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https://github.com/brian8544/turtle-wow.git
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109 lines
3.5 KiB
C++
109 lines
3.5 KiB
C++
/************************************************************************************
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*
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* D++, A Lightweight C++ library for Discord
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*
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* Copyright 2021 Craig Edwards and D++ contributors
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* (https://github.com/brainboxdotcc/DPP/graphs/contributors)
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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************************************************************************************/
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#include <dpp/dns.h>
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#include <cerrno>
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#include <exception>
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#include <cstring>
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#include <mutex>
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#include <shared_mutex>
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#include <dpp/exception.h>
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namespace dpp
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{
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/* One hour in seconds */
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constexpr time_t one_hour = 60 * 60;
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/* Thread safety mutex for dns cache */
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std::shared_mutex dns_cache_mutex;
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/* Cache container */
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dns_cache_t dns_cache;
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const dns_cache_entry* resolve_hostname(const std::string& hostname, const std::string& port)
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{
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addrinfo hints, *addrs;
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dns_cache_t::const_iterator iter;
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time_t now = time(nullptr);
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int error;
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bool exists = false;
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/* Thread safety scope */
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{
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/* Check cache for existing DNS record. This can use a shared lock. */
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std::shared_lock dns_cache_lock(dns_cache_mutex);
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iter = dns_cache.find(hostname);
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if (iter != dns_cache.end()) {
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exists = true;
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if (now < iter->second->expire_timestamp) {
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/* there is a cached entry that is still valid, return it */
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return iter->second;
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}
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}
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}
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if (exists) {
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/* there is a cached entry, but it has expired,
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* delete and free it, and fall through to a new lookup.
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* We must use a unique lock here as we modify the cache.
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*/
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std::unique_lock dns_cache_lock(dns_cache_mutex);
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iter = dns_cache.find(hostname);
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if (iter != dns_cache.end()) { /* re-validate iter */
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delete iter->second;
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dns_cache.erase(iter);
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}
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}
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/* The hints indicate what sort of DNS results we are interested in.
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* To change this to support IPv6, one change we need to make here is
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* to change AF_INET to AF_UNSPEC. Everything else should just work fine.
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*/
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memset(&hints, 0, sizeof(addrinfo));
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hints.ai_family = AF_INET; // IPv6 explicitly unsupported by Discord
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hints.ai_socktype = SOCK_STREAM;
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hints.ai_protocol = IPPROTO_TCP;
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if ((error = getaddrinfo(hostname.c_str(), port.c_str(), &hints, &addrs))) {
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throw dpp::connection_exception(std::string("getaddrinfo error: ") + gai_strerror(error));
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}
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/* Thread safety scope */
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{
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/* Update cache, requires unique lock */
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std::unique_lock dns_cache_lock(dns_cache_mutex);
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dns_cache_entry* cache_entry = new dns_cache_entry();
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/* The sockaddr struct contains a bunch of raw pointers that we
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* must copy to the cache, before freeing it with freeaddrinfo().
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* Icky icky C APIs.
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*/
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memcpy(&cache_entry->addr, addrs, sizeof(addrinfo));
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memcpy(&cache_entry->ai_addr, addrs->ai_addr, addrs->ai_addrlen);
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cache_entry->expire_timestamp = now + one_hour;
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dns_cache[hostname] = cache_entry;
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/* Now we're done with this horrible struct, free it and return */
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freeaddrinfo(addrs);
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return cache_entry;
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}
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}
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};
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