samba-mirror/source3/nmbd/asyncdns.c

/*
   Unix SMB/Netbios implementation.
   Version 1.9.
   a async DNS handler
   Copyright (C) Andrew Tridgell 1994-1997
   
   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.
   
   Revision History:

   14 jan 96: lkcl@pires.co.uk
   added multiple workgroup domain master support

*/

#include "includes.h"

extern int DEBUGLEVEL;


/***************************************************************************
  add a DNS result to the name cache
  ****************************************************************************/
static struct name_record *add_dns_result(struct nmb_name *question, struct in_addr addr)
{
  int name_type = question->name_type;
  char *qname = question->name;

  if (!addr.s_addr) {
    /* add the fail to WINS cache of names. give it 1 hour in the cache */
    DEBUG(3,("Negative DNS answer for %s\n", qname));
    add_netbios_entry(wins_client_subnet,qname,name_type,NB_ACTIVE,60*60,
                      DNSFAIL,addr,True);
    return NULL;
  }

  /* add it to our WINS cache of names. give it 2 hours in the cache */
  DEBUG(3,("DNS gave answer for %s of %s\n", qname, inet_ntoa(addr)));

  return add_netbios_entry(wins_client_subnet,qname,name_type,NB_ACTIVE,
                           2*60*60,DNS,addr, True);
}



#ifndef SYNC_DNS

static int fd_in = -1, fd_out = -1;
static int child_pid = -1;
static int in_dns;

/* this is the structure that is passed between the parent and child */
struct query_record {
	struct nmb_name name;
	struct in_addr result;
};

/* a queue of pending requests waiting for DNS responses */
static struct packet_struct *dns_queue;



/***************************************************************************
  return the fd used to gather async dns replies. This is added to the select
  loop
  ****************************************************************************/
int asyncdns_fd(void)
{
	return fd_in;
}

/***************************************************************************
  handle DNS queries arriving from the parent
  ****************************************************************************/
static void asyncdns_process(void)
{
	struct query_record r;
	fstring qname;

	DEBUGLEVEL = 0;

	while (1) {
		if (read_data(fd_in, (char *)&r, sizeof(r)) != sizeof(r)) 
			break;

		fstrcpy(qname, r.name.name);

		r.result.s_addr = interpret_addr(qname);

		if (write_data(fd_out, (char *)&r, sizeof(r)) != sizeof(r))
			break;
	}

	exit(0);
}


/***************************************************************************
  create a child process to handle DNS lookups
  ****************************************************************************/
void start_async_dns(void)
{
	int fd1[2], fd2[2];

	signal(SIGCLD, SIG_IGN);

	if (pipe(fd1) || pipe(fd2)) {
		return;
	}

	child_pid = fork();

	if (child_pid) {
		fd_in = fd1[0];
		fd_out = fd2[1];
		close(fd1[1]);
		close(fd2[0]);
		DEBUG(3,("async DNS initialised\n"));
		return;
	}

	fd_in = fd2[0];
	fd_out = fd1[1];

	asyncdns_process();
}


/***************************************************************************
check if a particular name is already being queried
  ****************************************************************************/
static BOOL query_in_queue(struct query_record *r)
{
	struct packet_struct *p;
	for (p = dns_queue; p; p = p->next) {
		struct nmb_packet *nmb = &p->packet.nmb;
		struct nmb_name *question = &nmb->question.question_name;

		if (name_equal(question, &r->name)) 
			return True;
	}
	return False;
}


/***************************************************************************
  check the DNS queue
  ****************************************************************************/
void run_dns_queue(void)
{
	struct query_record r;
	struct packet_struct *p, *p2;

	if (fd_in == -1)
		return;

	if (read_data(fd_in, (char *)&r, sizeof(r)) != sizeof(r)) {
		DEBUG(0,("Incomplete DNS answer from child!\n"));
		fd_in = -1;
		return;
	}

	add_dns_result(&r.name, r.result);

	/* loop over the whole dns queue looking for entries that
	   match the result we just got */
	for (p = dns_queue; p;) {
		struct nmb_packet *nmb = &p->packet.nmb;
		struct nmb_name *question = &nmb->question.question_name;

		if (name_equal(question, &r.name)) {
			DEBUG(3,("DNS calling reply_name_query\n"));
			in_dns = 1;
			reply_name_query(p);
			in_dns = 0;
			p->locked = False;

			if (p->prev)
				p->prev->next = p->next;
			else
				dns_queue = p->next;
			if (p->next)
				p->next->prev = p->prev;
			p2 = p->next;
			free_packet(p);
			p = p2;
		} else {
			p = p->next;
		}
	}

}

/***************************************************************************
queue a DNS query
  ****************************************************************************/
BOOL queue_dns_query(struct packet_struct *p,struct nmb_name *question,
		     struct name_record **n)
{
	struct query_record r;
	
	if (in_dns || fd_in == -1)
		return False;

	r.name = *question;

	if (!query_in_queue(&r) && 
	    !write_data(fd_out, (char *)&r, sizeof(r))) {
		DEBUG(3,("failed to send DNS query to child!\n"));
		return False;
	}

	p->locked = True;
	p->next = dns_queue;
	p->prev = NULL;
	if (p->next)
		p->next->prev = p;
	dns_queue = p;


	DEBUG(3,("added DNS query for %s\n", namestr(question)));
	return True;
}

#else


/***************************************************************************
  we use this then we can't do async DNS lookups
  ****************************************************************************/
BOOL queue_dns_query(struct packet_struct *p,struct nmb_name *question,
		     struct name_record **n)
{
	int name_type = question->name_type;
	char *qname = question->name;
	struct in_addr dns_ip;

	DEBUG(3,("DNS search for %s - ", namestr(question)));

	dns_ip.s_addr = interpret_addr(qname);

	*n = add_dns_result(question, dns_ip);
	return False;
}
#endif