/* packet-fr.c
 * Routines for Frame Relay  dissection
 *
 * Copyright 2001, Paul Ionescu	<paul@acorp.ro>
 *
 * $Id: packet-fr.c 32410 2010-04-06 21:14:01Z wmeier $
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * 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.
 *
 * References:
 *
 * http://www.protocols.com/pbook/frame.htm
 * http://www.mplsforum.org/frame/Approved/FRF.3/FRF.3.2.pdf
 * ITU Recommendations Q.922 and Q.933
 * RFC-1490
 * RFC-2427
 * Cisco encapsulation
 * http://www.trillium.com/assets/legacyframe/white_paper/8771019.pdf
 */

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

#include <stdlib.h>
#include <ctype.h>

#include <glib.h>
#include <epan/packet.h>
#include <epan/prefs.h>
#include "packet-llc.h"
#include "packet-chdlc.h"
#include "packet-eth.h"
#include "packet-ip.h"
#include "packet-ipv6.h"
#include "packet-ppp.h"
#include "packet-fr.h"
#include <epan/xdlc.h>
#include <epan/etypes.h>
#include <epan/oui.h>
#include <epan/nlpid.h>
#include <epan/greproto.h>

/*
 * Bits in the address field.
 */
#define FRELAY_EA		0x01	/* Address field extension bit */

#define FRELAY_UPPER_DLCI	0xFC	/* Upper DLCI */
#define FRELAY_CR		0x02	/* Command/response bit in first octet */

#define FRELAY_SECOND_DLCI	0xF0	/* DLCI bits in FECN/BECN/DE octet */
#define FRELAY_FECN		0x08	/* Forward Explicit Congestion Notification */
#define FRELAY_BECN		0x04	/* Backward Explicit Congestion Notification */
#define FRELAY_DE		0x02	/* Discard Eligibility */

#define FRELAY_THIRD_DLCI	0xFE	/* DLCI bits in third octet, if any */

#define FRELAY_LOWER_DLCI	0xFC	/* Lower DLCI */
#define FRELAY_DC		0x02	/* DLCI or DL-CORE control indicator in last octet */

#define FROM_DCE	0x80		/* for direction setting */

static gint proto_fr    = -1;
static gint ett_fr      = -1;
static gint ett_fr_address = -1;
static gint ett_fr_control = -1;
static gint hf_fr_ea    = -1;
static gint hf_fr_upper_dlci = -1;
static gint hf_fr_cr	= -1;
static gint hf_fr_second_dlci = -1;
static gint hf_fr_fecn  = -1;
static gint hf_fr_becn  = -1;
static gint hf_fr_de    = -1;
static gint hf_fr_third_dlci = -1;
static gint hf_fr_dlcore_control = -1;
static gint hf_fr_lower_dlci = -1;
static gint hf_fr_dc    = -1;
static gint hf_fr_dlci  = -1;
static gint hf_fr_control = -1;
static gint hf_fr_n_r = -1;
static gint hf_fr_n_s = -1;
static gint hf_fr_p = -1;
static gint hf_fr_p_ext = -1;
static gint hf_fr_f = -1;
static gint hf_fr_f_ext = -1;
static gint hf_fr_s_ftype = -1;
static gint hf_fr_u_modifier_cmd = -1;
static gint hf_fr_u_modifier_resp = -1;
static gint hf_fr_ftype_i = -1;
static gint hf_fr_ftype_s_u = -1;
static gint hf_fr_ftype_s_u_ext = -1;
static gint hf_fr_nlpid = -1;
static gint hf_fr_oui   = -1;
static gint hf_fr_pid   = -1;
static gint hf_fr_snaptype = -1;
static gint hf_fr_chdlctype = -1;

static dissector_handle_t eth_withfcs_handle;
static dissector_handle_t gprs_ns_handle;
static dissector_handle_t data_handle;

static dissector_table_t osinl_subdissector_table;

/*
 * Encapsulation type.
 * XXX - this should be per-DLCI as well.
 */
#define FRF_3_2		0	/* FRF 3.2 or Cisco HDLC */
#define GPRS_NS		1	/* GPRS Network Services (3GPP TS 08.16) */
#define RAW_ETHER	2	/* Raw Ethernet */

static gint fr_encap = FRF_3_2;

static const true_false_string ctrl_string = {
                "DLCI Address",
                "Control"
        };
static const true_false_string ea_string = {
                "Last Octet",
                "More Follows"
        };

/*
 * This isn't the same as "nlpid_vals[]"; 0x08 is Q.933, not Q.931,
 * and 0x09 is LMI, not Q.2931, and we assume that it's an initial
 * protocol identifier, so 0x01 is T.70, not X.29.
 */
static const value_string fr_nlpid_vals[] = {
	{ NLPID_NULL,            "NULL" },
	{ NLPID_IPI_T_70,        "T.70" },	/* XXX - IPI, or SPI? */
	{ NLPID_X_633,           "X.633" },
	{ NLPID_Q_931,           "Q.933" },
	{ NLPID_LMI,             "LMI" },
	{ NLPID_Q_2119,          "Q.2119" },
	{ NLPID_SNAP,            "SNAP" },
	{ NLPID_ISO8473_CLNP,    "CLNP" },
	{ NLPID_ISO9542_ESIS,    "ESIS" },
	{ NLPID_ISO10589_ISIS,   "ISIS" },
	{ NLPID_ISO10747_IDRP,   "IDRP" },
	{ NLPID_ISO9542X25_ESIS, "ESIS (X.25)" },
	{ NLPID_ISO10030,        "ISO 10030" },
	{ NLPID_ISO11577,        "ISO 11577" },
	{ NLPID_COMPRESSED,      "Data compression protocol" },
	{ NLPID_IP,              "IP" },
	{ NLPID_IP6,             "IPv6" },
	{ NLPID_PPP,             "PPP" },
	{ 0,                     NULL },
};

static dissector_table_t fr_subdissector_table;
static dissector_table_t fr_osinl_subdissector_table;

static void dissect_fr_nlpid(tvbuff_t *tvb, int offset, packet_info *pinfo,
			     proto_tree *tree, proto_item *ti,
			     proto_tree *fr_tree, guint8 fr_ctrl);
static void dissect_lapf(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree);
static void dissect_fr_xid(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree);

/* Used only for U frames */
static const xdlc_cf_items fr_cf_items = {
	NULL,
	NULL,
	&hf_fr_p,
	&hf_fr_f,
	NULL,
	&hf_fr_u_modifier_cmd,
	&hf_fr_u_modifier_resp,
	NULL,
	&hf_fr_ftype_s_u
};

/* Used only for I and S frames */
static const xdlc_cf_items fr_cf_items_ext = {
	&hf_fr_n_r,
	&hf_fr_n_s,
	&hf_fr_p_ext,
	&hf_fr_f_ext,
	&hf_fr_s_ftype,
	NULL,
	NULL,
	&hf_fr_ftype_i,
	&hf_fr_ftype_s_u_ext
};

void
capture_fr(const guchar *pd, int offset, int len, packet_counts *ld)
{
  guint8  fr_octet;
  guint32 addr;
  guint8  fr_ctrl;
  guint8  fr_nlpid;

  /*
   * OK, fetch the address field - keep going until we get an EA bit.
   */
  if (!BYTES_ARE_IN_FRAME(offset, len, 1)) {
    ld->other++;
    return;
  }
  fr_octet = pd[offset];
  if (fr_octet & FRELAY_EA) {
    /*
     * Bogus!  There should be at least 2 octets.
     * XXX - is this FRF.12 frame relay fragmentation?  If so, can
     * we handle that?
     */
    ld->other++;
    return;
  }
  /*
   * The first octet contains the upper 6 bits of the DLCI, as well
   * as the C/R bit.
   */
  addr = (fr_octet & FRELAY_UPPER_DLCI) >> 2;
  offset++;

  /*
   * The second octet contains 4 more bits of DLCI, as well as FECN,
   * BECN, and DE.
   */
  if (!BYTES_ARE_IN_FRAME(offset, len, 1)) {
    ld->other++;
    return;
  }
  fr_octet = pd[offset];
  addr = (addr << 4) | ((fr_octet & FRELAY_SECOND_DLCI) >> 4);
  offset++;

  if (!(fr_octet & FRELAY_EA)) {
    /*
     * We have 3 or more address octets.
     *
     * The third octet contains 7 more bits of DLCI if EA isn't set,
     * and lower DLCI or DL-CORE control plus the DLCI or DL-CORE
     * control indicator flag if EA is set.
     */
    if (!BYTES_ARE_IN_FRAME(offset, len, 1)) {
      ld->other++;
      return;
    }
    fr_octet = pd[offset];
    if (!(fr_octet & FRELAY_EA)) {
      /*
       * 7 more bits of DLCI.
       */
      addr = (addr << 7) | ((fr_octet & FRELAY_THIRD_DLCI) >> 1);
      offset++;
      if (!BYTES_ARE_IN_FRAME(offset, len, 1)) {
        ld->other++;
        return;
      }
      fr_octet = pd[offset];
      while (!(fr_octet & FRELAY_EA)) {
	/*
	 * Bogus!  More than 4 octets of address.
	 */
        offset++;
        if (!BYTES_ARE_IN_FRAME(offset, len, 1)) {
          ld->other++;
          return;
        }
	fr_octet = pd[offset];
      }
    }

    /*
     * Last octet - contains lower DLCI or DL-CORE control, DLCI or
     * DL-CORE control indicator flag.
     */
    if (fr_octet & FRELAY_DC) {
      /*
       * DL-CORE.
       */
    } else {
      /*
       * Last 6 bits of DLCI.
       */
      addr = (addr << 6) | ((fr_octet & FRELAY_LOWER_DLCI) >> 2);
    }
  }

  switch (fr_encap) {

  case FRF_3_2:
    if (!BYTES_ARE_IN_FRAME(offset, len, 1)) {
      ld->other++;
      return;
    }
    fr_ctrl = pd[offset];
    if (fr_ctrl == XDLC_U) {
      offset++;

      /*
       * XXX - treat DLCI 0 specially?  On DLCI 0, an NLPID of 0x08
       * means Q.933, but on other circuits it could be the "for
       * protocols which do not have an NLPID assigned or do not
       * have a SNAP encapsulation" stuff from RFC 2427.
       */
      if (!BYTES_ARE_IN_FRAME(offset, len, 1)) {
        ld->other++;
        return;
      }
      fr_nlpid = pd[offset];
      if (fr_nlpid == 0) {
	offset++;
        if (!BYTES_ARE_IN_FRAME(offset, len, 1)) {
          ld->other++;
          return;
        }
	fr_nlpid = pd[offset];
      }
      offset++;
      switch (fr_nlpid) {

      case NLPID_IP:
        capture_ip(pd, offset, len, ld);
        break;

      case NLPID_IP6:
        capture_ipv6(pd, offset, len, ld);
        break;

      case NLPID_PPP:
        capture_ppp_hdlc(pd, offset, len, ld);
        break;

      case NLPID_SNAP:
        capture_snap(pd, offset, len, ld);
        break;

      default:
        ld->other++;
        break;
      }
    } else {
      if (addr == 0) {
	/*
	 * This must be some sort of LAPF on DLCI 0 for SVC
	 * because DLCI 0 is reserved for LMI and SVC signaling
	 * encapsulated in LAPF, and LMI is transmitted in
	 * unnumbered information (03), so this must be LAPF
	 * (guessing).
	 *
	 * XXX - but what is it?  Is Q.933 carried inside UI
	 * frames or other types of frames or both?
	 */
	ld->other++;
	return;
      }
      if (fr_ctrl == (XDLC_U|XDLC_XID)) {
      	/*
      	 * XID.
      	 */
	ld->other++;
	return;
      }

      /*
       * If the data does not start with unnumbered information (03) and
       * the DLCI# is not 0, then there may be Cisco Frame Relay encapsulation.
       */
      capture_chdlc(pd, offset, len, ld);
    }
    break;

  case GPRS_NS:
    ld->other++;
    break;

  case RAW_ETHER:
    if (addr != 0)
      capture_eth(pd, offset, len, ld);
    else
      ld->other++;
    break;
  }
}

static void
dissect_fr_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
		  gboolean has_direction, gboolean decode_address )
{
  int offset = 0;
  proto_item *ti = NULL;
  proto_tree *fr_tree = NULL;
  proto_item *octet_item = NULL;
  proto_tree *octet_tree = NULL;
  guint8 fr_octet;
  int is_response = FALSE;
  guint32 addr = 0;
  guint8  fr_ctrl;
  guint16 fr_type;
  tvbuff_t *next_tvb;

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

  if (has_direction) {
    if (pinfo->pseudo_header->x25.flags & FROM_DCE) {
      col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DTE");
      col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DCE");
    } else {
      col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DCE");
      col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DTE");
    }
  }

  if (tree) {
      ti = proto_tree_add_protocol_format(tree, proto_fr, tvb, 0, -1, "Frame Relay");
      fr_tree = proto_item_add_subtree(ti, ett_fr);
  }

  if (decode_address)
  {
    /*
     * OK, fetch the address field - keep going until we get an EA bit.
     */
    fr_octet = tvb_get_guint8(tvb, offset);

    if (fr_octet & FRELAY_EA) {
      /*
       * Bogus!  There should be at least 2 octets.
       * XXX - is this FRF.12 frame relay fragmentation?  If so, we
       * should dissect it as such, if possible.
       */
      addr = 0;
      if (tree) {
        proto_tree_add_text(fr_tree, tvb, offset, 1,
			    "Bogus 1-octet address field");
        offset++;
      }
    } else {
      /*
       * The first octet contains the upper 6 bits of the DLCI, as well
       * as the C/R bit.
       */
      addr = (fr_octet & FRELAY_UPPER_DLCI) >> 2;
      is_response = (fr_octet & FRELAY_CR);
      if (tree) {
        octet_item = proto_tree_add_text(fr_tree, tvb, offset, 1,
					 "First address octet: 0x%02x", fr_octet);
        octet_tree = proto_item_add_subtree(octet_item, ett_fr_address);
        proto_tree_add_uint(octet_tree, hf_fr_upper_dlci, tvb, offset, 1, fr_octet);
        proto_tree_add_boolean(octet_tree, hf_fr_cr, tvb, offset, 1, fr_octet);
        proto_tree_add_boolean(octet_tree, hf_fr_ea, tvb, offset, 1, fr_octet);
      }
      offset++;

      /*
       * The second octet contains 4 more bits of DLCI, as well as FECN,
       * BECN, and DE.
       */
      fr_octet = tvb_get_guint8(tvb, offset);
      addr = (addr << 4) | ((fr_octet & FRELAY_SECOND_DLCI) >> 4);
      if (tree) {
        octet_item = proto_tree_add_text(fr_tree, tvb, offset, 1,
					 "Second address octet: 0x%02x",
					 fr_octet);
        octet_tree = proto_item_add_subtree(octet_item, ett_fr_address);
        proto_tree_add_uint(octet_tree, hf_fr_second_dlci, tvb, offset, 1, fr_octet);
        proto_tree_add_boolean(octet_tree, hf_fr_fecn, tvb, 0, offset, fr_octet);
        proto_tree_add_boolean(octet_tree, hf_fr_becn, tvb, 0, offset, fr_octet);
        proto_tree_add_boolean(octet_tree, hf_fr_de, tvb, 0, offset, fr_octet);
        proto_tree_add_boolean(octet_tree, hf_fr_ea, tvb, offset, 1, fr_octet);
      }
      offset++;

      if (!(fr_octet & FRELAY_EA)) {
        /*
         * We have 3 or more address octets.
         *
         * The third octet contains 7 more bits of DLCI if EA isn't set,
         * and lower DLCI or DL-CORE control plus the DLCI or DL-CORE
         * control indicator flag if EA is set.
         */
        fr_octet = tvb_get_guint8(tvb, offset);
        if (!(fr_octet & FRELAY_EA)) {
	  /*
	   * 7 more bits of DLCI.
	   */
	  addr = (addr << 7) | ((fr_octet & FRELAY_THIRD_DLCI) >> 1);
	  if (tree) {
	    octet_item = proto_tree_add_text(fr_tree, tvb, offset, 1,
					     "Third address octet: 0x%02x",
					     fr_octet);
	    octet_tree = proto_item_add_subtree(octet_item, ett_fr_address);
	    proto_tree_add_uint(octet_tree, hf_fr_third_dlci, tvb, offset, 1, fr_octet);
	    proto_tree_add_boolean(octet_tree, hf_fr_ea, tvb, offset, 1, fr_octet);
	  }
	  offset++;
	  fr_octet = tvb_get_guint8(tvb, offset);
	  while (!(fr_octet & FRELAY_EA)) {
	    /*
	     * Bogus!  More than 4 octets of address.
	     */
	    if (tree) {
	      proto_tree_add_text(fr_tree, tvb, offset, 1,
				 "Bogus extra address octet");
	    }
	    offset++;
	    fr_octet = tvb_get_guint8(tvb, offset);
	  }
        }
        if (tree) {
	  octet_item = proto_tree_add_text(fr_tree, tvb, offset, 1,
					   "Final address octet: 0x%02x",
					   fr_octet);
	  octet_tree = proto_item_add_subtree(octet_item, ett_fr_address);
        } 

        /*
         * Last octet - contains lower DLCI or DL-CORE control, DLCI or
         * DL-CORE control indicator flag.
         */
        if (fr_octet & FRELAY_DC) {
	  /*
	   * DL-CORE.
	   */
	  proto_tree_add_uint(octet_tree, hf_fr_dlcore_control, tvb, offset, 1, fr_octet);
        } else {
      	  /*
      	   * Last 6 bits of DLCI.
      	   */
      	  addr = (addr << 6) | ((fr_octet & FRELAY_LOWER_DLCI) >> 2);
	  proto_tree_add_uint(octet_tree, hf_fr_lower_dlci, tvb, offset, 1, fr_octet);
        }
        proto_tree_add_boolean(octet_tree, hf_fr_dc, tvb, offset, 1, fr_octet);
        proto_tree_add_boolean(octet_tree, hf_fr_ea, tvb, offset, 1, fr_octet);
      
        offset++;
      }
    }
    if (tree) {
      /* Put the full DLCI into the protocol tree. */
      proto_tree_add_uint(fr_tree, hf_fr_dlci, tvb, 0, offset, addr);
    }

    pinfo->ctype = CT_DLCI;
    pinfo->circuit_id = addr;

    if (check_col(pinfo->cinfo, COL_INFO)) {
      col_add_fstr(pinfo->cinfo, COL_INFO, "DLCI %u", addr);
    }
  }

  switch (fr_encap) {

  case FRF_3_2:
    fr_ctrl = tvb_get_guint8(tvb, offset);
    if (fr_ctrl == XDLC_U) {
      dissect_xdlc_control(tvb, offset, pinfo, fr_tree, hf_fr_control,
 			   ett_fr_control, &fr_cf_items, &fr_cf_items_ext,
 			   NULL, NULL, is_response, TRUE, TRUE);
      offset++;

      /*
       * XXX - treat DLCI 0 specially?  On DLCI 0, an NLPID of 0x08
       * means Q.933, but on other circuits it could be the "for
       * protocols which do not have an NLPID assigned or do not
       * have a SNAP encapsulation" stuff from RFC 2427.
       */
      dissect_fr_nlpid(tvb, offset, pinfo, tree, ti, fr_tree, fr_ctrl);
    } else {
      if (addr == 0) {
		/*
		 * This must be some sort of LAPF on DLCI 0 for SVC
		 * because DLCI 0 is reserved for LMI and SVC signaling
		 * encapsulated in LAPF, and LMI is transmitted in
		 * unnumbered information (03), so this must be LAPF
		 * (guessing).
		 *
		 * XXX - but what is it?  Is Q.933 carried inside UI
		 * frames or other types of frames or both?
		 */
		dissect_xdlc_control(tvb, offset, pinfo, fr_tree,
				     hf_fr_control, ett_fr_control,
				     &fr_cf_items, &fr_cf_items_ext,
				     NULL, NULL, is_response, TRUE, TRUE);
		dissect_lapf(tvb_new_subset_remaining(tvb,offset),pinfo,tree);
		return;
      }
      if (fr_ctrl == (XDLC_U|XDLC_XID)) {
		dissect_xdlc_control(tvb, offset, pinfo, fr_tree,
				     hf_fr_control, ett_fr_control,
				     &fr_cf_items, &fr_cf_items_ext,
				     NULL, NULL, is_response, TRUE, TRUE);
		dissect_fr_xid(tvb_new_subset_remaining(tvb,offset),pinfo,tree);
		return;
      }

      /*
       * If the data does not start with unnumbered information (03) and
       * the DLCI# is not 0, then there may be Cisco Frame Relay encapsulation.
       */
      fr_type  = tvb_get_ntohs(tvb, offset);
      if (ti != NULL) {
		/* Include the Cisco HDLC type in the top-level protocol
		   tree item. */
		proto_item_set_end(ti, tvb, offset+2);
      }
      chdlctype(fr_type, tvb, offset+2, pinfo, tree, fr_tree, hf_fr_chdlctype);
    }
    break;

  case GPRS_NS:
    next_tvb = tvb_new_subset_remaining(tvb, offset);
    if (addr != 0)
      call_dissector(gprs_ns_handle, next_tvb, pinfo, tree);
    else
      dissect_lapf(next_tvb, pinfo, tree);
    break;

  case RAW_ETHER:
    next_tvb = tvb_new_subset_remaining(tvb, offset);
    if (addr != 0)
      call_dissector(eth_withfcs_handle, next_tvb, pinfo, tree);
    else
      dissect_lapf(next_tvb, pinfo, tree);
    break;
  }
}

static void
dissect_fr(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
  dissect_fr_common(tvb, pinfo, tree, FALSE, TRUE );
}

static void
dissect_fr_phdr(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
  dissect_fr_common(tvb, pinfo, tree, TRUE, TRUE );
}

static void
dissect_fr_stripped_address(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
  dissect_fr_common(tvb, pinfo, tree, TRUE, FALSE );
}

static void dissect_fr_uncompressed(tvbuff_t *tvb, packet_info *pinfo,
				    proto_tree *tree)
{
  proto_item *ti = NULL;
  proto_tree *fr_tree = NULL;

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

  if (tree) {
      ti = proto_tree_add_protocol_format(tree, proto_fr, tvb, 0, -1, "Frame Relay");
      fr_tree = proto_item_add_subtree(ti, ett_fr);
  }
  dissect_fr_nlpid(tvb, 0, pinfo, tree, ti, fr_tree, XDLC_U);
}

static void dissect_fr_nlpid(tvbuff_t *tvb, int offset, packet_info *pinfo,
			     proto_tree *tree, proto_item *ti,
			     proto_tree *fr_tree, guint8 fr_ctrl)
{
  guint8  fr_nlpid;
  tvbuff_t *next_tvb;

  /*
   * Tentatively set the Frame Relay item not to include the NLPID,
   * as OSI network layer protocols consider it to be part of
   * the OSI PDU.
   */
  proto_item_set_end(ti, tvb, offset);
  fr_nlpid = tvb_get_guint8 (tvb,offset);
  if (fr_nlpid == 0) {
	if (tree)
		proto_tree_add_text(fr_tree, tvb, offset, 1, "Padding");
	offset++;
	if (ti != NULL) {
		/* Include the padding in the top-level protocol tree item. */
		proto_item_set_end(ti, tvb, offset);
	}
	fr_nlpid=tvb_get_guint8( tvb,offset);
  }

  /*
   * OSI network layer protocols consider the NLPID to be part
   * of the frame, so we'll pass it as part of the payload and,
   * if the protocol is one of those, add it as a hidden item here.
   * We check both the generic OSI NLPID dissector table and
   * the Frame Relay OSI NLPID dissector table - the latter is for
   * NLPID's such as 0x08, which is Q.933 in Frame Relay but
   * other protocols (e.g., Q.931) on other network layers.
   *
   * "OSI network layer protocols" includes Q.933.
   *
   * XXX - note that an NLPID of 0x08 for Q.933 could either be a
   * Q.933 signaling message or a message for a protocol
   * identified by a 2-octet layer 2 protocol type and a
   * 2-octet layer 3 protocol type, those protocol type
   * octets having the values from octets 6, 6a, 7, and 7a
   * of a Q.931 low layer compatibility information element
   * (section 4.5.19 of Q.931; Q.933 says they have the values
   * from a Q.933 low layer compatibility information element,
   * but Q.933 low layer compatibility information elements
   * don't have protocol values in them).
   *
   * Assuming that, as Q.933 seems to imply, that Q.933 messages
   * look just like Q.931 messages except where it explicitly
   * says they differ, then the octet after the NLPID would,
   * in a Q.933 message, have its upper 4 bits zero (that's
   * the length of the call reference value, in Q.931, and
   * is limited to 15 or fewer octets).  As appears to be the case,
   * octet 6 of a Q.931 low layer compatibility element has the
   * 0x40 bit set, so you can distinguish between a Q.933
   * message and an encapsulated packet by checking whether
   * the upper 4 bits of the octet after the NLPID are zero.
   *
   * Either that, or it's Q.933 iff the DLCI is 0.
   */
  next_tvb = tvb_new_subset_remaining(tvb,offset);
  if (dissector_try_port(osinl_subdissector_table, fr_nlpid, next_tvb,
			 pinfo, tree) ||
      dissector_try_port(fr_osinl_subdissector_table, fr_nlpid, next_tvb,
			 pinfo, tree)) {
	/*
	 * Yes, we got a match.  Add the NLPID as a hidden item,
	 * so you can, at least, filter on it.
	 */
	if (tree) {
		proto_item *hidden_item;
		hidden_item = proto_tree_add_uint(fr_tree, hf_fr_nlpid,
				    tvb, offset, 1, fr_nlpid );
		PROTO_ITEM_SET_HIDDEN(hidden_item);
	}
	return;
  }

  /*
   * All other protocols don't.
   *
   * XXX - what about Cisco/Gang-of-Four LMI?  Is the 0x09 considered
   * to be part of the LMI PDU?
   */
  if (tree)
	proto_tree_add_uint(fr_tree, hf_fr_nlpid, tvb, offset, 1, fr_nlpid );
  offset++;

  switch (fr_nlpid) {

  case NLPID_SNAP:
	if (ti != NULL) {
		/* Include the NLPID and SNAP header in the top-level
		   protocol tree item. */
		proto_item_set_end(ti, tvb, offset+5);
	}
	dissect_snap(tvb, offset, pinfo, tree, fr_tree, fr_ctrl,
	      hf_fr_oui, hf_fr_snaptype, hf_fr_pid, 0);
	return;

  default:
	if (ti != NULL) {
		/* Include the NLPID in the top-level protocol tree item. */
		proto_item_set_end(ti, tvb, offset);
	}
	next_tvb = tvb_new_subset_remaining(tvb,offset);
	if (!dissector_try_port(fr_subdissector_table,fr_nlpid,
				next_tvb, pinfo, tree))
		call_dissector(data_handle,next_tvb, pinfo, tree);
	break;
  }
}

static void dissect_lapf(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
	proto_tree_add_text(tree, tvb, 0, 0, "Frame relay lapf not yet implemented");
	call_dissector(data_handle,tvb_new_subset_remaining(tvb,0),pinfo,tree);
}
static void dissect_fr_xid(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
	proto_tree_add_text(tree, tvb, 0, 0, "Frame relay xid not yet implemented");
	call_dissector(data_handle,tvb_new_subset_remaining(tvb,0),pinfo,tree);
}

/* Register the protocol with Wireshark */
void proto_register_fr(void)
{
  static hf_register_info hf[] = {
        { &hf_fr_ea, {
           "EA", "fr.ea", FT_BOOLEAN, 8, TFS(&ea_string),
            FRELAY_EA, "Extended Address", HFILL }},
        { &hf_fr_upper_dlci, {
           "Upper DLCI", "fr.upper_dlci", FT_UINT8, BASE_HEX,
            NULL, FRELAY_UPPER_DLCI, "Upper bits of DLCI", HFILL }},
        { &hf_fr_cr, {
           "CR", "fr.cr", FT_BOOLEAN, 8, TFS(&tfs_command_response),
            FRELAY_CR, "Command/Response", HFILL }},
        { &hf_fr_second_dlci, {
           "Second DLCI", "fr.second_dlci", FT_UINT8, BASE_HEX,
            NULL, FRELAY_SECOND_DLCI, "Bits below upper bits of DLCI", HFILL }},
        { &hf_fr_fecn, {
           "FECN", "fr.fecn", FT_BOOLEAN, 8,
            NULL, FRELAY_FECN, "Forward Explicit Congestion Notification", HFILL }},
        { &hf_fr_becn, {
           "BECN", "fr.becn", FT_BOOLEAN, 8,
            NULL, FRELAY_BECN, "Backward Explicit Congestion Notification", HFILL }},
        { &hf_fr_de, {
           "DE", "fr.de", FT_BOOLEAN, 8,
            NULL, FRELAY_DE, "Discard Eligibility", HFILL }},
        { &hf_fr_third_dlci, {
           "Third DLCI", "fr.third_dlci", FT_UINT8, BASE_HEX,
            NULL, FRELAY_THIRD_DLCI, "Additional bits of DLCI", HFILL }},
        { &hf_fr_dlcore_control, {
           "DL-CORE Control", "fr.dlcore_control", FT_UINT8, BASE_HEX,
            NULL, FRELAY_LOWER_DLCI, "DL-Core control bits", HFILL }},
        { &hf_fr_lower_dlci, {
           "Lower DLCI", "fr.lower_dlci", FT_UINT8, BASE_HEX,
            NULL, FRELAY_LOWER_DLCI, "Lower bits of DLCI", HFILL }},
        { &hf_fr_dc, {
           "DC", "fr.dc", FT_BOOLEAN, 16, TFS(&ctrl_string),
            FRELAY_CR, "Address/Control", HFILL }},
        { &hf_fr_dlci, {
           "DLCI", "fr.dlci", FT_UINT32, BASE_DEC,
            NULL, 0x0, "Data-Link Connection Identifier", HFILL }},
	{ &hf_fr_control, {
          "Control Field", "fr.control", FT_UINT8, BASE_HEX,
          NULL, 0x0, "Control field", HFILL }},
	{ &hf_fr_n_r, {
	  "N(R)", "fr.control.n_r", FT_UINT16, BASE_DEC,
	  NULL, XDLC_N_R_EXT_MASK, NULL, HFILL }},
	{ &hf_fr_n_s, {
	  "N(S)", "fr.control.n_s", FT_UINT16, BASE_DEC,
	  NULL, XDLC_N_S_EXT_MASK, NULL, HFILL }},
	{ &hf_fr_p, {
	  "Poll", "fr.control.p", FT_BOOLEAN, 8,
	  TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},
	{ &hf_fr_p_ext, {
	  "Poll", "fr.control.p", FT_BOOLEAN, 16,
	  TFS(&tfs_set_notset), XDLC_P_F_EXT, NULL, HFILL }},
	{ &hf_fr_f, {
	  "Final", "fr.control.f", FT_BOOLEAN, 8,
	  TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},
	{ &hf_fr_f_ext, {
	  "Final", "fr.control.f", FT_BOOLEAN, 16,
	  TFS(&tfs_set_notset), XDLC_P_F_EXT, NULL, HFILL }},
	{ &hf_fr_s_ftype, {
	  "Supervisory frame type", "fr.control.s_ftype", FT_UINT16, BASE_HEX,
	  VALS(stype_vals), XDLC_S_FTYPE_MASK, NULL, HFILL }},
	{ &hf_fr_u_modifier_cmd, {
	  "Command", "fr.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
	  VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
	{ &hf_fr_u_modifier_resp, {
	  "Response", "fr.control.u_modifier_resp", FT_UINT8, BASE_HEX,
	    VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
	{ &hf_fr_ftype_i, {
	  "Frame type", "fr.control.ftype", FT_UINT16, BASE_HEX,
	  VALS(ftype_vals), XDLC_I_MASK, NULL, HFILL }},
	{ &hf_fr_ftype_s_u, {
	  "Frame type", "fr.control.ftype", FT_UINT8, BASE_HEX,
	  VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},
	{ &hf_fr_ftype_s_u_ext, {
	  "Frame type", "fr.control.ftype", FT_UINT16, BASE_HEX,
	  VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},
        { &hf_fr_nlpid, {
           "NLPID", "fr.nlpid", FT_UINT8, BASE_HEX,
            VALS(fr_nlpid_vals), 0x0, "Frame Relay Encapsulated Protocol NLPID", HFILL }},
	{ &hf_fr_oui, {
	   "Organization Code",	"fr.snap.oui", FT_UINT24, BASE_HEX,
	   VALS(oui_vals), 0x0, NULL, HFILL }},
	{ &hf_fr_pid, {
	   "Protocol ID", "fr.snap.pid", FT_UINT16, BASE_HEX,
	   NULL, 0x0, NULL, HFILL }},
        { &hf_fr_snaptype, {
           "Type", "fr.snaptype", FT_UINT16, BASE_HEX,
            VALS(etype_vals), 0x0, "Frame Relay SNAP Encapsulated Protocol", HFILL }},
        { &hf_fr_chdlctype, {
           "Type", "fr.chdlctype", FT_UINT16, BASE_HEX,
            VALS(chdlc_vals), 0x0, "Frame Relay Cisco HDLC Encapsulated Protocol", HFILL }},
  };

  /* Setup protocol subtree array */
  static gint *ett[] = {
    &ett_fr,
    &ett_fr_address,
    &ett_fr_control,
  };
  static enum_val_t fr_encap_options[] = {
    { "frf-3.2", "FRF 3.2/Cisco HDLC", FRF_3_2 },
    { "gprs-ns", "GPRS Network Service", GPRS_NS },
    { "ethernet", "Raw Ethernet", RAW_ETHER },
    { NULL, NULL, 0 },
  };
  module_t *frencap_module;

  proto_fr = proto_register_protocol("Frame Relay", "FR", "fr");
  proto_register_field_array(proto_fr, hf, array_length(hf));
  proto_register_subtree_array(ett, array_length(ett));

  fr_subdissector_table = register_dissector_table("fr.ietf",
	"Frame Relay NLPID", FT_UINT8, BASE_HEX);
  fr_osinl_subdissector_table = register_dissector_table("fr.osinl",
	"Frame Relay OSI NLPID", FT_UINT8, BASE_HEX);

  register_dissector("fr_uncompressed", dissect_fr_uncompressed, proto_fr);
  register_dissector("fr", dissect_fr, proto_fr);
  register_dissector("fr_stripped_address", dissect_fr_stripped_address, proto_fr);

  frencap_module = prefs_register_protocol(proto_fr, NULL);
  /*
   * XXX - this should really be per-circuit - I've seen at least one
   * capture where different DLCIs have different encapsulations - but
   * we don't yet have any support for per-circuit encapsulations.
   *
   * Even with that, though, we might want a default encapsulation,
   * so that people dealing with GPRS can make gprs-ns the default.
   */
  prefs_register_enum_preference(frencap_module, "encap", "Encapsulation",
				 "Encapsulation", &fr_encap,
				 fr_encap_options, FALSE);
}

void proto_reg_handoff_fr(void)
{
  dissector_handle_t fr_handle, fr_phdr_handle;

  fr_handle = find_dissector("fr");
  dissector_add("gre.proto", ETHERTYPE_RAW_FR, fr_handle);
  dissector_add("wtap_encap", WTAP_ENCAP_FRELAY, fr_handle);

  fr_phdr_handle = create_dissector_handle(dissect_fr_phdr, proto_fr);
  dissector_add("wtap_encap", WTAP_ENCAP_FRELAY_WITH_PHDR, fr_phdr_handle);

  eth_withfcs_handle = find_dissector("eth_withfcs");
  gprs_ns_handle = find_dissector("gprs_ns");
  data_handle = find_dissector("data");

  osinl_subdissector_table = find_dissector_table("osinl");
}
