diff --git a/print-tcp.c b/print-tcp.c
new file mode 100644
index 0000000..11bd6b7
--- /dev/null
+++ b/print-tcp.c
@@ -0,0 +1,807 @@
+/*
+ * Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * Copyright (c) 1999-2004 The tcpdump.org project
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that: (1) source code distributions
+ * retain the above copyright notice and this paragraph in its entirety, (2)
+ * distributions including binary code include the above copyright notice and
+ * this paragraph in its entirety in the documentation or other materials
+ * provided with the distribution, and (3) all advertising materials mentioning
+ * features or use of this software display the following acknowledgement:
+ * ``This product includes software developed by the University of California,
+ * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
+ * the University nor the names of its contributors may be used to endorse
+ * or promote products derived from this software without specific prior
+ * written permission.
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+#ifndef lint
+static const char rcsid[] _U_ =
+    "@(#) $Header: /tcpdump/master/tcpdump/print-tcp.c,v 1.120.2.3 2005/10/16 06:05:46 guy Exp $ (LBL)";
+#endif
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <tcpdump-stdinc.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "interface.h"
+#include "addrtoname.h"
+#include "extract.h"
+
+#include "tcp.h"
+
+#include "ip.h"
+#ifdef INET6
+#include "ip6.h"
+#endif
+#include "ipproto.h"
+#include "rpc_auth.h"
+#include "rpc_msg.h"
+
+#include "nameser.h"
+
+#ifdef HAVE_LIBCRYPTO
+#include <openssl/md5.h>
+
+#define SIGNATURE_VALID		0
+#define SIGNATURE_INVALID	1
+#define CANT_CHECK_SIGNATURE	2
+
+static int tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,
+    const u_char *data, int length, const u_char *rcvsig);
+#endif
+
+static void print_tcp_rst_data(register const u_char *sp, u_int length);
+
+#define MAX_RST_DATA_LEN	30
+
+
+struct tha {
+#ifndef INET6
+	struct in_addr src;
+	struct in_addr dst;
+#else
+	struct in6_addr src;
+	struct in6_addr dst;
+#endif /*INET6*/
+	u_int port;
+};
+
+struct tcp_seq_hash {
+	struct tcp_seq_hash *nxt;
+	struct tha addr;
+	tcp_seq seq;
+	tcp_seq ack;
+};
+
+#define TSEQ_HASHSIZE 919
+
+/* These tcp optinos do not have the size octet */
+#define ZEROLENOPT(o) ((o) == TCPOPT_EOL || (o) == TCPOPT_NOP)
+
+static struct tcp_seq_hash tcp_seq_hash[TSEQ_HASHSIZE];
+
+
+#ifndef TELNET_PORT
+#define TELNET_PORT	23
+#endif
+#ifndef BGP_PORT
+#define BGP_PORT	179
+#endif
+#define NETBIOS_SSN_PORT 139
+#ifndef PPTP_PORT
+#define PPTP_PORT	1723
+#endif
+#define BEEP_PORT        10288
+#ifndef NFS_PORT
+#define NFS_PORT	2049
+#endif
+#define MSDP_PORT	639
+#define LDP_PORT        646
+
+static int tcp_cksum(register const struct ip *ip,
+		     register const struct tcphdr *tp,
+		     register u_int len)
+{
+	union phu {
+		struct phdr {
+			u_int32_t src;
+			u_int32_t dst;
+			u_char mbz;
+			u_char proto;
+			u_int16_t len;
+		} ph;
+		u_int16_t pa[6];
+	} phu;
+	const u_int16_t *sp;
+
+	/* pseudo-header.. */
+	phu.ph.len = htons((u_int16_t)len);
+	phu.ph.mbz = 0;
+	phu.ph.proto = IPPROTO_TCP;
+	memcpy(&phu.ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
+	if (IP_HL(ip) == 5)
+		memcpy(&phu.ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
+	else
+		phu.ph.dst = ip_finddst(ip);
+
+	sp = &phu.pa[0];
+	return in_cksum((u_short *)tp, len,
+			sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5]);
+}
+
+#ifdef INET6
+static int tcp6_cksum(const struct ip6_hdr *ip6, const struct tcphdr *tp,
+	u_int len)
+{
+	size_t i;
+	register const u_int16_t *sp;
+	u_int32_t sum;
+	union {
+		struct {
+			struct in6_addr ph_src;
+			struct in6_addr ph_dst;
+			u_int32_t	ph_len;
+			u_int8_t	ph_zero[3];
+			u_int8_t	ph_nxt;
+		} ph;
+		u_int16_t pa[20];
+	} phu;
+
+	/* pseudo-header */
+	memset(&phu, 0, sizeof(phu));
+	phu.ph.ph_src = ip6->ip6_src;
+	phu.ph.ph_dst = ip6->ip6_dst;
+	phu.ph.ph_len = htonl(len);
+	phu.ph.ph_nxt = IPPROTO_TCP;
+
+	sum = 0;
+	for (i = 0; i < sizeof(phu.pa) / sizeof(phu.pa[0]); i++)
+		sum += phu.pa[i];
+
+	sp = (const u_int16_t *)tp;
+
+	for (i = 0; i < (len & ~1); i += 2)
+		sum += *sp++;
+
+	if (len & 1)
+		sum += htons((*(const u_int8_t *)sp) << 8);
+
+	while (sum > 0xffff)
+		sum = (sum & 0xffff) + (sum >> 16);
+	sum = ~sum & 0xffff;
+
+	return (sum);
+}
+#endif
+
+void
+tcp_print(register const u_char *bp, register u_int length,
+	  register const u_char *bp2, int fragmented)
+{
+	register const struct tcphdr *tp;
+	register const struct ip *ip;
+	register u_char flags;
+	register u_int hlen;
+	register char ch;
+	u_int16_t sport, dport, win, urp;
+	u_int32_t seq, ack, thseq, thack;
+	int threv;
+#ifdef INET6
+	register const struct ip6_hdr *ip6;
+#endif
+
+	tp = (struct tcphdr *)bp;
+	ip = (struct ip *)bp2;
+#ifdef INET6
+	if (IP_V(ip) == 6)
+		ip6 = (struct ip6_hdr *)bp2;
+	else
+		ip6 = NULL;
+#endif /*INET6*/
+	ch = '\0';
+	if (!TTEST(tp->th_dport)) {
+		(void)printf("%s > %s: [|tcp]",
+			ipaddr_string(&ip->ip_src),
+			ipaddr_string(&ip->ip_dst));
+		return;
+	}
+
+	sport = EXTRACT_16BITS(&tp->th_sport);
+	dport = EXTRACT_16BITS(&tp->th_dport);
+
+	hlen = TH_OFF(tp) * 4;
+
+	/*
+	 * If data present, header length valid, and NFS port used,
+	 * assume NFS.
+	 * Pass offset of data plus 4 bytes for RPC TCP msg length
+	 * to NFS print routines.
+	 */
+	if (!qflag && hlen >= sizeof(*tp) && hlen <= length) {
+		if ((u_char *)tp + 4 + sizeof(struct sunrpc_msg) <= snapend &&
+		    dport == NFS_PORT) {
+			nfsreq_print((u_char *)tp + hlen + 4, length - hlen,
+				     (u_char *)ip);
+			return;
+		} else if ((u_char *)tp + 4 + sizeof(struct sunrpc_msg)
+			   <= snapend &&
+			   sport == NFS_PORT) {
+			nfsreply_print((u_char *)tp + hlen + 4, length - hlen,
+				       (u_char *)ip);
+			return;
+		}
+	}
+#ifdef INET6
+	if (ip6) {
+		if (ip6->ip6_nxt == IPPROTO_TCP) {
+			(void)printf("%s.%s > %s.%s: ",
+				ip6addr_string(&ip6->ip6_src),
+				tcpport_string(sport),
+				ip6addr_string(&ip6->ip6_dst),
+				tcpport_string(dport));
+		} else {
+			(void)printf("%s > %s: ",
+				tcpport_string(sport), tcpport_string(dport));
+		}
+	} else
+#endif /*INET6*/
+	{
+		if (ip->ip_p == IPPROTO_TCP) {
+			(void)printf("%s.%s > %s.%s: ",
+				ipaddr_string(&ip->ip_src),
+				tcpport_string(sport),
+				ipaddr_string(&ip->ip_dst),
+				tcpport_string(dport));
+		} else {
+			(void)printf("%s > %s: ",
+				tcpport_string(sport), tcpport_string(dport));
+		}
+	}
+
+	if (hlen < sizeof(*tp)) {
+		(void)printf(" tcp %d [bad hdr length %u - too short, < %lu]",
+		    length - hlen, hlen, (unsigned long)sizeof(*tp));
+		return;
+	}
+
+	TCHECK(*tp);
+
+	seq = EXTRACT_32BITS(&tp->th_seq);
+	ack = EXTRACT_32BITS(&tp->th_ack);
+	win = EXTRACT_16BITS(&tp->th_win);
+	urp = EXTRACT_16BITS(&tp->th_urp);
+
+	if (qflag) {
+		(void)printf("tcp %d", length - hlen);
+		if (hlen > length) {
+			(void)printf(" [bad hdr length %u - too long, > %u]",
+			    hlen, length);
+		}
+		return;
+	}
+	if ((flags = tp->th_flags) & (TH_SYN|TH_FIN|TH_RST|TH_PUSH|
+				      TH_ECNECHO|TH_CWR)) {
+		if (flags & TH_SYN)
+			putchar('S');
+		if (flags & TH_FIN)
+			putchar('F');
+		if (flags & TH_RST)
+			putchar('R');
+		if (flags & TH_PUSH)
+			putchar('P');
+		if (flags & TH_CWR)
+			putchar('W');	/* congestion _W_indow reduced (ECN) */
+		if (flags & TH_ECNECHO)
+			putchar('E');	/* ecn _E_cho sent (ECN) */
+	} else
+		putchar('.');
+
+	if (!Sflag && (flags & TH_ACK)) {
+		register struct tcp_seq_hash *th;
+		const void *src, *dst;
+		register int rev;
+		struct tha tha;
+		/*
+		 * Find (or record) the initial sequence numbers for
+		 * this conversation.  (we pick an arbitrary
+		 * collating order so there's only one entry for
+		 * both directions).
+		 */
+#ifdef INET6
+		memset(&tha, 0, sizeof(tha));
+		rev = 0;
+		if (ip6) {
+			src = &ip6->ip6_src;
+			dst = &ip6->ip6_dst;
+			if (sport > dport)
+				rev = 1;
+			else if (sport == dport) {
+				if (memcmp(src, dst, sizeof ip6->ip6_dst) > 0)
+					rev = 1;
+			}
+			if (rev) {
+				memcpy(&tha.src, dst, sizeof ip6->ip6_dst);
+				memcpy(&tha.dst, src, sizeof ip6->ip6_src);
+				tha.port = dport << 16 | sport;
+			} else {
+				memcpy(&tha.dst, dst, sizeof ip6->ip6_dst);
+				memcpy(&tha.src, src, sizeof ip6->ip6_src);
+				tha.port = sport << 16 | dport;
+			}
+		} else {
+			src = &ip->ip_src;
+			dst = &ip->ip_dst;
+			if (sport > dport)
+				rev = 1;
+			else if (sport == dport) {
+				if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
+					rev = 1;
+			}
+			if (rev) {
+				memcpy(&tha.src, dst, sizeof ip->ip_dst);
+				memcpy(&tha.dst, src, sizeof ip->ip_src);
+				tha.port = dport << 16 | sport;
+			} else {
+				memcpy(&tha.dst, dst, sizeof ip->ip_dst);
+				memcpy(&tha.src, src, sizeof ip->ip_src);
+				tha.port = sport << 16 | dport;
+			}
+		}
+#else
+		rev = 0;
+		src = &ip->ip_src;
+		dst = &ip->ip_dst;
+		if (sport > dport)
+			rev = 1;
+		else if (sport == dport) {
+			if (memcmp(src, dst, sizeof ip->ip_dst) > 0)
+				rev = 1;
+		}
+		if (rev) {
+			memcpy(&tha.src, dst, sizeof ip->ip_dst);
+			memcpy(&tha.dst, src, sizeof ip->ip_src);
+			tha.port = dport << 16 | sport;
+		} else {
+			memcpy(&tha.dst, dst, sizeof ip->ip_dst);
+			memcpy(&tha.src, src, sizeof ip->ip_src);
+			tha.port = sport << 16 | dport;
+		}
+#endif
+
+		threv = rev;
+		for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];
+		     th->nxt; th = th->nxt)
+			if (memcmp((char *)&tha, (char *)&th->addr,
+				  sizeof(th->addr)) == 0)
+				break;
+
+		if (!th->nxt || (flags & TH_SYN)) {
+			/* didn't find it or new conversation */
+			if (th->nxt == NULL) {
+				th->nxt = (struct tcp_seq_hash *)
+					calloc(1, sizeof(*th));
+				if (th->nxt == NULL)
+					error("tcp_print: calloc");
+			}
+			th->addr = tha;
+			if (rev)
+				th->ack = seq, th->seq = ack - 1;
+			else
+				th->seq = seq, th->ack = ack - 1;
+		} else {
+			if (rev)
+				seq -= th->ack, ack -= th->seq;
+			else
+				seq -= th->seq, ack -= th->ack;
+		}
+
+		thseq = th->seq;
+		thack = th->ack;
+	} else {
+		/*fool gcc*/
+		thseq = thack = threv = 0;
+	}
+	if (hlen > length) {
+		(void)printf(" [bad hdr length %u - too long, > %u]",
+		    hlen, length);
+		return;
+	}
+
+	if (IP_V(ip) == 4 && vflag && !fragmented) {
+		u_int16_t sum, tcp_sum;
+		if (TTEST2(tp->th_sport, length)) {
+			sum = tcp_cksum(ip, tp, length);
+
+                        (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
+			if (sum != 0) {
+				tcp_sum = EXTRACT_16BITS(&tp->th_sum);
+				(void)printf(" (incorrect (-> 0x%04x),",in_cksum_shouldbe(tcp_sum, sum));
+			} else
+				(void)printf(" (correct),");
+		}
+	}
+#ifdef INET6
+	if (IP_V(ip) == 6 && ip6->ip6_plen && vflag && !fragmented) {
+		u_int16_t sum,tcp_sum;
+		if (TTEST2(tp->th_sport, length)) {
+			sum = tcp6_cksum(ip6, tp, length);
+                        (void)printf(", cksum 0x%04x",EXTRACT_16BITS(&tp->th_sum));
+			if (sum != 0) {
+				tcp_sum = EXTRACT_16BITS(&tp->th_sum);
+				(void)printf(" (incorrect (-> 0x%04x),",in_cksum_shouldbe(tcp_sum, sum));
+			} else
+				(void)printf(" (correct),");
+
+		}
+	}
+#endif
+
+	length -= hlen;
+	if (vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST))
+		(void)printf(" %u:%u(%u)", seq, seq + length, length);
+	if (flags & TH_ACK)
+		(void)printf(" ack %u", ack);
+
+	(void)printf(" win %d", win);
+
+	if (flags & TH_URG)
+		(void)printf(" urg %d", urp);
+	/*
+	 * Handle any options.
+	 */
+	if (hlen > sizeof(*tp)) {
+		register const u_char *cp;
+		register u_int i, opt, datalen;
+		register u_int len;
+
+		hlen -= sizeof(*tp);
+		cp = (const u_char *)tp + sizeof(*tp);
+		putchar(' ');
+		ch = '<';
+		while (hlen > 0) {
+			putchar(ch);
+			TCHECK(*cp);
+			opt = *cp++;
+			if (ZEROLENOPT(opt))
+				len = 1;
+			else {
+				TCHECK(*cp);
+				len = *cp++;	/* total including type, len */
+				if (len < 2 || len > hlen)
+					goto bad;
+				--hlen;		/* account for length byte */
+			}
+			--hlen;			/* account for type byte */
+			datalen = 0;
+
+/* Bail if "l" bytes of data are not left or were not captured  */
+#define LENCHECK(l) { if ((l) > hlen) goto bad; TCHECK2(*cp, l); }
+
+			switch (opt) {
+
+			case TCPOPT_MAXSEG:
+				(void)printf("mss");
+				datalen = 2;
+				LENCHECK(datalen);
+				(void)printf(" %u", EXTRACT_16BITS(cp));
+
+				break;
+
+			case TCPOPT_EOL:
+				(void)printf("eol");
+				break;
+
+			case TCPOPT_NOP:
+				(void)printf("nop");
+				break;
+
+			case TCPOPT_WSCALE:
+				(void)printf("wscale");
+				datalen = 1;
+				LENCHECK(datalen);
+				(void)printf(" %u", *cp);
+				break;
+
+			case TCPOPT_SACKOK:
+				(void)printf("sackOK");
+				break;
+
+			case TCPOPT_SACK:
+				datalen = len - 2;
+				if (datalen % 8 != 0) {
+					(void)printf("malformed sack");
+				} else {
+					u_int32_t s, e;
+
+					(void)printf("sack %d ", datalen / 8);
+					for (i = 0; i < datalen; i += 8) {
+						LENCHECK(i + 4);
+						s = EXTRACT_32BITS(cp + i);
+						LENCHECK(i + 8);
+						e = EXTRACT_32BITS(cp + i + 4);
+						if (threv) {
+							s -= thseq;
+							e -= thseq;
+						} else {
+							s -= thack;
+							e -= thack;
+						}
+						(void)printf("{%u:%u}", s, e);
+					}
+				}
+				break;
+
+			case TCPOPT_ECHO:
+				(void)printf("echo");
+				datalen = 4;
+				LENCHECK(datalen);
+				(void)printf(" %u", EXTRACT_32BITS(cp));
+				break;
+
+			case TCPOPT_ECHOREPLY:
+				(void)printf("echoreply");
+				datalen = 4;
+				LENCHECK(datalen);
+				(void)printf(" %u", EXTRACT_32BITS(cp));
+				break;
+
+			case TCPOPT_TIMESTAMP:
+				(void)printf("timestamp");
+				datalen = 8;
+				LENCHECK(4);
+				(void)printf(" %u", EXTRACT_32BITS(cp));
+				LENCHECK(datalen);
+				(void)printf(" %u", EXTRACT_32BITS(cp + 4));
+				break;
+
+			case TCPOPT_CC:
+				(void)printf("cc");
+				datalen = 4;
+				LENCHECK(datalen);
+				(void)printf(" %u", EXTRACT_32BITS(cp));
+				break;
+
+			case TCPOPT_CCNEW:
+				(void)printf("ccnew");
+				datalen = 4;
+				LENCHECK(datalen);
+				(void)printf(" %u", EXTRACT_32BITS(cp));
+				break;
+
+			case TCPOPT_CCECHO:
+				(void)printf("ccecho");
+				datalen = 4;
+				LENCHECK(datalen);
+				(void)printf(" %u", EXTRACT_32BITS(cp));
+				break;
+
+			case TCPOPT_SIGNATURE:
+				(void)printf("md5:");
+				datalen = TCP_SIGLEN;
+				LENCHECK(datalen);
+#ifdef HAVE_LIBCRYPTO
+				switch (tcp_verify_signature(ip, tp,
+				    bp + TH_OFF(tp) * 4, length, cp)) {
+
+				case SIGNATURE_VALID:
+					(void)printf("valid");
+					break;
+
+				case SIGNATURE_INVALID:
+					(void)printf("invalid");
+					break;
+
+				case CANT_CHECK_SIGNATURE:
+					(void)printf("can't check - ");
+					for (i = 0; i < TCP_SIGLEN; ++i)
+						(void)printf("%02x", cp[i]);
+					break;
+				}
+#else
+				for (i = 0; i < TCP_SIGLEN; ++i)
+					(void)printf("%02x", cp[i]);
+#endif
+				break;
+
+			default:
+				(void)printf("opt-%u:", opt);
+				datalen = len - 2;
+				for (i = 0; i < datalen; ++i) {
+					LENCHECK(i);
+					(void)printf("%02x", cp[i]);
+				}
+				break;
+			}
+
+			/* Account for data printed */
+			cp += datalen;
+			hlen -= datalen;
+
+			/* Check specification against observed length */
+			++datalen;			/* option octet */
+			if (!ZEROLENOPT(opt))
+				++datalen;		/* size octet */
+			if (datalen != len)
+				(void)printf("[len %d]", len);
+			ch = ',';
+			if (opt == TCPOPT_EOL)
+				break;
+		}
+		putchar('>');
+	}
+
+	if (length <= 0)
+		return;
+
+	/*
+	 * Decode payload if necessary.
+	 */
+	bp += TH_OFF(tp) * 4;
+	if (flags & TH_RST) {
+		if (vflag)
+			print_tcp_rst_data(bp, length);
+	} else {
+		if (sport == TELNET_PORT || dport == TELNET_PORT) {
+			if (!qflag && vflag)
+				telnet_print(bp, length);
+		} else if (sport == BGP_PORT || dport == BGP_PORT)
+			bgp_print(bp, length);
+		else if (sport == PPTP_PORT || dport == PPTP_PORT)
+			pptp_print(bp);
+#ifdef TCPDUMP_DO_SMB
+		else if (sport == NETBIOS_SSN_PORT || dport == NETBIOS_SSN_PORT)
+			nbt_tcp_print(bp, length);
+#endif
+		else if (sport == BEEP_PORT || dport == BEEP_PORT)
+			beep_print(bp, length);
+		else if (length > 2 &&
+		    (sport == NAMESERVER_PORT || dport == NAMESERVER_PORT ||
+		     sport == MULTICASTDNS_PORT || dport == MULTICASTDNS_PORT)) {
+			/*
+			 * TCP DNS query has 2byte length at the head.
+			 * XXX packet could be unaligned, it can go strange
+			 */
+			ns_print(bp + 2, length - 2, 0);
+		} else if (sport == MSDP_PORT || dport == MSDP_PORT) {
+			msdp_print(bp, length);
+		}
+                else if (length > 0 && (sport == LDP_PORT || dport == LDP_PORT)) {
+                        ldp_print(bp, length);
+		}
+	}
+	return;
+bad:
+	fputs("[bad opt]", stdout);
+	if (ch != '\0')
+		putchar('>');
+	return;
+trunc:
+	fputs("[|tcp]", stdout);
+	if (ch != '\0')
+		putchar('>');
+}
+
+/*
+ * RFC1122 says the following on data in RST segments:
+ *
+ *         4.2.2.12  RST Segment: RFC-793 Section 3.4
+ *
+ *            A TCP SHOULD allow a received RST segment to include data.
+ *
+ *            DISCUSSION
+ *                 It has been suggested that a RST segment could contain
+ *                 ASCII text that encoded and explained the cause of the
+ *                 RST.  No standard has yet been established for such
+ *                 data.
+ *
+ */
+
+static void
+print_tcp_rst_data(register const u_char *sp, u_int length)
+{
+	int c;
+
+	if (TTEST2(*sp, length))
+		printf(" [RST");
+	else
+		printf(" [!RST");
+	if (length > MAX_RST_DATA_LEN) {
+		length = MAX_RST_DATA_LEN;	/* can use -X for longer */
+		putchar('+');			/* indicate we truncate */
+	}
+	putchar(' ');
+	while (length-- && sp <= snapend) {
+		c = *sp++;
+		safeputchar(c);
+	}
+	putchar(']');
+}
+
+#ifdef HAVE_LIBCRYPTO
+static int
+tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,
+    const u_char *data, int length, const u_char *rcvsig)
+{
+        struct tcphdr tp1;
+	u_char sig[TCP_SIGLEN];
+	char zero_proto = 0;
+	MD5_CTX ctx;
+	u_int16_t savecsum, tlen;
+#ifdef INET6
+	struct ip6_hdr *ip6;
+#endif
+	u_int32_t len32;
+	u_int8_t nxt;
+
+	tp1 = *tp;
+
+	if (tcpmd5secret == NULL)
+		return (CANT_CHECK_SIGNATURE);
+
+	MD5_Init(&ctx);
+	/*
+	 * Step 1: Update MD5 hash with IP pseudo-header.
+	 */
+	if (IP_V(ip) == 4) {
+		MD5_Update(&ctx, (char *)&ip->ip_src, sizeof(ip->ip_src));
+		MD5_Update(&ctx, (char *)&ip->ip_dst, sizeof(ip->ip_dst));
+		MD5_Update(&ctx, (char *)&zero_proto, sizeof(zero_proto));
+		MD5_Update(&ctx, (char *)&ip->ip_p, sizeof(ip->ip_p));
+		tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4;
+		tlen = htons(tlen);
+		MD5_Update(&ctx, (char *)&tlen, sizeof(tlen));
+#ifdef INET6
+	} else if (IP_V(ip) == 6) {
+		ip6 = (struct ip6_hdr *)ip;
+		MD5_Update(&ctx, (char *)&ip6->ip6_src, sizeof(ip6->ip6_src));
+		MD5_Update(&ctx, (char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst));
+		len32 = htonl(ntohs(ip6->ip6_plen));
+		MD5_Update(&ctx, (char *)&len32, sizeof(len32));
+		nxt = 0;
+		MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
+		MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
+		MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
+		nxt = IPPROTO_TCP;
+		MD5_Update(&ctx, (char *)&nxt, sizeof(nxt));
+#endif
+	} else
+		return (CANT_CHECK_SIGNATURE);
+
+	/*
+	 * Step 2: Update MD5 hash with TCP header, excluding options.
+	 * The TCP checksum must be set to zero.
+	 */
+	savecsum = tp1.th_sum;
+	tp1.th_sum = 0;
+	MD5_Update(&ctx, (char *)&tp1, sizeof(struct tcphdr));
+	tp1.th_sum = savecsum;
+	/*
+	 * Step 3: Update MD5 hash with TCP segment data, if present.
+	 */
+	if (length > 0)
+		MD5_Update(&ctx, data, length);
+	/*
+	 * Step 4: Update MD5 hash with shared secret.
+	 */
+	MD5_Update(&ctx, tcpmd5secret, strlen(tcpmd5secret));
+	MD5_Final(sig, &ctx);
+
+	if (memcmp(rcvsig, sig, TCP_SIGLEN) == 0)
+		return (SIGNATURE_VALID);
+	else
+		return (SIGNATURE_INVALID);
+}
+#endif /* HAVE_LIBCRYPTO */