1 /* $NetBSD: print-tcp.c,v 1.9 2007/07/26 18:15:12 plunky Exp $ */
4 * Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
5 * The Regents of the University of California. All rights reserved.
7 * Copyright (c) 1999-2004 The tcpdump.org project
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that: (1) source code distributions
11 * retain the above copyright notice and this paragraph in its entirety, (2)
12 * distributions including binary code include the above copyright notice and
13 * this paragraph in its entirety in the documentation or other materials
14 * provided with the distribution, and (3) all advertising materials mentioning
15 * features or use of this software display the following acknowledgement:
16 * ``This product includes software developed by the University of California,
17 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
18 * the University nor the names of its contributors may be used to endorse
19 * or promote products derived from this software without specific prior
21 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
22 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
23 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
26 /* \summary: TCP printer */
30 __RCSID("$NetBSD: print-tcp.c,v 1.8 2007/07/24 11:53:48 drochner Exp $");
37 #include "netdissect-stdinc.h"
42 #include "netdissect.h"
43 #include "addrtoname.h"
46 #include "diag-control.h"
57 #include <openssl/md5.h>
58 #include "signature.h"
60 static int tcp_verify_signature(netdissect_options *ndo,
61 const struct ip *ip, const struct tcphdr *tp,
62 const u_char *data, u_int length, const u_char *rcvsig);
65 static void print_tcp_rst_data(netdissect_options *, const u_char *sp, u_int length);
66 static void print_tcp_fastopen_option(netdissect_options *ndo, const u_char *cp,
67 u_int datalen, int exp);
69 #define MAX_RST_DATA_LEN 30
79 struct tcp_seq_hash *nxt;
91 struct tcp_seq_hash6 {
92 struct tcp_seq_hash6 *nxt;
98 #define TSEQ_HASHSIZE 919
100 /* These tcp options do not have the size octet */
101 #define ZEROLENOPT(o) ((o) == TCPOPT_EOL || (o) == TCPOPT_NOP)
103 static struct tcp_seq_hash tcp_seq_hash4[TSEQ_HASHSIZE];
104 static struct tcp_seq_hash6 tcp_seq_hash6[TSEQ_HASHSIZE];
106 static const struct tok tcp_flag_values[] = {
118 static const struct tok tcp_option_values[] = {
119 { TCPOPT_EOL, "eol" },
120 { TCPOPT_NOP, "nop" },
121 { TCPOPT_MAXSEG, "mss" },
122 { TCPOPT_WSCALE, "wscale" },
123 { TCPOPT_SACKOK, "sackOK" },
124 { TCPOPT_SACK, "sack" },
125 { TCPOPT_ECHO, "echo" },
126 { TCPOPT_ECHOREPLY, "echoreply" },
127 { TCPOPT_TIMESTAMP, "TS" },
129 { TCPOPT_CCNEW, "ccnew" },
130 { TCPOPT_CCECHO, "" },
131 { TCPOPT_SIGNATURE, "md5" },
132 { TCPOPT_SCPS, "scps" },
133 { TCPOPT_UTO, "uto" },
134 { TCPOPT_TCPAO, "tcp-ao" },
135 { TCPOPT_MPTCP, "mptcp" },
136 { TCPOPT_FASTOPEN, "tfo" },
137 { TCPOPT_EXPERIMENT2, "exp" },
142 tcp_cksum(netdissect_options *ndo,
144 const struct tcphdr *tp,
147 return nextproto4_cksum(ndo, ip, (const uint8_t *)tp, len, len,
152 tcp6_cksum(netdissect_options *ndo,
153 const struct ip6_hdr *ip6,
154 const struct tcphdr *tp,
157 return nextproto6_cksum(ndo, ip6, (const uint8_t *)tp, len, len,
162 tcp_print(netdissect_options *ndo,
163 const u_char *bp, u_int length,
164 const u_char *bp2, int fragmented)
166 const struct tcphdr *tp;
171 uint16_t sport, dport, win, urp;
172 uint32_t seq, ack, thseq, thack;
176 const struct ip6_hdr *ip6;
177 u_int header_len; /* Header length in bytes */
179 ndo->ndo_protocol = "tcp";
180 tp = (const struct tcphdr *)bp;
181 ip = (const struct ip *)bp2;
183 ip6 = (const struct ip6_hdr *)bp2;
187 if (!ND_TTEST_2(tp->th_dport)) {
190 GET_IP6ADDR_STRING(ip6->ip6_src),
191 GET_IP6ADDR_STRING(ip6->ip6_dst));
194 GET_IPADDR_STRING(ip->ip_src),
195 GET_IPADDR_STRING(ip->ip_dst));
201 sport = GET_BE_U_2(tp->th_sport);
202 dport = GET_BE_U_2(tp->th_dport);
205 if (GET_U_1(ip6->ip6_nxt) == IPPROTO_TCP) {
206 ND_PRINT("%s.%s > %s.%s: ",
207 GET_IP6ADDR_STRING(ip6->ip6_src),
208 tcpport_string(ndo, sport),
209 GET_IP6ADDR_STRING(ip6->ip6_dst),
210 tcpport_string(ndo, dport));
212 ND_PRINT("%s > %s: ",
213 tcpport_string(ndo, sport), tcpport_string(ndo, dport));
216 if (GET_U_1(ip->ip_p) == IPPROTO_TCP) {
217 ND_PRINT("%s.%s > %s.%s: ",
218 GET_IPADDR_STRING(ip->ip_src),
219 tcpport_string(ndo, sport),
220 GET_IPADDR_STRING(ip->ip_dst),
221 tcpport_string(ndo, dport));
223 ND_PRINT("%s > %s: ",
224 tcpport_string(ndo, sport), tcpport_string(ndo, dport));
230 hlen = TH_OFF(tp) * 4;
232 if (hlen < sizeof(*tp)) {
233 ND_PRINT(" tcp %u [bad hdr length %u - too short, < %zu]",
234 length - hlen, hlen, sizeof(*tp));
238 seq = GET_BE_U_4(tp->th_seq);
239 ack = GET_BE_U_4(tp->th_ack);
240 win = GET_BE_U_2(tp->th_win);
241 urp = GET_BE_U_2(tp->th_urp);
243 if (ndo->ndo_qflag) {
244 ND_PRINT("tcp %u", length - hlen);
246 ND_PRINT(" [bad hdr length %u - too long, > %u]",
252 flags = GET_U_1(tp->th_flags);
253 ND_PRINT("Flags [%s]", bittok2str_nosep(tcp_flag_values, "none", flags));
255 if (!ndo->ndo_Sflag && (flags & TH_ACK)) {
257 * Find (or record) the initial sequence numbers for
258 * this conversation. (we pick an arbitrary
259 * collating order so there's only one entry for
264 struct tcp_seq_hash6 *th;
265 struct tcp_seq_hash6 *tcp_seq_hash;
266 const void *src, *dst;
269 tcp_seq_hash = tcp_seq_hash6;
270 src = (const void *)ip6->ip6_src;
271 dst = (const void *)ip6->ip6_dst;
274 else if (sport == dport) {
275 if (UNALIGNED_MEMCMP(src, dst, sizeof(ip6->ip6_dst)) > 0)
279 UNALIGNED_MEMCPY(&tha.src, dst, sizeof(ip6->ip6_dst));
280 UNALIGNED_MEMCPY(&tha.dst, src, sizeof(ip6->ip6_src));
281 tha.port = ((u_int)dport) << 16 | sport;
283 UNALIGNED_MEMCPY(&tha.dst, dst, sizeof(ip6->ip6_dst));
284 UNALIGNED_MEMCPY(&tha.src, src, sizeof(ip6->ip6_src));
285 tha.port = ((u_int)sport) << 16 | dport;
288 for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];
289 th->nxt; th = th->nxt)
290 if (memcmp((char *)&tha, (char *)&th->addr,
291 sizeof(th->addr)) == 0)
294 if (!th->nxt || (flags & TH_SYN)) {
295 /* didn't find it or new conversation */
296 /* calloc() return used by the 'tcp_seq_hash6'
297 hash table: do not free() */
298 if (th->nxt == NULL) {
299 th->nxt = (struct tcp_seq_hash6 *)
300 calloc(1, sizeof(*th));
302 (*ndo->ndo_error)(ndo,
304 "%s: calloc", __func__);
308 th->ack = seq, th->seq = ack - 1;
310 th->seq = seq, th->ack = ack - 1;
313 seq -= th->ack, ack -= th->seq;
315 seq -= th->seq, ack -= th->ack;
321 struct tcp_seq_hash *th;
322 struct tcp_seq_hash *tcp_seq_hash;
325 tcp_seq_hash = tcp_seq_hash4;
328 else if (sport == dport) {
329 if (UNALIGNED_MEMCMP(ip->ip_src, ip->ip_dst, sizeof(ip->ip_dst)) > 0)
333 UNALIGNED_MEMCPY(&tha.src, ip->ip_dst,
335 UNALIGNED_MEMCPY(&tha.dst, ip->ip_src,
337 tha.port = ((u_int)dport) << 16 | sport;
339 UNALIGNED_MEMCPY(&tha.dst, ip->ip_dst,
341 UNALIGNED_MEMCPY(&tha.src, ip->ip_src,
343 tha.port = ((u_int)sport) << 16 | dport;
346 for (th = &tcp_seq_hash[tha.port % TSEQ_HASHSIZE];
347 th->nxt; th = th->nxt)
348 if (memcmp((char *)&tha, (char *)&th->addr,
349 sizeof(th->addr)) == 0)
352 if (!th->nxt || (flags & TH_SYN)) {
353 /* didn't find it or new conversation */
354 /* calloc() return used by the 'tcp_seq_hash4'
355 hash table: do not free() */
356 if (th->nxt == NULL) {
357 th->nxt = (struct tcp_seq_hash *)
358 calloc(1, sizeof(*th));
360 (*ndo->ndo_error)(ndo,
362 "%s: calloc", __func__);
366 th->ack = seq, th->seq = ack - 1;
368 th->seq = seq, th->ack = ack - 1;
371 seq -= th->ack, ack -= th->seq;
373 seq -= th->seq, ack -= th->ack;
381 thseq = thack = rev = 0;
384 ND_PRINT(" [bad hdr length %u - too long, > %u]",
389 if (ndo->ndo_vflag && !ndo->ndo_Kflag && !fragmented) {
390 /* Check the checksum, if possible. */
391 uint16_t sum, tcp_sum;
394 if (ND_TTEST_LEN(tp->th_sport, length)) {
395 sum = tcp_cksum(ndo, ip, tp, length);
396 tcp_sum = GET_BE_U_2(tp->th_sum);
398 ND_PRINT(", cksum 0x%04x", tcp_sum);
400 ND_PRINT(" (incorrect -> 0x%04x)",
401 in_cksum_shouldbe(tcp_sum, sum));
403 ND_PRINT(" (correct)");
405 } else if (IP_V(ip) == 6) {
406 if (ND_TTEST_LEN(tp->th_sport, length)) {
407 sum = tcp6_cksum(ndo, ip6, tp, length);
408 tcp_sum = GET_BE_U_2(tp->th_sum);
410 ND_PRINT(", cksum 0x%04x", tcp_sum);
412 ND_PRINT(" (incorrect -> 0x%04x)",
413 in_cksum_shouldbe(tcp_sum, sum));
415 ND_PRINT(" (correct)");
422 if (ndo->ndo_vflag > 1 || length > 0 || flags & (TH_SYN | TH_FIN | TH_RST)) {
423 ND_PRINT(", seq %u", seq);
426 ND_PRINT(":%u", seq + length);
430 if (flags & TH_ACK) {
431 ND_PRINT(", ack %u", ack);
434 ND_PRINT(", win %u", win);
437 ND_PRINT(", urg %u", urp);
439 * Handle any options.
441 if (hlen > sizeof(*tp)) {
443 u_int i, opt, datalen;
447 cp = (const u_char *)tp + sizeof(*tp);
448 ND_PRINT(", options [");
458 cp++; /* total including type, len */
459 if (len < 2 || len > hlen)
461 --hlen; /* account for length byte */
463 --hlen; /* account for type byte */
466 /* Bail if "l" bytes of data are not left or were not captured */
467 #define LENCHECK(l) { if ((l) > hlen) goto bad; ND_TCHECK_LEN(cp, l); }
470 ND_PRINT("%s", tok2str(tcp_option_values, "unknown-%u", opt));
477 ND_PRINT(" %u", GET_BE_U_2(cp));
483 ND_PRINT(" %u", GET_U_1(cp));
488 if (datalen % 8 != 0) {
489 ND_PRINT(" invalid sack");
493 ND_PRINT(" %u ", datalen / 8);
494 for (i = 0; i < datalen; i += 8) {
496 s = GET_BE_U_4(cp + i);
498 e = GET_BE_U_4(cp + i + 4);
506 ND_PRINT("{%u:%u}", s, e);
515 case TCPOPT_ECHOREPLY:
518 * those options share their semantics.
523 ND_PRINT(" %u", GET_BE_U_4(cp));
526 case TCPOPT_TIMESTAMP:
529 ND_PRINT(" val %u ecr %u",
534 case TCPOPT_SIGNATURE:
535 datalen = TCP_SIGLEN;
538 #ifdef HAVE_LIBCRYPTO
539 switch (tcp_verify_signature(ndo, ip, tp,
540 bp + TH_OFF(tp) * 4, length, cp)) {
542 case SIGNATURE_VALID:
546 case SIGNATURE_INVALID:
547 nd_print_invalid(ndo);
550 case CANT_CHECK_SIGNATURE:
551 ND_PRINT("can't check - ");
552 for (i = 0; i < TCP_SIGLEN; ++i)
558 for (i = 0; i < TCP_SIGLEN; ++i)
559 ND_PRINT("%02x", GET_U_1(cp + i));
566 ND_PRINT(" cap %02x id %u", GET_U_1(cp),
572 /* RFC 5925 Section 2.2:
573 * "The Length value MUST be greater than or equal to 4."
574 * (This includes the Kind and Length fields already processed
578 nd_print_invalid(ndo);
581 ND_PRINT(" keyid %u", GET_U_1(cp));
583 ND_PRINT(" rnextkeyid %u",
587 for (i = 2; i < datalen; i++) {
600 * Nothing interesting.
608 utoval = GET_BE_U_2(cp);
609 ND_PRINT(" 0x%x", utoval);
611 utoval = (utoval >> 1) * 60;
614 ND_PRINT(" %u", utoval);
619 const u_char *snapend_save;
624 /* Update the snapend to the end of the option
625 * before calling mptcp_print(). Some options
626 * (MPTCP or others) may be present after a
627 * MPTCP option. This prevents that, in
628 * mptcp_print(), the remaining length < the
631 snapend_save = ndo->ndo_snapend;
632 ndo->ndo_snapend = ND_MIN(cp - 2 + len,
634 ret = mptcp_print(ndo, cp - 2, len, flags);
635 ndo->ndo_snapend = snapend_save;
641 case TCPOPT_FASTOPEN:
645 print_tcp_fastopen_option(ndo, cp, datalen, FALSE);
648 case TCPOPT_EXPERIMENT2:
654 magic = GET_BE_U_2(cp);
659 case 0xf989: /* TCP Fast Open RFC 7413 */
660 print_tcp_fastopen_option(ndo, cp + 2, datalen - 2, TRUE);
664 /* Unknown magic number */
665 ND_PRINT("%04x", magic);
674 for (i = 0; i < datalen; ++i) {
676 ND_PRINT("%02x", GET_U_1(cp + i));
681 /* Account for data printed */
685 /* Check specification against observed length */
686 ++datalen; /* option octet */
687 if (!ZEROLENOPT(opt))
688 ++datalen; /* size octet */
690 ND_PRINT("[len %u]", len);
692 if (opt == TCPOPT_EOL)
699 * Print length field before crawling down the stack.
701 ND_PRINT(", length %u", length);
707 * Decode payload if necessary.
709 header_len = TH_OFF(tp) * 4;
711 * Do a bounds check before decoding the payload.
712 * At least the header data is required.
714 if (!ND_TTEST_LEN(bp, header_len)) {
715 ND_PRINT(" [remaining caplen(%u) < header length(%u)]",
716 ND_BYTES_AVAILABLE_AFTER(bp), header_len);
717 nd_trunc_longjmp(ndo);
720 if ((flags & TH_RST) && ndo->ndo_vflag) {
721 print_tcp_rst_data(ndo, bp, length);
725 if (ndo->ndo_packettype) {
726 switch (ndo->ndo_packettype) {
728 zmtp1_print(ndo, bp, length);
731 resp_print(ndo, bp, length);
734 /* over_tcp: TRUE, is_mdns: FALSE */
735 domain_print(ndo, bp, length, TRUE, FALSE);
741 if (IS_SRC_OR_DST_PORT(TELNET_PORT)) {
742 telnet_print(ndo, bp, length);
743 } else if (IS_SRC_OR_DST_PORT(SMTP_PORT)) {
745 smtp_print(ndo, bp, length);
746 } else if (IS_SRC_OR_DST_PORT(WHOIS_PORT)) {
748 whois_print(ndo, bp, length);
749 } else if (IS_SRC_OR_DST_PORT(BGP_PORT))
750 bgp_print(ndo, bp, length);
751 else if (IS_SRC_OR_DST_PORT(PPTP_PORT))
753 else if (IS_SRC_OR_DST_PORT(REDIS_PORT))
754 resp_print(ndo, bp, length);
755 else if (IS_SRC_OR_DST_PORT(SSH_PORT))
756 ssh_print(ndo, bp, length);
758 else if (IS_SRC_OR_DST_PORT(NETBIOS_SSN_PORT))
759 nbt_tcp_print(ndo, bp, length);
760 else if (IS_SRC_OR_DST_PORT(SMB_PORT))
761 smb_tcp_print(ndo, bp, length);
763 else if (IS_SRC_OR_DST_PORT(BEEP_PORT))
764 beep_print(ndo, bp, length);
765 else if (IS_SRC_OR_DST_PORT(OPENFLOW_PORT_OLD) || IS_SRC_OR_DST_PORT(OPENFLOW_PORT_IANA))
766 openflow_print(ndo, bp, length);
767 else if (IS_SRC_OR_DST_PORT(FTP_PORT)) {
769 ftp_print(ndo, bp, length);
770 } else if (IS_SRC_OR_DST_PORT(HTTP_PORT) || IS_SRC_OR_DST_PORT(HTTP_PORT_ALT)) {
772 http_print(ndo, bp, length);
773 } else if (IS_SRC_OR_DST_PORT(RTSP_PORT) || IS_SRC_OR_DST_PORT(RTSP_PORT_ALT)) {
775 rtsp_print(ndo, bp, length);
776 } else if (IS_SRC_OR_DST_PORT(NAMESERVER_PORT)) {
777 /* over_tcp: TRUE, is_mdns: FALSE */
778 domain_print(ndo, bp, length, TRUE, FALSE);
779 } else if (IS_SRC_OR_DST_PORT(MSDP_PORT)) {
780 msdp_print(ndo, bp, length);
781 } else if (IS_SRC_OR_DST_PORT(RPKI_RTR_PORT)) {
782 rpki_rtr_print(ndo, bp, length);
783 } else if (IS_SRC_OR_DST_PORT(LDP_PORT)) {
784 ldp_print(ndo, bp, length);
785 } else if ((IS_SRC_OR_DST_PORT(NFS_PORT)) &&
786 length >= 4 && ND_TTEST_4(bp)) {
788 * If data present, header length valid, and NFS port used,
790 * Pass offset of data plus 4 bytes for RPC TCP msg length
791 * to NFS print routines.
794 const struct sunrpc_msg *rp;
795 enum sunrpc_msg_type direction;
797 fraglen = GET_BE_U_4(bp) & 0x7FFFFFFF;
798 if (fraglen > (length) - 4)
799 fraglen = (length) - 4;
800 rp = (const struct sunrpc_msg *)(bp + 4);
801 if (ND_TTEST_4(rp->rm_direction)) {
802 direction = (enum sunrpc_msg_type) GET_BE_U_4(rp->rm_direction);
803 if (dport == NFS_PORT && direction == SUNRPC_CALL) {
804 ND_PRINT(": NFS request xid %u ",
805 GET_BE_U_4(rp->rm_xid));
806 nfsreq_noaddr_print(ndo, (const u_char *)rp, fraglen, (const u_char *)ip);
809 if (sport == NFS_PORT && direction == SUNRPC_REPLY) {
810 ND_PRINT(": NFS reply xid %u ",
811 GET_BE_U_4(rp->rm_xid));
812 nfsreply_noaddr_print(ndo, (const u_char *)rp, fraglen, (const u_char *)ip);
820 ND_PRINT("[bad opt]");
831 * RFC1122 says the following on data in RST segments:
833 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
835 * A TCP SHOULD allow a received RST segment to include data.
838 * It has been suggested that a RST segment could contain
839 * ASCII text that encoded and explained the cause of the
840 * RST. No standard has yet been established for such
846 print_tcp_rst_data(netdissect_options *ndo,
847 const u_char *sp, u_int length)
851 ND_PRINT(ND_TTEST_LEN(sp, length) ? " [RST" : " [!RST");
852 if (length > MAX_RST_DATA_LEN) {
853 length = MAX_RST_DATA_LEN; /* can use -X for longer */
854 ND_PRINT("+"); /* indicate we truncate */
857 while (length && sp < ndo->ndo_snapend) {
860 fn_print_char(ndo, c);
867 print_tcp_fastopen_option(netdissect_options *ndo, const u_char *cp,
868 u_int datalen, int exp)
876 /* Fast Open Cookie Request */
877 ND_PRINT(" cookiereq");
879 /* Fast Open Cookie */
880 if (datalen % 2 != 0 || datalen < 4 || datalen > 16) {
881 nd_print_invalid(ndo);
883 ND_PRINT(" cookie ");
884 for (i = 0; i < datalen; ++i)
885 ND_PRINT("%02x", GET_U_1(cp + i));
890 #ifdef HAVE_LIBCRYPTO
893 tcp_verify_signature(netdissect_options *ndo,
894 const struct ip *ip, const struct tcphdr *tp,
895 const u_char *data, u_int length, const u_char *rcvsig)
898 u_char sig[TCP_SIGLEN];
901 uint16_t savecsum, tlen;
902 const struct ip6_hdr *ip6;
906 if (data + length > ndo->ndo_snapend) {
907 ND_PRINT("snaplen too short, ");
908 return (CANT_CHECK_SIGNATURE);
913 if (ndo->ndo_sigsecret == NULL) {
914 ND_PRINT("shared secret not supplied with -M, ");
915 return (CANT_CHECK_SIGNATURE);
920 * Step 1: Update MD5 hash with IP pseudo-header.
923 MD5_Update(&ctx, (const char *)&ip->ip_src, sizeof(ip->ip_src));
924 MD5_Update(&ctx, (const char *)&ip->ip_dst, sizeof(ip->ip_dst));
925 MD5_Update(&ctx, (const char *)&zero_proto, sizeof(zero_proto));
926 MD5_Update(&ctx, (const char *)&ip->ip_p, sizeof(ip->ip_p));
927 tlen = GET_BE_U_2(ip->ip_len) - IP_HL(ip) * 4;
929 MD5_Update(&ctx, (const char *)&tlen, sizeof(tlen));
930 } else if (IP_V(ip) == 6) {
931 ip6 = (const struct ip6_hdr *)ip;
932 MD5_Update(&ctx, (const char *)&ip6->ip6_src, sizeof(ip6->ip6_src));
933 MD5_Update(&ctx, (const char *)&ip6->ip6_dst, sizeof(ip6->ip6_dst));
934 len32 = htonl(GET_BE_U_2(ip6->ip6_plen));
935 MD5_Update(&ctx, (const char *)&len32, sizeof(len32));
937 MD5_Update(&ctx, (const char *)&nxt, sizeof(nxt));
938 MD5_Update(&ctx, (const char *)&nxt, sizeof(nxt));
939 MD5_Update(&ctx, (const char *)&nxt, sizeof(nxt));
941 MD5_Update(&ctx, (const char *)&nxt, sizeof(nxt));
943 ND_PRINT("IP version not 4 or 6, ");
944 return (CANT_CHECK_SIGNATURE);
948 * Step 2: Update MD5 hash with TCP header, excluding options.
949 * The TCP checksum must be set to zero.
951 memcpy(&savecsum, tp1.th_sum, sizeof(savecsum));
952 memset(tp1.th_sum, 0, sizeof(tp1.th_sum));
953 MD5_Update(&ctx, (const char *)&tp1, sizeof(struct tcphdr));
954 memcpy(tp1.th_sum, &savecsum, sizeof(tp1.th_sum));
956 * Step 3: Update MD5 hash with TCP segment data, if present.
959 MD5_Update(&ctx, data, length);
961 * Step 4: Update MD5 hash with shared secret.
963 MD5_Update(&ctx, ndo->ndo_sigsecret, strlen(ndo->ndo_sigsecret));
964 MD5_Final(sig, &ctx);
966 if (memcmp(rcvsig, sig, TCP_SIGLEN) == 0)
967 return (SIGNATURE_VALID);
969 return (SIGNATURE_INVALID);
972 #endif /* HAVE_LIBCRYPTO */