print-tcp.c

/*	$NetBSD: print-tcp.c,v 1.9 2007/07/26 18:15:12 plunky Exp $	*/

/*
 * 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.
 */

/* \summary: TCP printer */

#ifndef lint
#else
__RCSID("$NetBSD: print-tcp.c,v 1.8 2007/07/24 11:53:48 drochner Exp $");
#endif

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "netdissect-stdinc.h"

#include <stdlib.h>
#include <string.h>

#include "netdissect.h"
#include "addrtoname.h"
#include "extract.h"

#include "tcp.h"

#include "ip.h"
#include "ip6.h"
#include "ipproto.h"
#include "rpc_auth.h"
#include "rpc_msg.h"

#ifdef HAVE_LIBCRYPTO
#include <openssl/md5.h>
#include "signature.h"

static int tcp_verify_signature(netdissect_options *ndo,
                                const struct ip *ip, const struct tcphdr *tp,
                                const u_char *data, u_int length, const u_char *rcvsig);
#endif

static void print_tcp_rst_data(netdissect_options *, const u_char *sp, u_int length);
static void print_tcp_fastopen_option(netdissect_options *ndo, const u_char *cp,
                                      u_int datalen, int exp);

#define MAX_RST_DATA_LEN	30


struct tha {
        nd_ipv4 src;
        nd_ipv4 dst;
        u_int port;
};

struct tcp_seq_hash {
        struct tcp_seq_hash *nxt;
        struct tha addr;
        uint32_t seq;
        uint32_t ack;
};

struct tha6 {
        nd_ipv6 src;
        nd_ipv6 dst;
        u_int port;
};

struct tcp_seq_hash6 {
        struct tcp_seq_hash6 *nxt;
        struct tha6 addr;
        uint32_t seq;
        uint32_t ack;
};

#define TSEQ_HASHSIZE 919

/* These tcp options do not have the size octet */
#define ZEROLENOPT(o) ((o) == TCPOPT_EOL || (o) == TCPOPT_NOP)

static struct tcp_seq_hash tcp_seq_hash4[TSEQ_HASHSIZE];
static struct tcp_seq_hash6 tcp_seq_hash6[TSEQ_HASHSIZE];

static const struct tok tcp_flag_values[] = {
        { TH_FIN, "F" },
        { TH_SYN, "S" },
        { TH_RST, "R" },
        { TH_PUSH, "P" },
        { TH_ACK, "." },
        { TH_URG, "U" },
        { TH_ECNECHO, "E" },
        { TH_CWR, "W" },
        { 0, NULL }
};

static const struct tok tcp_option_values[] = {
        { TCPOPT_EOL, "eol" },
        { TCPOPT_NOP, "nop" },
        { TCPOPT_MAXSEG, "mss" },
        { TCPOPT_WSCALE, "wscale" },
        { TCPOPT_SACKOK, "sackOK" },
        { TCPOPT_SACK, "sack" },
        { TCPOPT_ECHO, "echo" },
        { TCPOPT_ECHOREPLY, "echoreply" },
        { TCPOPT_TIMESTAMP, "TS" },
        { TCPOPT_CC, "cc" },
        { TCPOPT_CCNEW, "ccnew" },
        { TCPOPT_CCECHO, "" },
        { TCPOPT_SIGNATURE, "md5" },
        { TCPOPT_SCPS, "scps" },
        { TCPOPT_UTO, "uto" },
        { TCPOPT_TCPAO, "tcp-ao" },
        { TCPOPT_MPTCP, "mptcp" },
        { TCPOPT_FASTOPEN, "tfo" },
        { TCPOPT_EXPERIMENT2, "exp" },
        { 0, NULL }
};

static uint16_t
tcp_cksum(netdissect_options *ndo,
          const struct ip *ip,
          const struct tcphdr *tp,
          u_int len)
{
        return nextproto4_cksum(ndo, ip, (const uint8_t *)tp, len, len,
                                IPPROTO_TCP);
}

static uint16_t
tcp6_cksum(netdissect_options *ndo,
           const struct ip6_hdr *ip6,
           const struct tcphdr *tp,
           u_int len)
{
        return nextproto6_cksum(ndo, ip6, (const uint8_t *)tp, len, len,
                                IPPROTO_TCP);
}

void
tcp_print(netdissect_options *ndo,
          const u_char *bp, u_int length,
          const u_char *bp2, int fragmented)
{
        const struct tcphdr *tp;
        const struct ip *ip;
        u_char flags;
        u_int hlen;
        char ch;
        uint16_t sport, dport, win, urp;
        uint32_t seq, ack, thseq, thack;
        u_int utoval;
        uint16_t magic;
        int rev;
        const struct ip6_hdr *ip6;
        u_int header_len;	/* Header length in bytes */

        ndo->ndo_protocol = "tcp";
        tp = (const struct tcphdr *)bp;
        ip = (const struct ip *)bp2;
        if (IP_V(ip) == 6)
                ip6 = (const struct ip6_hdr *)bp2;
        else
                ip6 = NULL;
        ch = '\0';
        if (!ND_TTEST_2(tp->th_dport)) {
                if (ip6) {
                        ND_PRINT("%s > %s:",
                                 GET_IP6ADDR_STRING(ip6->ip6_src),
                                 GET_IP6ADDR_STRING(ip6->ip6_dst));
                } else {
                        ND_PRINT("%s > %s:",
                                 GET_IPADDR_STRING(ip->ip_src),
                                 GET_IPADDR_STRING(ip->ip_dst));
                }
                nd_print_trunc(ndo);
                return;
        }

        sport = GET_BE_U_2(tp->th_sport);
        dport = GET_BE_U_2(tp->th_dport);

        if (ip6) {
                if (GET_U_1(ip6->ip6_nxt) == IPPROTO_TCP) {
                        ND_PRINT("%s.%s > %s.%s: ",
                                 GET_IP6ADDR_STRING(ip6->ip6_src),
                                 tcpport_string(ndo, sport),
                                 GET_IP6ADDR_STRING(ip6->ip6_dst),
                                 tcpport_string(ndo, dport));
                } else {
                        ND_PRINT("%s > %s: ",
                                 tcpport_string(ndo, sport), tcpport_string(ndo, dport));
                }
        } else {
                if (GET_U_1(ip->ip_p) == IPPROTO_TCP) {
                        ND_PRINT("%s.%s > %s.%s: ",
                                 GET_IPADDR_STRING(ip->ip_src),
                                 tcpport_string(ndo, sport),
                                 GET_IPADDR_STRING(ip->ip_dst),
                                 tcpport_string(ndo, dport));
                } else {
                        ND_PRINT("%s > %s: ",
                                 tcpport_string(ndo, sport), tcpport_string(ndo, dport));
                }
        }

        ND_TCHECK_SIZE(tp);

        hlen = TH_OFF(tp) * 4;

        if (hlen < sizeof(*tp)) {
                ND_PRINT(" tcp %u [bad hdr length %u - too short, < %zu]",
                         length - hlen, hlen, sizeof(*tp));
                return;
        }

        seq = GET_BE_U_4(tp->th_seq);
        ack = GET_BE_U_4(tp->th_ack);
        win = GET_BE_U_2(tp->th_win);
        urp = GET_BE_U_2(tp->th_urp);

        if (ndo->ndo_qflag) {
                ND_PRINT("tcp %u", length - hlen);
                if (hlen > length) {
                        ND_PRINT(" [bad hdr length %u - too long, > %u]",
                                 hlen, length);
                }
                return;
        }

        flags = GET_U_1(tp->th_flags);
        ND_PRINT("Flags [%s]", bittok2str_nosep(tcp_flag_values, "none", flags));

        if (!ndo->ndo_Sflag && (flags & TH_ACK)) {
                /*
                 * 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).
                 */
                rev = 0;
                if (ip6) {
                        struct tcp_seq_hash6 *th;
                        struct tcp_seq_hash6 *tcp_seq_hash;
                        const void *src, *dst;
                        struct tha6 tha;

                        tcp_seq_hash = tcp_seq_hash6;
                        src = (const void *)ip6->ip6_src;
                        dst = (const void *)ip6->ip6_dst;
                        if (sport > dport)
                                rev = 1;
                        else if (sport == dport) {
                                if (UNALIGNED_MEMCMP(src, dst, sizeof(ip6->ip6_dst)) > 0)
                                        rev = 1;
                        }
                        if (rev) {
                                UNALIGNED_MEMCPY(&tha.src, dst, sizeof(ip6->ip6_dst));
                                UNALIGNED_MEMCPY(&tha.dst, src, sizeof(ip6->ip6_src));
                                tha.port = ((u_int)dport) << 16 | sport;
                        } else {
                                UNALIGNED_MEMCPY(&tha.dst, dst, sizeof(ip6->ip6_dst));
                                UNALIGNED_MEMCPY(&tha.src, src, sizeof(ip6->ip6_src));
                                tha.port = ((u_int)sport) << 16 | dport;
                        }

                        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 */
                                /* calloc() return used by the 'tcp_seq_hash6'
                                   hash table: do not free() */
                                if (th->nxt == NULL) {
                                        th->nxt = (struct tcp_seq_hash6 *)
                                                calloc(1, sizeof(*th));
                                        if (th->nxt == NULL)
                                                (*ndo->ndo_error)(ndo,
                                                        S_ERR_ND_MEM_ALLOC,
                                                        "%s: calloc", __func__);
                                }
                                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 {
                        struct tcp_seq_hash *th;
                        struct tcp_seq_hash *tcp_seq_hash;
                        struct tha tha;

                        tcp_seq_hash = tcp_seq_hash4;
                        if (sport > dport)
                                rev = 1;
                        else if (sport == dport) {
                                if (UNALIGNED_MEMCMP(ip->ip_src, ip->ip_dst, sizeof(ip->ip_dst)) > 0)
                                        rev = 1;
                        }
                        if (rev) {
                                UNALIGNED_MEMCPY(&tha.src, ip->ip_dst,
                                                 sizeof(ip->ip_dst));
                                UNALIGNED_MEMCPY(&tha.dst, ip->ip_src,
                                                 sizeof(ip->ip_src));
                                tha.port = ((u_int)dport) << 16 | sport;
                        } else {
                                UNALIGNED_MEMCPY(&tha.dst, ip->ip_dst,
                                                 sizeof(ip->ip_dst));
                                UNALIGNED_MEMCPY(&tha.src, ip->ip_src,
                                                 sizeof(ip->ip_src));
                                tha.port = ((u_int)sport) << 16 | dport;
                        }

                        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 */
                                /* calloc() return used by the 'tcp_seq_hash4'
                                   hash table: do not free() */
                                if (th->nxt == NULL) {
                                        th->nxt = (struct tcp_seq_hash *)
                                                calloc(1, sizeof(*th));
                                        if (th->nxt == NULL)
                                                (*ndo->ndo_error)(ndo,
                                                        S_ERR_ND_MEM_ALLOC,
                                                        "%s: calloc", __func__);
                                }
                                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 = rev = 0;
        }
        if (hlen > length) {
                ND_PRINT(" [bad hdr length %u - too long, > %u]",
                         hlen, length);
                return;
        }

        if (ndo->ndo_vflag && !ndo->ndo_Kflag && !fragmented) {
                /* Check the checksum, if possible. */
                uint16_t sum, tcp_sum;

                if (IP_V(ip) == 4) {
                        if (ND_TTEST_LEN(tp->th_sport, length)) {
                                sum = tcp_cksum(ndo, ip, tp, length);
                                tcp_sum = GET_BE_U_2(tp->th_sum);

                                ND_PRINT(", cksum 0x%04x", tcp_sum);
                                if (sum != 0)
                                        ND_PRINT(" (incorrect -> 0x%04x)",
                                            in_cksum_shouldbe(tcp_sum, sum));
                                else
                                        ND_PRINT(" (correct)");
                        }
                } else if (IP_V(ip) == 6) {
                        if (ND_TTEST_LEN(tp->th_sport, length)) {
                                sum = tcp6_cksum(ndo, ip6, tp, length);
                                tcp_sum = GET_BE_U_2(tp->th_sum);

                                ND_PRINT(", cksum 0x%04x", tcp_sum);
                                if (sum != 0)
                                        ND_PRINT(" (incorrect -> 0x%04x)",
                                            in_cksum_shouldbe(tcp_sum, sum));
                                else
                                        ND_PRINT(" (correct)");

                        }
                }
        }

        length -= hlen;
        if (ndo->ndo_vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST)) {
                ND_PRINT(", seq %u", seq);

                if (length > 0) {
                        ND_PRINT(":%u", seq + length);
                }
        }

        if (flags & TH_ACK) {
                ND_PRINT(", ack %u", ack);
        }

        ND_PRINT(", win %u", win);

        if (flags & TH_URG)
                ND_PRINT(", urg %u", urp);
        /*
         * Handle any options.
         */
        if (hlen > sizeof(*tp)) {
                const u_char *cp;
                u_int i, opt, datalen;
                u_int len;

                hlen -= sizeof(*tp);
                cp = (const u_char *)tp + sizeof(*tp);
                ND_PRINT(", options [");
                while (hlen > 0) {
                        if (ch != '\0')
                                ND_PRINT("%c", ch);
                        opt = GET_U_1(cp);
                        cp++;
                        if (ZEROLENOPT(opt))
                                len = 1;
                        else {
                                len = GET_U_1(cp);
                                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; ND_TCHECK_LEN(cp, l); }


                        ND_PRINT("%s", tok2str(tcp_option_values, "unknown-%u", opt));

                        switch (opt) {

                        case TCPOPT_MAXSEG:
                                datalen = 2;
                                LENCHECK(datalen);
                                ND_PRINT(" %u", GET_BE_U_2(cp));
                                break;

                        case TCPOPT_WSCALE:
                                datalen = 1;
                                LENCHECK(datalen);
                                ND_PRINT(" %u", GET_U_1(cp));
                                break;

                        case TCPOPT_SACK:
                                datalen = len - 2;
                                if (datalen % 8 != 0) {
                                        ND_PRINT(" invalid sack");
                                } else {
                                        uint32_t s, e;

                                        ND_PRINT(" %u ", datalen / 8);
                                        for (i = 0; i < datalen; i += 8) {
                                                LENCHECK(i + 4);
                                                s = GET_BE_U_4(cp + i);
                                                LENCHECK(i + 8);
                                                e = GET_BE_U_4(cp + i + 4);
                                                if (rev) {
                                                        s -= thseq;
                                                        e -= thseq;
                                                } else {
                                                        s -= thack;
                                                        e -= thack;
                                                }
                                                ND_PRINT("{%u:%u}", s, e);
                                        }
                                }
                                break;

                        case TCPOPT_CC:
                        case TCPOPT_CCNEW:
                        case TCPOPT_CCECHO:
                        case TCPOPT_ECHO:
                        case TCPOPT_ECHOREPLY:

                                /*
                                 * those options share their semantics.
                                 * fall through
                                 */
                                datalen = 4;
                                LENCHECK(datalen);
                                ND_PRINT(" %u", GET_BE_U_4(cp));
                                break;

                        case TCPOPT_TIMESTAMP:
                                datalen = 8;
                                LENCHECK(datalen);
                                ND_PRINT(" val %u ecr %u",
                                             GET_BE_U_4(cp),
                                             GET_BE_U_4(cp + 4));
                                break;

                        case TCPOPT_SIGNATURE:
                                datalen = TCP_SIGLEN;
                                LENCHECK(datalen);
                                ND_PRINT(" ");
#ifdef HAVE_LIBCRYPTO
                                switch (tcp_verify_signature(ndo, ip, tp,
                                                             bp + TH_OFF(tp) * 4, length, cp)) {

                                case SIGNATURE_VALID:
                                        ND_PRINT("valid");
                                        break;

                                case SIGNATURE_INVALID:
                                        nd_print_invalid(ndo);
                                        break;

                                case CANT_CHECK_SIGNATURE:
                                        ND_PRINT("can't check - ");
                                        for (i = 0; i < TCP_SIGLEN; ++i)
                                                ND_PRINT("%02x",
                                                         GET_U_1(cp + i));
                                        break;
                                }
#else
                                for (i = 0; i < TCP_SIGLEN; ++i)
                                        ND_PRINT("%02x", GET_U_1(cp + i));
#endif
                                break;

                        case TCPOPT_SCPS:
                                datalen = 2;
                                LENCHECK(datalen);
                                ND_PRINT(" cap %02x id %u", GET_U_1(cp),
                                         GET_U_1(cp + 1));
                                break;

                        case TCPOPT_TCPAO:
                                datalen = len - 2;
                                /* RFC 5925 Section 2.2:
                                 * "The Length value MUST be greater than or equal to 4."
                                 * (This includes the Kind and Length fields already processed
                                 * at this point.)
                                 */
                                if (datalen < 2) {
                                        nd_print_invalid(ndo);
                                } else {
                                        LENCHECK(1);
                                        ND_PRINT(" keyid %u", GET_U_1(cp));
                                        LENCHECK(2);
                                        ND_PRINT(" rnextkeyid %u",
                                                 GET_U_1(cp + 1));
                                        if (datalen > 2) {
                                                ND_PRINT(" mac 0x");
                                                for (i = 2; i < datalen; i++) {
                                                        LENCHECK(i + 1);
                                                        ND_PRINT("%02x",
                                                                 GET_U_1(cp + i));
                                                }
                                        }
                                }
                                break;

                        case TCPOPT_EOL:
                        case TCPOPT_NOP:
                        case TCPOPT_SACKOK:
                                /*
                                 * Nothing interesting.
                                 * fall through
                                 */
                                break;

                        case TCPOPT_UTO:
                                datalen = 2;
                                LENCHECK(datalen);
                                utoval = GET_BE_U_2(cp);
                                ND_PRINT(" 0x%x", utoval);
                                if (utoval & 0x0001)
                                        utoval = (utoval >> 1) * 60;
                                else
                                        utoval >>= 1;
                                ND_PRINT(" %u", utoval);
                                break;

                        case TCPOPT_MPTCP:
                            {
                                const u_char *snapend_save;
                                int ret;

                                datalen = len - 2;
                                LENCHECK(datalen);
                                /* Update the snapend to the end of the option
                                 * before calling mptcp_print(). Some options
                                 * (MPTCP or others) may be present after a
                                 * MPTCP option. This prevents that, in
                                 * mptcp_print(), the remaining length < the
                                 * remaining caplen.
                                 */
                                snapend_save = ndo->ndo_snapend;
                                ndo->ndo_snapend = ND_MIN(cp - 2 + len,
                                                          ndo->ndo_snapend);
                                ret = mptcp_print(ndo, cp - 2, len, flags);
                                ndo->ndo_snapend = snapend_save;
                                if (!ret)
                                        goto bad;
                                break;
                            }

                        case TCPOPT_FASTOPEN:
                                datalen = len - 2;
                                LENCHECK(datalen);
                                ND_PRINT(" ");
                                print_tcp_fastopen_option(ndo, cp, datalen, FALSE);
                                break;

                        case TCPOPT_EXPERIMENT2:
                                datalen = len - 2;
                                LENCHECK(datalen);
                                if (datalen < 2)
                                        goto bad;
                                /* RFC6994 */
                                magic = GET_BE_U_2(cp);
                                ND_PRINT("-");

                                switch(magic) {

                                case 0xf989: /* TCP Fast Open RFC 7413 */
                                        print_tcp_fastopen_option(ndo, cp + 2, datalen - 2, TRUE);
                                        break;

                                default:
                                        /* Unknown magic number */
                                        ND_PRINT("%04x", magic);
                                        break;
                                }
                                break;

                        default:
                                datalen = len - 2;
                                if (datalen)
                                        ND_PRINT(" 0x");
                                for (i = 0; i < datalen; ++i) {
                                        LENCHECK(i + 1);
                                        ND_PRINT("%02x", GET_U_1(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)
                                ND_PRINT("[len %u]", len);
                        ch = ',';
                        if (opt == TCPOPT_EOL)
                                break;
                }
                ND_PRINT("]");
        }

        /*
         * Print length field before crawling down the stack.
         */
        ND_PRINT(", length %u", length);

        if (length <= 0)
                return;

        /*
         * Decode payload if necessary.
         */
        header_len = TH_OFF(tp) * 4;
        /*
         * Do a bounds check before decoding the payload.
         * At least the header data is required.
         */
        if (!ND_TTEST_LEN(bp, header_len)) {
                ND_PRINT(" [remaining caplen(%u) < header length(%u)]",
                         ND_BYTES_AVAILABLE_AFTER(bp), header_len);
                nd_trunc_longjmp(ndo);
        }
        bp += header_len;
        if ((flags & TH_RST) && ndo->ndo_vflag) {
                print_tcp_rst_data(ndo, bp, length);
                return;
        }

        if (ndo->ndo_packettype) {
                switch (ndo->ndo_packettype) {
                case PT_ZMTP1:
                        zmtp1_print(ndo, bp, length);
                        break;
                case PT_RESP:
                        resp_print(ndo, bp, length);
                        break;
                case PT_DOMAIN:
                        /* over_tcp: TRUE, is_mdns: FALSE */
                        domain_print(ndo, bp, length, TRUE, FALSE);
                        break;
                }
                return;
        }

        if (IS_SRC_OR_DST_PORT(TELNET_PORT)) {
                telnet_print(ndo, bp, length);
        } else if (IS_SRC_OR_DST_PORT(SMTP_PORT)) {
                ND_PRINT(": ");
                smtp_print(ndo, bp, length);
        } else if (IS_SRC_OR_DST_PORT(WHOIS_PORT)) {
                ND_PRINT(": ");
                ndo->ndo_protocol = "whois";	/* needed by txtproto_print() */
                txtproto_print(ndo, bp, length, NULL, 0); /* RFC 3912 */
        } else if (IS_SRC_OR_DST_PORT(BGP_PORT))
                bgp_print(ndo, bp, length);
        else if (IS_SRC_OR_DST_PORT(PPTP_PORT))
                pptp_print(ndo, bp);
        else if (IS_SRC_OR_DST_PORT(REDIS_PORT))
                resp_print(ndo, bp, length);
        else if (IS_SRC_OR_DST_PORT(SSH_PORT))
                ssh_print(ndo, bp, length);
#ifdef ENABLE_SMB
        else if (IS_SRC_OR_DST_PORT(NETBIOS_SSN_PORT))
                nbt_tcp_print(ndo, bp, length);
        else if (IS_SRC_OR_DST_PORT(SMB_PORT))
                smb_tcp_print(ndo, bp, length);
#endif
        else if (IS_SRC_OR_DST_PORT(BEEP_PORT))
                beep_print(ndo, bp, length);
        else if (IS_SRC_OR_DST_PORT(OPENFLOW_PORT_OLD) || IS_SRC_OR_DST_PORT(OPENFLOW_PORT_IANA))
                openflow_print(ndo, bp, length);
        else if (IS_SRC_OR_DST_PORT(FTP_PORT)) {
                ND_PRINT(": ");
                ftp_print(ndo, bp, length);
        } else if (IS_SRC_OR_DST_PORT(HTTP_PORT) || IS_SRC_OR_DST_PORT(HTTP_PORT_ALT)) {
                ND_PRINT(": ");
                http_print(ndo, bp, length);
        } else if (IS_SRC_OR_DST_PORT(RTSP_PORT) || IS_SRC_OR_DST_PORT(RTSP_PORT_ALT)) {
                ND_PRINT(": ");
                rtsp_print(ndo, bp, length);
        } else if (IS_SRC_OR_DST_PORT(NAMESERVER_PORT)) {
                /* over_tcp: TRUE, is_mdns: FALSE */
                domain_print(ndo, bp, length, TRUE, FALSE);
        } else if (IS_SRC_OR_DST_PORT(MSDP_PORT)) {
                msdp_print(ndo, bp, length);
        } else if (IS_SRC_OR_DST_PORT(RPKI_RTR_PORT)) {
                rpki_rtr_print(ndo, bp, length);
        } else if (IS_SRC_OR_DST_PORT(LDP_PORT)) {
                ldp_print(ndo, bp, length);
        } else if ((IS_SRC_OR_DST_PORT(NFS_PORT)) &&
                 length >= 4 && ND_TTEST_4(bp)) {
                /*
                 * 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.
                 */
                uint32_t fraglen;
                const struct sunrpc_msg *rp;
                enum sunrpc_msg_type direction;

                fraglen = GET_BE_U_4(bp) & 0x7FFFFFFF;
                if (fraglen > (length) - 4)
                        fraglen = (length) - 4;
                rp = (const struct sunrpc_msg *)(bp + 4);
                if (ND_TTEST_4(rp->rm_direction)) {
                        direction = (enum sunrpc_msg_type) GET_BE_U_4(rp->rm_direction);
                        if (dport == NFS_PORT && direction == SUNRPC_CALL) {
                                ND_PRINT(": NFS request xid %u ",
                                         GET_BE_U_4(rp->rm_xid));
                                nfsreq_noaddr_print(ndo, (const u_char *)rp, fraglen, (const u_char *)ip);
                                return;
                        }
                        if (sport == NFS_PORT && direction == SUNRPC_REPLY) {
                                ND_PRINT(": NFS reply xid %u ",
                                         GET_BE_U_4(rp->rm_xid));
                                nfsreply_noaddr_print(ndo, (const u_char *)rp, fraglen, (const u_char *)ip);
                                return;
                        }
                }
        }

        return;
bad:
        ND_PRINT("[bad opt]");
        if (ch != '\0')
                ND_PRINT("]");
        return;
trunc:
        nd_print_trunc(ndo);
        if (ch != '\0')
                ND_PRINT(">");
}

/*
 * 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(netdissect_options *ndo,
                   const u_char *sp, u_int length)
{
        u_char c;

        ND_PRINT(ND_TTEST_LEN(sp, length) ? " [RST" : " [!RST");
        if (length > MAX_RST_DATA_LEN) {
                length = MAX_RST_DATA_LEN;	/* can use -X for longer */
                ND_PRINT("+");			/* indicate we truncate */
        }
        ND_PRINT(" ");
        while (length && sp < ndo->ndo_snapend) {
                c = GET_U_1(sp);
                sp++;
                fn_print_char(ndo, c);
                length--;
        }
        ND_PRINT("]");
}

static void
print_tcp_fastopen_option(netdissect_options *ndo, const u_char *cp,
                          u_int datalen, int exp)
{
        u_int i;

        if (exp)
                ND_PRINT("tfo");

        if (datalen == 0) {
                /* Fast Open Cookie Request */
                ND_PRINT(" cookiereq");
        } else {
                /* Fast Open Cookie */
                if (datalen % 2 != 0 || datalen < 4 || datalen > 16) {
                        nd_print_invalid(ndo);
                } else {
                        ND_PRINT(" cookie ");
                        for (i = 0; i < datalen; ++i)
                                ND_PRINT("%02x", GET_U_1(cp + i));
                }
        }
}

#ifdef HAVE_LIBCRYPTO
USES_APPLE_DEPRECATED_API
static int
tcp_verify_signature(netdissect_options *ndo,
                     const struct ip *ip, const struct tcphdr *tp,
                     const u_char *data, u_int length, const u_char *rcvsig)
{
        struct tcphdr tp1;
        u_char sig[TCP_SIGLEN];
        char zero_proto = 0;
        MD5_CTX ctx;
        uint16_t savecsum, tlen;
        const struct ip6_hdr *ip6;
        uint32_t len32;
        uint8_t nxt;

        if (data + length > ndo->ndo_snapend) {
                ND_PRINT("snaplen too short, ");
                return (CANT_CHECK_SIGNATURE);
        }

        tp1 = *tp;

        if (ndo->ndo_sigsecret == NULL) {
                ND_PRINT("shared secret not supplied with -M, ");
                return (CANT_CHECK_SIGNATURE);
        }

        MD5_Init(&ctx);
        /*
         * Step 1: Update MD5 hash with IP pseudo-header.
         */
        if (IP_V(ip) == 4) {
                MD5_Update(&ctx, (const char *)&ip->ip_src, sizeof(ip->ip_src));
                MD5_Update(&ctx, (const char *)&ip->ip_dst, sizeof(ip->ip_dst));
                MD5_Update(&ctx, (const char *)&zero_proto, sizeof(zero_proto));
                MD5_Update(&ctx, (const char *)&ip->ip_p, sizeof(ip->ip_p));
                tlen = GET_BE_U_2(ip->ip_len) - IP_HL(ip) * 4;
                tlen = htons(tlen);
                MD5_Update(&ctx, (const char *)&tlen, sizeof(tlen));
        } else if (IP_V(ip) == 6) {
                ip6 = (const struct ip6_hdr *)ip;
                MD5_Update(&ctx, (const char *)&ip6->ip6_src, sizeof(ip6->ip6_src));
                MD5_Update(&ctx, (const char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst));
                len32 = htonl(GET_BE_U_2(ip6->ip6_plen));
                MD5_Update(&ctx, (const char *)&len32, sizeof(len32));
                nxt = 0;
                MD5_Update(&ctx, (const char *)&nxt, sizeof(nxt));
                MD5_Update(&ctx, (const char *)&nxt, sizeof(nxt));
                MD5_Update(&ctx, (const char *)&nxt, sizeof(nxt));
                nxt = IPPROTO_TCP;
                MD5_Update(&ctx, (const char *)&nxt, sizeof(nxt));
        } else {
                ND_PRINT("IP version not 4 or 6, ");
                return (CANT_CHECK_SIGNATURE);
        }

        /*
         * Step 2: Update MD5 hash with TCP header, excluding options.
         * The TCP checksum must be set to zero.
         */
        memcpy(&savecsum, tp1.th_sum, sizeof(savecsum));
        memset(tp1.th_sum, 0, sizeof(tp1.th_sum));
        MD5_Update(&ctx, (const char *)&tp1, sizeof(struct tcphdr));
        memcpy(tp1.th_sum, &savecsum, sizeof(tp1.th_sum));
        /*
         * 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, ndo->ndo_sigsecret, strlen(ndo->ndo_sigsecret));
        MD5_Final(sig, &ctx);

        if (memcmp(rcvsig, sig, TCP_SIGLEN) == 0)
                return (SIGNATURE_VALID);
        else
                return (SIGNATURE_INVALID);
}
USES_APPLE_RST
#endif /* HAVE_LIBCRYPTO */