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Date: Sun, 3 Jun 2007 13:14:03 +0200 (MEST)
From: Jan Engelhardt <jengelh@...ux01.gwdg.de>
To: Netfilter Developer Mailing List
<netfilter-devel@...ts.netfilter.org>
cc: Netfilter Mailing List <netfilter@...ts.netfilter.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/2] xt_connlimit (iptables) - connection limiting
Adds connlimit to iptables.
Signed-off-by: Jan Engelhardt <jengelh@....de>
---
extensions/.connlimit-test | 2
extensions/libipt_connlimit.c | 129 ++++++++++++++++++++++++++++++++++++++++
extensions/libipt_connlimit.man | 21 ++++++
3 files changed, 152 insertions(+)
Index: iptables/extensions/.connlimit-test
===================================================================
--- /dev/null
+++ iptables/extensions/.connlimit-test
@@ -0,0 +1,2 @@
+#!/bin/sh
+[ -f "$KERNEL_DIR/include/linux/netfilter/xt_connlimit.h" ] && echo connlimit
Index: iptables/extensions/libipt_connlimit.c
===================================================================
--- /dev/null
+++ iptables/extensions/libipt_connlimit.c
@@ -0,0 +1,129 @@
+/* Shared library add-on to iptables to add connection limit support. */
+#include <stdio.h>
+#include <netdb.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <getopt.h>
+#include <iptables.h>
+#include <linux/netfilter_ipv4/ip_conntrack.h>
+#include <linux/netfilter_ipv4/xt_connlimit.h>
+
+/* Function which prints out usage message. */
+static void help(void)
+{
+ printf(
+"connlimit v%s options:\n"
+"[!] --connlimit-above n match if the number of existing tcp connections is (not) above n\n"
+" --connlimit-mask n group hosts using mask\n"
+"\n", IPTABLES_VERSION);
+}
+
+static struct option opts[] = {
+ {"connlimit-above", 1, NULL, '1'},
+ {"connlimit-mask", 1, NULL, '2'},
+ {NULL},
+};
+
+/* Function which parses command options; returns true if it
+ ate an option */
+static int parse(int c, char **argv, int invert, unsigned int *flags,
+ const struct ipt_entry *entry, unsigned int *nfcache,
+ struct ipt_entry_match **match)
+{
+ struct xt_connlimit_info *info = (void *)(*match)->data;
+ int i;
+
+ if (!(*flags & 2))
+ /*
+ * set default mask unless we have already seen a mask option
+ */
+ info->mask = htonl(0xFFFFFFFF);
+
+ switch (c) {
+ case '1':
+ check_inverse(optarg, &invert, &optind, 0);
+ info->limit = strtoul(argv[optind-1], NULL, 0);
+ info->inverse = invert;
+ *flags |= 1;
+ break;
+
+ case '2':
+ i = strtol(argv[optind-1], NULL, 0);
+ if (i < 0 || i > 32)
+ exit_error(PARAMETER_PROBLEM,
+ "--connlimit-mask must be between 0 and 32");
+
+ if (i == 0)
+ info->mask = 0;
+ else
+ info->mask = htonl(0xFFFFFFFF << (32 - i));
+
+ *flags |= 2;
+ break;
+
+ default:
+ return 0;
+ }
+
+ return 1;
+}
+
+/* Final check */
+static void final_check(unsigned int flags)
+{
+ if (!(flags & 1))
+ exit_error(PARAMETER_PROBLEM, "You must specify `--connlimit-above'");
+}
+
+static int count_bits(u_int32_t mask)
+{
+ int i, bits;
+
+ for (bits = 0, i = 31; i >= 0; i--) {
+ if (mask & htonl((u_int32_t)1 << i)) {
+ bits++;
+ continue;
+ }
+ break;
+ }
+ return bits;
+}
+
+/* Prints out the matchinfo. */
+static void print(const struct ipt_ip *ip, const struct ipt_entry_match *match,
+ int numeric)
+{
+ const struct xt_connlimit_info *info = (const void *)match->data;
+
+ printf("#conn/%d %s %d ", count_bits(info->mask),
+ info->inverse ? "<" : ">", info->limit);
+}
+
+/* Saves the matchinfo in parsable form to stdout. */
+static void save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
+{
+ const struct xt_connlimit_info *info = (const void *)match->data;
+
+ printf("%s--connlimit-above %u --connlimit-mask %u ",
+ info->inverse ? "! " : "", info->limit,
+ count_bits(info->mask));
+}
+
+static struct iptables_match connlimit = {
+ .name = "connlimit",
+ .version = IPTABLES_VERSION,
+ .size = IPT_ALIGN(sizeof(struct xt_connlimit_info)),
+ .userspacesize = offsetof(struct xt_connlimit_info, data),
+ .help = help,
+ .parse = parse,
+ .final_check = final_check,
+ .print = print,
+ .save = save,
+ .extra_opts = opts,
+};
+
+static __attribute__((constructor)) void libipt_connlimit_init(void)
+{
+ register_match(&connlimit);
+}
Index: iptables/extensions/libipt_connlimit.man
===================================================================
--- /dev/null
+++ iptables/extensions/libipt_connlimit.man
@@ -0,0 +1,21 @@
+Allows you to restrict the number of parallel TCP connections to a
+server per client IP address (or address block).
+.TP
+[\fB!\fR] \fB--connlimit-above \fIn\fR
+match if the number of existing tcp connections is (not) above n
+.TP
+.BI "--connlimit-mask " "bits"
+group hosts using mask
+.P
+Examples:
+.TP
+# allow 2 telnet connections per client host
+iptables -A INPUT -p tcp --syn --dport 23 -m connlimit --connlimit-above 2 -j REJECT
+.TP
+# you can also match the other way around:
+iptables -A INPUT -p tcp --syn --dport 23 -m connlimit ! --connlimit-above 2 -j ACCEPT
+.TP
+# limit the nr of parallel http requests to 16 per class C sized \
+network (24 bit netmask)
+iptables -p tcp --syn --dport 80 -m connlimit --connlimit-above 16
+--connlimit-mask 24 -j REJECT
-
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