[NETFILTER]: add comment match

2.4 version by Brad Fisher <brad@info-link.net>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter_ipv4/ipt_comment.h

+#ifndef _IPT_COMMENT_H
+#define _IPT_COMMENT_H
+
+#define IPT_MAX_COMMENT_LEN 256
+
+struct ipt_comment_info {
+	unsigned char comment[IPT_MAX_COMMENT_LEN];
+};
+
+#endif /* _IPT_COMMENT_H */

net/ipv4/netfilter/Kconfig

@@ -332,6 +332,16 @@ config IP_NF_MATCH_SCTP
 	  If you want to compile it as a module, say M here and read
 	  Documentation/modules.txt.  If unsure, say `N'.
 
+config IP_NF_MATCH_COMMENT
+	tristate  'comment match support'
+	depends on IP_NF_IPTABLES
+	help
+	  This option adds a `comment' dummy-match, which allows you to put
+	  comments in your iptables ruleset.
+
+	  If you want to compile it as a module, say M here and read
+	  Documentation/modules.txt.  If unsure, say `N'.
+
 # `filter', generic and specific targets
 config IP_NF_FILTER
 	tristate "Packet filtering"

net/ipv4/netfilter/Makefile

@@ -50,28 +50,23 @@ obj-$(CONFIG_IP_NF_MATCH_SCTP) += ipt_sctp.o
 obj-$(CONFIG_IP_NF_MATCH_MARK) += ipt_mark.o
 obj-$(CONFIG_IP_NF_MATCH_MAC) += ipt_mac.o
 obj-$(CONFIG_IP_NF_MATCH_IPRANGE) += ipt_iprange.o
-
 obj-$(CONFIG_IP_NF_MATCH_PKTTYPE) += ipt_pkttype.o
 obj-$(CONFIG_IP_NF_MATCH_MULTIPORT) += ipt_multiport.o
 obj-$(CONFIG_IP_NF_MATCH_OWNER) += ipt_owner.o
 obj-$(CONFIG_IP_NF_MATCH_TOS) += ipt_tos.o
-
 obj-$(CONFIG_IP_NF_MATCH_RECENT) += ipt_recent.o
-
 obj-$(CONFIG_IP_NF_MATCH_ECN) += ipt_ecn.o
 obj-$(CONFIG_IP_NF_MATCH_DSCP) += ipt_dscp.o
 obj-$(CONFIG_IP_NF_MATCH_AH_ESP) += ipt_ah.o ipt_esp.o
-
 obj-$(CONFIG_IP_NF_MATCH_LENGTH) += ipt_length.o
-
 obj-$(CONFIG_IP_NF_MATCH_TTL) += ipt_ttl.o
 obj-$(CONFIG_IP_NF_MATCH_STATE) += ipt_state.o
 obj-$(CONFIG_IP_NF_MATCH_CONNTRACK) += ipt_conntrack.o
 obj-$(CONFIG_IP_NF_MATCH_TCPMSS) += ipt_tcpmss.o
 obj-$(CONFIG_IP_NF_MATCH_REALM) += ipt_realm.o
 obj-$(CONFIG_IP_NF_MATCH_ADDRTYPE) += ipt_addrtype.o
-
 obj-$(CONFIG_IP_NF_MATCH_PHYSDEV) += ipt_physdev.o
+obj-$(CONFIG_IP_NF_MATCH_COMMENT) += ipt_comment.o
 
 # targets
 obj-$(CONFIG_IP_NF_TARGET_REJECT) += ipt_REJECT.o

net/ipv4/netfilter/ipt_comment.c

+/*
+ * Implements a dummy match to allow attaching comments to rules
+ *
+ * 2003-05-13 Brad Fisher (brad@info-link.net)
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv4/ipt_comment.h>
+
+MODULE_AUTHOR("Brad Fisher <brad@info-link.net>");
+MODULE_DESCRIPTION("iptables comment match module");
+MODULE_LICENSE("GPL");
+
+static int
+match(const struct sk_buff *skb,
+      const struct net_device *in,
+      const struct net_device *out,
+      const void *matchinfo,
+      int offset,
+      int *hotdrop)
+{
+	/* We always match */
+	return 1;
+}
+
+static int
+checkentry(const char *tablename,
+           const struct ipt_ip *ip,
+           void *matchinfo,
+           unsigned int matchsize,
+           unsigned int hook_mask)
+{
+	/* Check the size */
+	if (matchsize != IPT_ALIGN(sizeof(struct ipt_comment_info)))
+		return 0;
+	return 1;
+}
+
+static struct ipt_match comment_match = {
+	.name		= "comment",
+	.match		= match,
+	.checkentry	= checkentry,
+	.me		= THIS_MODULE
+};
+
+static int __init init(void)
+{
+	return ipt_register_match(&comment_match);
+}
+
+static void __exit fini(void)
+{
+	ipt_unregister_match(&comment_match);
+}
+
+module_init(init);
+module_exit(fini);