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 Ian Jackson
  13  *
  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.
  18  *
  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.
  23  *
  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.
  27  */
  28
  29 #include <netinet/in.h>
  30
  31 #include "forwarder.h"
  32
  33 struct mechdata {
  34   uint32_t number;
  35   int anyseen; /* decode only */
  36 };
  37
  38 static void mes_sequence(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) {
  39   struct mechdata *md;
  40
  41   XMALLOC(md);
  42   get_random(&md->number,sizeof(md->number));
  43   *maxprefix_io += 4;
  44   *md_r= md;
  45 }
  46
  47 static void mds_sequence(struct mechdata **md_r) {
  48   struct mechdata *md;
  49   XMALLOC(md);
  50   md->anyseen= 0;
  51   *md_r= md;
  52 }
  53
  54 static void menc_sequence(struct mechdata *md, struct buffer *buf) {
  55   md->number++;
  56   *(uint32_t*)buf_prepend(buf,4)= htonl(md->number);
  57 }
  58
  59 static const char *mdec_check(struct mechdata *md, struct buffer *buf) {
  60   uint32_t *sp, sequence;
  61
  62   BUF_UNPREPEND(sp,buf,4);
  63   sequence= ntohl(*sp);
  64
  65   if (md->anyseen)
  66     if (sequence - md->number >= 0x800000UL) return "out of order packet";
  67
  68   md->number= sequence;
  69   md->anyseen= 1;
  70
  71   return 0;
  72 }
  73
  74 static const char *mdec_skip(struct mechdata *md, struct buffer *buf) {
  75   uint32_t *sp;
  76   BUF_UNPREPEND(sp,buf,4);
  77   return 0;
  78 }
  79
  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   },
  83  { 0 }
  84 };