netfilter: split netfilter IPv4 defragmentation into a separate module

Netfilter connection tracking requires all IPv4 packets to be defragmented.
Both the socket match and the TPROXY target depend on this functionality, so
this patch separates the Netfilter IPv4 defrag hooks into a separate module.

Signed-off-by: KOVACS Krisztian <hidden@sch.bme.hu>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 96 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/nf_defrag_ipv4.c b/net/ipv4/netfilter/nf_defrag_ipv4.c
new file mode 100644
index 000000000000..aa2c50a180f7
--- /dev/null
+++ b/net/ipv4/netfilter/nf_defrag_ipv4.c
@@ -0,0 +1,96 @@
+/* (C) 1999-2001 Paul `Rusty' Russell
+ * (C) 2002-2004 Netfilter Core Team <coreteam@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/types.h>
+#include <linux/ip.h>
+#include <linux/netfilter.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <net/route.h>
+#include <net/ip.h>
+
+#include <linux/netfilter_ipv4.h>
+#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
+
+/* Returns new sk_buff, or NULL */
+static int nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
+{
+	int err;
+
+	skb_orphan(skb);
+
+	local_bh_disable();
+	err = ip_defrag(skb, user);
+	local_bh_enable();
+
+	if (!err)
+		ip_send_check(ip_hdr(skb));
+
+	return err;
+}
+
+static unsigned int ipv4_conntrack_defrag(unsigned int hooknum,
+					  struct sk_buff *skb,
+					  const struct net_device *in,
+					  const struct net_device *out,
+					  int (*okfn)(struct sk_buff *))
+{
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+	/* Previously seen (loopback)?  Ignore.  Do this before
+	   fragment check. */
+	if (skb->nfct)
+		return NF_ACCEPT;
+#endif
+
+	/* Gather fragments. */
+	if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) {
+		if (nf_ct_ipv4_gather_frags(skb,
+					    hooknum == NF_INET_PRE_ROUTING ?
+					    IP_DEFRAG_CONNTRACK_IN :
+					    IP_DEFRAG_CONNTRACK_OUT))
+			return NF_STOLEN;
+	}
+	return NF_ACCEPT;
+}
+
+static struct nf_hook_ops ipv4_defrag_ops[] = {
+	{
+		.hook		= ipv4_conntrack_defrag,
+		.owner		= THIS_MODULE,
+		.pf		= PF_INET,
+		.hooknum	= NF_INET_PRE_ROUTING,
+		.priority	= NF_IP_PRI_CONNTRACK_DEFRAG,
+	},
+	{
+		.hook           = ipv4_conntrack_defrag,
+		.owner          = THIS_MODULE,
+		.pf             = PF_INET,
+		.hooknum        = NF_INET_LOCAL_OUT,
+		.priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
+	},
+};
+
+static int __init nf_defrag_init(void)
+{
+	return nf_register_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
+}
+
+static void __exit nf_defrag_fini(void)
+{
+	nf_unregister_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
+}
+
+void nf_defrag_ipv4_enable(void)
+{
+}
+EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);
+
+module_init(nf_defrag_init);
+module_exit(nf_defrag_fini);
+
+MODULE_LICENSE("GPL");