2000-06-20 11:41:48 +00:00
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/*
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* alias_pptp.c
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*
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* Copyright (c) 2000 Whistle Communications, Inc.
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* All rights reserved.
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*
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* Subject to the following obligations and disclaimer of warranty, use and
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* redistribution of this software, in source or object code forms, with or
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* without modifications are expressly permitted by Whistle Communications;
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* provided, however, that:
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* 1. Any and all reproductions of the source or object code must include the
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* copyright notice above and the following disclaimer of warranties; and
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* 2. No rights are granted, in any manner or form, to use Whistle
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* Communications, Inc. trademarks, including the mark "WHISTLE
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* COMMUNICATIONS" on advertising, endorsements, or otherwise except as
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* such appears in the above copyright notice or in the software.
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*
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* THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
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* TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
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* REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
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* INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
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* WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
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* REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
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* SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
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* IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
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* RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
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* WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
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* PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
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* OF SUCH DAMAGE.
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*
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* Author: Erik Salander <erik@whistle.com>
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*/
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2001-09-30 21:03:33 +00:00
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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2000-06-20 11:41:48 +00:00
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/*
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Alias_pptp.c performs special processing for PPTP sessions under TCP.
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Specifically, watch PPTP control messages and alias the Call ID or the
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Peer's Call ID in the appropriate messages. Note, PPTP requires
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"de-aliasing" of incoming packets, this is different than any other
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TCP applications that are currently (ie. FTP, IRC and RTSP) aliased.
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2000-08-09 11:25:44 +00:00
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For Call IDs encountered for the first time, a PPTP alias link is created.
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The PPTP alias link uses the Call ID in place of the original port number.
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2000-06-20 11:41:48 +00:00
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An alias Call ID is created.
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For this routine to work, the PPTP control messages must fit entirely
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into a single TCP packet. This is typically the case, but is not
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required by the spec.
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Unlike some of the other TCP applications that are aliased (ie. FTP,
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IRC and RTSP), the PPTP control messages that need to be aliased are
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guaranteed to remain the same length. The aliased Call ID is a fixed
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length field.
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Reference: RFC 2637
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Initial version: May, 2000 (eds)
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*/
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/* Includes */
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#include <sys/types.h>
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#include <netinet/in_systm.h>
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#include <netinet/in.h>
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#include <netinet/ip.h>
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#include <netinet/tcp.h>
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2001-03-25 12:05:10 +00:00
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#include <stdio.h>
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2000-06-20 11:41:48 +00:00
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#include "alias_local.h"
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/*
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* PPTP definitions
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*/
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struct grehdr /* Enhanced GRE header. */
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{
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2000-10-30 12:39:41 +00:00
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u_int16_t gh_flags; /* Flags. */
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u_int16_t gh_protocol; /* Protocol type. */
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u_int16_t gh_length; /* Payload length. */
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u_int16_t gh_call_id; /* Call ID. */
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2000-06-20 11:41:48 +00:00
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u_int32_t gh_seq_no; /* Sequence number (optional). */
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u_int32_t gh_ack_no; /* Acknowledgment number (optional). */
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};
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2000-10-30 12:39:41 +00:00
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typedef struct grehdr GreHdr;
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2000-06-20 11:41:48 +00:00
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/* The PPTP protocol ID used in the GRE 'proto' field. */
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#define PPTP_GRE_PROTO 0x880b
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/* Bits that must be set a certain way in all PPTP/GRE packets. */
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#define PPTP_INIT_VALUE ((0x2001 << 16) | PPTP_GRE_PROTO)
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#define PPTP_INIT_MASK 0xef7fffff
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#define PPTP_MAGIC 0x1a2b3c4d
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#define PPTP_CTRL_MSG_TYPE 1
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enum {
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PPTP_StartCtrlConnRequest = 1,
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PPTP_StartCtrlConnReply = 2,
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PPTP_StopCtrlConnRequest = 3,
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PPTP_StopCtrlConnReply = 4,
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PPTP_EchoRequest = 5,
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2000-08-09 11:25:44 +00:00
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PPTP_EchoReply = 6,
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2000-06-20 11:41:48 +00:00
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PPTP_OutCallRequest = 7,
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PPTP_OutCallReply = 8,
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PPTP_InCallRequest = 9,
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PPTP_InCallReply = 10,
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PPTP_InCallConn = 11,
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PPTP_CallClearRequest = 12,
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PPTP_CallDiscNotify = 13,
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PPTP_WanErrorNotify = 14,
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2000-10-30 12:39:41 +00:00
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PPTP_SetLinkInfo = 15
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2000-06-20 11:41:48 +00:00
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};
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/* Message structures */
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struct pptpMsgHead {
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u_int16_t length; /* total length */
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u_int16_t msgType; /* PPTP message type */
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u_int32_t magic; /* magic cookie */
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u_int16_t type; /* control message type */
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u_int16_t resv0; /* reserved */
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};
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typedef struct pptpMsgHead *PptpMsgHead;
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2000-10-30 12:39:41 +00:00
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struct pptpCodes {
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u_int8_t resCode; /* Result Code */
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u_int8_t errCode; /* Error Code */
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};
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typedef struct pptpCodes *PptpCode;
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2000-06-20 11:41:48 +00:00
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struct pptpCallIds {
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u_int16_t cid1; /* Call ID field #1 */
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u_int16_t cid2; /* Call ID field #2 */
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};
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typedef struct pptpCallIds *PptpCallId;
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static PptpCallId AliasVerifyPptp(struct ip *, u_int16_t *);
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void
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2004-01-17 10:52:21 +00:00
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AliasHandlePptpOut(struct libalias *la,
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struct ip *pip, /* IP packet to examine/patch */
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2000-06-20 11:41:48 +00:00
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struct alias_link *link) /* The PPTP control link */
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{
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2000-08-09 11:25:44 +00:00
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struct alias_link *pptp_link;
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2000-06-20 11:41:48 +00:00
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PptpCallId cptr;
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2000-10-30 12:39:41 +00:00
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PptpCode codes;
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2000-06-20 11:41:48 +00:00
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u_int16_t ctl_type; /* control message type */
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struct tcphdr *tc;
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/* Verify valid PPTP control message */
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if ((cptr = AliasVerifyPptp(pip, &ctl_type)) == NULL)
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return;
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/* Modify certain PPTP messages */
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2000-08-09 11:25:44 +00:00
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switch (ctl_type) {
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case PPTP_OutCallRequest:
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case PPTP_OutCallReply:
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case PPTP_InCallRequest:
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case PPTP_InCallReply:
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2000-10-30 12:39:41 +00:00
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/* Establish PPTP link for address and Call ID found in control message. */
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2004-01-17 10:52:21 +00:00
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pptp_link = AddPptp(la, GetOriginalAddress(link), GetDestAddress(link),
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2000-10-30 12:39:41 +00:00
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GetAliasAddress(link), cptr->cid1);
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break;
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2000-08-09 11:25:44 +00:00
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case PPTP_CallClearRequest:
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case PPTP_CallDiscNotify:
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2000-10-30 12:39:41 +00:00
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/* Find PPTP link for address and Call ID found in control message. */
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2004-01-17 10:52:21 +00:00
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pptp_link = FindPptpOutByCallId(la, GetOriginalAddress(link),
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2000-10-30 12:39:41 +00:00
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GetDestAddress(link),
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cptr->cid1);
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break;
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default:
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return;
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}
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2000-06-20 11:41:48 +00:00
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2000-08-09 11:25:44 +00:00
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if (pptp_link != NULL) {
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2000-08-07 09:51:04 +00:00
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int accumulate = cptr->cid1;
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2000-06-20 11:41:48 +00:00
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/* alias the Call Id */
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2000-08-09 11:25:44 +00:00
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cptr->cid1 = GetAliasPort(pptp_link);
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2000-06-20 11:41:48 +00:00
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/* Compute TCP checksum for revised packet */
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tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
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2000-08-07 09:51:04 +00:00
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accumulate -= cptr->cid1;
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ADJUST_CHECKSUM(accumulate, tc->th_sum);
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2000-10-30 12:39:41 +00:00
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switch (ctl_type) {
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case PPTP_OutCallReply:
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case PPTP_InCallReply:
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codes = (PptpCode)(cptr + 1);
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if (codes->resCode == 1) /* Connection established, */
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SetDestCallId(pptp_link, /* note the Peer's Call ID. */
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cptr->cid2);
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else
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SetExpire(pptp_link, 0); /* Connection refused. */
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break;
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case PPTP_CallDiscNotify: /* Connection closed. */
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SetExpire(pptp_link, 0);
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break;
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}
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2000-06-20 11:41:48 +00:00
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}
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}
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void
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2004-01-17 10:52:21 +00:00
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AliasHandlePptpIn(struct libalias *la,
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struct ip *pip, /* IP packet to examine/patch */
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2000-06-20 11:41:48 +00:00
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struct alias_link *link) /* The PPTP control link */
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{
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2000-08-09 11:25:44 +00:00
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struct alias_link *pptp_link;
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2000-06-20 11:41:48 +00:00
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PptpCallId cptr;
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u_int16_t *pcall_id;
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u_int16_t ctl_type; /* control message type */
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struct tcphdr *tc;
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/* Verify valid PPTP control message */
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if ((cptr = AliasVerifyPptp(pip, &ctl_type)) == NULL)
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return;
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/* Modify certain PPTP messages */
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switch (ctl_type)
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{
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case PPTP_InCallConn:
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case PPTP_WanErrorNotify:
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case PPTP_SetLinkInfo:
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pcall_id = &cptr->cid1;
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break;
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case PPTP_OutCallReply:
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case PPTP_InCallReply:
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pcall_id = &cptr->cid2;
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break;
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2000-10-30 12:39:41 +00:00
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case PPTP_CallDiscNotify: /* Connection closed. */
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2004-01-17 10:52:21 +00:00
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pptp_link = FindPptpInByCallId(la, GetDestAddress(link),
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2000-10-30 12:39:41 +00:00
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GetAliasAddress(link),
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cptr->cid1);
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if (pptp_link != NULL)
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SetExpire(pptp_link, 0);
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return;
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2000-06-20 11:41:48 +00:00
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default:
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return;
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}
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2000-08-09 11:25:44 +00:00
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/* Find PPTP link for address and Call ID found in PPTP Control Msg */
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2004-01-17 10:52:21 +00:00
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pptp_link = FindPptpInByPeerCallId(la, GetDestAddress(link),
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2000-10-30 12:39:41 +00:00
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GetAliasAddress(link),
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*pcall_id);
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2000-06-20 11:41:48 +00:00
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2000-08-09 11:25:44 +00:00
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if (pptp_link != NULL) {
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2000-08-07 09:51:04 +00:00
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int accumulate = *pcall_id;
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2000-10-30 12:39:41 +00:00
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/* De-alias the Peer's Call Id. */
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2000-08-09 11:25:44 +00:00
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*pcall_id = GetOriginalPort(pptp_link);
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2000-06-20 11:41:48 +00:00
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/* Compute TCP checksum for modified packet */
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tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
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2000-08-07 09:51:04 +00:00
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accumulate -= *pcall_id;
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ADJUST_CHECKSUM(accumulate, tc->th_sum);
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2000-10-30 12:39:41 +00:00
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if (ctl_type == PPTP_OutCallReply || ctl_type == PPTP_InCallReply) {
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PptpCode codes = (PptpCode)(cptr + 1);
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if (codes->resCode == 1) /* Connection established, */
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SetDestCallId(pptp_link, /* note the Call ID. */
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cptr->cid1);
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else
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SetExpire(pptp_link, 0); /* Connection refused. */
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}
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2000-06-20 11:41:48 +00:00
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}
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}
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2000-10-30 12:39:41 +00:00
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static PptpCallId
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2000-06-20 11:41:48 +00:00
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AliasVerifyPptp(struct ip *pip, u_int16_t *ptype) /* IP packet to examine/patch */
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{
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int hlen, tlen, dlen;
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PptpMsgHead hptr;
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struct tcphdr *tc;
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/* Calculate some lengths */
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tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
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hlen = (pip->ip_hl + tc->th_off) << 2;
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tlen = ntohs(pip->ip_len);
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dlen = tlen - hlen;
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/* Verify data length */
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if (dlen < (sizeof(struct pptpMsgHead) + sizeof(struct pptpCallIds)))
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return(NULL);
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/* Move up to PPTP message header */
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hptr = (PptpMsgHead)(((char *) pip) + hlen);
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/* Return the control message type */
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*ptype = ntohs(hptr->type);
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/* Verify PPTP Control Message */
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if ((ntohs(hptr->msgType) != PPTP_CTRL_MSG_TYPE) ||
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(ntohl(hptr->magic) != PPTP_MAGIC))
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return(NULL);
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2000-10-30 12:39:41 +00:00
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/* Verify data length. */
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if ((*ptype == PPTP_OutCallReply || *ptype == PPTP_InCallReply) &&
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(dlen < sizeof(struct pptpMsgHead) + sizeof(struct pptpCallIds) +
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sizeof(struct pptpCodes)))
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return (NULL);
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2000-06-20 11:41:48 +00:00
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else
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2000-10-30 12:39:41 +00:00
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return (PptpCallId)(hptr + 1);
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|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
int
|
2004-01-17 10:52:21 +00:00
|
|
|
AliasHandlePptpGreOut(struct libalias *la, struct ip *pip)
|
2000-10-30 12:39:41 +00:00
|
|
|
{
|
|
|
|
GreHdr *gr;
|
|
|
|
struct alias_link *link;
|
|
|
|
|
|
|
|
gr = (GreHdr *)((char *)pip + (pip->ip_hl << 2));
|
|
|
|
|
|
|
|
/* Check GRE header bits. */
|
|
|
|
if ((ntohl(*((u_int32_t *)gr)) & PPTP_INIT_MASK) != PPTP_INIT_VALUE)
|
|
|
|
return (-1);
|
|
|
|
|
2004-01-17 10:52:21 +00:00
|
|
|
link = FindPptpOutByPeerCallId(la, pip->ip_src, pip->ip_dst, gr->gh_call_id);
|
2000-10-30 12:39:41 +00:00
|
|
|
if (link != NULL) {
|
|
|
|
struct in_addr alias_addr = GetAliasAddress(link);
|
|
|
|
|
|
|
|
/* Change source IP address. */
|
|
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
|
|
(u_short *)&alias_addr,
|
|
|
|
(u_short *)&pip->ip_src,
|
|
|
|
2);
|
|
|
|
pip->ip_src = alias_addr;
|
|
|
|
}
|
|
|
|
|
|
|
|
return (0);
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
int
|
2004-01-17 10:52:21 +00:00
|
|
|
AliasHandlePptpGreIn(struct libalias *la, struct ip *pip)
|
2000-10-30 12:39:41 +00:00
|
|
|
{
|
|
|
|
GreHdr *gr;
|
|
|
|
struct alias_link *link;
|
|
|
|
|
|
|
|
gr = (GreHdr *)((char *)pip + (pip->ip_hl << 2));
|
|
|
|
|
|
|
|
/* Check GRE header bits. */
|
|
|
|
if ((ntohl(*((u_int32_t *)gr)) & PPTP_INIT_MASK) != PPTP_INIT_VALUE)
|
|
|
|
return (-1);
|
|
|
|
|
2004-01-17 10:52:21 +00:00
|
|
|
link = FindPptpInByPeerCallId(la, pip->ip_src, pip->ip_dst, gr->gh_call_id);
|
2000-10-30 12:39:41 +00:00
|
|
|
if (link != NULL) {
|
|
|
|
struct in_addr src_addr = GetOriginalAddress(link);
|
|
|
|
|
|
|
|
/* De-alias the Peer's Call Id. */
|
|
|
|
gr->gh_call_id = GetOriginalPort(link);
|
|
|
|
|
|
|
|
/* Restore original IP address. */
|
|
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
|
|
(u_short *)&src_addr,
|
|
|
|
(u_short *)&pip->ip_dst,
|
|
|
|
2);
|
|
|
|
pip->ip_dst = src_addr;
|
|
|
|
}
|
|
|
|
|
|
|
|
return (0);
|
2000-06-20 11:41:48 +00:00
|
|
|
}
|