xref: /aosp_15_r20/external/dnsmasq/src/cache.c (revision c2c26c8b25cb2c9c4fe49a734c2305a522f5635e)

/* dnsmasq is Copyright (c) 2000-2009 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;
static char* addrbuff = NULL;

/* 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;

    if (daemon->options & OPT_LOG) addrbuff = safe_malloc(ADDRSTRLEN);

    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_DHCP | F_CONFIG))
        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);

    /* CONFIG bit means something else when stored in cache entries */
    flags &= ~F_CONFIG;

    /* 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;
        int 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, int addr_dup) {
    struct crec* lookup = cache_find_by_name(NULL, cache->name.sname, 0, flags & (F_IPV4 | F_IPV6));
    int i, nameexists = 0;
    struct cname* a;

    /* 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, first we see if the address is the same as
       the last one we saw, which eliminates most in the case of an ad-block
       file with thousands of entries for the same address.
       Then we search and bail at the first matching address that came from
       a HOSTS file. Since the first host entry gets reverse, we know
       then that it must exist without searching exhaustively for it. */

    if (addr_dup)
        flags &= ~F_REVERSE;
    else
        for (i = 0; i < hash_size; i++) {
            for (lookup = hash_table[i]; lookup; lookup = lookup->hash_next)
                if ((lookup->flags & F_HOSTS) && (lookup->flags & flags & (F_IPV4 | F_IPV6)) &&
                    memcmp(&lookup->addr.addr, addr, addrlen) == 0) {
                    flags &= ~F_REVERSE;
                    break;
                }
            if (lookup) break;
        }

    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_CONFIG | 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) {
    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, saved_flags = 0;
    struct all_addr addr, saved_addr;
    int atnl, addrlen = 0, addr_dup;

    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) {
        addr_dup = 0;
        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;
        }

        if (saved_flags == flags && memcmp(&addr, &saved_addr, addrlen) == 0)
            addr_dup = 1;
        else {
            saved_flags = flags;
            saved_addr = addr;
        }

        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 ((daemon->options & 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, addr_dup);
                    addr_dup = 1;
                    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, addr_dup);
                    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 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 ((daemon->options & OPT_NO_HOSTS) && !daemon->addn_hosts) {
        if (daemon->cachesize > 0) my_syslog(LOG_INFO, _("cleared cache"));
        return;
    }

    if (!(daemon->options & OPT_NO_HOSTS)) total_size = read_hostsfile(HOSTSFILE, 0, total_size);

    for (i = 0, ah = daemon->addn_hosts; ah; ah = ah->next) {
        if (i <= ah->index) i = ah->index + 1;

        if (ah->flags & AH_DIR)
            ah->flags |= AH_INACTIVE;
        else
            ah->flags &= ~AH_INACTIVE;
    }

    for (ah = daemon->addn_hosts; ah; ah = ah->next)
        if (!(ah->flags & AH_INACTIVE)) {
            struct stat buf;
            if (stat(ah->fname, &buf) != -1 && S_ISDIR(buf.st_mode)) {
                DIR* dir_stream;
                struct dirent* ent;

                /* don't read this as a file */
                ah->flags |= AH_INACTIVE;

                if (!(dir_stream = opendir(ah->fname)))
                    my_syslog(LOG_ERR, _("cannot access directory %s: %s"), ah->fname,
                              strerror(errno));
                else {
                    while ((ent = readdir(dir_stream))) {
                        size_t lendir = strlen(ah->fname);
                        size_t lenfile = strlen(ent->d_name);
                        struct hostsfile* ah1;
                        char* path;

                        /* ignore emacs backups and dotfiles */
                        if (lenfile == 0 || ent->d_name[lenfile - 1] == '~' ||
                            (ent->d_name[0] == '#' && ent->d_name[lenfile - 1] == '#') ||
                            ent->d_name[0] == '.')
                            continue;

                        /* see if we have an existing record.
                           dir is ah->fname
                           file is ent->d_name
                           path to match is ah1->fname */

                        for (ah1 = daemon->addn_hosts; ah1; ah1 = ah1->next) {
                            if (lendir < strlen(ah1->fname) &&
                                strstr(ah1->fname, ah->fname) == ah1->fname &&
                                ah1->fname[lendir] == '/' &&
                                strcmp(ah1->fname + lendir + 1, ent->d_name) == 0) {
                                ah1->flags &= ~AH_INACTIVE;
                                break;
                            }
                        }

                        /* make new record */
                        if (!ah1) {
                            if (!(ah1 = whine_malloc(sizeof(struct hostsfile)))) continue;

                            if (!(path = whine_malloc(lendir + lenfile + 2))) {
                                free(ah1);
                                continue;
                            }

                            strcpy(path, ah->fname);
                            strcat(path, "/");
                            strcat(path, ent->d_name);
                            ah1->fname = path;
                            ah1->index = i++;
                            ah1->flags = AH_DIR;
                            ah1->next = daemon->addn_hosts;
                            daemon->addn_hosts = ah1;
                        }

                        /* inactivate record if not regular file */
                        if ((ah1->flags & AH_DIR) && stat(ah1->fname, &buf) != -1 &&
                            !S_ISREG(buf.st_mode))
                            ah1->flags |= AH_INACTIVE;
                    }
                    closedir(dir_stream);
                }
            }
        }

    for (ah = daemon->addn_hosts; ah; ah = ah->next)
        if (!(ah->flags & AH_INACTIVE))
            total_size = read_hostsfile(ah->fname, ah->index, total_size);
}

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
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_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 (crec->addr.addr.addr.addr4.s_addr != host_address->s_addr) {
                strcpy(daemon->namebuff, inet_ntoa(crec->addr.addr.addr.addr4));
                my_syslog(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);
                return;
            } else
                /* if in hosts, don't need DHCP record */
                in_hosts = 1;
        } 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_CONFIG | 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);

    if (!addrbuff && !(addrbuff = whine_malloc(ADDRSTRLEN))) return;

    /* 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))) {
            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)) &&
                    sockaddr_isequal(&serv->addr, &serv1->addr)) {
                    serv1->flags |= SERV_COUNTED;
                    queries += serv1->queries;
                    failed_queries += serv1->failed_queries;
                }
            port = prettyprint_addr(&serv->addr, addrbuff);
            my_syslog(LOG_INFO, _("server %s#%d: queries sent %u, retried or failed %u"), addrbuff,
                      port, queries, failed_queries);
        }

    if ((daemon->options & (OPT_DEBUG | OPT_LOG))) {
        struct crec* cache;
        int i;
        my_syslog(LOG_DEBUG,
                  "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 = addrbuff;
                    if (cache->flags & F_IPV4)
                        inet_ntop(AF_INET, &cache->addr.addr, addrbuff, ADDRSTRLEN);
                    else if (cache->flags & F_IPV6)
                        inet_ntop(AF_INET6, &cache->addr.addr, addrbuff, 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_DEBUG, 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 short flags, char* name, struct all_addr* addr, char* arg) {
    char *source, *dest = addrbuff;
    char* verb = "is";

    if (!(daemon->options & OPT_LOG)) return;

    if (addr) {
#ifdef HAVE_IPV6
        /* TODO: support scoped addresses. struct all_addr doesn't store scope IDs. */
        inet_ntop(flags & F_IPV4 ? AF_INET : AF_INET6, addr, addrbuff, ADDRSTRLEN);
#else
        strncpy(addrbuff, inet_ntoa(addr->addr.addr4), ADDRSTRLEN);
#endif
    }

    if (flags & F_REVERSE) {
        dest = name;
        name = 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) {
        /* nasty abuse of NXDOMAIN and CNAME flags */
        if (flags & F_NXDOMAIN)
            dest = arg;
        else
            dest = "<CNAME>";
    }

    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_DEBUG, "%s %s %s %s", source, name, verb, dest);
}