mdw@git.distorted.org.uk Git - userv-utils/blob - ipif/mech-sequence.c

   1 /*
   2  * Sequence number / nonce mechanism for udp tunnel
   3  *
   4  * mechanisms: nonce, sequence
   5  * arguments: none
   6  *
   7  * restrictions: none
   8  * encoding: prepend 4 bytes of sequence arithmetic serial number
   9  * decoding: check increasingness (sequence), or ignore (nonce)
  10  */
  11 /*
  12  * Copyright (C) 2000,2003 Ian Jackson
  13  * This file is part of ipif, part of userv-utils
  14  *
  15  * This is free software; you can redistribute it and/or modify it
  16  * under the terms of the GNU General Public License as published by
  17  * the Free Software Foundation; either version 2 of the License, or
  18  * (at your option) any later version.
  19  *
  20  * This program is distributed in the hope that it will be useful, but
  21  * WITHOUT ANY WARRANTY; without even the implied warranty of
  22  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  23  * General Public License for more details.
  24  *
  25  * You should have received a copy of the GNU General Public License
  26  * along with userv-utils; if not, write to the Free Software
  27  * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  28  */
  29
  30 #include <netinet/in.h>
  31
  32 #include "forwarder.h"
  33
  34 struct mechdata {
  35   uint32_t number;
  36   int anyseen; /* decode only */
  37 };
  38
  39 static void mes_sequence(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) {
  40   struct mechdata *md;
  41
  42   XMALLOC(md);
  43   get_random(&md->number,sizeof(md->number));
  44   *maxprefix_io += 4;
  45   *md_r= md;
  46 }
  47
  48 static void mds_sequence(struct mechdata **md_r) {
  49   struct mechdata *md;
  50   XMALLOC(md);
  51   md->anyseen= 0;
  52   *md_r= md;
  53 }
  54
  55 static void menc_sequence(struct mechdata *md, struct buffer *buf) {
  56   md->number++;
  57   *(uint32_t*)buf_prepend(buf,4)= htonl(md->number);
  58 }
  59
  60 static const char *mdec_check(struct mechdata *md, struct buffer *buf) {
  61   uint32_t *sp, sequence;
  62
  63   BUF_UNPREPEND(sp,buf,4);
  64   sequence= ntohl(*sp);
  65
  66   if (md->anyseen)
  67     if (sequence - md->number >= 0x800000UL) return "out of order packet";
  68
  69   md->number= sequence;
  70   md->anyseen= 1;
  71
  72   return 0;
  73 }
  74
  75 static const char *mdec_skip(struct mechdata *md, struct buffer *buf) {
  76   uint32_t *sp;
  77   BUF_UNPREPEND(sp,buf,4);
  78   return 0;
  79 }
  80
  81 const struct mechanism mechlist_sequence[]= {
  82  { "nonce",         mes_sequence, mds_sequence,  menc_sequence, mdec_skip    },
  83  { "sequence",      mes_sequence, mds_sequence,  menc_sequence, mdec_check   },
  84  { 0 }
  85 };