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

   1 /*
   2  * Sequence number / nonce mechanism for udp tunnel
   3  *
   4  * arguments: none
   5  *
   6  * encoding: prepend 4 bytes of sequence arithmetic serial number
   7  * decoding: check increasingness, or ignore
   8  */
   9 /*
  10  * Copyright (C) 2000 Ian Jackson
  11  *
  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.
  16  *
  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.
  21  *
  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.
  25  */
  26
  27 #include <netinet/in.h>
  28
  29 #include "forwarder.h"
  30
  31 struct mechdata {
  32   uint32_t number;
  33   int anyseen; /* decode only */
  34 };
  35
  36 static void mes_sequence(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) {
  37   struct mechdata *md;
  38
  39   XMALLOC(md);
  40   get_random(&md->number,sizeof(md->number));
  41   *maxprefix_io += 4;
  42   *md_r= md;
  43 }
  44
  45 static void mds_sequence(struct mechdata **md_r) {
  46   struct mechdata *md;
  47   XMALLOC(md);
  48   md->anyseen= 0;
  49   *md_r= md;
  50 }
  51
  52 static void menc_sequence(struct mechdata *md, struct buffer *buf) {
  53   md->number++;
  54   *(uint32_t*)buf_prepend(buf,4)= htonl(md->number);
  55 }
  56
  57 static const char *mdec_check(struct mechdata *md, struct buffer *buf) {
  58   uint32_t *sp, sequence;
  59
  60   BUF_UNPREPEND(sp,buf,4);
  61   sequence= ntohl(*sp);
  62
  63   if (md->anyseen)
  64     if (sequence - md->number >= 0x800000UL) return "out of order packet";
  65
  66   md->number= sequence;
  67   md->anyseen= 1;
  68
  69   return 0;
  70 }
  71
  72 static const char *mdec_skip(struct mechdata *md, struct buffer *buf) {
  73   uint32_t *sp;
  74   BUF_UNPREPEND(sp,buf,4);
  75   return 0;
  76 }
  77
  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   },
  81  { 0 }
  82 };