diff --git a/nf_nat_rtsp.c b/nf_nat_rtsp.c
index 6be8346..3354e7b 100644
--- a/nf_nat_rtsp.c
+++ b/nf_nat_rtsp.c
@@ -82,13 +82,34 @@ MODULE_PARM_DESC(destaction, "Action for destination parameter (auto/strip/none)
 /*** helper functions ***/

 static void
-get_skb_tcpdata(struct sk_buff* skb, char** pptcpdata, uint* ptcpdatalen)
+get_skb_tcpdata(struct sk_buff* skb, char** pptcpdata, uint* ptcpdatalen, uint protoff)
 {
-	struct iphdr*   iph  = ip_hdr(skb);
-	struct tcphdr*  tcph = (void *)iph + ip_hdrlen(skb);
+	char* rtsp_buffer;
+	struct tcphdr _tcph, *th;
+	int datalen, dataoff;
+
+	rtsp_buffer = kmalloc(65536, GFP_KERNEL);
+
+        /* Not whole TCP header? */
+        th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
+	if (!th)
+	{
+		*ptcpdatalen = 0;
+		return;
+	}
+        /* No data ? */
+        dataoff = protoff + th->doff*4;
+	if (dataoff >= skb->len)
+	{
+		*ptcpdatalen = 0;
+		return;
+	}
+        datalen = skb->len - dataoff;
+
+	*pptcpdata = skb_header_pointer(skb, dataoff, datalen, rtsp_buffer);
+	*ptcpdatalen = datalen;

-	*pptcpdata = (char*)tcph +  tcph->doff*4;
-	*ptcpdatalen = ((char*)skb_transport_header(skb) + skb->len) - *pptcpdata;
+	kfree(rtsp_buffer);
 }

 #if LINUX_VERSION_CODE >= KERNEL_VERSION(3,7,0)
@@ -164,7 +185,7 @@ rtsp_mangle_tran(enum ip_conntrack_info ctinfo,
 	uint extaddrlen;
 	int  is_stun;

-	get_skb_tcpdata(skb, &ptcp, &tcplen);
+	get_skb_tcpdata(skb, &ptcp, &tcplen, protoff);
 	ptran = ptcp+tranoff;

 	if (tranoff+tranlen > tcplen || tcplen-tranoff < tranlen ||
@@ -325,7 +346,7 @@ rtsp_mangle_tran(enum ip_conntrack_info ctinfo,
 							nf_ct_unexpect_related(rtcp_exp);
 						return 0;
 					}
-					get_skb_tcpdata(skb, &ptcp, &tcplen);
+					get_skb_tcpdata(skb, &ptcp, &tcplen, protoff);
 					ptran = ptcp+tranoff;
 					tranlen -= diff;
 					nextparamoff -= diff;
@@ -395,7 +416,7 @@ rtsp_mangle_tran(enum ip_conntrack_info ctinfo,
 							nf_ct_unexpect_related(rtcp_exp);
 						return 0;
 					}
-					get_skb_tcpdata(skb, &ptcp, &tcplen);
+					get_skb_tcpdata(skb, &ptcp, &tcplen, protoff);
 					ptran = ptcp+tranoff;
 					tranlen -= diff;
 					nextparamoff -= diff;
@@ -439,7 +460,7 @@ help_out(struct sk_buff *skb, enum ip_conntrack_info ctinfo,
 	//struct iphdr* iph = (struct iphdr*)(*pskb)->nh.iph;
 	//struct tcphdr* tcph = (struct tcphdr*)((void*)iph + iph->ihl*4);

-	get_skb_tcpdata(skb, &ptcp, &tcplen);
+	get_skb_tcpdata(skb, &ptcp, &tcplen, protoff);
 	hdrsoff = matchoff;//exp->seq - ntohl(tcph->seq);
 	hdrslen = matchlen;
 	off = hdrsoff;
@@ -486,7 +507,7 @@ help_out(struct sk_buff *skb, enum ip_conntrack_info ctinfo,
 				rtcp_exp->saved_proto.udp.port = htons(prtspexp->hiport);
 				rtcp_exp->dir = !dir;
 			}
-			get_skb_tcpdata(skb, &ptcp, &tcplen);
+			get_skb_tcpdata(skb, &ptcp, &tcplen, protoff);
 			hdrslen -= (oldtcplen-tcplen);
 			off -= (oldtcplen-tcplen);
 			lineoff -= (oldtcplen-tcplen);