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