--- sourceforge.net/trunk/rdesktop/mcs.c	2000/07/25 12:34:29	9
+++ sourceforge.net/trunk/rdesktop/mcs.c	2000/08/15 10:23:24	10
@@ -18,567 +18,358 @@
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
-#include "includes.h"
+#include "rdesktop.h"
 
-/* Establish a connection up to the MCS layer */
-HCONN mcs_connect(char *server)
-{
-	HCONN conn;
-	MCS_CONNECT_RESPONSE mcr;
-	MCS_AUCF aucf;
+uint16 mcs_userid;
 
-	if ((conn = iso_connect(server)) == NULL)
-		return NULL;
+/* Parse an ASN.1 BER header */
+static BOOL ber_parse_header(STREAM s, int tagval, int *length)
+{
+	int tag, len;
 
-	mcs_send_connect_initial(conn);
-	if (!iso_recv(conn) || !mcs_io_connect_response(&conn->in, &mcr))
+	if (tagval > 0xff)
 	{
-		ERROR("MCS error, expected Connect-Response\n");
-		iso_disconnect(conn);
-		return NULL;
+		in_uint16_be(s, tag);
 	}
-
-	if (mcr.result != 0)
-	{
-		ERROR("MCS-Connect-Initial failed, result %d\n", mcr.result);
-		iso_disconnect(conn);
-		return NULL;
-	}
-
-	mcs_send_edrq(conn);
-
-	mcs_send_aurq(conn);
-	if (!iso_recv(conn) || !mcs_io_aucf(&conn->in, &aucf))
+	else
 	{
-		ERROR("MCS error, expected AUcf\n");
-		mcs_disconnect(conn);
-		return NULL;
+		in_uint8(s, tag)
 	}
 
-	if (aucf.result != 0)
+	if (tag != tagval)
 	{
-		ERROR("AUrq failed, result %d\n", mcr.result);
-		mcs_disconnect(conn);
-		return NULL;
+		ERROR("expected tag %d, got %d\n", tagval, tag);
+		return False;
 	}
 
-	conn->mcs_userid = aucf.userid;
+	in_uint8(s, len);
 
-	if (!mcs_join_channel(conn, aucf.userid + 1001)
-	    || !mcs_join_channel(conn, MCS_GLOBAL_CHANNEL))
+	if (len & 0x80)
 	{
-		mcs_disconnect(conn);
-		return NULL;
+		len &= ~0x80;
+		*length = 0;
+		while (len--)
+			next_be(s, *length);
 	}
+	else *length = len;
 
-	return conn;
+	return s_check(s);
 }
 
-BOOL mcs_join_channel(HCONN conn, uint16 chanid)
+/* Output an ASN.1 BER header */
+static void ber_out_header(STREAM s, int tagval, int length)
 {
-	MCS_CJCF cjcf;
-
-	mcs_send_cjrq(conn, chanid);
-	if (!iso_recv(conn) || !mcs_io_cjcf(&conn->in, &cjcf))
+	if (tagval > 0xff)
 	{
-		ERROR("MCS error, expected CJcf\n");
-		return False;
+		out_uint16_be(s, tagval);
 	}
-
-	if (cjcf.result != 0)
+	else
 	{
-		ERROR("CJrq failed, result %d\n", cjcf.result);
-		return False;
+		out_uint8(s, tagval);
 	}
 
-	return True;
+	if (length >= 0x80)
+	{
+		out_uint8(s, 0x82);
+		out_uint16_be(s, length);
+	}
+	else out_uint8(s, length);
 }
 
-/* Disconnect from the MCS layer */
-void mcs_disconnect(HCONN conn)
+/* Output an ASN.1 BER integer */
+static void ber_out_integer(STREAM s, int value)
 {
-	/* Not complete */
-	iso_disconnect(conn);
+	ber_out_header(s, BER_TAG_INTEGER, 2);
+	out_uint16_be(s, value);
 }
 
-/* Send a Connect-Initial message */
-void mcs_send_connect_initial(HCONN conn)
+/* Output a DOMAIN_PARAMS structure (ASN.1 BER) */
+static void mcs_out_domain_params(STREAM s, int max_channels, int max_users,
+			   int max_tokens, int max_pdusize)
 {
-	MCS_CONNECT_INITIAL mci;
-
-	iso_init(conn);
-	mcs_make_connect_initial(&mci);
-	mcs_io_connect_initial(&conn->out, &mci);
-	MARK_END(conn->out);
-	iso_send(conn);
+	ber_out_header(s, MCS_TAG_DOMAIN_PARAMS, 32);
+	ber_out_integer(s, max_channels);
+	ber_out_integer(s, max_users);
+	ber_out_integer(s, max_tokens);
+	ber_out_integer(s, 1); /* num_priorities */
+	ber_out_integer(s, 0); /* min_throughput */
+	ber_out_integer(s, 1); /* max_height */
+	ber_out_integer(s, max_pdusize);
+	ber_out_integer(s, 2); /* ver_protocol */
 }
 
-/* Send a EDrq message */
-void mcs_send_edrq(HCONN conn)
+/* Parse a DOMAIN_PARAMS structure (ASN.1 BER) */
+static BOOL mcs_parse_domain_params(STREAM s)
 {
-	MCS_EDRQ edrq;
+	int length;
 
-	iso_init(conn);
-	edrq.height = edrq.interval = 1;
-	mcs_io_edrq(&conn->out, &edrq);
-	MARK_END(conn->out);
-	iso_send(conn);
+	ber_parse_header(s, MCS_TAG_DOMAIN_PARAMS, &length);
+	in_uint8s(s, length);
+
+	return s_check(s);
 }
 
-/* Send a AUrq message */
-void mcs_send_aurq(HCONN conn)
+/* Send an MCS_CONNECT_INITIAL message (ASN.1 BER) */
+static void mcs_send_connect_initial(STREAM mcs_data)
 {
-	MCS_AURQ aurq;
+	int datalen = mcs_data->end - mcs_data->data;
+	int length = 7 + 3*34 + 4 + datalen;
+	STREAM s;
 
-	iso_init(conn);
-	mcs_io_aurq(&conn->out, &aurq);
-	MARK_END(conn->out);
-	iso_send(conn);
-}
+	s = iso_init(length + 5);
 
-/* Send a CJrq message */
-void mcs_send_cjrq(HCONN conn, uint16 chanid)
-{
-	MCS_CJRQ cjrq;
+	ber_out_header(s, MCS_CONNECT_INITIAL, length);
+	ber_out_header(s, BER_TAG_OCTET_STRING, 0); /* calling domain */
+	ber_out_header(s, BER_TAG_OCTET_STRING, 0); /* called domain */
 
-	iso_init(conn);
-	cjrq.userid = conn->mcs_userid;
-	cjrq.chanid = chanid;
-	mcs_io_cjrq(&conn->out, &cjrq);
-	MARK_END(conn->out);
-	iso_send(conn);
-}
+	ber_out_header(s, BER_TAG_BOOLEAN, 1);
+	out_uint8(s, 0xff); /* upward flag */
 
-/* Initialise MCS transport data packet */
-void mcs_init_data(HCONN conn)
-{
-	iso_init(conn);
-	PUSH_LAYER(conn->out, mcs_offset, 8);
-}
+	mcs_out_domain_params(s, 2, 2, 0, 0xffff); /* target params */
+	mcs_out_domain_params(s, 1, 1, 1, 0x420); /* min params */
+	mcs_out_domain_params(s, 0xffff, 0xfc17, 0xffff, 0xffff); /* max params */
 
-/* Transmit MCS transport data packet */
-void mcs_send_data(HCONN conn, uint16 chanid, BOOL request)
-{
-	MCS_DATA dt;
+	ber_out_header(s, BER_TAG_OCTET_STRING, datalen);
+	out_uint8p(s, mcs_data->data, datalen);
 
-	POP_LAYER(conn->out, mcs_offset);
-	dt.userid = conn->mcs_userid;
-	dt.chanid = chanid;
-	dt.flags = 0x70;
-	dt.length = conn->out.end - conn->out.offset - 8;
-	mcs_io_data(&conn->out, &dt, request);
-	iso_send(conn);
+	s_mark_end(s);
+	iso_send(s);
 }
 
-/* Receive a message on the MCS layer */
-BOOL mcs_recv(HCONN conn, BOOL request)
+/* Expect a MCS_CONNECT_RESPONSE message (ASN.1 BER) */
+static BOOL mcs_recv_connect_response(STREAM mcs_data)
 {
-	MCS_DATA data;
+	uint8 result;
+	int length;
+	STREAM s;
 
-	if (!iso_recv(conn) || !mcs_io_data(&conn->in, &data, request))
+	s = iso_recv();
+	if (s == NULL)
 		return False;
 
-	conn->in.rdp_offset = conn->in.offset;
-	return True;
-}
-
-/* Initialise a DOMAIN_PARAMS structure */
-void mcs_make_domain_params(DOMAIN_PARAMS *dp, uint16 max_channels,
-	      uint16 max_users, uint16 max_tokens, uint16 max_pdusize)
-{
-	dp->max_channels   = max_channels;
-	dp->max_users      = max_users;
-	dp->max_tokens     = max_tokens;
-	dp->num_priorities = 1;
-	dp->min_throughput = 0;
-	dp->max_height     = 1;
-	dp->max_pdusize    = max_pdusize;
-	dp->ver_protocol   = 2;
-}
-
-/* RDP-specific 'user data'. Let's just get this right for now - to be
-   decoded later. */
-char precanned_connect_userdata[] = {
-   0x00,0x05,0x00,0x14,0x7c,0x00,0x01,0x80,0x9e,0x00,0x08,0x00,0x10,0x00,
-   0x01,0xc0,0x00,0x44,0x75,0x63,0x61,0x80,0x90,0x01,0xc0,0x88,0x00,0x01,
-   0x00,0x08,0x00,0x80,0x02,0xe0,0x01,0x01,0xca,0x03,0xaa,0x09,0x04,0x00,
-   0x00,0xa3,0x01,0x00,0x00,0x52,0x00,0x45,0x00,0x53,0x00,0x31,0x00,0x2d,
-   0x00,0x4e,0x00,0x45,0x00,0x57,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-   0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x04,0x00,0x00,0x00,0x00,
-   0x00,0x00,0x00,0x0c,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-   0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-   0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-   0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-   0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-   0x00,0x01,0xca,0x00,0x00,0x02,0xc0,0x08,0x00,
-   /* encryption disabled */ 0x00,0x00,0x00,0x00 };
-
-char precanned_connect_userdata_e[] = {
-0x00,
-0x05,0x00,0x14,0x7c,0x00,0x01,0x80,0x9e,0x00,0x08,0x00,0x10,0x00,0x01,0xc0,0x00,
-0x44,0x75,0x63,0x61,0x80,0x90,0x01,0xc0,0x88,0x00,0x01,0x00,0x08,0x00,0x80,0x02,
-0xe0,0x01,0x01,0xca,0x03,0xaa,0x09,0x04,0x00,0x00,0xa3,0x01,0x00,0x00,0x57,0x00,
-0x49,0x00,0x4e,0x00,0x39,0x00,0x35,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x04,0x00,
-0x00,0x00,0x00,0x00,0x00,0x00,0x0c,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0xca,0x00,0x00,0x02,0xc0,
-0x08,0x00,0x01,0x00,0x00,0x00
-};
-
-char domain_data[] = {0x01};
-
-/* Initialise a MCS_CONNECT_INITIAL structure */
-void mcs_make_connect_initial(MCS_CONNECT_INITIAL *mci)
-{
-	mci->calling_domain.length = 1;
-	mci->calling_domain.data = domain_data;
-
-	mci->called_domain.length = 1;
-	mci->called_domain.data = domain_data;
-
-	mci->upward_flag = 0xff;
-
-	mcs_make_domain_params(&mci->target_params,  2, 2, 0, 0xffff);
-	mcs_make_domain_params(&mci->minimum_params, 1, 1, 1, 0x420);
-	mcs_make_domain_params(&mci->maximum_params, 0xffff, 0xfc17, 0xffff,
-			       0xffff);
-
-	mci->user_data.length = sizeof(precanned_connect_userdata);
-	mci->user_data.data = precanned_connect_userdata;
-
-	mci->length = 2*2 + 3 + 3*34 + 4 + mci->user_data.length;
-}
-
-/* Marshall/demarshall an ASN.1 BER header */
-BOOL ber_io_header(STREAM s, BOOL islong, int tagval, int *length)
-{
-	uint16 word_tag;
-	uint8 byte_tag;
-	uint16 word_len;
-	uint8 byte_len;
-	uint8 byte_int;
-	int tag;
-	BOOL res;
-
-	/* Read/write tag */
-	if (islong)
-	{
-		word_tag = tagval;
-		res = msb_io_uint16(s, &word_tag);
-		tag = word_tag;
-	}
-	else
-	{
-		byte_tag = tagval;
-		res = prs_io_uint8(s, &byte_tag);
-		tag = byte_tag;
-	}
+	ber_parse_header(s, MCS_CONNECT_RESPONSE, &length);
 
-	if (!res || (tag != tagval))
+	ber_parse_header(s, BER_TAG_RESULT, &length);
+	in_uint8(s, result);
+	if (result != 0)
 	{
-		ERROR("Invalid ASN.1 tag\n");
+		ERROR("MCS connect: %d\n", result);
 		return False;
 	}
 
-	/* Read/write length */
-	if (s->marshall)
+	ber_parse_header(s, BER_TAG_INTEGER, &length);
+	in_uint8s(s, length); /* connect id */
+	mcs_parse_domain_params(s);
+
+	ber_parse_header(s, BER_TAG_OCTET_STRING, &length);
+	if (length > mcs_data->size)
 	{
-		if (*length >= 0x80)
-		{
-			byte_len = 0x82;
-			word_len = (uint16)*length;
-			res = prs_io_uint8(s, &byte_len);
-			res = res ? msb_io_uint16(s, &word_len) : False;
-		}
-		else
-		{
-			byte_len = (uint8)*length;
-			res = prs_io_uint8(s, &byte_len);
-		}
+		WARN("MCS data length %d\n", length);
+		length = mcs_data->size;
 	}
-	else
-	{
-		if (!prs_io_uint8(s, &byte_len))
-			return False;
 
-		if (byte_len & 0x80)
-		{
-			byte_len &= ~0x80;
-			*length = 0;
-			while (byte_len--)
-			{
-				if (!prs_io_uint8(s, &byte_int))
-					return False;
-
-				*length <<= 8;
-				*length += byte_int;
-			}
-		}
-		else *length = byte_len;
-	}
+	in_uint8a(s, mcs_data->data, length);
+	mcs_data->p = mcs_data->data;
+	mcs_data->end = mcs_data->data + length;
 
-	return res;
+	return s_check_end(s);
 }
 
-/* Marshall/demarshall an octet string (ASN.1 BER) */
-BOOL ber_io_octet_string(STREAM s, OCTET_STRING *os)
+/* Send an EDrq message (ASN.1 PER) */
+static void mcs_send_edrq()
 {
-	if (!ber_io_header(s, False, 4, &os->length))
-		return False;
+	STREAM s;
 
-	if (os->length > s->end - s->offset)
-		return False;
+	s = iso_init(5);
 
-	if (s->marshall)
-	{
-		memcpy(s->data + s->offset, os->data, os->length);
-	}
-	else
-	{
-		os->data = malloc(os->length);
-		memcpy(os->data, s->data + s->offset, os->length);
-	}
+	out_uint8(s, (MCS_EDRQ << 2));
+	out_uint16_be(s, 1); /* height */
+	out_uint16_be(s, 1); /* interval */
 
-	s->offset += os->length;
-	return True;
+	s_mark_end(s);
+	iso_send(s);
 }
 
-/* Marshall/demarshall an integer (ASN.1 BER) */
-BOOL ber_io_integer(STREAM s, uint16 *word_int)
+/* Send an AUrq message (ASN.1 PER) */
+static void mcs_send_aurq()
 {
-	int length = 2;
-	uint8 byte_int;
-	BOOL res;
-
-	if (!ber_io_header(s, False, 2, &length))
-		return False;
+	STREAM s;
 
-	if (s->marshall)
-	{
-		res = msb_io_uint16(s, word_int);
-	}
-	else
-	{
-		*word_int = 0;
-		while (length--)
-		{
-			if (!prs_io_uint8(s, &byte_int))
-				return False;
+	s = iso_init(1);
 
-			*word_int <<= 8;
-			*word_int += byte_int;
-		}
-	}
+	out_uint8(s, (MCS_AURQ << 2));
 
-	return res;
+	s_mark_end(s);
+	iso_send(s);
 }
 
-/* Marshall/demarshall a simple uint8 type (ASN.1 BER) */
-BOOL ber_io_uint8(STREAM s, uint8 *i, int tagval)
+/* Expect a AUcf message (ASN.1 PER) */
+static BOOL mcs_recv_aucf(uint16 *mcs_userid)
 {
-	int length = 1;
+	uint8 opcode, result;
+	STREAM s;
 
-	if (!ber_io_header(s, False, tagval, &length))
+	s = iso_recv();
+	if (s == NULL)
 		return False;
 
-	if (length != 1)
+	in_uint8(s, opcode);
+	if ((opcode >> 2) != MCS_AUCF)
 	{
-		ERROR("Wrong length for simple type\n");
+		ERROR("expected AUcf, got %d\n", opcode);
 		return False;
 	}
 
-	return prs_io_uint8(s, i);
-}
-
-/* Marshall/demarshall a DOMAIN_PARAMS structure (ASN.1 BER) */
-BOOL mcs_io_domain_params(STREAM s, DOMAIN_PARAMS *dp)
-{
-	int length = 32;
-	BOOL res;
+	in_uint8(s, result);
+	if (result != 0)
+	{
+		ERROR("AUrq: %d\n", result);
+		return False;
+	}
 
-	res = ber_io_header(s, False, 0x30, &length);
-	res = res ? ber_io_integer(s, &dp->max_channels  ) : False;
-	res = res ? ber_io_integer(s, &dp->max_users     ) : False;
-	res = res ? ber_io_integer(s, &dp->max_tokens    ) : False;
-	res = res ? ber_io_integer(s, &dp->num_priorities) : False;
-	res = res ? ber_io_integer(s, &dp->min_throughput) : False;
-	res = res ? ber_io_integer(s, &dp->max_height    ) : False;
-	res = res ? ber_io_integer(s, &dp->max_pdusize   ) : False;
-	res = res ? ber_io_integer(s, &dp->ver_protocol  ) : False;
+	if (opcode & 2)
+		in_uint16_be(s, *mcs_userid);
 
-	return res;
+	return s_check_end(s);
 }
 
-/* Marshall/demarshall a MCS_CONNECT_INITIAL structure (ASN.1 BER) */
-BOOL mcs_io_connect_initial(STREAM s, MCS_CONNECT_INITIAL *mci)
+/* Send a CJrq message (ASN.1 PER) */
+static void mcs_send_cjrq(uint16 chanid)
 {
-	BOOL res;
+	STREAM s;
 
-	res = ber_io_header(s, True, 0x7f65, &mci->length);
-	res = res ? ber_io_octet_string (s, &mci->calling_domain) : False;
-	res = res ? ber_io_octet_string (s, &mci->called_domain ) : False;
-        res = res ? ber_io_uint8        (s, &mci->upward_flag, 1) : False;
-	res = res ? mcs_io_domain_params(s, &mci->target_params ) : False;
-	res = res ? mcs_io_domain_params(s, &mci->minimum_params) : False;
-	res = res ? mcs_io_domain_params(s, &mci->maximum_params) : False;
-	res = res ? ber_io_octet_string (s, &mci->user_data     ) : False;
+	s = iso_init(5);
 
-	return res;
+	out_uint8(s, (MCS_CJRQ << 2));
+	out_uint16_be(s, mcs_userid);
+	out_uint16_be(s, chanid);
+
+	s_mark_end(s);
+	iso_send(s);
 }
 
-/* Marshall/demarshall a MCS_CONNECT_RESPONSE structure (ASN.1 BER) */
-BOOL mcs_io_connect_response(STREAM s, MCS_CONNECT_RESPONSE *mcr)
+/* Expect a CJcf message (ASN.1 PER) */
+static BOOL mcs_recv_cjcf()
 {
-	BOOL res;
-
-	res = ber_io_header(s, True, 0x7f66, &mcr->length);
-	res = res ? ber_io_uint8        (s, &mcr->result, 10   ) : False;
-	res = res ? ber_io_integer      (s, &mcr->connect_id   ) : False;
-	res = res ? mcs_io_domain_params(s, &mcr->domain_params) : False;
-	res = res ? ber_io_octet_string (s, &mcr->user_data    ) : False;
+	uint8 opcode, result;
+	STREAM s;
 
-	return res;
-}
+	s = iso_recv();
+	if (s == NULL)
+		return False;
 
-/* Marshall/demarshall an EDrq structure (ASN.1 PER) */
-BOOL mcs_io_edrq(STREAM s, MCS_EDRQ *edrq)
-{
-	uint8 opcode = (1) << 2;
-	uint8 pkt_opcode = opcode;
-	BOOL res;
+	in_uint8(s, opcode);
+	if ((opcode >> 2) != MCS_CJCF)
+	{
+		ERROR("expected CJcf, got %d\n", opcode);
+		return False;
+	}
 
-	res = prs_io_uint8(s, &pkt_opcode);
-	if (pkt_opcode != opcode)
+	in_uint8(s, result);
+	if (result != 0)
 	{
-		ERROR("Expected EDrq, received %x\n", pkt_opcode);
+		ERROR("CJrq: %d\n", result);
 		return False;
 	}
 
-	res = res ? msb_io_uint16(s, &edrq->height  ) : False;
-	res = res ? msb_io_uint16(s, &edrq->interval) : False;
+	in_uint8s(s, 4); /* mcs_userid, req_chanid */
+	if (opcode & 2)
+		in_uint8s(s, 2); /* join_chanid */
 
-	return res;
+	return s_check_end(s);
 }
 
-/* Marshall/demarshall an AUrq structure (ASN.1 PER) */
-BOOL mcs_io_aurq(STREAM s, MCS_AURQ *aurq)
+/* Initialise an MCS transport data packet */
+STREAM mcs_init(int length)
 {
-	uint8 opcode = (10) << 2;
-	uint8 pkt_opcode = opcode;
-	BOOL res;
+	STREAM s;
 
-	res = prs_io_uint8(s, &pkt_opcode);
-	if (pkt_opcode != opcode)
-	{
-		ERROR("Expected AUrq, received %x\n", pkt_opcode);
-		return False;
-	}
+	s = iso_init(length + 8);
+	s_push_layer(s, mcs_hdr, 8);
 
-	return res;
+	return s;
 }
 
-/* Marshall/demarshall an AUcf structure (ASN.1 PER) */
-BOOL mcs_io_aucf(STREAM s, MCS_AUCF *aucf)
+/* Send an MCS transport data packet */
+void mcs_send(STREAM s)
 {
-	uint8 opcode = (11) << 2;
-	uint8 pkt_opcode = opcode | 2;
-	BOOL res;
+	uint16 length;
 
-	res = prs_io_uint8(s, &pkt_opcode);
-	if ((pkt_opcode & 0xfc) != opcode)
-	{
-		ERROR("Expected AUcf, received %x\n", pkt_opcode);
-		return False;
-	}
+	s_pop_layer(s, mcs_hdr);
+	length = s->end - s->p - 8;
+	length |= 0x8000;
 
-	res = res ? prs_io_uint8 (s, &aucf->result) : False;
-	if (pkt_opcode & 2)
-		res = res ? msb_io_uint16(s, &aucf->userid) : False;
+	out_uint8(s, (MCS_SDRQ << 2));
+	out_uint16_be(s, mcs_userid);
+	out_uint16_be(s, MCS_GLOBAL_CHANNEL);
+	out_uint8(s, 0x70); /* flags */
+	out_uint16_be(s, length);
 
-	return res;
+	iso_send(s);
 }
 
-/* Marshall/demarshall an CJrq structure (ASN.1 PER) */
-BOOL mcs_io_cjrq(STREAM s, MCS_CJRQ *cjrq)
+/* Receive an MCS transport data packet */
+STREAM mcs_recv()
 {
-	uint8 opcode = (14) << 2;
-	uint8 pkt_opcode = opcode;
-	BOOL res;
+	uint8 opcode, appid, length;
+	STREAM s;
+
+	s = iso_recv();
+	if (s == NULL)
+		return NULL;
 
-	res = prs_io_uint8(s, &pkt_opcode);
-	if (pkt_opcode != opcode)
+	in_uint8(s, opcode);
+	appid = opcode >> 2;
+	if (appid != MCS_SDIN)
 	{
-		ERROR("Expected CJrq, received %x\n", pkt_opcode);
-		return False;
+		if (appid != MCS_DPUM)
+		{
+			ERROR("expected data, got %d\n", opcode);
+		}
+		return NULL;
 	}
 
-	res = res ? msb_io_uint16(s, &cjrq->userid) : False;
-	res = res ? msb_io_uint16(s, &cjrq->chanid) : False;
+	in_uint8s(s, 5); /* userid, chanid, flags */
+	in_uint8(s, length);
+	if (length & 0x80)
+		in_uint8s(s, 1); /* second byte of length */
 
-	return res;
+	return s;
 }
 
-/* Marshall/demarshall an CJcf structure (ASN.1 PER) */
-BOOL mcs_io_cjcf(STREAM s, MCS_CJCF *cjcf)
+/* Establish a connection up to the MCS layer */
+BOOL mcs_connect(char *server, STREAM mcs_data)
 {
-	uint8 opcode = (15) << 2;
-	uint8 pkt_opcode = opcode | 2;
-	BOOL res;
-
-	res = prs_io_uint8(s, &pkt_opcode);
-	if ((pkt_opcode & 0xfc) != opcode)
-	{
-		ERROR("Expected CJcf, received %x\n", pkt_opcode);
+	if (!iso_connect(server))
 		return False;
-	}
 
-	res = res ? prs_io_uint8 (s, &cjcf->result) : False;
-	res = res ? msb_io_uint16(s, &cjcf->userid) : False;
-	res = res ? msb_io_uint16(s, &cjcf->req_chanid) : False;
-	if (pkt_opcode & 2)
-		res = res ? msb_io_uint16(s, &cjcf->join_chanid) : False;
+	mcs_send_connect_initial(mcs_data);
+	if (!mcs_recv_connect_response(mcs_data))
+		goto error;
 
-	return res;
-}
+	mcs_send_edrq();
 
-/* Marshall/demarshall an SDrq or SDin packet (ASN.1 PER) */
-BOOL mcs_io_data(STREAM s, MCS_DATA *dt, BOOL request)
-{
-	uint8 opcode = (request ? 25 : 26) << 2;
-	uint8 pkt_opcode = opcode;
-	uint8 byte1, byte2;
-	BOOL res;
+	mcs_send_aurq();
+	if (!mcs_recv_aucf(&mcs_userid))
+		goto error;
 
-	res = prs_io_uint8(s, &pkt_opcode);
-	if (pkt_opcode != opcode)
-	{
-		ERROR("Expected MCS data, received %x\n", pkt_opcode);
-		return False;
-	}
+	mcs_send_cjrq(mcs_userid + 1001);
+	if (!mcs_recv_cjcf())
+		goto error;
 
-	res = res ? msb_io_uint16(s, &dt->userid) : False;
-	res = res ? msb_io_uint16(s, &dt->chanid) : False;
-	res = res ? prs_io_uint8 (s, &dt->flags ) : False;
+	mcs_send_cjrq(MCS_GLOBAL_CHANNEL);
+	if (!mcs_recv_cjcf())
+		goto error;
 
-	if (s->marshall)
-	{
-		dt->length |= 0x8000;
-		res = res ? msb_io_uint16(s, &dt->length) : False;
-	}
-	else
-	{
-		res = res ? prs_io_uint8(s, &byte1) : False;
-		if (byte1 & 0x80)
-		{
-			res = res ? prs_io_uint8(s, &byte2) : False;
-			dt->length = ((byte1 & ~0x80) << 8) + byte2;
-		}
-		else dt->length = byte1;
-	}
+	return True;
 
-	return res;
+ error:
+	iso_disconnect();
+	return False;
 }
 
+/* Disconnect from the MCS layer */
+void mcs_disconnect()
+{
+	iso_disconnect();
+}