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[Net] Fix IP address resolution incorrectly locking the main thread. #51199

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Aug 3, 2021
Merged

[Net] Fix IP address resolution incorrectly locking the main thread. #51199

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63 changes: 44 additions & 19 deletions core/io/ip.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -83,8 +83,23 @@ struct _IP_ResolverPrivate {
continue;
}

IP::get_singleton()->_resolve_hostname(queue[i].response, queue[i].hostname, queue[i].type);
queue[i].status.set(queue[i].response.is_empty() ? IP::RESOLVER_STATUS_ERROR : IP::RESOLVER_STATUS_DONE);
mutex.lock();
List<IPAddress> response;
String hostname = queue[i].hostname;
IP::Type type = queue[i].type;
mutex.unlock();

// We should not lock while resolving the hostname,
// only when modifying the queue.
IP::get_singleton()->_resolve_hostname(response, hostname, type);

MutexLock lock(mutex);
// Could have been completed by another function, or deleted.
if (queue[i].status.get() != IP::RESOLVER_STATUS_WAITING) {
continue;
}
queue[i].response = response;
queue[i].status.set(response.is_empty() ? IP::RESOLVER_STATUS_ERROR : IP::RESOLVER_STATUS_DONE);
}
}

Expand All @@ -93,8 +108,6 @@ struct _IP_ResolverPrivate {

while (!ipr->thread_abort) {
ipr->sem.wait();

MutexLock lock(ipr->mutex);
ipr->resolve_queues();
}
}
Expand All @@ -107,17 +120,23 @@ struct _IP_ResolverPrivate {
};

IPAddress IP::resolve_hostname(const String &p_hostname, IP::Type p_type) {
MutexLock lock(resolver->mutex);

List<IPAddress> res;

String key = _IP_ResolverPrivate::get_cache_key(p_hostname, p_type);

resolver->mutex.lock();
if (resolver->cache.has(key)) {
res = resolver->cache[key];
} else {
// This should be run unlocked so the resolver thread can keep
// resolving other requests.
resolver->mutex.unlock();
_resolve_hostname(res, p_hostname, p_type);
resolver->mutex.lock();
// We might be overriding another result, but we don't care (they are the
// same hostname).
resolver->cache[key] = res;
}
resolver->mutex.unlock();

for (int i = 0; i < res.size(); ++i) {
if (res[i].is_valid()) {
Expand All @@ -128,14 +147,23 @@ IPAddress IP::resolve_hostname(const String &p_hostname, IP::Type p_type) {
}

Array IP::resolve_hostname_addresses(const String &p_hostname, Type p_type) {
MutexLock lock(resolver->mutex);

List<IPAddress> res;
String key = _IP_ResolverPrivate::get_cache_key(p_hostname, p_type);
if (!resolver->cache.has(key)) {
_resolve_hostname(resolver->cache[key], p_hostname, p_type);
}

List<IPAddress> res = resolver->cache[key];
resolver->mutex.lock();
if (resolver->cache.has(key)) {
res = resolver->cache[key];
} else {
// This should be run unlocked so the resolver thread can keep resolving
// other requests.
resolver->mutex.unlock();
_resolve_hostname(res, p_hostname, p_type);
resolver->mutex.lock();
// We might be overriding another result, but we don't care (they are the
// same hostname).
resolver->cache[key] = res;
}
resolver->mutex.unlock();

Array result;
for (int i = 0; i < res.size(); ++i) {
Expand Down Expand Up @@ -178,13 +206,12 @@ IP::ResolverID IP::resolve_hostname_queue_item(const String &p_hostname, IP::Typ
IP::ResolverStatus IP::get_resolve_item_status(ResolverID p_id) const {
ERR_FAIL_INDEX_V(p_id, IP::RESOLVER_MAX_QUERIES, IP::RESOLVER_STATUS_NONE);

MutexLock lock(resolver->mutex);
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if (resolver->queue[p_id].status.get() == IP::RESOLVER_STATUS_NONE) {
IP::ResolverStatus res = resolver->queue[p_id].status.get();
if (res == IP::RESOLVER_STATUS_NONE) {
ERR_PRINT("Condition status == IP::RESOLVER_STATUS_NONE");
return IP::RESOLVER_STATUS_NONE;
}
return resolver->queue[p_id].status.get();
return res;
}

IPAddress IP::get_resolve_item_address(ResolverID p_id) const {
Expand Down Expand Up @@ -230,8 +257,6 @@ Array IP::get_resolve_item_addresses(ResolverID p_id) const {
void IP::erase_resolve_item(ResolverID p_id) {
ERR_FAIL_INDEX(p_id, IP::RESOLVER_MAX_QUERIES);

MutexLock lock(resolver->mutex);

resolver->queue[p_id].status.set(IP::RESOLVER_STATUS_NONE);
}

Expand Down