2 * Sequence number / nonce mechanism for udp tunnel
6 * encoding: prepend 4 bytes of sequence arithmetic serial number
7 * decoding: check increasingness, or ignore
10 * Copyright (C) 2000 Ian Jackson
12 * This is free software; you can redistribute it and/or modify it
13 * under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; either version 2 of the License, or
15 * (at your option) any later version.
17 * This program is distributed in the hope that it will be useful, but
18 * WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 * General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with userv-utils; if not, write to the Free Software
24 * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
27 #include <netinet/in.h>
29 #include "forwarder.h"
33 int anyseen; /* decode only */
36 static void mes_sequence(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) {
40 get_random(&md->number,sizeof(md->number));
45 static void mds_sequence(struct mechdata **md_r) {
52 static void menc_sequence(struct mechdata *md, struct buffer *buf) {
54 *(uint32_t*)buf_prepend(buf,4)= htonl(md->number);
57 static const char *mdec_check(struct mechdata *md, struct buffer *buf) {
58 uint32_t *sp, sequence;
60 BUF_UNPREPEND(sp,buf,4);
64 if (sequence - md->number >= 0x800000UL) return "out of order packet";
72 static const char *mdec_skip(struct mechdata *md, struct buffer *buf) {
74 BUF_UNPREPEND(sp,buf,4);
78 const struct mechanism mechlist_sequence[]= {
79 { "nonce", mes_sequence, mds_sequence, menc_sequence, mdec_skip },
80 { "sequence", mes_sequence, mds_sequence, menc_sequence, mdec_check },