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

   1 /*
   2  * Sequence number / nonce mechanism
   3  *
   4  * arguments: none
   5  *
   6  * encoding: prepend 4 bytes of sequence arithmetic serial number
   7  * decoding: check increasingness, or ignore
   8  */
   9
  10 #include <netinet/in.h>
  11
  12 #include "forwarder.h"
  13
  14 struct mechdata {
  15   uint32_t number;
  16   int anyseen; /* decode only */
  17 };
  18
  19 static void mes_sequence(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) {
  20   struct mechdata *md;
  21
  22   XMALLOC(md);
  23   get_random(&md->number,sizeof(md->number));
  24   *maxprefix_io += 4;
  25   *md_r= md;
  26 }
  27
  28 static void mds_sequence(struct mechdata **md_r) {
  29   struct mechdata *md;
  30   XMALLOC(md);
  31   md->anyseen= 0;
  32   *md_r= md;
  33 }
  34
  35 static void menc_sequence(struct mechdata *md, struct buffer *buf) {
  36   md->number++;
  37   *(uint32_t*)buf_prepend(buf,4)= htonl(md->number);
  38 }
  39
  40 static const char *mdec_check(struct mechdata *md, struct buffer *buf) {
  41   uint32_t *sp, sequence;
  42
  43   BUF_UNPREPEND(sp,buf,4);
  44   sequence= ntohl(*sp);
  45
  46   if (md->anyseen)
  47     if (sequence - md->number >= 0x800000UL) return "out of order packet";
  48
  49   md->number= sequence;
  50   md->anyseen= 1;
  51
  52   return 0;
  53 }
  54
  55 static const char *mdec_skip(struct mechdata *md, struct buffer *buf) {
  56   uint32_t *sp;
  57   BUF_UNPREPEND(sp,buf,4);
  58   return 0;
  59 }
  60
  61 const struct mechanism mechlist_sequence[]= {
  62  { "nonce",         mes_sequence, mds_sequence,  menc_sequence, mdec_skip    },
  63  { "sequence",      mes_sequence, mds_sequence,  menc_sequence, mdec_check   },
  64  { 0 }
  65 };