Add SIP connection tracking helpers.

Update 2.6 kernel configuration to build SIP connection tracking helper
Add informations in menuconfig


git-svn-id: svn://svn.openwrt.org/openwrt/trunk/openwrt@3627 3c298f89-4303-0410-b956-a3cf2f4a3e73

1 files changed, 830 insertions, 0 deletions

diff --git a/target/linux/generic-2.6/patches/107-netfilter_nat_sip.patch b/target/linux/generic-2.6/patches/107-netfilter_nat_sip.patch
new file mode 100644
index 0000000000..6640118f20
--- /dev/null
+++ b/target/linux/generic-2.6/patches/107-netfilter_nat_sip.patch
@@ -0,0 +1,830 @@
+diff -urN linux-2.6.16.4/net/ipv4/netfilter/ip_conntrack_sip.c linux-2.6.16.4.new/net/ipv4/netfilter/ip_conntrack_sip.c
+--- linux-2.6.16.4/net/ipv4/netfilter/ip_conntrack_sip.c	1970-01-01 01:00:00.000000000 +0100
++++ linux-2.6.16.4.new/net/ipv4/netfilter/ip_conntrack_sip.c	2006-04-12 17:31:44.000000000 +0200
+@@ -0,0 +1,414 @@
++/* SIP extension for IP connection tracking.
++ *
++ * (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar>
++ * based on RR's ip_conntrack_ftp.c and other modules.
++ *
++ * This program is free software; you can redistribute it and/or modify
++ * it under the terms of the GNU General Public License version 2 as
++ * published by the Free Software Foundation.
++ */
++
++#include <linux/config.h>
++#include <linux/module.h>
++#include <linux/netfilter.h>
++#include <linux/ip.h>
++#include <linux/ctype.h>
++#include <linux/in.h>
++#include <linux/udp.h>
++#include <net/checksum.h>
++#include <net/udp.h>
++
++#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
++#include <linux/netfilter_ipv4/ip_conntrack_sip.h>
++
++MODULE_LICENSE("GPL");
++MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
++MODULE_DESCRIPTION("SIP connection tracking helper");
++
++static DEFINE_SPINLOCK(sipbf_lock);
++
++
++#define MAX_PORTS	8
++static int ports[MAX_PORTS];
++static int ports_c;
++module_param_array(ports, int, &ports_c, 0400);
++MODULE_PARM_DESC(ports, " port numbers of sip servers");
++
++static unsigned int sip_timeout = SIP_TIMEOUT;
++
++module_param(sip_timeout, int, 0600);
++MODULE_PARM_DESC(sip_timeout, "timeout for the master sip session");
++
++unsigned int (*ip_nat_sip_hook)(struct sk_buff **pskb, 
++				enum ip_conntrack_info ctinfo,
++				struct ip_conntrack *ct,
++				const char **dptr);
++EXPORT_SYMBOL_GPL(ip_nat_sip_hook);
++				
++unsigned int (*ip_nat_sdp_hook)(struct sk_buff **pskb, 
++				enum ip_conntrack_info ctinfo,
++				struct ip_conntrack_expect *exp,
++				const char *dptr);
++EXPORT_SYMBOL_GPL(ip_nat_sdp_hook);
++
++int ct_sip_get_info(const char *dptr, size_t dlen, 
++				unsigned int *matchoff, 
++				unsigned int *matchlen, 
++				struct sip_header_nfo *hnfo);
++EXPORT_SYMBOL(ct_sip_get_info);
++
++#if 0
++#define DEBUGP printk
++#else
++#define DEBUGP(format, args...)
++#endif
++
++static int digits_len(const char *dptr, const char *limit, int *shift);
++static int epaddr_len(const char *dptr, const char *limit, int *shift);
++static int skp_digits_len(const char *dptr, const char *limit, int *shift);
++static int skp_epaddr_len(const char *dptr, const char *limit, int *shift);
++
++struct sip_header_nfo ct_sip_hdrs[] = {
++	{ 	/* Via header */
++		"Via:",		sizeof("Via:") - 1,
++		"\r\nv:",	sizeof("\r\nv:") - 1, /* rfc3261 "\r\n" */
++		"UDP ", 	sizeof("UDP ") - 1,
++		epaddr_len
++	},
++	{ 	/* Contact header */
++		"Contact:",	sizeof("Contact:") - 1,
++		"\r\nm:",	sizeof("\r\nm:") - 1,
++		"sip:",		sizeof("sip:") - 1,
++		skp_epaddr_len
++	},
++	{ 	/* Content length header */
++		"Content-Length:", sizeof("Content-Length:") - 1,
++		"\r\nl:",	sizeof("\r\nl:") - 1,
++		":",		sizeof(":") - 1, 
++		skp_digits_len
++	},
++	{	/* SDP media info */
++		"\nm=",		sizeof("\nm=") - 1,	
++		"\rm=",		sizeof("\rm=") - 1,
++		"audio ",	sizeof("audio ") - 1,
++		digits_len
++	},
++	{ 	/* SDP owner address*/	
++		"\no=",		sizeof("\no=") - 1, 
++		"\ro=",		sizeof("\ro=") - 1,
++		"IN IP4 ",	sizeof("IN IP4 ") - 1,
++		epaddr_len
++	},
++	{ 	/* SDP connection info */
++		"\nc=",		sizeof("\nc=") - 1, 
++		"\rc=",		sizeof("\rc=") - 1,
++		"IN IP4 ",	sizeof("IN IP4 ") - 1,
++		epaddr_len
++	},
++	{ 	/* Requests headers */
++		"sip:",		sizeof("sip:") - 1,
++		"sip:",		sizeof("sip:") - 1, /* yes, i know.. ;) */
++		"@", 		sizeof("@") - 1, 
++		epaddr_len
++	},
++	{ 	/* SDP version header */
++		"\nv=",		sizeof("\nv=") - 1,
++		"\rv=",		sizeof("\rv=") - 1,
++		"=", 		sizeof("=") - 1, 
++		digits_len
++	}
++};
++EXPORT_SYMBOL(ct_sip_hdrs);
++
++
++static int digits_len(const char *dptr, const char *limit, int *shift)
++{
++	int len = 0;	
++	while (dptr <= limit && isdigit(*dptr)) {
++		dptr++;
++		len++;
++	}
++	return len;
++} 
++
++/* get digits lenght, skiping blank spaces. */
++static int skp_digits_len(const char *dptr, const char *limit, int *shift)
++{
++	for (; dptr <= limit && *dptr == ' '; dptr++)
++		(*shift)++;
++		
++	return digits_len(dptr, limit, shift);
++}
++
++/* Simple ipaddr parser.. */
++static int parse_ipaddr(const char *cp,	const char **endp, 
++			uint32_t *ipaddr, const char *limit)
++{
++	unsigned long int val;
++	int i, digit = 0;
++	
++	for (i = 0, *ipaddr = 0; cp <= limit && i < 4; i++) {
++		digit = 0;
++		if (!isdigit(*cp))
++			break;
++		
++		val = simple_strtoul(cp, (char **)&cp, 10);
++		if (val > 0xFF)
++			return -1;
++	
++		((uint8_t *)ipaddr)[i] = val;	
++		digit = 1;
++	
++		if (*cp != '.')
++			break;
++		cp++;
++	}
++	if (!digit)
++		return -1;
++	
++	if (endp)
++		*endp = cp;
++
++	return 0;
++}
++
++/* skip ip address. returns it lenght. */
++static int epaddr_len(const char *dptr, const char *limit, int *shift)
++{
++	const char *aux = dptr;
++	uint32_t ip;
++	
++	if (parse_ipaddr(dptr, &dptr, &ip, limit) < 0) {
++		DEBUGP("ip: %s parse failed.!\n", dptr);
++		return 0;
++	}
++
++	/* Port number */
++	if (*dptr == ':') {
++		dptr++;
++		dptr += digits_len(dptr, limit, shift);
++	}
++	return dptr - aux;
++}
++
++/* get address lenght, skiping user info. */
++static int skp_epaddr_len(const char *dptr, const char *limit, int *shift)
++{
++	for (; dptr <= limit && *dptr != '@'; dptr++)
++		(*shift)++;	
++	
++	if (*dptr == '@') {
++		dptr++;
++		(*shift)++;
++		return epaddr_len(dptr, limit, shift);
++	}	
++	return  0;
++}
++
++/* Returns 0 if not found, -1 error parsing. */
++int ct_sip_get_info(const char *dptr, size_t dlen, 
++		unsigned int *matchoff, 
++		unsigned int *matchlen,
++		struct sip_header_nfo *hnfo)
++{
++	const char *limit, *aux, *k = dptr;
++	int shift = 0;
++	
++	limit = dptr + (dlen - hnfo->lnlen);
++
++	while (dptr <= limit) {
++		if ((strncmp(dptr, hnfo->lname, hnfo->lnlen) != 0) &&
++			(strncmp(dptr, hnfo->sname, hnfo->snlen) != 0))
++		{
++			dptr++;
++			continue;
++		}
++		aux = ct_sip_search(hnfo->ln_str, dptr, hnfo->ln_strlen, 
++						ct_sip_lnlen(dptr, limit));
++		if (!aux) {
++			DEBUGP("'%s' not found in '%s'.\n", hnfo->ln_str, hnfo->lname);
++			return -1;
++		}
++		aux += hnfo->ln_strlen;
++		
++		*matchlen = hnfo->match_len(aux, limit, &shift);
++		if (!*matchlen)
++			return -1;
++
++		*matchoff = (aux - k) + shift; 
++		
++		DEBUGP("%s match succeeded! - len: %u\n", hnfo->lname, *matchlen);
++		return 1;
++	}
++	DEBUGP("%s header not found.\n", hnfo->lname);
++	return 0;
++}
++
++static int set_expected_rtp(struct sk_buff **pskb, 
++			struct ip_conntrack *ct,
++			enum ip_conntrack_info ctinfo, 
++			uint32_t ipaddr, uint16_t port,
++			const char *dptr)
++{
++	struct ip_conntrack_expect *exp;
++	int ret;
++	
++	exp = ip_conntrack_expect_alloc(ct);
++	if (exp == NULL)
++		return NF_DROP;
++
++	exp->tuple = ((struct ip_conntrack_tuple)
++		{ { ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip, { 0 } },
++		  { ipaddr, { .udp = { htons(port) } }, IPPROTO_UDP }});
++		  
++	exp->mask = ((struct ip_conntrack_tuple) 
++		{ { 0xFFFFFFFF, { 0 } },
++		  { 0xFFFFFFFF, { .udp = { 0xFFFF } }, 0xFF }});
++	
++	exp->expectfn = NULL;
++	
++	if (ip_nat_sdp_hook)
++		ret = ip_nat_sdp_hook(pskb, ctinfo, exp, dptr);
++	else {
++		if (ip_conntrack_expect_related(exp) != 0)
++			ret = NF_DROP;
++		else
++			ret = NF_ACCEPT;
++	}
++	ip_conntrack_expect_put(exp);
++
++	return ret;
++}
++
++static int sip_help(struct sk_buff **pskb,
++		struct ip_conntrack *ct,
++		enum ip_conntrack_info ctinfo)
++{
++	unsigned int dataoff, datalen;
++	const char *dptr;
++	int ret = NF_ACCEPT;
++	int matchoff, matchlen;
++	uint32_t ipaddr;
++	uint16_t port;
++	
++	/* No Data ? */ 
++	dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
++	if (dataoff >= (*pskb)->len) {
++		DEBUGP("skb->len = %u\n", (*pskb)->len);
++		return NF_ACCEPT;
++        }
++        
++	ip_ct_refresh(ct, *pskb, sip_timeout * HZ);
++		
++	spin_lock_bh(&sipbf_lock);
++	
++	if ((dataoff + (*pskb)->len - dataoff) <= skb_headlen(*pskb))
++		dptr = (*pskb)->data + dataoff;
++	else {
++		DEBUGP("Copy of skbuff not supported yet.\n");
++		goto out;
++	}
++	
++	if (ip_nat_sip_hook) {
++		if (!ip_nat_sip_hook(pskb, ctinfo, ct, &dptr)) {
++			ret = NF_DROP;
++			goto out;
++		}
++	}
++	
++	if ((ctinfo) >= IP_CT_IS_REPLY)
++		goto out;
++
++	/* After this point NAT, could have mangled skb, so 
++	   we need to recalculate payload lenght. */
++	datalen = (*pskb)->len - dataoff;
++
++	if (datalen < (sizeof("SIP/2.0 200") - 1))
++		goto out;
++	
++	/* RTP info only in some SDP pkts */
++	if (memcmp(dptr, "INVITE", sizeof("INVITE") - 1) != 0 && 
++	    memcmp(dptr, "SIP/2.0 200", sizeof("SIP/2.0 200") - 1) != 0) {
++		goto out;
++	}
++	/* Get ip and port address from SDP packet. */
++	if (ct_sip_get_info(dptr, datalen, &matchoff, &matchlen, 
++	    &ct_sip_hdrs[POS_CONECTION]) > 0) {
++
++		/* We'll drop only if there are parse problems. */
++		if (parse_ipaddr(dptr + matchoff, NULL, &ipaddr, 
++		    dptr + datalen) < 0) {
++			ret = NF_DROP;
++			goto out;
++		}
++		if (ct_sip_get_info(dptr, datalen, &matchoff, &matchlen, 
++		    &ct_sip_hdrs[POS_MEDIA]) > 0) {
++
++			port = simple_strtoul(dptr + matchoff, NULL, 10);
++			if (port < 1024) {
++				ret = NF_DROP;
++				goto out;
++			}
++			ret = set_expected_rtp(pskb, ct, ctinfo,
++						ipaddr, port, dptr);
++		}
++	}
++out:	spin_unlock_bh(&sipbf_lock);
++	return ret;
++}
++
++static struct ip_conntrack_helper sip[MAX_PORTS];
++static char sip_names[MAX_PORTS][10];
++
++static void fini(void)
++{
++	int i = 0;
++	for (; i < ports_c; i++) {
++		DEBUGP("unregistering helper for port %d\n", ports[i]);
++		ip_conntrack_helper_unregister(&sip[i]);
++	} 
++}
++
++static int __init init(void)
++{
++	int i, ret;
++	char *tmpname;
++
++	if (ports_c == 0)
++		ports[ports_c++] = SIP_PORT;
++
++	for (i = 0; i < ports_c; i++) {
++		/* Create helper structure */
++		memset(&sip[i], 0, sizeof(struct ip_conntrack_helper));
++
++		sip[i].tuple.dst.protonum = IPPROTO_UDP;
++		sip[i].tuple.src.u.udp.port = htons(ports[i]);
++		sip[i].mask.src.u.udp.port = 0xFFFF;
++		sip[i].mask.dst.protonum = 0xFF;
++		sip[i].max_expected = 1;
++		sip[i].timeout = 3 * 60; /* 3 minutes */
++		sip[i].me = THIS_MODULE;
++		sip[i].help = sip_help;
++
++		tmpname = &sip_names[i][0];
++		if (ports[i] == SIP_PORT)
++			sprintf(tmpname, "sip");
++		else
++			sprintf(tmpname, "sip-%d", i);
++		sip[i].name = tmpname;
++
++		DEBUGP("port #%d: %d\n", i, ports[i]);
++
++		ret=ip_conntrack_helper_register(&sip[i]);
++		if (ret) {
++			printk("ERROR registering helper for port %d\n",
++				ports[i]);
++			fini();
++			return(ret);
++		}
++	}
++	return(0);
++}
++
++module_init(init);
++module_exit(fini);
+diff -urN linux-2.6.16.4/net/ipv4/netfilter/ip_nat_sip.c linux-2.6.16.4.new/net/ipv4/netfilter/ip_nat_sip.c
+--- linux-2.6.16.4/net/ipv4/netfilter/ip_nat_sip.c	1970-01-01 01:00:00.000000000 +0100
++++ linux-2.6.16.4.new/net/ipv4/netfilter/ip_nat_sip.c	2006-04-12 17:31:53.000000000 +0200
+@@ -0,0 +1,249 @@
++/* SIP extension for UDP NAT alteration.
++ *
++ * (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar>
++ * based on RR's ip_nat_ftp.c and other modules.
++ *
++ * This program is free software; you can redistribute it and/or modify
++ * it under the terms of the GNU General Public License version 2 as
++ * published by the Free Software Foundation.
++ */
++
++#include <linux/module.h>
++#include <linux/netfilter_ipv4.h>
++#include <linux/ip.h>
++#include <linux/udp.h>
++#include <net/udp.h>
++
++#include <linux/netfilter_ipv4/ip_nat.h>
++#include <linux/netfilter_ipv4/ip_nat_helper.h>
++#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
++#include <linux/netfilter_ipv4/ip_conntrack_sip.h>
++
++MODULE_LICENSE("GPL");
++MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
++MODULE_DESCRIPTION("SIP NAT helper");
++
++#if 0
++#define DEBUGP printk
++#else
++#define DEBUGP(format, args...)
++#endif
++
++extern struct sip_header_nfo ct_sip_hdrs[];
++
++static unsigned int mangle_sip_packet(struct sk_buff **pskb, 
++			enum ip_conntrack_info ctinfo,
++			struct ip_conntrack *ct, 
++			const char **dptr, size_t dlen,
++			char *buffer, int bufflen,
++			struct sip_header_nfo *hnfo)
++{
++	unsigned int matchlen, matchoff;
++	
++	if (ct_sip_get_info(*dptr, dlen, &matchoff, &matchlen, hnfo) <= 0)
++		return 0;
++
++	if (!ip_nat_mangle_udp_packet(pskb, ct, ctinfo, 
++	    matchoff, matchlen, buffer, bufflen)) {
++		return 0;
++	}
++	/* We need to reload this. Thanks Patrick. */
++	*dptr = (*pskb)->data + (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr); 
++	return 1;
++}
++
++static unsigned int ip_nat_sip(struct sk_buff **pskb, 
++			enum ip_conntrack_info ctinfo,
++			struct ip_conntrack *ct,
++			const char **dptr)
++{
++	char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];	
++	unsigned int bufflen, dataoff;
++	uint32_t ip;
++	uint16_t port;
++	
++	dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
++	
++	if ((ctinfo) >= IP_CT_IS_REPLY) {
++		ip = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip;
++		port = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
++	} else {
++		ip = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip;
++		port = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.udp.port;
++	}
++	bufflen = sprintf(buffer, "%u.%u.%u.%u:%u", NIPQUAD(ip), ntohs(port));
++	
++	/* short packet ? */
++	if (((*pskb)->len - dataoff) < (sizeof("SIP/2.0") - 1))
++		return 0;
++	
++	/* Basic rules: requests and responses. */
++	if (memcmp(*dptr, "SIP/2.0", sizeof("SIP/2.0") - 1) == 0) {
++	
++		if ((ctinfo) < IP_CT_IS_REPLY) {
++			mangle_sip_packet(pskb, ctinfo, ct, dptr, 
++				(*pskb)->len - dataoff, buffer, bufflen,
++				&ct_sip_hdrs[POS_CONTACT]);
++			return 1;
++		}
++
++		if (!mangle_sip_packet(pskb, ctinfo, ct, dptr, (*pskb)->len - dataoff,
++		    buffer, bufflen, &ct_sip_hdrs[POS_VIA])) {
++			return 0;
++		}
++		
++		/* This search should ignore case, but later.. */
++		const char *aux = ct_sip_search("CSeq:", *dptr, sizeof("CSeq:") - 1, 
++								(*pskb)->len - dataoff);
++		if (!aux)
++			return 0;
++		
++		if (!ct_sip_search("REGISTER", aux, sizeof("REGISTER"), 
++		    ct_sip_lnlen(aux, *dptr + (*pskb)->len - dataoff))) {
++			return 1;
++		}
++		return mangle_sip_packet(pskb, ctinfo, ct, dptr, (*pskb)->len - dataoff, 
++						buffer, bufflen, &ct_sip_hdrs[POS_CONTACT]);
++	}
++	if ((ctinfo) < IP_CT_IS_REPLY) {
++		if (!mangle_sip_packet(pskb, ctinfo, ct, dptr, (*pskb)->len - dataoff,
++		    buffer, bufflen, &ct_sip_hdrs[POS_VIA])) {
++			return 0;
++		}
++		
++		/* Mangle Contact if exists only. - watch udp_nat_mangle()! */
++		mangle_sip_packet(pskb, ctinfo, ct, dptr, (*pskb)->len - dataoff, 
++						buffer, bufflen, &ct_sip_hdrs[POS_CONTACT]);
++		return 1;
++	}
++	/* This mangle requests headers. */
++	return mangle_sip_packet(pskb, ctinfo, ct, dptr, 
++			ct_sip_lnlen(*dptr, *dptr + (*pskb)->len - dataoff),
++			buffer, bufflen, &ct_sip_hdrs[POS_REQ_HEADER]);
++}
++
++static int mangle_content_len(struct sk_buff **pskb, 
++			enum ip_conntrack_info ctinfo,
++			struct ip_conntrack *ct,
++			const char *dptr)
++{
++	unsigned int dataoff, matchoff, matchlen;
++	char buffer[sizeof("65536")];
++	int bufflen;
++	
++	dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
++	
++	/* Get actual SDP lenght */
++	if (ct_sip_get_info(dptr, (*pskb)->len - dataoff, &matchoff, 
++	    &matchlen, &ct_sip_hdrs[POS_SDP_HEADER]) > 0) {
++		
++		/* since ct_sip_get_info() give us a pointer passing 'v='
++		   we need to add 2 bytes in this count. */
++		int c_len = (*pskb)->len - dataoff - matchoff + 2;
++		
++		/* Now, update SDP lenght */
++		if (ct_sip_get_info(dptr, (*pskb)->len - dataoff, &matchoff, 
++		    &matchlen, &ct_sip_hdrs[POS_CONTENT]) > 0) {
++		    
++			bufflen = sprintf(buffer, "%u", c_len);
++			
++			return ip_nat_mangle_udp_packet(pskb, ct, ctinfo, matchoff,
++							matchlen, buffer, bufflen);
++		}
++	}
++	return 0;
++}
++
++static unsigned int mangle_sdp(struct sk_buff **pskb, 
++			enum ip_conntrack_info ctinfo,
++			struct ip_conntrack *ct,
++			uint32_t newip, uint16_t port,
++			const char *dptr)
++{
++	char buffer[sizeof("nnn.nnn.nnn.nnn")];
++	unsigned int dataoff, bufflen;
++
++	dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
++	
++	/* Mangle owner and contact info. */
++	bufflen = sprintf(buffer, "%u.%u.%u.%u", NIPQUAD(newip));
++	if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff,
++	    buffer, bufflen, &ct_sip_hdrs[POS_OWNER])) {
++		return 0;	
++	}
++	
++	if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff,
++	    buffer, bufflen, &ct_sip_hdrs[POS_CONECTION])) {
++		return 0;
++	}
++	
++	/* Mangle media port. */
++	bufflen = sprintf(buffer, "%u", port);
++	if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff,
++	    buffer, bufflen, &ct_sip_hdrs[POS_MEDIA])) {
++		return 0;
++	}
++	
++	return mangle_content_len(pskb, ctinfo, ct, dptr);
++}
++
++/* So, this packet has hit the connection tracking matching code.
++   Mangle it, and change the expectation to match the new version. */
++static unsigned int ip_nat_sdp(struct sk_buff **pskb, 
++			enum ip_conntrack_info ctinfo,
++			struct ip_conntrack_expect *exp,
++			const char *dptr)
++{
++	struct ip_conntrack *ct = exp->master;
++	uint32_t newip;
++	uint16_t port;
++	
++	DEBUGP("ip_nat_sdp():\n");
++
++	/* Connection will come from reply */
++	newip = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip;
++	
++	exp->tuple.dst.ip = newip;
++	exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port;
++	exp->dir = IP_CT_DIR_REPLY;
++
++	/* When you see the packet, we need to NAT it the same as the
++	   this one. */
++	exp->expectfn = ip_nat_follow_master;
++
++	/* Try to get same port: if not, try to change it. */
++	for (port = ntohs(exp->saved_proto.udp.port); port != 0; port++) {
++		exp->tuple.dst.u.udp.port = htons(port);
++		if (ip_conntrack_expect_related(exp) == 0)
++			break;
++	}
++	
++	if (port == 0)
++		return NF_DROP;
++	
++	if (!mangle_sdp(pskb, ctinfo, ct, newip, port, dptr)) {
++		ip_conntrack_unexpect_related(exp);
++		return NF_DROP;
++	}
++	return NF_ACCEPT;
++}
++
++static void __exit fini(void)
++{
++	ip_nat_sip_hook = NULL;
++	ip_nat_sdp_hook = NULL;
++	/* Make sure noone calls it, meanwhile. */
++	synchronize_net();
++}
++
++static int __init init(void)
++{
++	BUG_ON(ip_nat_sip_hook);
++	BUG_ON(ip_nat_sdp_hook);
++	ip_nat_sip_hook = ip_nat_sip;
++	ip_nat_sdp_hook = ip_nat_sdp;
++	return 0;
++}
++
++module_init(init);
++module_exit(fini);
+diff -urN linux-2.6.16.4/net/ipv4/netfilter/Kconfig linux-2.6.16.4.new/net/ipv4/netfilter/Kconfig
+--- linux-2.6.16.4/net/ipv4/netfilter/Kconfig	2006-04-12 17:29:19.000000000 +0200
++++ linux-2.6.16.4.new/net/ipv4/netfilter/Kconfig	2006-04-12 17:32:53.000000000 +0200
+@@ -168,6 +168,19 @@
+ 	  If you want to compile it as a module, say M here and read
+ 	  Documentation/modules.txt.  If unsure, say `N'.
+ 
++config IP_NF_SIP
++	tristate  'SIP support'
++	depends on IP_NF_CONNTRACK
++	help
++	  SIP is an application-layer control protocol that can establish,
++   	  modify, and terminate multimedia sessions (conferences) such as
++   	  Internet telephony calls. With the ip_conntrack_sip and
++	  the ip_nat_sip modules you can support the protocol on a connection
++	  tracking/NATing firewall.
++	
++	  If you want to compile it as a module, say 'M' here and read
++	  Documentation/modules.txt.  If unsure, say 'N'.
++
+ config IP_NF_QUEUE
+ 	tristate "IP Userspace queueing via NETLINK (OBSOLETE)"
+ 	help
+@@ -545,6 +558,12 @@
+ 	default IP_NF_NAT if IP_NF_PPTP=y
+ 	default m if IP_NF_PPTP=m
+ 
++config IP_NF_NAT_SIP
++	tristate
++	depends on IP_NF_CONNTRACK!=n && IP_NF_NAT!=n
++	default IP_NF_NAT if IP_NF_SIP=y
++	default m if IP_NF_SIP=m
++
+ # mangle + specific targets
+ config IP_NF_MANGLE
+ 	tristate "Packet mangling"
+diff -urN linux-2.6.16.4/net/ipv4/netfilter/Makefile linux-2.6.16.4.new/net/ipv4/netfilter/Makefile
+--- linux-2.6.16.4/net/ipv4/netfilter/Makefile	2006-04-12 17:29:19.000000000 +0200
++++ linux-2.6.16.4.new/net/ipv4/netfilter/Makefile	2006-04-12 17:33:39.000000000 +0200
+@@ -28,6 +28,7 @@
+ obj-$(CONFIG_IP_NF_FTP) += ip_conntrack_ftp.o
+ obj-$(CONFIG_IP_NF_IRC) += ip_conntrack_irc.o
+ obj-$(CONFIG_IP_NF_NETBIOS_NS) += ip_conntrack_netbios_ns.o
++obj-$(CONFIG_IP_NF_SIP) += ip_conntrack_sip.o
+ 
+ # NAT helpers 
+ obj-$(CONFIG_IP_NF_NAT_PPTP) += ip_nat_pptp.o
+@@ -35,6 +36,7 @@
+ obj-$(CONFIG_IP_NF_NAT_TFTP) += ip_nat_tftp.o
+ obj-$(CONFIG_IP_NF_NAT_FTP) += ip_nat_ftp.o
+ obj-$(CONFIG_IP_NF_NAT_IRC) += ip_nat_irc.o
++obj-$(CONFIG_IP_NF_NAT_SIP) += ip_nat_sip.o
+ 
+ # generic IP tables 
+ obj-$(CONFIG_IP_NF_IPTABLES) += ip_tables.o
+diff -urN linux-2.6.16.4/include/linux/netfilter_ipv4/ip_conntrack.h linux-2.6.16.4.new/include/linux/netfilter_ipv4/ip_conntrack.h
+--- linux-2.6.16.4/include/linux/netfilter_ipv4/ip_conntrack.h	2006-04-12 17:29:19.000000000 +0200
++++ linux-2.6.16.4.new/include/linux/netfilter_ipv4/ip_conntrack.h	2006-04-12 17:30:38.000000000 +0200
+@@ -33,6 +33,7 @@
+ #include <linux/netfilter_ipv4/ip_conntrack_amanda.h>
+ #include <linux/netfilter_ipv4/ip_conntrack_ftp.h>
+ #include <linux/netfilter_ipv4/ip_conntrack_irc.h>
++#include <linux/netfilter_ipv4/ip_conntrack_sip.h>
+ 
+ /* per conntrack: application helper private data */
+ union ip_conntrack_help {
+@@ -40,6 +41,7 @@
+ 	struct ip_ct_pptp_master ct_pptp_info;
+ 	struct ip_ct_ftp_master ct_ftp_info;
+ 	struct ip_ct_irc_master ct_irc_info;
++	struct ip_ct_sip_master ct_sip_info;
+ };
+ 
+ #ifdef CONFIG_IP_NF_NAT_NEEDED
+diff -urN linux-2.6.16.4/include/linux/netfilter_ipv4/ip_conntrack_sip.h linux-2.6.16.4.new/include/linux/netfilter_ipv4/ip_conntrack_sip.h
+--- linux-2.6.16.4/include/linux/netfilter_ipv4/ip_conntrack_sip.h	1970-01-01 01:00:00.000000000 +0100
++++ linux-2.6.16.4.new/include/linux/netfilter_ipv4/ip_conntrack_sip.h	2006-04-12 17:31:12.000000000 +0200
+@@ -0,0 +1,81 @@
++#ifndef __IP_CONNTRACK_SIP_H__
++#define __IP_CONNTRACK_SIP_H__
++/* SIP tracking. */
++
++#ifdef __KERNEL__
++
++#define SIP_PORT	5060
++#define SIP_TIMEOUT	3600
++
++#define POS_VIA		0
++#define POS_CONTACT	1
++#define POS_CONTENT	2
++#define POS_MEDIA	3
++#define POS_OWNER	4
++#define POS_CONECTION	5
++#define POS_REQ_HEADER	6
++#define POS_SDP_HEADER	7
++
++struct ip_ct_sip_master {
++};
++
++struct sip_header_nfo {
++	const char *lname;
++	size_t lnlen;
++	const char *sname;
++	size_t snlen;
++	const char *ln_str;
++	size_t ln_strlen;
++	int (*match_len)(const char *, const char *, int *);
++
++};
++
++extern unsigned int (*ip_nat_sip_hook)(struct sk_buff **pskb, 
++				enum ip_conntrack_info ctinfo,
++				struct ip_conntrack *ct,
++				const char **dptr);
++				
++/* For NAT to hook in when on expect. */
++extern unsigned int (*ip_nat_sdp_hook)(struct sk_buff **pskb, 
++				enum ip_conntrack_info ctinfo,
++				struct ip_conntrack_expect *exp,
++				const char *dptr);
++
++extern int ct_sip_get_info(const char *dptr, size_t dlen, 
++				unsigned int *matchoff, 
++				unsigned int *matchlen, 
++				struct sip_header_nfo *hnfo);
++
++/* get line lenght until first CR or LF seen. */
++static __inline__ int ct_sip_lnlen(const char *line, const char *limit)
++{
++        const char *k = line;
++
++        while ((line <= limit) && (*line == '\r' || *line == '\n'))
++                line++;
++
++        while (line <= limit) {
++                if (*line == '\r' || *line == '\n')
++                        break;
++                line++;
++        }
++        return line - k;
++}
++
++/* Linear string search, case sensitive. */
++static __inline__ 
++const char *ct_sip_search(const char *needle, const char *haystack, 
++			size_t needle_len, size_t haystack_len) 
++{
++	const char *limit = haystack + (haystack_len - needle_len);
++
++	while (haystack <= limit) {
++		if (memcmp(haystack, needle, needle_len) == 0)
++			return haystack;
++		haystack++;
++	}
++	return NULL;
++}
++#endif /* __KERNEL__ */
++
++#endif /* __IP_CONNTRACK_SIP_H__ */