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

   1 /*
   2  * Timestamp mechanism for udp tunnel
   3  *
   4  * mechanism: timestamp
   5  * arguments: <max-skew> <max-age>
   6  *
   7  * restrictions: none
   8  * encoding: prepend 4 bytes of UNIX time in network byte order
   9  *
  10  * <max-age> is maximum age in seconds we will accept a packet (or 0
  11  * for any age); <max-skew> is maximum future age in seconds we will
  12  * accept a packet (or 0 for any future age).
  13  *
  14  */
  15 /*
  16  * This file is part of ipif, part of userv-utils
  17  *
  18  * Copyright 1996-2013 Ian Jackson <ijackson@chiark.greenend.org.uk>
  19  * Copyright 1998 David Damerell <damerell@chiark.greenend.org.uk>
  20  * Copyright 1999,2003
  21  *    Chancellor Masters and Scholars of the University of Cambridge
  22  * Copyright 2010 Tony Finch <fanf@dotat.at>
  23  *
  24  * This is free software; you can redistribute it and/or modify it
  25  * under the terms of the GNU General Public License as published by
  26  * the Free Software Foundation; either version 3 of the License, or
  27  * (at your option) any later version.
  28  *
  29  * This program is distributed in the hope that it will be useful, but
  30  * WITHOUT ANY WARRANTY; without even the implied warranty of
  31  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  32  * General Public License for more details.
  33  *
  34  * You should have received a copy of the GNU General Public License
  35  * along with userv-utils; if not, see http://www.gnu.org/licenses/.
  36  */
  37
  38 #include <stdint.h>
  39 #include <netinet/in.h>
  40
  41 #include "forwarder.h"
  42
  43 #define WARN_EVERY 30
  44
  45 struct mechdata {
  46   time_t max_skew, max_age;
  47   time_t next_warn;
  48 };
  49
  50 static void mds_timestamp(struct mechdata **md_r) {
  51   struct mechdata *md;
  52
  53   md= xmalloc(sizeof(md));
  54
  55   md->max_skew= getarg_ulong();
  56   md->max_age= getarg_ulong();
  57   md->next_warn= now();
  58   *md_r= md;
  59 }
  60
  61 static void mes_timestamp(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) {
  62   mds_timestamp(md_r);
  63   *maxprefix_io += 4;
  64 }
  65
  66 static void menc_timestamp(struct mechdata *md, struct buffer *buf) {
  67   *(uint32_t*)buf_prepend(buf,4)= htonl(now());
  68 }
  69
  70 static const char *mdec_timestamp(struct mechdata *md, struct buffer *buf) {
  71   static char cbuf[40];
  72
  73   uint32_t *tp, timestamp;
  74   time_t tnow;
  75   long age;
  76
  77   BUF_UNPREPEND(tp,buf,4);
  78   timestamp= ntohl(*tp);
  79
  80   tnow= now();
  81   age= timestamp - (uint32_t)tnow;
  82   if (age > 0) {
  83     if (!md->max_age || age <= md->max_age) return 0;
  84     sprintf(cbuf,"packet too old (%lds)",age);
  85   } else if (age < 0) {
  86     if (!md->max_skew || age >= -md->max_skew) return 0;
  87     sprintf(cbuf,"too much skew (%lds)",-age);
  88   } else {
  89     return 0;
  90   }
  91
  92   if (tnow < md->next_warn) return "";
  93
  94   md->next_warn= tnow+WARN_EVERY;
  95   return cbuf;
  96 }
  97
  98 STANDARD_MECHANISMLIST("timestamp",timestamp);