#include "resolved-dns-cache.h"

#include "resolved-dns-packet.h"

#define CACHE_MAX 1024

#define CACHE_TTL_MAX_USEC (10 * USEC_PER_MINUTE)

typedef enum DnsCacheItemType DnsCacheItemType;

typedef struct DnsCacheItem DnsCacheItem;

enum DnsCacheItemType {

DNS_CACHE_POSITIVE,

DNS_CACHE_NODATA,

DNS_CACHE_NXDOMAIN,

};

struct DnsCacheItem {

DnsResourceKey *key;

DnsResourceRecord *rr;

usec_t until;

DnsCacheItemType type;

unsigned prioq_idx;

int owner_family;

union in_addr_union owner_address;

LIST_FIELDS(DnsCacheItem, by_key);

};

static void dns_cache_item_free(DnsCacheItem *i) {

if (!i)

return;

dns_resource_record_unref(i->rr);

dns_resource_key_unref(i->key);

free(i);

}

DEFINE_TRIVIAL_CLEANUP_FUNC(DnsCacheItem*, dns_cache_item_free);

static void dns_cache_item_remove_and_free(DnsCache *c, DnsCacheItem *i) {

DnsCacheItem *first;

assert(c);

if (!i)

return;

first = hashmap_get(c->by_key, i->key);

LIST_REMOVE(by_key, first, i);

if (first)

assert_se(hashmap_replace(c->by_key, first->key, first) >= 0);

else

hashmap_remove(c->by_key, i->key);

prioq_remove(c->by_expiry, i, &i->prioq_idx);

dns_cache_item_free(i);

}

void dns_cache_flush(DnsCache *c) {

DnsCacheItem *i;

assert(c);

while ((i = hashmap_first(c->by_key)))

dns_cache_item_remove_and_free(c, i);

assert(hashmap_size(c->by_key) == 0);

assert(prioq_size(c->by_expiry) == 0);

c->by_key = hashmap_free(c->by_key);

c->by_expiry = prioq_free(c->by_expiry);

}

static bool dns_cache_remove(DnsCache *c, DnsResourceKey *key) {

DnsCacheItem *i;

bool exist = false;

assert(c);

assert(key);

while ((i = hashmap_get(c->by_key, key))) {

dns_cache_item_remove_and_free(c, i);

exist = true;

}

return exist;

}

static void dns_cache_make_space(DnsCache *c, unsigned add) {

assert(c);

if (add <= 0)

return;

/* Makes space for n new entries. Note that we actually allow

for (;;) {

_cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;

DnsCacheItem *i;

if (prioq_size(c->by_expiry) <= 0)

break;

if (prioq_size(c->by_expiry) + add < CACHE_MAX)

break;

i = prioq_peek(c->by_expiry);

assert(i);

/* Take an extra reference to the key so that it

key = dns_resource_key_ref(i->key);

dns_cache_remove(c, key);

}

}

void dns_cache_prune(DnsCache *c) {

usec_t t = 0;

assert(c);

/* Remove all entries that are past their TTL */

for (;;) {

_cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;

DnsCacheItem *i;

i = prioq_peek(c->by_expiry);

if (!i)

break;

if (t <= 0)

t = now(clock_boottime_or_monotonic());

if (i->until > t)

break;

/* Take an extra reference to the key so that it

key = dns_resource_key_ref(i->key);

dns_cache_remove(c, key);

}

}

static int dns_cache_item_prioq_compare_func(const void *a, const void *b) {

const DnsCacheItem *x = a, *y = b;

if (x->until < y->until)

return -1;

if (x->until > y->until)

return 1;

return 0;

}

static int dns_cache_init(DnsCache *c) {

int r;

assert(c);

r = prioq_ensure_allocated(&c->by_expiry, dns_cache_item_prioq_compare_func);

if (r < 0)

return r;

r = hashmap_ensure_allocated(&c->by_key, &dns_resource_key_hash_ops);

if (r < 0)

return r;

return r;

}

static int dns_cache_link_item(DnsCache *c, DnsCacheItem *i) {

DnsCacheItem *first;

int r;

assert(c);

assert(i);

r = prioq_put(c->by_expiry, i, &i->prioq_idx);

if (r < 0)

return r;

first = hashmap_get(c->by_key, i->key);

if (first) {

LIST_PREPEND(by_key, first, i);

assert_se(hashmap_replace(c->by_key, first->key, first) >= 0);

} else {

r = hashmap_put(c->by_key, i->key, i);

if (r < 0) {

prioq_remove(c->by_expiry, i, &i->prioq_idx);

return r;

}

}

return 0;

}

static DnsCacheItem* dns_cache_get(DnsCache *c, DnsResourceRecord *rr) {

DnsCacheItem *i;

assert(c);

assert(rr);

LIST_FOREACH(by_key, i, hashmap_get(c->by_key, rr->key))

if (i->rr && dns_resource_record_equal(i->rr, rr) > 0)

return i;

return NULL;

}

static void dns_cache_item_update_positive(DnsCache *c, DnsCacheItem *i, DnsResourceRecord *rr, usec_t timestamp) {

assert(c);

assert(i);

assert(rr);

i->type = DNS_CACHE_POSITIVE;

if (!i->by_key_prev)

/* We are the first item in the list, we need to

assert_se(hashmap_replace(c->by_key, rr->key, i) >= 0);

dns_resource_record_ref(rr);

dns_resource_record_unref(i->rr);

i->rr = rr;

dns_resource_key_unref(i->key);

i->key = dns_resource_key_ref(rr->key);

i->until = timestamp + MIN(rr->ttl * USEC_PER_SEC, CACHE_TTL_MAX_USEC);

prioq_reshuffle(c->by_expiry, i, &i->prioq_idx);

}

static int dns_cache_put_positive(

DnsCache *c,

DnsResourceRecord *rr,

usec_t timestamp,

int owner_family,

const union in_addr_union *owner_address) {

_cleanup_(dns_cache_item_freep) DnsCacheItem *i = NULL;

_cleanup_free_ char *key_str = NULL;

DnsCacheItem *existing;

int r;

assert(c);

assert(rr);

assert(owner_address);

/* New TTL is 0? Delete the entry... */

if (rr->ttl <= 0) {

r = dns_resource_key_to_string(rr->key, &key_str);

if (r < 0)

return r;

if (dns_cache_remove(c, rr->key))

log_debug("Removed zero TTL entry from cache: %s", key_str);

else

log_debug("Not caching zero TTL cache entry: %s", key_str);

return 0;

}

if (rr->key->class == DNS_CLASS_ANY)

return 0;

if (rr->key->type == DNS_TYPE_ANY)

return 0;

/* Entry exists already? Update TTL and timestamp */

existing = dns_cache_get(c, rr);

if (existing) {

dns_cache_item_update_positive(c, existing, rr, timestamp);

return 0;

}

/* Otherwise, add the new RR */

r = dns_cache_init(c);

if (r < 0)

return r;

dns_cache_make_space(c, 1);

i = new0(DnsCacheItem, 1);

if (!i)

return -ENOMEM;

i->type = DNS_CACHE_POSITIVE;

i->key = dns_resource_key_ref(rr->key);

i->rr = dns_resource_record_ref(rr);

i->until = timestamp + MIN(i->rr->ttl * USEC_PER_SEC, CACHE_TTL_MAX_USEC);

i->prioq_idx = PRIOQ_IDX_NULL;

i->owner_family = owner_family;

i->owner_address = *owner_address;

r = dns_cache_link_item(c, i);

if (r < 0)

return r;

r = dns_resource_key_to_string(i->key, &key_str);

if (r < 0)

return r;

log_debug("Added cache entry for %s", key_str);

i = NULL;

return 0;

}

static int dns_cache_put_negative(

DnsCache *c,

DnsResourceKey *key,

int rcode,

usec_t timestamp,

uint32_t soa_ttl,

int owner_family,

const union in_addr_union *owner_address) {

_cleanup_(dns_cache_item_freep) DnsCacheItem *i = NULL;

_cleanup_free_ char *key_str = NULL;

int r;

assert(c);

assert(key);

assert(owner_address);

dns_cache_remove(c, key);

if (key->class == DNS_CLASS_ANY)

return 0;

if (key->type == DNS_TYPE_ANY)

return 0;

if (soa_ttl <= 0) {

r = dns_resource_key_to_string(key, &key_str);

if (r < 0)

return r;

log_debug("Not caching negative entry with zero SOA TTL: %s", key_str);

return 0;

}

if (!IN_SET(rcode, DNS_RCODE_SUCCESS, DNS_RCODE_NXDOMAIN))

return 0;

r = dns_cache_init(c);

if (r < 0)

return r;

dns_cache_make_space(c, 1);

i = new0(DnsCacheItem, 1);

if (!i)

return -ENOMEM;

i->type = rcode == DNS_RCODE_SUCCESS ? DNS_CACHE_NODATA : DNS_CACHE_NXDOMAIN;

i->key = dns_resource_key_ref(key);

i->until = timestamp + MIN(soa_ttl * USEC_PER_SEC, CACHE_TTL_MAX_USEC);

i->prioq_idx = PRIOQ_IDX_NULL;

i->owner_family = owner_family;

i->owner_address = *owner_address;

r = dns_cache_link_item(c, i);

if (r < 0)

return r;

r = dns_resource_key_to_string(i->key, &key_str);

if (r < 0)

return r;

log_debug("Added %s cache entry for %s", i->type == DNS_CACHE_NODATA ? "NODATA" : "NXDOMAIN", key_str);

i = NULL;

return 0;

}

int dns_cache_put(

DnsCache *c,

DnsResourceKey *key,

int rcode,

DnsAnswer *answer,

unsigned max_rrs,

usec_t timestamp,

int owner_family,

const union in_addr_union *owner_address) {

DnsResourceRecord *soa = NULL;

unsigned cache_keys, i;

int r;

assert(c);

if (key) {

/* First, if we were passed a key, delete all matching old RRs,

dns_cache_remove(c, key);

}

if (!answer)

return 0;

for (i = 0; i < answer->n_rrs; i++)

dns_cache_remove(c, answer->items[i].rr->key);

/* We only care for positive replies and NXDOMAINs, on all

if (!IN_SET(rcode, DNS_RCODE_SUCCESS, DNS_RCODE_NXDOMAIN))

return 0;

cache_keys = answer->n_rrs;

if (key)

cache_keys ++;

/* Make some space for our new entries */

dns_cache_make_space(c, cache_keys);

if (timestamp <= 0)

timestamp = now(clock_boottime_or_monotonic());

/* Second, add in positive entries for all contained RRs */

for (i = 0; i < MIN(max_rrs, answer->n_rrs); i++) {

r = dns_cache_put_positive(c, answer->items[i].rr, timestamp, owner_family, owner_address);

if (r < 0)

goto fail;

}

if (!key)

return 0;

/* Third, add in negative entries if the key has no RR */

r = dns_answer_contains(answer, key);

if (r < 0)

goto fail;

if (r > 0)

return 0;

/* See https://tools.ietf.org/html/rfc2308, which

r = dns_answer_find_soa(answer, key, &soa);

if (r < 0)

goto fail;

if (r == 0)

return 0;

r = dns_cache_put_negative(c, key, rcode, timestamp, MIN(soa->soa.minimum, soa->ttl), owner_family, owner_address);

if (r < 0)

goto fail;

return 0;

fail:

/* Adding all RRs failed. Let's clean up what we already

if (key)

dns_cache_remove(c, key);

for (i = 0; i < answer->n_rrs; i++)

dns_cache_remove(c, answer->items[i].rr->key);

return r;

}

static DnsCacheItem *dns_cache_get_by_key_follow_cname(DnsCache *c, DnsResourceKey *k) {

_cleanup_(dns_resource_key_unrefp) DnsResourceKey *cname_key = NULL;

DnsCacheItem *i, *j;

assert(c);

assert(k);

i = hashmap_get(c->by_key, k);

if (i || k->type == DNS_TYPE_CNAME)

return i;

/* check if we have a CNAME record instead */

cname_key = dns_resource_key_new_cname(k);

if (!cname_key)

return NULL;

j = hashmap_get(c->by_key, cname_key);

if (j)

return j;

return i;

}

int dns_cache_lookup(DnsCache *c, DnsResourceKey *key, int *rcode, DnsAnswer **ret) {

_cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;

unsigned n = 0;

int r;

bool nxdomain = false;

_cleanup_free_ char *key_str = NULL;

DnsCacheItem *j, *first;

assert(c);

assert(key);

assert(rcode);

assert(ret);

if (key->type == DNS_TYPE_ANY ||

key->class == DNS_CLASS_ANY) {

/* If we have ANY lookups we simply refresh */

r = dns_resource_key_to_string(key, &key_str);

if (r < 0)

return r;

log_debug("Ignoring cache for ANY lookup: %s", key_str);

*ret = NULL;

*rcode = DNS_RCODE_SUCCESS;

return 0;

}

first = dns_cache_get_by_key_follow_cname(c, key);

if (!first) {

/* If one question cannot be answered we need to refresh */

r = dns_resource_key_to_string(key, &key_str);

if (r < 0)

return r;

log_debug("Cache miss for %s", key_str);

*ret = NULL;

*rcode = DNS_RCODE_SUCCESS;

return 0;

}

LIST_FOREACH(by_key, j, first) {

if (j->rr)

n++;

else if (j->type == DNS_CACHE_NXDOMAIN)

nxdomain = true;

}

r = dns_resource_key_to_string(key, &key_str);

if (r < 0)

return r;

log_debug("%s cache hit for %s",

nxdomain ? "NXDOMAIN" :

n > 0 ? "Positive" : "NODATA",

key_str);

if (n <= 0) {

*ret = NULL;

*rcode = nxdomain ? DNS_RCODE_NXDOMAIN : DNS_RCODE_SUCCESS;

return 1;

}

answer = dns_answer_new(n);

if (!answer)

return -ENOMEM;

LIST_FOREACH(by_key, j, first) {

if (!j->rr)

continue;

r = dns_answer_add(answer, j->rr, 0);

if (r < 0)

return r;

}

*ret = answer;

*rcode = DNS_RCODE_SUCCESS;

answer = NULL;

return n;

}

int dns_cache_check_conflicts(DnsCache *cache, DnsResourceRecord *rr, int owner_family, const union in_addr_union *owner_address) {

DnsCacheItem *i, *first;

bool same_owner = true;

assert(cache);

assert(rr);

dns_cache_prune(cache);

/* See if there's a cache entry for the same key. If there

first = hashmap_get(cache->by_key, rr->key);

if (!first)

return 0;

/* See if the RR key is owned by the same owner, if so, there

LIST_FOREACH(by_key, i, first) {

if (i->owner_family != owner_family ||

!in_addr_equal(owner_family, &i->owner_address, owner_address)) {

same_owner = false;

break;

}

}

if (same_owner)

return 0;

/* See if there's the exact same RR in the cache. If yes, then

if (dns_cache_get(cache, rr))

return 0;

/* There's a conflict */

return 1;

}

void dns_cache_dump(DnsCache *cache, FILE *f) {

Iterator iterator;

DnsCacheItem *i;

int r;

if (!cache)

return;

if (!f)

f = stdout;

HASHMAP_FOREACH(i, cache->by_key, iterator) {

DnsCacheItem *j;

LIST_FOREACH(by_key, j, i) {

_cleanup_free_ char *t = NULL;

fputc('\t', f);

if (j->rr) {

r = dns_resource_record_to_string(j->rr, &t);

if (r < 0) {

log_oom();

continue;

}

fputs(t, f);

fputc('\n', f);

} else {

r = dns_resource_key_to_string(j->key, &t);

if (r < 0) {

log_oom();

continue;

}

fputs(t, f);

fputs(" -- ", f);

fputs(j->type == DNS_CACHE_NODATA ? "NODATA" : "NXDOMAIN", f);

fputc('\n', f);

}

}

}

}

bool dns_cache_is_empty(DnsCache *cache) {

if (!cache)

return true;

return hashmap_isempty(cache->by_key);

}