1 files changed, 929 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
new file mode 100644
index 000000000..b3cc416ed
--- /dev/null
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -0,0 +1,929 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Cluster IP hashmark target
+ * (C) 2003-2004 by Harald Welte <laforge@netfilter.org>
+ * based on ideas of Fabio Olive Leite <olive@unixforge.org>
+ *
+ * Development of this code funded by SuSE Linux AG, https://www.suse.com/
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/jhash.h>
+#include <linux/bitops.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <linux/ip.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <linux/icmp.h>
+#include <linux/if_arp.h>
+#include <linux/seq_file.h>
+#include <linux/refcount.h>
+#include <linux/netfilter_arp.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv4/ipt_CLUSTERIP.h>
+#include <net/netfilter/nf_conntrack.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+#include <net/checksum.h>
+#include <net/ip.h>
+
+#define CLUSTERIP_VERSION "0.8"
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
+MODULE_DESCRIPTION("Xtables: CLUSTERIP target");
+
+struct clusterip_config {
+	struct list_head list;			/* list of all configs */
+	refcount_t refcount;			/* reference count */
+	refcount_t entries;			/* number of entries/rules
+						 * referencing us */
+
+	__be32 clusterip;			/* the IP address */
+	u_int8_t clustermac[ETH_ALEN];		/* the MAC address */
+	int ifindex;				/* device ifindex */
+	u_int16_t num_total_nodes;		/* total number of nodes */
+	unsigned long local_nodes;		/* node number array */
+
+#ifdef CONFIG_PROC_FS
+	struct proc_dir_entry *pde;		/* proc dir entry */
+#endif
+	enum clusterip_hashmode hash_mode;	/* which hashing mode */
+	u_int32_t hash_initval;			/* hash initialization */
+	struct rcu_head rcu;			/* for call_rcu */
+	struct net *net;			/* netns for pernet list */
+	char ifname[IFNAMSIZ];			/* device ifname */
+};
+
+#ifdef CONFIG_PROC_FS
+static const struct proc_ops clusterip_proc_ops;
+#endif
+
+struct clusterip_net {
+	struct list_head configs;
+	/* lock protects the configs list */
+	spinlock_t lock;
+
+	bool clusterip_deprecated_warning;
+#ifdef CONFIG_PROC_FS
+	struct proc_dir_entry *procdir;
+	/* mutex protects the config->pde*/
+	struct mutex mutex;
+#endif
+	unsigned int hook_users;
+};
+
+static unsigned int clusterip_arp_mangle(void *priv, struct sk_buff *skb, const struct nf_hook_state *state);
+
+static const struct nf_hook_ops cip_arp_ops = {
+	.hook = clusterip_arp_mangle,
+	.pf = NFPROTO_ARP,
+	.hooknum = NF_ARP_OUT,
+	.priority = -1
+};
+
+static unsigned int clusterip_net_id __read_mostly;
+static inline struct clusterip_net *clusterip_pernet(struct net *net)
+{
+	return net_generic(net, clusterip_net_id);
+}
+
+static inline void
+clusterip_config_get(struct clusterip_config *c)
+{
+	refcount_inc(&c->refcount);
+}
+
+static void clusterip_config_rcu_free(struct rcu_head *head)
+{
+	struct clusterip_config *config;
+	struct net_device *dev;
+
+	config = container_of(head, struct clusterip_config, rcu);
+	dev = dev_get_by_name(config->net, config->ifname);
+	if (dev) {
+		dev_mc_del(dev, config->clustermac);
+		dev_put(dev);
+	}
+	kfree(config);
+}
+
+static inline void
+clusterip_config_put(struct clusterip_config *c)
+{
+	if (refcount_dec_and_test(&c->refcount))
+		call_rcu(&c->rcu, clusterip_config_rcu_free);
+}
+
+/* decrease the count of entries using/referencing this config.  If last
+ * entry(rule) is removed, remove the config from lists, but don't free it
+ * yet, since proc-files could still be holding references */
+static inline void
+clusterip_config_entry_put(struct clusterip_config *c)
+{
+	struct clusterip_net *cn = clusterip_pernet(c->net);
+
+	local_bh_disable();
+	if (refcount_dec_and_lock(&c->entries, &cn->lock)) {
+		list_del_rcu(&c->list);
+		spin_unlock(&cn->lock);
+		local_bh_enable();
+		/* In case anyone still accesses the file, the open/close
+		 * functions are also incrementing the refcount on their own,
+		 * so it's safe to remove the entry even if it's in use. */
+#ifdef CONFIG_PROC_FS
+		mutex_lock(&cn->mutex);
+		if (cn->procdir)
+			proc_remove(c->pde);
+		mutex_unlock(&cn->mutex);
+#endif
+		return;
+	}
+	local_bh_enable();
+}
+
+static struct clusterip_config *
+__clusterip_config_find(struct net *net, __be32 clusterip)
+{
+	struct clusterip_config *c;
+	struct clusterip_net *cn = clusterip_pernet(net);
+
+	list_for_each_entry_rcu(c, &cn->configs, list) {
+		if (c->clusterip == clusterip)
+			return c;
+	}
+
+	return NULL;
+}
+
+static inline struct clusterip_config *
+clusterip_config_find_get(struct net *net, __be32 clusterip, int entry)
+{
+	struct clusterip_config *c;
+
+	rcu_read_lock_bh();
+	c = __clusterip_config_find(net, clusterip);
+	if (c) {
+#ifdef CONFIG_PROC_FS
+		if (!c->pde)
+			c = NULL;
+		else
+#endif
+		if (unlikely(!refcount_inc_not_zero(&c->refcount)))
+			c = NULL;
+		else if (entry) {
+			if (unlikely(!refcount_inc_not_zero(&c->entries))) {
+				clusterip_config_put(c);
+				c = NULL;
+			}
+		}
+	}
+	rcu_read_unlock_bh();
+
+	return c;
+}
+
+static void
+clusterip_config_init_nodelist(struct clusterip_config *c,
+			       const struct ipt_clusterip_tgt_info *i)
+{
+	int n;
+
+	for (n = 0; n < i->num_local_nodes; n++)
+		set_bit(i->local_nodes[n] - 1, &c->local_nodes);
+}
+
+static int
+clusterip_netdev_event(struct notifier_block *this, unsigned long event,
+		       void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct net *net = dev_net(dev);
+	struct clusterip_net *cn = clusterip_pernet(net);
+	struct clusterip_config *c;
+
+	spin_lock_bh(&cn->lock);
+	list_for_each_entry_rcu(c, &cn->configs, list) {
+		switch (event) {
+		case NETDEV_REGISTER:
+			if (!strcmp(dev->name, c->ifname)) {
+				c->ifindex = dev->ifindex;
+				dev_mc_add(dev, c->clustermac);
+			}
+			break;
+		case NETDEV_UNREGISTER:
+			if (dev->ifindex == c->ifindex) {
+				dev_mc_del(dev, c->clustermac);
+				c->ifindex = -1;
+			}
+			break;
+		case NETDEV_CHANGENAME:
+			if (!strcmp(dev->name, c->ifname)) {
+				c->ifindex = dev->ifindex;
+				dev_mc_add(dev, c->clustermac);
+			} else if (dev->ifindex == c->ifindex) {
+				dev_mc_del(dev, c->clustermac);
+				c->ifindex = -1;
+			}
+			break;
+		}
+	}
+	spin_unlock_bh(&cn->lock);
+
+	return NOTIFY_DONE;
+}
+
+static struct clusterip_config *
+clusterip_config_init(struct net *net, const struct ipt_clusterip_tgt_info *i,
+		      __be32 ip, const char *iniface)
+{
+	struct clusterip_net *cn = clusterip_pernet(net);
+	struct clusterip_config *c;
+	struct net_device *dev;
+	int err;
+
+	if (iniface[0] == '\0') {
+		pr_info("Please specify an interface name\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	c = kzalloc(sizeof(*c), GFP_ATOMIC);
+	if (!c)
+		return ERR_PTR(-ENOMEM);
+
+	dev = dev_get_by_name(net, iniface);
+	if (!dev) {
+		pr_info("no such interface %s\n", iniface);
+		kfree(c);
+		return ERR_PTR(-ENOENT);
+	}
+	c->ifindex = dev->ifindex;
+	strcpy(c->ifname, dev->name);
+	memcpy(&c->clustermac, &i->clustermac, ETH_ALEN);
+	dev_mc_add(dev, c->clustermac);
+	dev_put(dev);
+
+	c->clusterip = ip;
+	c->num_total_nodes = i->num_total_nodes;
+	clusterip_config_init_nodelist(c, i);
+	c->hash_mode = i->hash_mode;
+	c->hash_initval = i->hash_initval;
+	c->net = net;
+	refcount_set(&c->refcount, 1);
+
+	spin_lock_bh(&cn->lock);
+	if (__clusterip_config_find(net, ip)) {
+		err = -EBUSY;
+		goto out_config_put;
+	}
+
+	list_add_rcu(&c->list, &cn->configs);
+	spin_unlock_bh(&cn->lock);
+
+#ifdef CONFIG_PROC_FS
+	{
+		char buffer[16];
+
+		/* create proc dir entry */
+		sprintf(buffer, "%pI4", &ip);
+		mutex_lock(&cn->mutex);
+		c->pde = proc_create_data(buffer, 0600,
+					  cn->procdir,
+					  &clusterip_proc_ops, c);
+		mutex_unlock(&cn->mutex);
+		if (!c->pde) {
+			err = -ENOMEM;
+			goto err;
+		}
+	}
+#endif
+
+	refcount_set(&c->entries, 1);
+	return c;
+
+#ifdef CONFIG_PROC_FS
+err:
+#endif
+	spin_lock_bh(&cn->lock);
+	list_del_rcu(&c->list);
+out_config_put:
+	spin_unlock_bh(&cn->lock);
+	clusterip_config_put(c);
+	return ERR_PTR(err);
+}
+
+#ifdef CONFIG_PROC_FS
+static int
+clusterip_add_node(struct clusterip_config *c, u_int16_t nodenum)
+{
+
+	if (nodenum == 0 ||
+	    nodenum > c->num_total_nodes)
+		return 1;
+
+	/* check if we already have this number in our bitfield */
+	if (test_and_set_bit(nodenum - 1, &c->local_nodes))
+		return 1;
+
+	return 0;
+}
+
+static bool
+clusterip_del_node(struct clusterip_config *c, u_int16_t nodenum)
+{
+	if (nodenum == 0 ||
+	    nodenum > c->num_total_nodes)
+		return true;
+
+	if (test_and_clear_bit(nodenum - 1, &c->local_nodes))
+		return false;
+
+	return true;
+}
+#endif
+
+static inline u_int32_t
+clusterip_hashfn(const struct sk_buff *skb,
+		 const struct clusterip_config *config)
+{
+	const struct iphdr *iph = ip_hdr(skb);
+	unsigned long hashval;
+	u_int16_t sport = 0, dport = 0;
+	int poff;
+
+	poff = proto_ports_offset(iph->protocol);
+	if (poff >= 0) {
+		const u_int16_t *ports;
+		u16 _ports[2];
+
+		ports = skb_header_pointer(skb, iph->ihl * 4 + poff, 4, _ports);
+		if (ports) {
+			sport = ports[0];
+			dport = ports[1];
+		}
+	} else {
+		net_info_ratelimited("unknown protocol %u\n", iph->protocol);
+	}
+
+	switch (config->hash_mode) {
+	case CLUSTERIP_HASHMODE_SIP:
+		hashval = jhash_1word(ntohl(iph->saddr),
+				      config->hash_initval);
+		break;
+	case CLUSTERIP_HASHMODE_SIP_SPT:
+		hashval = jhash_2words(ntohl(iph->saddr), sport,
+				       config->hash_initval);
+		break;
+	case CLUSTERIP_HASHMODE_SIP_SPT_DPT:
+		hashval = jhash_3words(ntohl(iph->saddr), sport, dport,
+				       config->hash_initval);
+		break;
+	default:
+		/* to make gcc happy */
+		hashval = 0;
+		/* This cannot happen, unless the check function wasn't called
+		 * at rule load time */
+		pr_info("unknown mode %u\n", config->hash_mode);
+		BUG();
+		break;
+	}
+
+	/* node numbers are 1..n, not 0..n */
+	return reciprocal_scale(hashval, config->num_total_nodes) + 1;
+}
+
+static inline int
+clusterip_responsible(const struct clusterip_config *config, u_int32_t hash)
+{
+	return test_bit(hash - 1, &config->local_nodes);
+}
+
+/***********************************************************************
+ * IPTABLES TARGET
+ ***********************************************************************/
+
+static unsigned int
+clusterip_tg(struct sk_buff *skb, const struct xt_action_param *par)
+{
+	const struct ipt_clusterip_tgt_info *cipinfo = par->targinfo;
+	struct nf_conn *ct;
+	enum ip_conntrack_info ctinfo;
+	u_int32_t hash;
+
+	/* don't need to clusterip_config_get() here, since refcount
+	 * is only decremented by destroy() - and ip_tables guarantees
+	 * that the ->target() function isn't called after ->destroy() */
+
+	ct = nf_ct_get(skb, &ctinfo);
+	if (ct == NULL)
+		return NF_DROP;
+
+	/* special case: ICMP error handling. conntrack distinguishes between
+	 * error messages (RELATED) and information requests (see below) */
+	if (ip_hdr(skb)->protocol == IPPROTO_ICMP &&
+	    (ctinfo == IP_CT_RELATED ||
+	     ctinfo == IP_CT_RELATED_REPLY))
+		return XT_CONTINUE;
+
+	/* nf_conntrack_proto_icmp guarantees us that we only have ICMP_ECHO,
+	 * TIMESTAMP, INFO_REQUEST or ICMP_ADDRESS type icmp packets from here
+	 * on, which all have an ID field [relevant for hashing]. */
+
+	hash = clusterip_hashfn(skb, cipinfo->config);
+
+	switch (ctinfo) {
+	case IP_CT_NEW:
+		WRITE_ONCE(ct->mark, hash);
+		break;
+	case IP_CT_RELATED:
+	case IP_CT_RELATED_REPLY:
+		/* FIXME: we don't handle expectations at the moment.
+		 * They can arrive on a different node than
+		 * the master connection (e.g. FTP passive mode) */
+	case IP_CT_ESTABLISHED:
+	case IP_CT_ESTABLISHED_REPLY:
+		break;
+	default:			/* Prevent gcc warnings */
+		break;
+	}
+
+#ifdef DEBUG
+	nf_ct_dump_tuple_ip(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
+#endif
+	pr_debug("hash=%u ct_hash=%u ", hash, READ_ONCE(ct->mark));
+	if (!clusterip_responsible(cipinfo->config, hash)) {
+		pr_debug("not responsible\n");
+		return NF_DROP;
+	}
+	pr_debug("responsible\n");
+
+	/* despite being received via linklayer multicast, this is
+	 * actually a unicast IP packet. TCP doesn't like PACKET_MULTICAST */
+	skb->pkt_type = PACKET_HOST;
+
+	return XT_CONTINUE;
+}
+
+static int clusterip_tg_check(const struct xt_tgchk_param *par)
+{
+	struct ipt_clusterip_tgt_info *cipinfo = par->targinfo;
+	struct clusterip_net *cn = clusterip_pernet(par->net);
+	const struct ipt_entry *e = par->entryinfo;
+	struct clusterip_config *config;
+	int ret, i;
+
+	if (par->nft_compat) {
+		pr_err("cannot use CLUSTERIP target from nftables compat\n");
+		return -EOPNOTSUPP;
+	}
+
+	if (cn->hook_users == UINT_MAX)
+		return -EOVERFLOW;
+
+	if (cipinfo->hash_mode != CLUSTERIP_HASHMODE_SIP &&
+	    cipinfo->hash_mode != CLUSTERIP_HASHMODE_SIP_SPT &&
+	    cipinfo->hash_mode != CLUSTERIP_HASHMODE_SIP_SPT_DPT) {
+		pr_info("unknown mode %u\n", cipinfo->hash_mode);
+		return -EINVAL;
+
+	}
+	if (e->ip.dmsk.s_addr != htonl(0xffffffff) ||
+	    e->ip.dst.s_addr == 0) {
+		pr_info("Please specify destination IP\n");
+		return -EINVAL;
+	}
+	if (cipinfo->num_local_nodes > ARRAY_SIZE(cipinfo->local_nodes)) {
+		pr_info("bad num_local_nodes %u\n", cipinfo->num_local_nodes);
+		return -EINVAL;
+	}
+	for (i = 0; i < cipinfo->num_local_nodes; i++) {
+		if (cipinfo->local_nodes[i] - 1 >=
+		    sizeof(config->local_nodes) * 8) {
+			pr_info("bad local_nodes[%d] %u\n",
+				i, cipinfo->local_nodes[i]);
+			return -EINVAL;
+		}
+	}
+
+	config = clusterip_config_find_get(par->net, e->ip.dst.s_addr, 1);
+	if (!config) {
+		if (!(cipinfo->flags & CLUSTERIP_FLAG_NEW)) {
+			pr_info("no config found for %pI4, need 'new'\n",
+				&e->ip.dst.s_addr);
+			return -EINVAL;
+		} else {
+			config = clusterip_config_init(par->net, cipinfo,
+						       e->ip.dst.s_addr,
+						       e->ip.iniface);
+			if (IS_ERR(config))
+				return PTR_ERR(config);
+		}
+	} else if (memcmp(&config->clustermac, &cipinfo->clustermac, ETH_ALEN)) {
+		clusterip_config_entry_put(config);
+		clusterip_config_put(config);
+		return -EINVAL;
+	}
+
+	ret = nf_ct_netns_get(par->net, par->family);
+	if (ret < 0) {
+		pr_info("cannot load conntrack support for proto=%u\n",
+			par->family);
+		clusterip_config_entry_put(config);
+		clusterip_config_put(config);
+		return ret;
+	}
+
+	if (cn->hook_users == 0) {
+		ret = nf_register_net_hook(par->net, &cip_arp_ops);
+
+		if (ret < 0) {
+			clusterip_config_entry_put(config);
+			clusterip_config_put(config);
+			nf_ct_netns_put(par->net, par->family);
+			return ret;
+		}
+	}
+
+	cn->hook_users++;
+
+	if (!cn->clusterip_deprecated_warning) {
+		pr_info("ipt_CLUSTERIP is deprecated and it will removed soon, "
+			"use xt_cluster instead\n");
+		cn->clusterip_deprecated_warning = true;
+	}
+
+	cipinfo->config = config;
+	return ret;
+}
+
+/* drop reference count of cluster config when rule is deleted */
+static void clusterip_tg_destroy(const struct xt_tgdtor_param *par)
+{
+	const struct ipt_clusterip_tgt_info *cipinfo = par->targinfo;
+	struct clusterip_net *cn = clusterip_pernet(par->net);
+
+	/* if no more entries are referencing the config, remove it
+	 * from the list and destroy the proc entry */
+	clusterip_config_entry_put(cipinfo->config);
+
+	clusterip_config_put(cipinfo->config);
+
+	nf_ct_netns_put(par->net, par->family);
+	cn->hook_users--;
+
+	if (cn->hook_users == 0)
+		nf_unregister_net_hook(par->net, &cip_arp_ops);
+}
+
+#ifdef CONFIG_NETFILTER_XTABLES_COMPAT
+struct compat_ipt_clusterip_tgt_info
+{
+	u_int32_t	flags;
+	u_int8_t	clustermac[6];
+	u_int16_t	num_total_nodes;
+	u_int16_t	num_local_nodes;
+	u_int16_t	local_nodes[CLUSTERIP_MAX_NODES];
+	u_int32_t	hash_mode;
+	u_int32_t	hash_initval;
+	compat_uptr_t	config;
+};
+#endif /* CONFIG_NETFILTER_XTABLES_COMPAT */
+
+static struct xt_target clusterip_tg_reg __read_mostly = {
+	.name		= "CLUSTERIP",
+	.family		= NFPROTO_IPV4,
+	.target		= clusterip_tg,
+	.checkentry	= clusterip_tg_check,
+	.destroy	= clusterip_tg_destroy,
+	.targetsize	= sizeof(struct ipt_clusterip_tgt_info),
+	.usersize	= offsetof(struct ipt_clusterip_tgt_info, config),
+#ifdef CONFIG_NETFILTER_XTABLES_COMPAT
+	.compatsize	= sizeof(struct compat_ipt_clusterip_tgt_info),
+#endif /* CONFIG_NETFILTER_XTABLES_COMPAT */
+	.me		= THIS_MODULE
+};
+
+
+/***********************************************************************
+ * ARP MANGLING CODE
+ ***********************************************************************/
+
+/* hardcoded for 48bit ethernet and 32bit ipv4 addresses */
+struct arp_payload {
+	u_int8_t src_hw[ETH_ALEN];
+	__be32 src_ip;
+	u_int8_t dst_hw[ETH_ALEN];
+	__be32 dst_ip;
+} __packed;
+
+#ifdef DEBUG
+static void arp_print(struct arp_payload *payload)
+{
+#define HBUFFERLEN 30
+	char hbuffer[HBUFFERLEN];
+	int j, k;
+
+	for (k = 0, j = 0; k < HBUFFERLEN - 3 && j < ETH_ALEN; j++) {
+		hbuffer[k++] = hex_asc_hi(payload->src_hw[j]);
+		hbuffer[k++] = hex_asc_lo(payload->src_hw[j]);
+		hbuffer[k++] = ':';
+	}
+	hbuffer[--k] = '\0';
+
+	pr_debug("src %pI4@%s, dst %pI4\n",
+		 &payload->src_ip, hbuffer, &payload->dst_ip);
+}
+#endif
+
+static unsigned int
+clusterip_arp_mangle(void *priv, struct sk_buff *skb,
+		     const struct nf_hook_state *state)
+{
+	struct arphdr *arp = arp_hdr(skb);
+	struct arp_payload *payload;
+	struct clusterip_config *c;
+	struct net *net = state->net;
+
+	/* we don't care about non-ethernet and non-ipv4 ARP */
+	if (arp->ar_hrd != htons(ARPHRD_ETHER) ||
+	    arp->ar_pro != htons(ETH_P_IP) ||
+	    arp->ar_pln != 4 || arp->ar_hln != ETH_ALEN)
+		return NF_ACCEPT;
+
+	/* we only want to mangle arp requests and replies */
+	if (arp->ar_op != htons(ARPOP_REPLY) &&
+	    arp->ar_op != htons(ARPOP_REQUEST))
+		return NF_ACCEPT;
+
+	payload = (void *)(arp+1);
+
+	/* if there is no clusterip configuration for the arp reply's
+	 * source ip, we don't want to mangle it */
+	c = clusterip_config_find_get(net, payload->src_ip, 0);
+	if (!c)
+		return NF_ACCEPT;
+
+	/* normally the linux kernel always replies to arp queries of
+	 * addresses on different interfacs.  However, in the CLUSTERIP case
+	 * this wouldn't work, since we didn't subscribe the mcast group on
+	 * other interfaces */
+	if (c->ifindex != state->out->ifindex) {
+		pr_debug("not mangling arp reply on different interface: cip'%d'-skb'%d'\n",
+			 c->ifindex, state->out->ifindex);
+		clusterip_config_put(c);
+		return NF_ACCEPT;
+	}
+
+	/* mangle reply hardware address */
+	memcpy(payload->src_hw, c->clustermac, arp->ar_hln);
+
+#ifdef DEBUG
+	pr_debug("mangled arp reply: ");
+	arp_print(payload);
+#endif
+
+	clusterip_config_put(c);
+
+	return NF_ACCEPT;
+}
+
+/***********************************************************************
+ * PROC DIR HANDLING
+ ***********************************************************************/
+
+#ifdef CONFIG_PROC_FS
+
+struct clusterip_seq_position {
+	unsigned int pos;	/* position */
+	unsigned int weight;	/* number of bits set == size */
+	unsigned int bit;	/* current bit */
+	unsigned long val;	/* current value */
+};
+
+static void *clusterip_seq_start(struct seq_file *s, loff_t *pos)
+{
+	struct clusterip_config *c = s->private;
+	unsigned int weight;
+	u_int32_t local_nodes;
+	struct clusterip_seq_position *idx;
+
+	/* FIXME: possible race */
+	local_nodes = c->local_nodes;
+	weight = hweight32(local_nodes);
+	if (*pos >= weight)
+		return NULL;
+
+	idx = kmalloc(sizeof(struct clusterip_seq_position), GFP_KERNEL);
+	if (!idx)
+		return ERR_PTR(-ENOMEM);
+
+	idx->pos = *pos;
+	idx->weight = weight;
+	idx->bit = ffs(local_nodes);
+	idx->val = local_nodes;
+	clear_bit(idx->bit - 1, &idx->val);
+
+	return idx;
+}
+
+static void *clusterip_seq_next(struct seq_file *s, void *v, loff_t *pos)
+{
+	struct clusterip_seq_position *idx = v;
+
+	*pos = ++idx->pos;
+	if (*pos >= idx->weight) {
+		kfree(v);
+		return NULL;
+	}
+	idx->bit = ffs(idx->val);
+	clear_bit(idx->bit - 1, &idx->val);
+	return idx;
+}
+
+static void clusterip_seq_stop(struct seq_file *s, void *v)
+{
+	if (!IS_ERR(v))
+		kfree(v);
+}
+
+static int clusterip_seq_show(struct seq_file *s, void *v)
+{
+	struct clusterip_seq_position *idx = v;
+
+	if (idx->pos != 0)
+		seq_putc(s, ',');
+
+	seq_printf(s, "%u", idx->bit);
+
+	if (idx->pos == idx->weight - 1)
+		seq_putc(s, '\n');
+
+	return 0;
+}
+
+static const struct seq_operations clusterip_seq_ops = {
+	.start	= clusterip_seq_start,
+	.next	= clusterip_seq_next,
+	.stop	= clusterip_seq_stop,
+	.show	= clusterip_seq_show,
+};
+
+static int clusterip_proc_open(struct inode *inode, struct file *file)
+{
+	int ret = seq_open(file, &clusterip_seq_ops);
+
+	if (!ret) {
+		struct seq_file *sf = file->private_data;
+		struct clusterip_config *c = pde_data(inode);
+
+		sf->private = c;
+
+		clusterip_config_get(c);
+	}
+
+	return ret;
+}
+
+static int clusterip_proc_release(struct inode *inode, struct file *file)
+{
+	struct clusterip_config *c = pde_data(inode);
+	int ret;
+
+	ret = seq_release(inode, file);
+
+	if (!ret)
+		clusterip_config_put(c);
+
+	return ret;
+}
+
+static ssize_t clusterip_proc_write(struct file *file, const char __user *input,
+				size_t size, loff_t *ofs)
+{
+	struct clusterip_config *c = pde_data(file_inode(file));
+#define PROC_WRITELEN	10
+	char buffer[PROC_WRITELEN+1];
+	unsigned long nodenum;
+	int rc;
+
+	if (size > PROC_WRITELEN)
+		return -EIO;
+	if (copy_from_user(buffer, input, size))
+		return -EFAULT;
+	buffer[size] = 0;
+
+	if (*buffer == '+') {
+		rc = kstrtoul(buffer+1, 10, &nodenum);
+		if (rc)
+			return rc;
+		if (clusterip_add_node(c, nodenum))
+			return -ENOMEM;
+	} else if (*buffer == '-') {
+		rc = kstrtoul(buffer+1, 10, &nodenum);
+		if (rc)
+			return rc;
+		if (clusterip_del_node(c, nodenum))
+			return -ENOENT;
+	} else
+		return -EIO;
+
+	return size;
+}
+
+static const struct proc_ops clusterip_proc_ops = {
+	.proc_open	= clusterip_proc_open,
+	.proc_read	= seq_read,
+	.proc_write	= clusterip_proc_write,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= clusterip_proc_release,
+};
+
+#endif /* CONFIG_PROC_FS */
+
+static int clusterip_net_init(struct net *net)
+{
+	struct clusterip_net *cn = clusterip_pernet(net);
+
+	INIT_LIST_HEAD(&cn->configs);
+
+	spin_lock_init(&cn->lock);
+
+#ifdef CONFIG_PROC_FS
+	cn->procdir = proc_mkdir("ipt_CLUSTERIP", net->proc_net);
+	if (!cn->procdir) {
+		pr_err("Unable to proc dir entry\n");
+		return -ENOMEM;
+	}
+	mutex_init(&cn->mutex);
+#endif /* CONFIG_PROC_FS */
+
+	return 0;
+}
+
+static void clusterip_net_exit(struct net *net)
+{
+#ifdef CONFIG_PROC_FS
+	struct clusterip_net *cn = clusterip_pernet(net);
+
+	mutex_lock(&cn->mutex);
+	proc_remove(cn->procdir);
+	cn->procdir = NULL;
+	mutex_unlock(&cn->mutex);
+#endif
+}
+
+static struct pernet_operations clusterip_net_ops = {
+	.init = clusterip_net_init,
+	.exit = clusterip_net_exit,
+	.id   = &clusterip_net_id,
+	.size = sizeof(struct clusterip_net),
+};
+
+static struct notifier_block cip_netdev_notifier = {
+	.notifier_call = clusterip_netdev_event
+};
+
+static int __init clusterip_tg_init(void)
+{
+	int ret;
+
+	ret = register_pernet_subsys(&clusterip_net_ops);
+	if (ret < 0)
+		return ret;
+
+	ret = xt_register_target(&clusterip_tg_reg);
+	if (ret < 0)
+		goto cleanup_subsys;
+
+	ret = register_netdevice_notifier(&cip_netdev_notifier);
+	if (ret < 0)
+		goto unregister_target;
+
+	pr_info("ClusterIP Version %s loaded successfully\n",
+		CLUSTERIP_VERSION);
+
+	return 0;
+
+unregister_target:
+	xt_unregister_target(&clusterip_tg_reg);
+cleanup_subsys:
+	unregister_pernet_subsys(&clusterip_net_ops);
+	return ret;
+}
+
+static void __exit clusterip_tg_exit(void)
+{
+	pr_info("ClusterIP Version %s unloading\n", CLUSTERIP_VERSION);
+
+	unregister_netdevice_notifier(&cip_netdev_notifier);
+	xt_unregister_target(&clusterip_tg_reg);
+	unregister_pernet_subsys(&clusterip_net_ops);
+
+	/* Wait for completion of call_rcu()'s (clusterip_config_rcu_free) */
+	rcu_barrier();
+}
+
+module_init(clusterip_tg_init);
+module_exit(clusterip_tg_exit);