ipaddr match (from "Writing your own Netfilter module" PDF)

2025-09-15 17:14:57 +02:00 · 2009-03-25 21:53:11 +01:00
parent 48ebf55444
commit 867a920fd7
7 changed files with 424 additions and 0 deletions
--- a/extensions/xt_ipaddr.c
+++ b/extensions/xt_ipaddr.c
@@ -0,0 +1,141 @@
+/*
+ *	"ipaddr" demo match for Xtables
+ *	Copyright © Jan Engelhardt, 2008-2009
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the WTF Public License version 2 or
+ *      (at your option) any later version.
+ */
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/module.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter/x_tables.h>
+#include <net/ipv6.h>
+#include "compat_xtables.h"
+#include "xt_ipaddr.h"
+
+static bool ipaddr_mt4(const struct sk_buff *skb, struct xt_action_param *par)
+{
+	const struct xt_ipaddr_mtinfo *info = par->matchinfo;
+	const struct iphdr *iph = ip_hdr(skb);
+
+	printk(KERN_INFO
+	       "xt_ipaddr: IN=%s OUT=%s "
+	       "SRC=" NIPQUAD_FMT " DST=" NIPQUAD_FMT " "
+	       "IPSRC=" NIPQUAD_FMT " IPDST=" NIPQUAD_FMT "\n",
+	       (par->in != NULL) ? par->in->name : "",
+	       (par->out != NULL) ? par->out->name : "",
+	       NIPQUAD(iph->saddr), NIPQUAD(iph->daddr),
+	       NIPQUAD(info->src), NIPQUAD(info->dst));
+
+	if (info->flags & XT_IPADDR_SRC)
+		if ((iph->saddr != info->src.ip) ^
+		    !!(info->flags & XT_IPADDR_SRC_INV)) {
+			printk(KERN_NOTICE "src IP - no match\n");
+			return false;
+		}
+
+	if (info->flags & XT_IPADDR_DST)
+		if ((iph->daddr != info->dst.ip) ^
+		    !!(info->flags & XT_IPADDR_DST_INV)) {
+			printk(KERN_NOTICE "dst IP - no match\n");
+			return false;
+		}
+
+	return true;
+}
+
+static bool ipaddr_mt6(const struct sk_buff *skb, struct xt_action_param *par)
+{
+	const struct xt_ipaddr_mtinfo *info = par->matchinfo;
+	const struct ipv6hdr *iph = ipv6_hdr(skb);
+
+	printk(KERN_INFO
+	       "xt_ipaddr: IN=%s OUT=%s "
+	       "SRC=" NIP6_FMT " DST=" NIP6_FMT " "
+	       "IPSRC=" NIP6_FMT " IPDST=" NIP6_FMT "\n",
+	       (par->in != NULL) ? par->in->name : "",
+	       (par->out != NULL) ? par->out->name : "",
+	       NIP6(iph->saddr), NIP6(iph->daddr),
+	       NIP6(info->src.in6), NIP6(info->dst.in6));
+
+	if (info->flags & XT_IPADDR_SRC)
+		if ((ipv6_addr_cmp(&iph->saddr, &info->src.in6) != 0) ^
+		    !!(info->flags & XT_IPADDR_SRC_INV)) {
+			printk(KERN_NOTICE "src IP - no match\n");
+			return false;
+		}
+
+	if (info->flags & XT_IPADDR_DST)
+		if ((ipv6_addr_cmp(&iph->daddr, &info->dst.in6) != 0) ^
+		    !!(info->flags & XT_IPADDR_DST_INV)) {
+			printk(KERN_NOTICE "dst IP - no match\n");
+			return false;
+		}
+
+	return true;
+}
+
+static int ipaddr_mt_check(const struct xt_mtchk_param *par)
+{
+	const struct xt_ipaddr_mtinfo *info = par->matchinfo;
+
+	printk(KERN_INFO "xt_ipaddr: Added a rule with -m ipaddr in "
+	       "the %s table; this rule is reachable through hooks 0x%x\n",
+	       par->table, par->hook_mask);
+
+	if (par->match->family == NFPROTO_IPV4 &&
+	    ntohl(info->src.ip) == 0xDEADBEEF) {
+		printk(KERN_INFO "xt_ipaddr: I just thought I do not want "
+		       "to let you match on 222.173.190.239\n");
+		return -EPERM;
+	}
+
+	return 0;
+}
+
+static void ipaddr_mt_destroy(const struct xt_mtdtor_param *par)
+{
+	printk(KERN_INFO "One rule with ipaddr match got deleted\n");
+}
+
+static struct xt_match ipaddr_mt_reg[] __read_mostly = {
+	{
+		.name       = "ipaddr",
+		.revision   = 0,
+		.family     = NFPROTO_IPV4,
+		.match      = ipaddr_mt4,
+		.checkentry = ipaddr_mt_check,
+		.destroy    = ipaddr_mt_destroy,
+		.matchsize  = XT_ALIGN(sizeof(struct xt_ipaddr_mtinfo)),
+		.me         = THIS_MODULE,
+	},
+	{
+		.name       = "ipaddr",
+		.revision   = 0,
+		.family     = NFPROTO_IPV6,
+		.match      = ipaddr_mt6,
+		.checkentry = ipaddr_mt_check,
+		.destroy    = ipaddr_mt_destroy,
+		.matchsize  = XT_ALIGN(sizeof(struct xt_ipaddr_mtinfo)),
+		.me         = THIS_MODULE,
+	},
+};
+
+static int __init ipaddr_mt_init(void)
+{
+	return xt_register_matches(ipaddr_mt_reg, ARRAY_SIZE(ipaddr_mt_reg));
+}
+
+static void __exit ipaddr_mt_exit(void)
+{
+	xt_unregister_matches(ipaddr_mt_reg, ARRAY_SIZE(ipaddr_mt_reg));
+}
+
+module_init(ipaddr_mt_init);
+module_exit(ipaddr_mt_exit);
+MODULE_DESCRIPTION("Xtables: Match source/destination address");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ipt_ipaddr");
+MODULE_ALIAS("ip6t_ipaddr");