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

   1 /* Shared library add-on to iptables to add packet length matching support. */
   2 #include <stdio.h>
   3 #include <netdb.h>
   4 #include <string.h>
   5 #include <stdlib.h>
   6 #include <getopt.h>
   7
   8 #include <iptables.h>
   9 #include <linux/netfilter_ipv4/ipt_length.h>
  10
  11 /* Function which prints out usage message. */
  12 static void
  13 help(void)
  14 {
  15         printf(
  16 "length v%s options:\n"
  17 "[!] --length length[:length]    Match packet length against value or range\n"
  18 "                                of values (inclusive)\n",
  19 IPTABLES_VERSION);
  20
  21 }
  22
  23 static struct option opts[] = {
  24         { "length", 1, 0, '1' },
  25         {0}
  26 };
  27
  28 static u_int16_t
  29 parse_length(const char *s)
  30 {
  31         unsigned int len;
  32
  33         if (string_to_number(s, 0, 0xFFFF, &len) == -1)
  34                 exit_error(PARAMETER_PROBLEM, "length invalid: `%s'\n", s);
  35         else
  36                 return (u_int16_t )len;
  37 }
  38
  39 /* If a single value is provided, min and max are both set to the value */
  40 static void
  41 parse_lengths(const char *s, struct ipt_length_info *info)
  42 {
  43         char *buffer;
  44         char *cp;
  45
  46         buffer = strdup(s);
  47         if ((cp = strchr(buffer, ':')) == NULL)
  48                 info->min = info->max = parse_length(buffer);
  49         else {
  50                 *cp = '\0';
  51                 cp++;
  52
  53                 info->min = buffer[0] ? parse_length(buffer) : 0;
  54                 info->max = cp[0] ? parse_length(cp) : 0xFFFF;
  55         }
  56         free(buffer);
  57
  58         if (info->min > info->max)
  59                 exit_error(PARAMETER_PROBLEM,
  60                            "length min. range value `%u' greater than max. "
  61                            "range value `%u'", info->min, info->max);
  62
  63 }
  64
  65 /* Function which parses command options; returns true if it
  66    ate an option */
  67 static int
  68 parse(int c, char **argv, int invert, unsigned int *flags,
  69       const struct ipt_entry *entry,
  70       unsigned int *nfcache,
  71       struct ipt_entry_match **match)
  72 {
  73         struct ipt_length_info *info = (struct ipt_length_info *)(*match)->data;
  74
  75         switch (c) {
  76                 case '1':
  77                         if (*flags)
  78                                 exit_error(PARAMETER_PROBLEM,
  79                                            "length: `--length' may only be "
  80                                            "specified once");
  81                         check_inverse(optarg, &invert, &optind, 0);
  82                         parse_lengths(argv[optind-1], info);
  83                         if (invert)
  84                                 info->invert = 1;
  85                         *flags = 1;
  86                         break;
  87
  88                 default:
  89                         return 0;
  90         }
  91         return 1;
  92 }
  93
  94 /* Final check; must have specified --length. */
  95 static void
  96 final_check(unsigned int flags)
  97 {
  98         if (!flags)
  99                 exit_error(PARAMETER_PROBLEM,
 100                            "length: You must specify `--length'");
 101 }
 102
 103 /* Common match printing code. */
 104 static void
 105 print_length(struct ipt_length_info *info)
 106 {
 107         if (info->invert)
 108                 printf("! ");
 109
 110         if (info->max == info->min)
 111                 printf("%u ", info->min);
 112         else
 113                 printf("%u:%u ", info->min, info->max);
 114 }
 115
 116 /* Prints out the matchinfo. */
 117 static void
 118 print(const struct ipt_ip *ip,
 119       const struct ipt_entry_match *match,
 120       int numeric)
 121 {
 122         printf("length ");
 123         print_length((struct ipt_length_info *)match->data);
 124 }
 125
 126 /* Saves the union ipt_matchinfo in parsable form to stdout. */
 127 static void
 128 save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
 129 {
 130         printf("--length ");
 131         print_length((struct ipt_length_info *)match->data);
 132 }
 133
 134 static struct iptables_match length = {
 135         .next           = NULL,
 136         .name           = "length",
 137         .version        = IPTABLES_VERSION,
 138         .size           = IPT_ALIGN(sizeof(struct ipt_length_info)),
 139         .userspacesize  = IPT_ALIGN(sizeof(struct ipt_length_info)),
 140         .help           = &help,
 141         .parse          = &parse,
 142         .final_check    = &final_check,
 143         .print          = &print,
 144         .save           = &save,
 145         .extra_opts     = opts
 146 };
 147
 148 void _init(void)
 149 {
 150         register_match(&length);
 151 }