/* packet-ajp13.c
 * Routines for AJP13 dissection
 * Copyright 2002, Christopher K. St. John <cks@distributopia.com>
 *
 * $Id: packet-ajp13.c 14786 2005-06-26 19:56:52Z guy $
 *
 * Ethereal - Network traffic analyzer
 * By Gerald Combs <gerald@ethereal.com>
 * 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.
 */

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

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

#include <glib.h>

#include <epan/packet.h>
#include <epan/conversation.h>
#include "packet-tcp.h"



/* IMPORTANT IMPLEMENTATION NOTES
 *
 * You need to be looking at: jk/doc/AJP13.html in the
 * jakarta-tomcat-connectors repository.
 *
 * If you're an ethereal dissector guru, then you can skip the rest of
 * this. I'm writing it all down because I've written 3 dissectors so
 * far and every time I've forgotten it all and had to re-learn it
 * from scratch. Not this time, damnit.
 *
 * Dissector routines get called in two phases:
 *
 * The first phase is an in-order traversal of every incoming
 * frame. Since we know it's in-order, we can set up a "conversational
 * state" that records context-sensitive stuff like "was there a
 * content-length in the previous request". During this first pass
 * through the data, the "tree" parameter might be null, or not. For
 * the regular gui-based ethereal, it's null, which means we don't
 * actually display the dissected data in the gui quite yet. For the
 * text based interface, we might do the parsing and display both in
 * this first pass.
 *
 * The second phase happens when the data is actually displayed. In
 * this pase the "tree" param is non-null, so you've got a hook to
 * hang the parsed-out display data on. Since there might be gigabytes
 * worth of capture data, the display code only calls the dissector
 * for the stuff the user actually clicks on. So you have to assume
 * the dissector is getting called on random frames, you can't depend
 * on ordering anymore.
 *
 * But some parts of the AJP13 capture stream are context sensitive.
 * That's no big deal during the first in-order pass, but the second
 * phase requires us to display any random frame correctly. So during
 * the first in-order phase we create a per-frame user data structure
 * and attach it to the frame using p_add_proto_data.
 *
 * Since AJP13 is a TCP/IP based protocol, writing a dissector for it
 * requires addressing several other issues:
 *
 * 1) TCP/IP segments can get retransmitted or be sent out of
 * order. Users don't normally care, because the low-level kernel
 * networking code takes care of reassembling them properly. But we're
 * looking at raw network packets, aren't we? The stuff on the
 * wire. Ethereal has been getting better and better at helping
 * dissectors with this. I'm a little fuzzy on the details, but my
 * uderstanding is that ethereal now contains a fairly substantial
 * user-space TCP/IP stack so it can re-assemble the data. But I might
 * be wrong. Since AJP13 is going to be used either on the loopback
 * interface or on a LAN, it isn't likely to be a big issues anyway.
 *
 * 2) AJP13 packets (PDU's or protocol data unit's in
 * networking-speak) don't necessarily line up with TCP segments. That
 * is, one TCP segment can have more than one AJP13 PDU, or one AJP13
 * PDU can stretch across multiple TCP segments. Assembling them is
 * obviously possible, but a royal pain. During the "phase one"
 * in-order pass you have to keep track of a bunch of offsets and
 * store which PDU goes with which TCP segment. Luckly, recent
 * (0.9.4+) versions of ethereal provide the "tcp_dissect_pdus()"
 * function that takes care of much of the work. See the comments in
 * packet-tcp.c, the example code in packet-dns.c, or check the
 * ethereal-dev archives for details.
 *
 * 3) Ethereal isn't guaranteed to see all the data. I'm a little
 * unclear on all the possible failure modes, but it comes down to: a)
 * Not your fault: it's an imperfect world, we're eavesdroppers, and
 * stuff happens. We might totally miss packets or get garbled
 * data. Or b) Totally your fault: you turn on the capture during the
 * middle of an AJP13 conversation and the capture starts out with
 * half an AJP13 PDU. This code doesn't currently handle either case
 * very well, but you can get arbitrarily clever. Like: put in tests
 * to see if this packet has reasonable field values, and if it
 * doesn't, walk the offset ahead until we see a matching magic number
 * field, then re-test. But we don't do that now, and since we're
 * using tcp_dissect_pdu's, I'm not sure how to do it.
 *
 */


/*
 * Request/response header codes. Common headers are stored as ints in
 * an effort to improve performance. Why can't we just have one big
 * list?
 */

static const value_string req_header_codes[] = {
  { 0x01, "accept" },
  { 0x02, "accept-charset" },
  { 0x03, "accept-encoding" },
  { 0x04, "accept-language" },
  { 0x05, "authorization" },
  { 0x06, "connection" },
  { 0x07, "content-type" },
  { 0x08, "content-length" },
  { 0x09, "cookie" },
  { 0x0A, "cookie2" },
  { 0x0B, "host" },
  { 0x0C, "pragma" },
  { 0x0D, "referer" },
  { 0x0E, "user-agent" },
};


static const value_string rsp_header_codes[] = {
  { 0x01, "Content-Type" },
  { 0x02, "Content-Language" },
  { 0x03, "Content-Length" },
  { 0x04, "Date" },
  { 0x05, "Last-Modified" },
  { 0x06, "Location" },
  { 0x07, "Set-Cookie" },
  { 0x08, "Set-Cookie2" },
  { 0x09, "Servlet-Engine" },
  { 0x0A, "Status" },
  { 0x0B, "WWW-Authenticate" },
};


static const value_string mtype_codes[] = {
  { 0, "BAD" },
  { 1, "BAD" },
  { 2, "FORWARD REQUEST" },
  { 3, "SEND BODY CHUNK" },
  { 4, "SEND HEADERS" },
  { 5, "END RESPONSE" },
  { 6, "GET BODY CHUNK" },
  { 7, "SHUTDOWN" },
};


static const value_string http_method_codes[] = {
  { 1, "OPTIONS" },
  { 2, "GET" },
  { 3, "HEAD" },
  { 4, "POST" },
  { 5, "PUT" },
  { 6, "DELETE" },
  { 7, "TRACE" },
  { 8, "PROPFIND" },
  { 9, "PROPPATCH" },
  { 10, "MKCOL" },
  { 11, "COPY" },
  { 12, "MOVE" },
  { 13, "LOCK" },
  { 14, "UNLOCK" },
  { 15, "ACL" },
  { 16, "REPORT" },
  { 17, "VERSION-CONTROL" },
  { 18, "CHECKIN" },
  { 19, "CHECKOUT" },
  { 20, "UNCHECKOUT" },
  { 21, "SEARCH" },
};



static int proto_ajp13     = -1;
static int hf_ajp13_magic  = -1;
static int hf_ajp13_len    = -1;
static int hf_ajp13_code   = -1;
static int hf_ajp13_method = -1;
static int hf_ajp13_ver    = -1;
static int hf_ajp13_uri    = -1;
static int hf_ajp13_raddr  = -1;
static int hf_ajp13_rhost  = -1;
static int hf_ajp13_srv    = -1;
static int hf_ajp13_port   = -1;
static int hf_ajp13_sslp   = -1;
static int hf_ajp13_nhdr   = -1;
static int hf_ajp13_hname  = -1;
static int hf_ajp13_hval   = -1;
static int hf_ajp13_rlen   = -1;
static int hf_ajp13_reusep = -1;
static int hf_ajp13_rstatus= -1;
static int hf_ajp13_rsmsg  = -1;
static int hf_ajp13_data   = -1;
static gint ett_ajp13 = -1;


typedef struct ajp13_conv_data {
  int content_length;
  gboolean was_get_body_chunk;	/* XXX - not used */
} ajp13_conv_data;

static GMemChunk *ajp13_conv_data_chunk = NULL;

typedef struct ajp13_frame_data {
  gboolean is_request_body;
} ajp13_frame_data;

static GMemChunk  *ajp13_frame_data_chunk = NULL;

static int ajp13_packet_init_count = 100;

/* ajp13, in sort of a belt-and-suspenders move, encodes strings with
 * both a leading length field, and a trailing null. Mostly, see
 * AJPv13.html. The returned length _includes_ the trailing null, if
 * there is one.
 *
 * XXX - is there a tvbuff routine to handle this?
 */
static guint16
get_nstring(tvbuff_t *tvb, gint offset, guint8* cbuf, size_t cbuflen)
{
  guint16 len;
  guint16 copylen;

  len = tvb_get_ntohs(tvb, offset);

  if (len == 0xffff) {
    cbuf[0] = '\0';
    len = 0;
  } else {
    copylen = len;
    if (copylen > cbuflen - 1)
      copylen = cbuflen - 1;
    tvb_memcpy(tvb, cbuf, offset+2, copylen);
    cbuf[copylen] = '\0';
    len++;
  }
  return len;
}



/* dissect a response. more work to do here.
 */
static void
display_rsp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *ajp13_tree)
{
  const gchar* msg_code = NULL;
  int pos = 0;
  guint8 mcode = 0;
  char mcode_buf[1024];
  int i;

  /* MAGIC
   */
  if (ajp13_tree)
    proto_tree_add_item(ajp13_tree, hf_ajp13_magic, tvb, pos, 2, 0);
  pos+=2;

  /* PDU LENGTH
   */
  if (ajp13_tree)
    proto_tree_add_item(ajp13_tree, hf_ajp13_len,   tvb, pos, 2, 0);
  pos+=2;

  /* MESSAGE TYPE CODE
   */
  mcode = tvb_get_guint8(tvb, pos);
  msg_code = val_to_str(mcode, mtype_codes, "UNKNOWN");
  sprintf(mcode_buf, "(%d) %s", mcode, msg_code);
  if (ajp13_tree)
    proto_tree_add_string(ajp13_tree, hf_ajp13_code, tvb, pos, 1, mcode_buf);
  pos+=1;

  if(check_col(pinfo->cinfo, COL_INFO))
    col_append_str(pinfo->cinfo, COL_INFO, msg_code);

  if (mcode == 5) {
    if (ajp13_tree)
      proto_tree_add_item(ajp13_tree, hf_ajp13_reusep, tvb, pos, 1, 0);
    pos+=1;

  } else if (mcode == 4) {

    guint8 rsmsg_bytes[8*1024]; /* DANGER WILL ROBINSON */
    guint16 rsmsg_len;
    guint16 nhdr;
    guint16 rcode_num;

    /* HTTP RESPONSE STATUS CODE
     */
    rcode_num = tvb_get_ntohs(tvb, pos);
    if (ajp13_tree)
      proto_tree_add_item(ajp13_tree, hf_ajp13_rstatus, tvb, pos, 2, 0);
    pos+=2;
    if(check_col(pinfo->cinfo, COL_INFO))
      col_append_fstr(pinfo->cinfo, COL_INFO, ":%d", rcode_num);

    /* HTTP RESPONSE STATUS MESSAGE
     */
    rsmsg_len = get_nstring(tvb, pos, rsmsg_bytes, sizeof rsmsg_bytes);
    pos+=2;
    if (ajp13_tree)
      proto_tree_add_item(ajp13_tree, hf_ajp13_rsmsg, tvb, pos, rsmsg_len, 0);
    pos+=rsmsg_len;
    /* dangerous assumption that we can just %s out raw bytes */
    if(check_col(pinfo->cinfo, COL_INFO))
      col_append_fstr(pinfo->cinfo, COL_INFO, " %s", rsmsg_bytes);

    /* NUMBER OF HEADERS
     */
    nhdr = tvb_get_ntohs(tvb, pos);
    if (ajp13_tree)
      proto_tree_add_item(ajp13_tree, hf_ajp13_nhdr, tvb, pos, 2, 0);
    pos+=2;

    /* HEADERS
     */
    for(i=0; i<nhdr; i++) {

      guint8 hcd;
      guint8 hid;
      char hval[8192];
      guint16 hval_len;
      int orig_pos = pos;
      const gchar* hname = NULL;
      int dp = 0;
      int cl = 0;
      guint8 hname_bytes[1024];
      gchar hname_value[8*1024];

      /* HEADER CODE/NAME
       */
      hcd = tvb_get_guint8(tvb, pos);

      if (hcd == 0xA0) {
        pos+=1;
        hid = tvb_get_guint8(tvb, pos);
        pos+=1;

        hname = val_to_str(hid, rsp_header_codes, "UNKNOWN");
        /* Content-Length header (encoded by 0x08) is special */
        if (hid == 0x08)
          cl = 1;
      } else {
        int hname_len = get_nstring(tvb, pos, hname_bytes, sizeof hname_bytes);

        pos+=hname_len+2;
        hname = (gchar*)hname_bytes; /* VERY EVIL */
      }

      dp = pos-orig_pos;

      /* HEADER VALUE
       */
      orig_pos = pos;
      hval_len = get_nstring(tvb, pos, hval, sizeof hval);

      pos+=hval_len+2;
      dp = pos - orig_pos;
      if (ajp13_tree) {
        sprintf(hname_value, "%s : %s", hname, hval);
        proto_tree_add_string(ajp13_tree, hf_ajp13_hval, tvb, orig_pos, dp, hname_value);
      }
    }

  } else if (mcode == 6) {
    if (ajp13_tree)
      proto_tree_add_item(ajp13_tree, hf_ajp13_rlen, tvb, pos, 2, 0);
    pos+=2;

  } else {
    /* MESSAGE DATA (COPOUT)
     */
    if (ajp13_tree)
      proto_tree_add_item(ajp13_tree, hf_ajp13_data,  tvb, pos+2, -1, 0);
  }
}



/* dissect a request body. see AJPv13.html, but the idea is that these
 * packets, unlike all other packets, have no type field. you just
 * sort of have to know that they're coming based on the previous
 * packets.
 */
static void
display_req_body(tvbuff_t *tvb, proto_tree *ajp13_tree)
{
  /*printf("ajp13:display_req_body()\n");*/

  if (ajp13_tree) {

    guint8 body_bytes[128*1024]; /* DANGER WILL ROBINSON */
    int pos = 0;
    guint16 body_len;

    /* MAGIC
     */
    proto_tree_add_item(ajp13_tree, hf_ajp13_magic, tvb, pos, 2, 0);
    pos+=2;

    /* PACKET LENGTH
     */
    proto_tree_add_item(ajp13_tree, hf_ajp13_len, tvb, pos, 2, 0);
    pos+=2;

    /* BODY (AS STRING)
     */
    body_len = get_nstring(tvb, pos, body_bytes, sizeof body_bytes);
    proto_tree_add_item(ajp13_tree, hf_ajp13_data, tvb, pos+2, body_len-1, 0);
  }
}



/* note that even if ajp13_tree is null on the first pass, we still
 * need to dissect the packet in order to determine if there is a
 * content-length, and thus if there is a subsequent automatic
 * request-body transmitted in the next request packet. if there is a
 * content-length, we record the fact in the conversation context.
 * ref the top of this file for comments explaining the multi-pass
 * thing.
*/
static void
display_req_forward(tvbuff_t *tvb, packet_info *pinfo,
                    proto_tree *ajp13_tree,
                    ajp13_conv_data* cd)
{
  int pos = 0;
  guint8 meth;
  guint8 cod;
  guint8 ver[1024];
  guint16 ver_len;
  guint8 uri[4096];
  guint16 uri_len;
  guint8 raddr[4096];
  guint16 raddr_len;
  guint8 rhost[4096];
  guint16 rhost_len;
  guint8 srv[4096];
  guint16 srv_len;
  guint nhdr;
  guint i;

  if (ajp13_tree)
    proto_tree_add_item(ajp13_tree, hf_ajp13_magic, tvb, pos, 2, 0);
  pos+=2;

  if (ajp13_tree)
    proto_tree_add_item(ajp13_tree, hf_ajp13_len, tvb, pos, 2, 0);
  pos+=2;

  /* PACKET CODE
   */
  cod = tvb_get_guint8(tvb, 4);
  if (ajp13_tree) {
    const gchar* msg_code = NULL;
    char mcode_buf[1024];
    msg_code = val_to_str(cod, mtype_codes, "UNKNOWN");
    sprintf(mcode_buf, "(%d) %s", cod, msg_code);
    proto_tree_add_string(ajp13_tree, hf_ajp13_code, tvb, pos, 1, mcode_buf);
  }
  pos+=1;

  /* HTTP METHOD (ENCODED AS INTEGER)
   */
  {
    const gchar* meth_code = NULL;
    meth = tvb_get_guint8(tvb, pos);
    meth_code = val_to_str(meth, http_method_codes, "UNKNOWN");
    if (ajp13_tree) {
      char mcode_buf[1024];
      sprintf(mcode_buf, "(%d) %s", meth, meth_code);
      proto_tree_add_string(ajp13_tree, hf_ajp13_method, tvb, pos, 1, mcode_buf);
    }
    if(check_col(pinfo->cinfo, COL_INFO))
      col_append_str(pinfo->cinfo, COL_INFO, meth_code);
    pos+=1;
  }

  /* HTTP VERSION STRING
   */
  ver_len = get_nstring(tvb, pos, ver, sizeof ver);
  pos+=2; /* skip over size */
  if (ajp13_tree)
    proto_tree_add_item(ajp13_tree, hf_ajp13_ver, tvb, pos, ver_len, 0);
  pos=pos+ver_len;  /* skip over chars + trailing null */

  /* URI
   */
  uri_len = get_nstring(tvb, pos, uri, sizeof uri);
  pos+=2; /* skip over size */
  if (ajp13_tree)
    proto_tree_add_item(ajp13_tree, hf_ajp13_uri, tvb, pos, uri_len, 0);
  pos=pos+uri_len;  /* skip over chars + trailing null */


  if(check_col(pinfo->cinfo, COL_INFO))
    col_append_fstr(pinfo->cinfo, COL_INFO, " %s %s", uri, ver);


  /* REMOTE ADDRESS
   */
  raddr_len = get_nstring(tvb, pos, raddr, sizeof raddr);
  pos+=2; /* skip over size */
  if (ajp13_tree)
    proto_tree_add_item(ajp13_tree, hf_ajp13_raddr, tvb, pos, raddr_len, 0);
  pos=pos+raddr_len;  /* skip over chars + trailing null */

  /* REMOTE HOST
   */
  rhost_len = get_nstring(tvb, pos, rhost, sizeof rhost);
  pos+=2; /* skip over size */
  if (ajp13_tree)
    proto_tree_add_item(ajp13_tree, hf_ajp13_rhost, tvb, pos, rhost_len, 0);
  pos=pos+rhost_len;  /* skip over chars + trailing null */

  /* SERVER NAME
   */
  srv_len = get_nstring(tvb, pos, srv, sizeof srv);
  pos+=2; /* skip over size */
  if (ajp13_tree)
    proto_tree_add_item(ajp13_tree, hf_ajp13_srv, tvb, pos, srv_len, 0);
  pos=pos+srv_len;  /* skip over chars + trailing null */

  /* SERVER PORT
   */
  if (ajp13_tree)
    proto_tree_add_item(ajp13_tree, hf_ajp13_port, tvb, pos, 2, 0);
  pos+=2;

  /* IS SSL?
   */
  if (ajp13_tree)
    proto_tree_add_item(ajp13_tree, hf_ajp13_sslp, tvb, pos, 1, 0);
  pos+=1;

  /* NUM HEADERS
   */
  nhdr = tvb_get_ntohs(tvb, pos);

  if (ajp13_tree)
    proto_tree_add_item(ajp13_tree, hf_ajp13_nhdr, tvb, pos, 2, 0);
  pos+=2;
  cd->content_length = 0;

  /* HEADERS
   */
  for(i=0; i<nhdr; i++) {

    guint8 hcd;
    guint8 hid;
    char hval[8192];
    guint16 hval_len;
    int orig_pos = pos;
    const gchar* hname = NULL;
    int dp = 0;
    int cl = 0;
    guint8 hname_bytes[1024];

    /* HEADER CODE/NAME
     */
    hcd = tvb_get_guint8(tvb, pos);

    if (hcd == 0xA0) {
      pos+=1;
      hid = tvb_get_guint8(tvb, pos);
      pos+=1;

      hname = val_to_str(hid, req_header_codes, "UNKNOWN");
      if (hid == 0x08)
        cl = 1;
    } else {
      int hname_len = get_nstring(tvb, pos, hname_bytes, sizeof hname_bytes);

      pos+=hname_len+2;
      hname = (gchar*)hname_bytes; /* VERY EVIL */
    }

    dp = pos-orig_pos;

    /* HEADER VALUE
     */
    orig_pos = pos;
    hval_len = get_nstring(tvb, pos, hval, sizeof hval);

    pos+=hval_len+2;
    dp = pos - orig_pos;
    if (ajp13_tree) {
      proto_tree_add_string_format(ajp13_tree, hf_ajp13_hval,
                                   tvb, orig_pos, dp, hname,
                                   "%s: %s", hname, hval);
    }
    if (cl) {
      cl = atoi(hval);
      cd->content_length = cl;
    }
  }
}



/* main dissector function. ethereal calls it for segments in both
 * directions.
 */
static void
dissect_ajp13_tcp_pdu(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
  guint16 mag;
  guint16 len;
  conversation_t *conv = NULL;
  ajp13_conv_data *cd = NULL;
  proto_tree *ajp13_tree = NULL;
  ajp13_frame_data* fd = NULL;

  /* conversational state really only does us good during the first
   * in-order traversal
   */
  conv = find_conversation(pinfo->fd->num, &pinfo->src, &pinfo->dst, pinfo->ptype,
                           pinfo->srcport, pinfo->destport, 0);
  if (!conv) {
    conv = conversation_new(pinfo->fd->num, &pinfo->src, &pinfo->dst, pinfo->ptype,
                            pinfo->srcport, pinfo->destport, 0);
  }
  cd = (ajp13_conv_data*)conversation_get_proto_data(conv, proto_ajp13);
  if (!cd) {
    cd = (ajp13_conv_data*)g_mem_chunk_alloc(ajp13_conv_data_chunk);
    cd->content_length = 0;
    cd->was_get_body_chunk = FALSE;
    conversation_add_proto_data(conv, proto_ajp13, cd);
  }

  /* we use the per segment user data to record the conversational
   * state for use later on when we're called out of order (see
   * comments at top of this file)
   */
  fd = (ajp13_frame_data*)p_get_proto_data(pinfo->fd, proto_ajp13);
  if (!fd) {
    /*printf("ajp13:dissect_ajp13_common():no frame data, adding");*/
    /* since there's no per-packet user data, this must be the first
     * time we've see the packet, and it must be the first "in order"
     * pass through the data.
     */
    fd = (ajp13_frame_data*)g_mem_chunk_alloc(ajp13_frame_data_chunk);
    p_add_proto_data(pinfo->fd, proto_ajp13, fd);
    fd->is_request_body = FALSE;
    if (cd->content_length) {
      /* this is screwy, see AJPv13.html. the idea is that if the
       * request has a body (as determined by the content-length
       * header), then there's always an immediate follow-up PDU with
       * no GET_BODY_CHUNK from the container.
       */
      fd->is_request_body = TRUE;
    }
  }

  if (check_col(pinfo->cinfo, COL_INFO))
    col_clear(pinfo->cinfo, COL_INFO);

  mag = tvb_get_ntohs(tvb, 0);
  len = tvb_get_ntohs(tvb, 2);

  if (check_col(pinfo->cinfo, COL_PROTOCOL))
    col_set_str(pinfo->cinfo, COL_PROTOCOL, "AJP13");
  if (check_col(pinfo->cinfo, COL_INFO)) {
    if (mag == 0x1234 && !fd->is_request_body)
      col_append_fstr(pinfo->cinfo, COL_INFO, "%d:REQ:", conv->index);
    else if (mag == 0x1234 && fd->is_request_body)
      col_append_fstr(pinfo->cinfo, COL_INFO, "%d:REQ:Body", conv->index);
    else if (mag == 0x4142)
      col_append_fstr(pinfo->cinfo, COL_INFO, "%d:RSP:", conv->index);
    else
      col_set_str(pinfo->cinfo, COL_INFO, "AJP13 Error?");
  }

  if (tree) {
    proto_item *ti;
    ti = proto_tree_add_item(tree, proto_ajp13, tvb, 0, tvb_length(tvb), FALSE);
    ajp13_tree = proto_item_add_subtree(ti, ett_ajp13);
  }

  if (mag == 0x1234) {

    if (fd->is_request_body)
      display_req_body(tvb, ajp13_tree);
    else
      display_req_forward(tvb, pinfo, ajp13_tree, cd);

  } else if (mag == 0x4142) {

    display_rsp(tvb, pinfo, ajp13_tree);

  }
}



/* given the first chunk of the AJP13 pdu, extract out and return the
 * packet length. see comments in packet-tcp.c:tcp_dissect_pdus().
 */
static guint
get_ajp13_pdu_len(tvbuff_t *tvb, int offset)
{
  guint16 magic;
  guint16 plen;
  magic = tvb_get_ntohs(tvb, offset);
  plen = tvb_get_ntohs(tvb, offset+2);
  plen += 4;
  return plen;
}



/* Code to actually dissect the packets.
 */
static void
dissect_ajp13(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
  /* Set up structures needed to add the protocol subtree and manage it
   */
  tcp_dissect_pdus(tvb, pinfo, tree,
                   TRUE,                   /* desegment or not   */
                   4,                      /* magic + length */
                   get_ajp13_pdu_len,      /* use first 4, calc data len */
                   dissect_ajp13_tcp_pdu); /* the naive dissector */
}



static void
ajp13_init_protocol(void)
{
  if (ajp13_conv_data_chunk)
    g_mem_chunk_destroy(ajp13_conv_data_chunk);
  if (ajp13_frame_data_chunk)
    g_mem_chunk_destroy(ajp13_frame_data_chunk);

  ajp13_conv_data_chunk = g_mem_chunk_new("ajp13_conv_data_chunk",
					  sizeof(ajp13_conv_data),
					  ajp13_packet_init_count * sizeof(ajp13_conv_data),
					  G_ALLOC_ONLY);

  ajp13_frame_data_chunk = g_mem_chunk_new("ajp13_frame_data_chunk",
					   sizeof(ajp13_frame_data),
					   ajp13_packet_init_count * sizeof(ajp13_frame_data),
					   G_ALLOC_ONLY);
}

void
proto_register_ajp13(void)
{
  static hf_register_info hf[] = {
    { &hf_ajp13_magic,
      { "Magic",  "ajp13.magic", FT_BYTES, BASE_HEX, NULL, 0x0, "Magic Number",
        HFILL }
    },
    { &hf_ajp13_len,
      { "Length",  "ajp13.len", FT_UINT16, BASE_DEC, NULL, 0x0, "Data Length",
        HFILL }
    },
    { &hf_ajp13_code,
      { "Code",  "ajp13.code", FT_STRING, BASE_DEC, NULL, 0x0, "Type Code",
         HFILL }
    },
    { &hf_ajp13_method,
      { "Method",  "ajp13.method", FT_STRING, BASE_DEC, NULL, 0x0, "HTTP Method",
        HFILL }
    },
    { &hf_ajp13_ver,
      { "Version",  "ajp13.ver", FT_STRING, BASE_DEC, NULL, 0x0, "HTTP Version",
        HFILL }
    },
    { &hf_ajp13_uri,
      { "URI",  "ajp13.uri", FT_STRING, BASE_DEC, NULL, 0x0, "HTTP URI",
        HFILL }
    },
    { &hf_ajp13_raddr,
      { "RADDR",  "ajp13.raddr", FT_STRING, BASE_DEC, NULL, 0x0, "Remote Address",
        HFILL }
    },
    { &hf_ajp13_rhost,
      { "RHOST",  "ajp13.rhost", FT_STRING, BASE_DEC, NULL, 0x0, "Remote Host",
        HFILL }
    },
    { &hf_ajp13_srv,
      { "SRV",  "ajp13.srv", FT_STRING, BASE_DEC, NULL, 0x0, "Server",
        HFILL }
    },
    { &hf_ajp13_port,
      { "PORT",  "ajp13.port", FT_UINT16, BASE_DEC, NULL, 0x0, "Port",
        HFILL }
    },
    { &hf_ajp13_sslp,
      { "SSLP",  "ajp13.sslp", FT_UINT8, BASE_DEC, NULL, 0x0, "Is SSL?",
        HFILL }
    },
    { &hf_ajp13_nhdr,
      { "NHDR",  "ajp13.nhdr", FT_UINT16, BASE_DEC, NULL, 0x0, "Num Headers",
        HFILL }
    },
    { &hf_ajp13_hname,
      { "HNAME",  "ajp13.hname", FT_STRING, BASE_DEC, NULL, 0x0, "Header Name",
        HFILL }
    },
    { &hf_ajp13_hval,
      { "HVAL",  "ajp13.hval", FT_STRING, BASE_DEC, NULL, 0x0, "Header Value",
        HFILL }
    },
    { &hf_ajp13_rlen,
      { "RLEN",  "ajp13.rlen", FT_UINT16, BASE_DEC, NULL, 0x0, "Requested Length",
        HFILL }
    },
    { &hf_ajp13_reusep,
      { "REUSEP",  "ajp13.reusep", FT_UINT8, BASE_DEC, NULL, 0x0, "Reuse Connection?",
        HFILL }
    },
    { &hf_ajp13_rstatus,
      { "RSTATUS",  "ajp13.rstatus", FT_UINT16, BASE_DEC, NULL, 0x0, "HTTP Status Code",
        HFILL }
    },
    { &hf_ajp13_rsmsg,
      { "RSMSG",  "ajp13.rmsg", FT_STRING, BASE_DEC, NULL, 0x0, "HTTP Status Message",
        HFILL }
    },
    { &hf_ajp13_data,
      { "Data",  "ajp13.data", FT_STRING, BASE_DEC, NULL, 0x0, "Data",
        HFILL }
    },
  };

  static gint *ett[] = {
    &ett_ajp13,
  };

  /* Register the protocol name and description
   */
  proto_ajp13 = proto_register_protocol("Apache JServ Protocol v1.3", "AJP13", "ajp13");

  proto_register_field_array(proto_ajp13, hf, array_length(hf));
  proto_register_subtree_array(ett, array_length(ett));

  register_init_routine(&ajp13_init_protocol);
}



void
proto_reg_handoff_ajp13(void)
{
  dissector_handle_t ajp13_handle;
  ajp13_handle = create_dissector_handle(dissect_ajp13, proto_ajp13);
  dissector_add("tcp.port", 8009, ajp13_handle);
}
