wireshark/epan/dissectors/packet-icmp.c

/* packet-icmp.c
 * Routines for ICMP - Internet Control Message Protocol
 *
 * $Id$
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * Monday, June 27, 2005
 * Support for the ICMP extensions for MPLS
 * (http://www.ietf.org/proceedings/01aug/I-D/draft-ietf-mpls-icmp-02.txt)
 * by   Maria-Luiza Crivat <luizacri@gmail.com>
 * &    Brice Augustin <bricecotte@gmail.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

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

#include <glib.h>

#include <epan/packet.h>
#include <epan/ipproto.h>
#include <epan/prefs.h>
#include <epan/in_cksum.h>

#include "packet-ip.h"


/* Decode the end of the ICMP payload as ICMP MPLS extensions
if the packet in the payload has more than 128 bytes */
static gboolean favor_icmp_mpls_ext = FALSE;

static int proto_icmp = -1;
static int hf_icmp_type = -1;
static int hf_icmp_code = -1;
static int hf_icmp_checksum = -1;
static int hf_icmp_checksum_bad = -1;
static int hf_icmp_ident = -1;
static int hf_icmp_seq_num = -1;
static int hf_icmp_mtu = -1;
static int hf_icmp_redir_gw = -1;


/* Mobile ip */
static int hf_icmp_mip_type = -1;
static int hf_icmp_mip_length = -1;
static int hf_icmp_mip_prefix_length = -1;
static int hf_icmp_mip_seq = -1;
static int hf_icmp_mip_life = -1;
static int hf_icmp_mip_flags = -1;
static int hf_icmp_mip_r = -1;
static int hf_icmp_mip_b = -1;
static int hf_icmp_mip_h = -1;
static int hf_icmp_mip_f = -1;
static int hf_icmp_mip_m = -1;
static int hf_icmp_mip_g = -1;
static int hf_icmp_mip_v = -1;
static int hf_icmp_mip_rt = -1;
static int hf_icmp_mip_u = -1;
static int hf_icmp_mip_x = -1;
static int hf_icmp_mip_reserved = -1;
static int hf_icmp_mip_coa = -1;
static int hf_icmp_mip_challenge = -1;

/* MPLS extensions */
static int hf_icmp_mpls = -1;
static int hf_icmp_mpls_version = -1;
static int hf_icmp_mpls_reserved = -1;
static int hf_icmp_mpls_checksum = -1;
static int hf_icmp_mpls_checksum_bad = -1;
static int hf_icmp_mpls_length = -1;
static int hf_icmp_mpls_class = -1;
static int hf_icmp_mpls_c_type = -1;
static int hf_icmp_mpls_label = -1;
static int hf_icmp_mpls_exp = -1;
static int hf_icmp_mpls_s = -1;
static int hf_icmp_mpls_ttl = -1;

static gint ett_icmp = -1;
static gint ett_icmp_mip = -1;
static gint ett_icmp_mip_flags = -1;

/* MPLS extensions */
static gint ett_icmp_mpls = -1;
static gint ett_icmp_mpls_object = -1;
static gint ett_icmp_mpls_stack_object = -1;

/* ICMP definitions */

#define ICMP_ECHOREPLY     0
#define ICMP_UNREACH       3
#define ICMP_SOURCEQUENCH  4
#define ICMP_REDIRECT      5
#define ICMP_ALTHOST       6
#define ICMP_ECHO          8
#define ICMP_RTRADVERT     9
#define ICMP_RTRSOLICIT   10
#define ICMP_TIMXCEED     11
#define ICMP_PARAMPROB    12
#define ICMP_TSTAMP       13
#define ICMP_TSTAMPREPLY  14
#define ICMP_IREQ         15
#define ICMP_IREQREPLY    16
#define ICMP_MASKREQ      17
#define ICMP_MASKREPLY    18
#define ICMP_PHOTURIS     40

/* ICMP UNREACHABLE */

#define ICMP_NET_UNREACH        0       /* Network Unreachable */
#define ICMP_HOST_UNREACH       1       /* Host Unreachable */
#define ICMP_PROT_UNREACH       2       /* Protocol Unreachable */
#define ICMP_PORT_UNREACH       3       /* Port Unreachable */
#define ICMP_FRAG_NEEDED        4       /* Fragmentation Needed/DF set */
#define ICMP_SR_FAILED          5       /* Source Route failed */
#define ICMP_NET_UNKNOWN        6
#define ICMP_HOST_UNKNOWN       7
#define ICMP_HOST_ISOLATED      8
#define ICMP_NET_ANO            9
#define ICMP_HOST_ANO           10
#define ICMP_NET_UNR_TOS        11
#define ICMP_HOST_UNR_TOS       12
#define ICMP_PKT_FILTERED       13      /* Packet filtered */
#define ICMP_PREC_VIOLATION     14      /* Precedence violation */
#define ICMP_PREC_CUTOFF        15      /* Precedence cut off */

#define ICMP_MIP_EXTENSION_PAD	0
#define ICMP_MIP_MOB_AGENT_ADV	16
#define ICMP_MIP_PREFIX_LENGTHS	19
#define ICMP_MIP_CHALLENGE	24

static dissector_handle_t ip_handle;
static dissector_handle_t data_handle;

static const value_string icmp_type_str[] = {
  { ICMP_ECHOREPLY,    "Echo (ping) reply" },
  { 1,                 "Reserved" },
  { 2,                 "Reserved" },
  { ICMP_UNREACH,      "Destination unreachable" },
  { ICMP_SOURCEQUENCH, "Source quench (flow control)" },
  { ICMP_REDIRECT,     "Redirect" },
  { ICMP_ALTHOST,      "Alternate host address" },
  { ICMP_ECHO,         "Echo (ping) request" },
  { ICMP_RTRADVERT,    "Router advertisement" },
  { ICMP_RTRSOLICIT,   "Router solicitation" },
  { ICMP_TIMXCEED,     "Time-to-live exceeded" },
  { ICMP_PARAMPROB,    "Parameter problem" },
  { ICMP_TSTAMP,       "Timestamp request" },
  { ICMP_TSTAMPREPLY,  "Timestamp reply" },
  { ICMP_IREQ,         "Information request" },
  { ICMP_IREQREPLY,    "Information reply" },
  { ICMP_MASKREQ,      "Address mask request" },
  { ICMP_MASKREPLY,    "Address mask reply" },
  { 19,                "Reserved (for security)" },
  { 30,                "Traceroute" },
  { 31,                "Datagram Conversion Error" },
  { 32,                "Mobile Host Redirect" },
  { 33,                "IPv6 Where-Are-You" },
  { 34,                "IPv6 I-Am-Here" },
  { 35,                "Mobile Registration Request" },
  { 36,                "Mobile Registration Reply" },
  { 37,                "Domain Name Request" },
  { 38,                "Domain Name Reply" },
  { 39,                "SKIP" },
  { ICMP_PHOTURIS,     "Photuris" },
  { 41,                "Experimental mobility protocols" },
  { 0, NULL }
};

static const value_string unreach_code_str[] = {
  { ICMP_NET_UNREACH,    "Network unreachable" },
  { ICMP_HOST_UNREACH,   "Host unreachable" },
  { ICMP_PROT_UNREACH,   "Protocol unreachable" },
  { ICMP_PORT_UNREACH,   "Port unreachable" },
  { ICMP_FRAG_NEEDED,    "Fragmentation needed" },
  { ICMP_SR_FAILED,      "Source route failed" },
  { ICMP_NET_UNKNOWN,    "Destination network unknown" },
  { ICMP_HOST_UNKNOWN,   "Destination host unknown" },
  { ICMP_HOST_ISOLATED,  "Source host isolated" },
  { ICMP_NET_ANO,        "Network administratively prohibited" },
  { ICMP_HOST_ANO,       "Host administratively prohibited" },
  { ICMP_NET_UNR_TOS,    "Network unreachable for TOS" },
  { ICMP_HOST_UNR_TOS,   "Host unreachable for TOS" },
  { ICMP_PKT_FILTERED,   "Communication administratively filtered" },
  { ICMP_PREC_VIOLATION, "Host precedence violation" },
  { ICMP_PREC_CUTOFF,    "Precedence cutoff in effect" },
  { 0, NULL }
};

static const value_string redir_code_str[] = {
  { 0, "Redirect for network" },
  { 1, "Redirect for host" },
  { 2, "Redirect for TOS and network" },
  { 3, "Redirect for TOS and host"},
  { 0, NULL }
};

static const value_string alt_host_code_str[] = {
  { 0, "Alternate address for host" },
  { 0, NULL }
};

static const value_string rtradvert_code_str[] = {
  { 0,  "Normal router advertisement" },
  { 16, "Does not route common traffic" },
  { 0, NULL }
};

static const value_string ttl_code_str[] = {
  { 0, "Time to live exceeded in transit" },
  { 1, "Fragment reassembly time exceeded" },
  { 0, NULL }
};

static const value_string par_code_str[] = {
  { 0, "Pointer indicates the error" },
  { 1, "Required option missing" },
  { 2, "Bad length" },
  { 0, NULL }
};

static const value_string photuris_code_str[] = {
  { 0, "Bad SPI" },
  { 1, "Authentication Failed" },
  { 2, "Decompression Failed" },
  { 3, "Decryption Failed" },
  { 4, "Need Authentication" },
  { 5, "Need Authorization" },
  { 0, NULL }
};

static const value_string mip_extensions[] = {
  { ICMP_MIP_EXTENSION_PAD, "One byte padding extension"},  /* RFC 2002 */
  { ICMP_MIP_MOB_AGENT_ADV, "Mobility Agent Advertisement Extension"},
							    /* RFC 2002 */
  { ICMP_MIP_PREFIX_LENGTHS, "Prefix Lengths Extension"},   /* RFC 2002 */
  { ICMP_MIP_CHALLENGE, "Challenge Extension"},             /* RFC 3012 */
  { 0, NULL}
};

#define MPLS_STACK_ENTRY_OBJECT_CLASS           1
#define MPLS_EXTENDED_PAYLOAD_OBJECT_CLASS      2

#define MPLS_STACK_ENTRY_C_TYPE                 1
#define MPLS_EXTENDED_PAYLOAD_C_TYPE            1

/* XXX no header defines these macros ??? */
#ifndef min
#define min(a,b) (((a)<(b))?(a):(b))
#endif

#ifndef max
#define max(a,b) (((a)>(b))?(a):(b))
#endif

/*
 * Dissect the mobile ip advertisement extensions.
 */
static void
dissect_mip_extensions(tvbuff_t *tvb, int offset, proto_tree *tree)
{
  guint8       type;
  guint8       length;
  guint16      flags;
  proto_item   *ti;
  proto_tree   *mip_tree=NULL;
  proto_tree   *flags_tree=NULL;
  gint         numCOAs;
  gint         i;

  /* Not much to do if we're not parsing everything */
  if (!tree) return;

  while (tvb_reported_length_remaining(tvb, offset) > 0) {

	type = tvb_get_guint8(tvb, offset + 0);
	if (type)
	  length = tvb_get_guint8(tvb, offset + 1);
	else
	  length=0;

	ti = proto_tree_add_text(tree, tvb, offset,
							 type?(length + 2):1,
							 "Ext: %s",
							 val_to_str(type, mip_extensions,
										"Unknown ext %u"));
	mip_tree = proto_item_add_subtree(ti, ett_icmp_mip);


	switch (type) {
	case ICMP_MIP_EXTENSION_PAD:
	  /* One byte padding extension */
	  /* Add our fields */
	  /* type */
	  proto_tree_add_item(mip_tree, hf_icmp_mip_type, tvb, offset,
						  1, FALSE);
	  offset++;
	  break;
	case ICMP_MIP_MOB_AGENT_ADV:
	  /* Mobility Agent Advertisement Extension (RFC 2002)*/
	  /* Add our fields */
	  /* type */
	  proto_tree_add_item(mip_tree, hf_icmp_mip_type, tvb, offset,
						  1, FALSE);
	  offset++;
	  /* length */
	  proto_tree_add_item(mip_tree, hf_icmp_mip_length, tvb, offset,
						  1, FALSE);
	  offset++;
	  /* sequence number */
	  proto_tree_add_item(mip_tree, hf_icmp_mip_seq, tvb, offset,
						  2, FALSE);
	  offset+=2;
	  /* Registration Lifetime */
	  proto_tree_add_item(mip_tree, hf_icmp_mip_life, tvb, offset,
						  2, FALSE);
	  offset+=2;
	  /* flags */
	  flags = tvb_get_ntohs(tvb, offset);
	  ti = proto_tree_add_uint(mip_tree, hf_icmp_mip_flags, tvb, offset, 2, flags);
	  flags_tree = proto_item_add_subtree(ti, ett_icmp_mip_flags);
	  proto_tree_add_boolean(flags_tree, hf_icmp_mip_r, tvb, offset, 2, flags);
	  proto_tree_add_boolean(flags_tree, hf_icmp_mip_b, tvb, offset, 2, flags);
	  proto_tree_add_boolean(flags_tree, hf_icmp_mip_h, tvb, offset, 2, flags);
	  proto_tree_add_boolean(flags_tree, hf_icmp_mip_f, tvb, offset, 2, flags);
	  proto_tree_add_boolean(flags_tree, hf_icmp_mip_m, tvb, offset, 2, flags);
	  proto_tree_add_boolean(flags_tree, hf_icmp_mip_g, tvb, offset, 2, flags);
	  proto_tree_add_boolean(flags_tree, hf_icmp_mip_v, tvb, offset, 2, flags);
	  proto_tree_add_boolean(flags_tree, hf_icmp_mip_rt, tvb, offset, 2, flags);
	  proto_tree_add_boolean(flags_tree, hf_icmp_mip_u, tvb, offset, 2, flags);
	  proto_tree_add_boolean(flags_tree, hf_icmp_mip_x, tvb, offset, 2, flags);

	  /* Reserved */
	  proto_tree_add_uint(flags_tree, hf_icmp_mip_reserved, tvb, offset, 2, flags);
	  offset+=2;

	  /* COAs */
	  numCOAs = (length - 6) / 4;
	  for (i=0; i<numCOAs; i++) {
		proto_tree_add_item(mip_tree, hf_icmp_mip_coa, tvb, offset,
							4, FALSE);
		offset+=4;
	  }
	  break;
	case ICMP_MIP_PREFIX_LENGTHS:
	  /* Prefix-Lengths Extension  (RFC 2002)*/
	  /* Add our fields */
	  /* type */
	  proto_tree_add_item(mip_tree, hf_icmp_mip_type, tvb, offset,
						  1, FALSE);
	  offset++;
	  /* length */
	  proto_tree_add_item(mip_tree, hf_icmp_mip_length, tvb, offset,
						  1, FALSE);
	  offset++;

	  /* prefix lengths */
	  for(i=0; i<length; i++) {
		proto_tree_add_item(mip_tree, hf_icmp_mip_prefix_length, tvb, offset,
							1, FALSE);
		offset++;
	  }
	  break;
	case ICMP_MIP_CHALLENGE:
	  /* Challenge Extension  (RFC 3012)*/
	  /* type */
	  proto_tree_add_item(mip_tree, hf_icmp_mip_type, tvb, offset,
						  1, FALSE);
	  offset++;
	  /* length */
	  proto_tree_add_item(mip_tree, hf_icmp_mip_length, tvb, offset,
						  1, FALSE);
	  offset++;
	  /* challenge */
	  proto_tree_add_item(mip_tree, hf_icmp_mip_challenge, tvb, offset,
						  length, FALSE);
	  offset+=length;

	  break;
	default:
	  g_warning("Unknown type(%u)!  I hope the length is right (%u)",
				type, length);
	  offset += length + 2;
	  break;
	} /* switch type */
  } /* end while */

} /* dissect_mip_extensions */

/*
 * Dissect the MPLS extensions
 */
static void
dissect_mpls_extensions(tvbuff_t *tvb, gint offset, proto_tree *tree)
{
    guint8          version;
    guint8          class_num;
    guint8          c_type;
    guint8          ttl;
    guint8          tmp;
    guint16         reserved;
    guint16         cksum, computed_cksum;
    guint16         obj_length, obj_trunc_length;
    proto_item      *ti, *tf_object, *tf_entry, *hidden_item;
    proto_tree      *mpls_tree=NULL, *mpls_object_tree, *mpls_stack_object_tree;
    gint            obj_end_offset;
    guint           reported_length;
    guint           label;
    gboolean        unknown_object;

    if (!tree)
        return;

    reported_length = tvb_reported_length_remaining(tvb, offset);

    if (reported_length < 4 /* Common header */)
    {
        proto_tree_add_text(tree, tvb, offset,
                            reported_length,
                            "MPLS Extensions (truncated)");
        return;
    }

    /* Add a tree for the MPLS extensions */
    ti = proto_tree_add_none_format(tree, hf_icmp_mpls, tvb,
                                            offset, reported_length, "MPLS Extensions");

    mpls_tree = proto_item_add_subtree(ti, ett_icmp_mpls);

    /* Version */
    version = hi_nibble(tvb_get_guint8(tvb, offset));
    proto_tree_add_uint(mpls_tree, hf_icmp_mpls_version, tvb, offset, 1, version);

    /* Reserved */
    reserved = tvb_get_ntohs(tvb, offset) & 0x0fff;
    proto_tree_add_uint_format(mpls_tree, hf_icmp_mpls_reserved,
                                tvb, offset, 2, reserved,
                                "Reserved: 0x%03x", reserved);

    /* Checksum */
    cksum = tvb_get_ntohs(tvb, offset + 2);

    computed_cksum = ip_checksum(tvb_get_ptr(tvb, offset, reported_length),
                                    reported_length);

    if (computed_cksum == 0)
    {
        proto_tree_add_uint_format(mpls_tree, hf_icmp_mpls_checksum, tvb, offset + 2, 2,
                                    cksum, "Checksum: 0x%04x [correct]", cksum);
    }
    else
    {
        hidden_item = proto_tree_add_boolean(mpls_tree, hf_icmp_mpls_checksum_bad, tvb,
                                            offset + 2, 2, TRUE);
        PROTO_ITEM_SET_HIDDEN(hidden_item);

        proto_tree_add_uint_format(mpls_tree, hf_icmp_mpls_checksum, tvb, offset + 2, 2,
                                    cksum,
                                    "Checksum: 0x%04x [incorrect, should be 0x%04x]",
                                    cksum, in_cksum_shouldbe(cksum, computed_cksum));
    }

    if (version != 1 && version != 2)
    {
        /* Unsupported version */
        proto_item_append_text(ti, " (unsupported version)");
        return;
    }

    /* Skip the common header */
    offset += 4;

    /* While there is enough room to read an object */
    while (tvb_reported_length_remaining(tvb, offset) >= 4 /* Object header */)
    {
        /* Object length */
        obj_length = tvb_get_ntohs(tvb, offset);

        obj_trunc_length =  min(obj_length, tvb_reported_length_remaining(tvb, offset));

        obj_end_offset = offset + obj_trunc_length;

        /* Add a subtree for this object (the text will be reset later) */
        tf_object = proto_tree_add_text(mpls_tree, tvb, offset,
                                        max(obj_trunc_length, 4),
                                        "Unknown object");

        mpls_object_tree = proto_item_add_subtree(tf_object, ett_icmp_mpls_object);

        proto_tree_add_uint(mpls_object_tree, hf_icmp_mpls_length, tvb, offset, 2, obj_length);

        /* Class */
        class_num = tvb_get_guint8(tvb, offset + 2);
        proto_tree_add_uint(mpls_object_tree, hf_icmp_mpls_class, tvb, offset + 2, 1, class_num);

        /* C-Type */
        c_type = tvb_get_guint8(tvb, offset + 3);
        proto_tree_add_uint(mpls_object_tree, hf_icmp_mpls_c_type, tvb, offset + 3, 1, c_type);

        if (obj_length < 4 /* Object header */)
        {
            /* Thanks doc/README.developer :)) */
            proto_item_set_text(tf_object, "Object with bad length");
            break;
        }

        /* Skip the object header */
        offset += 4;

        /* Default cases will set this flag to TRUE */
        unknown_object = FALSE;

        switch (class_num)
        {
            case MPLS_STACK_ENTRY_OBJECT_CLASS:
                switch (c_type)
                {
                    case MPLS_STACK_ENTRY_C_TYPE:

                        proto_item_set_text(tf_object, "MPLS Stack Entry");

                        /* For each entry */
                        while (offset + 4 <= obj_end_offset)
                        {
                            if (tvb_reported_length_remaining(tvb, offset) < 4)
                            {
                                /* Not enough room in the packet ! */
                                break;
                            }

                            /* Create a subtree for each entry (the text will be set later) */
                            tf_entry = proto_tree_add_text(mpls_object_tree,
                                                            tvb, offset, 4, " ");
                            mpls_stack_object_tree = proto_item_add_subtree(tf_entry,
                                                                            ett_icmp_mpls_stack_object);

                            /* Label */
                            label =  (guint)tvb_get_ntohs(tvb, offset);
                            tmp = tvb_get_guint8(tvb, offset + 2);
                            label = (label << 4) + (tmp >> 4);

                            proto_tree_add_uint(mpls_stack_object_tree,
                                                    hf_icmp_mpls_label,
                                                    tvb,
                                                    offset,
                                                    3,
                                                    label << 4);

                            proto_item_set_text(tf_entry, "Label: %u", label);

                            /* Experimental field (also called "CoS") */
                            proto_tree_add_uint(mpls_stack_object_tree,
                                                    hf_icmp_mpls_exp,
                                                    tvb,
                                                    offset + 2,
                                                    1,
                                                    tmp);

                            proto_item_append_text(tf_entry, ", Exp: %u", (tmp >> 1) & 0x07);

                            /* Stack bit */
                            proto_tree_add_boolean(mpls_stack_object_tree,
                                                    hf_icmp_mpls_s,
                                                    tvb,
                                                    offset + 2,
                                                    1,
                                                    tmp);

                            proto_item_append_text(tf_entry, ", S: %u", tmp  & 0x01);

                            /* TTL */
                            ttl = tvb_get_guint8(tvb, offset + 3);

                            proto_tree_add_item(mpls_stack_object_tree,
                                                hf_icmp_mpls_ttl,
                                                tvb,
                                                offset + 3,
                                                1,
                                                FALSE);

                            proto_item_append_text(tf_entry, ", TTL: %u", ttl);

                            /* Skip the entry */
                            offset += 4;

                        } /* end while */

                        if (offset < obj_end_offset)
                            proto_tree_add_text(mpls_object_tree, tvb,
                                                offset,
                                                obj_end_offset - offset,
                                                "%d junk bytes",
                                                obj_end_offset - offset);

                        break;
                    default:

                        unknown_object = TRUE;

                        break;
                } /* end switch c_type */
                break;
            case MPLS_EXTENDED_PAYLOAD_OBJECT_CLASS:
                switch (c_type)
                {
                    case MPLS_EXTENDED_PAYLOAD_C_TYPE:
                        proto_item_set_text(tf_object, "Extended Payload");

                        /* This object contains some portion of the original packet
                        that could not fit in the 128 bytes of the ICMP payload */
                        if (obj_trunc_length > 4)
                            proto_tree_add_text(mpls_object_tree, tvb,
                                                offset, obj_trunc_length - 4,
                                                "Data (%d bytes)", obj_trunc_length - 4);

                        break;
                    default:

                        unknown_object = TRUE;

                        break;
                } /* end switch c_type */
                break;
            default:

                unknown_object = TRUE;

                break;
        } /* end switch class_num */

        /* The switches couldn't decode the object */
        if (unknown_object == TRUE)
        {
            proto_item_set_text(tf_object, "Unknown object (%d/%d)", class_num, c_type);

            if (obj_trunc_length > 4)
                proto_tree_add_text(mpls_object_tree, tvb,
                                    offset, obj_trunc_length - 4,
                                    "Data (%d bytes)", obj_trunc_length - 4);
        }

        /* */
        if (obj_trunc_length < obj_length)
            proto_item_append_text(tf_object, " (truncated)");

        /* Go to the end of the object */
        offset = obj_end_offset;

    } /* end while */
} /* end dissect_mpls_extensions */

/*
 * RFC 792 for basic ICMP.
 * RFC 1191 for ICMP_FRAG_NEEDED (with MTU of next hop).
 * RFC 1256 for router discovery messages.
 * RFC 2002 and 3012 for Mobile IP stuff.
 */
static void
dissect_icmp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
  proto_tree *icmp_tree = NULL;
  proto_item *ti;
  guint8     icmp_type;
  guint8     icmp_code;
  guint      length, reported_length;
  guint16    cksum, computed_cksum;
  const gchar *type_str, *code_str;
  guint8     num_addrs = 0;
  guint8     addr_entry_size = 0;
  int        i;
  gboolean   save_in_error_pkt;
  tvbuff_t   *next_tvb;
  proto_item *item;

  col_set_str(pinfo->cinfo, COL_PROTOCOL, "ICMP");
  col_clear(pinfo->cinfo, COL_INFO);

  /* To do: check for runts, errs, etc. */
  icmp_type = tvb_get_guint8(tvb, 0);
  icmp_code = tvb_get_guint8(tvb, 1);
  cksum = tvb_get_ntohs(tvb, 2);

  type_str = val_to_str_const (icmp_type, icmp_type_str, "Unknown ICMP (obsolete or malformed?)");

  switch (icmp_type) {
    case ICMP_UNREACH:
      code_str = val_to_str (icmp_code, unreach_code_str, "Unknown code: %u");
      break;
    case ICMP_REDIRECT:
      code_str = val_to_str (icmp_code, redir_code_str, "Unknown code: %u");
      break;
    case ICMP_ALTHOST:
      code_str = val_to_str (icmp_code, alt_host_code_str, "Unknown code: %u");
      break;
    case ICMP_RTRADVERT:
      switch (icmp_code) {
      case 0: /* Mobile-Ip */
      case 16: /* Mobile-Ip */
        type_str = "Mobile IP Advertisement";
        break;
      } /* switch icmp_code */
      code_str = val_to_str (icmp_code, rtradvert_code_str, "Unknown code: %u");
      break;
    case ICMP_TIMXCEED:
      code_str = val_to_str (icmp_code, ttl_code_str, "Unknown code: %u");
      break;
    case ICMP_PARAMPROB:
      code_str = val_to_str (icmp_code, par_code_str, "Unknown code: %u");
      break;
    case ICMP_PHOTURIS:
      code_str = val_to_str (icmp_code, photuris_code_str, "Unknown code: %u");
      break;
    default:
      code_str = NULL;
      break;
  }

  col_set_str(pinfo->cinfo, COL_INFO, type_str);
  if (code_str)
    col_append_fstr(pinfo->cinfo, COL_INFO, " (%s)", code_str);

  length = tvb_length(tvb);
  reported_length = tvb_reported_length(tvb);

  ti = proto_tree_add_item(tree, proto_icmp, tvb, 0, length, FALSE);
  icmp_tree = proto_item_add_subtree(ti, ett_icmp);

  ti = proto_tree_add_item(icmp_tree, hf_icmp_type, tvb, 0, 1, FALSE);
  proto_item_append_text (ti, " (%s)", type_str);

  ti = proto_tree_add_item(icmp_tree, hf_icmp_code, tvb, 1, 1, FALSE);
  if (code_str)
    proto_item_append_text (ti, " (%s)", code_str);

  if (!pinfo->fragmented && length >= reported_length) {
    /* The packet isn't part of a fragmented datagram and isn't
       truncated, so we can checksum it. */

    computed_cksum = ip_checksum(tvb_get_ptr(tvb, 0, reported_length),
				 reported_length);
    if (computed_cksum == 0) {
      proto_tree_add_uint_format(icmp_tree, hf_icmp_checksum, tvb, 2, 2,
				 cksum,
				 "Checksum: 0x%04x [correct]", cksum);
    } else {
      item = proto_tree_add_boolean(icmp_tree, hf_icmp_checksum_bad,
				    tvb, 2, 2, TRUE);
      PROTO_ITEM_SET_HIDDEN(item);
      proto_tree_add_uint_format(icmp_tree, hf_icmp_checksum, tvb, 2, 2,
				 cksum,
				 "Checksum: 0x%04x [incorrect, should be 0x%04x]",
				 cksum, in_cksum_shouldbe(cksum, computed_cksum));
    }
  } else {
    proto_tree_add_uint(icmp_tree, hf_icmp_checksum, tvb, 2, 2, cksum);
  }

  /* Decode the second 4 bytes of the packet. */
  switch (icmp_type) {
      case ICMP_ECHOREPLY:
      case ICMP_ECHO:
      case ICMP_TSTAMP:
      case ICMP_TSTAMPREPLY:
      case ICMP_IREQ:
      case ICMP_IREQREPLY:
      case ICMP_MASKREQ:
      case ICMP_MASKREPLY:
        proto_tree_add_item(icmp_tree, hf_icmp_ident, tvb, 4, 2, FALSE);
        proto_tree_add_item(icmp_tree, hf_icmp_seq_num, tvb, 6, 2, FALSE);
	break;

      case ICMP_UNREACH:
        switch (icmp_code) {
          case ICMP_FRAG_NEEDED:
            proto_tree_add_item(icmp_tree, hf_icmp_mtu, tvb, 6, 2, FALSE);
            break;
	}
        break;

      case ICMP_RTRADVERT:
        num_addrs = tvb_get_guint8(tvb, 4);
	proto_tree_add_text(icmp_tree, tvb, 4, 1, "Number of addresses: %u",
	  num_addrs);
	addr_entry_size = tvb_get_guint8(tvb, 5);
	proto_tree_add_text(icmp_tree, tvb, 5, 1, "Address entry size: %u",
	  addr_entry_size);
	proto_tree_add_text(icmp_tree, tvb, 6, 2, "Lifetime: %s",
	  time_secs_to_str(tvb_get_ntohs(tvb, 6)));
	break;

      case ICMP_PARAMPROB:
	proto_tree_add_text(icmp_tree, tvb, 4, 1, "Pointer: %u",
	  tvb_get_guint8(tvb, 4));
	break;

      case ICMP_REDIRECT:
        proto_tree_add_item(icmp_tree, hf_icmp_redir_gw, tvb, 4, 4, FALSE);
	break;
  }

  /* Decode the additional information in the packet.  */
  switch (icmp_type) {
      case ICMP_UNREACH:
      case ICMP_TIMXCEED:
      case ICMP_PARAMPROB:
      case ICMP_SOURCEQUENCH:
      case ICMP_REDIRECT:
	/* Save the current value of the "we're inside an error packet"
	   flag, and set that flag; subdissectors may treat packets
	   that are the payload of error packets differently from
	   "real" packets. */
	save_in_error_pkt = pinfo->in_error_pkt;
	pinfo->in_error_pkt = TRUE;

	/* Decode the IP header and first 64 bits of data from the
	   original datagram. */
	next_tvb = tvb_new_subset_remaining(tvb, 8);

	/* There is a collision between RFC 1812 and draft-ietf-mpls-icmp-02.
	We don't know how to decode the 128th and following bytes of the ICMP payload.
	According to draft-ietf-mpls-icmp-02, these bytes should be decoded as MPLS extensions
	whereas RFC 1812 tells us to decode them as a portion of the original packet.
	Let the user decide.

	Here the user decided to favor MPLS extensions.
	Force the IP dissector to decode only the first 128 bytes. */
	if ((tvb_reported_length(tvb) > 8 + 128) &&
			favor_icmp_mpls_ext && (tvb_get_ntohs(tvb, 8 + 2) > 128))
		set_actual_length(next_tvb, 128);

	call_dissector(ip_handle, next_tvb, pinfo, icmp_tree);

	/* Restore the "we're inside an error packet" flag. */
	pinfo->in_error_pkt = save_in_error_pkt;

	/* Decode MPLS extensions if the payload has at least 128 bytes, and
		- the original packet in the ICMP payload has less than 128 bytes, or
		- the user favors the MPLS extensions analysis */
	if ((tvb_reported_length(tvb) > 8 + 128)
			&& (tvb_get_ntohs(tvb, 8 + 2) <= 128 || favor_icmp_mpls_ext))
		dissect_mpls_extensions(tvb, 8 + 128, icmp_tree);

	break;

      case ICMP_ECHOREPLY:
      case ICMP_ECHO:
	call_dissector(data_handle, tvb_new_subset_remaining(tvb, 8), pinfo,
	               icmp_tree);
	break;

      case ICMP_RTRADVERT:
        if (addr_entry_size == 2) {
	  for (i = 0; i < num_addrs; i++) {
	    proto_tree_add_text(icmp_tree, tvb, 8 + (i*8), 4,
	      "Router address: %s",
	      ip_to_str(tvb_get_ptr(tvb, 8 + (i*8), 4)));
	    proto_tree_add_text(icmp_tree, tvb, 12 + (i*8), 4,
	      "Preference level: %d", tvb_get_ntohl(tvb, 12 + (i*8)));
	  }
	  if ((icmp_code == 0) || (icmp_code == 16)) {
		/* Mobile-Ip */
		dissect_mip_extensions(tvb, 8 + i*8, icmp_tree);
	  }
	} else
	  call_dissector(data_handle, tvb_new_subset_remaining(tvb, 8), pinfo,
	                 icmp_tree);
	break;

      case ICMP_TSTAMP:
      case ICMP_TSTAMPREPLY:
	proto_tree_add_text(icmp_tree, tvb, 8, 4, "Originate timestamp: %s after midnight UTC",
	  time_msecs_to_str(tvb_get_ntohl(tvb, 8)));
	proto_tree_add_text(icmp_tree, tvb, 12, 4, "Receive timestamp: %s after midnight UTC",
	  time_msecs_to_str(tvb_get_ntohl(tvb, 12)));
	proto_tree_add_text(icmp_tree, tvb, 16, 4, "Transmit timestamp: %s after midnight UTC",
	  time_msecs_to_str(tvb_get_ntohl(tvb, 16)));
	break;

    case ICMP_MASKREQ:
    case ICMP_MASKREPLY:
	proto_tree_add_text(icmp_tree, tvb, 8, 4, "Address mask: %s (0x%08x)",
	  ip_to_str(tvb_get_ptr(tvb, 8, 4)), tvb_get_ntohl(tvb, 8));
	break;
  }
}

void
proto_register_icmp(void)
{
  static hf_register_info hf[] = {

    { &hf_icmp_type,
      { "Type",         "icmp.type",            FT_UINT8, BASE_DEC,     NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_code,
      { "Code",         "icmp.code",            FT_UINT8, BASE_DEC,     NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_checksum,
      { "Checksum",     "icmp.checksum",        FT_UINT16, BASE_HEX,    NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_checksum_bad,
      { "Bad Checksum", "icmp.checksum_bad",    FT_BOOLEAN, BASE_NONE,  NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_ident,
      { "Identifier", "icmp.ident",              FT_UINT16, BASE_HEX,    NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_seq_num,
      { "Sequence number", "icmp.seq",           FT_UINT16, BASE_DEC_HEX,    NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_mtu,
      { "MTU of next hop", "icmp.mtu",           FT_UINT16, BASE_DEC,    NULL, 0x0,
        NULL, HFILL}},

    { &hf_icmp_redir_gw,
      { "Gateway address", "icmp.redir_gw",      FT_IPv4, BASE_NONE,     NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_mip_type,
      { "Extension Type", "icmp.mip.type",      FT_UINT8, BASE_DEC,
        VALS(mip_extensions), 0x0,NULL, HFILL}},

    { &hf_icmp_mip_length,
      { "Length", "icmp.mip.length",            FT_UINT8, BASE_DEC, NULL, 0x0,
        NULL, HFILL}},

    { &hf_icmp_mip_prefix_length,
      { "Prefix Length", "icmp.mip.prefixlength",  FT_UINT8, BASE_DEC, NULL, 0x0,
        NULL, HFILL}},

    { &hf_icmp_mip_seq,
      { "Sequence Number", "icmp.mip.seq",      FT_UINT16, BASE_DEC, NULL, 0x0,
        NULL, HFILL}},

    { &hf_icmp_mip_life,
      { "Registration Lifetime", "icmp.mip.life",  FT_UINT16, BASE_DEC, NULL, 0x0,
        NULL, HFILL}},

    { &hf_icmp_mip_flags,
      { "Flags", "icmp.mip.flags",            FT_UINT16, BASE_HEX, NULL, 0x0,
        NULL, HFILL}},

    { &hf_icmp_mip_r,
      { "Registration Required", "icmp.mip.r", FT_BOOLEAN, 16, NULL, 0x8000,
        "Registration with this FA is required", HFILL }},

    { &hf_icmp_mip_b,
      { "Busy", "icmp.mip.b", FT_BOOLEAN, 16, NULL, 0x4000,
        "This FA will not accept requests at this time", HFILL }},

    { &hf_icmp_mip_h,
      { "Home Agent", "icmp.mip.h", FT_BOOLEAN, 16, NULL, 0x2000,
        "Home Agent Services Offered", HFILL }},

    { &hf_icmp_mip_f,
      { "Foreign Agent", "icmp.mip.f", FT_BOOLEAN, 16, NULL, 0x1000,
        "Foreign Agent Services Offered", HFILL }},

    { &hf_icmp_mip_m,
      { "Minimal Encapsulation", "icmp.mip.m", FT_BOOLEAN, 16, NULL, 0x0800,
        "Minimal encapsulation tunneled datagram support", HFILL }},

    { &hf_icmp_mip_g,
      { "GRE", "icmp.mip.g", FT_BOOLEAN, 16, NULL, 0x0400,
        "GRE encapsulated tunneled datagram support", HFILL }},

    { &hf_icmp_mip_v,
      { "VJ Comp", "icmp.mip.v", FT_BOOLEAN, 16, NULL, 0x0200,
        "Van Jacobson Header Compression Support", HFILL }},

    { &hf_icmp_mip_rt,
      { "Reverse tunneling", "icmp.mip.rt", FT_BOOLEAN, 16, NULL, 0x0100,
       "Reverse tunneling support", HFILL }},

    { &hf_icmp_mip_u,
      { "UDP tunneling", "icmp.mip.u", FT_BOOLEAN, 16, NULL, 0x0080,
       "UDP tunneling support", HFILL }},

    { &hf_icmp_mip_x,
      { "Revocation support", "icmp.mip.x", FT_BOOLEAN, 16, NULL, 0x0040,
       "Registration revocation support", HFILL }},


    { &hf_icmp_mip_reserved,
      { "Reserved", "icmp.mip.reserved",     FT_UINT16, BASE_HEX, NULL, 0x003f,
        NULL, HFILL}},

    { &hf_icmp_mip_coa,
      { "Care-Of-Address", "icmp.mip.coa",    FT_IPv4, BASE_NONE, NULL, 0x0,
        NULL, HFILL}},

    { &hf_icmp_mip_challenge,
      { "Challenge", "icmp.mip.challenge",    FT_BYTES, BASE_NONE, NULL, 0x0,
        NULL, HFILL}},

    { &hf_icmp_mpls,
      { "ICMP Extensions for MPLS",     "icmp.mpls",    FT_NONE, BASE_NONE,     NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_mpls_version,
      { "Version",              "icmp.mpls.version", FT_UINT8, BASE_DEC, NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_mpls_reserved,
      { "Reserved",     "icmp.mpls.res",        FT_UINT16, BASE_HEX,    NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_mpls_checksum,
      { "Checksum",     "icmp.mpls.checksum",   FT_UINT16, BASE_HEX,    NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_mpls_checksum_bad,
      { "Bad Checksum", "icmp.mpls.checksum_bad",       FT_BOOLEAN, BASE_NONE,  NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_mpls_length,
      { "Length",       "icmp.mpls.length",     FT_UINT16, BASE_HEX,    NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_mpls_class,
      { "Class",        "icmp.mpls.class", FT_UINT8, BASE_DEC, NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_mpls_c_type,
      { "C-Type",       "icmp.mpls.ctype", FT_UINT8, BASE_DEC, NULL, 0x0,
        NULL, HFILL }},

    { &hf_icmp_mpls_label,
      { "Label",        "icmp.mpls.label", FT_UINT24, BASE_DEC, NULL, 0x00fffff0,
        NULL, HFILL }},

    { &hf_icmp_mpls_exp,
      { "Experimental", "icmp.mpls.exp", FT_UINT24, BASE_DEC, NULL, 0x0e,
        NULL, HFILL }},

    { &hf_icmp_mpls_s,
      { "Stack bit",    "icmp.mpls.s", FT_BOOLEAN, 24, TFS(&tfs_set_notset), 0x01,
        NULL, HFILL }},

    { &hf_icmp_mpls_ttl,
      { "Time to live", "icmp.mpls.ttl", FT_UINT8, BASE_DEC, NULL, 0x0,
        NULL, HFILL }}
  };

  static gint *ett[] = {
    &ett_icmp,
    &ett_icmp_mip,
    &ett_icmp_mip_flags,
    /* MPLS extensions */
    &ett_icmp_mpls,
    &ett_icmp_mpls_object,
    &ett_icmp_mpls_stack_object
  };

  module_t *icmp_module;

  proto_icmp = proto_register_protocol("Internet Control Message Protocol",
				       "ICMP", "icmp");
  proto_register_field_array(proto_icmp, hf, array_length(hf));
  proto_register_subtree_array(ett, array_length(ett));

  icmp_module = prefs_register_protocol(proto_icmp, NULL);

  prefs_register_bool_preference(icmp_module, "favor_icmp_mpls",
	    "Favor ICMP extensions for MPLS",
	    "Whether the 128th and following bytes of the ICMP payload should be decoded as MPLS extensions or as a portion of the original packet",
	    &favor_icmp_mpls_ext);

  register_dissector("icmp", dissect_icmp, proto_icmp);
}

void
proto_reg_handoff_icmp(void)
{
  dissector_handle_t icmp_handle;

  /*
   * Get handle for the IP dissector.
   */
  ip_handle = find_dissector("ip");
  icmp_handle = find_dissector("icmp");
  data_handle = find_dissector("data");

  dissector_add("ip.proto", IP_PROTO_ICMP, icmp_handle);
}