Merge branch 'dhcpv6'

[people/ms/dnsmasq.git] / src / cache.c

/* dnsmasq is Copyright (c) 2000-2012 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 cache_inserted = 0, cache_live_freed = 0, insert_error;
static union bigname *big_free = NULL;
static int bignames_left, hash_size;
static int uid = 0;

/* 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" },
  { 33,  "SRV" },
  { 35,  "NAPTR" },
  { 36,  "KX" },
  { 37,  "CERT" },
  { 38,  "A6" },
  { 39,  "DNAME" },
  { 41,  "OPT" },
  { 48,  "DNSKEY" },
  { 249, "TKEY" },
  { 250, "TSIG" },
  { 251, "IXFR" },
  { 252, "AXFR" },
  { 253, "MAILB" },
  { 254, "MAILA" },
  { 255, "ANY" }
};

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 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++;
        }
    }
  
  /* 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;
}
 
static void cache_free(struct crec *crecp)
{
  crecp->flags &= ~F_FORWARD;
  crecp->flags &= ~F_REVERSE;
  crecp->uid = uid++; /* 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;
    }
}    

/* 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;
}

static int is_outdated_cname_pointer(struct crec *crecp)
{
  if (!(crecp->flags & F_CNAME))
    return 0;
  
  if (crecp->addr.cname.cache && crecp->addr.cname.uid == crecp->addr.cname.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 int cache_scan_free(char *name, struct all_addr *addr, time_t now, unsigned short flags)
{
  /* 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 zero 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. */
 
  struct crec *crecp, **up;
  
  if (flags & F_FORWARD)
    {
      for (up = hash_bucket(name), crecp = *up; crecp; crecp = crecp->hash_next)
        if (is_expired(now, crecp) || is_outdated_cname_pointer(crecp))
          { 
            *up = crecp->hash_next;
            if (!(crecp->flags & (F_HOSTS | F_DHCP)))
              {
                cache_unlink(crecp);
                cache_free(crecp);
              }
          } 
        else if ((crecp->flags & F_FORWARD) && 
                 ((flags & crecp->flags & (F_IPV4 | F_IPV6)) || ((crecp->flags | flags) & F_CNAME)) &&
                 hostname_isequal(cache_get_name(crecp), name))
          {
            if (crecp->flags & (F_HOSTS | F_DHCP))
              return 0;
            *up = crecp->hash_next;
            cache_unlink(crecp);
            cache_free(crecp);
          }
        else
          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)))
                { 
                  cache_unlink(crecp);
                  cache_free(crecp);
                }
            }
          else if (!(crecp->flags & (F_HOSTS | F_DHCP)) &&
                   (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 1;
}

/* 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)
{
  struct crec *new;
  union bigname *big_name = NULL;
  int freed_all = flags & F_REVERSE;
  int free_avail = 0;

  log_query(flags | F_UPSTREAM, name, addr, NULL);

  /* 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. Fail is we attempt to delete a name from
     /etc/hosts or DHCP. */
  if (!cache_scan_free(name, addr, now, flags))
    {
      insert_error = 1;
      return NULL;
    }
  
  /* Now get a cache entry from the end of the LRU list */
  while (1) {
    if (!(new = cache_tail)) /* no entries left - cache is too small, bail */
      {
        insert_error = 1;
        return NULL;
      }
    
    /* 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 (new->flags & (F_FORWARD | F_REVERSE))
      { 
        /* 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)
          {
            insert_error = 1;
            return NULL;
          }
                
        if (freed_all)
          {
            free_avail = 1; /* Must be free space now. */
            cache_scan_free(cache_get_name(new), &new->addr.addr, now, new->flags);
            cache_live_freed++;
          }
        else
          {
            cache_scan_free(NULL, NULL, now, 0);
            freed_all = 1;
          }
        continue;
      }
 
    /* Check if we need to and can allocate extra memory for a long name.
       If that fails, give up now. */
    if (name && (strlen(name) > SMALLDNAME-1))
      {
        if (big_free)
          { 
            big_name = big_free;
            big_free = big_free->next;
          }
        else if (!bignames_left ||
                 !(big_name = (union bigname *)whine_malloc(sizeof(union bigname))))
          {
            insert_error = 1;
            return NULL;
          }
        else
          bignames_left--;
        
      }

    /* Got the rest: finally grab entry. */
    cache_unlink(new);
    break;
  }
  
  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)
    new->addr.addr = *addr;
  else
    new->addr.cname.cache = NULL;
  
  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);
          cache_inserted++;
        }
      new_chain = tmp;
    }
  new_chain = NULL;
}

struct crec *cache_find_by_name(struct crec *crecp, char *name, time_t now, unsigned short prot)
{
  struct crec *ans;

  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))
                    {
                      *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)
                        {
                          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)))
                { 
                  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 short 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))
                     {
                       *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)))
                 {
                   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_entry(struct crec *cache, struct all_addr *addr, int addrlen, 
                            unsigned short flags, int index, struct crec **rhash, int hashsz)
{
  struct crec *lookup = cache_find_by_name(NULL, cache->name.sname, 0, flags & (F_IPV4 | F_IPV6));
  int i, nameexists = 0;
  struct cname *a;
  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. */
  
  /* 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 & flags & (F_IPV4 | F_IPV6)) &&
        memcmp(&lookup->addr.addr, addr, addrlen) == 0)
      {
        flags &= ~F_REVERSE;
        break;
      }
  
  /* maintain address hash chain, insert new unique address */
  if (!lookup)
    {
      cache->next = rhash[j];
      rhash[j] = cache;
    }
  
  cache->flags = flags;
  cache->uid = index;
  memcpy(&cache->addr.addr, addr, addrlen);  
  cache_hash(cache);
  
  /* don't need to do alias stuff for second and subsequent addresses. */
  if (!nameexists)
    for (a = daemon->cnames; a; a = a->next)
      if (hostname_isequal(cache->name.sname, a->target) &&
          (lookup = whine_malloc(sizeof(struct crec))))
        {
          lookup->flags = F_FORWARD | F_IMMORTAL | F_NAMEP | F_HOSTS | F_CNAME;
          lookup->name.namep = a->alias;
          lookup->addr.cname.cache = cache;
          lookup->addr.cname.uid = index;
          cache_hash(lookup);
        }
}

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;
        }
    }
}

static int read_hostsfile(char *filename, 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 0;
    }
  
  eatspace(f);
  
  while ((atnl = gettok(f, token)) != EOF)
    {
      lineno++;
      
#ifdef HAVE_IPV6      
      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);
        }
      else if (inet_pton(AF_INET6, token, &addr) > 0)
        {
          flags = F_HOSTS | F_IMMORTAL | F_FORWARD | F_REVERSE | F_IPV6;
          addrlen = IN6ADDRSZ;
          domain_suffix = daemon->domain_suffix;
        }
#else 
      if ((addr.addr.addr4.s_addr = inet_addr(token)) != (in_addr_t) -1)
        {
          flags = F_HOSTS | F_IMMORTAL | F_FORWARD | F_REVERSE | F_IPV4;
          addrlen = INADDRSZ;
          domain_suffix = get_domain(addr.addr.addr4);
        }
#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 ((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(struct crec) + 
                                        strlen(canon)+2+strlen(domain_suffix)-SMALLDNAME)))
                {
                  strcpy(cache->name.sname, canon);
                  strcat(cache->name.sname, ".");
                  strcat(cache->name.sname, domain_suffix);
                  add_hosts_entry(cache, &addr, addrlen, flags, index, rhash, hashsz);
                  name_count++;
                }
              if ((cache = whine_malloc(sizeof(struct crec) + strlen(canon)+1-SMALLDNAME)))
                {
                  strcpy(cache->name.sname, canon);
                  add_hosts_entry(cache, &addr, addrlen, flags, index, rhash, hashsz);
                  name_count++;
                }
              free(canon);
              
            }
          else if (!nomem)
            my_syslog(LOG_ERR, _("bad name at %s line %d"), filename, lineno); 
        }
    } 

  fclose(f);
  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;

  cache_inserted = cache_live_freed = 0;
  
  for (i=0; i<hash_size; i++)
    for (cache = hash_table[i], up = &hash_table[i]; cache; cache = tmp)
      {
        tmp = cache->hash_next;
        if (cache->flags & F_HOSTS)
          {
            *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;
      }
  
  if (option_bool(OPT_NO_HOSTS) && !daemon->addn_hosts)
    {
      if (daemon->cachesize > 0)
        my_syslog(LOG_INFO, _("cleared cache"));
      return;
    }
    
  /* 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;

  if (!option_bool(OPT_NO_HOSTS))
    total_size = read_hostsfile(HOSTSFILE, 0, 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);
} 

char *get_domain(struct in_addr addr)
{
  struct cond_domain *c;

  for (c = daemon->cond_domain; c; c = c->next)
    if (ntohl(addr.s_addr) >= ntohl(c->start.s_addr) &&
        ntohl(addr.s_addr) <= ntohl(c->end.s_addr))
      return c->domain;

  return daemon->domain_suffix;
}

#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;
}

void cache_add_dhcp_entry(char *host_name, 
                          struct in_addr *host_address, time_t ttd) 
{
  struct crec *crec = NULL, *aliasc;
  unsigned short flags =  F_NAMEP | F_DHCP | F_FORWARD | F_IPV4 | F_REVERSE;
  int in_hosts = 0;
  struct cname *a;
  
  while ((crec = cache_find_by_name(crec, host_name, 0, F_IPV4 | F_CNAME)))
    {
      /* check all addresses associated with name */
      if (crec->flags & F_HOSTS)
        {
          /* if in hosts, don't need DHCP record */
          in_hosts = 1;
          
          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, inet_ntoa(*host_address));
          else if (crec->addr.addr.addr.addr4.s_addr != host_address->s_addr)
            {
              strcpy(daemon->namebuff, inet_ntoa(crec->addr.addr.addr.addr4));
              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, inet_ntoa(*host_address),
                        record_source(crec->uid), daemon->namebuff);
            }     
        }
      else if (!(crec->flags & F_DHCP))
        {
          cache_scan_free(host_name, NULL, 0, crec->flags & (F_IPV4 | F_CNAME | F_FORWARD));
          /* scan_free deletes all addresses associated with name */
          break;
        }
    }
  
   if (in_hosts)
    return;

   if ((crec = cache_find_by_addr(NULL, (struct all_addr *)host_address, 0, F_IPV4)))
     {
       if (crec->flags & F_NEG)
         cache_scan_free(NULL, (struct all_addr *)host_address, 0, F_IPV4 | F_REVERSE);
       else
         /* avoid multiple reverse mappings */
         flags &= ~F_REVERSE;
     }
   
   if ((crec = dhcp_spare))
    dhcp_spare = dhcp_spare->next;
  else /* need new one */
    crec = whine_malloc(sizeof(struct crec));
  
  if (crec) /* malloc may fail */
    {
      crec->flags = flags;
      if (ttd == 0)
        crec->flags |= F_IMMORTAL;
      else
        crec->ttd = ttd;
      crec->addr.addr.addr.addr4 = *host_address;
      crec->name.namep = host_name;
      crec->uid = uid++;
      cache_hash(crec);

      for (a = daemon->cnames; a; a = a->next)
        if (hostname_isequal(host_name, a->target))
          {
            if ((aliasc = dhcp_spare))
              dhcp_spare = dhcp_spare->next;
            else /* need new one */
              aliasc = whine_malloc(sizeof(struct crec));
            
            if (aliasc)
              {
                aliasc->flags = F_FORWARD | F_NAMEP | F_DHCP | F_CNAME;
                if (ttd == 0)
                  aliasc->flags |= F_IMMORTAL;
                else
                  aliasc->ttd = ttd;
                aliasc->name.namep = a->alias;
                aliasc->addr.cname.cache = crec;
                aliasc->addr.cname.uid = crec->uid;
                cache_hash(aliasc);
              }
          }
    }
}
#endif


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, cache_live_freed, cache_inserted);
  my_syslog(LOG_INFO, _("queries forwarded %u, queries answered locally %u"), 
            daemon->queries_forwarded, daemon->local_answer);

  /* 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 *a, *p = daemon->namebuff;
            p += sprintf(p, "%-40.40s ", cache_get_name(cache));
            if ((cache->flags & F_NEG) && (cache->flags & F_FORWARD))
              a = ""; 
            else if (cache->flags & F_CNAME) 
              {
                a = "";
                if (!is_outdated_cname_pointer(cache))
                  a = cache_get_name(cache->addr.cname.cache);
              }
#ifdef HAVE_IPV6
            else 
              { 
                a = daemon->addrbuff;
                if (cache->flags & F_IPV4)
                  inet_ntop(AF_INET, &cache->addr.addr, a, ADDRSTRLEN);
                else if (cache->flags & F_IPV6)
                  inet_ntop(AF_INET6, &cache->addr.addr, a, ADDRSTRLEN);
              }
#else
            else 
              a = inet_ntoa(cache->addr.addr.addr.addr4);
#endif
            p += sprintf(p, "%-30.30s %s%s%s%s%s%s%s%s%s%s  ", a, 
                         cache->flags & F_IPV4 ? "4" : "",
                         cache->flags & F_IPV6 ? "6" : "",
                         cache->flags & F_CNAME ? "C" : "",
                         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" : " ");
#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, daemon->namebuff);
          }
    }
}

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

  if (index == 0)
    return HOSTSFILE;

  for (ah = daemon->addn_hosts; ah; ah = ah->next)
    if (ah->index == index)
      return ah->fname;
  
  return "<unknown>";
}

void querystr(char *str, unsigned short type)
{
  unsigned int i;
  
  sprintf(str, "query[type=%d]", type); 
  for (i = 0; i < (sizeof(typestr)/sizeof(typestr[0])); i++)
    if (typestr[i].type == type)
      sprintf(str,"query[%s]", typestr[i].name);
}

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;

  if (addr)
    {
#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
    }

  if (flags & F_REVERSE)
    {
      dest = name;
      name = daemon->addrbuff;
    }
  
  if (flags & F_NEG)
    {
      if (flags & F_NXDOMAIN)
        {
          if (flags & F_IPV4)
            dest = "NXDOMAIN-IPv4";
          else if (flags & F_IPV6)
            dest = "NXDOMAIN-IPv6";
          else
            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_SERVER)
    {
      source = "forwarded";
      verb = "to";
    }
  else if (flags & F_QUERY)
    {
      source = arg;
      verb = "from";
    }
  else
    source = "cached";
  
  if (strlen(name) == 0)
    name = ".";

  my_syslog(LOG_INFO, "%s %s %s %s", source, name, verb, dest);
}