req.cpp

/* SPDX-License-Identifier: MPL-2.0 */

#include "precompiled.hpp"
#include "macros.hpp"
#include "req.hpp"
#include "err.hpp"
#include "msg.hpp"
#include "wire.hpp"
#include "random.hpp"
#include "likely.hpp"

zmq::req_t::req_t (class ctx_t *parent_, uint32_t tid_, int sid_) :
    dealer_t (parent_, tid_, sid_),
    _receiving_reply (false),
    _message_begins (true),
    _reply_pipe (NULL),
    _request_id_frames_enabled (false),
    _request_id (generate_random ()),
    _strict (true)
{
    options.type = ZMQ_REQ;
}

zmq::req_t::~req_t ()
{
}

int zmq::req_t::xsend (msg_t *msg_)
{
    //  If we've sent a request and we still haven't got the reply,
    //  we can't send another request unless the strict option is disabled.
    if (_receiving_reply) {
        if (_strict) {
            errno = EFSM;
            return -1;
        }

        _receiving_reply = false;
        _message_begins = true;
    }

    //  First part of the request is the request routing id.
    if (_message_begins) {
        _reply_pipe = NULL;

        if (_request_id_frames_enabled) {
            _request_id++;

            msg_t id;
            int rc = id.init_size (sizeof (uint32_t));
            memcpy (id.data (), &_request_id, sizeof (uint32_t));
            errno_assert (rc == 0);
            id.set_flags (msg_t::more);

            rc = dealer_t::sendpipe (&id, &_reply_pipe);
            if (rc != 0) {
                return -1;
            }
        }

        msg_t bottom;
        int rc = bottom.init ();
        errno_assert (rc == 0);
        bottom.set_flags (msg_t::more);

        rc = dealer_t::sendpipe (&bottom, &_reply_pipe);
        if (rc != 0)
            return -1;
        zmq_assert (_reply_pipe);

        _message_begins = false;

        // Eat all currently available messages before the request is fully
        // sent. This is done to avoid:
        //   REQ sends request to A, A replies, B replies too.
        //   A's reply was first and matches, that is used.
        //   An hour later REQ sends a request to B. B's old reply is used.
        msg_t drop;
        while (true) {
            rc = drop.init ();
            errno_assert (rc == 0);
            rc = dealer_t::xrecv (&drop);
            if (rc != 0)
                break;
            drop.close ();
        }
    }

    bool more = (msg_->flags () & msg_t::more) != 0;

    int rc = dealer_t::xsend (msg_);
    if (rc != 0)
        return rc;

    //  If the request was fully sent, flip the FSM into reply-receiving state.
    if (!more) {
        _receiving_reply = true;
        _message_begins = true;
    }

    return 0;
}

int zmq::req_t::xrecv (msg_t *msg_)
{
    //  If request wasn't send, we can't wait for reply.
    if (!_receiving_reply) {
        errno = EFSM;
        return -1;
    }

    //  Skip messages until one with the right first frames is found.
    while (_message_begins) {
        //  If enabled, the first frame must have the correct request_id.
        if (_request_id_frames_enabled) {
            int rc = recv_reply_pipe (msg_);
            if (rc != 0)
                return rc;

            if (unlikely (!(msg_->flags () & msg_t::more)
                          || msg_->size () != sizeof (_request_id)
                          || *static_cast<uint32_t *> (msg_->data ())
                               != _request_id)) {
                //  Skip the remaining frames and try the next message
                while (msg_->flags () & msg_t::more) {
                    rc = recv_reply_pipe (msg_);
                    errno_assert (rc == 0);
                }
                continue;
            }
        }

        //  The next frame must be 0.
        // TODO: Failing this check should also close the connection with the peer!
        int rc = recv_reply_pipe (msg_);
        if (rc != 0)
            return rc;

        if (unlikely (!(msg_->flags () & msg_t::more) || msg_->size () != 0)) {
            //  Skip the remaining frames and try the next message
            while (msg_->flags () & msg_t::more) {
                rc = recv_reply_pipe (msg_);
                errno_assert (rc == 0);
            }
            continue;
        }

        _message_begins = false;
    }

    const int rc = recv_reply_pipe (msg_);
    if (rc != 0)
        return rc;

    //  If the reply is fully received, flip the FSM into request-sending state.
    if (!(msg_->flags () & msg_t::more)) {
        _receiving_reply = false;
        _message_begins = true;
    }

    return 0;
}

bool zmq::req_t::xhas_in ()
{
    //  TODO: Duplicates should be removed here.

    if (!_receiving_reply)
        return false;

    return dealer_t::xhas_in ();
}

bool zmq::req_t::xhas_out ()
{
    if (_receiving_reply && _strict)
        return false;

    return dealer_t::xhas_out ();
}

int zmq::req_t::xsetsockopt (int option_,
                             const void *optval_,
                             size_t optvallen_)
{
    const bool is_int = (optvallen_ == sizeof (int));
    int value = 0;
    if (is_int)
        memcpy (&value, optval_, sizeof (int));

    switch (option_) {
        case ZMQ_REQ_CORRELATE:
            if (is_int && value >= 0) {
                _request_id_frames_enabled = (value != 0);
                return 0;
            }
            break;

        case ZMQ_REQ_RELAXED:
            if (is_int && value >= 0) {
                _strict = (value == 0);
                return 0;
            }
            break;

        default:
            break;
    }

    return dealer_t::xsetsockopt (option_, optval_, optvallen_);
}

void zmq::req_t::xpipe_terminated (pipe_t *pipe_)
{
    if (_reply_pipe == pipe_)
        _reply_pipe = NULL;
    dealer_t::xpipe_terminated (pipe_);
}

int zmq::req_t::recv_reply_pipe (msg_t *msg_)
{
    while (true) {
        pipe_t *pipe = NULL;
        const int rc = dealer_t::recvpipe (msg_, &pipe);
        if (rc != 0)
            return rc;
        if (!_reply_pipe || pipe == _reply_pipe)
            return 0;
    }
}

zmq::req_session_t::req_session_t (io_thread_t *io_thread_,
                                   bool connect_,
                                   socket_base_t *socket_,
                                   const options_t &options_,
                                   address_t *addr_) :
    session_base_t (io_thread_, connect_, socket_, options_, addr_),
    _state (bottom)
{
}

zmq::req_session_t::~req_session_t ()
{
}

int zmq::req_session_t::push_msg (msg_t *msg_)
{
    //  Ignore commands, they are processed by the engine and should not
    //  affect the state machine.
    if (unlikely (msg_->flags () & msg_t::command))
        return 0;

    switch (_state) {
        case bottom:
            if (msg_->flags () == msg_t::more) {
                //  In case option ZMQ_CORRELATE is on, allow request_id to be
                //  transferred as first frame (would be too cumbersome to check
                //  whether the option is actually on or not).
                if (msg_->size () == sizeof (uint32_t)) {
                    _state = request_id;
                    return session_base_t::push_msg (msg_);
                }
                if (msg_->size () == 0) {
                    _state = body;
                    return session_base_t::push_msg (msg_);
                }
            }
            break;
        case request_id:
            if (msg_->flags () == msg_t::more && msg_->size () == 0) {
                _state = body;
                return session_base_t::push_msg (msg_);
            }
            break;
        case body:
            if (msg_->flags () == msg_t::more)
                return session_base_t::push_msg (msg_);
            if (msg_->flags () == 0) {
                _state = bottom;
                return session_base_t::push_msg (msg_);
            }
            break;
    }
    errno = EFAULT;
    return -1;
}

void zmq::req_session_t::reset ()
{
    session_base_t::reset ();
    _state = bottom;
}