src/lease.c

/* dnsmasq is Copyright (c) 2000-2005 Simon Kelley

   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; version 2 dated June, 1991.

   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.
*/

/* Author's email: simon@thekelleys.org.uk */

#include "dnsmasq.h"

static struct dhcp_lease *leases;
static FILE *lease_file;
static int dns_dirty;
enum { no, yes, force } file_dirty;
static int leases_left;

void lease_init(struct daemon *daemon, time_t now)
{
  unsigned int a0, a1, a2, a3;
  unsigned long ei;
  time_t expires;
  unsigned char hwaddr[ETHER_ADDR_LEN];
  struct in_addr addr;
  struct dhcp_lease *lease;
  int clid_len = 0;
  int has_old = 0;

  leases = NULL;
  leases_left = daemon->dhcp_max;

  /* NOTE: need a+ mode to create file if it doesn't exist */
  if (!(lease_file = fopen(daemon->lease_file, "a+")))
    die(_("cannot open or create leases file: %s"), NULL);
    
  /* a+ mode lease pointer at end. */
  rewind(lease_file);

  /* client-id max length is 255 which is 255*2 digits + 254 colons 
     borrow DNS packet buffer which is always larger than 1000 bytes */
  while (fscanf(lease_file, "%lu %40s %d.%d.%d.%d %255s %764s",
		&ei, daemon->dhcp_buff2, &a0, &a1, &a2, &a3, 
		daemon->dhcp_buff, daemon->packet) == 8)
    {
#ifdef HAVE_BROKEN_RTC
      if (ei)
	expires = (time_t)ei + now;
      else
	expires = (time_t)0;
#else 
      /* strictly time_t is opaque, but this hack should work on all sane systems,
	 even when sizeof(time_t) == 8 */
      expires = (time_t)ei;
      
      if (ei != 0  && difftime(now, expires) > 0)
	{
	  has_old = 1;
	  continue; /* expired */
	}
#endif

      parse_hex(daemon->dhcp_buff2, hwaddr, ETHER_ADDR_LEN, NULL);
      addr.s_addr = htonl((a0<<24) + (a1<<16) + (a2<<8) + a3);

      /* decode hex in place */
      if (strcmp(daemon->packet, "*") == 0)
	clid_len = 0;
      else
	clid_len = parse_hex(daemon->packet, (unsigned char *)daemon->packet, 255, NULL);
      
      if (!(lease = lease_allocate(hwaddr, (unsigned char *)daemon->packet, clid_len, addr)))
	die (_("too many stored leases"), NULL);
      
      lease->expires = expires;

      if (strcmp(daemon->dhcp_buff, "*") !=  0)
	  lease_set_hostname(lease, daemon->dhcp_buff, daemon->domain_suffix, 0);
    }
  
  dns_dirty = 1;
  file_dirty = has_old ? yes: no;

  daemon->lease_fd = fileno(lease_file);
}

void lease_update_from_configs(struct daemon *daemon)
{
  /* changes to the config may change current leases. */
  
  struct dhcp_lease *lease;
  struct dhcp_config *config;
  char *name;

  for (lease = leases; lease; lease = lease->next)
    if ((config = find_config(daemon->dhcp_conf, NULL, lease->clid, lease->clid_len, lease->hwaddr, NULL)) && 
	(config->flags & CONFIG_NAME) &&
	(!(config->flags & CONFIG_ADDR) || config->addr.s_addr == lease->addr.s_addr))
      lease_set_hostname(lease, config->hostname, daemon->domain_suffix, 1);
    else if ((name = host_from_dns(daemon, lease->addr)))
      lease_set_hostname(lease, name, daemon->domain_suffix, 1); /* updates auth flag only */
}

void lease_update_file(int always, time_t now)
{
  struct dhcp_lease *lease;
  int i = always; /* avoid warning */
  unsigned long expires;

#ifdef HAVE_BROKEN_RTC
  if (always || file_dirty == force)
    {
      lease_prune(NULL, now);
#else
  if (file_dirty != no)
    {
#endif
      rewind(lease_file);
      ftruncate(fileno(lease_file), 0);
      
      for (lease = leases; lease; lease = lease->next)
	{
#ifdef HAVE_BROKEN_RTC
	  if (lease->expires)
	    expires = (unsigned long) difftime(lease->expires, now);
	  else
	    expires = 0;
#else
	  expires = now; /* eliminate warning */
	  expires = (unsigned long)lease->expires;
#endif
	  fprintf(lease_file, "%lu %.2x:%.2x:%.2x:%.2x:%.2x:%.2x %s %s ", 
		  expires, lease->hwaddr[0], lease->hwaddr[1],
		  lease->hwaddr[2], lease->hwaddr[3], lease->hwaddr[4],
		  lease->hwaddr[5], inet_ntoa(lease->addr),
		  lease->hostname && strlen(lease->hostname) != 0 ? lease->hostname : "*");
	  
	  if (lease->clid && lease->clid_len != 0)
	    {
	      for (i = 0; i < lease->clid_len - 1; i++)
		fprintf(lease_file, "%.2x:", lease->clid[i]);
	      fprintf(lease_file, "%.2x\n", lease->clid[i]);
	    }
	  else
	    fprintf(lease_file, "*\n");
	  
	}

      fflush(lease_file);
      fsync(fileno(lease_file));
      file_dirty = no;
    }
}

void lease_update_dns(struct daemon *daemon)
{
  struct dhcp_lease *lease;
  
  if (dns_dirty)
    {
      cache_unhash_dhcp();
      
      for (lease = leases; lease; lease = lease->next)
	{
	  cache_add_dhcp_entry(daemon, lease->fqdn, &lease->addr, lease->expires);
	  cache_add_dhcp_entry(daemon, lease->hostname, &lease->addr, lease->expires);
	}
      
      dns_dirty = 0;
    }
}

void lease_prune(struct dhcp_lease *target, time_t now)
{
  struct dhcp_lease *lease, *tmp, **up;

  for (lease = leases, up = &leases; lease; lease = tmp)
    {
      tmp = lease->next;
      if ((lease->expires != 0 && difftime(now, lease->expires) > 0) || lease == target)
	{
	  file_dirty = yes;

	  *up = lease->next; /* unlink */
	  if (lease->hostname)
	    {
	      free(lease->hostname); 
	      dns_dirty = 1;
	    }
	  if (lease->fqdn)
	    free(lease->fqdn);
	  if (lease->clid)
	    free(lease->clid);
	  free(lease);
	  leases_left++;
	}
      else
	up = &lease->next;
    }
} 
	
  
struct dhcp_lease *lease_find_by_client(unsigned char *hwaddr,
					unsigned char *clid, int clid_len)
{
  struct dhcp_lease *lease;

  if (clid)
    for (lease = leases; lease; lease = lease->next)
      if (lease->clid && clid_len == lease->clid_len &&
	  memcmp(clid, lease->clid, clid_len) == 0)
	return lease;
  
  for (lease = leases; lease; lease = lease->next)	
    if ((!lease->clid || !clid) && 
	memcmp(hwaddr, lease->hwaddr, ETHER_ADDR_LEN) == 0)
      return lease;
  
  return NULL;
}

struct dhcp_lease *lease_find_by_addr(struct in_addr addr)
{
  struct dhcp_lease *lease;

  for (lease = leases; lease; lease = lease->next)
    if (lease->addr.s_addr == addr.s_addr)
      return lease;
  
  return NULL;
}


struct dhcp_lease *lease_allocate(unsigned char *hwaddr, unsigned char *clid, 
				  int clid_len, struct in_addr addr)
{
  struct dhcp_lease *lease;
  if (!leases_left || !(lease = malloc(sizeof(struct dhcp_lease))))
    return NULL;

  lease->clid = NULL;
  lease->hostname = lease->fqdn = NULL;  
  lease->addr = addr;
  memset(lease->hwaddr, 0, ETHER_ADDR_LEN);
  lease->expires = 1;
  
  if (!lease_set_hwaddr(lease, hwaddr, clid, clid_len))
    {
      free(lease);
      return NULL;
    }

  lease->next = leases;
  leases = lease;
  
  file_dirty = force;
  leases_left--;

  return lease;
}

void lease_set_expires(struct dhcp_lease *lease, time_t exp)
{
  if (exp != lease->expires)
    {
      file_dirty = yes;
      dns_dirty = 1;
    }
  lease->expires = exp;
}

int lease_set_hwaddr(struct dhcp_lease *lease, unsigned char *hwaddr,
		      unsigned char *clid, int clid_len)
{
  if (memcmp(lease->hwaddr, hwaddr, ETHER_ADDR_LEN) != 0)
    {
      file_dirty = force;
      memcpy(lease->hwaddr, hwaddr, ETHER_ADDR_LEN);
    }

  /* only update clid when one is available, stops packets
     without a clid removing the record. Lease init uses
     clid_len == 0 for no clid. */
  if (clid_len != 0 && clid)
    {
      if (!lease->clid)
	lease->clid_len = 0;

      if (lease->clid_len != clid_len)
	{
	  file_dirty = force;
	  if (lease->clid)
	    free(lease->clid);
	  if (!(lease->clid = malloc(clid_len)))
	    return 0;
	}
      else if (memcmp(lease->clid, clid, clid_len) != 0)
	file_dirty = force;

      lease->clid_len = clid_len;
      memcpy(lease->clid, clid, clid_len);
    }

  return 1;
}

void lease_set_hostname(struct dhcp_lease *lease, char *name, char *suffix, int auth)
{
  struct dhcp_lease *lease_tmp;
  char *new_name = NULL, *new_fqdn = NULL;

  if (lease->hostname && name && hostname_isequal(lease->hostname, name))
    {
      lease->auth_name = auth;
      return;
    }

  if (!name && !lease->hostname)
    return;

  /* If a machine turns up on a new net without dropping the old lease,
     or two machines claim the same name, then we end up with two interfaces with
     the same name. Check for that here and remove the name from the old lease.
     Don't allow a name from the client to override a name from dnsmasq config. */
  
  if (name)
    {
      for (lease_tmp = leases; lease_tmp; lease_tmp = lease_tmp->next)
	if (lease_tmp->hostname && hostname_isequal(lease_tmp->hostname, name))
	  {
	    if (lease_tmp->auth_name && !auth)
	      return;
	    new_name = lease_tmp->hostname;
	    lease_tmp->hostname = NULL;
	    if (lease_tmp->fqdn)
	      {
		new_fqdn = lease_tmp->fqdn;
		lease_tmp->fqdn = NULL;
	      }
	    break;
	  }
     
      if (!new_name && (new_name = malloc(strlen(name) + 1)))
	strcpy(new_name, name);
      
      if (suffix && !new_fqdn && (new_fqdn = malloc(strlen(name) + strlen(suffix) + 2)))
	{
	  strcpy(new_fqdn, name);
	  strcat(new_fqdn, ".");
	  strcat(new_fqdn, suffix);
	}
    }

  if (lease->hostname)
    free(lease->hostname);
  if (lease->fqdn)
    free(lease->fqdn);
  
  lease->hostname = new_name;
  lease->fqdn = new_fqdn;
  lease->auth_name = auth;
  
  file_dirty = force;
  dns_dirty = 1;
}