From: Samuel Jero <sj323707@ohio.edu>
Date: Sun, 17 Apr 2011 23:28:54 +0000 (-0400)
Subject: Split out the Ethernet/IPv4 encapsulation
X-Git-Url: http://sjero.net/git/?p=dccp2tcp;a=commitdiff_plain;h=a9d2edbab427f8e7e412db7a1bf9ecc26de679c3

Split out the Ethernet/IPv4 encapsulation

In preparation for a full fledged encapsulation layer.
---

diff --git a/Makefile b/Makefile
index 781ad03..5289c51 100644
--- a/Makefile
+++ b/Makefile
@@ -1,12 +1,12 @@
 ###############################################################################
 #Author: Samuel Jero
 #
-# Date: 10/2010
+# Date: 4/2011
 #
 # Makefile for program dccp2tcp
 ###############################################################################
 
-CFLAGS= -O2 -Wall -Werror
+CFLAGS= -O2 -Wall -Werror -g
 
 # for solaris, you probably want:
 #	LDLIBS = -lpcap -lnsl -lsocket
@@ -22,8 +22,14 @@ MANDIR = /usr/local/man
 
 all: dccp2tcp
 
-dccp2tcp: dccp2tcp.c dccp2tcp.h Makefile
-	gcc ${CFLAGS} ${LDLIBS} --std=gnu99 dccp2tcp.c -odccp2tcp
+dccp2tcp: dccp2tcp.o encap.o
+	gcc ${CFLAGS} ${LDLIBS} --std=gnu99 dccp2tcp.o encap.o -odccp2tcp
+
+dccp2tcp.o: dccp2tcp.h dccp2tcp.c
+	gcc ${CFLAGS} ${LDLIBS} --std=gnu99 -c dccp2tcp.c -odccp2tcp.o
+
+encap.o: encap.c dccp2tcp.h
+	gcc ${CFLAGS} ${LDLIBS} --std=gnu99 -c encap.c -oencap.o
 
 install: dccp2tcp
 	install -m 755 -o bin -g bin dccp2tcp ${BINDIR}/dccp2tcp
diff --git a/dccp2tcp.c b/dccp2tcp.c
index 12f6c45..193df2c 100644
--- a/dccp2tcp.c
+++ b/dccp2tcp.c
@@ -1,7 +1,7 @@
 /******************************************************************************
 Author: Samuel Jero
 
-Date: 2/2011
+Date: 4/2011
 
 Description: Program to convert a DCCP flow to a TCP flow for DCCP analysis via
 		tcptrace.
@@ -33,7 +33,7 @@ struct seq_num	*s2;	/*sequence number structure for side two of connection*/
 void PcapSavePacket(struct pcap_pkthdr *h, u_char *data);
 void process_packets();
 void handle_packet(u_char *user, const struct pcap_pkthdr *h, const u_char *bytes);
-void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata);
+void convert_packet(struct pcap_pkthdr *h, u_char **ndata, int *nlength, const u_char **odata, int *length);
 unsigned int interp_ack_vect(u_char* hdr);
 u_int32_t initialize_seq(struct seq_num **seq, __be16 source, __be32 initial);
 u_int32_t add_new_seq(struct seq_num *seq, __be32 num, int size, enum dccp_pkt_type type);
@@ -139,24 +139,35 @@ return 0;
 /*call back function for pcap_loop--do basic packet handling*/
 void handle_packet(u_char *user, const struct pcap_pkthdr *h, const u_char *bytes)
 {
-	u_char *ndata;
-	struct pcap_pkthdr nh;
+	u_char 				*ndata;
+	u_char 				*nptr;
+	int					length;
+	int					nlength;
+	struct pcap_pkthdr 	nh;
 
 	/*create new libpcap header*/
 	memcpy(&nh, h, sizeof(struct pcap_pkthdr));
+	length=h->caplen;
+	nlength=MAX_PACKET;
 
 	/*create buffer for new packet*/
-	ndata=malloc(MAX_PACKET);
+	nptr=ndata=malloc(MAX_PACKET);
 	if(ndata==NULL){
 		dbgprintf(0,"Error: Couldn't allocate Memory\n");
 		exit(1);
 	}
 
 	/*make sure the packet is all zero*/
-	memset(ndata, 0, MAX_PACKET);	
+	memset(nptr, 0, MAX_PACKET);
 	
 	/*do all the fancy conversions*/
-	convert_packet(&nh, bytes, ndata);
+	if(eth_ip_encap_pre(&nh, &nptr, &nlength, &bytes, &length)<0){
+		return;
+	}
+	convert_packet(&nh, &nptr, &nlength, &bytes, &length);
+	if(eth_ip_encap_post(&nh, &ndata, &nlength)<0){
+		return;
+	}
 
 	/*save packet*/
 	pcap_dump(user,&nh, ndata);
@@ -167,32 +178,20 @@ return;
 
 
 /*do all the dccp to tcp conversions*/
-void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
+void convert_packet(struct pcap_pkthdr *h, u_char **ndata, int *nlength, const u_char **odata, int *length)
 {	
-	u_char* ncur=ndata;
-	const u_char* ocur=odata;
-	int length=h->caplen;
-	struct iphdr *iph;
+	u_char* ncur=*ndata;
+	const u_char* ocur=*odata;
 	struct tcphdr *tcph;
 	struct dccp_hdr *dccph;
 	struct dccp_hdr_ext *dccphex;
 	struct dccp_hdr_ack_bits *dccphack;
 	int datalength;
+	int	len=0;
 	const u_char* pd;
 	u_char* npd;
 	u_char* tcpopt;
 
-	/*copy ethernet and ip headers over*/
-	memcpy(ncur, ocur, sizeof(struct ether_header)+sizeof(struct iphdr) );
-	ocur+=sizeof(struct ether_header)+ sizeof(struct iphdr);
-	ncur+=sizeof(struct ether_header) +sizeof(struct iphdr);
-	length-=sizeof(struct ether_header) +sizeof(struct iphdr);
-
-	/*set ip to indicate that tcp is next protocol*/
-	iph= (struct iphdr *) (ncur - sizeof(struct iphdr));
-	iph->protocol=6;
-	iph->check=htonl(0);
-
 	/*cast header pointers*/
 	tcph=(struct tcphdr*)ncur;
 	tcpopt=ncur+ sizeof(struct tcphdr);
@@ -203,8 +202,8 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 	dbgprintf(2,"Sequence Number: %llu\n", (unsigned long long)(((unsigned long)ntohs(dccph->dccph_seq)<<32) + ntohl(dccphex->dccph_seq_low)));
 
 	/*determine data length*/
-	datalength=ntohs(iph->tot_len) - sizeof(struct iphdr) - dccph->dccph_doff*4;
-	pd=odata + sizeof(struct ether_header)+sizeof(struct iphdr) + dccph->dccph_doff*4;
+	datalength=*length - dccph->dccph_doff*4;
+	pd=*odata + dccph->dccph_doff*4;
 
 	/*set tcp standard features*/
 	tcph->source=dccph->dccph_sport;
@@ -218,61 +217,61 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 		tcph->window=htons(30000);
 	}
 
+	/*Only accept the first connection*/
+	if(s1 && s2 && dccph->dccph_sport!=s1->addr && dccph->dccph_dport!=s1->addr){
+		return;
+	}
+
 	/*make changes by packet type*/
 	if(dccph->dccph_type==DCCP_PKT_REQUEST){//DCCP REQUEST -->TCP SYN
 		dbgprintf(2,"Packet Type: Request\n");
+		if(!s1){
+			if(yellow){
+				tcph->window=htons(0);
+			}
+			tcph->ack_seq=htonl(0);
+			tcph->seq=htonl(initialize_seq(&s1, dccph->dccph_sport, ntohl(dccphex->dccph_seq_low)));
+			tcph->syn=1;
+			tcph->ack=0;
+			tcph->fin=0;
+			tcph->rst=0;
 
-		if(yellow){
-			tcph->window=htons(0);
-		}
-		tcph->ack_seq=htonl(0);
-		tcph->seq=htonl(initialize_seq(&s1, dccph->dccph_sport, ntohl(dccphex->dccph_seq_low)));
-		tcph->syn=1;
-		tcph->ack=0;
-		tcph->fin=0;
-		tcph->rst=0;
+			/* add Sack-permitted option, if relevant*/
+			if(sack){
+				*tcpopt=4;
+				tcpopt++;
+				*tcpopt=2;
+				tcph->doff++;
+			}
 
-		/* add Sack-permitted option, if relevant*/
-		if(sack){
-			*tcpopt=4;
-			tcpopt++;
-			*tcpopt=2;
-			tcph->doff++;
+			/*calculate length*/
+			len=tcph->doff*4;
 		}
-
-		/*set libpcap header lengths*/
-		h->len=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4;
-		h->caplen=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4;
-
-		/*set length in ip header*/
-		iph->tot_len=htons(sizeof(struct iphdr) + tcph->doff*4);
 	}
 
 	if(dccph->dccph_type==DCCP_PKT_RESPONSE){//DCCP RESPONSE-->TCP SYN,ACK
 		dbgprintf(2,"Packet Type: Response\n");
-		tcph->ack_seq=htonl(convert_ack(s1,ntohl(dccphack->dccph_ack_nr_low)));
-		if(yellow){
-			tcph->window=htons(0);
-		}
-		tcph->seq=htonl(initialize_seq(&s2, dccph->dccph_sport, ntohl(dccphex->dccph_seq_low)));
-		tcph->syn=1;
-		tcph->ack=1;
-		tcph->fin=0;
-		tcph->rst=0;
-
-		/* add Sack-permitted option, if relevant*/
-		if(sack){
-			*tcpopt=4;
-			*(tcpopt+1)=2;
-			tcph->doff++;
-		}
+		if(s1 && !s2){
+			tcph->ack_seq=htonl(convert_ack(s1,ntohl(dccphack->dccph_ack_nr_low)));
+			if(yellow){
+				tcph->window=htons(0);
+			}
+			tcph->seq=htonl(initialize_seq(&s2, dccph->dccph_sport, ntohl(dccphex->dccph_seq_low)));
+			tcph->syn=1;
+			tcph->ack=1;
+			tcph->fin=0;
+			tcph->rst=0;
 
-		/*set libpcap header lengths*/
-		h->len=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4;
-		h->caplen=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4;
+			/* add Sack-permitted option, if relevant*/
+			if(sack){
+				*tcpopt=4;
+				*(tcpopt+1)=2;
+				tcph->doff++;
+			}
 
-		/*set length in ip header*/
-		iph->tot_len=htons(sizeof(struct iphdr) + tcph->doff*4);
+			/*calculate length*/
+			len=tcph->doff*4;
+		}
 	}
 
 	if(dccph->dccph_type==DCCP_PKT_DATA){//DCCP DATA----Never seen in packet capture
@@ -282,7 +281,7 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 
 	if(dccph->dccph_type==DCCP_PKT_DATAACK){//DCCP DATAACK-->TCP ACK with data
 		dbgprintf(2,"Packet Type: DataAck\n");
-		if(s1 && dccph->dccph_sport==s1->addr){ //determine which side of connection is sending this packet
+		if(s1 && s2 && dccph->dccph_sport==s1->addr){ //determine which side of connection is sending this packet
 			if(green){
 				tcph->ack_seq=htonl(convert_ack(s2,ntohl(dccphack->dccph_ack_nr_low)));
 			}else{
@@ -295,7 +294,7 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 			if(sack){
 				ack_vect2sack(s2, tcph, tcpopt, (u_char*)dccph, ntohl(dccphack->dccph_ack_nr_low) );
 			}
-		}else{
+		}else if(s1 && s2 && dccph->dccph_sport==s2->addr){
 			if(green){
 				tcph->ack_seq=htonl(convert_ack(s1,ntohl(dccphack->dccph_ack_nr_low)));
 			}else{
@@ -316,20 +315,16 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 		tcph->rst=0;
 
 		/*copy data*/
-		npd=ndata+ sizeof(struct ether_header)+sizeof(struct iphdr)+ tcph->doff*4;
+		npd=*ndata + tcph->doff*4;
 		memcpy(npd, pd, datalength);
 
-		/*set libpcap header lengths*/
-		h->len=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4 + datalength;
-		h->caplen=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4 + datalength;
-
-		/*set length in ip header*/
-		iph->tot_len=htons(sizeof(struct iphdr) + tcph->doff*4 + datalength);
+		/*calculate length*/
+		len= tcph->doff*4 + datalength;
 	}
 
 	if(dccph->dccph_type==DCCP_PKT_ACK){ //DCCP ACK -->TCP ACK with no data
 		dbgprintf(2,"Packet Type: Ack\n");
-		if(s1 && dccph->dccph_sport==s1->addr){//determine which side of connection is sending this packet
+		if(s1 && s2 && dccph->dccph_sport==s1->addr){//determine which side of connection is sending this packet
 			if(green){
 				tcph->ack_seq=htonl(convert_ack(s2,ntohl(dccphack->dccph_ack_nr_low)));
 			}else{
@@ -345,7 +340,7 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 			if(sack){
 				ack_vect2sack(s2, tcph, tcpopt, (u_char*)dccph, ntohl(dccphack->dccph_ack_nr_low) );
 			}
-		}else{
+		}else if(s1 && s2 && dccph->dccph_sport==s2->addr){
 			if(green){
 				tcph->ack_seq=htonl(convert_ack(s1,ntohl(dccphack->dccph_ack_nr_low)));
 			}else{
@@ -368,12 +363,8 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 		tcph->fin=0;
 		tcph->rst=0;
 
-		/*set libpcap header lengths*/
-		h->len=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4 + 1;
-		h->caplen=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4 + 1;
-
-		/*set length in ip header*/
-		iph->tot_len=htons(sizeof(struct iphdr) + tcph->doff*4 + 1);
+		/*calculate length*/
+		len=tcph->doff*4 + 1;
 	}
 
 	if(dccph->dccph_type==DCCP_PKT_CLOSEREQ){//DCCP CLOSEREQ----Never seen in packet capture
@@ -383,7 +374,7 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 
 	if(dccph->dccph_type==DCCP_PKT_CLOSE){//DCCP CLOSE-->TCP FIN,ACK
 		dbgprintf(2,"Packet Type: Close\n");
-		if(s1 && dccph->dccph_sport==s1->addr){//determine which side of connection is sending this packet
+		if(s1 && s2 && dccph->dccph_sport==s1->addr){//determine which side of connection is sending this packet
 			if(green){
 				tcph->ack_seq=htonl(convert_ack(s2,ntohl(dccphack->dccph_ack_nr_low)));
 			}else{
@@ -396,7 +387,7 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 			if(sack){
 				ack_vect2sack(s2, tcph, tcpopt, (u_char*)dccph, ntohl(dccphack->dccph_ack_nr_low) );
 			}
-		}else{
+		}else if(s1 && s2 && dccph->dccph_sport==s2->addr){
 			if(green){
 				tcph->ack_seq=htonl(convert_ack(s1,ntohl(dccphack->dccph_ack_nr_low)));
 			}else{
@@ -416,17 +407,13 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 		tcph->fin=1;
 		tcph->rst=0;
 
-		/*set libpcap header lengths*/
-		h->len=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4;
-		h->caplen=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4;
-
-		/*set length in ip header*/
-		iph->tot_len=htons(sizeof(struct iphdr) + tcph->doff*4);
+		/*calculate length*/
+		len=tcph->doff*4;
 	}
 
 	if(dccph->dccph_type==DCCP_PKT_RESET){//DCCP RESET-->TCP FIN,ACK (only seen at end of connection as CLOSE ACK)
 		dbgprintf(2,"Packet Type: Reset\n");
-		if(s1 && dccph->dccph_sport==s1->addr){//determine which side of connection is sending this packet
+		if(s1 && s2 && dccph->dccph_sport==s1->addr){//determine which side of connection is sending this packet
 			if(green){
 				tcph->ack_seq=htonl(convert_ack(s2,ntohl(dccphack->dccph_ack_nr_low)));
 			}else{
@@ -439,7 +426,7 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 			if(sack){
 				ack_vect2sack(s2, tcph, tcpopt, (u_char*)dccph, ntohl(dccphack->dccph_ack_nr_low) );
 			}
-		}else{
+		}else if(s1 && s2 && dccph->dccph_sport==s2->addr){
 			if(green){
 				tcph->ack_seq=htonl(convert_ack(s1,ntohl(dccphack->dccph_ack_nr_low)));
 			}else{
@@ -459,17 +446,13 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 		tcph->fin=1;
 		tcph->rst=0;
 
-		/*set libpcap header lengths*/
-		h->len=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4;
-		h->caplen=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4;
-
-		/*set length in ip header*/
-		iph->tot_len=htons(sizeof(struct iphdr) + tcph->doff*4);
+		/*calculate length*/
+		len=tcph->doff*4;
 	}
 
 	if(dccph->dccph_type==DCCP_PKT_SYNC){//DCCP SYNC
 		dbgprintf(2,"Packet Type: Sync\n");
-		if(s1 && dccph->dccph_sport==s1->addr){//determine which side of connection is sending this packet
+		if(s1 && s2 && dccph->dccph_sport==s1->addr){//determine which side of connection is sending this packet
 			if(green){
 				tcph->ack_seq=htonl(convert_ack(s2,ntohl(dccphack->dccph_ack_nr_low)));
 			}else{
@@ -484,7 +467,7 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 			if(sack){
 				ack_vect2sack(s2, tcph, tcpopt, (u_char*)dccph, ntohl(dccphack->dccph_ack_nr_low) );
 			}
-		}else{
+		}else if(s1 && s2 && dccph->dccph_sport==s2->addr){
 			if(green){
 				tcph->ack_seq=htonl(convert_ack(s1,ntohl(dccphack->dccph_ack_nr_low)));
 			}else{
@@ -506,17 +489,13 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 		tcph->fin=0;
 		tcph->rst=0;
 
-		/*set libpcap header lengths*/
-		h->len=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4+ 0;
-		h->caplen=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4+ 0;
-
-		/*set length in ip header*/
-		iph->tot_len=htons(sizeof(struct iphdr) + tcph->doff*4+0);
+		/*calculate length*/
+		len=tcph->doff*4;
 	}
 
 	if(dccph->dccph_type==DCCP_PKT_SYNCACK){//DCCP SYNACK
 		dbgprintf(2,"Packet Type: SyncAck\n");
-		if(s1 && dccph->dccph_sport==s1->addr){//determine which side of connection is sending this packet
+		if(s1 && s2 && dccph->dccph_sport==s1->addr){//determine which side of connection is sending this packet
 			if(green){
 				tcph->ack_seq=htonl(convert_ack(s2,ntohl(dccphack->dccph_ack_nr_low)));
 			}else{
@@ -531,7 +510,7 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 			if(sack){
 				ack_vect2sack(s2, tcph, tcpopt, (u_char*)dccph, ntohl(dccphack->dccph_ack_nr_low));
 			}
-		}else{
+		}else if(s1 && s2 && dccph->dccph_sport==s2->addr){
 			if(green){
 				tcph->ack_seq=htonl(convert_ack(s1,ntohl(dccphack->dccph_ack_nr_low)));
 			}else{
@@ -553,18 +532,16 @@ void convert_packet(struct pcap_pkthdr *h, const u_char *odata, u_char *ndata)
 		tcph->fin=0;
 		tcph->rst=0;
 
-		/*set libpcap header lengths*/
-		h->len=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4+0;
-		h->caplen=sizeof(struct ether_header) + sizeof(struct iphdr) + tcph->doff*4+0;
-
-		/*set length in ip header*/
-		iph->tot_len=htons(sizeof(struct iphdr) + tcph->doff*4+0);
+		/*calculate length*/
+		len=tcph->doff*4;
 	}
 
 	if(dccph->dccph_type==DCCP_PKT_INVALID){//DCCP INVALID----Never seen in packet capture
 		dbgprintf(0,"Invalid DCCP Packet!!\n");
 		exit(1);
 	}
+
+	*nlength=len;
 return;
 }
 
diff --git a/dccp2tcp.h b/dccp2tcp.h
index 6c08d28..3395339 100644
--- a/dccp2tcp.h
+++ b/dccp2tcp.h
@@ -1,13 +1,13 @@
 /******************************************************************************
 Author: Samuel Jero
 
-Date: 2/2011
+Date: 4/2011
 
 Description: Header file for program to convert a DCCP flow to a TCP flow for DCCP
  	 	 analysis via tcptrace.
 
 Notes:
-	1)Supports only a single DCCP contection per capture
+	1)Supports only a single DCCP connection per capture
 	2)Source Port!=Destination Port
 	3)DCCP MUST use 48 bit sequence numbers
 	4)Checksums are not computed (they are zeroed)
@@ -44,7 +44,7 @@ Notes:
 
 
 #define MAX_PACKET 	1600	/*Maximum size of TCP packet */
-#define	TBL_SZ		10000	/*Size of Sequence Number Table*/
+#define	TBL_SZ		40000	/*Size of Sequence Number Table*/
 
 
 
@@ -58,15 +58,15 @@ struct seq_num{
 
 /*sequence number table structure */
 struct tbl{
-	__be32 		old;	/*DCCP sequence number */
-	u_int32_t	new;	/*TCP sequence number */
-	int		size;		/*packet size*/
-	enum dccp_pkt_type type; /*packet type*/
+	__be32 				old;	/*DCCP sequence number */
+	u_int32_t			new;	/*TCP sequence number */
+	int					size;	/*packet size*/
+	enum dccp_pkt_type 	type;	/*packet type*/
 };
 
 /*Option flags*/
 extern int debug;		/*set to 1 to turn on debugging information*/
-extern int yellow;	/*tcptrace yellow line as currently acked packet*/
+extern int yellow;		/*tcptrace yellow line as currently acked packet*/
 extern int green;		/*tcptrace green line as currently acked packet*/
 extern int sack;		/*add TCP SACKS*/
 
@@ -83,5 +83,11 @@ extern struct seq_num	*s2;	/*sequence number structure for side two of connectio
  */
 void dbgprintf(int level, const char *fmt, ...);
 
+/* Encapsulation functions*/
+int eth_ip_encap_pre(struct pcap_pkthdr *h, u_char **nptr, int *nlength, const u_char **optr, int *length);
+int eth_ip_encap_post(struct pcap_pkthdr *h, u_char** nptr, int *nlength);
+
+/*The Conversion Function*/
+void convert_packet(struct pcap_pkthdr *h, u_char **ndata, int *nlength, const u_char **odata, int *length);
 
 #endif