loop-uh
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95 lines
3.2 KiB
C++
95 lines
3.2 KiB
C++
/*
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This file is part of Telegram Desktop,
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the official desktop application for the Telegram messaging service.
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For license and copyright information please follow this link:
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https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
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*/
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#pragma once
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#include "base/basic_types.h"
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#include "mtproto/proxy/data.h"
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#include <crl/crl_time.h>
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namespace MTP {
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class RuntimeEnvironment;
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namespace details {
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// Paces outgoing connection attempts towards a single proxy server.
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//
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// Every session dials on its own, so a cold start or a proxy switch makes
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// every session of every account open its socket in the same millisecond.
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// Some public mtproxies take that batch in stride; others answer the first
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// two or three handshakes and silently drop the rest, which the client then
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// reads as client_hello_sent_no_server_hello or connected_no_mtproto_data
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// across everything that did not get in.
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//
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// Which kind a relay is cannot be known before dialing it, so the limit is
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// not a constant: it starts at what a client asks for anyway and is raised
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// by proof, never lowered below concurrency the relay has already answered.
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//
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// A lease is taken when a connection is created and lives until the attempt
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// either proves the relay or dies, so the limit counts unproven handshakes
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// and not established connections: a steady state of many live sessions is
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// fine, only the burst is spread out.
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//
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// A run of attempts that never proved anything also stretches the spacing,
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// which is the only thing standing between a blackholed proxy and every
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// session redialing it on its own eight second retry timer. This is a rate
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// limiter and nothing more: it does not mark endpoints unhealthy, does not
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// pick proxies and never touches the handshake shape.
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class ProxyDialLease final {
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public:
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ProxyDialLease() = default;
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ProxyDialLease(const ProxyDialLease &other) = delete;
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ProxyDialLease &operator=(const ProxyDialLease &other) = delete;
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ProxyDialLease(ProxyDialLease &&other) noexcept;
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ProxyDialLease &operator=(ProxyDialLease &&other) noexcept;
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~ProxyDialLease();
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// How long the caller must wait before starting the attempt.
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[[nodiscard]] crl::time delay() const;
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// The proxy relayed a Telegram reply through this attempt.
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void proven();
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// The attempt is over without having proved anything.
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void release();
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// The attempt is being dropped for a reason of ours - it lost a route
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// race, or the proxy was switched under it. The slot comes back, but the
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// proxy did nothing wrong and is not moved towards the failure spacing.
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void cancel();
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private:
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friend ProxyDialLease ReserveProxyDial(
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not_null<RuntimeEnvironment*> runtime,
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const ProxyData &proxy);
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ProxyDialLease(QString key, crl::time delay);
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enum class Verdict {
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Proven,
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Failed,
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Cancelled,
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};
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void finish(Verdict verdict);
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QString _key;
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crl::time _delay = 0;
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};
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// Only MTProxy handshakes are paced. SOCKS, HTTP and WEB proxies have their
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// own connection semantics (WEB in particular multiplexes logical streams
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// over one browser carrier), so for them this returns an empty lease with a
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// zero delay.
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[[nodiscard]] ProxyDialLease ReserveProxyDial(
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not_null<RuntimeEnvironment*> runtime,
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const ProxyData &proxy);
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} // namespace details
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} // namespace MTP
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