extensions/ebt_limit.c

/* Shared library add-on to ebtables to add limit support.
 *
 * Swipted from iptables' limit match.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
#include "../include/ebtables_u.h"
#include <linux/netfilter_bridge/ebt_limit.h>

#define EBT_LIMIT_AVG	"3/hour"
#define EBT_LIMIT_BURST	5

/* from iptables.c */
#include <errno.h>
int
string_to_number(const char *s, unsigned int min, unsigned int max,
		 unsigned int *ret)
{
	long number;
	char *end;

	/* Handle hex, octal, etc. */
	errno = 0;
	number = strtol(s, &end, 0);
	if (*end == '\0' && end != s) {
		/* we parsed a number, let's see if we want this */
		if (errno != ERANGE && min <= number && number <= max) {
			*ret = number;
			return 0;
		}
	}
	return -1;
}

#define FLAG_LIMIT		0x01
#define FLAG_LIMIT_BURST	0x02

#define ARG_LIMIT		'1'
#define ARG_LIMIT_BURST		'2'

static struct option opts[] =
{
	{ "limit",		required_argument, 0, ARG_LIMIT },
	{ "limit-burst",	required_argument, 0, ARG_LIMIT_BURST },
	{ 0 }
};

static void print_help(void)
{
	printf(
"limit options:\n"
"--limit avg			max average match rate: default "EBT_LIMIT_AVG"\n"
"                                [Packets per second unless followed by \n"
"                                /sec /minute /hour /day postfixes]\n"
"--limit-burst number		number to match in a burst, -1 < number < 10001,\n"
"                                default %u\n"
"\n", EBT_LIMIT_BURST);
}

static int parse_rate(const char *rate, u_int32_t *val)
{
	const char *delim;
	u_int32_t r;
	u_int32_t mult = 1;  /* Seconds by default. */

	delim = strchr(rate, '/');
	if (delim) {
		if (strlen(delim+1) == 0)
			return 0;

		if (strncasecmp(delim+1, "second", strlen(delim+1)) == 0)
			mult = 1;
		else if (strncasecmp(delim+1, "minute", strlen(delim+1)) == 0)
			mult = 60;
		else if (strncasecmp(delim+1, "hour", strlen(delim+1)) == 0)
			mult = 60*60;
		else if (strncasecmp(delim+1, "day", strlen(delim+1)) == 0)
			mult = 24*60*60;
		else
			return 0;
	}
	r = atoi(rate);
	if (!r)
		return 0;

	/* This would get mapped to infinite (1/day is minimum they
	   can specify, so we're ok at that end). */
	if (r / mult > EBT_LIMIT_SCALE)
		return 0;

	*val = EBT_LIMIT_SCALE * mult / r;
	return 1;
}

/* Initialize the match. */
static void init(struct ebt_entry_match *m)
{
	struct ebt_limit_info *r = (struct ebt_limit_info *)m->data;

	parse_rate(EBT_LIMIT_AVG, &r->avg);
	r->burst = EBT_LIMIT_BURST;
}

/* FIXME: handle overflow:
	if (r->avg*r->burst/r->burst != r->avg)
		exit_error(PARAMETER_PROBLEM,
			   "Sorry: burst too large for that avg rate.\n");
*/

static int parse(int c, char **argv, int argc,
      const struct ebt_u_entry *entry,
      unsigned int *flags,
      struct ebt_entry_match **match)
{
	struct ebt_limit_info *r = (struct ebt_limit_info *)(*match)->data;
	unsigned int num;

	switch(c) {
	case ARG_LIMIT:
		check_option(flags, FLAG_LIMIT);
		if (check_inverse(optarg))
			print_error("Unexpected `!' after --limit");
		if (!parse_rate(optarg, &r->avg))
			print_error("bad rate `%s'", optarg);
		break;

	case ARG_LIMIT_BURST:
		check_option(flags, FLAG_LIMIT_BURST);
		if (check_inverse(optarg))
			print_error("Unexpected `!' after --limit-burst");

		if (string_to_number(optarg, 0, 10000, &num) == -1)
			print_error("bad --limit-burst `%s'", optarg);
		r->burst = num;
		break;

	default:
		return 0;
	}

	return 1;
}

static void final_check(unsigned int flags)
{
	/* empty */
}

struct rates
{
	const char *name;
	u_int32_t mult;
};

static struct rates g_rates[] =
{
	{ "day", EBT_LIMIT_SCALE*24*60*60 },
	{ "hour", EBT_LIMIT_SCALE*60*60 },
	{ "min", EBT_LIMIT_SCALE*60 },
	{ "sec", EBT_LIMIT_SCALE }
};

static void print_rate(u_int32_t period)
{
	unsigned int i;

	for (i = 1; i < sizeof(g_rates)/sizeof(struct rates); i++)
		if (period > g_rates[i].mult ||
		    g_rates[i].mult/period < g_rates[i].mult%period)
			break;

	printf("%u/%s ", g_rates[i-1].mult / period, g_rates[i-1].name);
}

/* Prints out the matchinfo. */
static void
print(const struct ebt_u_entry *entry, const struct ebt_entry_match *match)
{
	struct ebt_limit_info *r = (struct ebt_limit_info *)match->data;

	printf("limit: avg "); print_rate(r->avg);
	printf("burst %u ", r->burst);
}

static int compare(const struct ebt_entry_match* m1, const struct ebt_entry_match *m2)
{
	struct ebt_limit_info* li1 = (struct ebt_limit_info*)m1->data;
	struct ebt_limit_info* li2 = (struct ebt_limit_info*)m2->data;

	if (li1->avg != li2->avg)
		return 0;

	if (li1->burst != li2->burst)
		return 0;

	return 1;
}

static struct ebt_u_match limit_match =
{
	.name		EBT_LIMIT_MATCH,
	.size		sizeof(struct ebt_limit_info),
	.help		print_help,
	.init		init,
	.parse		parse,
	.final_check	final_check,
	.print		print,
	.compare	compare,
	.extra_ops	opts,
};

static void _init(void) __attribute((constructor));
static void _init(void)
{
	register_match(&limit_match);
}