transmission/libtransmission/global-ip-cache.h

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// This file Copyright © 2023-2023 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#include <array>
#include <atomic>
#include <condition_variable>
#include <chrono> // std::chrono::milliseconds
#include <memory> // std::unique_ptr
#include <mutex>
#include <optional>
#include <shared_mutex>
#include <string_view>
#include "libtransmission/net.h"
#include "libtransmission/timer.h"
#include "libtransmission/web.h"
#pragma once
#ifndef __TRANSMISSION__
#error only libtransmission should #include this header.
#endif
/**
* Cache global IP addresses.
*
* This class caches 3 useful info:
* 1. Whether your machine supports the IP protocol
* 2. Source address used for global connections
* 3. Global address
*
* The idea is, if this class successfully cached a source address, that means
* you have connectivity to the public internet. And if the global address is
* the same as the source address, then you are not behind a NAT.
*
*/
class tr_global_ip_cache
{
public:
struct Mediator
{
virtual ~Mediator() = default;
virtual void fetch(tr_web::FetchOptions&& /* options */)
{
}
[[nodiscard]] virtual std::string_view settings_bind_addr(tr_address_type /* type */)
{
return {};
}
[[nodiscard]] virtual libtransmission::TimerMaker& timer_maker() = 0;
};
private:
explicit tr_global_ip_cache(Mediator& mediator_in);
public:
[[nodiscard]] static std::unique_ptr<tr_global_ip_cache> create(Mediator& mediator_in);
tr_global_ip_cache() = delete;
~tr_global_ip_cache();
tr_global_ip_cache(tr_global_ip_cache const&) = delete;
tr_global_ip_cache(tr_global_ip_cache&&) = delete;
tr_global_ip_cache& operator=(tr_global_ip_cache const&) = delete;
tr_global_ip_cache& operator=(tr_global_ip_cache&&) = delete;
bool try_shutdown() noexcept;
[[nodiscard]] std::optional<tr_address> global_addr(tr_address_type type) const noexcept
{
auto const lock = std::shared_lock{ global_addr_mutex_[type] };
return global_addr_[type];
}
[[nodiscard]] std::optional<tr_address> global_source_addr(tr_address_type type) const noexcept
{
auto const lock = std::shared_lock{ source_addr_mutex_[type] };
return source_addr_[type];
}
[[nodiscard]] tr_address bind_addr(tr_address_type type) const noexcept;
bool set_global_addr(tr_address_type type, tr_address const& addr) noexcept;
void update_addr(tr_address_type type) noexcept;
void update_global_addr(tr_address_type type) noexcept;
void update_source_addr(tr_address_type type) noexcept;
// Only use as a callback for web_->fetch()
void on_response_ip_query(tr_address_type type, tr_web::FetchResponse const& response) noexcept;
[[nodiscard]] constexpr auto has_ip_protocol(tr_address_type type) const noexcept
{
return has_ip_protocol_[type];
}
private:
template<typename T>
using array_ip_t = std::array<T, NUM_TR_AF_INET_TYPES>;
void unset_global_addr(tr_address_type type) noexcept;
void set_source_addr(tr_address const& addr) noexcept;
void unset_addr(tr_address_type type) noexcept;
void start_timer(tr_address_type type, std::chrono::milliseconds msec) noexcept
{
upkeep_timers_[type]->start_repeating(msec);
}
void stop_timer(tr_address_type type) noexcept
{
upkeep_timers_[type]->stop();
}
[[nodiscard]] bool set_is_updating(tr_address_type type) noexcept;
void unset_is_updating(tr_address_type type) noexcept;
Mediator& mediator_;
enum class is_updating_t
{
NO = 0,
YES,
ABORT
};
array_ip_t<is_updating_t> is_updating_ = {};
array_ip_t<std::mutex> is_updating_mutex_;
array_ip_t<std::condition_variable> is_updating_cv_;
// Never directly read/write IP addresses for the sake of being thread safe
// Use global_*_addr() for read, and set_*_addr()/unset_*_addr() for write instead
mutable array_ip_t<std::shared_mutex> global_addr_mutex_;
array_ip_t<std::optional<tr_address>> global_addr_;
mutable array_ip_t<std::shared_mutex> source_addr_mutex_;
array_ip_t<std::optional<tr_address>> source_addr_;
// Keep the timer at the bottom of the class definition so that it will be destructed first
// We don't want it to trigger after the IP addresses have been destroyed
// (The destructor will acquire the IP address locks before proceeding, but still)
array_ip_t<std::unique_ptr<libtransmission::Timer>> upkeep_timers_;
// Whether this machine supports this IP protocol
array_ip_t<bool> has_ip_protocol_ = { true, true };
array_ip_t<std::atomic_size_t> ix_service_ = {};
};