ebtables-compat: add support for limit extension

new file mode 100644
index 0000000..c71561c
@@ -0,0 +1,179 @@
+/* ebt_limit
+ *
+ * Authors:
+ * Tom Marshall <[email protected]>
+ *
+ * Mostly copied from iptables' limit match.
+ *
+ * September, 2003
+ *
+ * Translated to use libxtables for ebtables-compat in 2015 by
+ * Arturo Borrero Gonzalez <[email protected]>
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <getopt.h>
+#include <errno.h>
+#include <xtables.h>
+#include <linux/netfilter_bridge/ebt_limit.h>
+#include "iptables/nft.h"
+#include "iptables/nft-bridge.h"
+
+#define EBT_LIMIT_AVG	"3/hour"
+#define EBT_LIMIT_BURST	5
+
+#define FLAG_LIMIT		0x01
+#define FLAG_LIMIT_BURST	0x02
+#define ARG_LIMIT		'1'
+#define ARG_LIMIT_BURST		'2'
+
+static struct option brlimit_opts[] =
+{
+	{ .name = "limit",	.has_arg = true,	.val = ARG_LIMIT },
+	{ .name = "limit-burst",.has_arg = true,	.val = ARG_LIMIT_BURST },
+	XT_GETOPT_TABLEEND,
+};
+
+static void brlimit_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", EBT_LIMIT_BURST);
+}
+
+static int parse_rate(const char *rate, uint32_t *val)
+{
+	const char *delim;
+	uint32_t r;
+	uint32_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;
+}
+
+static void brlimit_init(struct xt_entry_match *match)
+{
+	struct ebt_limit_info *r = (struct ebt_limit_info *)match->data;
+
+	parse_rate(EBT_LIMIT_AVG, &r->avg);
+	r->burst = EBT_LIMIT_BURST;
+}
+
+static int brlimit_parse(int c, char **argv, int invert, unsigned int *flags,
+			 const void *entry, struct xt_entry_match **match)
+{
+	struct ebt_limit_info *r = (struct ebt_limit_info *)(*match)->data;
+	uintmax_t num;
+
+	switch (c) {
+	case ARG_LIMIT:
+		EBT_CHECK_OPTION(flags, FLAG_LIMIT);
+		if (invert)
+			xtables_error(PARAMETER_PROBLEM,
+				      "Unexpected `!' after --limit");
+		if (!parse_rate(optarg, &r->avg))
+			xtables_error(PARAMETER_PROBLEM,
+				      "bad rate `%s'", optarg);
+		break;
+	case ARG_LIMIT_BURST:
+		EBT_CHECK_OPTION(flags, FLAG_LIMIT_BURST);
+		if (invert)
+			xtables_error(PARAMETER_PROBLEM,
+				      "Unexpected `!' after --limit-burst");
+		if (!xtables_strtoul(optarg, NULL, &num, 0, 10000))
+			xtables_error(PARAMETER_PROBLEM,
+				      "bad --limit-burst `%s'", optarg);
+		r->burst = num;
+		break;
+	default:
+		return 0;
+	}
+
+	return 1;
+}
+
+struct rates
+{
+	const char	*name;
+	uint32_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(uint32_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);
+}
+
+static void brlimit_print(const void *ip, const struct xt_entry_match *match,
+			  int numeric)
+{
+	struct ebt_limit_info *r = (struct ebt_limit_info *)match->data;
+
+	printf("--limit ");
+	print_rate(r->avg);
+	printf("--limit-burst %u ", r->burst);
+}
+
+static struct xtables_match brlimit_match = {
+	.name		= "limit",
+	.revision	= 0,
+	.version	= XTABLES_VERSION,
+	.family		= NFPROTO_BRIDGE,
+	.size		= XT_ALIGN(sizeof(struct ebt_limit_info)),
+	.userspacesize	= offsetof(struct ebt_limit_info, prev),
+	.init		= brlimit_init,
+	.help		= brlimit_print_help,
+	.parse		= brlimit_parse,
+	.print		= brlimit_print,
+	.extra_opts	= brlimit_opts,
+};
+
+void _init(void)
+{
+	xtables_register_match(&brlimit_match);
+}

index efbb3cd..90d89cc 100644
@@ -643,6 +643,7 @@ static void ebt_load_match_extensions(void)
 	ebt_load_match("802_3");
 	ebt_load_match("ip");
 	ebt_load_match("mark_m");
+	ebt_load_match("limit");
 
 	ebt_load_watcher("log");
 }