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/*
* Sequence number / nonce mechanism for udp tunnel
*
* mechanisms: nonce, sequence
* arguments: none
*
* restrictions: none
* encoding: prepend 4 bytes of sequence arithmetic serial number
* decoding: check increasingness (sequence), or ignore (nonce)
*/
/*
* This file is part of ipif, part of userv-utils
*
* Copyright 1996-2013 Ian Jackson <ijackson@chiark.greenend.org.uk>
* Copyright 1998 David Damerell <damerell@chiark.greenend.org.uk>
* Copyright 1999,2003
* Chancellor Masters and Scholars of the University of Cambridge
* Copyright 2010 Tony Finch <fanf@dotat.at>
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with userv-utils; if not, see http://www.gnu.org/licenses/.
*/
#include <netinet/in.h>
#include "forwarder.h"
struct mechdata {
uint32_t number;
int anyseen; /* decode only */
};
static void mes_sequence(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) {
struct mechdata *md;
XMALLOC(md);
get_random(&md->number,sizeof(md->number));
*maxprefix_io += 4;
*md_r= md;
}
static void mds_sequence(struct mechdata **md_r) {
struct mechdata *md;
XMALLOC(md);
md->anyseen= 0;
*md_r= md;
}
static void menc_sequence(struct mechdata *md, struct buffer *buf) {
md->number++;
*(uint32_t*)buf_prepend(buf,4)= htonl(md->number);
}
static const char *mdec_check(struct mechdata *md, struct buffer *buf) {
uint32_t *sp, sequence;
BUF_UNPREPEND(sp,buf,4);
sequence= ntohl(*sp);
if (md->anyseen)
if (sequence - md->number >= 0x800000UL) return "out of order packet";
md->number= sequence;
md->anyseen= 1;
return 0;
}
static const char *mdec_skip(struct mechdata *md, struct buffer *buf) {
uint32_t *sp;
BUF_UNPREPEND(sp,buf,4);
return 0;
}
const struct mechanism mechlist_sequence[]= {
{ "nonce", mes_sequence, mds_sequence, menc_sequence, mdec_skip },
{ "sequence", mes_sequence, mds_sequence, menc_sequence, mdec_check },
{ 0 }
};
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