net/ipv4/netfilter/nf_nat_h323.c - kernel/quantenna - Git at Google

 /*
  * H.323 extension for NAT alteration.
  *
  * Copyright (c) 2006 Jing Min Zhao <zhaojingmin@users.sourceforge.net>
  * Copyright (c) 2006-2012 Patrick McHardy <kaber@trash.net>
  *
  * This source code is licensed under General Public License version 2.
  *
  * Based on the 'brute force' H.323 NAT module by
  * Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
  */

 #include <linux/module.h>
 #include <linux/tcp.h>
 #include <net/tcp.h>

 #include <net/netfilter/nf_nat.h>
 #include <net/netfilter/nf_nat_helper.h>
 #include <net/netfilter/nf_conntrack_helper.h>
 #include <net/netfilter/nf_conntrack_expect.h>
 #include <linux/netfilter/nf_conntrack_h323.h>

 /****************************************************************************/
 static int set_addr(struct sk_buff *skb, unsigned int protoff,
 		    unsigned char **data, int dataoff,
 		    unsigned int addroff, __be32 ip, __be16 port)
 {
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 	struct {
 		__be32 ip;
 		__be16 port;
 	} __attribute__ ((__packed__)) buf;
 	const struct tcphdr *th;
 	struct tcphdr _tcph;

 	buf.ip = ip;
 	buf.port = port;
 	addroff += dataoff;

 	if (ip_hdr(skb)->protocol == IPPROTO_TCP) {
 		if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
 					      protoff, addroff, sizeof(buf),
 					      (char *) &buf, sizeof(buf))) {
 			net_notice_ratelimited("nf_nat_h323: nf_nat_mangle_tcp_packet error\n");
 			return -1;
 		}

 		/* Relocate data pointer */
 		th = skb_header_pointer(skb, ip_hdrlen(skb),
 					sizeof(_tcph), &_tcph);
 		if (th == NULL)
 			return -1;
 		*data = skb->data + ip_hdrlen(skb) + th->doff * 4 + dataoff;
 	} else {
 		if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo,
 					      protoff, addroff, sizeof(buf),
 					      (char *) &buf, sizeof(buf))) {
 			net_notice_ratelimited("nf_nat_h323: nf_nat_mangle_udp_packet error\n");
 			return -1;
 		}
 		/* nf_nat_mangle_udp_packet uses skb_make_writable() to copy
 		 * or pull everything in a linear buffer, so we can safely
 		 * use the skb pointers now */
 		*data = skb->data + ip_hdrlen(skb) + sizeof(struct udphdr);
 	}

 	return 0;
 }

 /****************************************************************************/
 static int set_h225_addr(struct sk_buff *skb, unsigned int protoff,
 			 unsigned char **data, int dataoff,
 			 TransportAddress *taddr,
 			 union nf_inet_addr *addr, __be16 port)
 {
 	return set_addr(skb, protoff, data, dataoff, taddr->ipAddress.ip,
 			addr->ip, port);
 }

 /****************************************************************************/
 static int set_h245_addr(struct sk_buff *skb, unsigned protoff,
 			 unsigned char **data, int dataoff,
 			 H245_TransportAddress *taddr,
 			 union nf_inet_addr *addr, __be16 port)
 {
 	return set_addr(skb, protoff, data, dataoff,
 			taddr->unicastAddress.iPAddress.network,
 			addr->ip, port);
 }

 /****************************************************************************/
 static int set_sig_addr(struct sk_buff *skb, struct nf_conn *ct,
 			enum ip_conntrack_info ctinfo,
 			unsigned int protoff, unsigned char **data,
 			TransportAddress *taddr, int count)
 {
 	const struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	int i;
 	__be16 port;
 	union nf_inet_addr addr;

 	for (i = 0; i < count; i++) {
 		if (get_h225_addr(ct, *data, &taddr[i], &addr, &port)) {
 			if (addr.ip == ct->tuplehash[dir].tuple.src.u3.ip &&
 			    port == info->sig_port[dir]) {
 				/* GW->GK */

 				/* Fix for Gnomemeeting */
 				if (i > 0 &&
 				    get_h225_addr(ct, *data, &taddr[0],
 						  &addr, &port) &&
 				    (ntohl(addr.ip) & 0xff000000) == 0x7f000000)
 					i = 0;

 				pr_debug("nf_nat_ras: set signal address %pI4:%hu->%pI4:%hu\n",
 					 &addr.ip, port,
 					 &ct->tuplehash[!dir].tuple.dst.u3.ip,
 					 info->sig_port[!dir]);
 				return set_h225_addr(skb, protoff, data, 0,
 						     &taddr[i],
 						     &ct->tuplehash[!dir].
 						     tuple.dst.u3,
 						     info->sig_port[!dir]);
 			} else if (addr.ip == ct->tuplehash[dir].tuple.dst.u3.ip &&
 				   port == info->sig_port[dir]) {
 				/* GK->GW */
 				pr_debug("nf_nat_ras: set signal address %pI4:%hu->%pI4:%hu\n",
 					 &addr.ip, port,
 					 &ct->tuplehash[!dir].tuple.src.u3.ip,
 					 info->sig_port[!dir]);
 				return set_h225_addr(skb, protoff, data, 0,
 						     &taddr[i],
 						     &ct->tuplehash[!dir].
 						     tuple.src.u3,
 						     info->sig_port[!dir]);
 			}
 		}
 	}

 	return 0;
 }

 /****************************************************************************/
 static int set_ras_addr(struct sk_buff *skb, struct nf_conn *ct,
 			enum ip_conntrack_info ctinfo,
 			unsigned int protoff, unsigned char **data,
 			TransportAddress *taddr, int count)
 {
 	int dir = CTINFO2DIR(ctinfo);
 	int i;
 	__be16 port;
 	union nf_inet_addr addr;

 	for (i = 0; i < count; i++) {
 		if (get_h225_addr(ct, *data, &taddr[i], &addr, &port) &&
 		    addr.ip == ct->tuplehash[dir].tuple.src.u3.ip &&
 		    port == ct->tuplehash[dir].tuple.src.u.udp.port) {
 			pr_debug("nf_nat_ras: set rasAddress %pI4:%hu->%pI4:%hu\n",
 				 &addr.ip, ntohs(port),
 				 &ct->tuplehash[!dir].tuple.dst.u3.ip,
 				 ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port));
 			return set_h225_addr(skb, protoff, data, 0, &taddr[i],
 					     &ct->tuplehash[!dir].tuple.dst.u3,
 					     ct->tuplehash[!dir].tuple.
 								dst.u.udp.port);
 		}
 	}

 	return 0;
 }

 /****************************************************************************/
 static int nat_rtp_rtcp(struct sk_buff *skb, struct nf_conn *ct,
 			enum ip_conntrack_info ctinfo,
 			unsigned int protoff, unsigned char **data, int dataoff,
 			H245_TransportAddress *taddr,
 			__be16 port, __be16 rtp_port,
 			struct nf_conntrack_expect *rtp_exp,
 			struct nf_conntrack_expect *rtcp_exp)
 {
 	struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	int i;
 	u_int16_t nated_port;

 	/* Set expectations for NAT */
 	rtp_exp->saved_proto.udp.port = rtp_exp->tuple.dst.u.udp.port;
 	rtp_exp->expectfn = nf_nat_follow_master;
 	rtp_exp->dir = !dir;
 	rtcp_exp->saved_proto.udp.port = rtcp_exp->tuple.dst.u.udp.port;
 	rtcp_exp->expectfn = nf_nat_follow_master;
 	rtcp_exp->dir = !dir;

 	/* Lookup existing expects */
 	for (i = 0; i < H323_RTP_CHANNEL_MAX; i++) {
 		if (info->rtp_port[i][dir] == rtp_port) {
 			/* Expected */

 			/* Use allocated ports first. This will refresh
 			 * the expects */
 			rtp_exp->tuple.dst.u.udp.port = info->rtp_port[i][dir];
 			rtcp_exp->tuple.dst.u.udp.port =
 			    htons(ntohs(info->rtp_port[i][dir]) + 1);
 			break;
 		} else if (info->rtp_port[i][dir] == 0) {
 			/* Not expected */
 			break;
 		}
 	}

 	/* Run out of expectations */
 	if (i >= H323_RTP_CHANNEL_MAX) {
 		net_notice_ratelimited("nf_nat_h323: out of expectations\n");
 		return 0;
 	}

 	/* Try to get a pair of ports. */
 	for (nated_port = ntohs(rtp_exp->tuple.dst.u.udp.port);
 	     nated_port != 0; nated_port += 2) {
 		int ret;

 		rtp_exp->tuple.dst.u.udp.port = htons(nated_port);
 		ret = nf_ct_expect_related(rtp_exp);
 		if (ret == 0) {
 			rtcp_exp->tuple.dst.u.udp.port =
 			    htons(nated_port + 1);
 			ret = nf_ct_expect_related(rtcp_exp);
 			if (ret == 0)
 				break;
 			else if (ret == -EBUSY) {
 				nf_ct_unexpect_related(rtp_exp);
 				continue;
 			} else if (ret < 0) {
 				nf_ct_unexpect_related(rtp_exp);
 				nated_port = 0;
 				break;
 			}
 		} else if (ret != -EBUSY) {
 			nated_port = 0;
 			break;
 		}
 	}

 	if (nated_port == 0) {	/* No port available */
 		net_notice_ratelimited("nf_nat_h323: out of RTP ports\n");
 		return 0;
 	}

 	/* Modify signal */
 	if (set_h245_addr(skb, protoff, data, dataoff, taddr,
 			  &ct->tuplehash[!dir].tuple.dst.u3,
 			  htons((port & htons(1)) ? nated_port + 1 :
 						    nated_port)) == 0) {
 		/* Save ports */
 		info->rtp_port[i][dir] = rtp_port;
 		info->rtp_port[i][!dir] = htons(nated_port);
 	} else {
 		nf_ct_unexpect_related(rtp_exp);
 		nf_ct_unexpect_related(rtcp_exp);
 		return -1;
 	}

 	/* Success */
 	pr_debug("nf_nat_h323: expect RTP %pI4:%hu->%pI4:%hu\n",
 		 &rtp_exp->tuple.src.u3.ip,
 		 ntohs(rtp_exp->tuple.src.u.udp.port),
 		 &rtp_exp->tuple.dst.u3.ip,
 		 ntohs(rtp_exp->tuple.dst.u.udp.port));
 	pr_debug("nf_nat_h323: expect RTCP %pI4:%hu->%pI4:%hu\n",
 		 &rtcp_exp->tuple.src.u3.ip,
 		 ntohs(rtcp_exp->tuple.src.u.udp.port),
 		 &rtcp_exp->tuple.dst.u3.ip,
 		 ntohs(rtcp_exp->tuple.dst.u.udp.port));

 	return 0;
 }

 /****************************************************************************/
 static int nat_t120(struct sk_buff *skb, struct nf_conn *ct,
 		    enum ip_conntrack_info ctinfo,
 		    unsigned int protoff, unsigned char **data, int dataoff,
 		    H245_TransportAddress *taddr, __be16 port,
 		    struct nf_conntrack_expect *exp)
 {
 	int dir = CTINFO2DIR(ctinfo);
 	u_int16_t nated_port = ntohs(port);

 	/* Set expectations for NAT */
 	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 	exp->expectfn = nf_nat_follow_master;
 	exp->dir = !dir;

 	/* Try to get same port: if not, try to change it. */
 	for (; nated_port != 0; nated_port++) {
 		int ret;

 		exp->tuple.dst.u.tcp.port = htons(nated_port);
 		ret = nf_ct_expect_related(exp);
 		if (ret == 0)
 			break;
 		else if (ret != -EBUSY) {
 			nated_port = 0;
 			break;
 		}
 	}

 	if (nated_port == 0) {	/* No port available */
 		net_notice_ratelimited("nf_nat_h323: out of TCP ports\n");
 		return 0;
 	}

 	/* Modify signal */
 	if (set_h245_addr(skb, protoff, data, dataoff, taddr,
 			  &ct->tuplehash[!dir].tuple.dst.u3,
 			  htons(nated_port)) < 0) {
 		nf_ct_unexpect_related(exp);
 		return -1;
 	}

 	pr_debug("nf_nat_h323: expect T.120 %pI4:%hu->%pI4:%hu\n",
 		 &exp->tuple.src.u3.ip,
 		 ntohs(exp->tuple.src.u.tcp.port),
 		 &exp->tuple.dst.u3.ip,
 		 ntohs(exp->tuple.dst.u.tcp.port));

 	return 0;
 }

 /****************************************************************************/
 static int nat_h245(struct sk_buff *skb, struct nf_conn *ct,
 		    enum ip_conntrack_info ctinfo,
 		    unsigned int protoff, unsigned char **data, int dataoff,
 		    TransportAddress *taddr, __be16 port,
 		    struct nf_conntrack_expect *exp)
 {
 	struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	u_int16_t nated_port = ntohs(port);

 	/* Set expectations for NAT */
 	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 	exp->expectfn = nf_nat_follow_master;
 	exp->dir = !dir;

 	/* Check existing expects */
 	if (info->sig_port[dir] == port)
 		nated_port = ntohs(info->sig_port[!dir]);

 	/* Try to get same port: if not, try to change it. */
 	for (; nated_port != 0; nated_port++) {
 		int ret;

 		exp->tuple.dst.u.tcp.port = htons(nated_port);
 		ret = nf_ct_expect_related(exp);
 		if (ret == 0)
 			break;
 		else if (ret != -EBUSY) {
 			nated_port = 0;
 			break;
 		}
 	}

 	if (nated_port == 0) {	/* No port available */
 		net_notice_ratelimited("nf_nat_q931: out of TCP ports\n");
 		return 0;
 	}

 	/* Modify signal */
 	if (set_h225_addr(skb, protoff, data, dataoff, taddr,
 			  &ct->tuplehash[!dir].tuple.dst.u3,
 			  htons(nated_port)) == 0) {
 		/* Save ports */
 		info->sig_port[dir] = port;
 		info->sig_port[!dir] = htons(nated_port);
 	} else {
 		nf_ct_unexpect_related(exp);
 		return -1;
 	}

 	pr_debug("nf_nat_q931: expect H.245 %pI4:%hu->%pI4:%hu\n",
 		 &exp->tuple.src.u3.ip,
 		 ntohs(exp->tuple.src.u.tcp.port),
 		 &exp->tuple.dst.u3.ip,
 		 ntohs(exp->tuple.dst.u.tcp.port));

 	return 0;
 }

 /****************************************************************************
  * This conntrack expect function replaces nf_conntrack_q931_expect()
  * which was set by nf_conntrack_h323.c.
  ****************************************************************************/
 static void ip_nat_q931_expect(struct nf_conn *new,
 			       struct nf_conntrack_expect *this)
 {
 	struct nf_nat_range range;

 	if (this->tuple.src.u3.ip != 0) {	/* Only accept calls from GK */
 		nf_nat_follow_master(new, this);
 		return;
 	}

 	/* This must be a fresh one. */
 	BUG_ON(new->status & IPS_NAT_DONE_MASK);

 	/* Change src to where master sends to */
 	range.flags = NF_NAT_RANGE_MAP_IPS;
 	range.min_addr = range.max_addr =
 	    new->tuplehash[!this->dir].tuple.src.u3;
 	nf_nat_setup_info(new, &range, NF_NAT_MANIP_SRC);

 	/* For DST manip, map port here to where it's expected. */
 	range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED);
 	range.min_proto = range.max_proto = this->saved_proto;
 	range.min_addr = range.max_addr =
 	    new->master->tuplehash[!this->dir].tuple.src.u3;
 	nf_nat_setup_info(new, &range, NF_NAT_MANIP_DST);
 }

 /****************************************************************************/
 static int nat_q931(struct sk_buff *skb, struct nf_conn *ct,
 		    enum ip_conntrack_info ctinfo,
 		    unsigned int protoff, unsigned char **data,
 		    TransportAddress *taddr, int idx,
 		    __be16 port, struct nf_conntrack_expect *exp)
 {
 	struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	u_int16_t nated_port = ntohs(port);
 	union nf_inet_addr addr;

 	/* Set expectations for NAT */
 	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 	exp->expectfn = ip_nat_q931_expect;
 	exp->dir = !dir;

 	/* Check existing expects */
 	if (info->sig_port[dir] == port)
 		nated_port = ntohs(info->sig_port[!dir]);

 	/* Try to get same port: if not, try to change it. */
 	for (; nated_port != 0; nated_port++) {
 		int ret;

 		exp->tuple.dst.u.tcp.port = htons(nated_port);
 		ret = nf_ct_expect_related(exp);
 		if (ret == 0)
 			break;
 		else if (ret != -EBUSY) {
 			nated_port = 0;
 			break;
 		}
 	}

 	if (nated_port == 0) {	/* No port available */
 		net_notice_ratelimited("nf_nat_ras: out of TCP ports\n");
 		return 0;
 	}

 	/* Modify signal */
 	if (set_h225_addr(skb, protoff, data, 0, &taddr[idx],
 			  &ct->tuplehash[!dir].tuple.dst.u3,
 			  htons(nated_port)) == 0) {
 		/* Save ports */
 		info->sig_port[dir] = port;
 		info->sig_port[!dir] = htons(nated_port);

 		/* Fix for Gnomemeeting */
 		if (idx > 0 &&
 		    get_h225_addr(ct, *data, &taddr[0], &addr, &port) &&
 		    (ntohl(addr.ip) & 0xff000000) == 0x7f000000) {
 			set_h225_addr(skb, protoff, data, 0, &taddr[0],
 				      &ct->tuplehash[!dir].tuple.dst.u3,
 				      info->sig_port[!dir]);
 		}
 	} else {
 		nf_ct_unexpect_related(exp);
 		return -1;
 	}

 	/* Success */
 	pr_debug("nf_nat_ras: expect Q.931 %pI4:%hu->%pI4:%hu\n",
 		 &exp->tuple.src.u3.ip,
 		 ntohs(exp->tuple.src.u.tcp.port),
 		 &exp->tuple.dst.u3.ip,
 		 ntohs(exp->tuple.dst.u.tcp.port));

 	return 0;
 }

 /****************************************************************************/
 static void ip_nat_callforwarding_expect(struct nf_conn *new,
 					 struct nf_conntrack_expect *this)
 {
 	struct nf_nat_range range;

 	/* This must be a fresh one. */
 	BUG_ON(new->status & IPS_NAT_DONE_MASK);

 	/* Change src to where master sends to */
 	range.flags = NF_NAT_RANGE_MAP_IPS;
 	range.min_addr = range.max_addr =
 	    new->tuplehash[!this->dir].tuple.src.u3;
 	nf_nat_setup_info(new, &range, NF_NAT_MANIP_SRC);

 	/* For DST manip, map port here to where it's expected. */
 	range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED);
 	range.min_proto = range.max_proto = this->saved_proto;
 	range.min_addr = range.max_addr = this->saved_addr;
 	nf_nat_setup_info(new, &range, NF_NAT_MANIP_DST);
 }

 /****************************************************************************/
 static int nat_callforwarding(struct sk_buff *skb, struct nf_conn *ct,
 			      enum ip_conntrack_info ctinfo,
 			      unsigned int protoff,
 			      unsigned char **data, int dataoff,
 			      TransportAddress *taddr, __be16 port,
 			      struct nf_conntrack_expect *exp)
 {
 	int dir = CTINFO2DIR(ctinfo);
 	u_int16_t nated_port;

 	/* Set expectations for NAT */
 	exp->saved_addr = exp->tuple.dst.u3;
 	exp->tuple.dst.u3.ip = ct->tuplehash[!dir].tuple.dst.u3.ip;
 	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 	exp->expectfn = ip_nat_callforwarding_expect;
 	exp->dir = !dir;

 	/* Try to get same port: if not, try to change it. */
 	for (nated_port = ntohs(port); nated_port != 0; nated_port++) {
 		int ret;

 		exp->tuple.dst.u.tcp.port = htons(nated_port);
 		ret = nf_ct_expect_related(exp);
 		if (ret == 0)
 			break;
 		else if (ret != -EBUSY) {
 			nated_port = 0;
 			break;
 		}
 	}

 	if (nated_port == 0) {	/* No port available */
 		net_notice_ratelimited("nf_nat_q931: out of TCP ports\n");
 		return 0;
 	}

 	/* Modify signal */
 	if (!set_h225_addr(skb, protoff, data, dataoff, taddr,
 			   &ct->tuplehash[!dir].tuple.dst.u3,
 			   htons(nated_port)) == 0) {
 		nf_ct_unexpect_related(exp);
 		return -1;
 	}

 	/* Success */
 	pr_debug("nf_nat_q931: expect Call Forwarding %pI4:%hu->%pI4:%hu\n",
 		 &exp->tuple.src.u3.ip,
 		 ntohs(exp->tuple.src.u.tcp.port),
 		 &exp->tuple.dst.u3.ip,
 		 ntohs(exp->tuple.dst.u.tcp.port));

 	return 0;
 }

 static struct nf_ct_helper_expectfn q931_nat = {
 	.name		= "Q.931",
 	.expectfn	= ip_nat_q931_expect,
 };

 static struct nf_ct_helper_expectfn callforwarding_nat = {
 	.name		= "callforwarding",
 	.expectfn	= ip_nat_callforwarding_expect,
 };

 /****************************************************************************/
 static int __init init(void)
 {
 	BUG_ON(set_h245_addr_hook != NULL);
 	BUG_ON(set_h225_addr_hook != NULL);
 	BUG_ON(set_sig_addr_hook != NULL);
 	BUG_ON(set_ras_addr_hook != NULL);
 	BUG_ON(nat_rtp_rtcp_hook != NULL);
 	BUG_ON(nat_t120_hook != NULL);
 	BUG_ON(nat_h245_hook != NULL);
 	BUG_ON(nat_callforwarding_hook != NULL);
 	BUG_ON(nat_q931_hook != NULL);

 	RCU_INIT_POINTER(set_h245_addr_hook, set_h245_addr);
 	RCU_INIT_POINTER(set_h225_addr_hook, set_h225_addr);
 	RCU_INIT_POINTER(set_sig_addr_hook, set_sig_addr);
 	RCU_INIT_POINTER(set_ras_addr_hook, set_ras_addr);
 	RCU_INIT_POINTER(nat_rtp_rtcp_hook, nat_rtp_rtcp);
 	RCU_INIT_POINTER(nat_t120_hook, nat_t120);
 	RCU_INIT_POINTER(nat_h245_hook, nat_h245);
 	RCU_INIT_POINTER(nat_callforwarding_hook, nat_callforwarding);
 	RCU_INIT_POINTER(nat_q931_hook, nat_q931);
 	nf_ct_helper_expectfn_register(&q931_nat);
 	nf_ct_helper_expectfn_register(&callforwarding_nat);
 	return 0;
 }

 /****************************************************************************/
 static void __exit fini(void)
 {
 	RCU_INIT_POINTER(set_h245_addr_hook, NULL);
 	RCU_INIT_POINTER(set_h225_addr_hook, NULL);
 	RCU_INIT_POINTER(set_sig_addr_hook, NULL);
 	RCU_INIT_POINTER(set_ras_addr_hook, NULL);
 	RCU_INIT_POINTER(nat_rtp_rtcp_hook, NULL);
 	RCU_INIT_POINTER(nat_t120_hook, NULL);
 	RCU_INIT_POINTER(nat_h245_hook, NULL);
 	RCU_INIT_POINTER(nat_callforwarding_hook, NULL);
 	RCU_INIT_POINTER(nat_q931_hook, NULL);
 	nf_ct_helper_expectfn_unregister(&q931_nat);
 	nf_ct_helper_expectfn_unregister(&callforwarding_nat);
 	synchronize_rcu();
 }

 /****************************************************************************/
 module_init(init);
 module_exit(fini);

 MODULE_AUTHOR("Jing Min Zhao <zhaojingmin@users.sourceforge.net>");
 MODULE_DESCRIPTION("H.323 NAT helper");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("ip_nat_h323");
	/*
	* H.323 extension for NAT alteration.
	*
	* Copyright (c) 2006 Jing Min Zhao <zhaojingmin@users.sourceforge.net>
	* Copyright (c) 2006-2012 Patrick McHardy <kaber@trash.net>
	*
	* This source code is licensed under General Public License version 2.
	*
	* Based on the 'brute force' H.323 NAT module by
	* Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
	*/

	#include <linux/module.h>
	#include <linux/tcp.h>
	#include <net/tcp.h>

	#include <net/netfilter/nf_nat.h>
	#include <net/netfilter/nf_nat_helper.h>
	#include <net/netfilter/nf_conntrack_helper.h>
	#include <net/netfilter/nf_conntrack_expect.h>
	#include <linux/netfilter/nf_conntrack_h323.h>

	/****************************************************************************/
	static int set_addr(struct sk_buff *skb, unsigned int protoff,
	unsigned char **data, int dataoff,
	unsigned int addroff, __be32 ip, __be16 port)
	{
	enum ip_conntrack_info ctinfo;
	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
	struct {
	__be32 ip;
	__be16 port;
	} __attribute__ ((__packed__)) buf;
	const struct tcphdr *th;
	struct tcphdr _tcph;

	buf.ip = ip;
	buf.port = port;
	addroff += dataoff;

	if (ip_hdr(skb)->protocol == IPPROTO_TCP) {
	if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
	protoff, addroff, sizeof(buf),
	(char *) &buf, sizeof(buf))) {
	net_notice_ratelimited("nf_nat_h323: nf_nat_mangle_tcp_packet error\n");
	return -1;
	}

	/* Relocate data pointer */
	th = skb_header_pointer(skb, ip_hdrlen(skb),
	sizeof(_tcph), &_tcph);
	if (th == NULL)
	return -1;
	data = skb->data + ip_hdrlen(skb) + th->doff 4 + dataoff;
	} else {
	if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo,
	protoff, addroff, sizeof(buf),
	(char *) &buf, sizeof(buf))) {
	net_notice_ratelimited("nf_nat_h323: nf_nat_mangle_udp_packet error\n");
	return -1;
	}
	/* nf_nat_mangle_udp_packet uses skb_make_writable() to copy
	* or pull everything in a linear buffer, so we can safely
	* use the skb pointers now */
	*data = skb->data + ip_hdrlen(skb) + sizeof(struct udphdr);
	}

	return 0;
	}

	/****************************************************************************/
	static int set_h225_addr(struct sk_buff *skb, unsigned int protoff,
	unsigned char **data, int dataoff,
	TransportAddress *taddr,
	union nf_inet_addr *addr, __be16 port)
	{
	return set_addr(skb, protoff, data, dataoff, taddr->ipAddress.ip,
	addr->ip, port);
	}

	/****************************************************************************/
	static int set_h245_addr(struct sk_buff *skb, unsigned protoff,
	unsigned char **data, int dataoff,
	H245_TransportAddress *taddr,
	union nf_inet_addr *addr, __be16 port)
	{
	return set_addr(skb, protoff, data, dataoff,
	taddr->unicastAddress.iPAddress.network,
	addr->ip, port);
	}

	/****************************************************************************/
	static int set_sig_addr(struct sk_buff skb, struct nf_conn ct,
	enum ip_conntrack_info ctinfo,
	unsigned int protoff, unsigned char **data,
	TransportAddress *taddr, int count)
	{
	const struct nf_ct_h323_master *info = nfct_help_data(ct);
	int dir = CTINFO2DIR(ctinfo);
	int i;
	__be16 port;
	union nf_inet_addr addr;

	for (i = 0; i < count; i++) {
	if (get_h225_addr(ct, *data, &taddr[i], &addr, &port)) {
	if (addr.ip == ct->tuplehash[dir].tuple.src.u3.ip &&
	port == info->sig_port[dir]) {
	/* GW->GK */

	/* Fix for Gnomemeeting */
	if (i > 0 &&
	get_h225_addr(ct, *data, &taddr[0],
	&addr, &port) &&
	(ntohl(addr.ip) & 0xff000000) == 0x7f000000)
	i = 0;

	pr_debug("nf_nat_ras: set signal address %pI4:%hu->%pI4:%hu\n",
	&addr.ip, port,
	&ct->tuplehash[!dir].tuple.dst.u3.ip,
	info->sig_port[!dir]);
	return set_h225_addr(skb, protoff, data, 0,
	&taddr[i],
	&ct->tuplehash[!dir].
	tuple.dst.u3,
	info->sig_port[!dir]);
	} else if (addr.ip == ct->tuplehash[dir].tuple.dst.u3.ip &&
	port == info->sig_port[dir]) {
	/* GK->GW */
	pr_debug("nf_nat_ras: set signal address %pI4:%hu->%pI4:%hu\n",
	&addr.ip, port,
	&ct->tuplehash[!dir].tuple.src.u3.ip,
	info->sig_port[!dir]);
	return set_h225_addr(skb, protoff, data, 0,
	&taddr[i],
	&ct->tuplehash[!dir].
	tuple.src.u3,
	info->sig_port[!dir]);
	}
	}
	}

	return 0;
	}

	/****************************************************************************/
	static int set_ras_addr(struct sk_buff skb, struct nf_conn ct,
	enum ip_conntrack_info ctinfo,
	unsigned int protoff, unsigned char **data,
	TransportAddress *taddr, int count)
	{
	int dir = CTINFO2DIR(ctinfo);
	int i;
	__be16 port;
	union nf_inet_addr addr;

	for (i = 0; i < count; i++) {
	if (get_h225_addr(ct, *data, &taddr[i], &addr, &port) &&
	addr.ip == ct->tuplehash[dir].tuple.src.u3.ip &&
	port == ct->tuplehash[dir].tuple.src.u.udp.port) {
	pr_debug("nf_nat_ras: set rasAddress %pI4:%hu->%pI4:%hu\n",
	&addr.ip, ntohs(port),
	&ct->tuplehash[!dir].tuple.dst.u3.ip,
	ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port));
	return set_h225_addr(skb, protoff, data, 0, &taddr[i],
	&ct->tuplehash[!dir].tuple.dst.u3,
	ct->tuplehash[!dir].tuple.
	dst.u.udp.port);
	}
	}

	return 0;
	}

	/****************************************************************************/
	static int nat_rtp_rtcp(struct sk_buff skb, struct nf_conn ct,
	enum ip_conntrack_info ctinfo,
	unsigned int protoff, unsigned char **data, int dataoff,
	H245_TransportAddress *taddr,
	__be16 port, __be16 rtp_port,
	struct nf_conntrack_expect *rtp_exp,
	struct nf_conntrack_expect *rtcp_exp)
	{
	struct nf_ct_h323_master *info = nfct_help_data(ct);
	int dir = CTINFO2DIR(ctinfo);
	int i;
	u_int16_t nated_port;

	/* Set expectations for NAT */
	rtp_exp->saved_proto.udp.port = rtp_exp->tuple.dst.u.udp.port;
	rtp_exp->expectfn = nf_nat_follow_master;
	rtp_exp->dir = !dir;
	rtcp_exp->saved_proto.udp.port = rtcp_exp->tuple.dst.u.udp.port;
	rtcp_exp->expectfn = nf_nat_follow_master;
	rtcp_exp->dir = !dir;

	/* Lookup existing expects */
	for (i = 0; i < H323_RTP_CHANNEL_MAX; i++) {
	if (info->rtp_port[i][dir] == rtp_port) {
	/* Expected */

	/* Use allocated ports first. This will refresh
	* the expects */
	rtp_exp->tuple.dst.u.udp.port = info->rtp_port[i][dir];
	rtcp_exp->tuple.dst.u.udp.port =
	htons(ntohs(info->rtp_port[i][dir]) + 1);
	break;
	} else if (info->rtp_port[i][dir] == 0) {
	/* Not expected */
	break;
	}
	}

	/* Run out of expectations */
	if (i >= H323_RTP_CHANNEL_MAX) {
	net_notice_ratelimited("nf_nat_h323: out of expectations\n");
	return 0;
	}

	/* Try to get a pair of ports. */
	for (nated_port = ntohs(rtp_exp->tuple.dst.u.udp.port);
	nated_port != 0; nated_port += 2) {
	int ret;

	rtp_exp->tuple.dst.u.udp.port = htons(nated_port);
	ret = nf_ct_expect_related(rtp_exp);
	if (ret == 0) {
	rtcp_exp->tuple.dst.u.udp.port =
	htons(nated_port + 1);
	ret = nf_ct_expect_related(rtcp_exp);
	if (ret == 0)
	break;
	else if (ret == -EBUSY) {
	nf_ct_unexpect_related(rtp_exp);
	continue;
	} else if (ret < 0) {
	nf_ct_unexpect_related(rtp_exp);
	nated_port = 0;
	break;
	}
	} else if (ret != -EBUSY) {
	nated_port = 0;
	break;
	}
	}

	if (nated_port == 0) { /* No port available */
	net_notice_ratelimited("nf_nat_h323: out of RTP ports\n");
	return 0;
	}

	/* Modify signal */
	if (set_h245_addr(skb, protoff, data, dataoff, taddr,
	&ct->tuplehash[!dir].tuple.dst.u3,
	htons((port & htons(1)) ? nated_port + 1 :
	nated_port)) == 0) {
	/* Save ports */
	info->rtp_port[i][dir] = rtp_port;
	info->rtp_port[i][!dir] = htons(nated_port);
	} else {
	nf_ct_unexpect_related(rtp_exp);
	nf_ct_unexpect_related(rtcp_exp);
	return -1;
	}

	/* Success */
	pr_debug("nf_nat_h323: expect RTP %pI4:%hu->%pI4:%hu\n",
	&rtp_exp->tuple.src.u3.ip,
	ntohs(rtp_exp->tuple.src.u.udp.port),
	&rtp_exp->tuple.dst.u3.ip,
	ntohs(rtp_exp->tuple.dst.u.udp.port));
	pr_debug("nf_nat_h323: expect RTCP %pI4:%hu->%pI4:%hu\n",
	&rtcp_exp->tuple.src.u3.ip,
	ntohs(rtcp_exp->tuple.src.u.udp.port),
	&rtcp_exp->tuple.dst.u3.ip,
	ntohs(rtcp_exp->tuple.dst.u.udp.port));

	return 0;
	}

	/****************************************************************************/
	static int nat_t120(struct sk_buff skb, struct nf_conn ct,
	enum ip_conntrack_info ctinfo,
	unsigned int protoff, unsigned char **data, int dataoff,
	H245_TransportAddress *taddr, __be16 port,
	struct nf_conntrack_expect *exp)
	{
	int dir = CTINFO2DIR(ctinfo);
	u_int16_t nated_port = ntohs(port);

	/* Set expectations for NAT */
	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
	exp->expectfn = nf_nat_follow_master;
	exp->dir = !dir;

	/* Try to get same port: if not, try to change it. */
	for (; nated_port != 0; nated_port++) {
	int ret;

	exp->tuple.dst.u.tcp.port = htons(nated_port);
	ret = nf_ct_expect_related(exp);
	if (ret == 0)
	break;
	else if (ret != -EBUSY) {
	nated_port = 0;
	break;
	}
	}

	if (nated_port == 0) { /* No port available */
	net_notice_ratelimited("nf_nat_h323: out of TCP ports\n");
	return 0;
	}

	/* Modify signal */
	if (set_h245_addr(skb, protoff, data, dataoff, taddr,
	&ct->tuplehash[!dir].tuple.dst.u3,
	htons(nated_port)) < 0) {
	nf_ct_unexpect_related(exp);
	return -1;
	}

	pr_debug("nf_nat_h323: expect T.120 %pI4:%hu->%pI4:%hu\n",
	&exp->tuple.src.u3.ip,
	ntohs(exp->tuple.src.u.tcp.port),
	&exp->tuple.dst.u3.ip,
	ntohs(exp->tuple.dst.u.tcp.port));

	return 0;
	}

	/****************************************************************************/
	static int nat_h245(struct sk_buff skb, struct nf_conn ct,
	enum ip_conntrack_info ctinfo,
	unsigned int protoff, unsigned char **data, int dataoff,
	TransportAddress *taddr, __be16 port,
	struct nf_conntrack_expect *exp)
	{
	struct nf_ct_h323_master *info = nfct_help_data(ct);
	int dir = CTINFO2DIR(ctinfo);
	u_int16_t nated_port = ntohs(port);

	/* Set expectations for NAT */
	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
	exp->expectfn = nf_nat_follow_master;
	exp->dir = !dir;

	/* Check existing expects */
	if (info->sig_port[dir] == port)
	nated_port = ntohs(info->sig_port[!dir]);

	/* Try to get same port: if not, try to change it. */
	for (; nated_port != 0; nated_port++) {
	int ret;

	exp->tuple.dst.u.tcp.port = htons(nated_port);
	ret = nf_ct_expect_related(exp);
	if (ret == 0)
	break;
	else if (ret != -EBUSY) {
	nated_port = 0;
	break;
	}
	}

	if (nated_port == 0) { /* No port available */
	net_notice_ratelimited("nf_nat_q931: out of TCP ports\n");
	return 0;
	}

	/* Modify signal */
	if (set_h225_addr(skb, protoff, data, dataoff, taddr,
	&ct->tuplehash[!dir].tuple.dst.u3,
	htons(nated_port)) == 0) {
	/* Save ports */
	info->sig_port[dir] = port;
	info->sig_port[!dir] = htons(nated_port);
	} else {
	nf_ct_unexpect_related(exp);
	return -1;
	}

	pr_debug("nf_nat_q931: expect H.245 %pI4:%hu->%pI4:%hu\n",
	&exp->tuple.src.u3.ip,
	ntohs(exp->tuple.src.u.tcp.port),
	&exp->tuple.dst.u3.ip,
	ntohs(exp->tuple.dst.u.tcp.port));

	return 0;
	}

	/****************************************************************************
	* This conntrack expect function replaces nf_conntrack_q931_expect()
	* which was set by nf_conntrack_h323.c.
	****************************************************************************/
	static void ip_nat_q931_expect(struct nf_conn *new,
	struct nf_conntrack_expect *this)
	{
	struct nf_nat_range range;

	if (this->tuple.src.u3.ip != 0) { /* Only accept calls from GK */
	nf_nat_follow_master(new, this);
	return;
	}

	/* This must be a fresh one. */
	BUG_ON(new->status & IPS_NAT_DONE_MASK);

	/* Change src to where master sends to */
	range.flags = NF_NAT_RANGE_MAP_IPS;
	range.min_addr = range.max_addr =
	new->tuplehash[!this->dir].tuple.src.u3;
	nf_nat_setup_info(new, &range, NF_NAT_MANIP_SRC);

	/* For DST manip, map port here to where it's expected. */
	range.flags = (NF_NAT_RANGE_MAP_IPS \| NF_NAT_RANGE_PROTO_SPECIFIED);
	range.min_proto = range.max_proto = this->saved_proto;
	range.min_addr = range.max_addr =
	new->master->tuplehash[!this->dir].tuple.src.u3;
	nf_nat_setup_info(new, &range, NF_NAT_MANIP_DST);
	}

	/****************************************************************************/
	static int nat_q931(struct sk_buff skb, struct nf_conn ct,
	enum ip_conntrack_info ctinfo,
	unsigned int protoff, unsigned char **data,
	TransportAddress *taddr, int idx,
	__be16 port, struct nf_conntrack_expect *exp)
	{
	struct nf_ct_h323_master *info = nfct_help_data(ct);
	int dir = CTINFO2DIR(ctinfo);
	u_int16_t nated_port = ntohs(port);
	union nf_inet_addr addr;

	/* Set expectations for NAT */
	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
	exp->expectfn = ip_nat_q931_expect;
	exp->dir = !dir;

	/* Check existing expects */
	if (info->sig_port[dir] == port)
	nated_port = ntohs(info->sig_port[!dir]);

	/* Try to get same port: if not, try to change it. */
	for (; nated_port != 0; nated_port++) {
	int ret;

	exp->tuple.dst.u.tcp.port = htons(nated_port);
	ret = nf_ct_expect_related(exp);
	if (ret == 0)
	break;
	else if (ret != -EBUSY) {
	nated_port = 0;
	break;
	}
	}

	if (nated_port == 0) { /* No port available */
	net_notice_ratelimited("nf_nat_ras: out of TCP ports\n");
	return 0;
	}

	/* Modify signal */
	if (set_h225_addr(skb, protoff, data, 0, &taddr[idx],
	&ct->tuplehash[!dir].tuple.dst.u3,
	htons(nated_port)) == 0) {
	/* Save ports */
	info->sig_port[dir] = port;
	info->sig_port[!dir] = htons(nated_port);

	/* Fix for Gnomemeeting */
	if (idx > 0 &&
	get_h225_addr(ct, *data, &taddr[0], &addr, &port) &&
	(ntohl(addr.ip) & 0xff000000) == 0x7f000000) {
	set_h225_addr(skb, protoff, data, 0, &taddr[0],
	&ct->tuplehash[!dir].tuple.dst.u3,
	info->sig_port[!dir]);
	}
	} else {
	nf_ct_unexpect_related(exp);
	return -1;
	}

	/* Success */
	pr_debug("nf_nat_ras: expect Q.931 %pI4:%hu->%pI4:%hu\n",
	&exp->tuple.src.u3.ip,
	ntohs(exp->tuple.src.u.tcp.port),
	&exp->tuple.dst.u3.ip,
	ntohs(exp->tuple.dst.u.tcp.port));

	return 0;
	}

	/****************************************************************************/
	static void ip_nat_callforwarding_expect(struct nf_conn *new,
	struct nf_conntrack_expect *this)
	{
	struct nf_nat_range range;

	/* This must be a fresh one. */
	BUG_ON(new->status & IPS_NAT_DONE_MASK);

	/* Change src to where master sends to */
	range.flags = NF_NAT_RANGE_MAP_IPS;
	range.min_addr = range.max_addr =
	new->tuplehash[!this->dir].tuple.src.u3;
	nf_nat_setup_info(new, &range, NF_NAT_MANIP_SRC);

	/* For DST manip, map port here to where it's expected. */
	range.flags = (NF_NAT_RANGE_MAP_IPS \| NF_NAT_RANGE_PROTO_SPECIFIED);
	range.min_proto = range.max_proto = this->saved_proto;
	range.min_addr = range.max_addr = this->saved_addr;
	nf_nat_setup_info(new, &range, NF_NAT_MANIP_DST);
	}

	/****************************************************************************/
	static int nat_callforwarding(struct sk_buff skb, struct nf_conn ct,
	enum ip_conntrack_info ctinfo,
	unsigned int protoff,
	unsigned char **data, int dataoff,
	TransportAddress *taddr, __be16 port,
	struct nf_conntrack_expect *exp)
	{
	int dir = CTINFO2DIR(ctinfo);
	u_int16_t nated_port;

	/* Set expectations for NAT */
	exp->saved_addr = exp->tuple.dst.u3;
	exp->tuple.dst.u3.ip = ct->tuplehash[!dir].tuple.dst.u3.ip;
	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
	exp->expectfn = ip_nat_callforwarding_expect;
	exp->dir = !dir;

	/* Try to get same port: if not, try to change it. */
	for (nated_port = ntohs(port); nated_port != 0; nated_port++) {
	int ret;

	exp->tuple.dst.u.tcp.port = htons(nated_port);
	ret = nf_ct_expect_related(exp);
	if (ret == 0)
	break;
	else if (ret != -EBUSY) {
	nated_port = 0;
	break;
	}
	}

	if (nated_port == 0) { /* No port available */
	net_notice_ratelimited("nf_nat_q931: out of TCP ports\n");
	return 0;
	}

	/* Modify signal */
	if (!set_h225_addr(skb, protoff, data, dataoff, taddr,
	&ct->tuplehash[!dir].tuple.dst.u3,
	htons(nated_port)) == 0) {
	nf_ct_unexpect_related(exp);
	return -1;
	}

	/* Success */
	pr_debug("nf_nat_q931: expect Call Forwarding %pI4:%hu->%pI4:%hu\n",
	&exp->tuple.src.u3.ip,
	ntohs(exp->tuple.src.u.tcp.port),
	&exp->tuple.dst.u3.ip,
	ntohs(exp->tuple.dst.u.tcp.port));

	return 0;
	}

	static struct nf_ct_helper_expectfn q931_nat = {
	.name = "Q.931",
	.expectfn = ip_nat_q931_expect,
	};

	static struct nf_ct_helper_expectfn callforwarding_nat = {
	.name = "callforwarding",
	.expectfn = ip_nat_callforwarding_expect,
	};

	/****************************************************************************/
	static int __init init(void)
	{
	BUG_ON(set_h245_addr_hook != NULL);
	BUG_ON(set_h225_addr_hook != NULL);
	BUG_ON(set_sig_addr_hook != NULL);
	BUG_ON(set_ras_addr_hook != NULL);
	BUG_ON(nat_rtp_rtcp_hook != NULL);
	BUG_ON(nat_t120_hook != NULL);
	BUG_ON(nat_h245_hook != NULL);
	BUG_ON(nat_callforwarding_hook != NULL);
	BUG_ON(nat_q931_hook != NULL);

	RCU_INIT_POINTER(set_h245_addr_hook, set_h245_addr);
	RCU_INIT_POINTER(set_h225_addr_hook, set_h225_addr);
	RCU_INIT_POINTER(set_sig_addr_hook, set_sig_addr);
	RCU_INIT_POINTER(set_ras_addr_hook, set_ras_addr);
	RCU_INIT_POINTER(nat_rtp_rtcp_hook, nat_rtp_rtcp);
	RCU_INIT_POINTER(nat_t120_hook, nat_t120);
	RCU_INIT_POINTER(nat_h245_hook, nat_h245);
	RCU_INIT_POINTER(nat_callforwarding_hook, nat_callforwarding);
	RCU_INIT_POINTER(nat_q931_hook, nat_q931);
	nf_ct_helper_expectfn_register(&q931_nat);
	nf_ct_helper_expectfn_register(&callforwarding_nat);
	return 0;
	}

	/****************************************************************************/
	static void __exit fini(void)
	{
	RCU_INIT_POINTER(set_h245_addr_hook, NULL);
	RCU_INIT_POINTER(set_h225_addr_hook, NULL);
	RCU_INIT_POINTER(set_sig_addr_hook, NULL);
	RCU_INIT_POINTER(set_ras_addr_hook, NULL);
	RCU_INIT_POINTER(nat_rtp_rtcp_hook, NULL);
	RCU_INIT_POINTER(nat_t120_hook, NULL);
	RCU_INIT_POINTER(nat_h245_hook, NULL);
	RCU_INIT_POINTER(nat_callforwarding_hook, NULL);
	RCU_INIT_POINTER(nat_q931_hook, NULL);
	nf_ct_helper_expectfn_unregister(&q931_nat);
	nf_ct_helper_expectfn_unregister(&callforwarding_nat);
	synchronize_rcu();
	}

	/****************************************************************************/
	module_init(init);
	module_exit(fini);

	MODULE_AUTHOR("Jing Min Zhao <zhaojingmin@users.sourceforge.net>");
	MODULE_DESCRIPTION("H.323 NAT helper");
	MODULE_LICENSE("GPL");
	MODULE_ALIAS("ip_nat_h323");