L2TP support (from KAME)

1 files changed, 712 insertions, 0 deletions

diff --git a/usr.sbin/tcpdump/print-l2tp.c b/usr.sbin/tcpdump/print-l2tp.c
new file mode 100644
index 00000000000..d5d1bde2f3b
--- /dev/null
+++ b/usr.sbin/tcpdump/print-l2tp.c
@@ -0,0 +1,712 @@
+/*	$OpenBSD: print-l2tp.c,v 1.1 2000/01/16 10:54:58 jakob Exp $	*/
+
+/*
+ * Copyright (c) 1991, 1993, 1994, 1995, 1996, 1997
+ *      The Regents of the University of California.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that: (1) source code distributions
+ * retain the above copyright notice and this paragraph in its entirety, (2)
+ * distributions including binary code include the above copyright notice and
+ * this paragraph in its entirety in the documentation or other materials
+ * provided with the distribution, and (3) all advertising materials mentioning
+ * features or use of this software display the following acknowledgement:
+ * ``This product includes software developed by the University of California,
+ * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
+ * the University nor the names of its contributors may be used to endorse
+ * or promote products derived from this software without specific prior
+ * written permission.
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * L2TP support contributed by Motonori Shindo (mshindo@ascend.co.jp)
+ */
+
+#ifndef lint
+static const char rcsid[] =
+    "@(#) $Header: /cvs/OpenBSD/src/usr.sbin/tcpdump/print-l2tp.c,v 1.1 2000/01/16 10:54:58 jakob Exp $";
+#endif
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <stdio.h>
+
+#include "l2tp.h"
+#include "interface.h"
+
+static char tstr[] = " [|l2tp]";
+
+#ifndef TRUE
+#define TRUE 1
+#endif
+
+#ifndef FALSE
+#define FALSE 0
+#endif
+
+static u_char *l2tp_message_type_string[] = {
+	"RESERVED_0",		/* 0  Reserved */
+	"SCCRQ",		/* 1  Start-Control-Connection-Request */
+	"SCCRP",		/* 2  Start-Control-Connection-Reply */
+	"SCCCN",		/* 3  Start-Control-Connection-Connected */
+	"StopCCN",		/* 4  Stop-Control-Connection-Notification */
+	"RESERVED_5",		/* 5  Reserved */
+	"HELLO",		/* 6  Hello */
+	"OCRQ",			/* 7  Outgoing-Call-Request */
+	"OCRP",			/* 8  Outgoing-Call-Reply */
+	"OCCN",			/* 9  Outgoing-Call-Connected */
+	"ICRQ",			/* 10 Incoming-Call-Request */
+	"ICRP",			/* 11 Incoming-Call-Reply */
+	"ICCN",			/* 12 Incoming-Call-Connected */
+	"RESERVED_13",		/* 13 Reserved */
+	"CDN",			/* 14 Call-Disconnect-Notify */
+	"WEN",			/* 15 WAN-Error-Notify */
+	"SLI"			/* 16 Set-Link-Info */
+#define L2TP_MAX_MSGTYPE_INDEX	17
+};
+
+static void l2tp_msgtype_print(const u_char *dat, u_int length);
+static void l2tp_result_code_print(const u_char *dat, u_int length);
+static void l2tp_proto_ver_print(const u_char *dat, u_int length);
+static void l2tp_framing_cap_print(const u_char *dat, u_int length);
+static void l2tp_bearer_cap_print(const u_char *dat, u_int length);
+static void l2tp_tie_breaker_print(const u_char *dat, u_int length);
+static void l2tp_firm_ver_print(const u_char *dat, u_int length);
+static void l2tp_host_name_print(const u_char *dat, u_int length);
+static void l2tp_vendor_name_print(const u_char *dat, u_int length);
+static void l2tp_assnd_tun_id_print(const u_char *dat, u_int length);
+static void l2tp_recv_win_size_print(const u_char *dat, u_int length);
+static void l2tp_challenge_print(const u_char *dat, u_int length);
+static void l2tp_q931_cc_print(const u_char *dat, u_int length);
+static void l2tp_challenge_resp_print(const u_char *dat, u_int length);
+static void l2tp_assnd_sess_id_print(const u_char *dat, u_int length);
+static void l2tp_call_ser_num_print(const u_char *dat, u_int length);
+static void l2tp_minimum_bps_print(const u_char *dat, u_int length);
+static void l2tp_maximum_bps_print(const u_char *dat, u_int length);
+static void l2tp_bearer_type_print(const u_char *dat, u_int length);
+static void l2tp_framing_type_print(const u_char *dat, u_int length);
+static void l2tp_packet_proc_delay_print(const u_char *dat, u_int length);
+static void l2tp_called_number_print(const u_char *dat, u_int length);
+static void l2tp_calling_number_print(const u_char *dat, u_int length);
+static void l2tp_sub_address_print(const u_char *dat, u_int length);
+static void l2tp_tx_conn_speed_print(const u_char *dat, u_int length);
+static void l2tp_phy_channel_id_print(const u_char *dat, u_int length);
+static void l2tp_ini_recv_lcp_print(const u_char *dat, u_int length);
+static void l2tp_last_sent_lcp_print(const u_char *dat, u_int length);
+static void l2tp_last_recv_lcp_print(const u_char *dat, u_int length);
+static void l2tp_proxy_auth_type_print(const u_char *dat, u_int length);
+static void l2tp_proxy_auth_name_print(const u_char *dat, u_int length);
+static void l2tp_proxy_auth_chal_print(const u_char *dat, u_int length);
+static void l2tp_proxy_auth_id_print(const u_char *dat, u_int length);
+static void l2tp_proxy_auth_resp_print(const u_char *dat, u_int length);
+static void l2tp_call_errors_print(const u_char *dat, u_int length);
+static void l2tp_accm_print(const u_char *dat, u_int length);
+static void l2tp_random_vector_print(const u_char *dat, u_int length);
+static void l2tp_private_grp_id_print(const u_char *dat, u_int length);
+static void l2tp_rx_conn_speed_print(const u_char *dat, u_int length);
+static void l2tp_seq_required_print(const u_char *dat, u_int length);
+static void l2tp_avp_print(const u_char *dat, u_int length);
+
+static struct l2tp_avp_vec l2tp_avp[] = {
+  {"MSGTYPE", l2tp_msgtype_print}, 		/* 0  Message Type */
+  {"RESULT_CODE", l2tp_result_code_print},	/* 1  Result Code */
+  {"PROTO_VER", l2tp_proto_ver_print},		/* 2  Protocol Version */
+  {"FRAMING_CAP", l2tp_framing_cap_print},	/* 3  Framing Capabilities */
+  {"BEARER_CAP", l2tp_bearer_cap_print},	/* 4  Bearer Capabilities */
+  {"TIE_BREAKER", l2tp_tie_breaker_print},	/* 5  Tie Breaker */
+  {"FIRM_VER", l2tp_firm_ver_print},		/* 6  Firmware Revision */
+  {"HOST_NAME", l2tp_host_name_print},		/* 7  Host Name */
+  {"VENDOR_NAME", l2tp_vendor_name_print},	/* 8  Vendor Name */
+  {"ASSND_TUN_ID", l2tp_assnd_tun_id_print}, 	/* 9  Assigned Tunnel ID */
+  {"RECV_WIN_SIZE", l2tp_recv_win_size_print},	/* 10 Receive Window Size */
+  {"CHALLENGE", l2tp_challenge_print},		/* 11 Challenge */
+  {"Q931_CC", l2tp_q931_cc_print},		/* 12 Q.931 Cause Code */
+  {"CHALLENGE_RESP", l2tp_challenge_resp_print},/* 13 Challenge Response */
+  {"ASSND_SESS_ID", l2tp_assnd_sess_id_print},  /* 14 Assigned Session ID */
+  {"CALL_SER_NUM", l2tp_call_ser_num_print}, 	/* 15 Call Serial Number */
+  {"MINIMUM_BPS",	l2tp_minimum_bps_print},/* 16 Minimum BPS */
+  {"MAXIMUM_BPS", l2tp_maximum_bps_print},	/* 17 Maximum BPS */
+  {"BEARER_TYPE",	l2tp_bearer_type_print},/* 18 Bearer Type */
+  {"FRAMING_TYPE", l2tp_framing_type_print}, 	/* 19 Framing Type */
+  {"PACKET_PROC_DELAY", l2tp_packet_proc_delay_print}, /* 20 Packet Processing Delay (OBSOLETE) */
+  {"CALLED_NUMBER", l2tp_called_number_print},	/* 21 Called Number */
+  {"CALLING_NUMBER", l2tp_calling_number_print},/* 22 Calling Number */
+  {"SUB_ADDRESS",	l2tp_sub_address_print},/* 23 Sub-Address */
+  {"TX_CONN_SPEED", l2tp_tx_conn_speed_print},	/* 24 (Tx) Connect Speed */
+  {"PHY_CHANNEL_ID", l2tp_phy_channel_id_print},/* 25 Physical Channel ID */
+  {"INI_RECV_LCP", l2tp_ini_recv_lcp_print}, 	/* 26 Initial Received LCP CONFREQ */
+  {"LAST_SENT_LCP", l2tp_last_sent_lcp_print},	/* 27 Last Sent LCP CONFREQ */
+  {"LAST_RECV_LCP", l2tp_last_recv_lcp_print},	/* 28 Last Received LCP CONFREQ */
+  {"PROXY_AUTH_TYPE", l2tp_proxy_auth_type_print},/* 29 Proxy Authen Type */
+  {"PROXY_AUTH_NAME", l2tp_proxy_auth_name_print},/* 30 Proxy Authen Name */
+  {"PROXY_AUTH_CHAL", l2tp_proxy_auth_chal_print},/* 31 Proxy Authen Challenge */
+  {"PROXY_AUTH_ID", l2tp_proxy_auth_id_print},	/* 32 Proxy Authen ID */
+  {"PROXY_AUTH_RESP", l2tp_proxy_auth_resp_print},/* 33 Proxy Authen Response */
+  {"CALL_ERRORS", l2tp_call_errors_print},	/* 34 Call Errors */
+  {"ACCM", l2tp_accm_print},			/* 35 ACCM */
+  {"RANDOM_VECTOR", l2tp_random_vector_print},	/* 36 Random Vector */
+  {"PRIVATE_GRP_ID", l2tp_private_grp_id_print},/* 37 Private Group ID */
+  {"RX_CONN_SPEED", l2tp_rx_conn_speed_print},	/* 38 (Rx) Connect Speed */
+  {"SEQ_REQUIRED", l2tp_seq_required_print}, 	/* 39 Sequencing Required */
+#define L2TP_MAX_AVP_INDEX	40
+};
+
+#if 0
+static char *l2tp_result_code_StopCCN[] = {
+         "Reserved",
+         "General request to clear control connection",
+         "General error--Error Code indicates the problem",
+         "Control channel already exists",
+         "Requester is not authorized to establish a control channel",
+         "The protocol version of the requester is not supported",
+         "Requester is being shut down",
+         "Finite State Machine error"
+#define L2TP_MAX_RESULT_CODE_STOPCC_INDEX	8
+};
+#endif
+
+#if 0
+static char *l2tp_result_code_CDN[] = {
+	"Reserved",
+	"Call disconnected due to loss of carrier",
+	"Call disconnected for the reason indicated in error code",
+	"Call disconnected for administrative reasons",
+	"Call failed due to lack of appropriate facilities being " \
+	"available (temporary condition)",
+	"Call failed due to lack of appropriate facilities being " \
+	"available (permanent condition)",
+	"Invalid destination",
+	"Call failed due to no carrier detected",
+	"Call failed due to detection of a busy signal",
+	"Call failed due to lack of a dial tone",
+	"Call was not established within time allotted by LAC",
+	"Call was connected but no appropriate framing was detected"
+#define L2TP_MAX_RESULT_CODE_CDN_INDEX	12
+};
+#endif
+
+#if 0
+static char *l2tp_error_code_general[] = {
+	"No general error",
+	"No control connection exists yet for this LAC-LNS pair",
+	"Length is wrong",
+	"One of the field values was out of range or " \
+	"reserved field was non-zero"
+	"Insufficient resources to handle this operation now",
+	"The Session ID is invalid in this context",
+	"A generic vendor-specific error occurred in the LAC",
+	"Try another"
+#define L2TP_MAX_ERROR_CODE_GENERAL_INDEX	8
+};
+#endif
+
+/******************************/
+/* generic print out routines */
+/******************************/
+static void 
+print_string(const u_char *dat, u_int length)
+{
+	int i;
+	for (i=0; i<length; i++) {
+		printf("%c", *dat++);
+	}
+}
+
+static void 
+print_octets(const u_char *dat, u_int length)
+{
+	int i;
+	for (i=0; i<length; i++) {
+		printf("%02x", *dat++);
+	}
+}
+
+static void
+print_short(const u_short *dat)
+{
+	printf("%u", ntohs(*dat));
+}
+
+static void
+print_int(const u_int *dat)
+{
+	printf("%lu", (u_long)ntohl(*dat));
+}
+
+/**********************************/
+/* AVP-specific print out routines*/
+/**********************************/
+static void
+l2tp_msgtype_print(const u_char *dat, u_int length)
+{
+	u_short *ptr = (u_short *)dat;
+
+	if (ntohs(*ptr) < L2TP_MAX_MSGTYPE_INDEX) {
+		printf("%s", l2tp_message_type_string[ntohs(*ptr)]);
+	}
+}
+
+static void
+l2tp_result_code_print(const u_char *dat, u_int length)
+{
+	/* we just print out the result and error code number */
+	u_short *ptr = (u_short *)dat;
+	
+	if (length == 2) {		/* result code */
+		printf("%d", ntohs(*ptr));	
+	} else if (length == 4) { 	/* result & error code */
+		printf("%d/%d", ntohs(*ptr), ntohs(*(ptr+1)));
+	} else if (length > 4) {	/* result & error code & msg */
+		printf("%u/%u ", ntohs(*ptr), ntohs(*(ptr+1)));
+		print_string((u_char *)(ptr+2), length - 4);
+	}
+}
+
+static void
+l2tp_proto_ver_print(const u_char *dat, u_int length)
+{
+	printf("%d.%d", *dat, *(dat+1));
+}
+
+
+static void
+l2tp_framing_cap_print(const u_char *dat, u_int length)
+{
+	u_int *ptr = (u_int *)dat;
+
+	if (ntohl(*ptr) &  L2TP_FRAMING_CAP_ASYNC_MASK) {
+		printf("A");
+	}
+	if (ntohl(*ptr) &  L2TP_FRAMING_CAP_SYNC_MASK) {
+		printf("S");
+	}
+}
+
+static void
+l2tp_bearer_cap_print(const u_char *dat, u_int length)
+{
+	u_int *ptr = (u_int *)dat;
+
+	if (ntohl(*ptr) &  L2TP_BEARER_CAP_ANALOG_MASK) {
+		printf("A");
+	}
+	if (ntohl(*ptr) &  L2TP_BEARER_CAP_DIGITAL_MASK) {
+		printf("D");
+	}
+}
+
+static void
+l2tp_tie_breaker_print(const u_char *dat, u_int length)
+{
+	printf("%lx", *(u_long *)dat);	/* XXX */
+}
+
+static void
+l2tp_firm_ver_print(const u_char *dat, u_int length)
+{
+	print_short((u_short *)dat);
+}
+
+static void
+l2tp_host_name_print(const u_char *dat, u_int length)
+{
+	print_string(dat, length);
+}
+
+static void
+l2tp_vendor_name_print(const u_char *dat, u_int length)
+{
+	print_string(dat, length);
+}
+
+static void
+l2tp_assnd_tun_id_print(const u_char *dat, u_int length)
+{
+	print_short((u_short *)dat);
+}
+
+static void
+l2tp_recv_win_size_print(const u_char *dat, u_int length)
+{
+	print_short((u_short *)dat); 
+}
+
+static void
+l2tp_challenge_print(const u_char *dat, u_int length)
+{
+	print_octets(dat, length);
+}
+
+static void
+l2tp_q931_cc_print(const u_char *dat, u_int length)
+{
+	print_short((u_short *)dat);
+	print_short((u_short *)(dat + 2));
+	if (length > 3) {
+		printf(" ");
+		print_string(dat+3, length-3);
+	} 
+}
+
+static void
+l2tp_challenge_resp_print(const u_char *dat, u_int length)
+{
+	print_octets(dat, 16);		/* XXX length should be 16? */
+}
+
+static void
+l2tp_assnd_sess_id_print(const u_char *dat, u_int length)
+{
+	print_short((u_short *)dat);
+}
+
+static void
+l2tp_call_ser_num_print(const u_char *dat, u_int length)
+{
+	print_int((u_int *)dat);
+}
+
+static void
+l2tp_minimum_bps_print(const u_char *dat, u_int length)
+{
+	print_int((u_int *)dat);
+}
+
+static void
+l2tp_maximum_bps_print(const u_char *dat, u_int length)
+{
+	print_int((u_int *)dat);
+}
+
+static void
+l2tp_bearer_type_print(const u_char *dat, u_int length)
+{
+	u_int *ptr = (u_int *)dat;
+
+	if (ntohl(*ptr) &  L2TP_BEARER_TYPE_ANALOG_MASK) {
+		printf("A");
+	}
+	if (ntohl(*ptr) &  L2TP_BEARER_TYPE_DIGITAL_MASK) {
+		printf("D");
+	}
+}
+
+static void
+l2tp_framing_type_print(const u_char *dat, u_int length)
+{
+	u_int *ptr = (u_int *)dat;
+
+	if (ntohl(*ptr) &  L2TP_FRAMING_TYPE_ASYNC_MASK) {
+		printf("A");
+	}
+	if (ntohl(*ptr) &  L2TP_FRAMING_TYPE_SYNC_MASK) {
+		printf("S");
+	}
+}
+
+static void
+l2tp_packet_proc_delay_print(const u_char *dat, u_int length)
+{
+	printf("obsolete");
+}
+
+static void
+l2tp_called_number_print(const u_char *dat, u_int length)
+{
+	print_string(dat, length);
+}
+
+static void
+l2tp_calling_number_print(const u_char *dat, u_int length)
+{
+	print_string(dat, length);
+}
+
+static void
+l2tp_sub_address_print(const u_char *dat, u_int length)
+{
+	print_string(dat, length);
+}
+
+static void
+l2tp_tx_conn_speed_print(const u_char *dat, u_int length)
+{
+	print_int((u_int *)dat);
+}
+
+static void
+l2tp_phy_channel_id_print(const u_char *dat, u_int length)
+{
+	print_int((u_int *)dat);
+}
+
+static void
+l2tp_ini_recv_lcp_print(const u_char *dat, u_int length)
+{
+	print_octets(dat, length);
+}
+
+static void
+l2tp_last_sent_lcp_print(const u_char *dat, u_int length)
+{
+	print_octets(dat, length);
+}
+
+static void
+l2tp_last_recv_lcp_print(const u_char *dat, u_int length)
+{
+	print_octets(dat, length);
+}
+
+static void
+l2tp_proxy_auth_type_print(const u_char *dat, u_int length)
+{
+	u_short *ptr = (u_short *)dat;
+
+	switch (ntohs(*ptr)) {
+	case L2TP_AUTHEN_TYPE_RESERVED:
+		printf("Reserved");
+		break;
+	case L2TP_AUTHEN_TYPE_TEXTUAL:
+		printf("Textual");
+		break;
+	case L2TP_AUTHEN_TYPE_CHAP:
+		printf("CHAP");
+		break;
+	case L2TP_AUTHEN_TYPE_PAP:
+		printf("PAP");
+		break;
+	case L2TP_AUTHEN_TYPE_NO_AUTH:
+		printf("No Auth");
+		break;
+	case L2TP_AUTHEN_TYPE_MSCHAP:
+		printf("MS-CHAP");
+		break;
+	default:
+		printf("unknown");
+	}
+}
+
+static void
+l2tp_proxy_auth_name_print(const u_char *dat, u_int length)
+{
+	print_octets(dat, length);
+}
+
+static void
+l2tp_proxy_auth_chal_print(const u_char *dat, u_int length)
+{
+	print_octets(dat, length);
+}
+
+static void
+l2tp_proxy_auth_id_print(const u_char *dat, u_int length)
+{
+	u_short *ptr = (u_short *)dat;
+
+	printf("%d", ntohs(*ptr) & L2TP_PROXY_AUTH_ID_MASK);
+}
+
+static void
+l2tp_proxy_auth_resp_print(const u_char *dat, u_int length)
+{
+	print_octets(dat, length);
+}
+
+static void
+l2tp_call_errors_print(const u_char *dat, u_int length)
+{
+	struct l2tp_call_errors *ptr = (struct l2tp_call_errors *)dat;
+
+	printf("CRCErr=%d FrameErr=%d HardOver=%d BufOver=%d ",
+	       ptr->crc_errs,
+	       ptr->framing_errs,
+	       ptr->hardware_overruns,
+	       ptr->buffer_overruns);
+	printf("Timeout=%d AlingErr=%d",
+	       ptr->timeout_errs,
+	       ptr->alignment_errs);
+}
+
+static void
+l2tp_accm_print(const u_char *dat, u_int length)
+{
+	struct l2tp_accm *ptr = (struct l2tp_accm *)dat;
+
+	printf("send=%x recv=%x", ptr->send_accm, ptr->recv_accm);
+}
+
+static void
+l2tp_random_vector_print(const u_char *dat, u_int length)
+{
+	print_octets(dat, length);
+}
+
+static void
+l2tp_private_grp_id_print(const u_char *dat, u_int length)
+{
+	print_string(dat, length);	
+	/* XXX print_octets is more appropriate?? */
+}
+
+static void
+l2tp_rx_conn_speed_print(const u_char *dat, u_int length)
+{
+	print_int((u_int *)dat);
+}
+
+static void
+l2tp_seq_required_print(const u_char *dat, u_int length)
+{
+	return;
+}
+
+static void
+l2tp_avp_print(const u_char *dat, u_int length)
+{
+	u_int len;
+	const u_short *ptr = (u_short *)dat;
+	int hidden = FALSE;
+
+	printf(" ");
+	if (length > 0 && (snapend - dat) >= 2) {
+		/* there must be at least two octets for the length
+		   to be decoded */
+		if ((len = (ntohs(*ptr) & L2TP_AVP_HDR_LEN_MASK)) <=
+		    (snapend - dat)) {
+			if (ntohs(*ptr) & L2TP_AVP_HDR_FLAG_MANDATORY) {
+				printf("*");
+			}
+			if (ntohs(*ptr) & L2TP_AVP_HDR_FLAG_HIDDEN) {
+				hidden = TRUE;
+				printf("?");
+			}
+		} else {
+			printf("|...");
+			return;
+		}
+		ptr++;
+
+		if (ntohs(*ptr)) {	/* IETF == 0 */
+			printf("vendor=%04x", ntohs(*ptr));
+		}
+		ptr++;
+
+		if (ntohs(*ptr) < L2TP_MAX_AVP_INDEX) {
+			printf("%s", l2tp_avp[ntohs(*ptr)].name);
+			printf("(");
+			if (!hidden) {
+				(l2tp_avp[ntohs(*ptr)].print)
+					((u_char *)ptr+2, len-6);
+			} else {
+				printf("???");
+			}
+			printf(")");
+		} else {
+			printf(" invalid AVP %u", ntohs(*ptr));
+		}
+
+		l2tp_avp_print(dat + len, length - len);
+	} else if (length == 0) {
+		return;
+	} else {
+		printf("|...");
+	}
+}
+
+
+void
+l2tp_print(const u_char *dat, u_int length)
+{
+	const u_short *ptr = (u_short *)dat;
+	u_int cnt = 0;			/* total octets consumed */
+	u_short pad;
+	int flag_t, flag_l, flag_s, flag_o, flag_p;
+	u_short l2tp_len;
+
+	flag_t = flag_l = flag_s = flag_o = flag_p = FALSE;
+
+	if (min(length, snapend - dat) - 6 < 0) { 
+		/* flag/ver, tunnel_id, session_id must be present for
+		   this packet to be properly decoded */
+		printf("%s", tstr);
+		return;
+	}
+
+	if ((ntohs(*ptr) & L2TP_VERSION_MASK) == L2TP_VERSION_L2TP) {
+		printf(" l2tp:");
+	} else if ((ntohs(*ptr) & L2TP_VERSION_MASK) == L2TP_VERSION_L2F) {
+		printf(" l2f:");
+		return;		/* nothing to do */
+	} else {
+		printf(" Unknown Version, neither L2F(1) nor L2TP(2)");
+		return;		/* nothing we can do */
+	}
+
+	printf("[");
+	if (ntohs(*ptr) & L2TP_FLAG_TYPE) {
+		flag_t = TRUE;
+		printf("T");
+	}
+	if (ntohs(*ptr) & L2TP_FLAG_LENGTH) {
+		flag_l = TRUE;
+		printf("L");
+	}
+	if (ntohs(*ptr) & L2TP_FLAG_SEQUENCE) {
+		flag_s = TRUE;
+		printf("S");
+	}
+	if (ntohs(*ptr) & L2TP_FLAG_OFFSET) {
+		flag_o = TRUE;
+		printf("O");
+	}
+	if (ntohs(*ptr) & L2TP_FLAG_PRIORITY) {
+		flag_p = TRUE;
+		printf("P");
+	}
+	printf("]");
+
+	ptr++;
+	cnt += 2;
+	
+	if (flag_l) {
+		l2tp_len = ntohs(*ptr++);	/* XXX need to consider 
+						   truncation ?? */
+		cnt += 2;
+	} else {
+		l2tp_len = 0;
+	}
+
+	printf("(%d/", ntohs(*ptr++));		/* Tunnel ID */
+	printf("%d)",  ntohs(*ptr++));		/* Session ID */
+	cnt += 4;
+
+	if (flag_s) {
+		printf("Ns=%d,", ntohs(*ptr++));
+		printf("Nr=%d",  ntohs(*ptr++));
+		cnt += 4;
+	}
+
+	if (flag_o) {
+		pad =  ntohs(*ptr++);
+		(u_char *)ptr += pad;
+		cnt += (2 + pad);
+	}
+
+	if (flag_t) {
+		if (length - cnt == 0) {
+			printf(" ZLB");
+		} else {
+			l2tp_avp_print((u_char *)ptr, length - cnt);
+		}
+	} else {
+#if 0
+		printf(" {");
+		ppp_hdlc_print((u_char *)ptr, length - cnt);
+		printf("}");
+#else
+		printf("[hdlc|]");
+#endif
+	}
+}