[NETFILTER] x_tables: Abstraction layer for {ip,ip6,arp}_tables

This monster-patch tries to do the best job for unifying the data
structures and backend interfaces for the three evil clones ip_tables,
ip6_tables and arp_tables.  In an ideal world we would never have
allowed this kind of copy+paste programming... but well, our world
isn't (yet?) ideal.

o introduce a new x_tables module
o {ip,arp,ip6}_tables depend on this x_tables module
o registration functions for tables, matches and targets are only
  wrappers around x_tables provided functions
o all matches/targets that are used from ip_tables and ip6_tables
  are now implemented as xt_FOOBAR.c files and provide module aliases
  to ipt_FOOBAR and ip6t_FOOBAR
o header files for xt_matches are in include/linux/netfilter/,
  include/linux/netfilter_{ipv4,ipv6} contains compatibility wrappers
  around the xt_FOOBAR.h headers

Based on this patchset we're going to further unify the code,
gradually getting rid of all the layer 3 specific assumptions.

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 221 insertions, 0 deletions

diff --git a/net/netfilter/xt_dccp.c b/net/netfilter/xt_dccp.c
new file mode 100644
index 000000000000..779f42fc9524
--- /dev/null
+++ b/net/netfilter/xt_dccp.c
@@ -0,0 +1,221 @@
+/*
+ * iptables module for DCCP protocol header matching
+ *
+ * (C) 2005 by Harald Welte <laforge@netfilter.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/spinlock.h>
+#include <net/ip.h>
+#include <linux/dccp.h>
+
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter/xt_dccp.h>
+
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv6/ip6_tables.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
+MODULE_DESCRIPTION("Match for DCCP protocol packets");
+MODULE_ALIAS("ipt_dccp");
+
+#define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
+		                  || (!!((invflag) & (option)) ^ (cond)))
+
+static unsigned char *dccp_optbuf;
+static DEFINE_SPINLOCK(dccp_buflock);
+
+static inline int
+dccp_find_option(u_int8_t option,
+		 const struct sk_buff *skb,
+		 unsigned int protoff,
+		 const struct dccp_hdr *dh,
+		 int *hotdrop)
+{
+	/* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
+	unsigned char *op;
+	unsigned int optoff = __dccp_hdr_len(dh);
+	unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh);
+	unsigned int i;
+
+	if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) {
+		*hotdrop = 1;
+		return 0;
+	}
+
+	if (!optlen)
+		return 0;
+
+	spin_lock_bh(&dccp_buflock);
+	op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf);
+	if (op == NULL) {
+		/* If we don't have the whole header, drop packet. */
+		spin_unlock_bh(&dccp_buflock);
+		*hotdrop = 1;
+		return 0;
+	}
+
+	for (i = 0; i < optlen; ) {
+		if (op[i] == option) {
+			spin_unlock_bh(&dccp_buflock);
+			return 1;
+		}
+
+		if (op[i] < 2) 
+			i++;
+		else 
+			i += op[i+1]?:1;
+	}
+
+	spin_unlock_bh(&dccp_buflock);
+	return 0;
+}
+
+
+static inline int
+match_types(const struct dccp_hdr *dh, u_int16_t typemask)
+{
+	return (typemask & (1 << dh->dccph_type));
+}
+
+static inline int
+match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff,
+	     const struct dccp_hdr *dh, int *hotdrop)
+{
+	return dccp_find_option(option, skb, protoff, dh, hotdrop);
+}
+
+static int
+match(const struct sk_buff *skb,
+      const struct net_device *in,
+      const struct net_device *out,
+      const void *matchinfo,
+      int offset,
+      unsigned int protoff,
+      int *hotdrop)
+{
+	const struct xt_dccp_info *info = 
+				(const struct xt_dccp_info *)matchinfo;
+	struct dccp_hdr _dh, *dh;
+
+	if (offset)
+		return 0;
+	
+	dh = skb_header_pointer(skb, protoff, sizeof(_dh), &_dh);
+	if (dh == NULL) {
+		*hotdrop = 1;
+		return 0;
+       	}
+
+	return  DCCHECK(((ntohs(dh->dccph_sport) >= info->spts[0]) 
+			&& (ntohs(dh->dccph_sport) <= info->spts[1])), 
+		   	XT_DCCP_SRC_PORTS, info->flags, info->invflags)
+		&& DCCHECK(((ntohs(dh->dccph_dport) >= info->dpts[0]) 
+			&& (ntohs(dh->dccph_dport) <= info->dpts[1])), 
+			XT_DCCP_DEST_PORTS, info->flags, info->invflags)
+		&& DCCHECK(match_types(dh, info->typemask),
+			   XT_DCCP_TYPE, info->flags, info->invflags)
+		&& DCCHECK(match_option(info->option, skb, protoff, dh,
+					hotdrop),
+			   XT_DCCP_OPTION, info->flags, info->invflags);
+}
+
+static int
+checkentry(const char *tablename,
+	   const void *inf,
+	   void *matchinfo,
+	   unsigned int matchsize,
+	   unsigned int hook_mask)
+{
+	const struct ipt_ip *ip = inf;
+	const struct xt_dccp_info *info;
+
+	info = (const struct xt_dccp_info *)matchinfo;
+
+	return ip->proto == IPPROTO_DCCP
+		&& !(ip->invflags & XT_INV_PROTO)
+		&& matchsize == XT_ALIGN(sizeof(struct xt_dccp_info))
+		&& !(info->flags & ~XT_DCCP_VALID_FLAGS)
+		&& !(info->invflags & ~XT_DCCP_VALID_FLAGS)
+		&& !(info->invflags & ~info->flags);
+}
+
+static int
+checkentry6(const char *tablename,
+	   const void *inf,
+	   void *matchinfo,
+	   unsigned int matchsize,
+	   unsigned int hook_mask)
+{
+	const struct ip6t_ip6 *ip = inf;
+	const struct xt_dccp_info *info;
+
+	info = (const struct xt_dccp_info *)matchinfo;
+
+	return ip->proto == IPPROTO_DCCP
+		&& !(ip->invflags & XT_INV_PROTO)
+		&& matchsize == XT_ALIGN(sizeof(struct xt_dccp_info))
+		&& !(info->flags & ~XT_DCCP_VALID_FLAGS)
+		&& !(info->invflags & ~XT_DCCP_VALID_FLAGS)
+		&& !(info->invflags & ~info->flags);
+}
+
+
+static struct xt_match dccp_match = 
+{ 
+	.name 		= "dccp",
+	.match		= &match,
+	.checkentry	= &checkentry,
+	.me 		= THIS_MODULE,
+};
+static struct xt_match dccp6_match = 
+{ 
+	.name 		= "dccp",
+	.match		= &match,
+	.checkentry	= &checkentry6,
+	.me 		= THIS_MODULE,
+};
+
+
+static int __init init(void)
+{
+	int ret;
+
+	/* doff is 8 bits, so the maximum option size is (4*256).  Don't put
+	 * this in BSS since DaveM is worried about locked TLB's for kernel
+	 * BSS. */
+	dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL);
+	if (!dccp_optbuf)
+		return -ENOMEM;
+	ret = xt_register_match(AF_INET, &dccp_match);
+	if (ret)
+		goto out_kfree;
+	ret = xt_register_match(AF_INET6, &dccp6_match);
+	if (ret)
+		goto out_unreg;
+
+	return ret;
+
+out_unreg:
+	xt_unregister_match(AF_INET, &dccp_match);
+out_kfree:
+	kfree(dccp_optbuf);
+
+	return ret;
+}
+
+static void __exit fini(void)
+{
+	xt_unregister_match(AF_INET6, &dccp6_match);
+	xt_unregister_match(AF_INET, &dccp_match);
+	kfree(dccp_optbuf);
+}
+
+module_init(init);
+module_exit(fini);