Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

dns_cache: synchronize access with mutex [backport 2022.07] #18342

Merged
merged 1 commit into from
Jul 20, 2022
Merged

dns_cache: synchronize access with mutex [backport 2022.07] #18342

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
24 changes: 17 additions & 7 deletions sys/net/application_layer/dns/cache.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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);
Expand Down Expand Up @@ -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)) {
Expand All @@ -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,
Expand All @@ -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) {
Expand All @@ -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);
}