release/src/router/iptables/extensions/libip6t_random.c

   1 /*
   2    Shared library add-on to iptables to add match support for random match.
   3
   4    This file is distributed under the terms of the GNU General Public
   5    License (GPL). Copies of the GPL can be obtained from:
   6    ftp://prep.ai.mit.edu/pub/gnu/GPL
   7
   8    2001-10-14 Fabrice MARIE <fabrice@netfilter.org> : initial development.
   9    2003-04-30 Maciej Soltysiak <solt@dns.toxicfilms.tv> : IPv6 port.
  10 */
  11
  12 #include <stdio.h>
  13 #include <netdb.h>
  14 #include <string.h>
  15 #include <stdlib.h>
  16 #include <syslog.h>
  17 #include <getopt.h>
  18 #include <ip6tables.h>
  19 #include <linux/netfilter_ipv6/ip6_tables.h>
  20 #include <linux/netfilter_ipv6/ip6t_random.h>
  21
  22 /**
  23  * The kernel random routing returns numbers between 0 and 255.
  24  * To ease the task of the user in choosing the probability
  25  * of matching, we want him to be able to use percentages.
  26  * Therefore we have to accept numbers in percentage here,
  27  * turn them into number between 0 and 255 for the kernel module,
  28  * and turn them back to percentages when we print/save
  29  * the rule.
  30  */
  31
  32
  33 /* Function which prints out usage message. */
  34 static void
  35 help(void)
  36 {
  37         printf(
  38 "random v%s options:\n"
  39 "  [--average]     percent      The probability in percentage of the match\n"
  40 "                               If ommited, a probability of 50%% percent is set.\n"
  41 "                               Percentage must be within : 1 <= percent <= 99.\n\n",
  42 IPTABLES_VERSION);
  43 }
  44
  45 static struct option opts[] = {
  46         { "average", 1, 0, '1' },
  47         { 0 }
  48 };
  49
  50 /* Initialize the target. */
  51 static void
  52 init(struct ip6t_entry_match *m, unsigned int *nfcache)
  53 {
  54         struct ip6t_rand_info *randinfo = (struct ip6t_rand_info *)(m)->data;
  55
  56         /* We assign the average to be 50 which is our default value */
  57         /* 50 * 2.55 = 128 */
  58         randinfo->average = 128;
  59 }
  60
  61 #define IP6T_RAND_OPT_AVERAGE   0x01
  62
  63 /* Function which parses command options; returns true if it
  64    ate an option */
  65 static int
  66 parse(int c, char **argv, int invert, unsigned int *flags,
  67       const struct ip6t_entry *entry,
  68       unsigned int *nfcache,
  69       struct ip6t_entry_match **match)
  70 {
  71         struct ip6t_rand_info *randinfo = (struct ip6t_rand_info *)(*match)->data;
  72         unsigned int num;
  73
  74         switch (c) {
  75         case '1':
  76                 /* check for common mistakes... */
  77                 if (invert)
  78                         exit_error(PARAMETER_PROBLEM,
  79                                    "Can't specify ! --average");
  80                 if (*flags & IP6T_RAND_OPT_AVERAGE)
  81                         exit_error(PARAMETER_PROBLEM,
  82                                    "Can't specify --average twice");
  83
  84                 /* Remember, this function will interpret a leading 0 to be
  85                    Octal, a leading 0x to be hexdecimal... */
  86                 if (string_to_number(optarg, 1, 99, &num) == -1 || num < 1)
  87                         exit_error(PARAMETER_PROBLEM,
  88                                    "bad --average `%s', must be between 1 and 99", optarg);
  89
  90                 /* assign the values */
  91                 randinfo->average = (int)(num * 2.55);
  92                 *flags |= IP6T_RAND_OPT_AVERAGE;
  93                 break;
  94         default:
  95                 return 0;
  96         }
  97         return 1;
  98 }
  99
 100 /* Final check; nothing. */
 101 static void final_check(unsigned int flags)
 102 {
 103 }
 104
 105 /* Prints out the targinfo. */
 106 static void
 107 print(const struct ip6t_ip6 *ip,
 108       const struct ip6t_entry_match *match,
 109       int numeric)
 110 {
 111         const struct ip6t_rand_info *randinfo
 112                 = (const struct ip6t_rand_info *)match->data;
 113         div_t result = div((randinfo->average*100), 255);
 114         if (result.rem > 127)  /* round up... */
 115                 ++result.quot;
 116
 117         printf(" random %u%% ", result.quot);
 118 }
 119
 120 /* Saves the union ip6t_targinfo in parsable form to stdout. */
 121 static void
 122 save(const struct ip6t_ip6 *ip, const struct ip6t_entry_match *match)
 123 {
 124         const struct ip6t_rand_info *randinfo
 125                 = (const struct ip6t_rand_info *)match->data;
 126         div_t result = div((randinfo->average *100), 255);
 127         if (result.rem > 127)  /* round up... */
 128                 ++result.quot;
 129
 130         printf("--average %u ", result.quot);
 131 }
 132
 133 struct ip6tables_match rand_match = {
 134         .name           = "random",
 135         .version        = IPTABLES_VERSION,
 136         .size           = IP6T_ALIGN(sizeof(struct ip6t_rand_info)),
 137         .userspacesize  = IP6T_ALIGN(sizeof(struct ip6t_rand_info)),
 138         .help           = &help,
 139         .init           = &init,
 140         .parse          = &parse,
 141         .final_check    = &final_check,
 142         .print          = &print,
 143         .save           = &save,
 144         .extra_opts     = opts,
 145 };
 146
 147 void _init(void)
 148 {
 149         register_match6(&rand_match);
 150 }