path: root/source4/libcli/nmblib.c

/* 
   Unix SMB/CIFS implementation.
   NBT netbios library routines
   Copyright (C) Andrew Tridgell 1994-1998
   
   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., 675 Mass Ave, Cambridge, MA 02139, USA.
   
*/

#include "includes.h"
#include "system/network.h"
#include "system/time.h"
#include "system/iconv.h"

static const struct opcode_names {
	const char *nmb_opcode_name;
	int opcode;
} nmb_header_opcode_names[] = {
	{"Query",           0 },
	{"Registration",      5 },
	{"Release",           6 },
	{"WACK",              7 },
	{"Refresh",           8 },
	{"Refresh(altcode)",  9 },
	{"Multi-homed Registration", 15 },
	{0, -1 }
};

/****************************************************************************
 * Lookup a nmb opcode name.
 ****************************************************************************/
static const char *lookup_opcode_name( int opcode )
{
  const struct opcode_names *op_namep;
  int i;

  for(i = 0; nmb_header_opcode_names[i].nmb_opcode_name != 0; i++) {
    op_namep = &nmb_header_opcode_names[i];
    if(opcode == op_namep->opcode)
      return op_namep->nmb_opcode_name;
  }
  return "<unknown opcode>";
}

/****************************************************************************
  print out a res_rec structure
  ****************************************************************************/
static void debug_nmb_res_rec(struct res_rec *res, const char *hdr)
{
  int i, j;

  DEBUGADD( 4, ( "    %s: nmb_name=%s rr_type=%d rr_class=%d ttl=%d\n",
                 hdr,
                 nmb_namestr(&res->rr_name),
                 res->rr_type,
                 res->rr_class,
                 res->ttl ) );

  if( res->rdlength == 0 || res->rdata == NULL )
    return;

  for (i = 0; i < res->rdlength; i+= 16)
    {
      DEBUGADD(4, ("    %s %3x char ", hdr, i));

      for (j = 0; j < 16; j++)
	{
	  uint8_t x = res->rdata[i+j];
	  if (x < 32 || x > 127) x = '.';
	  
	  if (i+j >= res->rdlength) break;
	  DEBUGADD(4, ("%c", x));
	}
      
      DEBUGADD(4, ("   hex "));

      for (j = 0; j < 16; j++)
	{
	  if (i+j >= res->rdlength) break;
	  DEBUGADD(4, ("%02X", (uint8_t)res->rdata[i+j]));
	}
      
      DEBUGADD(4, ("\n"));
    }
}

/****************************************************************************
  process a nmb packet
  ****************************************************************************/
void debug_nmb_packet(struct packet_struct *p)
{
  struct nmb_packet *nmb = &p->packet.nmb;

  if (DEBUGLVL(4)) {
	  DEBUG(4, ("nmb packet from %s(%d) header: id=%d opcode=%s(%d) response=%s\n",
		    sys_inet_ntoa(p->ip), p->port,
		    nmb->header.name_trn_id,
		    lookup_opcode_name(nmb->header.opcode),
		    nmb->header.opcode,
		    BOOLSTR(nmb->header.response)));
	  DEBUG(4, ("    header: flags: bcast=%s rec_avail=%s rec_des=%s trunc=%s auth=%s\n",
		    BOOLSTR(nmb->header.nm_flags.bcast),
		    BOOLSTR(nmb->header.nm_flags.recursion_available),
		    BOOLSTR(nmb->header.nm_flags.recursion_desired),
		    BOOLSTR(nmb->header.nm_flags.trunc),
		    BOOLSTR(nmb->header.nm_flags.authoritative)));
	  DEBUG(4, ("    header: rcode=%d qdcount=%d ancount=%d nscount=%d arcount=%d\n",
		    nmb->header.rcode,
		    nmb->header.qdcount,
		    nmb->header.ancount,
		    nmb->header.nscount,
		    nmb->header.arcount));
    }

  if (nmb->header.qdcount)
    {
      DEBUGADD( 4, ( "    question: q_name=%s q_type=%d q_class=%d\n",
                     nmb_namestr(&nmb->question.question_name),
                     nmb->question.question_type,
                     nmb->question.question_class) );
    }

  if (nmb->answers && nmb->header.ancount)
    {
      debug_nmb_res_rec(nmb->answers,"answers");
    }
  if (nmb->nsrecs && nmb->header.nscount)
    {
      debug_nmb_res_rec(nmb->nsrecs,"nsrecs");
    }
  if (nmb->additional && nmb->header.arcount)
    {
      debug_nmb_res_rec(nmb->additional,"additional");
    }
}

/*******************************************************************
  handle "compressed" name pointers
  ******************************************************************/
static BOOL handle_name_ptrs(uint8_t *ubuf,int *offset,int length,
			     BOOL *got_pointer,int *ret)
{
  int loop_count=0;
  
  while ((ubuf[*offset] & 0xC0) == 0xC0) {
    if (!*got_pointer) (*ret) += 2;
    (*got_pointer)=True;
    (*offset) = ((ubuf[*offset] & ~0xC0)<<8) | ubuf[(*offset)+1];
    if (loop_count++ == 10 || (*offset) < 0 || (*offset)>(length-2)) {
      return(False);
    }
  }
  return(True);
}

/*******************************************************************
  parse a nmb name from "compressed" format to something readable
  return the space taken by the name, or 0 if the name is invalid
  ******************************************************************/
static int parse_nmb_name(char *inbuf,int ofs,int length, struct nmb_name *name)
{
  int m,n=0;
  uint8_t *ubuf = (uint8_t *)inbuf;
  int ret = 0;
  BOOL got_pointer=False;
  int loop_count=0;
  int offset = ofs;

  if (length - offset < 2)
    return(0);  

  /* handle initial name pointers */
  if (!handle_name_ptrs(ubuf,&offset,length,&got_pointer,&ret))
    return(0);
  
  m = ubuf[offset];

  if (!m)
    return(0);
  if ((m & 0xC0) || offset+m+2 > length)
    return(0);

  memset((char *)name,'\0',sizeof(*name));

  /* the "compressed" part */
  if (!got_pointer)
    ret += m + 2;
  offset++;
  while (m > 0) {
    uint8_t c1,c2;
    c1 = ubuf[offset++]-'A';
    c2 = ubuf[offset++]-'A';
    if ((c1 & 0xF0) || (c2 & 0xF0) || (n > sizeof(name->name)-1))
      return(0);
    name->name[n++] = (c1<<4) | c2;
    m -= 2;
  }
  name->name[n] = 0;

  if (n==16) {
    /* parse out the name type, 
       its always in the 16th byte of the name */
    name->name_type = ((uint8_t)name->name[15]) & 0xff;
  
    /* remove trailing spaces */
    name->name[15] = 0;
    n = 14;
    while (n && name->name[n]==' ')
      name->name[n--] = 0;  
  }

  /* now the domain parts (if any) */
  n = 0;
  while (ubuf[offset]) {
    /* we can have pointers within the domain part as well */
    if (!handle_name_ptrs(ubuf,&offset,length,&got_pointer,&ret))
      return(0);

    m = ubuf[offset];
    /*
     * Don't allow null domain parts.
     */
    if (!m)
      return(0);
    if (!got_pointer)
      ret += m+1;
    if (n)
      name->scope[n++] = '.';
    if (m+2+offset>length || n+m+1>sizeof(name->scope))
      return(0);
    offset++;
    while (m--)
      name->scope[n++] = (char)ubuf[offset++];

    /*
     * Watch for malicious loops.
     */
    if (loop_count++ == 10)
      return 0;
  }
  name->scope[n++] = 0;  

  return(ret);
}


/*******************************************************************
  put a compressed nmb name into a buffer. return the length of the
  compressed name

  compressed names are really weird. The "compression" doubles the
  size. The idea is that it also means that compressed names conform
  to the doman name system. See RFC1002.
  ******************************************************************/
static int put_nmb_name(char *buf,int offset,struct nmb_name *name)
{
  int ret,m;
  fstring buf1;
  char *p;

  if (strcmp(name->name,"*") == 0) {
    /* special case for wildcard name */
    memset(buf1,'\0',20);
    buf1[0] = '*';
    buf1[15] = name->name_type;
  } else {
    slprintf(buf1, sizeof(buf1) - 1,"%-15.15s%c",name->name,name->name_type);
  }

  buf[offset] = 0x20;

  ret = 34;

  for (m=0;m<16;m++) {
    buf[offset+1+2*m] = 'A' + ((buf1[m]>>4)&0xF);
    buf[offset+2+2*m] = 'A' + (buf1[m]&0xF);
  }
  offset += 33;

  buf[offset] = 0;

  if (name->scope[0]) {
    /* XXXX this scope handling needs testing */
    ret += strlen(name->scope) + 1;
    pstrcpy(&buf[offset+1],name->scope);  
  
    p = &buf[offset+1];
    while ((p = strchr_m(p,'.'))) {
      buf[offset] = PTR_DIFF(p,&buf[offset+1]);
      offset += (buf[offset] + 1);
      p = &buf[offset+1];
    }
    buf[offset] = strlen(&buf[offset+1]);
  }

  return(ret);
}

/*******************************************************************
  useful for debugging messages
  ******************************************************************/
char *nmb_namestr(struct nmb_name *n)
{
  static int i=0;
  static fstring ret[4];
  char *p = ret[i];

  if (!n->scope[0])
    slprintf(p,sizeof(fstring)-1, "%s<%02x>",n->name,n->name_type);
  else
    slprintf(p,sizeof(fstring)-1, "%s<%02x>.%s",n->name,n->name_type,n->scope);

  i = (i+1)%4;
  return(p);
}

/*******************************************************************
  allocate and parse some resource records
  ******************************************************************/
static BOOL parse_alloc_res_rec(char *inbuf,int *offset,int length,
				struct res_rec **recs, int count)
{
  int i;
  *recs = (struct res_rec *)malloc(sizeof(**recs)*count);
  if (!*recs) return(False);

  memset((char *)*recs,'\0',sizeof(**recs)*count);

  for (i=0;i<count;i++) {
    int l = parse_nmb_name(inbuf,*offset,length,&(*recs)[i].rr_name);
    (*offset) += l;
    if (!l || (*offset)+10 > length) {
      SAFE_FREE(*recs);
      return(False);
    }
    (*recs)[i].rr_type = RSVAL(inbuf,(*offset));
    (*recs)[i].rr_class = RSVAL(inbuf,(*offset)+2);
    (*recs)[i].ttl = RIVAL(inbuf,(*offset)+4);
    (*recs)[i].rdlength = RSVAL(inbuf,(*offset)+8);
    (*offset) += 10;
    if ((*recs)[i].rdlength>sizeof((*recs)[i].rdata) || 
	(*offset)+(*recs)[i].rdlength > length) {
      SAFE_FREE(*recs);
      return(False);
    }
    memcpy((*recs)[i].rdata,inbuf+(*offset),(*recs)[i].rdlength);
    (*offset) += (*recs)[i].rdlength;    
  }
  return(True);
}

/*******************************************************************
  put a resource record into a packet
  ******************************************************************/
static int put_res_rec(char *buf,int offset,struct res_rec *recs,int count)
{
  int ret=0;
  int i;

  for (i=0;i<count;i++) {
    int l = put_nmb_name(buf,offset,&recs[i].rr_name);
    offset += l;
    ret += l;
    RSSVAL(buf,offset,recs[i].rr_type);
    RSSVAL(buf,offset+2,recs[i].rr_class);
    RSIVAL(buf,offset+4,recs[i].ttl);
    RSSVAL(buf,offset+8,recs[i].rdlength);
    memcpy(buf+offset+10,recs[i].rdata,recs[i].rdlength);
    offset += 10+recs[i].rdlength;
    ret += 10+recs[i].rdlength;
  }

  return(ret);
}

/*******************************************************************
  put a compressed name pointer record into a packet
  ******************************************************************/
static int put_compressed_name_ptr(uint8_t *buf,int offset,struct res_rec *rec,int ptr_offset)
{  
  int ret=0;
  buf[offset] = (0xC0 | ((ptr_offset >> 8) & 0xFF));
  buf[offset+1] = (ptr_offset & 0xFF);
  offset += 2;
  ret += 2;
  RSSVAL(buf,offset,rec->rr_type);
  RSSVAL(buf,offset+2,rec->rr_class);
  RSIVAL(buf,offset+4,rec->ttl);
  RSSVAL(buf,offset+8,rec->rdlength);
  memcpy(buf+offset+10,rec->rdata,rec->rdlength);
  offset += 10+rec->rdlength;
  ret += 10+rec->rdlength;
    
  return(ret);
}

/*******************************************************************
  parse a dgram packet. Return False if the packet can't be parsed 
  or is invalid for some reason, True otherwise 

  this is documented in section 4.4.1 of RFC1002
  ******************************************************************/
static BOOL parse_dgram(char *inbuf,int length,struct dgram_packet *dgram)
{
  int offset;
  int flags;

  memset((char *)dgram,'\0',sizeof(*dgram));

  if (length < 14) return(False);

  dgram->header.msg_type = CVAL(inbuf,0);
  flags = CVAL(inbuf,1);
  dgram->header.flags.node_type = (enum node_type)((flags>>2)&3);
  if (flags & 1) dgram->header.flags.more = True;
  if (flags & 2) dgram->header.flags.first = True;
  dgram->header.dgm_id = RSVAL(inbuf,2);
  putip((char *)&dgram->header.source_ip,inbuf+4);
  dgram->header.source_port = RSVAL(inbuf,8);
  dgram->header.dgm_length = RSVAL(inbuf,10);
  dgram->header.packet_offset = RSVAL(inbuf,12);

  offset = 14;

  if (dgram->header.msg_type == 0x10 ||
      dgram->header.msg_type == 0x11 ||
      dgram->header.msg_type == 0x12) {      
    offset += parse_nmb_name(inbuf,offset,length,&dgram->source_name);
    offset += parse_nmb_name(inbuf,offset,length,&dgram->dest_name);
  }

  if (offset >= length || (length-offset > sizeof(dgram->data))) 
    return(False);

  dgram->datasize = length-offset;
  memcpy(dgram->data,inbuf+offset,dgram->datasize);

  return(True);
}


/*******************************************************************
  parse a nmb packet. Return False if the packet can't be parsed 
  or is invalid for some reason, True otherwise 
  ******************************************************************/
static BOOL parse_nmb(char *inbuf,int length,struct nmb_packet *nmb)
{
  int nm_flags,offset;

  memset((char *)nmb,'\0',sizeof(*nmb));

  if (length < 12) return(False);

  /* parse the header */
  nmb->header.name_trn_id = RSVAL(inbuf,0);

  DEBUG(10,("parse_nmb: packet id = %d\n", nmb->header.name_trn_id));

  nmb->header.opcode = (CVAL(inbuf,2) >> 3) & 0xF;
  nmb->header.response = ((CVAL(inbuf,2)>>7)&1)?True:False;
  nm_flags = ((CVAL(inbuf,2) & 0x7) << 4) + (CVAL(inbuf,3)>>4);
  nmb->header.nm_flags.bcast = (nm_flags&1)?True:False;
  nmb->header.nm_flags.recursion_available = (nm_flags&8)?True:False;
  nmb->header.nm_flags.recursion_desired = (nm_flags&0x10)?True:False;
  nmb->header.nm_flags.trunc = (nm_flags&0x20)?True:False;
  nmb->header.nm_flags.authoritative = (nm_flags&0x40)?True:False;  
  nmb->header.rcode = CVAL(inbuf,3) & 0xF;
  nmb->header.qdcount = RSVAL(inbuf,4);
  nmb->header.ancount = RSVAL(inbuf,6);
  nmb->header.nscount = RSVAL(inbuf,8);
  nmb->header.arcount = RSVAL(inbuf,10);
  
  if (nmb->header.qdcount) {
    offset = parse_nmb_name(inbuf,12,length,&nmb->question.question_name);
    if (!offset) return(False);

    if (length - (12+offset) < 4) return(False);
    nmb->question.question_type = RSVAL(inbuf,12+offset);
    nmb->question.question_class = RSVAL(inbuf,12+offset+2);

    offset += 12+4;
  } else {
    offset = 12;
  }

  /* and any resource records */
  if (nmb->header.ancount && 
      !parse_alloc_res_rec(inbuf,&offset,length,&nmb->answers,
			   nmb->header.ancount))
    return(False);

  if (nmb->header.nscount && 
      !parse_alloc_res_rec(inbuf,&offset,length,&nmb->nsrecs,
			   nmb->header.nscount))
    return(False);
  
  if (nmb->header.arcount && 
      !parse_alloc_res_rec(inbuf,&offset,length,&nmb->additional,
			   nmb->header.arcount))
    return(False);

  return(True);
}

/*******************************************************************
  'Copy constructor' for an nmb packet
  ******************************************************************/
static struct packet_struct *copy_nmb_packet(struct packet_struct *packet)
{  
  struct nmb_packet *nmb;
  struct nmb_packet *copy_nmb;
  struct packet_struct *pkt_copy;

  if(( pkt_copy = (struct packet_struct *)malloc(sizeof(*packet))) == NULL)
  {
    DEBUG(0,("copy_nmb_packet: malloc fail.\n"));
    return NULL;
  }

  /* Structure copy of entire thing. */

  *pkt_copy = *packet;

  /* Ensure this copy is not locked. */
  pkt_copy->locked = False;

  /* Ensure this copy has no resource records. */
  nmb = &packet->packet.nmb;
  copy_nmb = &pkt_copy->packet.nmb;

  copy_nmb->answers = NULL;
  copy_nmb->nsrecs = NULL;
  copy_nmb->additional = NULL;

  /* Now copy any resource records. */

  if (nmb->answers)
  {
    if((copy_nmb->answers = malloc_array_p(struct res_rec, nmb->header.ancount)) == NULL)
      goto free_and_exit;
    memcpy((char *)copy_nmb->answers, (char *)nmb->answers, 
           nmb->header.ancount * sizeof(struct res_rec));
  }
  if (nmb->nsrecs)
  {
    if((copy_nmb->nsrecs = malloc_array_p(struct res_rec, nmb->header.nscount)) == NULL)
      goto free_and_exit;
    memcpy((char *)copy_nmb->nsrecs, (char *)nmb->nsrecs, 
           nmb->header.nscount * sizeof(struct res_rec));
  }
  if (nmb->additional)
  {
    if((copy_nmb->additional = malloc_array_p(struct res_rec, nmb->header.arcount)) == NULL)
      goto free_and_exit;
    memcpy((char *)copy_nmb->additional, (char *)nmb->additional, 
           nmb->header.arcount * sizeof(struct res_rec));
  }

  return pkt_copy;

free_and_exit:

  SAFE_FREE(copy_nmb->answers);
  SAFE_FREE(copy_nmb->nsrecs);
  SAFE_FREE(copy_nmb->additional);
  SAFE_FREE(pkt_copy);

  DEBUG(0,("copy_nmb_packet: malloc fail in resource records.\n"));
  return NULL;
}

/*******************************************************************
  'Copy constructor' for a dgram packet
  ******************************************************************/
static struct packet_struct *copy_dgram_packet(struct packet_struct *packet)
{ 
  struct packet_struct *pkt_copy;

  if(( pkt_copy = malloc_p(struct packet_struct)) == NULL)
  {
    DEBUG(0,("copy_dgram_packet: malloc fail.\n"));
    return NULL;
  }

  /* Structure copy of entire thing. */

  *pkt_copy = *packet;

  /* Ensure this copy is not locked. */
  pkt_copy->locked = False;

  /* There are no additional pointers in a dgram packet,
     we are finished. */
  return pkt_copy;
}

/*******************************************************************
  'Copy constructor' for a generic packet
  ******************************************************************/
struct packet_struct *copy_packet(struct packet_struct *packet)
{  
  if(packet->packet_type == NMB_PACKET)
    return copy_nmb_packet(packet);
  else if (packet->packet_type == DGRAM_PACKET)
    return copy_dgram_packet(packet);
  return NULL;
}
 
/*******************************************************************
  free up any resources associated with an nmb packet
  ******************************************************************/
static void free_nmb_packet(struct nmb_packet *nmb)
{  
  SAFE_FREE(nmb->answers);
  SAFE_FREE(nmb->nsrecs);
  SAFE_FREE(nmb->additional);
}

/*******************************************************************
  free up any resources associated with a dgram packet
  ******************************************************************/
static void free_dgram_packet(struct dgram_packet *nmb)
{  
  /* We have nothing to do for a dgram packet. */
}

/*******************************************************************
  free up any resources associated with a packet
  ******************************************************************/
void free_packet(struct packet_struct *packet)
{  
	if (packet->locked) 
		return;
	if (packet->packet_type == NMB_PACKET)
		free_nmb_packet(&packet->packet.nmb);
	else if (packet->packet_type == DGRAM_PACKET)
		free_dgram_packet(&packet->packet.dgram);
	ZERO_STRUCTPN(packet);
	SAFE_FREE(packet);
}

/*******************************************************************
parse a packet buffer into a packet structure
  ******************************************************************/
struct packet_struct *parse_packet(char *buf,int length,
				   enum packet_type packet_type)
{
	struct packet_struct *p;
	BOOL ok=False;

	p = malloc_p(struct packet_struct);
	if (!p) return(NULL);

	p->next = NULL;
	p->prev = NULL;
	p->locked = False;
	p->timestamp = time(NULL);
	p->packet_type = packet_type;

	switch (packet_type) {
	case NMB_PACKET:
		ok = parse_nmb(buf,length,&p->packet.nmb);
		break;
		
	case DGRAM_PACKET:
		ok = parse_dgram(buf,length,&p->packet.dgram);
		break;
	}

	if (!ok) {
		free_packet(p);
		return NULL;
	}

	return p;
}

/*******************************************************************
  read a packet from a socket and parse it, returning a packet ready
  to be used or put on the queue. This assumes a UDP socket
  ******************************************************************/
struct packet_struct *read_packet(int fd,enum packet_type packet_type)
{
	struct packet_struct *packet;
	char buf[MAX_DGRAM_SIZE];
	int length;
	struct ipv4_addr addr;
	int port;
	
	length = read_udp_socket(fd, buf, sizeof(buf), &addr, &port);
	if (length < MIN_DGRAM_SIZE) return(NULL);
	
	packet = parse_packet(buf, length, packet_type);
	if (!packet) return NULL;

	packet->fd = fd;
	packet->ip = addr;
	packet->port = port;
	
	DEBUG(5,("Received a packet of len %d from (%s) port %d\n",
		 length, sys_inet_ntoa(packet->ip), packet->port));
	
	return packet;
}
					 

/*******************************************************************
  send a udp packet on a already open socket
  ******************************************************************/
static BOOL send_udp(int fd,char *buf,int len,struct ipv4_addr ip,int port)
{
  BOOL ret = False;
  int i;
  struct sockaddr_in sock_out;

  /* set the address and port */
  memset((char *)&sock_out,'\0',sizeof(sock_out));
  putip((char *)&sock_out.sin_addr,(char *)&ip);
  sock_out.sin_port = htons( port );
  sock_out.sin_family = AF_INET;
  
  DEBUG( 5, ( "Sending a packet of len %d to (%s) on port %d\n",
	      len, sys_inet_ntoa(ip), port ) );

  /*
   * Patch to fix asynch error notifications from Linux kernel.
   */
	
  for (i = 0; i < 5; i++) {
    ret = (sendto(fd,buf,len,0,(struct sockaddr *)&sock_out, sizeof(sock_out)) >= 0);
    if (ret || errno != ECONNREFUSED)
      break;
  }

  if (!ret)
    DEBUG(0,("Packet send failed to %s(%d) ERRNO=%s\n",
	     sys_inet_ntoa(ip),port,strerror(errno)));

  return(ret);
}

/*******************************************************************
  build a dgram packet ready for sending

  XXXX This currently doesn't handle packets too big for one
  datagram. It should split them and use the packet_offset, more and
  first flags to handle the fragmentation. Yuck.

    [...but it isn't clear that we would ever need to send a
    a fragmented NBT Datagram.  The IP layer does its own
    fragmentation to ensure that messages can fit into the path
    MTU.  It *is* important to be able to receive and rebuild
    fragmented NBT datagrams, just in case someone out there
    really has implemented this 'feature'.  crh -)------ ]

  ******************************************************************/
static int build_dgram(char *buf,struct packet_struct *p)
{
  struct dgram_packet *dgram = &p->packet.dgram;
  uint8_t *ubuf = (uint8_t *)buf;
  int offset=0;

  /* put in the header */
  ubuf[0] = dgram->header.msg_type;
  ubuf[1] = (((int)dgram->header.flags.node_type)<<2);
  if (dgram->header.flags.more) ubuf[1] |= 1;
  if (dgram->header.flags.first) ubuf[1] |= 2;
  RSSVAL(ubuf,2,dgram->header.dgm_id);
  putip(ubuf+4,(char *)&dgram->header.source_ip);
  RSSVAL(ubuf,8,dgram->header.source_port);
  RSSVAL(ubuf,12,dgram->header.packet_offset);

  offset = 14;

  if (dgram->header.msg_type == 0x10 ||
      dgram->header.msg_type == 0x11 ||
      dgram->header.msg_type == 0x12) {      
    offset += put_nmb_name((char *)ubuf,offset,&dgram->source_name);
    offset += put_nmb_name((char *)ubuf,offset,&dgram->dest_name);
  }

  memcpy(ubuf+offset,dgram->data,dgram->datasize);
  offset += dgram->datasize;

  /* automatically set the dgm_length
   * NOTE: RFC1002 says the dgm_length does *not*
   *       include the fourteen-byte header. crh
   */
  dgram->header.dgm_length = (offset - 14);
  RSSVAL(ubuf,10,dgram->header.dgm_length); 

  return(offset);
}

/*******************************************************************
 Build a nmb name
*******************************************************************/

void make_nmb_name( struct nmb_name *n, const char *name, int type)
{
	memset( (char *)n, '\0', sizeof(struct nmb_name) );
	push_ascii(n->name, name, 16, STR_TERMINATE|STR_UPPER);
	n->name_type = (uint_t)type & 0xFF;
	StrnCpy( n->scope, lp_netbios_scope(), 63 );
	strupper( n->scope );
}

/*******************************************************************
  Compare two nmb names
  ******************************************************************/

BOOL nmb_name_equal(struct nmb_name *n1, struct nmb_name *n2)
{
  return ((n1->name_type == n2->name_type) &&
         strequal(n1->name ,n2->name ) &&
         strequal(n1->scope,n2->scope));
}

/*******************************************************************
  build a nmb packet ready for sending

  XXXX this currently relies on not being passed something that expands
  to a packet too big for the buffer. Eventually this should be
  changed to set the trunc bit so the receiver can request the rest
  via tcp (when that becomes supported)
  ******************************************************************/
static int build_nmb(char *buf,struct packet_struct *p)
{
  struct nmb_packet *nmb = &p->packet.nmb;
  uint8_t *ubuf = (uint8_t *)buf;
  int offset=0;

  /* put in the header */
  RSSVAL(ubuf,offset,nmb->header.name_trn_id);
  ubuf[offset+2] = (nmb->header.opcode & 0xF) << 3;
  if (nmb->header.response) ubuf[offset+2] |= (1<<7);
  if (nmb->header.nm_flags.authoritative && 
      nmb->header.response) ubuf[offset+2] |= 0x4;
  if (nmb->header.nm_flags.trunc) ubuf[offset+2] |= 0x2;
  if (nmb->header.nm_flags.recursion_desired) ubuf[offset+2] |= 0x1;
  if (nmb->header.nm_flags.recursion_available &&
      nmb->header.response) ubuf[offset+3] |= 0x80;
  if (nmb->header.nm_flags.bcast) ubuf[offset+3] |= 0x10;
  ubuf[offset+3] |= (nmb->header.rcode & 0xF);

  RSSVAL(ubuf,offset+4,nmb->header.qdcount);
  RSSVAL(ubuf,offset+6,nmb->header.ancount);
  RSSVAL(ubuf,offset+8,nmb->header.nscount);
  RSSVAL(ubuf,offset+10,nmb->header.arcount);
  
  offset += 12;
  if (nmb->header.qdcount) {
    /* XXXX this doesn't handle a qdcount of > 1 */
    offset += put_nmb_name((char *)ubuf,offset,&nmb->question.question_name);
    RSSVAL(ubuf,offset,nmb->question.question_type);
    RSSVAL(ubuf,offset+2,nmb->question.question_class);
    offset += 4;
  }

  if (nmb->header.ancount)
    offset += put_res_rec((char *)ubuf,offset,nmb->answers,
			  nmb->header.ancount);

  if (nmb->header.nscount)
    offset += put_res_rec((char *)ubuf,offset,nmb->nsrecs,
			  nmb->header.nscount);

  /*
   * The spec says we must put compressed name pointers
   * in the following outgoing packets :
   * NAME_REGISTRATION_REQUEST, NAME_REFRESH_REQUEST,
   * NAME_RELEASE_REQUEST.
   */

  if((nmb->header.response == False) &&
     ((nmb->header.opcode == NMB_NAME_REG_OPCODE) ||
      (nmb->header.opcode == NMB_NAME_RELEASE_OPCODE) ||
      (nmb->header.opcode == NMB_NAME_REFRESH_OPCODE_8) ||
      (nmb->header.opcode == NMB_NAME_REFRESH_OPCODE_9) ||
      (nmb->header.opcode == NMB_NAME_MULTIHOMED_REG_OPCODE)) &&
     (nmb->header.arcount == 1)) {

    offset += put_compressed_name_ptr(ubuf,offset,nmb->additional,12);

  } else if (nmb->header.arcount) {
    offset += put_res_rec((char *)ubuf,offset,nmb->additional,
			  nmb->header.arcount);  
  }
  return(offset);
}


/*******************************************************************
linearise a packet
  ******************************************************************/
int build_packet(char *buf, struct packet_struct *p)
{
	int len = 0;

	switch (p->packet_type) {
	case NMB_PACKET:
		len = build_nmb(buf,p);
		break;

	case DGRAM_PACKET:
		len = build_dgram(buf,p);
		break;
	}

	return len;
}

/*******************************************************************
  send a packet_struct
  ******************************************************************/
BOOL send_packet(struct packet_struct *p)
{
  char buf[1024];
  int len=0;

  memset(buf,'\0',sizeof(buf));

  len = build_packet(buf, p);

  if (!len) return(False);

  return(send_udp(p->fd,buf,len,p->ip,p->port));
}

/****************************************************************************
  receive a packet with timeout on a open UDP filedescriptor
  The timeout is in milliseconds
  ***************************************************************************/
struct packet_struct *receive_packet(int fd,enum packet_type type,int t)
{
	fd_set fds;
	struct timeval timeout;
	int ret;

	FD_ZERO(&fds);
	FD_SET(fd,&fds);
	timeout.tv_sec = t/1000;
	timeout.tv_usec = 1000*(t%1000);

	if ((ret = sys_select_intr(fd+1,&fds,NULL,NULL,&timeout)) == -1) {
		/* errno should be EBADF or EINVAL. */
		DEBUG(0,("select returned -1, errno = %s (%d)\n", strerror(errno), errno));
		return NULL;
	}

	if (ret == 0) /* timeout */
		return NULL;

	if (FD_ISSET(fd,&fds)) 
		return(read_packet(fd,type));
	
	return(NULL);
}


/****************************************************************************
  receive a UDP/137 packet either via UDP or from the unexpected packet
  queue. The packet must be a reply packet and have the specified trn_id
  The timeout is in milliseconds
  ***************************************************************************/
struct packet_struct *receive_nmb_packet(int fd, int t, int trn_id)
{
	struct packet_struct *p;

	p = receive_packet(fd, NMB_PACKET, t);

	if (p && p->packet.nmb.header.response &&
	    p->packet.nmb.header.name_trn_id == trn_id) {
		return p;
	}
	if (p) free_packet(p);

	/* try the unexpected packet queue */
	return receive_unexpected(NMB_PACKET, trn_id, NULL);
}

/****************************************************************************
  receive a UDP/138 packet either via UDP or from the unexpected packet
  queue. The packet must be a reply packet and have the specified mailslot name
  The timeout is in milliseconds
  ***************************************************************************/
struct packet_struct *receive_dgram_packet(int fd, int t, const char *mailslot_name)
{
	struct packet_struct *p;

	p = receive_packet(fd, DGRAM_PACKET, t);

	if (p && match_mailslot_name(p, mailslot_name)) {
		return p;
	}
	if (p) free_packet(p);

	/* try the unexpected packet queue */
	return receive_unexpected(DGRAM_PACKET, 0, mailslot_name);
}


/****************************************************************************
 see if a datagram has the right mailslot name
***************************************************************************/
BOOL match_mailslot_name(struct packet_struct *p, const char *mailslot_name)
{
	struct dgram_packet *dgram = &p->packet.dgram;
	char *buf;

	buf = &dgram->data[0];
	buf -= 4;

	buf = smb_buf(buf);

	if (memcmp(buf, mailslot_name, strlen(mailslot_name)+1) == 0) {
		return True;
	}

	return False;
}


/****************************************************************************
return the number of bits that match between two 4 character buffers
  ***************************************************************************/
int matching_quad_bits(uint8_t *p1, uint8_t *p2)
{
	int i, j, ret = 0;
	for (i=0; i<4; i++) {
		if (p1[i] != p2[i]) break;
		ret += 8;
	}

	if (i==4) return ret;

	for (j=0; j<8; j++) {
		if ((p1[i] & (1<<(7-j))) != (p2[i] & (1<<(7-j)))) break;
		ret++;
	}	
	
	return ret;
}


static uint8_t sort_ip[4];

/****************************************************************************
compare two query reply records
  ***************************************************************************/
static int name_query_comp(uint8_t *p1, uint8_t *p2)
{
	return matching_quad_bits(p2+2, sort_ip) - matching_quad_bits(p1+2, sort_ip);
}

/****************************************************************************
sort a set of 6 byte name query response records so that the IPs that
have the most leading bits in common with the specified address come first
  ***************************************************************************/
void sort_query_replies(char *data, int n, struct ipv4_addr ip)
{
	if (n <= 1) return;

	putip(sort_ip, (char *)&ip);

	qsort(data, n, 6, QSORT_CAST name_query_comp);
}


#define TRUNCATE_NETBIOS_NAME 1

/*******************************************************************
 convert, possibly using a stupid microsoft-ism which has destroyed
 the transport independence of netbios (for CIFS vendors that usually
 use the Win95-type methods, not for NT to NT communication, which uses
 DCE/RPC and therefore full-length unicode strings...) a dns name into
 a netbios name.

 the netbios name (NOT necessarily null-terminated) is truncated to 15
 characters.

 ******************************************************************/
char *dns_to_netbios_name(char *dns_name)
{
	static char netbios_name[16];
	int i;
	StrnCpy(netbios_name, dns_name, 15);
	netbios_name[15] = 0;
	
#ifdef TRUNCATE_NETBIOS_NAME
	/* ok.  this is because of a stupid microsoft-ism.  if the called host
	   name contains a '.', microsoft clients expect you to truncate the
	   netbios name up to and including the '.'  this even applies, by
	   mistake, to workgroup (domain) names, which is _really_ daft.
	 */
	for (i = 15; i >= 0; i--)
	{
		if (netbios_name[i] == '.')
		{
			netbios_name[i] = 0;
			break;
		}
	}
#endif /* TRUNCATE_NETBIOS_NAME */

	return netbios_name;
}


/****************************************************************************
interpret the weird netbios "name". Return the name type
****************************************************************************/
static int name_interpret(char *in,char *out)
{
  int ret;
  int len = (*in++) / 2;

  *out=0;

  if (len > 30 || len<1) return(0);

  while (len--)
    {
      if (in[0] < 'A' || in[0] > 'P' || in[1] < 'A' || in[1] > 'P') {
	*out = 0;
	return(0);
      }
      *out = ((in[0]-'A')<<4) + (in[1]-'A');
      in += 2;
      out++;
    }
  *out = 0;
  ret = out[-1];

#ifdef NETBIOS_SCOPE
  /* Handle any scope names */
  while(*in) 
    {
      *out++ = '.'; /* Scope names are separated by periods */
      len = *(uint8_t *)in++;
      StrnCpy(out, in, len);
      out += len;
      *out=0;
      in += len;
    }
#endif
  return(ret);
}


/****************************************************************************
return the number of bytes that would be occupied by the result of
name_mangle()
****************************************************************************/
uint_t nbt_mangled_name_len(void)
{
	const char *scope = lp_netbios_scope();
	uint_t ret = 34;
	if (scope && *scope) {
		ret += strlen(scope) + 1;
	}
	return ret;
}

/****************************************************************************
mangle a name into netbios format

  Note:  <Out> must be nbt_mangled_name_len() in length
****************************************************************************/
int name_mangle(char *In, char *Out, char name_type)
{
	int   i;
	int   c;
	int   len;
	char  buf[20];
	char *p = Out;
	const char *scope = lp_netbios_scope();

	/* Safely copy the input string, In, into buf[]. */
	memset( buf, 0, 20 );
	if (strcmp(In,"*") == 0) {
		buf[0] = '*';
	} else {
		slprintf( buf, sizeof(buf) - 1, "%-15.15s%c", In, name_type);
	}

	/* Place the length of the first field into the output buffer. */
	p[0] = 32;
	p++;

	/* Now convert the name to the rfc1001/1002 format. */
	for ( i = 0; i < 16; i++ ) {
		c = toupper( buf[i] );
		p[i*2]     = ( (c >> 4) & 0xF ) + 'A';
		p[(i*2)+1] = (c & 0xF) + 'A';
	}
	p += 32;
	p[0] = '\0';

	if (!scope || !*scope) {
		return name_len(Out);
	}

	/* Add the scope string. */
	for (i = 0, len = 0; scope[i]; i++, len++) {
		switch(scope[i]) {
		case '.':
			p[0] = len;
			p   += (len + 1);
			len  = -1;
			break;
		default:
			p[len+1] = scope[i];
			break;
		}
	}

	p[0] = len;
	if (len > 0) {	
		p[len+1] = 0;
	}

	return name_len(Out);
}

/****************************************************************************
find a pointer to a netbios name
****************************************************************************/
static char *name_ptr(char *buf,int ofs)
{
  uint8_t c = *(uint8_t *)(buf+ofs);

  if ((c & 0xC0) == 0xC0)
    {
      uint16_t l = RSVAL(buf, ofs) & 0x3FFF;
      DEBUG(5,("name ptr to pos %d from %d is %s\n",l,ofs,buf+l));
      return(buf + l);
    }
  else
    return(buf+ofs);
}  

/****************************************************************************
extract a netbios name from a buf
****************************************************************************/
int name_extract(char *buf,int ofs,char *name)
{
	char *p = name_ptr(buf,ofs);
	int d = PTR_DIFF(p,buf+ofs);
	pstrcpy(name,"");
	if (d < -50 || d > 50) return(0);
	return(name_interpret(p,name));
}
  
/****************************************************************************
return the total storage length of a mangled name
****************************************************************************/
int name_len(char *s1)
{
	/* NOTE: this argument _must_ be unsigned */
	uint8_t *s = (uint8_t *)s1;
	int len;

	/* If the two high bits of the byte are set, return 2. */
	if (0xC0 == (*s & 0xC0))
		return(2);

	/* Add up the length bytes. */
	for (len = 1; (*s); s += (*s) + 1) {
		len += *s + 1;
		SMB_ASSERT(len < 80);
	}

	return(len);
} /* name_len */


/*
  choose a name to use when calling a server in a NBT session request.
  we use heuristics to see if the name we have been given is a IP
  address, or a too-long name. If it is then use *SMBSERVER, or a
  truncated name
*/
void choose_called_name(struct nmb_name *n, const char *name, int type)
{
	if (is_ipaddress(name)) {
		make_nmb_name(n, "*SMBSERVER", type);
		return;
	}
	if (strlen(name) > 16) {
		const char *p = strchr(name, '.');
		char name2[17];
		if (p - name > 16) {
			make_nmb_name(n, "*SMBSERVER", type);
			return;
		}
		strlcpy(name2, name, 1+(p-name));
		make_nmb_name(n, name2, type);
		return;
	}

	/* looks OK */
	make_nmb_name(n, name, type);
}