src/cache.c

/* dnsmasq is Copyright (c) 2000-2018 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, or
   (at your option) version 3 dated 29 June, 2007.
 
   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, see <http://www.gnu.org/licenses/>.
*/

#include "dnsmasq.h"

static struct crec *cache_head = NULL, *cache_tail = NULL, **hash_table = NULL;
#ifdef HAVE_DHCP
static struct crec *dhcp_spare = NULL;
#endif
static struct crec *new_chain = NULL;
static int insert_error;
static union bigname *big_free = NULL;
static int bignames_left, hash_size;

static void make_non_terminals(struct crec *source);
static struct crec *really_insert(char *name, struct all_addr *addr, 
				  time_t now,  unsigned long ttl, unsigned short flags);

/* type->string mapping: this is also used by the name-hash function as a mixing table. */
static const struct {
  unsigned int type;
  const char * const name;
} typestr[] = {
  { 1,   "A" },
  { 2,   "NS" },
  { 5,   "CNAME" },
  { 6,   "SOA" },
  { 10,  "NULL" },
  { 11,  "WKS" },
  { 12,  "PTR" },
  { 13,  "HINFO" },	
  { 15,  "MX" },
  { 16,  "TXT" },
  { 22,  "NSAP" },
  { 23,  "NSAP_PTR" },
  { 24,  "SIG" },
  { 25,  "KEY" },
  { 28,  "AAAA" },
  { 29,  "LOC" },
  { 33,  "SRV" },
  { 35,  "NAPTR" },
  { 36,  "KX" },
  { 37,  "CERT" },
  { 38,  "A6" },
  { 39,  "DNAME" },
  { 41,  "OPT" },
  { 43,  "DS" },
  { 46,  "RRSIG" },
  { 47,  "NSEC" },
  { 48,  "DNSKEY" },
  { 50,  "NSEC3" },
  { 51,  "NSEC3PARAM" },
  { 52,  "TLSA" },
  { 53,  "SMIMEA" },
  { 55,  "HIP" },
  { 249, "TKEY" },
  { 250, "TSIG" },
  { 251, "IXFR" },
  { 252, "AXFR" },
  { 253, "MAILB" },
  { 254, "MAILA" },
  { 255, "ANY" },
  { 257, "CAA" }
};

static void cache_free(struct crec *crecp);
static void cache_unlink(struct crec *crecp);
static void cache_link(struct crec *crecp);
static void rehash(int size);
static void cache_hash(struct crec *crecp);

void next_uid(struct crec *crecp)
{
  static unsigned int uid = 0;

  if (crecp->uid == UID_NONE)
    {
      uid++;
  
      /* uid == 0 used to indicate CNAME to interface name. */
      if (uid == UID_NONE)
	uid++;
      
      crecp->uid = uid;
    }
}

void cache_init(void)
{
  struct crec *crecp;
  int i;
 
  bignames_left = daemon->cachesize/10;
  
  if (daemon->cachesize > 0)
    {
      crecp = safe_malloc(daemon->cachesize*sizeof(struct crec));
      
      for (i=0; i < daemon->cachesize; i++, crecp++)
	{
	  cache_link(crecp);
	  crecp->flags = 0;
	  crecp->uid = UID_NONE;
	}
    }
  
  /* create initial hash table*/
  rehash(daemon->cachesize);
}

/* In most cases, we create the hash table once here by calling this with (hash_table == NULL)
   but if the hosts file(s) are big (some people have 50000 ad-block entries), the table
   will be much too small, so the hosts reading code calls rehash every 1000 addresses, to
   expand the table. */
static void rehash(int size)
{
  struct crec **new, **old, *p, *tmp;
  int i, new_size, old_size;

  /* hash_size is a power of two. */
  for (new_size = 64; new_size < size/10; new_size = new_size << 1);
  
  /* must succeed in getting first instance, failure later is non-fatal */
  if (!hash_table)
    new = safe_malloc(new_size * sizeof(struct crec *));
  else if (new_size <= hash_size || !(new = whine_malloc(new_size * sizeof(struct crec *))))
    return;

  for(i = 0; i < new_size; i++)
    new[i] = NULL;

  old = hash_table;
  old_size = hash_size;
  hash_table = new;
  hash_size = new_size;
  
  if (old)
    {
      for (i = 0; i < old_size; i++)
	for (p = old[i]; p ; p = tmp)
	  {
	    tmp = p->hash_next;
	    cache_hash(p);
	  }
      free(old);
    }
}
  
static struct crec **hash_bucket(char *name)
{
  unsigned int c, val = 017465; /* Barker code - minimum self-correlation in cyclic shift */
  const unsigned char *mix_tab = (const unsigned char*)typestr; 

  while((c = (unsigned char) *name++))
    {
      /* don't use tolower and friends here - they may be messed up by LOCALE */
      if (c >= 'A' && c <= 'Z')
	c += 'a' - 'A';
      val = ((val << 7) | (val >> (32 - 7))) + (mix_tab[(val + c) & 0x3F] ^ c);
    } 
  
  /* hash_size is a power of two */
  return hash_table + ((val ^ (val >> 16)) & (hash_size - 1));
}

static void cache_hash(struct crec *crecp)
{
  /* maintain an invariant that all entries with F_REVERSE set
     are at the start of the hash-chain  and all non-reverse
     immortal entries are at the end of the hash-chain.
     This allows reverse searches and garbage collection to be optimised */

  struct crec **up = hash_bucket(cache_get_name(crecp));

  if (!(crecp->flags & F_REVERSE))
    {
      while (*up && ((*up)->flags & F_REVERSE))
	up = &((*up)->hash_next); 
      
      if (crecp->flags & F_IMMORTAL)
	while (*up && !((*up)->flags & F_IMMORTAL))
	  up = &((*up)->hash_next);
    }
  crecp->hash_next = *up;
  *up = crecp;
}

#ifdef HAVE_DNSSEC
static void cache_blockdata_free(struct crec *crecp)
{
  if (crecp->flags & F_DNSKEY)
    blockdata_free(crecp->addr.key.keydata);
  else if ((crecp->flags & F_DS) && !(crecp->flags & F_NEG))
    blockdata_free(crecp->addr.ds.keydata);
}
#endif

static void cache_free(struct crec *crecp)
{
  crecp->flags &= ~F_FORWARD;
  crecp->flags &= ~F_REVERSE;
  crecp->uid = UID_NONE; /* invalidate CNAMES pointing to this. */

  if (cache_tail)
    cache_tail->next = crecp;
  else
    cache_head = crecp;
  crecp->prev = cache_tail;
  crecp->next = NULL;
  cache_tail = crecp;
  
  /* retrieve big name for further use. */
  if (crecp->flags & F_BIGNAME)
    {
      crecp->name.bname->next = big_free;
      big_free = crecp->name.bname;
      crecp->flags &= ~F_BIGNAME;
    }

#ifdef HAVE_DNSSEC
  cache_blockdata_free(crecp);
#endif
}    

/* insert a new cache entry at the head of the list (youngest entry) */
static void cache_link(struct crec *crecp)
{
  if (cache_head) /* check needed for init code */
    cache_head->prev = crecp;
  crecp->next = cache_head;
  crecp->prev = NULL;
  cache_head = crecp;
  if (!cache_tail)
    cache_tail = crecp;
}

/* remove an arbitrary cache entry for promotion */ 
static void cache_unlink (struct crec *crecp)
{
  if (crecp->prev)
    crecp->prev->next = crecp->next;
  else
    cache_head = crecp->next;

  if (crecp->next)
    crecp->next->prev = crecp->prev;
  else
    cache_tail = crecp->prev;
}

char *cache_get_name(struct crec *crecp)
{
  if (crecp->flags & F_BIGNAME)
    return crecp->name.bname->name;
  else if (crecp->flags & F_NAMEP) 
    return crecp->name.namep;
  
  return crecp->name.sname;
}

char *cache_get_cname_target(struct crec *crecp)
{
  if (crecp->addr.cname.uid != SRC_INTERFACE)
    return cache_get_name(crecp->addr.cname.target.cache);

  return crecp->addr.cname.target.int_name->name;
}



struct crec *cache_enumerate(int init)
{
  static int bucket;
  static struct crec *cache;

  if (init)
    {
      bucket = 0;
      cache = NULL;
    }
  else if (cache && cache->hash_next)
    cache = cache->hash_next;
  else
    {
       cache = NULL; 
       while (bucket < hash_size)
	 if ((cache = hash_table[bucket++]))
	   break;
    }
  
  return cache;
}

static int is_outdated_cname_pointer(struct crec *crecp)
{
  if (!(crecp->flags & F_CNAME) || crecp->addr.cname.uid == SRC_INTERFACE)
    return 0;
  
  /* NB. record may be reused as DS or DNSKEY, where uid is 
     overloaded for something completely different */
  if (crecp->addr.cname.target.cache && 
      (crecp->addr.cname.target.cache->flags & (F_IPV4 | F_IPV6 | F_CNAME)) &&
      crecp->addr.cname.uid == crecp->addr.cname.target.cache->uid)
    return 0;
  
  return 1;
}

static int is_expired(time_t now, struct crec *crecp)
{
  if (crecp->flags & F_IMMORTAL)
    return 0;

  if (difftime(now, crecp->ttd) < 0)
    return 0;
  
  return 1;
}

static struct crec *cache_scan_free(char *name, struct all_addr *addr, time_t now, unsigned short flags,
				    struct crec **target_crec, unsigned int *target_uid)
{
  /* Scan and remove old entries.
     If (flags & F_FORWARD) then remove any forward entries for name and any expired
     entries but only in the same hash bucket as name.
     If (flags & F_REVERSE) then remove any reverse entries for addr and any expired
     entries in the whole cache.
     If (flags == 0) remove any expired entries in the whole cache. 

     In the flags & F_FORWARD case, the return code is valid, and returns a non-NULL pointer
     to a cache entry if the name exists in the cache as a HOSTS or DHCP entry (these are never deleted)

     We take advantage of the fact that hash chains have stuff in the order <reverse>,<other>,<immortal>
     so that when we hit an entry which isn't reverse and is immortal, we're done. 

     If we free a crec which is a CNAME target, return the entry and uid in target_crec and target_uid.
     This entry will get re-used with the same name, to preserve CNAMEs. */
 
  struct crec *crecp, **up;
  
  if (flags & F_FORWARD)
    {
      for (up = hash_bucket(name), crecp = *up; crecp; crecp = crecp->hash_next)
	{
	  if ((crecp->flags & F_FORWARD) && hostname_isequal(cache_get_name(crecp), name))
	    {
	      /* Don't delete DNSSEC in favour of a CNAME, they can co-exist */
	      if ((flags & crecp->flags & (F_IPV4 | F_IPV6)) || 
		  (((crecp->flags | flags) & F_CNAME) && !(crecp->flags & (F_DNSKEY | F_DS))))
		{
		  if (crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG))
		    return crecp;
		  *up = crecp->hash_next;
		  /* If this record is for the name we're inserting and is the target
		     of a CNAME record. Make the new record for the same name, in the same
		     crec, with the same uid to avoid breaking the existing CNAME. */
		  if (crecp->uid != UID_NONE)
		    {
		      if (target_crec)
			*target_crec = crecp;
		      if (target_uid)
			*target_uid = crecp->uid;
		    }
		  cache_unlink(crecp);
		  cache_free(crecp);
		  continue;
		}
	      
#ifdef HAVE_DNSSEC
	      /* Deletion has to be class-sensitive for DS and DNSKEY */
	      if ((flags & crecp->flags & (F_DNSKEY | F_DS)) && crecp->uid == addr->addr.dnssec.class)
		{
		  if (crecp->flags & F_CONFIG)
		    return crecp;
		  *up = crecp->hash_next;
		  cache_unlink(crecp);
		  cache_free(crecp);
		  continue;
		}
#endif
	    }

	  if (is_expired(now, crecp) || is_outdated_cname_pointer(crecp))
	    { 
	      *up = crecp->hash_next;
	      if (!(crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)))
		{
		  cache_unlink(crecp);
		  cache_free(crecp);
		}
	      continue;
	    } 
	  
	  up = &crecp->hash_next;
	}
    }
  else
    {
      int i;
#ifdef HAVE_IPV6
      int addrlen = (flags & F_IPV6) ? IN6ADDRSZ : INADDRSZ;
#else
      int addrlen = INADDRSZ;
#endif 
      for (i = 0; i < hash_size; i++)
	for (crecp = hash_table[i], up = &hash_table[i]; 
	     crecp && ((crecp->flags & F_REVERSE) || !(crecp->flags & F_IMMORTAL));
	     crecp = crecp->hash_next)
	  if (is_expired(now, crecp))
	    {
	      *up = crecp->hash_next;
	      if (!(crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)))
		{ 
		  cache_unlink(crecp);
		  cache_free(crecp);
		}
	    }
	  else if (!(crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)) &&
		   (flags & crecp->flags & F_REVERSE) && 
		   (flags & crecp->flags & (F_IPV4 | F_IPV6)) &&
		   memcmp(&crecp->addr.addr, addr, addrlen) == 0)
	    {
	      *up = crecp->hash_next;
	      cache_unlink(crecp);
	      cache_free(crecp);
	    }
	  else
	    up = &crecp->hash_next;
    }
  
  return NULL;
}

/* Note: The normal calling sequence is
   cache_start_insert
   cache_insert * n
   cache_end_insert

   but an abort can cause the cache_end_insert to be missed 
   in which can the next cache_start_insert cleans things up. */

void cache_start_insert(void)
{
  /* Free any entries which didn't get committed during the last
     insert due to error.
  */
  while (new_chain)
    {
      struct crec *tmp = new_chain->next;
      cache_free(new_chain);
      new_chain = tmp;
    }
  new_chain = NULL;
  insert_error = 0;
}

struct crec *cache_insert(char *name, struct all_addr *addr, 
			  time_t now,  unsigned long ttl, unsigned short flags)
{
  /* Don't log DNSSEC records here, done elsewhere */
  if (flags & (F_IPV4 | F_IPV6 | F_CNAME))
    {
      log_query(flags | F_UPSTREAM, name, addr, NULL);
      /* Don't mess with TTL for DNSSEC records. */
      if (daemon->max_cache_ttl != 0 && daemon->max_cache_ttl < ttl)
	ttl = daemon->max_cache_ttl;
      if (daemon->min_cache_ttl != 0 && daemon->min_cache_ttl > ttl)
	ttl = daemon->min_cache_ttl;
    }
  
  return really_insert(name, addr, now, ttl, flags);
}


static struct crec *really_insert(char *name, struct all_addr *addr, 
				  time_t now,  unsigned long ttl, unsigned short flags)
{
  struct crec *new, *target_crec = NULL;
  union bigname *big_name = NULL;
  int freed_all = flags & F_REVERSE;
  int free_avail = 0;
  unsigned int target_uid;
  
  /* if previous insertion failed give up now. */
  if (insert_error)
    return NULL;
  
  /* First remove any expired entries and entries for the name/address we
     are currently inserting. */
  if ((new = cache_scan_free(name, addr, now, flags, &target_crec, &target_uid)))
    {
      /* We're trying to insert a record over one from 
	 /etc/hosts or DHCP, or other config. If the 
	 existing record is for an A or AAAA and
	 the record we're trying to insert is the same, 
	 just drop the insert, but don't error the whole process. */
      if ((flags & (F_IPV4 | F_IPV6)) && (flags & F_FORWARD) && addr)
	{
	  if ((flags & F_IPV4) && (new->flags & F_IPV4) &&
	      new->addr.addr.addr.addr4.s_addr == addr->addr.addr4.s_addr)
	    return new;
#ifdef HAVE_IPV6
	  else if ((flags & F_IPV6) && (new->flags & F_IPV6) &&
		   IN6_ARE_ADDR_EQUAL(&new->addr.addr.addr.addr6, &addr->addr.addr6))
	    return new;
#endif
	}
      
      insert_error = 1;
      return NULL;
    }
  
  /* Now get a cache entry from the end of the LRU list */
  if (!target_crec)
    while (1) {
      if (!(new = cache_tail)) /* no entries left - cache is too small, bail */
	{
	  insert_error = 1;
	  return NULL;
	}
      
      /* Free entry at end of LRU list, use it. */
      if (!(new->flags & (F_FORWARD | F_REVERSE)))
	break;

      /* End of LRU list is still in use: if we didn't scan all the hash
	 chains for expired entries do that now. If we already tried that
	 then it's time to start spilling things. */
      
      /* If free_avail set, we believe that an entry has been freed.
	 Bugs have been known to make this not true, resulting in
	 a tight loop here. If that happens, abandon the
	 insert. Once in this state, all inserts will probably fail. */
      if (free_avail)
	{
	  static int warned = 0;
	  if (!warned)
	    {
	      my_syslog(LOG_ERR, _("Internal error in cache."));
	      warned = 1;
	    }
	  insert_error = 1;
	  return NULL;
	}
      
      if (freed_all)
	{
	  struct all_addr free_addr = new->addr.addr;;
	  
#ifdef HAVE_DNSSEC
	  /* For DNSSEC records, addr holds class. */
	  if (new->flags & (F_DS | F_DNSKEY))
	    free_addr.addr.dnssec.class = new->uid;
#endif
	  
	  free_avail = 1; /* Must be free space now. */
	  cache_scan_free(cache_get_name(new), &free_addr, now, new->flags, NULL, NULL);
	  daemon->metrics[METRIC_DNS_CACHE_LIVE_FREED]++;
	}
      else
	{
	  cache_scan_free(NULL, NULL, now, 0, NULL, NULL);
	  freed_all = 1;
	}
    }
      
  /* Check if we need to and can allocate extra memory for a long name.
     If that fails, give up now, always succeed for DNSSEC records. */
  if (name && (strlen(name) > SMALLDNAME-1))
    {
      if (big_free)
	{ 
	  big_name = big_free;
	  big_free = big_free->next;
	}
      else if ((bignames_left == 0 && !(flags & (F_DS | F_DNSKEY))) ||
	       !(big_name = (union bigname *)whine_malloc(sizeof(union bigname))))
	{
	  insert_error = 1;
	  return NULL;
	}
      else if (bignames_left != 0)
	bignames_left--;
      
    }

  /* If we freed a cache entry for our name which was a CNAME target, use that.
     and preserve the uid, so that existing CNAMES are not broken. */
  if (target_crec)
    {
      new = target_crec;
      new->uid = target_uid;
    }
  
  /* Got the rest: finally grab entry. */
  cache_unlink(new);
  
  new->flags = flags;
  if (big_name)
    {
      new->name.bname = big_name;
      new->flags |= F_BIGNAME;
    }

  if (name)
    strcpy(cache_get_name(new), name);
  else
    *cache_get_name(new) = 0;

  if (addr)
    {
#ifdef HAVE_DNSSEC
      if (flags & (F_DS | F_DNSKEY))
	new->uid = addr->addr.dnssec.class;
      else
#endif
	new->addr.addr = *addr;	
    }

  new->ttd = now + (time_t)ttl;
  new->next = new_chain;
  new_chain = new;

  return new;
}

/* after end of insertion, commit the new entries */
void cache_end_insert(void)
{
  if (insert_error)
    return;
  
  while (new_chain)
    { 
      struct crec *tmp = new_chain->next;
      /* drop CNAMEs which didn't find a target. */
      if (is_outdated_cname_pointer(new_chain))
	cache_free(new_chain);
      else
	{
	  cache_hash(new_chain);
	  cache_link(new_chain);
	  daemon->metrics[METRIC_DNS_CACHE_INSERTED]++;

	  /* If we're a child process, send this cache entry up the pipe to the master.
	     The marshalling process is rather nasty. */
	  if (daemon->pipe_to_parent != -1)
	    {
	      char *name = cache_get_name(new_chain);
	      ssize_t m = strlen(name);
	      unsigned short flags = new_chain->flags;
#ifdef HAVE_DNSSEC
	      u16 class = new_chain->uid;
#endif
	      
	      read_write(daemon->pipe_to_parent, (unsigned char *)&m, sizeof(m), 0);
	      read_write(daemon->pipe_to_parent, (unsigned char *)name, m, 0);
	      read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->ttd, sizeof(new_chain->ttd), 0);
	      read_write(daemon->pipe_to_parent, (unsigned  char *)&flags, sizeof(flags), 0);

	      if (flags & (F_IPV4 | F_IPV6))
		read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr, sizeof(new_chain->addr), 0);
#ifdef HAVE_DNSSEC
	      else if (flags & F_DNSKEY)
		{
		  read_write(daemon->pipe_to_parent, (unsigned char *)&class, sizeof(class), 0);
		  read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.key.algo, sizeof(new_chain->addr.key.algo), 0);
		  read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.key.keytag, sizeof(new_chain->addr.key.keytag), 0);
		  read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.key.flags, sizeof(new_chain->addr.key.flags), 0);
		  read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.key.keylen, sizeof(new_chain->addr.key.keylen), 0);
		  blockdata_write(new_chain->addr.key.keydata, new_chain->addr.key.keylen, daemon->pipe_to_parent);
		}
	      else if (flags & F_DS)
		{
		  read_write(daemon->pipe_to_parent, (unsigned char *)&class, sizeof(class), 0);
		  /* A negative DS entry is possible and has no data, obviously. */
		  if (!(flags & F_NEG))
		    {
		      read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.ds.algo, sizeof(new_chain->addr.ds.algo), 0);
		      read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.ds.keytag, sizeof(new_chain->addr.ds.keytag), 0);
		      read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.ds.digest, sizeof(new_chain->addr.ds.digest), 0);
		      read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.ds.keylen, sizeof(new_chain->addr.ds.keylen), 0);
		      blockdata_write(new_chain->addr.ds.keydata, new_chain->addr.ds.keylen, daemon->pipe_to_parent);
		    }
		}
#endif
	      
	    }
	}
      
      new_chain = tmp;
    }

  /* signal end of cache insert in master process */
  if (daemon->pipe_to_parent != -1)
    {
      ssize_t m = -1;
      read_write(daemon->pipe_to_parent, (unsigned char *)&m, sizeof(m), 0);
    }
      
  new_chain = NULL;
}


/* A marshalled cache entry arrives on fd, read, unmarshall and insert into cache of master process. */
int cache_recv_insert(time_t now, int fd)
{
  ssize_t m;
  struct all_addr addr;
  unsigned long ttl;
  time_t ttd;
  unsigned short flags;
  struct crec *crecp = NULL;
  
  cache_start_insert();
  
  while(1)
    {
 
      if (!read_write(fd, (unsigned char *)&m, sizeof(m), 1))
	return 0;
      
      if (m == -1)
	{
	  cache_end_insert();
	  return 1;
	}

      if (!read_write(fd, (unsigned char *)daemon->namebuff, m, 1) ||
	  !read_write(fd, (unsigned char *)&ttd, sizeof(ttd), 1) ||
	  !read_write(fd, (unsigned char *)&flags, sizeof(flags), 1))
	return 0;

      daemon->namebuff[m] = 0;

      ttl = difftime(ttd, now);
      
      if (flags & (F_IPV4 | F_IPV6))
	{
	  if (!read_write(fd, (unsigned char *)&addr, sizeof(addr), 1))
	    return 0;
	  crecp = really_insert(daemon->namebuff, &addr, now, ttl, flags);
	}
      else if (flags & F_CNAME)
	{
	  struct crec *newc = really_insert(daemon->namebuff, NULL, now, ttl, flags);
	  /* This relies on the fact the the target of a CNAME immediately preceeds
	     it because of the order of extraction in extract_addresses, and
	     the order reversal on the new_chain. */
	  if (newc)
	    {
	      if (!crecp)
		{
		  newc->addr.cname.target.cache = NULL;
		  /* anything other than zero, to avoid being mistaken for CNAME to interface-name */ 
		  newc->addr.cname.uid = 1; 
		}
	      else
		{
		  next_uid(crecp);
		  newc->addr.cname.target.cache = crecp;
		  newc->addr.cname.uid = crecp->uid;
		}
	    }
	}
#ifdef HAVE_DNSSEC
      else if (flags & (F_DNSKEY | F_DS))
	{
	  unsigned short class, keylen, keyflags, keytag;
	  unsigned char algo, digest;
	  struct blockdata *keydata;
	  
	  if (!read_write(fd, (unsigned char *)&class, sizeof(class), 1))
	    return 0;
	  /* Cache needs to known class for DNSSEC stuff */
	  addr.addr.dnssec.class = class;

	  crecp = really_insert(daemon->namebuff, &addr, now, ttl, flags);
	    
	  if (flags & F_DNSKEY)
	    {
	      if (!read_write(fd, (unsigned char *)&algo, sizeof(algo), 1) ||
		  !read_write(fd, (unsigned char *)&keytag, sizeof(keytag), 1) ||
		  !read_write(fd, (unsigned char *)&keyflags, sizeof(keyflags), 1) ||
		  !read_write(fd, (unsigned char *)&keylen, sizeof(keylen), 1) ||
		  !(keydata = blockdata_read(fd, keylen)))
		return 0;
	    }
	  else if (!(flags & F_NEG))
	    {
	      if (!read_write(fd, (unsigned char *)&algo, sizeof(algo), 1) ||
		  !read_write(fd, (unsigned char *)&keytag, sizeof(keytag), 1) ||
		  !read_write(fd, (unsigned char *)&digest, sizeof(digest), 1) ||
		  !read_write(fd, (unsigned char *)&keylen, sizeof(keylen), 1) ||
		  !(keydata = blockdata_read(fd, keylen)))
		return 0;
	    }

	  if (crecp)
	    {
	       if (flags & F_DNSKEY)
		 {
		   crecp->addr.key.algo = algo;
		   crecp->addr.key.keytag = keytag;
		   crecp->addr.key.flags = flags;
		   crecp->addr.key.keylen = keylen;
		   crecp->addr.key.keydata = keydata;
		 }
	       else if (!(flags & F_NEG))
		 {
		   crecp->addr.ds.algo = algo;
		   crecp->addr.ds.keytag = keytag;
		   crecp->addr.ds.digest = digest;
		   crecp->addr.ds.keylen = keylen;
		   crecp->addr.ds.keydata = keydata;
		 }
	    }
	}
#endif
    }
}
	
int cache_find_non_terminal(char *name, time_t now)
{
  struct crec *crecp;

  for (crecp = *hash_bucket(name); crecp; crecp = crecp->hash_next)
    if (!is_outdated_cname_pointer(crecp) &&
	!is_expired(now, crecp) &&
	(crecp->flags & F_FORWARD) &&
	hostname_isequal(name, cache_get_name(crecp)))
      return 1;

  return 0;
}

struct crec *cache_find_by_name(struct crec *crecp, char *name, time_t now, unsigned int prot)
{
  struct crec *ans;
  int no_rr = prot & F_NO_RR;

  prot &= ~F_NO_RR;
  
  if (crecp) /* iterating */
    ans = crecp->next;
  else
    {
      /* first search, look for relevant entries and push to top of list
	 also free anything which has expired */
      struct crec *next, **up, **insert = NULL, **chainp = &ans;
      unsigned short ins_flags = 0;
      
      for (up = hash_bucket(name), crecp = *up; crecp; crecp = next)
	{
	  next = crecp->hash_next;
	  
	  if (!is_expired(now, crecp) && !is_outdated_cname_pointer(crecp))
	    {
	      if ((crecp->flags & F_FORWARD) && 
		  (crecp->flags & prot) &&
		  hostname_isequal(cache_get_name(crecp), name))
		{
		  if (crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG))
		    {
		      *chainp = crecp;
		      chainp = &crecp->next;
		    }
		  else
		    {
		      cache_unlink(crecp);
		      cache_link(crecp);
		    }
	      	      
		  /* Move all but the first entry up the hash chain
		     this implements round-robin. 
		     Make sure that re-ordering doesn't break the hash-chain
		     order invariants. 
		  */
		  if (insert && (crecp->flags & (F_REVERSE | F_IMMORTAL)) == ins_flags)
		    {
		      *up = crecp->hash_next;
		      crecp->hash_next = *insert;
		      *insert = crecp;
		      insert = &crecp->hash_next;
		    }
		  else
		    {
		      if (!insert && !no_rr)
			{
			  insert = up;
			  ins_flags = crecp->flags & (F_REVERSE | F_IMMORTAL);
			}
		      up = &crecp->hash_next; 
		    }
		}
	      else
		/* case : not expired, incorrect entry. */
		up = &crecp->hash_next; 
	    }
	  else
	    {
	      /* expired entry, free it */
	      *up = crecp->hash_next;
	      if (!(crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)))
		{ 
		  cache_unlink(crecp);
		  cache_free(crecp);
		}
	    }
	}
	  
      *chainp = cache_head;
    }

  if (ans && 
      (ans->flags & F_FORWARD) &&
      (ans->flags & prot) &&     
      hostname_isequal(cache_get_name(ans), name))
    return ans;
  
  return NULL;
}

struct crec *cache_find_by_addr(struct crec *crecp, struct all_addr *addr, 
				time_t now, unsigned int prot)
{
  struct crec *ans;
#ifdef HAVE_IPV6
  int addrlen = (prot == F_IPV6) ? IN6ADDRSZ : INADDRSZ;
#else
  int addrlen = INADDRSZ;
#endif
  
  if (crecp) /* iterating */
    ans = crecp->next;
  else
    {  
      /* first search, look for relevant entries and push to top of list
	 also free anything which has expired. All the reverse entries are at the
	 start of the hash chain, so we can give up when we find the first 
	 non-REVERSE one.  */
       int i;
       struct crec **up, **chainp = &ans;
       
       for (i=0; i<hash_size; i++)
	 for (crecp = hash_table[i], up = &hash_table[i]; 
	      crecp && (crecp->flags & F_REVERSE);
	      crecp = crecp->hash_next)
	   if (!is_expired(now, crecp))
	     {      
	       if ((crecp->flags & prot) &&
		   memcmp(&crecp->addr.addr, addr, addrlen) == 0)
		 {	    
		   if (crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG))
		     {
		       *chainp = crecp;
		       chainp = &crecp->next;
		     }
		   else
		     {
		       cache_unlink(crecp);
		       cache_link(crecp);
		     }
		 }
	       up = &crecp->hash_next;
	     }
	   else
	     {
	       *up = crecp->hash_next;
	       if (!(crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)))
		 {
		   cache_unlink(crecp);
		   cache_free(crecp);
		 }
	     }
       
       *chainp = cache_head;
    }
  
  if (ans && 
      (ans->flags & F_REVERSE) &&
      (ans->flags & prot) &&
      memcmp(&ans->addr.addr, addr, addrlen) == 0)
    return ans;
  
  return NULL;
}

static void add_hosts_cname(struct crec *target)
{
  struct crec *crec;
  struct cname *a;
  
  for (a = daemon->cnames; a; a = a->next)
    if (a->alias[1] != '*' &&
	hostname_isequal(cache_get_name(target), a->target) &&
	(crec = whine_malloc(SIZEOF_POINTER_CREC)))
      {
	crec->flags = F_FORWARD | F_IMMORTAL | F_NAMEP | F_CONFIG | F_CNAME;
	crec->ttd = a->ttl;
	crec->name.namep = a->alias;
	crec->addr.cname.target.cache = target;
	next_uid(target);
	crec->addr.cname.uid = target->uid;
	crec->uid = UID_NONE;
	cache_hash(crec);
	make_non_terminals(crec);
	
	add_hosts_cname(crec); /* handle chains */
      }
}
  
static void add_hosts_entry(struct crec *cache, struct all_addr *addr, int addrlen, 
			    unsigned int index, struct crec **rhash, int hashsz)
{
  struct crec *lookup = cache_find_by_name(NULL, cache_get_name(cache), 0, cache->flags & (F_IPV4 | F_IPV6));
  int i, nameexists = 0;
  unsigned int j; 

  /* Remove duplicates in hosts files. */
  if (lookup && (lookup->flags & F_HOSTS))
    {
      nameexists = 1;
      if (memcmp(&lookup->addr.addr, addr, addrlen) == 0)
	{
	  free(cache);
	  return;
	}
    }
  
  /* Ensure there is only one address -> name mapping (first one trumps) 
     We do this by steam here, The entries are kept in hash chains, linked
     by ->next (which is unused at this point) held in hash buckets in
     the array rhash, hashed on address. Note that rhash and the values
     in ->next are only valid  whilst reading hosts files: the buckets are
     then freed, and the ->next pointer used for other things. 

     Only insert each unique address once into this hashing structure.

     This complexity avoids O(n^2) divergent CPU use whilst reading
     large (10000 entry) hosts files. 

     Note that we only do this process when bulk-reading hosts files, 
     for incremental reads, rhash is NULL, and we use cache lookups
     instead.
  */
  
  if (rhash)
    {
      /* hash address */
      for (j = 0, i = 0; i < addrlen; i++)
	j = (j*2 +((unsigned char *)addr)[i]) % hashsz;
      
      for (lookup = rhash[j]; lookup; lookup = lookup->next)
	if ((lookup->flags & cache->flags & (F_IPV4 | F_IPV6)) &&
	    memcmp(&lookup->addr.addr, addr, addrlen) == 0)
	  {
	    cache->flags &= ~F_REVERSE;
	    break;
	  }
      
      /* maintain address hash chain, insert new unique address */
      if (!lookup)
	{
	  cache->next = rhash[j];
	  rhash[j] = cache;
	}
    }
  else
    {
      /* incremental read, lookup in cache */
      lookup = cache_find_by_addr(NULL, addr, 0, cache->flags & (F_IPV4 | F_IPV6));
      if (lookup && lookup->flags & F_HOSTS)
	cache->flags &= ~F_REVERSE;
    }

  cache->uid = index;
  memcpy(&cache->addr.addr, addr, addrlen);  
  cache_hash(cache);
  make_non_terminals(cache);
  
  /* don't need to do alias stuff for second and subsequent addresses. */
  if (!nameexists)
    add_hosts_cname(cache);
}

static int eatspace(FILE *f)
{
  int c, nl = 0;

  while (1)
    {
      if ((c = getc(f)) == '#')
	while (c != '\n' && c != EOF)
	  c = getc(f);
      
      if (c == EOF)
	return 1;

      if (!isspace(c))
	{
	  ungetc(c, f);
	  return nl;
	}

      if (c == '\n')
	nl = 1;
    }
}
	 
static int gettok(FILE *f, char *token)
{
  int c, count = 0;
 
  while (1)
    {
      if ((c = getc(f)) == EOF)
	return (count == 0) ? EOF : 1;

      if (isspace(c) || c == '#')
	{
	  ungetc(c, f);
	  return eatspace(f);
	}
      
      if (count < (MAXDNAME - 1))
	{
	  token[count++] = c;
	  token[count] = 0;
	}
    }
}

int read_hostsfile(char *filename, unsigned int index, int cache_size, struct crec **rhash, int hashsz)
{  
  FILE *f = fopen(filename, "r");
  char *token = daemon->namebuff, *domain_suffix = NULL;
  int addr_count = 0, name_count = cache_size, lineno = 0;
  unsigned short flags = 0;
  struct all_addr addr;
  int atnl, addrlen = 0;

  if (!f)
    {
      my_syslog(LOG_ERR, _("failed to load names from %s: %s"), filename, strerror(errno));
      return cache_size;
    }
  
  eatspace(f);
  
  while ((atnl = gettok(f, token)) != EOF)
    {
      lineno++;
      
      if (inet_pton(AF_INET, token, &addr) > 0)
	{
	  flags = F_HOSTS | F_IMMORTAL | F_FORWARD | F_REVERSE | F_IPV4;
	  addrlen = INADDRSZ;
	  domain_suffix = get_domain(addr.addr.addr4);
	}
#ifdef HAVE_IPV6
      else if (inet_pton(AF_INET6, token, &addr) > 0)
	{
	  flags = F_HOSTS | F_IMMORTAL | F_FORWARD | F_REVERSE | F_IPV6;
	  addrlen = IN6ADDRSZ;
	  domain_suffix = get_domain6(&addr.addr.addr6);
	}
#endif
      else
	{
	  my_syslog(LOG_ERR, _("bad address at %s line %d"), filename, lineno); 
	  while (atnl == 0)
	    atnl = gettok(f, token);
	  continue;
	}
      
      addr_count++;
      
      /* rehash every 1000 names. */
      if (rhash && ((name_count - cache_size) > 1000))
	{
	  rehash(name_count);
	  cache_size = name_count;
	} 
      
      while (atnl == 0)
	{
	  struct crec *cache;
	  int fqdn, nomem;
	  char *canon;
	  
	  if ((atnl = gettok(f, token)) == EOF)
	    break;

	  fqdn = !!strchr(token, '.');

	  if ((canon = canonicalise(token, &nomem)))
	    {
	      /* If set, add a version of the name with a default domain appended */
	      if (option_bool(OPT_EXPAND) && domain_suffix && !fqdn && 
		  (cache = whine_malloc(SIZEOF_BARE_CREC + strlen(canon) + 2 + strlen(domain_suffix))))
		{
		  strcpy(cache->name.sname, canon);
		  strcat(cache->name.sname, ".");
		  strcat(cache->name.sname, domain_suffix);
		  cache->flags = flags;
		  cache->ttd = daemon->local_ttl;
		  add_hosts_entry(cache, &addr, addrlen, index, rhash, hashsz);
		  name_count++;
		}
	      if ((cache = whine_malloc(SIZEOF_BARE_CREC + strlen(canon) + 1)))
		{
		  strcpy(cache->name.sname, canon);
		  cache->flags = flags;
		  cache->ttd = daemon->local_ttl;
		  add_hosts_entry(cache, &addr, addrlen, index, rhash, hashsz);
		  name_count++;
		}
	      free(canon);
	      
	    }
	  else if (!nomem)
	    my_syslog(LOG_ERR, _("bad name at %s line %d"), filename, lineno); 
	}
    } 

  fclose(f);
  
  if (rhash)
    rehash(name_count); 
  
  my_syslog(LOG_INFO, _("read %s - %d addresses"), filename, addr_count);
  
  return name_count;
}
	    
void cache_reload(void)
{
  struct crec *cache, **up, *tmp;
  int revhashsz, i, total_size = daemon->cachesize;
  struct hostsfile *ah;
  struct host_record *hr;
  struct name_list *nl;
  struct cname *a;
  struct interface_name *intr;
#ifdef HAVE_DNSSEC
  struct ds_config *ds;
#endif

  daemon->metrics[METRIC_DNS_CACHE_INSERTED] = 0;
  daemon->metrics[METRIC_DNS_CACHE_LIVE_FREED] = 0;
  
  for (i=0; i<hash_size; i++)
    for (cache = hash_table[i], up = &hash_table[i]; cache; cache = tmp)
      {
#ifdef HAVE_DNSSEC
	cache_blockdata_free(cache);
#endif
	tmp = cache->hash_next;
	if (cache->flags & (F_HOSTS | F_CONFIG))
	  {
	    *up = cache->hash_next;
	    free(cache);
	  }
	else if (!(cache->flags & F_DHCP))
	  {
	    *up = cache->hash_next;
	    if (cache->flags & F_BIGNAME)
	      {
		cache->name.bname->next = big_free;
		big_free = cache->name.bname;
	      }
	    cache->flags = 0;
	  }
	else
	  up = &cache->hash_next;
      }
  
  /* Add CNAMEs to interface_names to the cache */
  for (a = daemon->cnames; a; a = a->next)
    for (intr = daemon->int_names; intr; intr = intr->next)
      if (a->alias[1] != '*' &&
	  hostname_isequal(a->target, intr->name) &&
	  ((cache = whine_malloc(SIZEOF_POINTER_CREC))))
	{
	  cache->flags = F_FORWARD | F_NAMEP | F_CNAME | F_IMMORTAL | F_CONFIG;
	  cache->ttd = a->ttl;
	  cache->name.namep = a->alias;
	  cache->addr.cname.target.int_name = intr;
	  cache->addr.cname.uid = SRC_INTERFACE;
	  cache->uid = UID_NONE;
	  cache_hash(cache);
	  make_non_terminals(cache);
	  add_hosts_cname(cache); /* handle chains */
	}

#ifdef HAVE_DNSSEC
  for (ds = daemon->ds; ds; ds = ds->next)
    if ((cache = whine_malloc(SIZEOF_POINTER_CREC)) &&
	(cache->addr.ds.keydata = blockdata_alloc(ds->digest, ds->digestlen)))
      {
	cache->flags = F_FORWARD | F_IMMORTAL | F_DS | F_CONFIG | F_NAMEP;
	cache->ttd = daemon->local_ttl;
	cache->name.namep = ds->name;
	cache->addr.ds.keylen = ds->digestlen;
	cache->addr.ds.algo = ds->algo;
	cache->addr.ds.keytag = ds->keytag;
	cache->addr.ds.digest = ds->digest_type;
	cache->uid = ds->class;
	cache_hash(cache);
	make_non_terminals(cache);
      }
#endif
  
  /* borrow the packet buffer for a temporary by-address hash */
  memset(daemon->packet, 0, daemon->packet_buff_sz);
  revhashsz = daemon->packet_buff_sz / sizeof(struct crec *);
  /* we overwrote the buffer... */
  daemon->srv_save = NULL;

  /* Do host_records in config. */
  for (hr = daemon->host_records; hr; hr = hr->next)
    for (nl = hr->names; nl; nl = nl->next)
      {
	if (hr->addr.s_addr != 0 &&
	    (cache = whine_malloc(SIZEOF_POINTER_CREC)))
	  {
	    cache->name.namep = nl->name;
	    cache->ttd = hr->ttl;
	    cache->flags = F_HOSTS | F_IMMORTAL | F_FORWARD | F_REVERSE | F_IPV4 | F_NAMEP | F_CONFIG;
	    add_hosts_entry(cache, (struct all_addr *)&hr->addr, INADDRSZ, SRC_CONFIG, (struct crec **)daemon->packet, revhashsz);
	  }
#ifdef HAVE_IPV6
	if (!IN6_IS_ADDR_UNSPECIFIED(&hr->addr6) &&
	    (cache = whine_malloc(SIZEOF_POINTER_CREC)))
	  {
	    cache->name.namep = nl->name;
	    cache->ttd = hr->ttl;
	    cache->flags = F_HOSTS | F_IMMORTAL | F_FORWARD | F_REVERSE | F_IPV6 | F_NAMEP | F_CONFIG;
	    add_hosts_entry(cache, (struct all_addr *)&hr->addr6, IN6ADDRSZ, SRC_CONFIG, (struct crec **)daemon->packet, revhashsz);
	  }
#endif
      }
	
  if (option_bool(OPT_NO_HOSTS) && !daemon->addn_hosts)
    {
      if (daemon->cachesize > 0)
	my_syslog(LOG_INFO, _("cleared cache"));
    }
  else
    {
      if (!option_bool(OPT_NO_HOSTS))
	total_size = read_hostsfile(HOSTSFILE, SRC_HOSTS, total_size, (struct crec **)daemon->packet, revhashsz);
      
      daemon->addn_hosts = expand_filelist(daemon->addn_hosts);
      for (ah = daemon->addn_hosts; ah; ah = ah->next)
	if (!(ah->flags & AH_INACTIVE))
	  total_size = read_hostsfile(ah->fname, ah->index, total_size, (struct crec **)daemon->packet, revhashsz);
    }

#ifdef HAVE_INOTIFY
  set_dynamic_inotify(AH_HOSTS, total_size, (struct crec **)daemon->packet, revhashsz);
#endif
  
} 

#ifdef HAVE_DHCP
struct in_addr a_record_from_hosts(char *name, time_t now)
{
  struct crec *crecp = NULL;
  struct in_addr ret;
  
  while ((crecp = cache_find_by_name(crecp, name, now, F_IPV4)))
    if (crecp->flags & F_HOSTS)
      return *(struct in_addr *)&crecp->addr;

  my_syslog(MS_DHCP | LOG_WARNING, _("No IPv4 address found for %s"), name);
  
  ret.s_addr = 0;
  return ret;
}

void cache_unhash_dhcp(void)
{
  struct crec *cache, **up;
  int i;

  for (i=0; i<hash_size; i++)
    for (cache = hash_table[i], up = &hash_table[i]; cache; cache = cache->hash_next)
      if (cache->flags & F_DHCP)
	{
	  *up = cache->hash_next;
	  cache->next = dhcp_spare;
	  dhcp_spare = cache;
	}
      else
	up = &cache->hash_next;
}

static void add_dhcp_cname(struct crec *target, time_t ttd)
{
  struct crec *aliasc;
  struct cname *a;
  
  for (a = daemon->cnames; a; a = a->next)
    if (a->alias[1] != '*' &&
	hostname_isequal(cache_get_name(target), a->target))
      {
	if ((aliasc = dhcp_spare))
	  dhcp_spare = dhcp_spare->next;
	else /* need new one */
	  aliasc = whine_malloc(SIZEOF_POINTER_CREC);
	
	if (aliasc)
	  {
	    aliasc->flags = F_FORWARD | F_NAMEP | F_DHCP | F_CNAME | F_CONFIG;
	    if (ttd == 0)
	      aliasc->flags |= F_IMMORTAL;
	    else
	      aliasc->ttd = ttd;
	    aliasc->name.namep = a->alias;
	    aliasc->addr.cname.target.cache = target;
	    next_uid(target);
	    aliasc->addr.cname.uid = target->uid;
	    aliasc->uid = UID_NONE;
	    cache_hash(aliasc);
	    make_non_terminals(aliasc);
	    add_dhcp_cname(aliasc, ttd);
	  }
      }
}

void cache_add_dhcp_entry(char *host_name, int prot,
			  struct all_addr *host_address, time_t ttd) 
{
  struct crec *crec = NULL, *fail_crec = NULL;
  unsigned short flags = F_IPV4;
  int in_hosts = 0;
  size_t addrlen = sizeof(struct in_addr);

#ifdef HAVE_IPV6
  if (prot == AF_INET6)
    {
      flags = F_IPV6;
      addrlen = sizeof(struct in6_addr);
    }
#endif
  
  inet_ntop(prot, host_address, daemon->addrbuff, ADDRSTRLEN);
  
  while ((crec = cache_find_by_name(crec, host_name, 0, flags | F_CNAME)))
    {
      /* check all addresses associated with name */
      if (crec->flags & (F_HOSTS | F_CONFIG))
	{
	  if (crec->flags & F_CNAME)
	    my_syslog(MS_DHCP | LOG_WARNING, 
		      _("%s is a CNAME, not giving it to the DHCP lease of %s"),
		      host_name, daemon->addrbuff);
	  else if (memcmp(&crec->addr.addr, host_address, addrlen) == 0)
	    in_hosts = 1;
	  else
	    fail_crec = crec;
	}
      else if (!(crec->flags & F_DHCP))
	{
	  cache_scan_free(host_name, NULL, 0, crec->flags & (flags | F_CNAME | F_FORWARD), NULL, NULL);
	  /* scan_free deletes all addresses associated with name */
	  break;
	}
    }
  
  /* if in hosts, don't need DHCP record */
  if (in_hosts)
    return;
  
  /* Name in hosts, address doesn't match */
  if (fail_crec)
    {
      inet_ntop(prot, &fail_crec->addr.addr, daemon->namebuff, MAXDNAME);
      my_syslog(MS_DHCP | LOG_WARNING, 
		_("not giving name %s to the DHCP lease of %s because "
		  "the name exists in %s with address %s"), 
		host_name, daemon->addrbuff,
		record_source(fail_crec->uid), daemon->namebuff);
      return;
    }	  
  
  if ((crec = cache_find_by_addr(NULL, (struct all_addr *)host_address, 0, flags)))
    {
      if (crec->flags & F_NEG)
	{
	  flags |= F_REVERSE;
	  cache_scan_free(NULL, (struct all_addr *)host_address, 0, flags, NULL, NULL);
	}
    }
  else
    flags |= F_REVERSE;
  
  if ((crec = dhcp_spare))
    dhcp_spare = dhcp_spare->next;
  else /* need new one */
    crec = whine_malloc(SIZEOF_POINTER_CREC);
  
  if (crec) /* malloc may fail */
    {
      crec->flags = flags | F_NAMEP | F_DHCP | F_FORWARD;
      if (ttd == 0)
	crec->flags |= F_IMMORTAL;
      else
	crec->ttd = ttd;
      crec->addr.addr = *host_address;
      crec->name.namep = host_name;
      crec->uid = UID_NONE;
      cache_hash(crec);
      make_non_terminals(crec);

      add_dhcp_cname(crec, ttd);
    }
}
#endif

/* Called when we put a local or DHCP name into the cache.
   Creates empty cache entries for subnames (ie,
   for three.two.one, for two.one and one), without
   F_IPV4 or F_IPV6 or F_CNAME set. These convert
   NXDOMAIN answers to NoData ones. */
static void make_non_terminals(struct crec *source)
{
  char *name = cache_get_name(source);
  struct crec *crecp, *tmp, **up;
  int type = F_HOSTS | F_CONFIG;
#ifdef HAVE_DHCP
  if (source->flags & F_DHCP)
    type = F_DHCP;
#endif
  
  /* First delete any empty entries for our new real name. Note that
     we only delete empty entries deriving from DHCP for a new DHCP-derived
     entry and vice-versa for HOSTS and CONFIG. This ensures that 
     non-terminals from DHCP go when we reload DHCP and 
     for HOSTS/CONFIG when we re-read. */
  for (up = hash_bucket(name), crecp = *up; crecp; crecp = tmp)
    {
      tmp = crecp->hash_next;

      if (!is_outdated_cname_pointer(crecp) &&
	  (crecp->flags & F_FORWARD) &&
	  (crecp->flags & type) &&
	  !(crecp->flags & (F_IPV4 | F_IPV6 | F_CNAME | F_DNSKEY | F_DS)) && 
	  hostname_isequal(name, cache_get_name(crecp)))
	{
	  *up = crecp->hash_next;
#ifdef HAVE_DHCP
	  if (type & F_DHCP)
	    {
	      crecp->next = dhcp_spare;
	      dhcp_spare = crecp;
	    }
	  else
#endif
	    free(crecp);
	  break;
	}
      else
	 up = &crecp->hash_next;
    }
     
  while ((name = strchr(name, '.')))
    {
      name++;

      /* Look for one existing, don't need another */
      for (crecp = *hash_bucket(name); crecp; crecp = crecp->hash_next)
	if (!is_outdated_cname_pointer(crecp) &&
	    (crecp->flags & F_FORWARD) &&
	    (crecp->flags & type) &&
	    hostname_isequal(name, cache_get_name(crecp)))
	  break;
      
      if (crecp)
	{
	  /* If the new name expires later, transfer that time to
	     empty non-terminal entry. */
	  if (!(crecp->flags & F_IMMORTAL))
	    {
	      if (source->flags & F_IMMORTAL)
		crecp->flags |= F_IMMORTAL;
	      else if (difftime(crecp->ttd, source->ttd) < 0)
		crecp->ttd = source->ttd;
	    }
	  continue;
	}
      
#ifdef HAVE_DHCP
      if ((source->flags & F_DHCP) && dhcp_spare)
	{
	  crecp = dhcp_spare;
	  dhcp_spare = dhcp_spare->next;
	}
      else
#endif
	crecp = whine_malloc(SIZEOF_POINTER_CREC);

      if (crecp)
	{
	  crecp->flags = (source->flags | F_NAMEP) & ~(F_IPV4 | F_IPV6 | F_CNAME | F_DNSKEY | F_DS | F_REVERSE);
	  crecp->ttd = source->ttd;
	  crecp->name.namep = name;
	  
	  cache_hash(crecp);
	}
    }
}

#ifndef NO_ID
int cache_make_stat(struct txt_record *t)
{ 
  static char *buff = NULL;
  static int bufflen = 60;
  int len;
  struct server *serv, *serv1;
  char *p;

  if (!buff && !(buff = whine_malloc(60)))
    return 0;

  p = buff;
  
  switch (t->stat)
    {
    case TXT_STAT_CACHESIZE:
      sprintf(buff+1, "%d", daemon->cachesize);
      break;

    case TXT_STAT_INSERTS:
      sprintf(buff+1, "%d", daemon->metrics[METRIC_DNS_CACHE_INSERTED]);
      break;

    case TXT_STAT_EVICTIONS:
      sprintf(buff+1, "%d", daemon->metrics[METRIC_DNS_CACHE_LIVE_FREED]);
      break;

    case TXT_STAT_MISSES:
      sprintf(buff+1, "%u", daemon->metrics[METRIC_DNS_QUERIES_FORWARDED]);
      break;

    case TXT_STAT_HITS:
      sprintf(buff+1, "%u", daemon->metrics[METRIC_DNS_LOCAL_ANSWERED]);
      break;

#ifdef HAVE_AUTH
    case TXT_STAT_AUTH:
      sprintf(buff+1, "%u", daemon->metrics[METRIC_DNS_AUTH_ANSWERED]);
      break;
#endif

    case TXT_STAT_SERVERS:
      /* sum counts from different records for same server */
      for (serv = daemon->servers; serv; serv = serv->next)
	serv->flags &= ~SERV_COUNTED;
      
      for (serv = daemon->servers; serv; serv = serv->next)
	if (!(serv->flags & 
	      (SERV_NO_ADDR | SERV_LITERAL_ADDRESS | SERV_COUNTED | SERV_USE_RESOLV | SERV_NO_REBIND)))
	  {
	    char *new, *lenp;
	    int port, newlen, bytes_avail, bytes_needed;
	    unsigned int queries = 0, failed_queries = 0;
	    for (serv1 = serv; serv1; serv1 = serv1->next)
	      if (!(serv1->flags & 
		    (SERV_NO_ADDR | SERV_LITERAL_ADDRESS | SERV_COUNTED | SERV_USE_RESOLV | SERV_NO_REBIND)) && 
		  sockaddr_isequal(&serv->addr, &serv1->addr))
		{
		  serv1->flags |= SERV_COUNTED;
		  queries += serv1->queries;
		  failed_queries += serv1->failed_queries;
		}
	    port = prettyprint_addr(&serv->addr, daemon->addrbuff);
	    lenp = p++; /* length */
	    bytes_avail = bufflen - (p - buff );
	    bytes_needed = snprintf(p, bytes_avail, "%s#%d %u %u", daemon->addrbuff, port, queries, failed_queries);
	    if (bytes_needed >= bytes_avail)
	      {
		/* expand buffer if necessary */
		newlen = bytes_needed + 1 + bufflen - bytes_avail;
		if (!(new = whine_malloc(newlen)))
		  return 0;
		memcpy(new, buff, bufflen);
		free(buff);
		p = new + (p - buff);
		lenp = p - 1;
		buff = new;
		bufflen = newlen;
		bytes_avail =  bufflen - (p - buff );
		bytes_needed = snprintf(p, bytes_avail, "%s#%d %u %u", daemon->addrbuff, port, queries, failed_queries);
	      }
	    *lenp = bytes_needed;
	    p += bytes_needed;
	  }
      t->txt = (unsigned char *)buff;
      t->len = p - buff;
      return 1;
    }
  
  len = strlen(buff+1);
  t->txt = (unsigned char *)buff;
  t->len = len + 1;
  *buff = len;
  return 1;
}
#endif

/* There can be names in the cache containing control chars, don't 
   mess up logging or open security holes. */
static char *sanitise(char *name)
{
  unsigned char *r;
  if (name)
    for (r = (unsigned char *)name; *r; r++)
      if (!isprint((int)*r))
	return "<name unprintable>";

  return name;
}


void dump_cache(time_t now)
{
  struct server *serv, *serv1;

  my_syslog(LOG_INFO, _("time %lu"), (unsigned long)now);
  my_syslog(LOG_INFO, _("cache size %d, %d/%d cache insertions re-used unexpired cache entries."), 
	    daemon->cachesize, daemon->metrics[METRIC_DNS_CACHE_LIVE_FREED], daemon->metrics[METRIC_DNS_CACHE_INSERTED]);
  my_syslog(LOG_INFO, _("queries forwarded %u, queries answered locally %u"), 
	    daemon->metrics[METRIC_DNS_QUERIES_FORWARDED], daemon->metrics[METRIC_DNS_LOCAL_ANSWERED]);
#ifdef HAVE_AUTH
  my_syslog(LOG_INFO, _("queries for authoritative zones %u"), daemon->metrics[METRIC_DNS_AUTH_ANSWERED]);
#endif
#ifdef HAVE_DNSSEC
  blockdata_report();
#endif

  /* sum counts from different records for same server */
  for (serv = daemon->servers; serv; serv = serv->next)
    serv->flags &= ~SERV_COUNTED;
  
  for (serv = daemon->servers; serv; serv = serv->next)
    if (!(serv->flags & 
	  (SERV_NO_ADDR | SERV_LITERAL_ADDRESS | SERV_COUNTED | SERV_USE_RESOLV | SERV_NO_REBIND)))
      {
	int port;
	unsigned int queries = 0, failed_queries = 0;
	for (serv1 = serv; serv1; serv1 = serv1->next)
	  if (!(serv1->flags & 
		(SERV_NO_ADDR | SERV_LITERAL_ADDRESS | SERV_COUNTED | SERV_USE_RESOLV | SERV_NO_REBIND)) && 
	      sockaddr_isequal(&serv->addr, &serv1->addr))
	    {
	      serv1->flags |= SERV_COUNTED;
	      queries += serv1->queries;
	      failed_queries += serv1->failed_queries;
	    }
	port = prettyprint_addr(&serv->addr, daemon->addrbuff);
	my_syslog(LOG_INFO, _("server %s#%d: queries sent %u, retried or failed %u"), daemon->addrbuff, port, queries, failed_queries);
      }
  
  if (option_bool(OPT_DEBUG) || option_bool(OPT_LOG))
    {
      struct crec *cache ;
      int i;
      my_syslog(LOG_INFO, "Host                                     Address                        Flags      Expires");
    
      for (i=0; i<hash_size; i++)
	for (cache = hash_table[i]; cache; cache = cache->hash_next)
	  {
	    char *t = " ";
	    char *a = daemon->addrbuff, *p = daemon->namebuff, *n = cache_get_name(cache);
	    *a = 0;
	    if (strlen(n) == 0 && !(cache->flags & F_REVERSE))
	      n = "<Root>";
	    p += sprintf(p, "%-30.30s ", sanitise(n));
	    if ((cache->flags & F_CNAME) && !is_outdated_cname_pointer(cache))
	      a = sanitise(cache_get_cname_target(cache));
#ifdef HAVE_DNSSEC
	    else if (cache->flags & F_DS)
	      {
		if (!(cache->flags & F_NEG))
		  sprintf(a, "%5u %3u %3u", cache->addr.ds.keytag,
			  cache->addr.ds.algo, cache->addr.ds.digest);
	      }
	    else if (cache->flags & F_DNSKEY)
	      sprintf(a, "%5u %3u %3u", cache->addr.key.keytag,
		      cache->addr.key.algo, cache->addr.key.flags);
#endif
	    else if (!(cache->flags & F_NEG) || !(cache->flags & F_FORWARD))
	      { 
		a = daemon->addrbuff;
		if (cache->flags & F_IPV4)
		  inet_ntop(AF_INET, &cache->addr.addr, a, ADDRSTRLEN);
#ifdef HAVE_IPV6
		else if (cache->flags & F_IPV6)
		  inet_ntop(AF_INET6, &cache->addr.addr, a, ADDRSTRLEN);
#endif
	      }

	    if (cache->flags & F_IPV4)
	      t = "4";
	    else if (cache->flags & F_IPV6)
	      t = "6";
	    else if (cache->flags & F_CNAME)
	      t = "C";
#ifdef HAVE_DNSSEC
	    else if (cache->flags & F_DS)
	      t = "S";
	    else if (cache->flags & F_DNSKEY)
	      t = "K";
#endif
	    p += sprintf(p, "%-40.40s %s%s%s%s%s%s%s%s%s  ", a, t,
			 cache->flags & F_FORWARD ? "F" : " ",
			 cache->flags & F_REVERSE ? "R" : " ",
			 cache->flags & F_IMMORTAL ? "I" : " ",
			 cache->flags & F_DHCP ? "D" : " ",
			 cache->flags & F_NEG ? "N" : " ",
			 cache->flags & F_NXDOMAIN ? "X" : " ",
			 cache->flags & F_HOSTS ? "H" : " ",
			 cache->flags & F_DNSSECOK ? "V" : " ");
#ifdef HAVE_BROKEN_RTC
	    p += sprintf(p, "%lu", cache->flags & F_IMMORTAL ? 0: (unsigned long)(cache->ttd - now));
#else
	    p += sprintf(p, "%s", cache->flags & F_IMMORTAL ? "\n" : ctime(&(cache->ttd)));
	    /* ctime includes trailing \n - eat it */
	    *(p-1) = 0;
#endif
	    my_syslog(LOG_INFO, "%s", daemon->namebuff);
	  }
    }
}

char *record_source(unsigned int index)
{
  struct hostsfile *ah;

  if (index == SRC_CONFIG)
    return "config";
  else if (index == SRC_HOSTS)
    return HOSTSFILE;

  for (ah = daemon->addn_hosts; ah; ah = ah->next)
    if (ah->index == index)
      return ah->fname;

#ifdef HAVE_INOTIFY
  for (ah = daemon->dynamic_dirs; ah; ah = ah->next)
     if (ah->index == index)
       return ah->fname;
#endif

  return "<unknown>";
}

char *querystr(char *desc, unsigned short type)
{
  unsigned int i;
  int len = 10; /* strlen("type=xxxxx") */
  const char *types = NULL;
  static char *buff = NULL;
  static int bufflen = 0;

  for (i = 0; i < (sizeof(typestr)/sizeof(typestr[0])); i++)
    if (typestr[i].type == type)
      {
	types = typestr[i].name;
	len = strlen(types);
	break;
      }

  if (desc)
    {
       len += 2; /* braces */
       len += strlen(desc);
    }
  len++; /* terminator */
  
  if (!buff || bufflen < len)
    {
      if (buff)
	free(buff);
      else if (len < 20)
	len = 20;
      
      buff = whine_malloc(len);
      bufflen = len;
    }

  if (buff)
    {
      if (desc)
	{
	  if (types)
	    sprintf(buff, "%s[%s]", desc, types);
	  else
	    sprintf(buff, "%s[type=%d]", desc, type);
	}
      else
	{
	  if (types)
	    sprintf(buff, "<%s>", types);
	  else
	    sprintf(buff, "type=%d", type);
	}
    }
  
  return buff ? buff : "";
}

void log_query(unsigned int flags, char *name, struct all_addr *addr, char *arg)
{
  char *source, *dest = daemon->addrbuff;
  char *verb = "is";
  
  if (!option_bool(OPT_LOG))
    return;

  name = sanitise(name);

  if (addr)
    {
      if (flags & F_KEYTAG)
	sprintf(daemon->addrbuff, arg, addr->addr.log.keytag, addr->addr.log.algo, addr->addr.log.digest);
      else if (flags & F_RCODE)
	{
	  unsigned int rcode = addr->addr.rcode.rcode;

	   if (rcode == SERVFAIL)
	     dest = "SERVFAIL";
	   else if (rcode == REFUSED)
	     dest = "REFUSED";
	   else if (rcode == NOTIMP)
	     dest = "not implemented";
	   else
	     sprintf(daemon->addrbuff, "%u", rcode);
	}
      else
	{
#ifdef HAVE_IPV6
	  inet_ntop(flags & F_IPV4 ? AF_INET : AF_INET6,
		    addr, daemon->addrbuff, ADDRSTRLEN);
#else
	  strncpy(daemon->addrbuff, inet_ntoa(addr->addr.addr4), ADDRSTRLEN);  
#endif
	}
    }
  else
    dest = arg;

  if (flags & F_REVERSE)
    {
      dest = name;
      name = daemon->addrbuff;
    }
  
  if (flags & F_NEG)
    {
      if (flags & F_NXDOMAIN)
	dest = "NXDOMAIN";
      else
	{      
	  if (flags & F_IPV4)
	    dest = "NODATA-IPv4";
	  else if (flags & F_IPV6)
	    dest = "NODATA-IPv6";
	  else
	    dest = "NODATA";
	}
    }
  else if (flags & F_CNAME)
    dest = "<CNAME>";
  else if (flags & F_RRNAME)
    dest = arg;
    
  if (flags & F_CONFIG)
    source = "config";
  else if (flags & F_DHCP)
    source = "DHCP";
  else if (flags & F_HOSTS)
    source = arg;
  else if (flags & F_UPSTREAM)
    source = "reply";
  else if (flags & F_SECSTAT)
    source = "validation";
  else if (flags & F_AUTH)
    source = "auth";
  else if (flags & F_SERVER)
    {
      source = "forwarded";
      verb = "to";
    }
  else if (flags & F_QUERY)
    {
      source = arg;
      verb = "from";
    }
  else if (flags & F_DNSSEC)
    {
      source = arg;
      verb = "to";
    }
  else if (flags & F_IPSET)
    {
      source = "ipset add";
      dest = name;
      name = arg;
      verb = daemon->addrbuff;
    }
  else
    source = "cached";
  
  if (strlen(name) == 0)
    name = ".";

  if (option_bool(OPT_EXTRALOG))
    {
      int port = prettyprint_addr(daemon->log_source_addr, daemon->addrbuff2);
      if (flags & F_NOEXTRA)
	my_syslog(LOG_INFO, "* %s/%u %s %s %s %s", daemon->addrbuff2, port, source, name, verb, dest);
      else
	my_syslog(LOG_INFO, "%u %s/%u %s %s %s %s", daemon->log_display_id, daemon->addrbuff2, port, source, name, verb, dest);
    }
  else
    my_syslog(LOG_INFO, "%s %s %s %s", source, name, verb, dest);
}