net/netfilter/nfnetlink_cthelper.c - linux - Git at Google

 /*
  * (C) 2012 Pablo Neira Ayuso <pablo@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 (or any later at your option).
  *
  * This software has been sponsored by Vyatta Inc. <http://www.vyatta.com>
  */
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/skbuff.h>
 #include <linux/netlink.h>
 #include <linux/rculist.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/list.h>
 #include <linux/errno.h>
 #include <net/netlink.h>
 #include <net/sock.h>

 #include <net/netfilter/nf_conntrack_helper.h>
 #include <net/netfilter/nf_conntrack_expect.h>
 #include <net/netfilter/nf_conntrack_ecache.h>

 #include <linux/netfilter/nfnetlink.h>
 #include <linux/netfilter/nfnetlink_conntrack.h>
 #include <linux/netfilter/nfnetlink_cthelper.h>

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
 MODULE_DESCRIPTION("nfnl_cthelper: User-space connection tracking helpers");

 static int
 nfnl_userspace_cthelper(struct sk_buff *skb, unsigned int protoff,
 			struct nf_conn *ct, enum ip_conntrack_info ctinfo)
 {
 	const struct nf_conn_help *help;
 	struct nf_conntrack_helper *helper;

 	help = nfct_help(ct);
 	if (help == NULL)
 		return NF_DROP;

 	/* rcu_read_lock()ed by nf_hook_slow */
 	helper = rcu_dereference(help->helper);
 	if (helper == NULL)
 		return NF_DROP;

 	/* This is an user-space helper not yet configured, skip. */
 	if ((helper->flags &
 	    (NF_CT_HELPER_F_USERSPACE | NF_CT_HELPER_F_CONFIGURED)) ==
 	     NF_CT_HELPER_F_USERSPACE)
 		return NF_ACCEPT;

 	/* If the user-space helper is not available, don't block traffic. */
 	return NF_QUEUE_NR(helper->queue_num) | NF_VERDICT_FLAG_QUEUE_BYPASS;
 }

 static const struct nla_policy nfnl_cthelper_tuple_pol[NFCTH_TUPLE_MAX+1] = {
 	[NFCTH_TUPLE_L3PROTONUM] = { .type = NLA_U16, },
 	[NFCTH_TUPLE_L4PROTONUM] = { .type = NLA_U8, },
 };

 static int
 nfnl_cthelper_parse_tuple(struct nf_conntrack_tuple *tuple,
 			  const struct nlattr *attr)
 {
 	int err;
 	struct nlattr *tb[NFCTH_TUPLE_MAX+1];

 	err = nla_parse_nested(tb, NFCTH_TUPLE_MAX, attr, nfnl_cthelper_tuple_pol);
 	if (err < 0)
 		return err;

 	if (!tb[NFCTH_TUPLE_L3PROTONUM] || !tb[NFCTH_TUPLE_L4PROTONUM])
 		return -EINVAL;

 	tuple->src.l3num = ntohs(nla_get_be16(tb[NFCTH_TUPLE_L3PROTONUM]));
 	tuple->dst.protonum = nla_get_u8(tb[NFCTH_TUPLE_L4PROTONUM]);

 	return 0;
 }

 static int
 nfnl_cthelper_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
 {
 	const struct nf_conn_help *help = nfct_help(ct);

 	if (attr == NULL)
 		return -EINVAL;

 	if (help->helper->data_len == 0)
 		return -EINVAL;

 	memcpy(&help->data, nla_data(attr), help->helper->data_len);
 	return 0;
 }

 static int
 nfnl_cthelper_to_nlattr(struct sk_buff *skb, const struct nf_conn *ct)
 {
 	const struct nf_conn_help *help = nfct_help(ct);

 	if (help->helper->data_len &&
 	    nla_put(skb, CTA_HELP_INFO, help->helper->data_len, &help->data))
 		goto nla_put_failure;

 	return 0;

 nla_put_failure:
 	return -ENOSPC;
 }

 static const struct nla_policy nfnl_cthelper_expect_pol[NFCTH_POLICY_MAX+1] = {
 	[NFCTH_POLICY_NAME] = { .type = NLA_NUL_STRING,
 				.len = NF_CT_HELPER_NAME_LEN-1 },
 	[NFCTH_POLICY_EXPECT_MAX] = { .type = NLA_U32, },
 	[NFCTH_POLICY_EXPECT_TIMEOUT] = { .type = NLA_U32, },
 };

 static int
 nfnl_cthelper_expect_policy(struct nf_conntrack_expect_policy *expect_policy,
 			    const struct nlattr *attr)
 {
 	int err;
 	struct nlattr *tb[NFCTH_POLICY_MAX+1];

 	err = nla_parse_nested(tb, NFCTH_POLICY_MAX, attr, nfnl_cthelper_expect_pol);
 	if (err < 0)
 		return err;

 	if (!tb[NFCTH_POLICY_NAME] ||
 	    !tb[NFCTH_POLICY_EXPECT_MAX] ||
 	    !tb[NFCTH_POLICY_EXPECT_TIMEOUT])
 		return -EINVAL;

 	strncpy(expect_policy->name,
 		nla_data(tb[NFCTH_POLICY_NAME]), NF_CT_HELPER_NAME_LEN);
 	expect_policy->max_expected =
 		ntohl(nla_get_be32(tb[NFCTH_POLICY_EXPECT_MAX]));
 	expect_policy->timeout =
 		ntohl(nla_get_be32(tb[NFCTH_POLICY_EXPECT_TIMEOUT]));

 	return 0;
 }

 static const struct nla_policy
 nfnl_cthelper_expect_policy_set[NFCTH_POLICY_SET_MAX+1] = {
 	[NFCTH_POLICY_SET_NUM] = { .type = NLA_U32, },
 };

 static int
 nfnl_cthelper_parse_expect_policy(struct nf_conntrack_helper *helper,
 				  const struct nlattr *attr)
 {
 	int i, ret;
 	struct nf_conntrack_expect_policy *expect_policy;
 	struct nlattr *tb[NFCTH_POLICY_SET_MAX+1];

 	ret = nla_parse_nested(tb, NFCTH_POLICY_SET_MAX, attr,
 			       nfnl_cthelper_expect_policy_set);
 	if (ret < 0)
 		return ret;

 	if (!tb[NFCTH_POLICY_SET_NUM])
 		return -EINVAL;

 	helper->expect_class_max =
 		ntohl(nla_get_be32(tb[NFCTH_POLICY_SET_NUM]));

 	if (helper->expect_class_max != 0 &&
 	    helper->expect_class_max > NF_CT_MAX_EXPECT_CLASSES)
 		return -EOVERFLOW;

 	expect_policy = kzalloc(sizeof(struct nf_conntrack_expect_policy) *
 				helper->expect_class_max, GFP_KERNEL);
 	if (expect_policy == NULL)
 		return -ENOMEM;

 	for (i=0; i<helper->expect_class_max; i++) {
 		if (!tb[NFCTH_POLICY_SET+i])
 			goto err;

 		ret = nfnl_cthelper_expect_policy(&expect_policy[i],
 						  tb[NFCTH_POLICY_SET+i]);
 		if (ret < 0)
 			goto err;
 	}
 	helper->expect_policy = expect_policy;
 	return 0;
 err:
 	kfree(expect_policy);
 	return -EINVAL;
 }

 static int
 nfnl_cthelper_create(const struct nlattr * const tb[],
 		     struct nf_conntrack_tuple *tuple)
 {
 	struct nf_conntrack_helper *helper;
 	int ret;

 	if (!tb[NFCTH_TUPLE] || !tb[NFCTH_POLICY] || !tb[NFCTH_PRIV_DATA_LEN])
 		return -EINVAL;

 	helper = kzalloc(sizeof(struct nf_conntrack_helper), GFP_KERNEL);
 	if (helper == NULL)
 		return -ENOMEM;

 	ret = nfnl_cthelper_parse_expect_policy(helper, tb[NFCTH_POLICY]);
 	if (ret < 0)
 		goto err;

 	strncpy(helper->name, nla_data(tb[NFCTH_NAME]), NF_CT_HELPER_NAME_LEN);
 	helper->data_len = ntohl(nla_get_be32(tb[NFCTH_PRIV_DATA_LEN]));
 	helper->flags |= NF_CT_HELPER_F_USERSPACE;
 	memcpy(&helper->tuple, tuple, sizeof(struct nf_conntrack_tuple));

 	helper->me = THIS_MODULE;
 	helper->help = nfnl_userspace_cthelper;
 	helper->from_nlattr = nfnl_cthelper_from_nlattr;
 	helper->to_nlattr = nfnl_cthelper_to_nlattr;

 	/* Default to queue number zero, this can be updated at any time. */
 	if (tb[NFCTH_QUEUE_NUM])
 		helper->queue_num = ntohl(nla_get_be32(tb[NFCTH_QUEUE_NUM]));

 	if (tb[NFCTH_STATUS]) {
 		int status = ntohl(nla_get_be32(tb[NFCTH_STATUS]));

 		switch(status) {
 		case NFCT_HELPER_STATUS_ENABLED:
 			helper->flags |= NF_CT_HELPER_F_CONFIGURED;
 			break;
 		case NFCT_HELPER_STATUS_DISABLED:
 			helper->flags &= ~NF_CT_HELPER_F_CONFIGURED;
 			break;
 		}
 	}

 	ret = nf_conntrack_helper_register(helper);
 	if (ret < 0)
 		goto err;

 	return 0;
 err:
 	kfree(helper);
 	return ret;
 }

 static int
 nfnl_cthelper_update(const struct nlattr * const tb[],
 		     struct nf_conntrack_helper *helper)
 {
 	int ret;

 	if (tb[NFCTH_PRIV_DATA_LEN])
 		return -EBUSY;

 	if (tb[NFCTH_POLICY]) {
 		ret = nfnl_cthelper_parse_expect_policy(helper,
 							tb[NFCTH_POLICY]);
 		if (ret < 0)
 			return ret;
 	}
 	if (tb[NFCTH_QUEUE_NUM])
 		helper->queue_num = ntohl(nla_get_be32(tb[NFCTH_QUEUE_NUM]));

 	if (tb[NFCTH_STATUS]) {
 		int status = ntohl(nla_get_be32(tb[NFCTH_STATUS]));

 		switch(status) {
 		case NFCT_HELPER_STATUS_ENABLED:
 			helper->flags |= NF_CT_HELPER_F_CONFIGURED;
 			break;
 		case NFCT_HELPER_STATUS_DISABLED:
 			helper->flags &= ~NF_CT_HELPER_F_CONFIGURED;
 			break;
 		}
 	}
 	return 0;
 }

 static int
 nfnl_cthelper_new(struct sock *nfnl, struct sk_buff *skb,
 		  const struct nlmsghdr *nlh, const struct nlattr * const tb[])
 {
 	const char *helper_name;
 	struct nf_conntrack_helper *cur, *helper = NULL;
 	struct nf_conntrack_tuple tuple;
 	int ret = 0, i;

 	if (!tb[NFCTH_NAME] || !tb[NFCTH_TUPLE])
 		return -EINVAL;

 	helper_name = nla_data(tb[NFCTH_NAME]);

 	ret = nfnl_cthelper_parse_tuple(&tuple, tb[NFCTH_TUPLE]);
 	if (ret < 0)
 		return ret;

 	rcu_read_lock();
 	for (i = 0; i < nf_ct_helper_hsize && !helper; i++) {
 		hlist_for_each_entry_rcu(cur, &nf_ct_helper_hash[i], hnode) {

 			/* skip non-userspace conntrack helpers. */
 			if (!(cur->flags & NF_CT_HELPER_F_USERSPACE))
 				continue;

 			if (strncmp(cur->name, helper_name,
 					NF_CT_HELPER_NAME_LEN) != 0)
 				continue;

 			if ((tuple.src.l3num != cur->tuple.src.l3num ||
 			     tuple.dst.protonum != cur->tuple.dst.protonum))
 				continue;

 			if (nlh->nlmsg_flags & NLM_F_EXCL) {
 				ret = -EEXIST;
 				goto err;
 			}
 			helper = cur;
 			break;
 		}
 	}
 	rcu_read_unlock();

 	if (helper == NULL)
 		ret = nfnl_cthelper_create(tb, &tuple);
 	else
 		ret = nfnl_cthelper_update(tb, helper);

 	return ret;
 err:
 	rcu_read_unlock();
 	return ret;
 }

 static int
 nfnl_cthelper_dump_tuple(struct sk_buff *skb,
 			 struct nf_conntrack_helper *helper)
 {
 	struct nlattr *nest_parms;

 	nest_parms = nla_nest_start(skb, NFCTH_TUPLE | NLA_F_NESTED);
 	if (nest_parms == NULL)
 		goto nla_put_failure;

 	if (nla_put_be16(skb, NFCTH_TUPLE_L3PROTONUM,
 			 htons(helper->tuple.src.l3num)))
 		goto nla_put_failure;

 	if (nla_put_u8(skb, NFCTH_TUPLE_L4PROTONUM, helper->tuple.dst.protonum))
 		goto nla_put_failure;

 	nla_nest_end(skb, nest_parms);
 	return 0;

 nla_put_failure:
 	return -1;
 }

 static int
 nfnl_cthelper_dump_policy(struct sk_buff *skb,
 			struct nf_conntrack_helper *helper)
 {
 	int i;
 	struct nlattr *nest_parms1, *nest_parms2;

 	nest_parms1 = nla_nest_start(skb, NFCTH_POLICY | NLA_F_NESTED);
 	if (nest_parms1 == NULL)
 		goto nla_put_failure;

 	if (nla_put_be32(skb, NFCTH_POLICY_SET_NUM,
 			 htonl(helper->expect_class_max)))
 		goto nla_put_failure;

 	for (i=0; i<helper->expect_class_max; i++) {
 		nest_parms2 = nla_nest_start(skb,
 				(NFCTH_POLICY_SET+i) | NLA_F_NESTED);
 		if (nest_parms2 == NULL)
 			goto nla_put_failure;

 		if (nla_put_string(skb, NFCTH_POLICY_NAME,
 				   helper->expect_policy[i].name))
 			goto nla_put_failure;

 		if (nla_put_be32(skb, NFCTH_POLICY_EXPECT_MAX,
 				 htonl(helper->expect_policy[i].max_expected)))
 			goto nla_put_failure;

 		if (nla_put_be32(skb, NFCTH_POLICY_EXPECT_TIMEOUT,
 				 htonl(helper->expect_policy[i].timeout)))
 			goto nla_put_failure;

 		nla_nest_end(skb, nest_parms2);
 	}
 	nla_nest_end(skb, nest_parms1);
 	return 0;

 nla_put_failure:
 	return -1;
 }

 static int
 nfnl_cthelper_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
 			int event, struct nf_conntrack_helper *helper)
 {
 	struct nlmsghdr *nlh;
 	struct nfgenmsg *nfmsg;
 	unsigned int flags = portid ? NLM_F_MULTI : 0;
 	int status;

 	event |= NFNL_SUBSYS_CTHELPER << 8;
 	nlh = nlmsg_put(skb, portid, seq, event, sizeof(*nfmsg), flags);
 	if (nlh == NULL)
 		goto nlmsg_failure;

 	nfmsg = nlmsg_data(nlh);
 	nfmsg->nfgen_family = AF_UNSPEC;
 	nfmsg->version = NFNETLINK_V0;
 	nfmsg->res_id = 0;

 	if (nla_put_string(skb, NFCTH_NAME, helper->name))
 		goto nla_put_failure;

 	if (nla_put_be32(skb, NFCTH_QUEUE_NUM, htonl(helper->queue_num)))
 		goto nla_put_failure;

 	if (nfnl_cthelper_dump_tuple(skb, helper) < 0)
 		goto nla_put_failure;

 	if (nfnl_cthelper_dump_policy(skb, helper) < 0)
 		goto nla_put_failure;

 	if (nla_put_be32(skb, NFCTH_PRIV_DATA_LEN, htonl(helper->data_len)))
 		goto nla_put_failure;

 	if (helper->flags & NF_CT_HELPER_F_CONFIGURED)
 		status = NFCT_HELPER_STATUS_ENABLED;
 	else
 		status = NFCT_HELPER_STATUS_DISABLED;

 	if (nla_put_be32(skb, NFCTH_STATUS, htonl(status)))
 		goto nla_put_failure;

 	nlmsg_end(skb, nlh);
 	return skb->len;

 nlmsg_failure:
 nla_put_failure:
 	nlmsg_cancel(skb, nlh);
 	return -1;
 }

 static int
 nfnl_cthelper_dump_table(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	struct nf_conntrack_helper *cur, *last;

 	rcu_read_lock();
 	last = (struct nf_conntrack_helper *)cb->args[1];
 	for (; cb->args[0] < nf_ct_helper_hsize; cb->args[0]++) {
 restart:
 		hlist_for_each_entry_rcu(cur,
 				&nf_ct_helper_hash[cb->args[0]], hnode) {

 			/* skip non-userspace conntrack helpers. */
 			if (!(cur->flags & NF_CT_HELPER_F_USERSPACE))
 				continue;

 			if (cb->args[1]) {
 				if (cur != last)
 					continue;
 				cb->args[1] = 0;
 			}
 			if (nfnl_cthelper_fill_info(skb,
 					    NETLINK_CB(cb->skb).portid,
 					    cb->nlh->nlmsg_seq,
 					    NFNL_MSG_TYPE(cb->nlh->nlmsg_type),
 					    NFNL_MSG_CTHELPER_NEW, cur) < 0) {
 				cb->args[1] = (unsigned long)cur;
 				goto out;
 			}
 		}
 	}
 	if (cb->args[1]) {
 		cb->args[1] = 0;
 		goto restart;
 	}
 out:
 	rcu_read_unlock();
 	return skb->len;
 }

 static int
 nfnl_cthelper_get(struct sock *nfnl, struct sk_buff *skb,
 		  const struct nlmsghdr *nlh, const struct nlattr * const tb[])
 {
 	int ret = -ENOENT, i;
 	struct nf_conntrack_helper *cur;
 	struct sk_buff *skb2;
 	char *helper_name = NULL;
 	struct nf_conntrack_tuple tuple;
 	bool tuple_set = false;

 	if (nlh->nlmsg_flags & NLM_F_DUMP) {
 		struct netlink_dump_control c = {
 			.dump = nfnl_cthelper_dump_table,
 		};
 		return netlink_dump_start(nfnl, skb, nlh, &c);
 	}

 	if (tb[NFCTH_NAME])
 		helper_name = nla_data(tb[NFCTH_NAME]);

 	if (tb[NFCTH_TUPLE]) {
 		ret = nfnl_cthelper_parse_tuple(&tuple, tb[NFCTH_TUPLE]);
 		if (ret < 0)
 			return ret;

 		tuple_set = true;
 	}

 	for (i = 0; i < nf_ct_helper_hsize; i++) {
 		hlist_for_each_entry_rcu(cur, &nf_ct_helper_hash[i], hnode) {

 			/* skip non-userspace conntrack helpers. */
 			if (!(cur->flags & NF_CT_HELPER_F_USERSPACE))
 				continue;

 			if (helper_name && strncmp(cur->name, helper_name,
 						NF_CT_HELPER_NAME_LEN) != 0) {
 				continue;
 			}
 			if (tuple_set &&
 			    (tuple.src.l3num != cur->tuple.src.l3num ||
 			     tuple.dst.protonum != cur->tuple.dst.protonum))
 				continue;

 			skb2 = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
 			if (skb2 == NULL) {
 				ret = -ENOMEM;
 				break;
 			}

 			ret = nfnl_cthelper_fill_info(skb2, NETLINK_CB(skb).portid,
 						nlh->nlmsg_seq,
 						NFNL_MSG_TYPE(nlh->nlmsg_type),
 						NFNL_MSG_CTHELPER_NEW, cur);
 			if (ret <= 0) {
 				kfree_skb(skb2);
 				break;
 			}

 			ret = netlink_unicast(nfnl, skb2, NETLINK_CB(skb).portid,
 						MSG_DONTWAIT);
 			if (ret > 0)
 				ret = 0;

 			/* this avoids a loop in nfnetlink. */
 			return ret == -EAGAIN ? -ENOBUFS : ret;
 		}
 	}
 	return ret;
 }

 static int
 nfnl_cthelper_del(struct sock *nfnl, struct sk_buff *skb,
 	     const struct nlmsghdr *nlh, const struct nlattr * const tb[])
 {
 	char *helper_name = NULL;
 	struct nf_conntrack_helper *cur;
 	struct hlist_node *tmp;
 	struct nf_conntrack_tuple tuple;
 	bool tuple_set = false, found = false;
 	int i, j = 0, ret;

 	if (tb[NFCTH_NAME])
 		helper_name = nla_data(tb[NFCTH_NAME]);

 	if (tb[NFCTH_TUPLE]) {
 		ret = nfnl_cthelper_parse_tuple(&tuple, tb[NFCTH_TUPLE]);
 		if (ret < 0)
 			return ret;

 		tuple_set = true;
 	}

 	for (i = 0; i < nf_ct_helper_hsize; i++) {
 		hlist_for_each_entry_safe(cur, tmp, &nf_ct_helper_hash[i],
 								hnode) {
 			/* skip non-userspace conntrack helpers. */
 			if (!(cur->flags & NF_CT_HELPER_F_USERSPACE))
 				continue;

 			j++;

 			if (helper_name && strncmp(cur->name, helper_name,
 						NF_CT_HELPER_NAME_LEN) != 0) {
 				continue;
 			}
 			if (tuple_set &&
 			    (tuple.src.l3num != cur->tuple.src.l3num ||
 			     tuple.dst.protonum != cur->tuple.dst.protonum))
 				continue;

 			found = true;
 			nf_conntrack_helper_unregister(cur);
 		}
 	}
 	/* Make sure we return success if we flush and there is no helpers */
 	return (found || j == 0) ? 0 : -ENOENT;
 }

 static const struct nla_policy nfnl_cthelper_policy[NFCTH_MAX+1] = {
 	[NFCTH_NAME] = { .type = NLA_NUL_STRING,
 			 .len = NF_CT_HELPER_NAME_LEN-1 },
 	[NFCTH_QUEUE_NUM] = { .type = NLA_U32, },
 };

 static const struct nfnl_callback nfnl_cthelper_cb[NFNL_MSG_CTHELPER_MAX] = {
 	[NFNL_MSG_CTHELPER_NEW]		= { .call = nfnl_cthelper_new,
 					    .attr_count = NFCTH_MAX,
 					    .policy = nfnl_cthelper_policy },
 	[NFNL_MSG_CTHELPER_GET]		= { .call = nfnl_cthelper_get,
 					    .attr_count = NFCTH_MAX,
 					    .policy = nfnl_cthelper_policy },
 	[NFNL_MSG_CTHELPER_DEL]		= { .call = nfnl_cthelper_del,
 					    .attr_count = NFCTH_MAX,
 					    .policy = nfnl_cthelper_policy },
 };

 static const struct nfnetlink_subsystem nfnl_cthelper_subsys = {
 	.name				= "cthelper",
 	.subsys_id			= NFNL_SUBSYS_CTHELPER,
 	.cb_count			= NFNL_MSG_CTHELPER_MAX,
 	.cb				= nfnl_cthelper_cb,
 };

 MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_CTHELPER);

 static int __init nfnl_cthelper_init(void)
 {
 	int ret;

 	ret = nfnetlink_subsys_register(&nfnl_cthelper_subsys);
 	if (ret < 0) {
 		pr_err("nfnl_cthelper: cannot register with nfnetlink.\n");
 		goto err_out;
 	}
 	return 0;
 err_out:
 	return ret;
 }

 static void __exit nfnl_cthelper_exit(void)
 {
 	struct nf_conntrack_helper *cur;
 	struct hlist_node *tmp;
 	int i;

 	nfnetlink_subsys_unregister(&nfnl_cthelper_subsys);

 	for (i=0; i<nf_ct_helper_hsize; i++) {
 		hlist_for_each_entry_safe(cur, tmp, &nf_ct_helper_hash[i],
 									hnode) {
 			/* skip non-userspace conntrack helpers. */
 			if (!(cur->flags & NF_CT_HELPER_F_USERSPACE))
 				continue;

 			nf_conntrack_helper_unregister(cur);
 		}
 	}
 }

 module_init(nfnl_cthelper_init);
 module_exit(nfnl_cthelper_exit);
	/*
	* (C) 2012 Pablo Neira Ayuso <pablo@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 (or any later at your option).
	*
	* This software has been sponsored by Vyatta Inc. <http://www.vyatta.com>
	*/
	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/kernel.h>
	#include <linux/skbuff.h>
	#include <linux/netlink.h>
	#include <linux/rculist.h>
	#include <linux/slab.h>
	#include <linux/types.h>
	#include <linux/list.h>
	#include <linux/errno.h>
	#include <net/netlink.h>
	#include <net/sock.h>

	#include <net/netfilter/nf_conntrack_helper.h>
	#include <net/netfilter/nf_conntrack_expect.h>
	#include <net/netfilter/nf_conntrack_ecache.h>

	#include <linux/netfilter/nfnetlink.h>
	#include <linux/netfilter/nfnetlink_conntrack.h>
	#include <linux/netfilter/nfnetlink_cthelper.h>

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
	MODULE_DESCRIPTION("nfnl_cthelper: User-space connection tracking helpers");

	static int
	nfnl_userspace_cthelper(struct sk_buff *skb, unsigned int protoff,
	struct nf_conn *ct, enum ip_conntrack_info ctinfo)
	{
	const struct nf_conn_help *help;
	struct nf_conntrack_helper *helper;

	help = nfct_help(ct);
	if (help == NULL)
	return NF_DROP;

	/* rcu_read_lock()ed by nf_hook_slow */
	helper = rcu_dereference(help->helper);
	if (helper == NULL)
	return NF_DROP;

	/* This is an user-space helper not yet configured, skip. */
	if ((helper->flags &
	(NF_CT_HELPER_F_USERSPACE \| NF_CT_HELPER_F_CONFIGURED)) ==
	NF_CT_HELPER_F_USERSPACE)
	return NF_ACCEPT;

	/* If the user-space helper is not available, don't block traffic. */
	return NF_QUEUE_NR(helper->queue_num) \| NF_VERDICT_FLAG_QUEUE_BYPASS;
	}

	static const struct nla_policy nfnl_cthelper_tuple_pol[NFCTH_TUPLE_MAX+1] = {
	[NFCTH_TUPLE_L3PROTONUM] = { .type = NLA_U16, },
	[NFCTH_TUPLE_L4PROTONUM] = { .type = NLA_U8, },
	};

	static int
	nfnl_cthelper_parse_tuple(struct nf_conntrack_tuple *tuple,
	const struct nlattr *attr)
	{
	int err;
	struct nlattr *tb[NFCTH_TUPLE_MAX+1];

	err = nla_parse_nested(tb, NFCTH_TUPLE_MAX, attr, nfnl_cthelper_tuple_pol);
	if (err < 0)
	return err;

	if (!tb[NFCTH_TUPLE_L3PROTONUM] \|\| !tb[NFCTH_TUPLE_L4PROTONUM])
	return -EINVAL;

	tuple->src.l3num = ntohs(nla_get_be16(tb[NFCTH_TUPLE_L3PROTONUM]));
	tuple->dst.protonum = nla_get_u8(tb[NFCTH_TUPLE_L4PROTONUM]);

	return 0;
	}

	static int
	nfnl_cthelper_from_nlattr(struct nlattr attr, struct nf_conn ct)
	{
	const struct nf_conn_help *help = nfct_help(ct);

	if (attr == NULL)
	return -EINVAL;

	if (help->helper->data_len == 0)
	return -EINVAL;

	memcpy(&help->data, nla_data(attr), help->helper->data_len);
	return 0;
	}

	static int
	nfnl_cthelper_to_nlattr(struct sk_buff skb, const struct nf_conn ct)
	{
	const struct nf_conn_help *help = nfct_help(ct);

	if (help->helper->data_len &&
	nla_put(skb, CTA_HELP_INFO, help->helper->data_len, &help->data))
	goto nla_put_failure;

	return 0;

	nla_put_failure:
	return -ENOSPC;
	}

	static const struct nla_policy nfnl_cthelper_expect_pol[NFCTH_POLICY_MAX+1] = {
	[NFCTH_POLICY_NAME] = { .type = NLA_NUL_STRING,
	.len = NF_CT_HELPER_NAME_LEN-1 },
	[NFCTH_POLICY_EXPECT_MAX] = { .type = NLA_U32, },
	[NFCTH_POLICY_EXPECT_TIMEOUT] = { .type = NLA_U32, },
	};

	static int
	nfnl_cthelper_expect_policy(struct nf_conntrack_expect_policy *expect_policy,
	const struct nlattr *attr)
	{
	int err;
	struct nlattr *tb[NFCTH_POLICY_MAX+1];

	err = nla_parse_nested(tb, NFCTH_POLICY_MAX, attr, nfnl_cthelper_expect_pol);
	if (err < 0)
	return err;

	if (!tb[NFCTH_POLICY_NAME] \|\|
	!tb[NFCTH_POLICY_EXPECT_MAX] \|\|
	!tb[NFCTH_POLICY_EXPECT_TIMEOUT])
	return -EINVAL;

	strncpy(expect_policy->name,
	nla_data(tb[NFCTH_POLICY_NAME]), NF_CT_HELPER_NAME_LEN);
	expect_policy->max_expected =
	ntohl(nla_get_be32(tb[NFCTH_POLICY_EXPECT_MAX]));
	expect_policy->timeout =
	ntohl(nla_get_be32(tb[NFCTH_POLICY_EXPECT_TIMEOUT]));

	return 0;
	}

	static const struct nla_policy
	nfnl_cthelper_expect_policy_set[NFCTH_POLICY_SET_MAX+1] = {
	[NFCTH_POLICY_SET_NUM] = { .type = NLA_U32, },
	};

	static int
	nfnl_cthelper_parse_expect_policy(struct nf_conntrack_helper *helper,
	const struct nlattr *attr)
	{
	int i, ret;
	struct nf_conntrack_expect_policy *expect_policy;
	struct nlattr *tb[NFCTH_POLICY_SET_MAX+1];

	ret = nla_parse_nested(tb, NFCTH_POLICY_SET_MAX, attr,
	nfnl_cthelper_expect_policy_set);
	if (ret < 0)
	return ret;

	if (!tb[NFCTH_POLICY_SET_NUM])
	return -EINVAL;

	helper->expect_class_max =
	ntohl(nla_get_be32(tb[NFCTH_POLICY_SET_NUM]));

	if (helper->expect_class_max != 0 &&
	helper->expect_class_max > NF_CT_MAX_EXPECT_CLASSES)
	return -EOVERFLOW;

	expect_policy = kzalloc(sizeof(struct nf_conntrack_expect_policy) *
	helper->expect_class_max, GFP_KERNEL);
	if (expect_policy == NULL)
	return -ENOMEM;

	for (i=0; i<helper->expect_class_max; i++) {
	if (!tb[NFCTH_POLICY_SET+i])
	goto err;

	ret = nfnl_cthelper_expect_policy(&expect_policy[i],
	tb[NFCTH_POLICY_SET+i]);
	if (ret < 0)
	goto err;
	}
	helper->expect_policy = expect_policy;
	return 0;
	err:
	kfree(expect_policy);
	return -EINVAL;
	}

	static int
	nfnl_cthelper_create(const struct nlattr * const tb[],
	struct nf_conntrack_tuple *tuple)
	{
	struct nf_conntrack_helper *helper;
	int ret;

	if (!tb[NFCTH_TUPLE] \|\| !tb[NFCTH_POLICY] \|\| !tb[NFCTH_PRIV_DATA_LEN])
	return -EINVAL;

	helper = kzalloc(sizeof(struct nf_conntrack_helper), GFP_KERNEL);
	if (helper == NULL)
	return -ENOMEM;

	ret = nfnl_cthelper_parse_expect_policy(helper, tb[NFCTH_POLICY]);
	if (ret < 0)
	goto err;

	strncpy(helper->name, nla_data(tb[NFCTH_NAME]), NF_CT_HELPER_NAME_LEN);
	helper->data_len = ntohl(nla_get_be32(tb[NFCTH_PRIV_DATA_LEN]));
	helper->flags \|= NF_CT_HELPER_F_USERSPACE;
	memcpy(&helper->tuple, tuple, sizeof(struct nf_conntrack_tuple));

	helper->me = THIS_MODULE;
	helper->help = nfnl_userspace_cthelper;
	helper->from_nlattr = nfnl_cthelper_from_nlattr;
	helper->to_nlattr = nfnl_cthelper_to_nlattr;

	/* Default to queue number zero, this can be updated at any time. */
	if (tb[NFCTH_QUEUE_NUM])
	helper->queue_num = ntohl(nla_get_be32(tb[NFCTH_QUEUE_NUM]));

	if (tb[NFCTH_STATUS]) {
	int status = ntohl(nla_get_be32(tb[NFCTH_STATUS]));

	switch(status) {
	case NFCT_HELPER_STATUS_ENABLED:
	helper->flags \|= NF_CT_HELPER_F_CONFIGURED;
	break;
	case NFCT_HELPER_STATUS_DISABLED:
	helper->flags &= ~NF_CT_HELPER_F_CONFIGURED;
	break;
	}
	}

	ret = nf_conntrack_helper_register(helper);
	if (ret < 0)
	goto err;

	return 0;
	err:
	kfree(helper);
	return ret;
	}

	static int
	nfnl_cthelper_update(const struct nlattr * const tb[],
	struct nf_conntrack_helper *helper)
	{
	int ret;

	if (tb[NFCTH_PRIV_DATA_LEN])
	return -EBUSY;

	if (tb[NFCTH_POLICY]) {
	ret = nfnl_cthelper_parse_expect_policy(helper,
	tb[NFCTH_POLICY]);
	if (ret < 0)
	return ret;
	}
	if (tb[NFCTH_QUEUE_NUM])
	helper->queue_num = ntohl(nla_get_be32(tb[NFCTH_QUEUE_NUM]));

	if (tb[NFCTH_STATUS]) {
	int status = ntohl(nla_get_be32(tb[NFCTH_STATUS]));

	switch(status) {
	case NFCT_HELPER_STATUS_ENABLED:
	helper->flags \|= NF_CT_HELPER_F_CONFIGURED;
	break;
	case NFCT_HELPER_STATUS_DISABLED:
	helper->flags &= ~NF_CT_HELPER_F_CONFIGURED;
	break;
	}
	}
	return 0;
	}

	static int
	nfnl_cthelper_new(struct sock nfnl, struct sk_buff skb,
	const struct nlmsghdr nlh, const struct nlattr const tb[])
	{
	const char *helper_name;
	struct nf_conntrack_helper cur, helper = NULL;
	struct nf_conntrack_tuple tuple;
	int ret = 0, i;

	if (!tb[NFCTH_NAME] \|\| !tb[NFCTH_TUPLE])
	return -EINVAL;

	helper_name = nla_data(tb[NFCTH_NAME]);

	ret = nfnl_cthelper_parse_tuple(&tuple, tb[NFCTH_TUPLE]);
	if (ret < 0)
	return ret;

	rcu_read_lock();
	for (i = 0; i < nf_ct_helper_hsize && !helper; i++) {
	hlist_for_each_entry_rcu(cur, &nf_ct_helper_hash[i], hnode) {

	/* skip non-userspace conntrack helpers. */
	if (!(cur->flags & NF_CT_HELPER_F_USERSPACE))
	continue;

	if (strncmp(cur->name, helper_name,
	NF_CT_HELPER_NAME_LEN) != 0)
	continue;

	if ((tuple.src.l3num != cur->tuple.src.l3num \|\|
	tuple.dst.protonum != cur->tuple.dst.protonum))
	continue;

	if (nlh->nlmsg_flags & NLM_F_EXCL) {
	ret = -EEXIST;
	goto err;
	}
	helper = cur;
	break;
	}
	}
	rcu_read_unlock();

	if (helper == NULL)
	ret = nfnl_cthelper_create(tb, &tuple);
	else
	ret = nfnl_cthelper_update(tb, helper);

	return ret;
	err:
	rcu_read_unlock();
	return ret;
	}

	static int
	nfnl_cthelper_dump_tuple(struct sk_buff *skb,
	struct nf_conntrack_helper *helper)
	{
	struct nlattr *nest_parms;

	nest_parms = nla_nest_start(skb, NFCTH_TUPLE \| NLA_F_NESTED);
	if (nest_parms == NULL)
	goto nla_put_failure;

	if (nla_put_be16(skb, NFCTH_TUPLE_L3PROTONUM,
	htons(helper->tuple.src.l3num)))
	goto nla_put_failure;

	if (nla_put_u8(skb, NFCTH_TUPLE_L4PROTONUM, helper->tuple.dst.protonum))
	goto nla_put_failure;

	nla_nest_end(skb, nest_parms);
	return 0;

	nla_put_failure:
	return -1;
	}

	static int
	nfnl_cthelper_dump_policy(struct sk_buff *skb,
	struct nf_conntrack_helper *helper)
	{
	int i;
	struct nlattr nest_parms1, nest_parms2;

	nest_parms1 = nla_nest_start(skb, NFCTH_POLICY \| NLA_F_NESTED);
	if (nest_parms1 == NULL)
	goto nla_put_failure;

	if (nla_put_be32(skb, NFCTH_POLICY_SET_NUM,
	htonl(helper->expect_class_max)))
	goto nla_put_failure;

	for (i=0; i<helper->expect_class_max; i++) {
	nest_parms2 = nla_nest_start(skb,
	(NFCTH_POLICY_SET+i) \| NLA_F_NESTED);
	if (nest_parms2 == NULL)
	goto nla_put_failure;

	if (nla_put_string(skb, NFCTH_POLICY_NAME,
	helper->expect_policy[i].name))
	goto nla_put_failure;

	if (nla_put_be32(skb, NFCTH_POLICY_EXPECT_MAX,
	htonl(helper->expect_policy[i].max_expected)))
	goto nla_put_failure;

	if (nla_put_be32(skb, NFCTH_POLICY_EXPECT_TIMEOUT,
	htonl(helper->expect_policy[i].timeout)))
	goto nla_put_failure;

	nla_nest_end(skb, nest_parms2);
	}
	nla_nest_end(skb, nest_parms1);
	return 0;

	nla_put_failure:
	return -1;
	}

	static int
	nfnl_cthelper_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
	int event, struct nf_conntrack_helper *helper)
	{
	struct nlmsghdr *nlh;
	struct nfgenmsg *nfmsg;
	unsigned int flags = portid ? NLM_F_MULTI : 0;
	int status;

	event \|= NFNL_SUBSYS_CTHELPER << 8;
	nlh = nlmsg_put(skb, portid, seq, event, sizeof(*nfmsg), flags);
	if (nlh == NULL)
	goto nlmsg_failure;

	nfmsg = nlmsg_data(nlh);
	nfmsg->nfgen_family = AF_UNSPEC;
	nfmsg->version = NFNETLINK_V0;
	nfmsg->res_id = 0;

	if (nla_put_string(skb, NFCTH_NAME, helper->name))
	goto nla_put_failure;

	if (nla_put_be32(skb, NFCTH_QUEUE_NUM, htonl(helper->queue_num)))
	goto nla_put_failure;

	if (nfnl_cthelper_dump_tuple(skb, helper) < 0)
	goto nla_put_failure;

	if (nfnl_cthelper_dump_policy(skb, helper) < 0)
	goto nla_put_failure;

	if (nla_put_be32(skb, NFCTH_PRIV_DATA_LEN, htonl(helper->data_len)))
	goto nla_put_failure;

	if (helper->flags & NF_CT_HELPER_F_CONFIGURED)
	status = NFCT_HELPER_STATUS_ENABLED;
	else
	status = NFCT_HELPER_STATUS_DISABLED;

	if (nla_put_be32(skb, NFCTH_STATUS, htonl(status)))
	goto nla_put_failure;

	nlmsg_end(skb, nlh);
	return skb->len;

	nlmsg_failure:
	nla_put_failure:
	nlmsg_cancel(skb, nlh);
	return -1;
	}

	static int
	nfnl_cthelper_dump_table(struct sk_buff skb, struct netlink_callback cb)
	{
	struct nf_conntrack_helper cur, last;

	rcu_read_lock();
	last = (struct nf_conntrack_helper *)cb->args[1];
	for (; cb->args[0] < nf_ct_helper_hsize; cb->args[0]++) {
	restart:
	hlist_for_each_entry_rcu(cur,
	&nf_ct_helper_hash[cb->args[0]], hnode) {

	/* skip non-userspace conntrack helpers. */
	if (!(cur->flags & NF_CT_HELPER_F_USERSPACE))
	continue;

	if (cb->args[1]) {
	if (cur != last)
	continue;
	cb->args[1] = 0;
	}
	if (nfnl_cthelper_fill_info(skb,
	NETLINK_CB(cb->skb).portid,
	cb->nlh->nlmsg_seq,
	NFNL_MSG_TYPE(cb->nlh->nlmsg_type),
	NFNL_MSG_CTHELPER_NEW, cur) < 0) {
	cb->args[1] = (unsigned long)cur;
	goto out;
	}
	}
	}
	if (cb->args[1]) {
	cb->args[1] = 0;
	goto restart;
	}
	out:
	rcu_read_unlock();
	return skb->len;
	}

	static int
	nfnl_cthelper_get(struct sock nfnl, struct sk_buff skb,
	const struct nlmsghdr nlh, const struct nlattr const tb[])
	{
	int ret = -ENOENT, i;
	struct nf_conntrack_helper *cur;
	struct sk_buff *skb2;
	char *helper_name = NULL;
	struct nf_conntrack_tuple tuple;
	bool tuple_set = false;

	if (nlh->nlmsg_flags & NLM_F_DUMP) {
	struct netlink_dump_control c = {
	.dump = nfnl_cthelper_dump_table,
	};
	return netlink_dump_start(nfnl, skb, nlh, &c);
	}

	if (tb[NFCTH_NAME])
	helper_name = nla_data(tb[NFCTH_NAME]);

	if (tb[NFCTH_TUPLE]) {
	ret = nfnl_cthelper_parse_tuple(&tuple, tb[NFCTH_TUPLE]);
	if (ret < 0)
	return ret;

	tuple_set = true;
	}

	for (i = 0; i < nf_ct_helper_hsize; i++) {
	hlist_for_each_entry_rcu(cur, &nf_ct_helper_hash[i], hnode) {

	/* skip non-userspace conntrack helpers. */
	if (!(cur->flags & NF_CT_HELPER_F_USERSPACE))
	continue;

	if (helper_name && strncmp(cur->name, helper_name,
	NF_CT_HELPER_NAME_LEN) != 0) {
	continue;
	}
	if (tuple_set &&
	(tuple.src.l3num != cur->tuple.src.l3num \|\|
	tuple.dst.protonum != cur->tuple.dst.protonum))
	continue;

	skb2 = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
	if (skb2 == NULL) {
	ret = -ENOMEM;
	break;
	}

	ret = nfnl_cthelper_fill_info(skb2, NETLINK_CB(skb).portid,
	nlh->nlmsg_seq,
	NFNL_MSG_TYPE(nlh->nlmsg_type),
	NFNL_MSG_CTHELPER_NEW, cur);
	if (ret <= 0) {
	kfree_skb(skb2);
	break;
	}

	ret = netlink_unicast(nfnl, skb2, NETLINK_CB(skb).portid,
	MSG_DONTWAIT);
	if (ret > 0)
	ret = 0;

	/* this avoids a loop in nfnetlink. */
	return ret == -EAGAIN ? -ENOBUFS : ret;
	}
	}
	return ret;
	}

	static int
	nfnl_cthelper_del(struct sock nfnl, struct sk_buff skb,
	const struct nlmsghdr nlh, const struct nlattr const tb[])
	{
	char *helper_name = NULL;
	struct nf_conntrack_helper *cur;
	struct hlist_node *tmp;
	struct nf_conntrack_tuple tuple;
	bool tuple_set = false, found = false;
	int i, j = 0, ret;

	if (tb[NFCTH_NAME])
	helper_name = nla_data(tb[NFCTH_NAME]);

	if (tb[NFCTH_TUPLE]) {
	ret = nfnl_cthelper_parse_tuple(&tuple, tb[NFCTH_TUPLE]);
	if (ret < 0)
	return ret;

	tuple_set = true;
	}

	for (i = 0; i < nf_ct_helper_hsize; i++) {
	hlist_for_each_entry_safe(cur, tmp, &nf_ct_helper_hash[i],
	hnode) {
	/* skip non-userspace conntrack helpers. */
	if (!(cur->flags & NF_CT_HELPER_F_USERSPACE))
	continue;

	j++;

	if (helper_name && strncmp(cur->name, helper_name,
	NF_CT_HELPER_NAME_LEN) != 0) {
	continue;
	}
	if (tuple_set &&
	(tuple.src.l3num != cur->tuple.src.l3num \|\|
	tuple.dst.protonum != cur->tuple.dst.protonum))
	continue;

	found = true;
	nf_conntrack_helper_unregister(cur);
	}
	}
	/* Make sure we return success if we flush and there is no helpers */
	return (found \|\| j == 0) ? 0 : -ENOENT;
	}

	static const struct nla_policy nfnl_cthelper_policy[NFCTH_MAX+1] = {
	[NFCTH_NAME] = { .type = NLA_NUL_STRING,
	.len = NF_CT_HELPER_NAME_LEN-1 },
	[NFCTH_QUEUE_NUM] = { .type = NLA_U32, },
	};

	static const struct nfnl_callback nfnl_cthelper_cb[NFNL_MSG_CTHELPER_MAX] = {
	[NFNL_MSG_CTHELPER_NEW] = { .call = nfnl_cthelper_new,
	.attr_count = NFCTH_MAX,
	.policy = nfnl_cthelper_policy },
	[NFNL_MSG_CTHELPER_GET] = { .call = nfnl_cthelper_get,
	.attr_count = NFCTH_MAX,
	.policy = nfnl_cthelper_policy },
	[NFNL_MSG_CTHELPER_DEL] = { .call = nfnl_cthelper_del,
	.attr_count = NFCTH_MAX,
	.policy = nfnl_cthelper_policy },
	};

	static const struct nfnetlink_subsystem nfnl_cthelper_subsys = {
	.name = "cthelper",
	.subsys_id = NFNL_SUBSYS_CTHELPER,
	.cb_count = NFNL_MSG_CTHELPER_MAX,
	.cb = nfnl_cthelper_cb,
	};

	MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_CTHELPER);

	static int __init nfnl_cthelper_init(void)
	{
	int ret;

	ret = nfnetlink_subsys_register(&nfnl_cthelper_subsys);
	if (ret < 0) {
	pr_err("nfnl_cthelper: cannot register with nfnetlink.\n");
	goto err_out;
	}
	return 0;
	err_out:
	return ret;
	}

	static void __exit nfnl_cthelper_exit(void)
	{
	struct nf_conntrack_helper *cur;
	struct hlist_node *tmp;
	int i;

	nfnetlink_subsys_unregister(&nfnl_cthelper_subsys);

	for (i=0; i<nf_ct_helper_hsize; i++) {
	hlist_for_each_entry_safe(cur, tmp, &nf_ct_helper_hash[i],
	hnode) {
	/* skip non-userspace conntrack helpers. */
	if (!(cur->flags & NF_CT_HELPER_F_USERSPACE))
	continue;

	nf_conntrack_helper_unregister(cur);
	}
	}
	}

	module_init(nfnl_cthelper_init);
	module_exit(nfnl_cthelper_exit);