2 Shared library add-on to iptables to add match support for random match.
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
8 2001-10-14 Fabrice MARIE <fabrice@netfilter.org> : initial development.
18 #include <linux/netfilter_ipv4/ip_tables.h>
19 #include <linux/netfilter_ipv4/ipt_random.h>
22 * The kernel random routing returns numbers between 0 and 255.
23 * To ease the task of the user in choosing the probability
24 * of matching, we want him to be able to use percentages.
25 * Therefore we have to accept numbers in percentage here,
26 * turn them into number between 0 and 255 for the kernel module,
27 * and turn them back to percentages when we print/save
32 /* Function which prints out usage message. */
37 "random v%s options:\n"
38 " [--average percent ] The probability in percentage of the match\n"
39 " If ommited, a probability of 50%% percent is set.\n"
40 " Percentage must be within : 1 <= percent <= 99.\n\n",
44 static struct option opts[] = {
45 { "average", 1, 0, '1' },
49 /* Initialize the target. */
51 init(struct ipt_entry_match *m, unsigned int *nfcache)
53 struct ipt_rand_info *randinfo = (struct ipt_rand_info *)(m)->data;
55 /* We assign the average to be 50 which is our default value */
57 randinfo->average = 128;
60 #define IPT_RAND_OPT_AVERAGE 0x01
62 /* Function which parses command options; returns true if it
65 parse(int c, char **argv, int invert, unsigned int *flags,
66 const struct ipt_entry *entry,
67 unsigned int *nfcache,
68 struct ipt_entry_match **match)
70 struct ipt_rand_info *randinfo = (struct ipt_rand_info *)(*match)->data;
75 /* check for common mistakes... */
77 exit_error(PARAMETER_PROBLEM,
78 "Can't specify ! --average");
79 if (*flags & IPT_RAND_OPT_AVERAGE)
80 exit_error(PARAMETER_PROBLEM,
81 "Can't specify --average twice");
83 /* Remember, this function will interpret a leading 0 to be
84 Octal, a leading 0x to be hexdecimal... */
85 if (string_to_number(optarg, 1, 99, &num) == -1 || num < 1)
86 exit_error(PARAMETER_PROBLEM,
87 "bad --average `%s', must be between 1 and 99", optarg);
89 /* assign the values */
90 randinfo->average = (int)(num * 2.55);
91 *flags |= IPT_RAND_OPT_AVERAGE;
99 /* Final check; nothing. */
100 static void final_check(unsigned int flags)
104 /* Prints out the targinfo. */
106 print(const struct ipt_ip *ip,
107 const struct ipt_entry_match *match,
110 const struct ipt_rand_info *randinfo
111 = (const struct ipt_rand_info *)match->data;
112 div_t result = div((randinfo->average*100), 255);
113 if (result.rem > 127) /* round up... */
116 printf(" random %u%% ", result.quot);
119 /* Saves the union ipt_targinfo in parsable form to stdout. */
121 save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
123 const struct ipt_rand_info *randinfo
124 = (const struct ipt_rand_info *)match->data;
125 div_t result = div((randinfo->average *100), 255);
126 if (result.rem > 127) /* round up... */
129 printf("--average %u ", result.quot);
132 struct iptables_match rand_match = {
135 .version = IPTABLES_VERSION,
136 .size = IPT_ALIGN(sizeof(struct ipt_rand_info)),
137 .userspacesize = IPT_ALIGN(sizeof(struct ipt_rand_info)),
141 .final_check = &final_check,
149 register_match(&rand_match);