BaseWSPeer.h

#pragma once
 
#include <xrpl/basics/safe_cast.h>
#include <xrpl/beast/utility/Journal.h>
#include <xrpl/beast/utility/instrumentation.h>
#include <xrpl/beast/utility/rngfill.h>
#include <xrpl/crypto/csprng.h>
#include <xrpl/protocol/BuildInfo.h>
#include <xrpl/server/Handoff.h>
#include <xrpl/server/Port.h>
#include <xrpl/server/WSSession.h>
#include <xrpl/server/detail/BasePeer.h>
#include <xrpl/server/detail/LowestLayer.h>
 
#include <boost/asio/error.hpp>
#include <boost/beast/core/multi_buffer.hpp>
#include <boost/beast/http/message.hpp>
#include <boost/beast/websocket.hpp>
#include <boost/logic/tribool.hpp>
 
#include <algorithm>
#include <chrono>
#include <cstddef>
#include <functional>
#include <iterator>
#include <list>
#include <memory>
#include <string_view>
#include <utility>
#include <vector>
 
namespace xrpl {

template <class Handler, class Impl>
class BaseWSPeer : public BasePeer<Handler, Impl>, public WSSession
{
protected:
    using ClockType = std::chrono::system_clock;
    using ErrorCode = boost::system::error_code;
    using EndpointType = boost::asio::ip::tcp::endpoint;
    using WaitableTimer = boost::asio::basic_waitable_timer<ClockType>;
    using BasePeer<Handler, Impl>::strand_;
 
private:
    friend class BasePeer<Handler, Impl>;
 
    HttpRequestType request_;
    boost::beast::multi_buffer rb_;
    boost::beast::multi_buffer wb_;
    std::list<std::shared_ptr<WSMsg>> wq_;
    bool doClose_ = false;
    boost::beast::websocket::close_reason cr_;
    WaitableTimer timer_;
    bool closeOnTimer_ = false;
    bool pingActive_ = false;
    boost::beast::websocket::ping_data payload_;
    ErrorCode ec_;
    std::function<void(boost::beast::websocket::frame_type, std::string_view)> controlCallback_;
 
public:
    template <class Body, class Headers>
    BaseWSPeer(
        Port const& port,
        Handler& handler,
        boost::asio::executor const& executor,
        WaitableTimer timer,
        EndpointType remoteAddress,
        boost::beast::http::request<Body, Headers>&& request,
        beast::Journal journal);
 
    void
    run() override;
 
    //
    // WSSession
    //
 
    [[nodiscard]] Port const&
    port() const override
    {
        return this->port_;
    }
 
    [[nodiscard]] HttpRequestType const&
    request() const override
    {
        return this->request_;
    }
 
    [[nodiscard]] boost::asio::ip::tcp::endpoint const&
    remoteEndpoint() const override
    {
        return this->remoteAddress_;
    }
 
    void
    send(std::shared_ptr<WSMsg> w) override;
 
    void
    close() override;
 
    void
    close(boost::beast::websocket::close_reason const& reason) override;
 
    void
    complete() override;
 
protected:
    Impl&
    impl()
    {
        return *static_cast<Impl*>(this);
    }
 
    void
    onWsHandshake(ErrorCode const& ec);
 
    void
    doWrite();
 
    void
    onWrite(ErrorCode const& ec);
 
    void
    onWriteFin(ErrorCode const& ec);
 
    void
    doRead();
 
    void
    onRead(ErrorCode const& ec);
 
    void
    onClose(ErrorCode const& ec);
 
    void
    startTimer();
 
    void
    cancelTimer();
 
    void
    onPing(ErrorCode const& ec);
 
    void
    onPingPong(boost::beast::websocket::frame_type kind, std::string_view payload);
 
    void
    onTimer(ErrorCode ec);
 
    template <class String>
    void
    fail(ErrorCode ec, String const& what);
};
 
//------------------------------------------------------------------------------
 
template <class Handler, class Impl>
template <class Body, class Headers>
BaseWSPeer<Handler, Impl>::BaseWSPeer(
    Port const& port,
    Handler& handler,
    boost::asio::executor const& executor,
    WaitableTimer timer,
    EndpointType remoteAddress,
    boost::beast::http::request<Body, Headers>&& request,
    beast::Journal journal)
    : BasePeer<Handler, Impl>(port, handler, executor, remoteAddress, journal)
    , request_(std::move(request))
    , timer_(std::move(timer))
    , payload_("12345678")  // ensures size is 8 bytes
{
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::run()
{
    if (!strand_.running_in_this_thread())
        return post(strand_, [self = impl().shared_from_this()] { self->run(); });
    impl().ws_.set_option(port().pmdOptions);
    // Must manage the control callback memory outside of the `control_callback`
    // function
    controlCallback_ = [this](boost::beast::websocket::frame_type kind, std::string_view payload) {
        onPingPong(kind, payload);
    };
    impl().ws_.control_callback(controlCallback_);
    startTimer();
    closeOnTimer_ = true;
    impl().ws_.set_option(boost::beast::websocket::stream_base::decorator([](auto& res) {
        res.set(boost::beast::http::field::server, build_info::getFullVersionString());
    }));
    impl().ws_.async_accept(
        request_, bind_executor(strand_, [self = impl().shared_from_this()](ErrorCode const& ec) {
            self->onWsHandshake(ec);
        }));
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::send(std::shared_ptr<WSMsg> w)
{
    if (!strand_.running_in_this_thread())
    {
        return post(
            strand_, [self = impl().shared_from_this(), w = std::move(w)] { self->send(w); });
    }
    if (doClose_)
        return;
    if (wq_.size() > port().wsQueueLimit)
    {
        cr_.code = safeCast<decltype(cr_.code)>(boost::beast::websocket::close_code::policy_error);
        cr_.reason = "Policy error: client is too slow.";
        JLOG(this->j_.info()) << cr_.reason;
        wq_.erase(std::next(wq_.begin()), wq_.end());
        close(cr_);
        return;
    }
    wq_.emplace_back(std::move(w));
    if (wq_.size() == 1)
        onWrite({});
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::close()
{
    close(boost::beast::websocket::close_reason{});
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::close(boost::beast::websocket::close_reason const& reason)
{
    if (!strand_.running_in_this_thread())
        return post(strand_, [self = impl().shared_from_this(), reason] { self->close(reason); });
    if (doClose_)
        return;
    doClose_ = true;
    if (wq_.empty())
    {
        impl().ws_.async_close(
            reason,
            bind_executor(
                strand_, [self = impl().shared_from_this()](boost::beast::error_code const& ec) {
                    self->onClose(ec);
                }));
    }
    else
    {
        cr_ = reason;
    }
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::complete()
{
    if (!strand_.running_in_this_thread())
        return post(strand_, [self = impl().shared_from_this()] { self->complete(); });
    doRead();
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::onWsHandshake(ErrorCode const& ec)
{
    if (ec)
        return fail(ec, "on_ws_handshake");
    closeOnTimer_ = false;
    doRead();
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::doWrite()
{
    if (!strand_.running_in_this_thread())
        return post(strand_, [self = impl().shared_from_this()] { self->doWrite(); });
    onWrite({});
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::onWrite(ErrorCode const& ec)
{
    if (ec)
        return fail(ec, "write");
    auto& w = *wq_.front();
    auto const result = w.prepare(65536, [self = impl().shared_from_this()] { self->doWrite(); });
    if (boost::indeterminate(result.first))
        return;
    startTimer();
    if (!result.first)
    {
        impl().ws_.async_write_some(
            static_cast<bool>(result.first),
            result.second,
            bind_executor(
                strand_, [self = impl().shared_from_this()](ErrorCode const& ec, std::size_t) {
                    self->onWrite(ec);
                }));
    }
    else
    {
        impl().ws_.async_write_some(
            static_cast<bool>(result.first),
            result.second,
            bind_executor(
                strand_, [self = impl().shared_from_this()](ErrorCode const& ec, std::size_t) {
                    self->onWriteFin(ec);
                }));
    }
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::onWriteFin(ErrorCode const& ec)
{
    if (ec)
        return fail(ec, "write_fin");
    wq_.pop_front();
    if (doClose_)
    {
        impl().ws_.async_close(
            cr_, bind_executor(strand_, [self = impl().shared_from_this()](ErrorCode const& ec) {
                self->onClose(ec);
            }));
    }
    else if (!wq_.empty())
    {
        onWrite({});
    }
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::doRead()
{
    if (!strand_.running_in_this_thread())
        return post(strand_, [self = impl().shared_from_this()] { self->doRead(); });
    impl().ws_.async_read(
        rb_,
        bind_executor(
            strand_, [self = impl().shared_from_this()](ErrorCode const& ec, std::size_t) {
                self->onRead(ec);
            }));
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::onRead(ErrorCode const& ec)
{
    if (ec == boost::beast::websocket::error::closed)
        return onClose({});
    if (ec)
        return fail(ec, "read");
    auto const& data = rb_.data();
    std::vector<boost::asio::const_buffer> b;
    b.reserve(std::distance(data.begin(), data.end()));
    std::ranges::copy(data, std::back_inserter(b));
    this->handler_.onWSMessage(impl().shared_from_this(), b);
    rb_.consume(rb_.size());
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::onClose(ErrorCode const& ec)
{
    cancelTimer();
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::startTimer()
{
    // Max seconds without completing a message
    static constexpr std::chrono::seconds kTimeout{30};
    static constexpr std::chrono::seconds kTimeoutLocal{3};
 
    try
    {
        timer_.expires_after(remoteEndpoint().address().is_loopback() ? kTimeoutLocal : kTimeout);
    }
    catch (boost::system::system_error const& e)
    {
        return fail(e.code(), "start_timer");
    }
 
    timer_.async_wait(bind_executor(
        strand_, [self = impl().shared_from_this()](ErrorCode const& ec) { self->onTimer(ec); }));
}
 
// Convenience for discarding the error code
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::cancelTimer()
{
    try
    {
        timer_.cancel();
    }
    catch (boost::system::system_error const&)  // NOLINT(bugprone-empty-catch)
    {
        // ignored
    }
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::onPing(ErrorCode const& ec)
{
    if (ec == boost::asio::error::operation_aborted)
        return;
    pingActive_ = false;
    if (!ec)
        return;
    fail(ec, "on_ping");
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::onPingPong(
    boost::beast::websocket::frame_type kind,
    std::string_view payload)
{
    if (kind == boost::beast::websocket::frame_type::pong)
    {
        std::string_view const p(payload_.begin(), payload_.size());
        if (payload == p)
        {
            closeOnTimer_ = false;
            JLOG(this->j_.trace()) << "got matching pong";
        }
        else
        {
            JLOG(this->j_.trace()) << "got pong";
        }
    }
}
 
template <class Handler, class Impl>
void
BaseWSPeer<Handler, Impl>::onTimer(ErrorCode ec)
{
    if (ec == boost::asio::error::operation_aborted)
        return;
    if (!ec)
    {
        if (!closeOnTimer_ || !pingActive_)
        {
            startTimer();
            closeOnTimer_ = true;
            pingActive_ = true;
            // cryptographic is probably overkill..
            beast::rngfill(payload_.begin(), payload_.size(), cryptoPrng());
            impl().ws_.async_ping(
                payload_,
                bind_executor(strand_, [self = impl().shared_from_this()](ErrorCode const& ec) {
                    self->onPing(ec);
                }));
            JLOG(this->j_.trace()) << "sent ping";
            return;
        }
        ec = boost::system::errc::make_error_code(boost::system::errc::timed_out);
    }
    fail(ec, "timer");
}
 
template <class Handler, class Impl>
template <class String>
void
BaseWSPeer<Handler, Impl>::fail(ErrorCode ec, String const& what)
{
    XRPL_ASSERT(strand_.running_in_this_thread(), "xrpl::BaseWSPeer::fail : strand in this thread");
 
    cancelTimer();
    if (!ec_ && ec != boost::asio::error::operation_aborted)
    {
        ec_ = ec;
        JLOG(this->j_.trace()) << what << ": " << ec.message();
        xrpl::getLowestLayer(impl().ws_).socket().close(ec);
    }
}
 
}  // namespace xrpl