--- /dev/null
+++ b/extensions/rtsp/Kbuild
@@ -0,0 +1,4 @@
+# -*- Makefile -*-
+
+obj-m += nf_nat_rtsp.o
+obj-m += nf_conntrack_rtsp.o
--- /dev/null
+++ b/extensions/rtsp/netfilter_helpers.h
@@ -0,0 +1,144 @@
+/*
+ * Helpers for netfiler modules.  This file provides implementations for basic
+ * functions such as strncasecmp(), etc.
+ *
+ * gcc will warn for defined but unused functions, so we only include the
+ * functions requested.  The following macros are used:
+ *   NF_NEED_STRNCASECMP        nf_strncasecmp()
+ *   NF_NEED_STRTOU16           nf_strtou16()
+ *   NF_NEED_STRTOU32           nf_strtou32()
+ */
+#ifndef _NETFILTER_HELPERS_H
+#define _NETFILTER_HELPERS_H
+
+/* Only include these functions for kernel code. */
+#ifdef __KERNEL__
+
+#include <net/netfilter/nf_conntrack_expect.h>
+
+#include <linux/ctype.h>
+#define iseol(c) ( (c) == '\r' || (c) == '\n' )
+
+/*
+ * The standard strncasecmp()
+ */
+#ifdef NF_NEED_STRNCASECMP
+static int
+nf_strncasecmp(const char* s1, const char* s2, u_int32_t len)
+{
+    if (s1 == NULL || s2 == NULL)
+    {
+        if (s1 == NULL && s2 == NULL)
+        {
+            return 0;
+        }
+        return (s1 == NULL) ? -1 : 1;
+    }
+    while (len > 0 && tolower(*s1) == tolower(*s2))
+    {
+        len--;
+        s1++;
+        s2++;
+    }
+    return ( (len == 0) ? 0 : (tolower(*s1) - tolower(*s2)) );
+}
+#endif /* NF_NEED_STRNCASECMP */
+
+/*
+ * Parse a string containing a 16-bit unsigned integer.
+ * Returns the number of chars used, or zero if no number is found.
+ */
+#ifdef NF_NEED_STRTOU16
+static int
+nf_strtou16(const char* pbuf, u_int16_t* pval)
+{
+    int n = 0;
+
+    *pval = 0;
+    while (isdigit(pbuf[n]))
+    {
+        *pval = (*pval * 10) + (pbuf[n] - '0');
+        n++;
+    }
+
+    return n;
+}
+#endif /* NF_NEED_STRTOU16 */
+
+/*
+ * Parse a string containing a 32-bit unsigned integer.
+ * Returns the number of chars used, or zero if no number is found.
+ */
+#ifdef NF_NEED_STRTOU32
+static int
+nf_strtou32(const char* pbuf, u_int32_t* pval)
+{
+    int n = 0;
+
+    *pval = 0;
+    while (pbuf[n] >= '0' && pbuf[n] <= '9')
+    {
+        *pval = (*pval * 10) + (pbuf[n] - '0');
+        n++;
+    }
+
+    return n;
+}
+#endif /* NF_NEED_STRTOU32 */
+
+/*
+ * Given a buffer and length, advance to the next line and mark the current
+ * line.
+ */
+#ifdef NF_NEED_NEXTLINE
+static int
+nf_nextline(char* p, uint len, uint* poff, uint* plineoff, uint* plinelen)
+{
+    uint    off = *poff;
+    uint    physlen = 0;
+
+    if (off >= len)
+    {
+        return 0;
+    }
+
+    while (p[off] != '\n')
+    {
+        if (len-off <= 1)
+        {
+            return 0;
+        }
+
+        physlen++;
+        off++;
+    }
+
+    /* if we saw a crlf, physlen needs adjusted */
+    if (physlen > 0 && p[off] == '\n' && p[off-1] == '\r')
+    {
+        physlen--;
+    }
+
+    /* advance past the newline */
+    off++;
+
+    *plineoff = *poff;
+    *plinelen = physlen;
+    *poff = off;
+
+    return 1;
+}
+#endif /* NF_NEED_NEXTLINE */
+
+static inline int rtsp_nf_ct_expect_related(struct nf_conntrack_expect *expect)
+{
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5,3,0)
+	return nf_ct_expect_related(expect, 0);
+#else
+	return nf_ct_expect_related(expect);
+#endif
+}
+
+#endif /* __KERNEL__ */
+
+#endif /* _NETFILTER_HELPERS_H */
--- /dev/null
+++ b/extensions/rtsp/netfilter_mime.h
@@ -0,0 +1,89 @@
+/*
+ * MIME functions for netfilter modules.  This file provides implementations
+ * for basic MIME parsing.  MIME headers are used in many protocols, such as
+ * HTTP, RTSP, SIP, etc.
+ *
+ * gcc will warn for defined but unused functions, so we only include the
+ * functions requested.  The following macros are used:
+ *   NF_NEED_MIME_NEXTLINE      nf_mime_nextline()
+ */
+#ifndef _NETFILTER_MIME_H
+#define _NETFILTER_MIME_H
+
+/* Only include these functions for kernel code. */
+#ifdef __KERNEL__
+
+#include <linux/ctype.h>
+
+/*
+ * Given a buffer and length, advance to the next line and mark the current
+ * line.  If the current line is empty, *plinelen will be set to zero.  If
+ * not, it will be set to the actual line length (including CRLF).
+ *
+ * 'line' in this context means logical line (includes LWS continuations).
+ * Returns 1 on success, 0 on failure.
+ */
+#ifdef NF_NEED_MIME_NEXTLINE
+static int
+nf_mime_nextline(char* p, uint len, uint* poff, uint* plineoff, uint* plinelen)
+{
+    uint    off = *poff;
+    uint    physlen = 0;
+    int     is_first_line = 1;
+
+    if (off >= len)
+    {
+        return 0;
+    }
+
+    do
+    {
+        while (p[off] != '\n')
+        {
+            if (len-off <= 1)
+            {
+                return 0;
+            }
+
+            physlen++;
+            off++;
+        }
+
+        /* if we saw a crlf, physlen needs adjusted */
+        if (physlen > 0 && p[off] == '\n' && p[off-1] == '\r')
+        {
+            physlen--;
+        }
+
+        /* advance past the newline */
+        off++;
+
+        /* check for an empty line */
+        if (physlen == 0)
+        {
+            break;
+        }
+
+        /* check for colon on the first physical line */
+        if (is_first_line)
+        {
+            is_first_line = 0;
+            if (memchr(p+(*poff), ':', physlen) == NULL)
+            {
+                return 0;
+            }
+        }
+    }
+    while (p[off] == ' ' || p[off] == '\t');
+
+    *plineoff = *poff;
+    *plinelen = (physlen == 0) ? 0 : (off - *poff);
+    *poff = off;
+
+    return 1;
+}
+#endif /* NF_NEED_MIME_NEXTLINE */
+
+#endif /* __KERNEL__ */
+
+#endif /* _NETFILTER_MIME_H */
--- /dev/null
+++ b/extensions/rtsp/nf_conntrack_rtsp.c
@@ -0,0 +1,756 @@
+/*
+ * RTSP extension for IP connection tracking
+ * (C) 2003 by Tom Marshall <tmarshall at real.com>
+ *
+ * 2005-02-13: Harald Welte <laforge at netfilter.org>
+ * 	- port to 2.6
+ * 	- update to recent post-2.6.11 api changes
+ * 2006-09-14: Steven Van Acker <deepstar at singularity.be>
+ *	- removed calls to NAT code from conntrack helper: NAT no longer needed to use rtsp-conntrack
+ * 2007-04-18: Michael Guntsche <mike at it-loops.com>
+ * 			- Port to new NF API
+ * 2013-03-04: Il'inykh Sergey <sergeyi at inango-sw.com>. Inango Systems Ltd
+ *	- fixed rtcp nat mapping and other port mapping fixes
+ *	- simple TEARDOWN request handling
+ *	- codestyle fixes and other less significant bug fixes
+ * 2018-04-17: Alin Nastac <alin.nastac at gmail.com>
+ *             Hans Dedecker <dedeckeh at gmail.com>
+ *       - use IP address read from SETUP URI in expected connections
+ * 2018-04-18: Hans Dedecker <dedeckeh at gmail.com>
+ *       - update RTP expected connection source IP based on SOURCE
+ *         in the SETUP reply message
+ * 2018-08-03: Alin Nastac <alin.nastac at gmail.com>
+ *             Hans Dedecker <dedeckeh at gmail.com>
+ *       - parse non-standard destination=address:port format
+ *
+ * based on ip_conntrack_irc.c
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ *
+ * Module load syntax:
+ *   insmod nf_conntrack_rtsp.o ports=port1,port2,...port<MAX_PORTS>
+ *                              max_outstanding=n setup_timeout=secs
+ *
+ * If no ports are specified, the default will be port 554.
+ *
+ * With max_outstanding you can define the maximum number of not yet
+ * answered SETUP requests per RTSP session (default 8).
+ * With setup_timeout you can specify how long the system waits for
+ * an expected data channel (default 300 seconds).
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/netfilter.h>
+#include <linux/ip.h>
+#include <linux/inet.h>
+#include <net/tcp.h>
+
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_conntrack_zones.h>
+#include "nf_conntrack_rtsp.h"
+
+#define NF_NEED_STRNCASECMP
+#define NF_NEED_STRTOU16
+#define NF_NEED_STRTOU32
+#define NF_NEED_NEXTLINE
+#include "netfilter_helpers.h"
+#define NF_NEED_MIME_NEXTLINE
+#include "netfilter_mime.h"
+
+#include <linux/ctype.h>
+
+#define MAX_PORTS 8
+static int ports[MAX_PORTS];
+static int num_ports = 0;
+static int max_outstanding = 8;
+static unsigned int setup_timeout = 300;
+
+MODULE_AUTHOR("Tom Marshall <tmarshall at real.com>");
+MODULE_DESCRIPTION("RTSP connection tracking module");
+MODULE_LICENSE("GPL");
+module_param_array(ports, int, &num_ports, 0400);
+MODULE_PARM_DESC(ports, "port numbers of RTSP servers");
+module_param(max_outstanding, int, 0400);
+MODULE_PARM_DESC(max_outstanding, "max number of outstanding SETUP requests per RTSP session");
+module_param(setup_timeout, uint, 0400);
+MODULE_PARM_DESC(setup_timeout, "timeout on for unestablished data channels");
+
+static char *rtsp_buffer;
+static DEFINE_SPINLOCK(rtsp_buffer_lock);
+
+static struct nf_conntrack_expect_policy rtsp_exp_policy;
+
+unsigned int (*nf_nat_rtsp_hook)(struct sk_buff *skb,
+				 enum ip_conntrack_info ctinfo,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+				 unsigned int protoff,
+#endif
+				 unsigned int matchoff, unsigned int matchlen,
+				 struct ip_ct_rtsp_expect* prtspexp,
+				 struct nf_conntrack_expect *rtp_exp,
+				 struct nf_conntrack_expect *rtcp_exp);
+
+EXPORT_SYMBOL_GPL(nf_nat_rtsp_hook);
+
+/*
+ * Max mappings we will allow for one RTSP connection (for RTP, the number
+ * of allocated ports is twice this value).  Note that SMIL burns a lot of
+ * ports so keep this reasonably high.  If this is too low, you will see a
+ * lot of "no free client map entries" messages.
+ */
+#define MAX_PORT_MAPS 16
+
+/*** default port list was here in the masq code: 554, 3030, 4040 ***/
+
+#define SKIP_WSPACE(ptr,len,off) while(off < len && isspace(*(ptr+off))) { off++; }
+
+/*
+ * Parse an RTSP packet.
+ *
+ * Returns zero if parsing failed.
+ *
+ * Parameters:
+ *  IN      ptcp        tcp data pointer
+ *  IN      tcplen      tcp data len
+ *  IN/OUT  ptcpoff     points to current tcp offset
+ *  OUT     phdrsoff    set to offset of rtsp headers
+ *  OUT     phdrslen    set to length of rtsp headers
+ *  OUT     pcseqoff    set to offset of CSeq header
+ *  OUT     pcseqlen    set to length of CSeq header
+ */
+static int
+rtsp_parse_message(char* ptcp, uint tcplen, uint* ptcpoff,
+		   uint* phdrsoff, uint* phdrslen,
+		   uint* pcseqoff, uint* pcseqlen,
+		   uint* transoff, uint* translen)
+{
+	uint	entitylen = 0;
+	uint	lineoff;
+	uint	linelen;
+	
+	if (!nf_nextline(ptcp, tcplen, ptcpoff, &lineoff, &linelen))
+		return 0;
+	
+	*phdrsoff = *ptcpoff;
+	while (nf_mime_nextline(ptcp, tcplen, ptcpoff, &lineoff, &linelen)) {
+		if (linelen == 0) {
+			if (entitylen > 0)
+				*ptcpoff += min(entitylen, tcplen - *ptcpoff);
+			break;
+		}
+		if (lineoff+linelen > tcplen) {
+			pr_info("!! overrun !!\n");
+			break;
+		}
+
+		if (nf_strncasecmp(ptcp+lineoff, "CSeq:", 5) == 0) {
+			*pcseqoff = lineoff;
+			*pcseqlen = linelen;
+		} 
+
+		if (nf_strncasecmp(ptcp+lineoff, "Transport:", 10) == 0) {
+			*transoff = lineoff;
+			*translen = linelen;
+		}
+		
+		if (nf_strncasecmp(ptcp+lineoff, "Content-Length:", 15) == 0) {
+			uint off = lineoff+15;
+			SKIP_WSPACE(ptcp+lineoff, linelen, off);
+			nf_strtou32(ptcp+off, &entitylen);
+		}
+	}
+	*phdrslen = (*ptcpoff) - (*phdrsoff);
+	
+	return 1;
+}
+
+/*
+ * Find lo/hi client ports and/or source (if any) in transport header
+ * In:
+ *   ptcp, tcplen = packet
+ *   tranoff, tranlen = buffer to search
+ *
+ * Out:
+ *   pport_lo, pport_hi = lo/hi ports (host endian)
+ *   srvaddr
+ *
+ * Returns nonzero if any client ports found
+ *
+ * Note: it is valid (and expected) for the client to request multiple
+ * transports, so we need to parse the entire line.
+ */
+static int
+rtsp_parse_transport(char* ptran, uint tranlen,
+		     struct ip_ct_rtsp_expect* prtspexp)
+{
+	int  rc = 0;
+	uint off = 0;
+	
+	if (tranlen < 10 || !iseol(ptran[tranlen-1]) ||
+	    nf_strncasecmp(ptran, "Transport:", 10) != 0) {
+		pr_info("sanity check failed\n");
+		return 0;
+	}
+	
+	pr_debug("tran='%.*s'\n", (int)tranlen, ptran);
+	off += 10;
+	SKIP_WSPACE(ptran, tranlen, off);
+	
+	/* Transport: tran;field;field=val,tran;field;field=val,... */
+	while (off < tranlen) {
+		const char* pparamend;
+		uint        nextparamoff;
+		
+		pparamend = memchr(ptran+off, ',', tranlen-off);
+		pparamend = (pparamend == NULL) ? ptran+tranlen : pparamend+1;
+		nextparamoff = pparamend-ptran;
+		
+		while (off < nextparamoff) {
+			const char* pfieldend;
+			uint        nextfieldoff;
+			
+			pfieldend = memchr(ptran+off, ';', nextparamoff-off);
+			nextfieldoff = (pfieldend == NULL) ? nextparamoff : pfieldend-ptran+1;
+		   
+			if (strncmp(ptran+off, "client_port=", 12) == 0) {
+				u_int16_t   port;
+				uint        numlen;
+
+				off += 12;
+				numlen = nf_strtou16(ptran+off, &port);
+				off += numlen;
+				if (prtspexp->loport != 0 && prtspexp->loport != port)
+					pr_debug("multiple ports found, port %hu ignored\n", port);
+				else {
+					pr_debug("lo port found : %hu\n", port);
+					prtspexp->loport = prtspexp->hiport = port;
+					if (ptran[off] == '-') {
+						off++;
+						numlen = nf_strtou16(ptran+off, &port);
+						off += numlen;
+						prtspexp->pbtype = pb_range;
+						prtspexp->hiport = port;
+						
+						// If we have a range, assume rtp:
+						// loport must be even, hiport must be loport+1
+						if ((prtspexp->loport & 0x0001) != 0 ||
+						    prtspexp->hiport != prtspexp->loport+1) {
+							pr_debug("incorrect range: %hu-%hu, correcting\n",
+							       prtspexp->loport, prtspexp->hiport);
+							prtspexp->loport &= 0xfffe;
+							prtspexp->hiport = prtspexp->loport+1;
+						}
+					} else if (ptran[off] == '/') {
+						off++;
+						numlen = nf_strtou16(ptran+off, &port);
+						off += numlen;
+						prtspexp->pbtype = pb_discon;
+						prtspexp->hiport = port;
+					}
+					rc = 1;
+				}
+			} else if (strncmp(ptran+off, "source=", 7) == 0) {
+				uint srcaddrlen;
+
+				off += 7;
+				srcaddrlen = nextfieldoff - off - 1;
+
+				if (in4_pton(ptran + off, srcaddrlen,
+					     (u8 *)&prtspexp->srvaddr.in,
+					     -1, NULL))
+					pr_debug("source found : %pI4\n",
+						 &prtspexp->srvaddr.ip);
+			} else if (nextfieldoff - off > 12 && strncmp(ptran+off, "destination=", 12) == 0) {
+				const char *psep;
+				u_int16_t   port;
+
+				off += 12;
+
+				if (in4_pton(ptran+off, nextfieldoff - off - 1, (u8 *)&prtspexp->cltaddr.in, -1, NULL)) {
+					pr_debug("destination found : %pI4\n", &prtspexp->cltaddr.ip);
+
+					/*
+					 * Some RTSP clients(mostly STBs) use non-standard destination parameters:
+					 * destination=address:port
+					 */
+					psep = memchr(ptran+off, ':', nextfieldoff-off);
+					if (psep != NULL && nf_strtou16(psep + 1, &port)) {
+						if (prtspexp->loport != 0 && prtspexp->loport != port)
+							pr_debug("multiple ports found, port %hu ignored\n", port);
+						else {
+							pr_debug("lo port found : %hu\n", port);
+							prtspexp->loport = prtspexp->hiport = port;
+						}
+					}
+				}
+			}
+			
+			/*
+			 * Note we don't look for the destination parameter here.
+			 * If we are using NAT, the NAT module will handle it.  If not,
+			 * and the client is sending packets elsewhere, the expectation
+			 * will quietly time out.
+			 */
+			
+			off = nextfieldoff;
+		}
+		
+		off = nextparamoff;
+	}
+	
+	return rc;
+}
+
+
+/*** conntrack functions ***/
+
+/* outbound packet: client->server */
+
+static inline int
+help_out(struct sk_buff *skb, unsigned char *rb_ptr, unsigned int datalen,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+	 struct nf_conn *ct, enum ip_conntrack_info ctinfo,
+	 unsigned int protoff)
+#else
+	 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
+#endif
+{
+	struct ip_ct_rtsp_expect expinfo;
+	
+	int dir = CTINFO2DIR(ctinfo);   /* = IP_CT_DIR_ORIGINAL */
+	//struct  tcphdr* tcph = (void*)iph + iph->ihl * 4;
+	//uint    tcplen = pktlen - iph->ihl * 4;
+	char*   pdata = rb_ptr;
+	//uint    datalen = tcplen - tcph->doff * 4;
+	uint    dataoff = 0;
+	int ret = NF_ACCEPT;
+	
+	struct nf_conntrack_expect *rtp_exp;
+	struct nf_conntrack_expect *rtcp_exp = NULL;
+	
+	__be16 be_loport;
+	__be16 be_hiport;
+	
+	typeof(nf_nat_rtsp_hook) nf_nat_rtsp;
+
+	memset(&expinfo, 0, sizeof(expinfo));
+	
+	while (dataoff < datalen) {
+		uint cmdoff = dataoff;
+		uint hdrsoff = 0;
+		uint hdrslen = 0;
+		uint cseqoff = 0;
+		uint cseqlen = 0;
+		uint transoff = 0;
+		uint translen = 0;
+		uint off;
+		union nf_inet_addr srvaddr;
+		
+		if (!rtsp_parse_message(pdata, datalen, &dataoff,
+					&hdrsoff, &hdrslen,
+					&cseqoff, &cseqlen,
+					&transoff, &translen))
+			break;      /* not a valid message */
+
+		if (strncmp(pdata+cmdoff, "TEARDOWN ", 9) == 0) {
+			pr_debug("teardown handled\n");
+			nf_ct_remove_expectations(ct); /* FIXME must be session id aware */
+			break;
+		}
+
+		if (strncmp(pdata+cmdoff, "SETUP ", 6) != 0)
+			continue;   /* not a SETUP message */
+
+		srvaddr = ct->tuplehash[!dir].tuple.src.u3;
+
+		/* try to get RTP media source from SETUP URI */
+		off = cmdoff + 6;
+		while (off < datalen) {
+			if (strncmp(pdata+off, "://", 3) == 0) {
+				off += 3;
+				cmdoff = off;
+
+				while (off < datalen) {
+					if (pdata[off] == ':' ||
+					    pdata[off] == '/' ||
+					    pdata[off] == ' ') {
+						in4_pton(pdata + cmdoff,
+							 off - cmdoff,
+							 (u8 *)&srvaddr.in,
+							 -1, NULL);
+						break;
+					}
+					off++;
+				}
+				break;
+			}
+			off++;
+		}
+
+		pr_debug("found a setup message\n");
+
+		off = 0;
+		if(translen)
+			rtsp_parse_transport(pdata+transoff, translen, &expinfo);
+
+		if (expinfo.loport == 0) {
+			pr_debug("no udp transports found\n");
+			continue;   /* no udp transports found */
+		}
+
+		pr_debug("udp transport found, ports=(%d,%hu,%hu)\n",
+			 (int)expinfo.pbtype, expinfo.loport, expinfo.hiport);
+
+
+		be_loport = htons(expinfo.loport);
+
+		rtp_exp = nf_ct_expect_alloc(ct);
+		if (rtp_exp == NULL) {
+			ret = NF_DROP;
+			goto out;
+		}
+
+		nf_ct_expect_init(rtp_exp, NF_CT_EXPECT_CLASS_DEFAULT,
+				  nf_ct_l3num(ct), NULL,
+				  &ct->tuplehash[!dir].tuple.dst.u3,
+				  IPPROTO_UDP, NULL, &be_loport);
+
+		rtp_exp->flags = 0;
+
+		if (expinfo.pbtype == pb_range || expinfo.pbtype == pb_discon) {
+			pr_debug("setup expectation for rtcp\n");
+
+			be_hiport = htons(expinfo.hiport);
+			rtcp_exp = nf_ct_expect_alloc(ct);
+			if (rtcp_exp == NULL) {
+				ret = NF_DROP;
+				goto out1;
+			}
+
+			nf_ct_expect_init(rtcp_exp, NF_CT_EXPECT_CLASS_DEFAULT,
+					  nf_ct_l3num(ct), NULL,
+					  &ct->tuplehash[!dir].tuple.dst.u3,
+					  IPPROTO_UDP, NULL, &be_hiport);
+
+			rtcp_exp->flags = 0;
+
+			pr_debug("expect_related %pI4:%u-%u-%pI4:%u-%u\n",
+				   &rtp_exp->tuple.src.u3.ip,
+				   ntohs(rtp_exp->tuple.src.u.udp.port),
+				   ntohs(rtcp_exp->tuple.src.u.udp.port),
+				   &rtp_exp->tuple.dst.u3.ip,
+				   ntohs(rtp_exp->tuple.dst.u.udp.port),
+				   ntohs(rtcp_exp->tuple.dst.u.udp.port));
+		} else {
+			pr_debug("expect_related %pI4:%u-%pI4:%u\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));
+		}
+
+		nf_nat_rtsp = rcu_dereference(nf_nat_rtsp_hook);
+		if (nf_nat_rtsp && ct->status & IPS_NAT_MASK)
+			/* pass the request off to the nat helper */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+			ret = nf_nat_rtsp(skb, ctinfo, protoff, hdrsoff, hdrslen,
+					  &expinfo, rtp_exp, rtcp_exp);
+#else
+			ret = nf_nat_rtsp(skb, ctinfo, hdrsoff, hdrslen,
+					  &expinfo, rtp_exp, rtcp_exp);
+#endif
+		else {
+			if (rtsp_nf_ct_expect_related(rtp_exp) == 0) {
+				if (rtcp_exp && rtsp_nf_ct_expect_related(rtcp_exp) != 0) {
+					nf_ct_unexpect_related(rtp_exp);
+					pr_info("nf_conntrack_expect_related failed for rtcp\n");
+					ret = NF_DROP;
+				}
+			} else {
+				pr_info("nf_conntrack_expect_related failed for rtp\n");
+				ret = NF_DROP;
+			}
+		}
+		if (rtcp_exp) {
+			nf_ct_expect_put(rtcp_exp);
+		}
+out1:
+		nf_ct_expect_put(rtp_exp);
+		goto out;
+	}
+out:
+
+	return ret;
+}
+
+
+static inline int
+help_in(struct sk_buff *skb, unsigned char *rb_ptr, unsigned int datalen,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+	 struct nf_conn *ct, enum ip_conntrack_info ctinfo,
+	 unsigned int protoff)
+#else
+	 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
+#endif
+ {
+	struct ip_ct_rtsp_expect expinfo;
+	union nf_inet_addr srvaddr;
+	int dir = CTINFO2DIR(ctinfo);   /* = IP_CT_DIR_ORIGINAL */
+	int len;
+	char* pdata = rb_ptr;
+	uint dataoff = 0;
+	int ret = NF_ACCEPT;
+	u_int8_t family;
+	struct nf_conntrack_expect *exp_ct = NULL;
+	struct nf_conntrack_tuple t;
+	struct net *net = nf_ct_net(ct);
+
+	memset(&expinfo, 0, sizeof(expinfo));
+
+	while (dataoff < datalen) {
+		uint cmdoff = dataoff;
+		uint hdrsoff = 0;
+		uint hdrslen = 0;
+		uint cseqoff = 0;
+		uint cseqlen = 0;
+		uint transoff = 0;
+		uint translen = 0;
+
+		if (!rtsp_parse_message(pdata, datalen, &dataoff,
+					&hdrsoff, &hdrslen,
+					&cseqoff, &cseqlen,
+					&transoff, &translen))
+			break;      /* not a valid message */
+
+		if (strncmp(pdata+cmdoff, "RTSP/", 5) == 0 && translen) {
+			union nf_inet_addr zeroaddr;
+
+			memset(&zeroaddr, 0, sizeof(zeroaddr));
+
+			if (!rtsp_parse_transport(pdata+transoff, translen, &expinfo))
+				continue;
+
+			srvaddr = expinfo.srvaddr;
+
+			if (nf_inet_addr_cmp(&srvaddr, &ct->tuplehash[dir].tuple.src.u3) ||
+					nf_inet_addr_cmp(&srvaddr, &zeroaddr))
+				continue;
+		} else
+			continue;  /* not valid RTSP reply */
+
+ 		if (expinfo.loport == 0) {
+			pr_debug("no udp transports found\n");
+			continue;   /* no udp transports found */
+		}
+
+		family = nf_ct_l3num(ct);
+		if (family == AF_INET)
+			len = 4;
+		else
+			len = 16;
+
+		/* replace rtp expect src addr */
+		t.src.l3num = family;
+		t.dst.protonum = IPPROTO_UDP;
+
+		memcpy(&t.src.u3, &ct->tuplehash[dir].tuple.src.u3, len);
+		if (sizeof(t.src.u3) > len)
+			/* address needs to be cleared for nf_ct_tuple_equal */
+			memset((void *)&t.src.u3 + len, 0, sizeof(t.src.u3) - len);
+
+		t.src.u.all = 0;
+
+		memcpy(&t.dst.u3, &ct->tuplehash[dir].tuple.dst.u3, len);
+		if (sizeof(t.dst.u3) > len)
+			/* address needs to be cleared for nf_ct_tuple_equal */
+			memset((void *)&t.dst.u3 + len, 0, sizeof(t.dst.u3) - len);
+
+		t.dst.u.all = htons(expinfo.loport);
+
+		/* get the rtp expect and replace the srcaddr with RTP server addr */
+		exp_ct = nf_ct_expect_find_get(net, nf_ct_zone(ct), &t);
+		if (exp_ct) {
+			memcpy(&exp_ct->tuple.src.u3, &srvaddr, len);
+			if (sizeof(exp_ct->tuple.src.u3) > len)
+				/* address needs to be cleared for nf_ct_tuple_equal */
+				memset((void *)&exp_ct->tuple.src.u3 + len, 0,
+				       sizeof(exp_ct->tuple.src.u3) - len);
+		} else
+			goto out;
+
+		/* replace rtcp expect src addr */
+		if (expinfo.pbtype == pb_range || expinfo.pbtype == pb_discon) {
+			t.dst.u.all = htons(expinfo.hiport);
+
+			/* get the rtcp expect and replace the srcaddr with RTP server addr */
+			exp_ct = nf_ct_expect_find_get(net, nf_ct_zone(ct), &t);
+			if (exp_ct) {
+				memcpy(&exp_ct->tuple.src.u3, &srvaddr, len);
+				if (sizeof(exp_ct->tuple.src.u3) > len)
+					/* address needs to be cleared for nf_ct_tuple_equal */
+					memset((void *)&exp_ct->tuple.src.u3 + len, 0,
+					       sizeof(exp_ct->tuple.src.u3) - len);
+			} else
+				goto out;
+		}
+
+		goto out;
+	}
+out:
+	return ret;
+ }
+
+static int help(struct sk_buff *skb, unsigned int protoff,
+		struct nf_conn *ct, enum ip_conntrack_info ctinfo) 
+{
+	struct tcphdr _tcph, *th;
+	unsigned int dataoff, datalen;
+	char *rb_ptr;
+	int ret = NF_DROP;
+
+	/* Until there's been traffic both ways, don't look in packets. */
+	if (ctinfo != IP_CT_ESTABLISHED && 
+	    ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) {
+		pr_debug("conntrackinfo = %u\n", ctinfo);
+		return NF_ACCEPT;
+	} 
+
+	/* Not whole TCP header? */
+	th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
+
+	if (!th)
+		return NF_ACCEPT;
+   
+	/* No data ? */
+	dataoff = protoff + th->doff*4;
+	datalen = skb->len - dataoff;
+	if (dataoff >= skb->len)
+		return NF_ACCEPT;
+
+	spin_lock_bh(&rtsp_buffer_lock);
+	rb_ptr = skb_header_pointer(skb, dataoff,
+				    skb->len - dataoff, rtsp_buffer);
+	BUG_ON(rb_ptr == NULL);
+
+#if 0
+	/* Checksum invalid?  Ignore. */
+	/* FIXME: Source route IP option packets --RR */
+	if (tcp_v4_check(tcph, tcplen, iph->saddr, iph->daddr,
+			 csum_partial((char*)tcph, tcplen, 0)))
+	{
+		DEBUGP("bad csum: %p %u %u.%u.%u.%u %u.%u.%u.%u\n",
+		       tcph, tcplen, NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
+		return NF_ACCEPT;
+	}
+#endif
+
+	switch (CTINFO2DIR(ctinfo)) {
+	case IP_CT_DIR_ORIGINAL:
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+		ret = help_out(skb, rb_ptr, datalen, ct, ctinfo, protoff);
+#else
+		ret = help_out(skb, rb_ptr, datalen, ct, ctinfo);
+#endif
+		break;
+	case IP_CT_DIR_REPLY:
+		pr_debug("IP_CT_DIR_REPLY\n");
+		/* inbound packet: server->client */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+		ret = help_in(skb, rb_ptr, datalen, ct, ctinfo, protoff);
+#else
+		ret = help_in(skb, rb_ptr, datalen, ct, ctinfo);
+#endif
+		break;
+	default:
+		break;
+	}
+
+	spin_unlock_bh(&rtsp_buffer_lock);
+
+	return ret;
+}
+
+static struct nf_conntrack_helper rtsp_helpers[MAX_PORTS];
+static char rtsp_names[MAX_PORTS][10];
+
+/* This function is intentionally _NOT_ defined as __exit */
+static void
+fini(void)
+{
+	int i;
+	for (i = 0; i < num_ports; i++) {
+		pr_debug("unregistering port %d\n", ports[i]);
+		nf_conntrack_helper_unregister(&rtsp_helpers[i]);
+	}
+	kfree(rtsp_buffer);
+}
+
+static int __init
+init(void)
+{
+	int i, ret;
+	struct nf_conntrack_helper *hlpr;
+	char *tmpname;
+
+	printk("nf_conntrack_rtsp v" IP_NF_RTSP_VERSION " loading\n");
+
+	if (max_outstanding < 1) {
+		printk("nf_conntrack_rtsp: max_outstanding must be a positive integer\n");
+		return -EBUSY;
+	}
+
+	rtsp_exp_policy.max_expected = max_outstanding;
+	rtsp_exp_policy.timeout = setup_timeout;
+	
+	rtsp_buffer = kmalloc(65536, GFP_KERNEL);
+	if (!rtsp_buffer) 
+		return -ENOMEM;
+
+	/* If no port given, default to standard rtsp port */
+	if (ports[0] == 0) {
+		ports[0] = RTSP_PORT;
+		num_ports = 1;
+	}
+
+	for (i = 0; (i < MAX_PORTS) && ports[i]; i++) {
+		hlpr = &rtsp_helpers[i];
+		memset(hlpr, 0, sizeof(struct nf_conntrack_helper));
+		hlpr->tuple.src.l3num = AF_INET;
+		hlpr->tuple.src.u.tcp.port = htons(ports[i]);
+		hlpr->tuple.dst.protonum = IPPROTO_TCP;
+		hlpr->expect_policy = &rtsp_exp_policy;
+		hlpr->me = THIS_MODULE;
+		hlpr->help = help;
+
+		tmpname = &rtsp_names[i][0];
+		if (ports[i] == RTSP_PORT) {
+			sprintf(tmpname, "rtsp");
+		} else {
+			sprintf(tmpname, "rtsp-%d", i);
+		}
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,6,0)
+		strlcpy(hlpr->name, tmpname, sizeof(hlpr->name));
+#else
+		hlpr->name = tmpname;
+#endif
+		pr_debug("port #%d: %d\n", i, ports[i]);
+
+		ret = nf_conntrack_helper_register(hlpr);
+
+		if (ret) {
+			printk("nf_conntrack_rtsp: ERROR registering port %d\n", ports[i]);
+			fini();
+			return -EBUSY;
+		}
+	}
+	return 0;
+}
+
+module_init(init);
+module_exit(fini);
--- /dev/null
+++ b/extensions/rtsp/nf_conntrack_rtsp.h
@@ -0,0 +1,74 @@
+/*
+ * RTSP extension for IP connection tracking.
+ * (C) 2003 by Tom Marshall <tmarshall at real.com>
+ * based on ip_conntrack_irc.h
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ *
+ * 2013-03-04: Il'inykh Sergey <sergeyi at inango-sw.com>. Inango Systems Ltd
+ *	- conditional compilation for kernel 3.7
+ *	- port mapping improvements
+*/
+#ifndef _IP_CONNTRACK_RTSP_H
+#define _IP_CONNTRACK_RTSP_H
+
+#include <linux/version.h>
+
+//#define IP_NF_RTSP_DEBUG 1
+#define IP_NF_RTSP_VERSION "0.7"
+
+#ifdef __KERNEL__
+/* port block types */
+typedef enum {
+    pb_single,  /* client_port=x */
+    pb_range,   /* client_port=x-y */
+    pb_discon   /* client_port=x/y (rtspbis) */
+} portblock_t;
+
+/* We record seq number and length of rtsp headers here, all in host order. */
+
+/*
+ * This structure is per expected connection.  It is a member of struct
+ * ip_conntrack_expect.  The TCP SEQ for the conntrack expect is stored
+ * there and we are expected to only store the length of the data which
+ * needs replaced.  If a packet contains multiple RTSP messages, we create
+ * one expected connection per message.
+ *
+ * We use these variables to mark the entire header block.  This may seem
+ * like overkill, but the nature of RTSP requires it.  A header may appear
+ * multiple times in a message.  We must treat two Transport headers the
+ * same as one Transport header with two entries.
+ */
+struct ip_ct_rtsp_expect
+{
+    u_int32_t          len;        /* length of header block */
+    portblock_t        pbtype;     /* Type of port block that was requested */
+    u_int16_t          loport;     /* Port that was requested, low or first */
+    u_int16_t          hiport;     /* Port that was requested, high or second */
+    union nf_inet_addr srvaddr;    /* src address in SETUP reply */
+    union nf_inet_addr cltaddr;    /* destination address */
+#if 0
+    uint               method;     /* RTSP method */
+    uint               cseq;       /* CSeq from request */
+#endif
+};
+
+extern unsigned int (*nf_nat_rtsp_hook)(struct sk_buff *skb,
+					enum ip_conntrack_info ctinfo,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+					unsigned int protoff,
+#endif
+					unsigned int matchoff,
+					unsigned int matchlen,
+					struct ip_ct_rtsp_expect *prtspexp,
+					struct nf_conntrack_expect *rtp_exp,
+					struct nf_conntrack_expect *rtcp_exp);
+
+#define RTSP_PORT   554
+
+#endif /* __KERNEL__ */
+
+#endif /* _IP_CONNTRACK_RTSP_H */
--- /dev/null
+++ b/extensions/rtsp/nf_nat_rtsp.c
@@ -0,0 +1,640 @@
+/*
+ * RTSP extension for TCP NAT alteration
+ * (C) 2003 by Tom Marshall <tmarshall at real.com>
+ *
+ * 2013-03-04: Il'inykh Sergey <sergeyi at inango-sw.com>. Inango Systems Ltd
+ *	- fixed rtcp nat mapping and other port mapping fixes
+ *	- fixed system hard lock because of bug in the parser
+ *	- codestyle fixes and less significant fixes
+ *
+ * based on ip_nat_irc.c
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ *
+ * Module load syntax:
+ *	insmod nf_nat_rtsp.o ports=port1,port2,...port<MAX_PORTS>
+ *	                     stunaddr=<address>
+ *	                     destaction=[auto|strip|none]
+ *
+ * If no ports are specified, the default will be port 554 only.
+ *
+ * stunaddr specifies the address used to detect that a client is using STUN.
+ * If this address is seen in the destination parameter, it is assumed that
+ * the client has already punched a UDP hole in the firewall, so we don't
+ * mangle the client_port.  If none is specified, it is autodetected.  It
+ * only needs to be set if you have multiple levels of NAT.  It should be
+ * set to the external address that the STUN clients detect.  Note that in
+ * this case, it will not be possible for clients to use UDP with servers
+ * between the NATs.
+ *
+ * If no destaction is specified, auto is used.
+ *   destaction=auto:  strip destination parameter if it is not stunaddr.
+ *   destaction=strip: always strip destination parameter (not recommended).
+ *   destaction=none:  do not touch destination parameter (not recommended).
+ */
+
+#include <linux/module.h>
+#include <linux/version.h>
+#include <net/tcp.h>
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+# include <net/netfilter/nf_nat.h>
+#else
+# include <net/netfilter/nf_nat_rule.h>
+#endif
+#include <net/netfilter/nf_nat_helper.h>
+#include "nf_conntrack_rtsp.h"
+
+#include <linux/inet.h>
+#include <linux/ctype.h>
+#define NF_NEED_STRNCASECMP
+#define NF_NEED_STRTOU16
+#include "netfilter_helpers.h"
+#define NF_NEED_MIME_NEXTLINE
+#include "netfilter_mime.h"
+
+#define MAX_PORTS     8
+#define DSTACT_AUTO   0
+#define DSTACT_STRIP  1
+#define DSTACT_NONE   2
+
+static char* stunaddr = NULL;
+static char* destaction = NULL;
+
+static u_int32_t extip = 0;
+static int       dstact = 0;
+
+static void nf_nat_rtsp_expected(struct nf_conn* ct, struct nf_conntrack_expect *exp);
+
+MODULE_AUTHOR("Tom Marshall <tmarshall at real.com>");
+MODULE_DESCRIPTION("RTSP network address translation module");
+MODULE_LICENSE("GPL");
+module_param(stunaddr, charp, 0644);
+MODULE_PARM_DESC(stunaddr, "Address for detecting STUN");
+module_param(destaction, charp, 0644);
+MODULE_PARM_DESC(destaction, "Action for destination parameter (auto/strip/none)");
+
+#define SKIP_WSPACE(ptr,len,off) while(off < len && isspace(*(ptr+off))) { off++; }
+
+/*** helper functions ***/
+
+static void
+get_skb_tcpdata(struct sk_buff* skb, char** pptcpdata, uint* ptcpdatalen)
+{
+	struct iphdr*   iph  = ip_hdr(skb);
+	struct tcphdr*  tcph = (void *)iph + ip_hdrlen(skb);
+
+	*pptcpdata = (char*)tcph +  tcph->doff*4;
+	*ptcpdatalen = ((char*)skb_transport_header(skb) + skb->len) - *pptcpdata;
+}
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+/* copy of sip_sprintf_addr */
+static int rtsp_sprintf_addr(const struct nf_conn *ct, char *buffer,
+			     const union nf_inet_addr *addr, bool delim)
+{
+	if (nf_ct_l3num(ct) == NFPROTO_IPV4) {
+		return sprintf(buffer, "%pI4", &addr->ip);
+	} else {
+		if (delim)
+			return sprintf(buffer, "[%pI6c]", &addr->ip6);
+		else
+			return sprintf(buffer, "%pI6c", &addr->ip6);
+	}
+}
+#endif
+
+/*** nat functions ***/
+
+/*
+ * Mangle the "Transport:" header:
+ *   - Replace all occurences of "client_port=<spec>"
+ *   - Handle destination parameter
+ *
+ * In:
+ *   ct, ctinfo = conntrack context
+ *   skb        = packet
+ *   tranoff    = Transport header offset from TCP data
+ *   tranlen    = Transport header length (incl. CRLF)
+ *   rport_lo   = replacement low  port (host endian)
+ *   rport_hi   = replacement high port (host endian)
+ *
+ * Returns packet size difference.
+ *
+ * Assumes that a complete transport header is present, ending with CR or LF
+ */
+static int
+rtsp_mangle_tran(enum ip_conntrack_info ctinfo,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+		 unsigned int protoff,
+#endif
+		 struct nf_conntrack_expect* rtp_exp,
+		 struct nf_conntrack_expect* rtcp_exp,
+		 struct ip_ct_rtsp_expect* prtspexp,
+		 struct sk_buff* skb, uint tranoff, uint tranlen)
+{
+	char*  ptcp;
+	uint   tcplen;
+	char*  ptran;
+	char   rbuf1[16];	  /* Replacement buffer (one port) */
+	uint   rbuf1len;	  /* Replacement len (one port) */
+	char   rbufa[16];	  /* Replacement buffer (all ports) */
+	uint   rbufalen;	  /* Replacement len (all ports) */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+	union nf_inet_addr newip;
+#else
+	u_int32_t  newip;
+#endif
+	u_int16_t loport, hiport;
+	uint      off = 0;
+	uint      diff;		   /* Number of bytes we removed */
+
+	struct nf_conn *ct = rtp_exp->master;
+	/* struct nf_conn *ct = nf_ct_get(skb, &ctinfo); */
+	struct nf_conntrack_tuple *rtp_t;
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+	char szextaddr[INET6_ADDRSTRLEN + 16];
+#else
+	char szextaddr[INET_ADDRSTRLEN + 16];
+#endif
+	uint extaddrlen;
+	int  is_stun;
+
+	get_skb_tcpdata(skb, &ptcp, &tcplen);
+	ptran = ptcp+tranoff;
+
+	if (tranoff+tranlen > tcplen || tcplen-tranoff < tranlen ||
+	    tranlen < 10 || !iseol(ptran[tranlen-1]) ||
+	    nf_strncasecmp(ptran, "Transport:", 10) != 0) {
+		pr_info("sanity check failed\n");
+		return 0;
+	}
+	off += 10;
+	SKIP_WSPACE(ptcp+tranoff, tranlen, off);
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+	newip = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3;
+	rtp_t = &rtp_exp->tuple;
+	rtp_t->dst.u3 = newip;
+	if (rtcp_exp) {
+		rtcp_exp->tuple.dst.u3 = newip;
+	}
+	extaddrlen = rtsp_sprintf_addr(ct, szextaddr, &newip, true); // FIXME handle extip
+	pr_debug("stunaddr=%s (auto)\n", szextaddr);
+#else
+	newip = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip;
+	rtp_t = &rtp_exp->tuple;
+	rtp_t->dst.u3.ip = newip;
+	if (rtcp_exp) {
+		rtcp_exp->tuple.dst.u3.ip = newip;
+	}
+	extaddrlen = extip ? sprintf(szextaddr, "%pI4", &extip)
+			   : sprintf(szextaddr, "%pI4", &newip);
+	pr_debug("stunaddr=%s (%s)\n", szextaddr, (extip?"forced":"auto"));
+#endif
+	hiport = 0;
+	rbuf1len = rbufalen = 0;
+	switch (prtspexp->pbtype) {
+	case pb_single:
+		for (loport = prtspexp->loport; loport != 0; loport++) { /* XXX: improper wrap? */
+			rtp_t->dst.u.udp.port = htons(loport);
+			if (rtsp_nf_ct_expect_related(rtp_exp) == 0) {
+				pr_debug("using port %hu\n", loport);
+				break;
+			}
+		}
+		if (loport != 0) {
+			rbuf1len = sprintf(rbuf1, "%hu", loport);
+			rbufalen = sprintf(rbufa, "%hu", loport);
+		}
+		break;
+	case pb_range:
+		for (loport = prtspexp->loport; loport != 0; loport += 2) { /* XXX: improper wrap? */
+			rtp_t->dst.u.udp.port = htons(loport);
+			if (rtsp_nf_ct_expect_related(rtp_exp) != 0) {
+				continue;
+			}
+			hiport = loport + 1;
+			rtcp_exp->tuple.dst.u.udp.port = htons(hiport);
+			if (rtsp_nf_ct_expect_related(rtcp_exp) != 0) {
+				nf_ct_unexpect_related(rtp_exp);
+				continue;
+			}
+
+			/* FIXME: invalid print in case of ipv6 */
+			pr_debug("nat expect_related %pI4:%u-%u-%pI4:%u-%u\n",
+				 &rtp_exp->tuple.src.u3.ip,
+				 ntohs(rtp_exp->tuple.src.u.udp.port),
+				 ntohs(rtcp_exp->tuple.src.u.udp.port),
+				 &rtp_exp->tuple.dst.u3.ip,
+				 ntohs(rtp_exp->tuple.dst.u.udp.port),
+				 ntohs(rtcp_exp->tuple.dst.u.udp.port));
+			break;
+		}
+		if (loport != 0) {
+			rbuf1len = sprintf(rbuf1, "%hu", loport);
+			rbufalen = sprintf(rbufa, "%hu-%hu", loport, hiport);
+		}
+		break;
+	case pb_discon:
+		for (loport = prtspexp->loport; loport != 0; loport++) { /* XXX: improper wrap? */
+			rtp_t->dst.u.udp.port = htons(loport);
+			if (rtsp_nf_ct_expect_related(rtp_exp) == 0) {
+				pr_debug("using port %hu (1 of 2)\n", loport);
+				break;
+			}
+		}
+		for (hiport = prtspexp->hiport; hiport != 0; hiport++) { /* XXX: improper wrap? */
+			rtcp_exp->tuple.dst.u.udp.port = htons(hiport);
+			if (rtsp_nf_ct_expect_related(rtcp_exp) == 0) {
+				pr_debug("using port %hu (2 of 2)\n", hiport);
+				break;
+			}
+		}
+		if (loport != 0 && hiport != 0) {
+			rbuf1len = sprintf(rbuf1, "%hu", loport);
+			rbufalen = sprintf(rbufa, hiport == loport+1 ?
+					   "%hu-%hu":"%hu/%hu", loport, hiport);
+		} else {
+			if (loport != 0)
+				nf_ct_unexpect_related(rtp_exp);
+			if (hiport != 0)
+				nf_ct_unexpect_related(rtcp_exp);
+		}
+		break;
+	}
+
+	if (rbuf1len == 0)
+		return 0;   /* cannot get replacement port(s) */
+
+	/* Transport: tran;field;field=val,tran;field;field=val,...
+	   `off` is set to the start of Transport value from start of line
+	*/
+	while (off < tranlen) {
+		uint        saveoff;
+		const char* pparamend;
+		uint        nextparamoff;
+
+		pparamend = memchr(ptran+off, ',', tranlen-off);
+		pparamend = (pparamend == NULL) ? ptran+tranlen : pparamend+1;
+		nextparamoff = pparamend-ptran;
+
+		/*
+		 * We pass over each param twice.  On the first pass, we look for a
+		 * destination= field.  It is handled by the security policy.  If it
+		 * is present, allowed, and equal to our external address, we assume
+		 * that STUN is being used and we leave the client_port= field alone.
+		 */
+		is_stun = 0;
+		saveoff = off;
+		while (off < nextparamoff) {
+			const char* pfieldend;
+			uint        nextfieldoff;
+
+			pfieldend = memchr(ptran+off, ';', nextparamoff-off);
+			nextfieldoff = (pfieldend == NULL) ? nextparamoff : pfieldend-ptran+1;
+			SKIP_WSPACE(ptran, nextfieldoff, off);
+
+			if (dstact != DSTACT_NONE && nextfieldoff - off > 12 && strncmp(ptran+off, "destination=", 12) == 0) {
+				if (strncmp(ptran+off+12, szextaddr, extaddrlen) == 0)
+					is_stun = 1;
+
+				if (dstact == DSTACT_STRIP || (dstact == DSTACT_AUTO && !is_stun)) {
+					uint dstoff = (ptran-ptcp)+off;
+					uint dstlen = nextfieldoff-off;
+					char* pdstrep = NULL;
+					uint dstreplen = 0;
+					diff = dstlen;
+					if (dstact == DSTACT_AUTO && !is_stun) {
+						const char* psep = memchr(ptran+off, ':', dstlen);
+						u_int16_t port;
+
+						dstoff += 12;
+						dstlen -= 13;
+						pdstrep = szextaddr;
+
+						if (psep != NULL && nf_strtou16(psep + 1, &port)) {
+							pr_debug("RTSP: replace dst addr&port\n");
+
+							if (port != prtspexp->loport) {
+								pr_debug("multiple ports found, port %hu ignored\n", port);
+								dstreplen = extaddrlen;
+							} else {
+								sprintf(szextaddr+extaddrlen, ":%s", rbuf1);
+								dstreplen = extaddrlen+1+rbuf1len;
+							}
+						} else {
+							pr_debug("RTSP: replace dst addr\n");
+							dstreplen = extaddrlen;
+						}
+						diff = nextfieldoff-off-13-dstreplen;
+					}
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+					if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff,
+								      dstoff, dstlen, pdstrep, dstreplen)) {
+#else
+					if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
+								      dstoff, dstlen, pdstrep, dstreplen)) {
+#endif
+						/* mangle failed, all we can do is bail */
+						nf_ct_unexpect_related(rtp_exp);
+						if (rtcp_exp)
+							nf_ct_unexpect_related(rtcp_exp);
+						return 0;
+					}
+					get_skb_tcpdata(skb, &ptcp, &tcplen);
+					ptran = ptcp+tranoff;
+					tranlen -= diff;
+					nextparamoff -= diff;
+					nextfieldoff -= diff;
+				}
+			}
+
+			off = nextfieldoff;
+		}
+
+		if (is_stun)
+			continue;
+
+		off = saveoff;
+		while (off < nextparamoff) {
+			const char* pfieldend;
+			uint        nextfieldoff;
+
+			pfieldend = memchr(ptran+off, ';', nextparamoff-off);
+			nextfieldoff = (pfieldend == NULL) ? nextparamoff : pfieldend-ptran+1;
+
+			if (nextfieldoff - off > 12 && strncmp(ptran+off, "client_port=", 12) == 0) {
+				u_int16_t port;
+				uint	  numlen;
+				uint      origoff;
+				uint      origlen;
+				char*     rbuf = rbuf1;
+				uint      rbuflen = rbuf1len;
+
+				off += 12;
+				origoff = (ptran-ptcp)+off;
+				origlen = 0;
+				numlen = nf_strtou16(ptran+off, &port);
+				off += numlen;
+				origlen += numlen;
+				if (port != prtspexp->loport) {
+					pr_debug("multiple ports found, port %hu ignored\n", port);
+				} else {
+					if (ptran[off] == '-' || ptran[off] == '/') {
+						off++;
+						origlen++;
+						numlen = nf_strtou16(ptran+off, &port);
+						off += numlen;
+						origlen += numlen;
+						rbuf = rbufa;
+						rbuflen = rbufalen;
+					}
+
+					/*
+					 * note we cannot just memcpy() if the sizes are the same.
+					 * the mangle function does skb resizing, checks for a
+					 * cloned skb, and updates the checksums.
+					 *
+					 * parameter 4 below is offset from start of tcp data.
+					 */
+					diff = origlen-rbuflen;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+					if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff,
+								      origoff, origlen, rbuf, rbuflen)) {
+#else
+					if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
+								      origoff, origlen, rbuf, rbuflen)) {
+#endif
+						/* mangle failed, all we can do is bail */
+						nf_ct_unexpect_related(rtp_exp);
+						if (rtcp_exp)
+							nf_ct_unexpect_related(rtcp_exp);
+						return 0;
+					}
+					get_skb_tcpdata(skb, &ptcp, &tcplen);
+					ptran = ptcp+tranoff;
+					tranlen -= diff;
+					nextparamoff -= diff;
+					nextfieldoff -= diff;
+				}
+			}
+
+			off = nextfieldoff;
+		}
+
+		off = nextparamoff;
+	}
+
+	return 1;
+}
+
+static uint
+help_out(struct sk_buff *skb, enum ip_conntrack_info ctinfo,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+	 unsigned int protoff,
+#endif
+	 unsigned int matchoff, unsigned int matchlen,
+	 struct ip_ct_rtsp_expect* prtspexp,
+	 struct nf_conntrack_expect* rtp_exp,
+	 struct nf_conntrack_expect* rtcp_exp)
+{
+	char* ptcp;
+	uint  tcplen;
+	uint  hdrsoff;
+	uint  hdrslen;
+	uint  lineoff;
+	uint  linelen;
+	uint  off;
+	int   dir = CTINFO2DIR(ctinfo);
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+	union nf_inet_addr saddr = rtp_exp->master->tuplehash[dir].tuple.src.u3;
+#else
+	__be32 saddr = rtp_exp->master->tuplehash[dir].tuple.src.u3.ip;
+#endif
+
+	//struct iphdr* iph = (struct iphdr*)(*pskb)->nh.iph;
+	//struct tcphdr* tcph = (struct tcphdr*)((void*)iph + iph->ihl*4);
+
+	get_skb_tcpdata(skb, &ptcp, &tcplen);
+	hdrsoff = matchoff;//exp->seq - ntohl(tcph->seq);
+	hdrslen = matchlen;
+	off = hdrsoff;
+	pr_debug("NAT rtsp help_out\n");
+
+	while (nf_mime_nextline(ptcp, hdrsoff+hdrslen, &off, &lineoff, &linelen)) {
+		if (linelen == 0)
+			break;
+
+		if (off > hdrsoff+hdrslen) {
+			pr_info("!! overrun !!");
+			break;
+		}
+		pr_debug("hdr: len=%u, %.*s", linelen, (int)linelen, ptcp+lineoff);
+
+		if (nf_strncasecmp(ptcp+lineoff, "Transport:", 10) == 0) {
+			uint oldtcplen = tcplen;
+			pr_debug("hdr: Transport\n");
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+			if (!rtsp_mangle_tran(ctinfo, protoff, rtp_exp, rtcp_exp,
+					      prtspexp, skb, lineoff, linelen)) {
+#else
+			if (!rtsp_mangle_tran(ctinfo, rtp_exp, rtcp_exp, prtspexp,
+					      skb, lineoff, linelen)) {
+#endif
+				pr_debug("hdr: Transport mangle failed");
+				break;
+			}
+			rtp_exp->expectfn = nf_nat_rtsp_expected;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+			rtp_exp->saved_addr = saddr;
+#else
+			rtp_exp->saved_ip = saddr;
+#endif
+			rtp_exp->saved_proto.udp.port = htons(prtspexp->loport);
+			rtp_exp->dir = !dir;
+			if (rtcp_exp) {
+				rtcp_exp->expectfn = nf_nat_rtsp_expected;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+				rtcp_exp->saved_addr = saddr;
+#else
+				rtcp_exp->saved_ip = saddr;
+#endif
+				rtcp_exp->saved_proto.udp.port = htons(prtspexp->hiport);
+				rtcp_exp->dir = !dir;
+			}
+			get_skb_tcpdata(skb, &ptcp, &tcplen);
+			hdrslen -= (oldtcplen-tcplen);
+			off -= (oldtcplen-tcplen);
+			lineoff -= (oldtcplen-tcplen);
+			linelen -= (oldtcplen-tcplen);
+			pr_debug("rep: len=%u, %.*s", linelen, (int)linelen, ptcp+lineoff);
+		}
+	}
+
+	return NF_ACCEPT;
+}
+
+static unsigned int
+nf_nat_rtsp(struct sk_buff *skb, enum ip_conntrack_info ctinfo,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+	    unsigned int protoff,
+#endif
+	    unsigned int matchoff, unsigned int matchlen,
+	    struct ip_ct_rtsp_expect* prtspexp,
+	    struct nf_conntrack_expect* rtp_exp,
+	    struct nf_conntrack_expect* rtcp_exp)
+{
+	int dir = CTINFO2DIR(ctinfo);
+	int rc = NF_ACCEPT;
+
+	switch (dir) {
+	case IP_CT_DIR_ORIGINAL:
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+		rc = help_out(skb, ctinfo, protoff, matchoff, matchlen, prtspexp,
+			      rtp_exp, rtcp_exp);
+#else
+		rc = help_out(skb, ctinfo, matchoff, matchlen, prtspexp,
+			      rtp_exp, rtcp_exp);
+#endif
+		break;
+	case IP_CT_DIR_REPLY:
+		pr_debug("unmangle ! %u\n", ctinfo);
+		/* XXX: unmangle */
+		rc = NF_ACCEPT;
+		break;
+	}
+	//UNLOCK_BH(&ip_rtsp_lock);
+
+	return rc;
+}
+
+static void nf_nat_rtsp_expected(struct nf_conn* ct, struct nf_conntrack_expect *exp)
+{
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4,18,0)
+	struct nf_nat_range2 range;
+#elif LINUX_VERSION_CODE < KERNEL_VERSION(3,3,0) || LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+	struct nf_nat_range range;
+#else
+	struct nf_nat_ipv4_range range;
+#endif
+
+	/* This must be a fresh one. */
+	BUG_ON(ct->status & IPS_NAT_DONE_MASK);
+
+	/* For DST manip, map port here to where it's expected. */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+	range.min_proto = range.max_proto = exp->saved_proto;
+	range.min_addr = range.max_addr = exp->saved_addr;
+#else
+	range.min = range.max = exp->saved_proto;
+	range.min_ip = range.max_ip = exp->saved_ip;
+#endif
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,3,0)
+	range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED);
+	nf_nat_setup_info(ct, &range, NF_NAT_MANIP_DST);
+#else
+	range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
+	nf_nat_setup_info(ct, &range, IP_NAT_MANIP_DST);
+#endif
+
+	/* Change src to where master sends to, but only if the connection
+	 * actually came from the same source. */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
+	if (nf_inet_addr_cmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
+			     &ct->master->tuplehash[exp->dir].tuple.src.u3)) {
+		range.min_addr = range.max_addr
+			= ct->master->tuplehash[!exp->dir].tuple.dst.u3;
+#else
+	if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip ==
+	    ct->master->tuplehash[exp->dir].tuple.src.u3.ip) {
+		range.min_ip = range.max_ip
+			= ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
+#endif
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,3,0)
+		range.flags = NF_NAT_RANGE_MAP_IPS;
+		nf_nat_setup_info(ct, &range, NF_NAT_MANIP_SRC);
+#else
+		range.flags = IP_NAT_RANGE_MAP_IPS;
+		nf_nat_setup_info(ct, &range, IP_NAT_MANIP_SRC);
+#endif
+	}
+}
+
+
+static void __exit fini(void)
+{
+	rcu_assign_pointer(nf_nat_rtsp_hook, NULL);
+	synchronize_net();
+}
+
+static int __init init(void)
+{
+	printk("nf_nat_rtsp v" IP_NF_RTSP_VERSION " loading\n");
+
+	BUG_ON(nf_nat_rtsp_hook);
+	rcu_assign_pointer(nf_nat_rtsp_hook, nf_nat_rtsp);
+
+	if (stunaddr != NULL)
+		extip = in_aton(stunaddr);
+
+	if (destaction != NULL) {
+		if (strcmp(destaction, "auto") == 0)
+			dstact = DSTACT_AUTO;
+
+		if (strcmp(destaction, "strip") == 0)
+			dstact = DSTACT_STRIP;
+
+		if (strcmp(destaction, "none") == 0)
+			dstact = DSTACT_NONE;
+	}
+
+	return 0;
+}
+
+module_init(init);
+module_exit(fini);
--- a/extensions/Kbuild
+++ b/extensions/Kbuild
@@ -27,6 +27,7 @@ obj-${build_lscan}       += xt_lscan.o
 obj-${build_pknock}      += pknock/
 obj-${build_psd}         += xt_psd.o
 obj-${build_quota2}      += xt_quota2.o
+obj-${build_rtsp}        += rtsp/
 
 -include ${M}/*.Kbuild
 -include ${M}/Kbuild.*
--- a/mconfig
+++ b/mconfig
@@ -23,3 +23,4 @@ build_lscan=m
 build_pknock=m
 build_psd=m
 build_quota2=m
+build_rtsp=m
