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dns_cache: synchronize access with mutex

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This commit is contained in:
Martine Lenders 2022-07-19 17:32:06 +02:00
parent bafb7d53c5
commit fe4deff522
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GPG Key ID: 2134D77A5336DD80
1 changed files with 17 additions and 7 deletions
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24
sys/net/application_layer/dns/cache.c
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@ -17,11 +17,12 @@
#include "bitfield.h"
#include "checksum/fletcher32.h"
#include "time_units.h"
#include "mutex.h"
#include "net/af.h"
#include "net/dns/cache.h"
#include "net/ipv4/addr.h"
#include "net/ipv6/addr.h"
#include "time_units.h"
#include "ztimer.h"
#define ENABLE_DEBUG 0
@ -39,6 +40,7 @@ static struct dns_cache_entry {
#endif
} addr;
} cache[CONFIG_DNS_CACHE_SIZE];
static mutex_t cache_mutex = MUTEX_INIT;
#if IS_ACTIVE(CONFIG_DNS_CACHE_A) && IS_ACTIVE(CONFIG_DNS_CACHE_AAAA)
BITFIELD(cache_is_v6, CONFIG_DNS_CACHE_SIZE);
@ -118,10 +120,12 @@ static uint32_t _hash(const void *data, size_t len)
int dns_cache_query(const char *domain_name, void *addr_out, int family)
{
int res = 0;
uint32_t now = ztimer_now(ZTIMER_MSEC) / MS_PER_SEC;
uint32_t hash = _hash(domain_name, strlen(domain_name));
uint8_t addr_len = _addr_len(family);
mutex_lock(&cache_mutex);
for (unsigned i = 0; i < CONFIG_DNS_CACHE_SIZE; ++i) {
/* empty slot */
if (_is_empty(i)) {
@ -137,12 +141,15 @@ int dns_cache_query(const char *domain_name, void *addr_out, int family)
if (cache[i].hash == hash && (!addr_len || addr_len == _get_len(i))) {
DEBUG("dns_cache[%u] hit\n", i);
memcpy(addr_out, &cache[i].addr, _get_len(i));
return _get_len(i);
res = _get_len(i);
break;
}
}
DEBUG("dns_cache miss\n");
return 0;
if (res == 0) {
DEBUG("dns_cache miss\n");
}
mutex_unlock(&cache_mutex);
return res;
}
static void _add_entry(uint8_t i, uint32_t hash, const void *addr_out,
@ -166,15 +173,16 @@ void dns_cache_add(const char *domain_name, const void *addr_out,
assert(addr_len == 4 || addr_len == 16);
DEBUG("dns_cache: lifetime of %s is %"PRIu32" s\n", domain_name, ttl);
mutex_lock(&cache_mutex);
for (unsigned i = 0; i < CONFIG_DNS_CACHE_SIZE; ++i) {
if (now > cache[i].expires || _is_empty(i)) {
_add_entry(i, hash, addr_out, addr_len, now + ttl);
return;
goto exit;
}
if (cache[i].hash == hash && _get_len(i) == addr_len) {
DEBUG("dns_cache[%u] update ttl\n", i);
cache[i].expires = now + ttl;
return;
goto exit;
}
uint32_t _ttl = cache[i].expires - now;
if (_ttl < oldest) {
@ -187,4 +195,6 @@ void dns_cache_add(const char *domain_name, const void *addr_out,
DEBUG("dns_cache: evict first entry to expire\n");
_add_entry(idx, hash, addr_out, addr_len, now + ttl);
}
exit:
mutex_unlock(&cache_mutex);
}