print-mptcp.c - platform/external/tcpdump - Git at Google

 /**
  * Copyright (c) 2012
  *
  * Gregory Detal <[email protected]>
  * Christoph Paasch <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  *
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * 3. Neither the name of the University nor of the Laboratory may be used
  *    to endorse or promote products derived from this software without
  *    specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */

 /* \summary: Multipath TCP (MPTCP) printer */

 /* specification: RFC 6824 */

 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif

 #include <netdissect-stdinc.h>

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

 #include "tcp.h"

 #define MPTCP_SUB_CAPABLE       0x0
 #define MPTCP_SUB_JOIN          0x1
 #define MPTCP_SUB_DSS           0x2
 #define MPTCP_SUB_ADD_ADDR      0x3
 #define MPTCP_SUB_REMOVE_ADDR   0x4
 #define MPTCP_SUB_PRIO          0x5
 #define MPTCP_SUB_FAIL          0x6
 #define MPTCP_SUB_FCLOSE        0x7

 struct mptcp_option {
         uint8_t        kind;
         uint8_t        len;
         uint8_t        sub_etc;        /* subtype upper 4 bits, other stuff lower 4 bits */
 };

 #define MPTCP_OPT_SUBTYPE(sub_etc)      (((sub_etc) >> 4) & 0xF)

 struct mp_capable {
         uint8_t        kind;
         uint8_t        len;
         uint8_t        sub_ver;
         uint8_t        flags;
         uint8_t        sender_key[8];
         uint8_t        receiver_key[8];
 };

 #define MP_CAPABLE_OPT_VERSION(sub_ver) (((sub_ver) >> 0) & 0xF)
 #define MP_CAPABLE_C                    0x80
 #define MP_CAPABLE_S                    0x01

 struct mp_join {
         uint8_t        kind;
         uint8_t        len;
         uint8_t        sub_b;
         uint8_t        addr_id;
         union {
                 struct {
                         uint8_t         token[4];
                         uint8_t         nonce[4];
                 } syn;
                 struct {
                         uint8_t         mac[8];
                         uint8_t         nonce[4];
                 } synack;
                 struct {
                         uint8_t        mac[20];
                 } ack;
         } u;
 };

 #define MP_JOIN_B                       0x01

 struct mp_dss {
         uint8_t        kind;
         uint8_t        len;
         uint8_t        sub;
         uint8_t        flags;
 };

 #define MP_DSS_F                        0x10
 #define MP_DSS_m                        0x08
 #define MP_DSS_M                        0x04
 #define MP_DSS_a                        0x02
 #define MP_DSS_A                        0x01

 struct mp_add_addr {
         uint8_t        kind;
         uint8_t        len;
         uint8_t        sub_ipver;
         uint8_t        addr_id;
         union {
                 struct {
                         uint8_t         addr[4];
                         uint8_t         port[2];
                 } v4;
                 struct {
                         uint8_t         addr[16];
                         uint8_t         port[2];
                 } v6;
         } u;
 };

 #define MP_ADD_ADDR_IPVER(sub_ipver)    (((sub_ipver) >> 0) & 0xF)

 struct mp_remove_addr {
         uint8_t        kind;
         uint8_t        len;
         uint8_t        sub;
         /* list of addr_id */
         uint8_t        addrs_id;
 };

 struct mp_fail {
         uint8_t        kind;
         uint8_t        len;
         uint8_t        sub;
         uint8_t        resv;
         uint8_t        data_seq[8];
 };

 struct mp_close {
         uint8_t        kind;
         uint8_t        len;
         uint8_t        sub;
         uint8_t        rsv;
         uint8_t        key[8];
 };

 struct mp_prio {
         uint8_t        kind;
         uint8_t        len;
         uint8_t        sub_b;
         uint8_t        addr_id;
 };

 #define MP_PRIO_B                       0x01

 static int
 dummy_print(netdissect_options *ndo _U_,
             const u_char *opt _U_, u_int opt_len _U_, u_char flags _U_)
 {
         return 1;
 }

 static int
 mp_capable_print(netdissect_options *ndo,
                  const u_char *opt, u_int opt_len, u_char flags)
 {
         const struct mp_capable *mpc = (const struct mp_capable *) opt;

         if (!(opt_len == 12 && (flags & TH_SYN)) &&
             !(opt_len == 20 && (flags & (TH_SYN | TH_ACK)) == TH_ACK))
                 return 0;

         if (MP_CAPABLE_OPT_VERSION(mpc->sub_ver) != 0) {
                 ND_PRINT((ndo, " Unknown Version (%d)", MP_CAPABLE_OPT_VERSION(mpc->sub_ver)));
                 return 1;
         }

         if (mpc->flags & MP_CAPABLE_C)
                 ND_PRINT((ndo, " csum"));
         ND_PRINT((ndo, " {0x%" PRIx64, EXTRACT_64BITS(mpc->sender_key)));
         if (opt_len == 20) /* ACK */
                 ND_PRINT((ndo, ",0x%" PRIx64, EXTRACT_64BITS(mpc->receiver_key)));
         ND_PRINT((ndo, "}"));
         return 1;
 }

 static int
 mp_join_print(netdissect_options *ndo,
               const u_char *opt, u_int opt_len, u_char flags)
 {
         const struct mp_join *mpj = (const struct mp_join *) opt;

         if (!(opt_len == 12 && (flags & TH_SYN)) &&
             !(opt_len == 16 && (flags & (TH_SYN | TH_ACK)) == (TH_SYN | TH_ACK)) &&
             !(opt_len == 24 && (flags & TH_ACK)))
                 return 0;

         if (opt_len != 24) {
                 if (mpj->sub_b & MP_JOIN_B)
                         ND_PRINT((ndo, " backup"));
                 ND_PRINT((ndo, " id %u", mpj->addr_id));
         }

         switch (opt_len) {
         case 12: /* SYN */
                 ND_PRINT((ndo, " token 0x%x" " nonce 0x%x",
                         EXTRACT_32BITS(mpj->u.syn.token),
                         EXTRACT_32BITS(mpj->u.syn.nonce)));
                 break;
         case 16: /* SYN/ACK */
                 ND_PRINT((ndo, " hmac 0x%" PRIx64 " nonce 0x%x",
                         EXTRACT_64BITS(mpj->u.synack.mac),
                         EXTRACT_32BITS(mpj->u.synack.nonce)));
                 break;
         case 24: {/* ACK */
                 size_t i;
                 ND_PRINT((ndo, " hmac 0x"));
                 for (i = 0; i < sizeof(mpj->u.ack.mac); ++i)
                         ND_PRINT((ndo, "%02x", mpj->u.ack.mac[i]));
         }
         default:
                 break;
         }
         return 1;
 }

 static int
 mp_dss_print(netdissect_options *ndo,
              const u_char *opt, u_int opt_len, u_char flags)
 {
         const struct mp_dss *mdss = (const struct mp_dss *) opt;

         /* We need the flags, at a minimum. */
         if (opt_len < 4)
                 return 0;

         if (flags & TH_SYN)
                 return 0;

         if (mdss->flags & MP_DSS_F)
                 ND_PRINT((ndo, " fin"));

         opt += 4;
         opt_len -= 4;
         if (mdss->flags & MP_DSS_A) {
                 /* Ack present */
                 ND_PRINT((ndo, " ack "));
                 /*
                  * If the a flag is set, we have an 8-byte ack; if it's
                  * clear, we have a 4-byte ack.
                  */
                 if (mdss->flags & MP_DSS_a) {
                         if (opt_len < 8)
                                 return 0;
                         ND_PRINT((ndo, "%" PRIu64, EXTRACT_64BITS(opt)));
                         opt += 8;
                         opt_len -= 8;
                 } else {
                         if (opt_len < 4)
                                 return 0;
                         ND_PRINT((ndo, "%u", EXTRACT_32BITS(opt)));
                         opt += 4;
                         opt_len -= 4;
                 }
         }

         if (mdss->flags & MP_DSS_M) {
                 /*
                  * Data Sequence Number (DSN), Subflow Sequence Number (SSN),
                  * Data-Level Length present, and Checksum possibly present.
                  */
                 ND_PRINT((ndo, " seq "));
 		/*
                  * If the m flag is set, we have an 8-byte NDS; if it's clear,
                  * we have a 4-byte DSN.
                  */
                 if (mdss->flags & MP_DSS_m) {
                         if (opt_len < 8)
                                 return 0;
                         ND_PRINT((ndo, "%" PRIu64, EXTRACT_64BITS(opt)));
                         opt += 8;
                         opt_len -= 8;
                 } else {
                         if (opt_len < 4)
                                 return 0;
                         ND_PRINT((ndo, "%u", EXTRACT_32BITS(opt)));
                         opt += 4;
                         opt_len -= 4;
                 }
                 if (opt_len < 4)
                         return 0;
                 ND_PRINT((ndo, " subseq %u", EXTRACT_32BITS(opt)));
                 opt += 4;
                 opt_len -= 4;
                 if (opt_len < 2)
                         return 0;
                 ND_PRINT((ndo, " len %u", EXTRACT_16BITS(opt)));
                 opt += 2;
                 opt_len -= 2;

                 /*
                  * The Checksum is present only if negotiated.
                  * If there are at least 2 bytes left, process the next 2
                  * bytes as the Checksum.
                  */
                 if (opt_len >= 2) {
                         ND_PRINT((ndo, " csum 0x%x", EXTRACT_16BITS(opt)));
                         opt_len -= 2;
                 }
         }
         if (opt_len != 0)
                 return 0;
         return 1;
 }

 static int
 add_addr_print(netdissect_options *ndo,
                const u_char *opt, u_int opt_len, u_char flags _U_)
 {
         const struct mp_add_addr *add_addr = (const struct mp_add_addr *) opt;
         u_int ipver = MP_ADD_ADDR_IPVER(add_addr->sub_ipver);

         if (!((opt_len == 8 || opt_len == 10) && ipver == 4) &&
             !((opt_len == 20 || opt_len == 22) && ipver == 6))
                 return 0;

         ND_PRINT((ndo, " id %u", add_addr->addr_id));
         switch (ipver) {
         case 4:
                 ND_PRINT((ndo, " %s", ipaddr_string(ndo, add_addr->u.v4.addr)));
                 if (opt_len == 10)
                         ND_PRINT((ndo, ":%u", EXTRACT_16BITS(add_addr->u.v4.port)));
                 break;
         case 6:
                 ND_PRINT((ndo, " %s", ip6addr_string(ndo, add_addr->u.v6.addr)));
                 if (opt_len == 22)
                         ND_PRINT((ndo, ":%u", EXTRACT_16BITS(add_addr->u.v6.port)));
                 break;
         default:
                 return 0;
         }

         return 1;
 }

 static int
 remove_addr_print(netdissect_options *ndo,
                   const u_char *opt, u_int opt_len, u_char flags _U_)
 {
         const struct mp_remove_addr *remove_addr = (const struct mp_remove_addr *) opt;
         const uint8_t *addr_id = &remove_addr->addrs_id;

         if (opt_len < 4)
                 return 0;

         opt_len -= 3;
         ND_PRINT((ndo, " id"));
         while (opt_len--)
                 ND_PRINT((ndo, " %u", *addr_id++));
         return 1;
 }

 static int
 mp_prio_print(netdissect_options *ndo,
               const u_char *opt, u_int opt_len, u_char flags _U_)
 {
         const struct mp_prio *mpp = (const struct mp_prio *) opt;

         if (opt_len != 3 && opt_len != 4)
                 return 0;

         if (mpp->sub_b & MP_PRIO_B)
                 ND_PRINT((ndo, " backup"));
         else
                 ND_PRINT((ndo, " non-backup"));
         if (opt_len == 4)
                 ND_PRINT((ndo, " id %u", mpp->addr_id));

         return 1;
 }

 static int
 mp_fail_print(netdissect_options *ndo,
               const u_char *opt, u_int opt_len, u_char flags _U_)
 {
         if (opt_len != 12)
                 return 0;

         ND_PRINT((ndo, " seq %" PRIu64, EXTRACT_64BITS(opt + 4)));
         return 1;
 }

 static int
 mp_fast_close_print(netdissect_options *ndo,
                     const u_char *opt, u_int opt_len, u_char flags _U_)
 {
         if (opt_len != 12)
                 return 0;

         ND_PRINT((ndo, " key 0x%" PRIx64, EXTRACT_64BITS(opt + 4)));
         return 1;
 }

 static const struct {
         const char *name;
         int (*print)(netdissect_options *, const u_char *, u_int, u_char);
 } mptcp_options[] = {
         { "capable", mp_capable_print},
         { "join",       mp_join_print },
         { "dss",        mp_dss_print },
         { "add-addr",   add_addr_print },
         { "rem-addr",   remove_addr_print },
         { "prio",       mp_prio_print },
         { "fail",       mp_fail_print },
         { "fast-close", mp_fast_close_print },
         { "unknown",    dummy_print },
 };

 int
 mptcp_print(netdissect_options *ndo,
             const u_char *cp, u_int len, u_char flags)
 {
         const struct mptcp_option *opt;
         u_int subtype;

         if (len < 3)
                 return 0;

         opt = (const struct mptcp_option *) cp;
         subtype = min(MPTCP_OPT_SUBTYPE(opt->sub_etc), MPTCP_SUB_FCLOSE + 1);

         ND_PRINT((ndo, " %s", mptcp_options[subtype].name));
         return mptcp_options[subtype].print(ndo, cp, len, flags);
 }
	/**
	* Copyright (c) 2012
	*
	* Gregory Detal <[email protected]>
	* Christoph Paasch <[email protected]>
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	*
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	*
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* 3. Neither the name of the University nor of the Laboratory may be used
	* to endorse or promote products derived from this software without
	* specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	* SUCH DAMAGE.
	*/

	/* \summary: Multipath TCP (MPTCP) printer */

	/* specification: RFC 6824 */

	#ifdef HAVE_CONFIG_H
	#include "config.h"
	#endif

	#include <netdissect-stdinc.h>

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

	#include "tcp.h"

	#define MPTCP_SUB_CAPABLE 0x0
	#define MPTCP_SUB_JOIN 0x1
	#define MPTCP_SUB_DSS 0x2
	#define MPTCP_SUB_ADD_ADDR 0x3
	#define MPTCP_SUB_REMOVE_ADDR 0x4
	#define MPTCP_SUB_PRIO 0x5
	#define MPTCP_SUB_FAIL 0x6
	#define MPTCP_SUB_FCLOSE 0x7

	struct mptcp_option {
	uint8_t kind;
	uint8_t len;
	uint8_t sub_etc; /* subtype upper 4 bits, other stuff lower 4 bits */
	};

	#define MPTCP_OPT_SUBTYPE(sub_etc) (((sub_etc) >> 4) & 0xF)

	struct mp_capable {
	uint8_t kind;
	uint8_t len;
	uint8_t sub_ver;
	uint8_t flags;
	uint8_t sender_key[8];
	uint8_t receiver_key[8];
	};

	#define MP_CAPABLE_OPT_VERSION(sub_ver) (((sub_ver) >> 0) & 0xF)
	#define MP_CAPABLE_C 0x80
	#define MP_CAPABLE_S 0x01

	struct mp_join {
	uint8_t kind;
	uint8_t len;
	uint8_t sub_b;
	uint8_t addr_id;
	union {
	struct {
	uint8_t token[4];
	uint8_t nonce[4];
	} syn;
	struct {
	uint8_t mac[8];
	uint8_t nonce[4];
	} synack;
	struct {
	uint8_t mac[20];
	} ack;
	} u;
	};

	#define MP_JOIN_B 0x01

	struct mp_dss {
	uint8_t kind;
	uint8_t len;
	uint8_t sub;
	uint8_t flags;
	};

	#define MP_DSS_F 0x10
	#define MP_DSS_m 0x08
	#define MP_DSS_M 0x04
	#define MP_DSS_a 0x02
	#define MP_DSS_A 0x01

	struct mp_add_addr {
	uint8_t kind;
	uint8_t len;
	uint8_t sub_ipver;
	uint8_t addr_id;
	union {
	struct {
	uint8_t addr[4];
	uint8_t port[2];
	} v4;
	struct {
	uint8_t addr[16];
	uint8_t port[2];
	} v6;
	} u;
	};

	#define MP_ADD_ADDR_IPVER(sub_ipver) (((sub_ipver) >> 0) & 0xF)

	struct mp_remove_addr {
	uint8_t kind;
	uint8_t len;
	uint8_t sub;
	/* list of addr_id */
	uint8_t addrs_id;
	};

	struct mp_fail {
	uint8_t kind;
	uint8_t len;
	uint8_t sub;
	uint8_t resv;
	uint8_t data_seq[8];
	};

	struct mp_close {
	uint8_t kind;
	uint8_t len;
	uint8_t sub;
	uint8_t rsv;
	uint8_t key[8];
	};

	struct mp_prio {
	uint8_t kind;
	uint8_t len;
	uint8_t sub_b;
	uint8_t addr_id;
	};

	#define MP_PRIO_B 0x01

	static int
	dummy_print(netdissect_options *ndo _U_,
	const u_char *opt _U_, u_int opt_len _U_, u_char flags _U_)
	{
	return 1;
	}

	static int
	mp_capable_print(netdissect_options *ndo,
	const u_char *opt, u_int opt_len, u_char flags)
	{
	const struct mp_capable mpc = (const struct mp_capable ) opt;

	if (!(opt_len == 12 && (flags & TH_SYN)) &&
	!(opt_len == 20 && (flags & (TH_SYN \| TH_ACK)) == TH_ACK))
	return 0;

	if (MP_CAPABLE_OPT_VERSION(mpc->sub_ver) != 0) {
	ND_PRINT((ndo, " Unknown Version (%d)", MP_CAPABLE_OPT_VERSION(mpc->sub_ver)));
	return 1;
	}

	if (mpc->flags & MP_CAPABLE_C)
	ND_PRINT((ndo, " csum"));
	ND_PRINT((ndo, " {0x%" PRIx64, EXTRACT_64BITS(mpc->sender_key)));
	if (opt_len == 20) /* ACK */
	ND_PRINT((ndo, ",0x%" PRIx64, EXTRACT_64BITS(mpc->receiver_key)));
	ND_PRINT((ndo, "}"));
	return 1;
	}

	static int
	mp_join_print(netdissect_options *ndo,
	const u_char *opt, u_int opt_len, u_char flags)
	{
	const struct mp_join mpj = (const struct mp_join ) opt;

	if (!(opt_len == 12 && (flags & TH_SYN)) &&
	!(opt_len == 16 && (flags & (TH_SYN \| TH_ACK)) == (TH_SYN \| TH_ACK)) &&
	!(opt_len == 24 && (flags & TH_ACK)))
	return 0;

	if (opt_len != 24) {
	if (mpj->sub_b & MP_JOIN_B)
	ND_PRINT((ndo, " backup"));
	ND_PRINT((ndo, " id %u", mpj->addr_id));
	}

	switch (opt_len) {
	case 12: /* SYN */
	ND_PRINT((ndo, " token 0x%x" " nonce 0x%x",
	EXTRACT_32BITS(mpj->u.syn.token),
	EXTRACT_32BITS(mpj->u.syn.nonce)));
	break;
	case 16: /* SYN/ACK */
	ND_PRINT((ndo, " hmac 0x%" PRIx64 " nonce 0x%x",
	EXTRACT_64BITS(mpj->u.synack.mac),
	EXTRACT_32BITS(mpj->u.synack.nonce)));
	break;
	case 24: {/* ACK */
	size_t i;
	ND_PRINT((ndo, " hmac 0x"));
	for (i = 0; i < sizeof(mpj->u.ack.mac); ++i)
	ND_PRINT((ndo, "%02x", mpj->u.ack.mac[i]));
	}
	default:
	break;
	}
	return 1;
	}

	static int
	mp_dss_print(netdissect_options *ndo,
	const u_char *opt, u_int opt_len, u_char flags)
	{
	const struct mp_dss mdss = (const struct mp_dss ) opt;

	/* We need the flags, at a minimum. */
	if (opt_len < 4)
	return 0;

	if (flags & TH_SYN)
	return 0;

	if (mdss->flags & MP_DSS_F)
	ND_PRINT((ndo, " fin"));

	opt += 4;
	opt_len -= 4;
	if (mdss->flags & MP_DSS_A) {
	/* Ack present */
	ND_PRINT((ndo, " ack "));
	/*
	* If the a flag is set, we have an 8-byte ack; if it's
	* clear, we have a 4-byte ack.
	*/
	if (mdss->flags & MP_DSS_a) {
	if (opt_len < 8)
	return 0;
	ND_PRINT((ndo, "%" PRIu64, EXTRACT_64BITS(opt)));
	opt += 8;
	opt_len -= 8;
	} else {
	if (opt_len < 4)
	return 0;
	ND_PRINT((ndo, "%u", EXTRACT_32BITS(opt)));
	opt += 4;
	opt_len -= 4;
	}
	}

	if (mdss->flags & MP_DSS_M) {
	/*
	* Data Sequence Number (DSN), Subflow Sequence Number (SSN),
	* Data-Level Length present, and Checksum possibly present.
	*/
	ND_PRINT((ndo, " seq "));
	/*
	* If the m flag is set, we have an 8-byte NDS; if it's clear,
	* we have a 4-byte DSN.
	*/
	if (mdss->flags & MP_DSS_m) {
	if (opt_len < 8)
	return 0;
	ND_PRINT((ndo, "%" PRIu64, EXTRACT_64BITS(opt)));
	opt += 8;
	opt_len -= 8;
	} else {
	if (opt_len < 4)
	return 0;
	ND_PRINT((ndo, "%u", EXTRACT_32BITS(opt)));
	opt += 4;
	opt_len -= 4;
	}
	if (opt_len < 4)
	return 0;
	ND_PRINT((ndo, " subseq %u", EXTRACT_32BITS(opt)));
	opt += 4;
	opt_len -= 4;
	if (opt_len < 2)
	return 0;
	ND_PRINT((ndo, " len %u", EXTRACT_16BITS(opt)));
	opt += 2;
	opt_len -= 2;

	/*
	* The Checksum is present only if negotiated.
	* If there are at least 2 bytes left, process the next 2
	* bytes as the Checksum.
	*/
	if (opt_len >= 2) {
	ND_PRINT((ndo, " csum 0x%x", EXTRACT_16BITS(opt)));
	opt_len -= 2;
	}
	}
	if (opt_len != 0)
	return 0;
	return 1;
	}

	static int
	add_addr_print(netdissect_options *ndo,
	const u_char *opt, u_int opt_len, u_char flags _U_)
	{
	const struct mp_add_addr add_addr = (const struct mp_add_addr ) opt;
	u_int ipver = MP_ADD_ADDR_IPVER(add_addr->sub_ipver);

	if (!((opt_len == 8 \|\| opt_len == 10) && ipver == 4) &&
	!((opt_len == 20 \|\| opt_len == 22) && ipver == 6))
	return 0;

	ND_PRINT((ndo, " id %u", add_addr->addr_id));
	switch (ipver) {
	case 4:
	ND_PRINT((ndo, " %s", ipaddr_string(ndo, add_addr->u.v4.addr)));
	if (opt_len == 10)
	ND_PRINT((ndo, ":%u", EXTRACT_16BITS(add_addr->u.v4.port)));
	break;
	case 6:
	ND_PRINT((ndo, " %s", ip6addr_string(ndo, add_addr->u.v6.addr)));
	if (opt_len == 22)
	ND_PRINT((ndo, ":%u", EXTRACT_16BITS(add_addr->u.v6.port)));
	break;
	default:
	return 0;
	}

	return 1;
	}

	static int
	remove_addr_print(netdissect_options *ndo,
	const u_char *opt, u_int opt_len, u_char flags _U_)
	{
	const struct mp_remove_addr remove_addr = (const struct mp_remove_addr ) opt;
	const uint8_t *addr_id = &remove_addr->addrs_id;

	if (opt_len < 4)
	return 0;

	opt_len -= 3;
	ND_PRINT((ndo, " id"));
	while (opt_len--)
	ND_PRINT((ndo, " %u", *addr_id++));
	return 1;
	}

	static int
	mp_prio_print(netdissect_options *ndo,
	const u_char *opt, u_int opt_len, u_char flags _U_)
	{
	const struct mp_prio mpp = (const struct mp_prio ) opt;

	if (opt_len != 3 && opt_len != 4)
	return 0;

	if (mpp->sub_b & MP_PRIO_B)
	ND_PRINT((ndo, " backup"));
	else
	ND_PRINT((ndo, " non-backup"));
	if (opt_len == 4)
	ND_PRINT((ndo, " id %u", mpp->addr_id));

	return 1;
	}

	static int
	mp_fail_print(netdissect_options *ndo,
	const u_char *opt, u_int opt_len, u_char flags _U_)
	{
	if (opt_len != 12)
	return 0;

	ND_PRINT((ndo, " seq %" PRIu64, EXTRACT_64BITS(opt + 4)));
	return 1;
	}

	static int
	mp_fast_close_print(netdissect_options *ndo,
	const u_char *opt, u_int opt_len, u_char flags _U_)
	{
	if (opt_len != 12)
	return 0;

	ND_PRINT((ndo, " key 0x%" PRIx64, EXTRACT_64BITS(opt + 4)));
	return 1;
	}

	static const struct {
	const char *name;
	int (print)(netdissect_options , const u_char *, u_int, u_char);
	} mptcp_options[] = {
	{ "capable", mp_capable_print},
	{ "join", mp_join_print },
	{ "dss", mp_dss_print },
	{ "add-addr", add_addr_print },
	{ "rem-addr", remove_addr_print },
	{ "prio", mp_prio_print },
	{ "fail", mp_fail_print },
	{ "fast-close", mp_fast_close_print },
	{ "unknown", dummy_print },
	};

	int
	mptcp_print(netdissect_options *ndo,
	const u_char *cp, u_int len, u_char flags)
	{
	const struct mptcp_option *opt;
	u_int subtype;

	if (len < 3)
	return 0;

	opt = (const struct mptcp_option *) cp;
	subtype = min(MPTCP_OPT_SUBTYPE(opt->sub_etc), MPTCP_SUB_FCLOSE + 1);

	ND_PRINT((ndo, " %s", mptcp_options[subtype].name));
	return mptcp_options[subtype].print(ndo, cp, len, flags);
	}