "dcc.trace.query", FT_BOOLEAN, 32,
				NULL, 0x00000010, NULL, HFILL }},

			{ &hf_dcc_trace_ridc, {
				"RID Cache Messages", "dcc.trace.ridc", FT_BOOLEAN, 32,
				NULL, 0x00000020, NULL, HFILL }},

			{ &hf_dcc_trace_flood, {
				"Input/Output Flooding", "dcc.trace.flood", FT_BOOLEAN, 32,
				NULL, 0x00000040, NULL, HFILL }},

			{ &hf_dcc_floodop, {
				"Flood Control Operation", "dcc.floodop", FT_UINT32, BASE_DEC,
				VALS(dcc_floodop_vals), 0, NULL, HFILL }},

			{ &hf_dcc_id, {
				"Id", "dcc.id", FT_UINT32, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_last_used, {
				"Last Used", "dcc.last_used", FT_UINT32, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_requests, {
				"Requests", "dcc.requests", FT_UINT32, BASE_DEC,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_addr, {
				"Addr", "dcc.addr", FT_BYTES, BASE_NONE,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_pad, {
				"Pad", "dcc.pad", FT_BYTES, BASE_NONE,
				NULL, 0, NULL, HFILL }},

			{ &hf_dcc_unused, {
				"Unused", "dcc.unused", FT_BYTES, BASE_NONE,
				NULL, 0, NULL, HFILL }},
		};

	static gint *ett[] = {
		&ett_dcc,
		&ett_dcc_op,
		&ett_dcc_ck,
		&ett_dcc_opnums,
		&ett_dcc_trace,
	};

	static ei_register_info ei[] = {
		{ &ei_dcc_len, { "dcc.len.short", PI_MALFORMED, PI_ERROR, "Error - packet is shorter than header claims!", EXPFILL }},
	};

	expert_module_t* expert_dcc;

	proto_dcc = proto_register_protocol("Distributed Checksum Clearinghouse protocol", "DCC", "dcc");

	proto_register_field_array(proto_dcc, hf, array_length(hf));
	proto_register_subtree_array(ett, array_length(ett));
	expert_dcc = expert_register_protocol(proto_dcc);
	expert_register_field_array(expert_dcc, ei, array_length(ei));
}

void
proto_reg_handoff_dcc(void)
{
	heur_dissector_add("udp", dissect_dcc, "Distributed Checksum Clearinghouse over UDP", "dcc_udp", proto_dcc, HEURISTIC_ENABLE);
}

/*
 * 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:
 */