router.cpp

/*
    Copyright (c) 2007-2016 Contributors as noted in the AUTHORS file

    This file is part of libzmq, the ZeroMQ core engine in C++.

    libzmq is free software; you can redistribute it and/or modify it under
    the terms of the GNU Lesser General Public License (LGPL) as published
    by the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    As a special exception, the Contributors give you permission to link
    this library with independent modules to produce an executable,
    regardless of the license terms of these independent modules, and to
    copy and distribute the resulting executable under terms of your choice,
    provided that you also meet, for each linked independent module, the
    terms and conditions of the license of that module. An independent
    module is a module which is not derived from or based on this library.
    If you modify this library, you must extend this exception to your
    version of the library.

    libzmq is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
    License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "macros.hpp"
#include "router.hpp"
#include "pipe.hpp"
#include "wire.hpp"
#include "random.hpp"
#include "likely.hpp"
#include "err.hpp"

zmq::router_t::router_t (class ctx_t *parent_, uint32_t tid_, int sid_) :
    socket_base_t (parent_, tid_, sid_),
    prefetched (false),
    identity_sent (false),
    current_in (NULL),
    terminate_current_in (false),
    more_in (false),
    current_out (NULL),
    more_out (false),
    next_rid (generate_random ()),
    mandatory (false),
    //  raw_socket functionality in ROUTER is deprecated
    raw_socket (false),
    probe_router (false),
    handover (false)
{
    options.type = ZMQ_ROUTER;
    options.recv_identity = true;
    options.raw_socket = false;

    prefetched_id.init ();
    prefetched_msg.init ();
}

zmq::router_t::~router_t ()
{
    zmq_assert (anonymous_pipes.empty ());;
    zmq_assert (outpipes.empty ());
    prefetched_id.close ();
    prefetched_msg.close ();
}

void zmq::router_t::xattach_pipe (pipe_t *pipe_, bool subscribe_to_all_)
{
    LIBZMQ_UNUSED (subscribe_to_all_);

    zmq_assert (pipe_);

    if (probe_router) {
        msg_t probe_msg_;
        int rc = probe_msg_.init ();
        errno_assert (rc == 0);

        rc = pipe_->write (&probe_msg_);
        // zmq_assert (rc) is not applicable here, since it is not a bug.
        pipe_->flush ();

        rc = probe_msg_.close ();
        errno_assert (rc == 0);
    }

    bool identity_ok = identify_peer (pipe_);
    if (identity_ok)
        fq.attach (pipe_);
    else
        anonymous_pipes.insert (pipe_);
}

int zmq::router_t::xsetsockopt (int option_, const void *optval_,
    size_t optvallen_)
{
    bool is_int = (optvallen_ == sizeof (int));
    int value = is_int? *((int *) optval_): 0;

    switch (option_) {
        case ZMQ_CONNECT_RID:
            if (optval_ && optvallen_) {
                connect_rid.assign ((char *) optval_, optvallen_);
                return 0;
            }
            break;

        case ZMQ_ROUTER_RAW:
            if (is_int && value >= 0) {
                raw_socket = (value != 0);
                if (raw_socket) {
                    options.recv_identity = false;
                    options.raw_socket = true;
                }
                return 0;
            }
            break;

        case ZMQ_ROUTER_MANDATORY:
            if (is_int && value >= 0) {
                mandatory = (value != 0);
                return 0;
            }
            break;

        case ZMQ_PROBE_ROUTER:
            if (is_int && value >= 0) {
                probe_router = (value != 0);
                return 0;
            }
            break;

        case ZMQ_ROUTER_HANDOVER:
            if (is_int && value >= 0) {
                handover = (value != 0);
                return 0;
            }
            break;

        default:
            break;
    }
    errno = EINVAL;
    return -1;
}


void zmq::router_t::xpipe_terminated (pipe_t *pipe_)
{
    std::set <pipe_t*>::iterator it = anonymous_pipes.find (pipe_);
    if (it != anonymous_pipes.end ())
        anonymous_pipes.erase (it);
    else {
        outpipes_t::iterator it = outpipes.find (pipe_->get_identity ());
        zmq_assert (it != outpipes.end ());
        outpipes.erase (it);
        fq.pipe_terminated (pipe_);
        if (pipe_ == current_out)
            current_out = NULL;
    }
}

void zmq::router_t::xread_activated (pipe_t *pipe_)
{
    std::set <pipe_t*>::iterator it = anonymous_pipes.find (pipe_);
    if (it == anonymous_pipes.end ())
        fq.activated (pipe_);
    else {
        bool identity_ok = identify_peer (pipe_);
        if (identity_ok) {
            anonymous_pipes.erase (it);
            fq.attach (pipe_);
        }
    }
}

void zmq::router_t::xwrite_activated (pipe_t *pipe_)
{
    outpipes_t::iterator it;
    for (it = outpipes.begin (); it != outpipes.end (); ++it)
        if (it->second.pipe == pipe_)
            break;

    zmq_assert (it != outpipes.end ());
    zmq_assert (!it->second.active);
    it->second.active = true;
}

int zmq::router_t::xsend (msg_t *msg_)
{
    //  If this is the first part of the message it's the ID of the
    //  peer to send the message to.
    if (!more_out) {
        zmq_assert (!current_out);

        //  If we have malformed message (prefix with no subsequent message)
        //  then just silently ignore it.
        //  TODO: The connections should be killed instead.
        if (msg_->flags () & msg_t::more) {

            more_out = true;

            //  Find the pipe associated with the identity stored in the prefix.
            //  If there's no such pipe just silently ignore the message, unless
            //  router_mandatory is set.
            blob_t identity ((unsigned char*) msg_->data (), msg_->size ());
            outpipes_t::iterator it = outpipes.find (identity);

            if (it != outpipes.end ()) {
                current_out = it->second.pipe;
                if (!current_out->check_write ()) {
                    it->second.active = false;
                    current_out = NULL;
                    if (mandatory) {
                        more_out = false;
                        errno = EAGAIN;
                        return -1;
                    }
                }
            }
            else
            if (mandatory) {
                more_out = false;
                errno = EHOSTUNREACH;
                return -1;
            }
        }

        int rc = msg_->close ();
        errno_assert (rc == 0);
        rc = msg_->init ();
        errno_assert (rc == 0);
        return 0;
    }

    //  Ignore the MORE flag for raw-sock or assert?
    if (options.raw_socket)
        msg_->reset_flags (msg_t::more);

    //  Check whether this is the last part of the message.
    more_out = msg_->flags () & msg_t::more ? true : false;

    //  Push the message into the pipe. If there's no out pipe, just drop it.
    if (current_out) {

        // Close the remote connection if user has asked to do so
        // by sending zero length message.
        // Pending messages in the pipe will be dropped (on receiving term- ack)
        if (raw_socket && msg_->size() == 0) {
            current_out->terminate (false);
            int rc = msg_->close ();
            errno_assert (rc == 0);
            rc = msg_->init ();
            errno_assert (rc == 0);
            current_out = NULL;
            return 0;
        }

        bool ok = current_out->write (msg_);
        if (unlikely (!ok)) {
            // Message failed to send - we must close it ourselves.
            int rc = msg_->close ();
            errno_assert (rc == 0);
            current_out = NULL;
        } else {
          if (!more_out) {
              current_out->flush ();
              current_out = NULL;
          }
        }
    }
    else {
        int rc = msg_->close ();
        errno_assert (rc == 0);
    }

    //  Detach the message from the data buffer.
    int rc = msg_->init ();
    errno_assert (rc == 0);

    return 0;
}

int zmq::router_t::xrecv (msg_t *msg_)
{
    if (prefetched) {
        if (!identity_sent) {
            int rc = msg_->move (prefetched_id);
            errno_assert (rc == 0);
            identity_sent = true;
        }
        else {
            int rc = msg_->move (prefetched_msg);
            errno_assert (rc == 0);
            prefetched = false;
        }
        more_in = msg_->flags () & msg_t::more ? true : false;
 
        if (!more_in) {
            if (terminate_current_in) {
                current_in->terminate (true);
                terminate_current_in = false;
            }
            current_in = NULL;
        }
        return 0;
    }

    pipe_t *pipe = NULL;
    int rc = fq.recvpipe (msg_, &pipe);

    //  It's possible that we receive peer's identity. That happens
    //  after reconnection. The current implementation assumes that
    //  the peer always uses the same identity.
    while (rc == 0 && msg_->is_identity ())
        rc = fq.recvpipe (msg_, &pipe);

    if (rc != 0)
        return -1;

    zmq_assert (pipe != NULL);

    //  If we are in the middle of reading a message, just return the next part.
    if (more_in) {
        more_in = msg_->flags () & msg_t::more ? true : false;

        if (!more_in) {
            if (terminate_current_in) {
                current_in->terminate (true);
                terminate_current_in = false;
            }
            current_in = NULL;
        }
    }
    else {
        //  We are at the beginning of a message.
        //  Keep the message part we have in the prefetch buffer
        //  and return the ID of the peer instead.
        rc = prefetched_msg.move (*msg_);
        errno_assert (rc == 0);
        prefetched = true;
        current_in = pipe;

        blob_t identity = pipe->get_identity ();
        rc = msg_->init_size (identity.size ());
        errno_assert (rc == 0);
        memcpy (msg_->data (), identity.data (), identity.size ());
        msg_->set_flags (msg_t::more);
        if (prefetched_msg.metadata())
            msg_->set_metadata(prefetched_msg.metadata());
        identity_sent = true;
    }

    return 0;
}

int zmq::router_t::rollback (void)
{
    if (current_out) {
        current_out->rollback ();
        current_out = NULL;
        more_out = false;
    }
    return 0;
}

bool zmq::router_t::xhas_in ()
{
    //  If we are in the middle of reading the messages, there are
    //  definitely more parts available.
    if (more_in)
        return true;

    //  We may already have a message pre-fetched.
    if (prefetched)
        return true;

    //  Try to read the next message.
    //  The message, if read, is kept in the pre-fetch buffer.
    pipe_t *pipe = NULL;
    int rc = fq.recvpipe (&prefetched_msg, &pipe);

    //  It's possible that we receive peer's identity. That happens
    //  after reconnection. The current implementation assumes that
    //  the peer always uses the same identity.
    //  TODO: handle the situation when the peer changes its identity.
    while (rc == 0 && prefetched_msg.is_identity ())
        rc = fq.recvpipe (&prefetched_msg, &pipe);

    if (rc != 0)
        return false;

    zmq_assert (pipe != NULL);

    blob_t identity = pipe->get_identity ();
    rc = prefetched_id.init_size (identity.size ());
    errno_assert (rc == 0);
    memcpy (prefetched_id.data (), identity.data (), identity.size ());
    prefetched_id.set_flags (msg_t::more);

    prefetched = true;
    identity_sent = false;
    current_in = pipe;

    return true;
}

bool zmq::router_t::xhas_out ()
{
    //  In theory, ROUTER socket is always ready for writing. Whether actual
    //  attempt to write succeeds depends on which pipe the message is going
    //  to be routed to.
    return true;
}

zmq::blob_t zmq::router_t::get_credential () const
{
    return fq.get_credential ();
}

bool zmq::router_t::identify_peer (pipe_t *pipe_)
{
    msg_t msg;
    blob_t identity;
    bool ok;

    if (connect_rid.length()) {
        identity = blob_t ((unsigned char*) connect_rid.c_str (),
            connect_rid.length());
        connect_rid.clear ();
        outpipes_t::iterator it = outpipes.find (identity);
        if (it != outpipes.end ())
            zmq_assert(false); //  Not allowed to duplicate an existing rid
    }
    else
    if (options.raw_socket) { //  Always assign identity for raw-socket
        unsigned char buf [5];
        buf [0] = 0;
        put_uint32 (buf + 1, next_rid++);
        identity = blob_t (buf, sizeof buf);
    }
    else
    if (!options.raw_socket) {
        //  Pick up handshake cases and also case where next identity is set
        msg.init ();
        ok = pipe_->read (&msg);
        if (!ok)
            return false;

        if (msg.size () == 0) {
            //  Fall back on the auto-generation
            unsigned char buf [5];
            buf [0] = 0;
            put_uint32 (buf + 1, next_rid++);
            identity = blob_t (buf, sizeof buf);
            msg.close ();
        }
        else {
            identity = blob_t ((unsigned char*) msg.data (), msg.size ());
            outpipes_t::iterator it = outpipes.find (identity);
            msg.close ();

            if (it != outpipes.end ()) {
                if (!handover)
                    //  Ignore peers with duplicate ID
                    return false;
                else {
                    //  We will allow the new connection to take over this
                    //  identity. Temporarily assign a new identity to the
                    //  existing pipe so we can terminate it asynchronously.
                    unsigned char buf [5];
                    buf [0] = 0;
                    put_uint32 (buf + 1, next_rid++);
                    blob_t new_identity = blob_t (buf, sizeof buf);

                    it->second.pipe->set_identity (new_identity);
                    outpipe_t existing_outpipe =
                        {it->second.pipe, it->second.active};

                    ok = outpipes.insert (outpipes_t::value_type (
                        new_identity, existing_outpipe)).second;
                    zmq_assert (ok);

                    //  Remove the existing identity entry to allow the new
                    //  connection to take the identity.
                    outpipes.erase (it);

                    if (existing_outpipe.pipe == current_in)
                        terminate_current_in = true;
                    else
                        existing_outpipe.pipe->terminate (true);
                }
            }
        }
    }

    pipe_->set_identity (identity);
    //  Add the record into output pipes lookup table
    outpipe_t outpipe = {pipe_, true};
    ok = outpipes.insert (outpipes_t::value_type (identity, outpipe)).second;
    zmq_assert (ok);

    return true;
}