mpmd: Refactor MPM transport architecture, use managers

This splits up the transport code in mpmd_impl across multiple classes
to properly leverage the request_xport/commit_xport API in MPM.
Different types of transport (UDP, liberio) use their own distinct
classes, which are generated dynamically on request.

This is a true refactoring despite the large amount of changes; there
are no functional differences.

Reviewed-By: Brent Stapleton <brent.stapleton@ettus.com>
Reviewed-By: Trung Tran <trung.tran@ettus.com>
Reviewed-By: Ashish Chaudhari <ashish.chaudhari@ettus.com>

12 files changed, 843 insertions, 404 deletions

diff --git a/host/lib/usrp/mpmd/CMakeLists.txt b/host/lib/usrp/mpmd/CMakeLists.txt
index 5bc8e2d08..e4ce0e316 100644
--- a/host/lib/usrp/mpmd/CMakeLists.txt
+++ b/host/lib/usrp/mpmd/CMakeLists.txt
@@ -17,14 +17,23 @@
 
 IF(ENABLE_MPMD)
     IF(ENABLE_LIBERIO)
-        MESSAGE(STATUS "Compiling MPM with liberio support...")
-	ADD_DEFINITIONS(-DHAVE_LIBERIO)
+        MESSAGE(STATUS "Compiling MPMD with liberio support...")
+        ADD_DEFINITIONS(-DHAVE_LIBERIO)
     ENDIF(ENABLE_LIBERIO)
 
     LIBUHD_APPEND_SOURCES(
+        ${CMAKE_CURRENT_SOURCE_DIR}/mpmd_image_loader.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/mpmd_impl.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/mpmd_mboard_impl.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/mpmd_xport.cpp
-        ${CMAKE_CURRENT_SOURCE_DIR}/mpmd_image_loader.cpp
+        ${CMAKE_CURRENT_SOURCE_DIR}/mpmd_xport_mgr.cpp
+        ${CMAKE_CURRENT_SOURCE_DIR}/mpmd_xport_ctrl_udp.cpp
     )
+
+    IF(ENABLE_LIBERIO)
+        LIBUHD_APPEND_SOURCES(
+            ${CMAKE_CURRENT_SOURCE_DIR}/mpmd_xport_ctrl_liberio.cpp
+        )
+    ENDIF(ENABLE_LIBERIO)
+
 ENDIF(ENABLE_MPMD)
diff --git a/host/lib/usrp/mpmd/mpmd_impl.cpp b/host/lib/usrp/mpmd/mpmd_impl.cpp
index d020e3546..92f8039a4 100644
--- a/host/lib/usrp/mpmd/mpmd_impl.cpp
+++ b/host/lib/usrp/mpmd/mpmd_impl.cpp
@@ -1,18 +1,7 @@
 //
-// Copyright 2017 Ettus Research (National Instruments)
+// Copyright 2017 Ettus Research, a National Instruments Company
 //
-// This program is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// This program 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 General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+// SPDX-License-Identifier: GPL-3.0
 //
 
 #include "mpmd_impl.hpp"
@@ -39,6 +28,7 @@
 #include <vector>
 
 using namespace uhd;
+using namespace uhd::mpmd;
 
 namespace {
     /*************************************************************************
@@ -274,6 +264,14 @@ namespace {
     }
 }
 
+
+/*****************************************************************************
+ * Static class attributes
+ ****************************************************************************/
+const std::string mpmd_impl::MPM_RPC_GET_LAST_ERROR_CMD = "get_last_error";
+const std::string mpmd_impl::MPM_DISCOVERY_CMD = "MPM-DISC";
+const std::string mpmd_impl::MPM_ECHO_CMD = "MPM-ECHO";
+
 /*****************************************************************************
  * Structors
  ****************************************************************************/
@@ -285,15 +283,6 @@ mpmd_impl::mpmd_impl(const device_addr_t& device_args)
     UHD_LOGGER_INFO("MPMD")
         << "Initializing device with args: " << device_args.to_string();
 
-    for (const std::string& key : device_args.keys()) {
-        if (key.find("recv") != std::string::npos) {
-            recv_args[key] = device_args[key];
-        }
-        if (key.find("send") != std::string::npos) {
-            send_args[key] = device_args[key];
-        }
-    }
-
     const device_addrs_t mb_args = separate_device_addr(device_args);
     _mb.reserve(mb_args.size());
 
@@ -506,13 +495,18 @@ device_addrs_t mpmd_find_with_addr(const device_addr_t& hint_)
     }
 
     transport::udp_simple::sptr comm = transport::udp_simple::make_broadcast(
-        query_addr, std::to_string(MPM_DISCOVERY_PORT));
+        query_addr, std::to_string(mpmd_impl::MPM_DISCOVERY_PORT));
     comm->send(
-        boost::asio::buffer(&MPM_DISCOVERY_CMD, sizeof(MPM_DISCOVERY_CMD)));
+        boost::asio::buffer(
+            mpmd_impl::MPM_DISCOVERY_CMD.c_str(),
+            mpmd_impl::MPM_DISCOVERY_CMD.size()
+        )
+    );
     while (true) {
-        char buff[4096] = {};
-        const size_t nbytes = comm->recv( // TODO make sure we don't buf overflow
-                boost::asio::buffer(buff),
+        const size_t MAX_MTU = 8000;
+        char buff[MAX_MTU] = {};
+        const size_t nbytes = comm->recv(
+                boost::asio::buffer(buff, MAX_MTU),
                 MPMD_FIND_TIMEOUT
         );
         if (nbytes == 0) {
diff --git a/host/lib/usrp/mpmd/mpmd_impl.hpp b/host/lib/usrp/mpmd/mpmd_impl.hpp
index 3143378dd..7b81be0f6 100644
--- a/host/lib/usrp/mpmd/mpmd_impl.hpp
+++ b/host/lib/usrp/mpmd/mpmd_impl.hpp
@@ -1,22 +1,13 @@
 //
-// Copyright 2017 Ettus Research (National Instruments)
+// Copyright 2017 Ettus Research, a National Instruments Company
 //
-// This program is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// This program 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 General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+// SPDX-License-Identifier: GPL-3.0
 //
 
 #ifndef INCLUDED_MPMD_IMPL_HPP
 #define INCLUDED_MPMD_IMPL_HPP
+
+#include "mpmd_xport_mgr.hpp"
 #include "../../utils/rpc.hpp"
 #include "../device3/device3_impl.hpp"
 #include <uhd/stream.hpp>
@@ -25,17 +16,9 @@
 #include <uhd/utils/tasks.hpp>
 #include <uhd/transport/muxed_zero_copy_if.hpp>
 #include <map>
+#include <memory>
 
-static const size_t MPMD_RX_SW_BUFF_SIZE_ETH        = 0x2000000;//32MiB    For an ~8k frame size any size >32MiB is just wasted buffer space
-static const size_t MPMD_RX_SW_BUFF_SIZE_ETH_MACOS  = 0x100000; //1Mib
-
-static const size_t MPM_DISCOVERY_PORT = 49600;
-static const size_t MPM_RPC_PORT = 49601;
-static const char MPM_RPC_GET_LAST_ERROR_CMD[] = "get_last_error";
-static const char MPM_DISCOVERY_CMD[] = "MPM-DISC";
-static const char MPM_ECHO_CMD[] = "MPM-ECHO";
-static const size_t MPMD_10GE_DATA_FRAME_MAX_SIZE = 8000; // CHDR packet size in bytes
-
+namespace uhd { namespace mpmd {
 
 /*! Stores all attributes specific to a single MPM device
  */
@@ -93,28 +76,42 @@ class mpmd_mboard_impl
     /*************************************************************************
      * API
      ************************************************************************/
-    uhd::sid_t allocate_sid(const uint16_t port,
-                            const uhd::sid_t address,
-                            const uint32_t xbar_src_addr,
-                            const uint32_t xbar_src_dst,
-                            const uint32_t dst_addr
-                            );
-
     //! Configure a crossbar to have a certain local address
     void set_xbar_local_addr(const size_t xbar_index, const size_t local_addr);
 
     //! Return the local address of a given crossbar
-    size_t get_xbar_local_addr(const size_t xbar_index) {
+    size_t get_xbar_local_addr(const size_t xbar_index) const {
         return xbar_local_addrs.at(xbar_index);
     }
 
+    //! Device-specific make_transport implementation
+    //
+    // A major difference to the mpmd_impl::make_transport() is the meaning of
+    // the first argument (\p sid). mpmd_impl::make_transport() will add a
+    // source part to the SID which needs to be taken into account in this
+    // function.
+    //
+    // \param sid The full SID of this transport (UHD to device)
+    // \param xport_type Transport type (CTRL, RX_DATA, ...)
+    // \param args Any kind of args passed in via get_?x_stream()
+    uhd::both_xports_t make_transport(
+        const sid_t& sid,
+        usrp::device3_impl::xport_type_t xport_type,
+        const uhd::device_addr_t& args
+    );
+
+
+    uhd::device_addr_t get_rx_hints() const;
+    uhd::device_addr_t get_tx_hints() const;
+
   private:
     /*************************************************************************
      * Private methods
      ************************************************************************/
     /*! Renew the claim onto the device.
      *
-     * This is meant to be called repeatedly, e.g., using a UHD task.
+     * This is meant to be called repeatedly, e.g., using a UHD task. See also
+     * _claimer_task.
      */
     bool claim();
 
@@ -130,10 +127,11 @@ class mpmd_mboard_impl
     // what we use when addressing a crossbar in a CHDR header.
     std::vector<size_t> xbar_local_addrs;
 
-
     /*! Continuously reclaims the device.
      */
     uhd::task::sptr _claimer_task;
+
+    uhd::mpmd::xport::mpmd_xport_mgr::uptr _xport_mgr;
 };
 
 
@@ -145,16 +143,36 @@ class mpmd_mboard_impl
  */
 class mpmd_impl : public uhd::usrp::device3_impl
 {
-  public:
+public:
+    //! Port on which the discovery process is listening
+    static const size_t MPM_DISCOVERY_PORT = 49600;
+    //! Port on which the RPC process is listening
+    static const size_t MPM_RPC_PORT = 49601;
+    //! This is the command that needs to be sent to the discovery port to
+    // trigger a response.
+    static const std::string MPM_DISCOVERY_CMD;
+    //! This is the command that will let you measure ping responses from the
+    // device via the discovery process. Useful for MTU discovery.
+    static const std::string MPM_ECHO_CMD;
+    //! This is the RPC command that will return the last known error from MPM.
+    static const std::string MPM_RPC_GET_LAST_ERROR_CMD;
+
+    /**************************************************************************
+     * Structors
+     ************************************************************************/
     mpmd_impl(const uhd::device_addr_t& device_addr);
     ~mpmd_impl();
 
+    /**************************************************************************
+     * API
+     ************************************************************************/
     uhd::both_xports_t make_transport(const uhd::sid_t&,
                                       uhd::usrp::device3_impl::xport_type_t,
                                       const uhd::device_addr_t&);
 
   private:
     uhd::device_addr_t get_rx_hints(size_t mb_index);
+    uhd::device_addr_t get_tx_hints(size_t mb_index);
 
     /*************************************************************************
      * Private methods/helpers
@@ -185,49 +203,14 @@ class mpmd_impl : public uhd::usrp::device3_impl
      */
     size_t allocate_xbar_local_addr();
 
-    /*! Return the index of the motherboard carrying the crossbar at \p remote_addr
+    /*! Return the index of the motherboard given the local address of a
+     * crossbar
      */
-    size_t identify_mboard_by_sid(const size_t remote_addr);
-
-    using xport_info_t = std::map<std::string, std::string>;
-    using xport_info_list_t = std::vector<std::map<std::string, std::string>>;
-
-    uhd::both_xports_t make_transport_udp(
-        const size_t mb_index,
-        xport_info_t &xport_info,
-        const xport_type_t xport_type,
-        const uhd::device_addr_t& xport_args
-    );
-
-#ifdef HAVE_LIBERIO
-    /*! Create a muxed liberio transport for control packets */
-    uhd::transport::muxed_zero_copy_if::sptr make_muxed_liberio_xport(
-            const std::string &tx_dev,
-            const std::string &rx_dev,
-            const uhd::transport::zero_copy_xport_params &buff_args,
-            const size_t max_muxed_ports
-    );
-
-    uhd::both_xports_t make_transport_liberio(
-        const size_t mb_index,
-        xport_info_t &xport_info,
-        const xport_type_t xport_type,
-        const uhd::device_addr_t& xport_args
-    );
-#endif
+    size_t identify_mboard_by_xbar_addr(const size_t xbar_addr) const;
 
     /*************************************************************************
      * Private attributes
      ************************************************************************/
-    // FIXME move the next two into their own transport manager class
-    //! Control transport for one liberio connection
-    uhd::transport::muxed_zero_copy_if::sptr _ctrl_dma_xport;
-    //! Control transport for one liberio connection
-    uhd::transport::muxed_zero_copy_if::sptr _async_msg_dma_xport;
-
-    uhd::dict<std::string, std::string> recv_args;
-    uhd::dict<std::string, std::string> send_args;
-
     //! Stores the args with which the device was originally initialized
     uhd::device_addr_t _device_args;
     //! Stores a list of mboard references
@@ -237,9 +220,12 @@ class mpmd_impl : public uhd::usrp::device3_impl
     // No-one touches this except allocate_xbar_local_addr(), gotcha?
     size_t  _xbar_local_addr_ctr = 2;
 
+    // TODO make sure this can't wrap
     size_t _sid_framer;
 };
 
+}} /* namespace uhd::mpmd */
+
 uhd::device_addrs_t mpmd_find(const uhd::device_addr_t& hint_);
 
 #endif /* INCLUDED_MPMD_IMPL_HPP */
diff --git a/host/lib/usrp/mpmd/mpmd_mboard_impl.cpp b/host/lib/usrp/mpmd/mpmd_mboard_impl.cpp
index 337504927..1038be26d 100644
--- a/host/lib/usrp/mpmd/mpmd_mboard_impl.cpp
+++ b/host/lib/usrp/mpmd/mpmd_mboard_impl.cpp
@@ -1,18 +1,7 @@
 //
-// Copyright 2017 Ettus Research (National Instruments)
+// Copyright 2017 Ettus Research, a National Instruments Company
 //
-// This program is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// This program 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 General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+// SPDX-License-Identifier: GPL-3.0
 //
 
 #include "mpmd_impl.hpp"
@@ -67,6 +56,7 @@ namespace {
 }
 
 using namespace uhd;
+using namespace uhd::mpmd;
 
 /*****************************************************************************
  * Structors
@@ -77,8 +67,9 @@ mpmd_mboard_impl::mpmd_mboard_impl(
 ) : mb_args(mb_args_)
   , rpc(uhd::rpc_client::make(
               rpc_server_addr,
-              MPM_RPC_PORT,
-              MPM_RPC_GET_LAST_ERROR_CMD))
+              mpmd_impl::MPM_RPC_PORT,
+              mpmd_impl::MPM_RPC_GET_LAST_ERROR_CMD))
+  , _xport_mgr(xport::mpmd_xport_mgr::make(mb_args))
 {
     UHD_LOGGER_TRACE("MPMD")
         << "Initializing mboard, connecting to RPC server address: "
@@ -96,7 +87,6 @@ mpmd_mboard_impl::mpmd_mboard_impl(
     init_device(rpc, mb_args);
     // RFNoC block clocks are now on. Noc-IDs can be read back.
 
-
     auto device_info_dict = rpc->request<dev_info>("get_device_info");
     for (const auto &info_pair : device_info_dict) {
         device_info[info_pair.first] = info_pair.second;
@@ -120,24 +110,6 @@ mpmd_mboard_impl::mpmd_mboard_impl(
     this->num_xbars = rpc->request<size_t>("get_num_xbars");
     // xbar_local_addrs is not yet valid after this!
     this->xbar_local_addrs.resize(this->num_xbars, 0xFF);
-
-    // std::vector<std::string> data_ifaces =
-    //     rpc.call<std::vector<std::string>>("get_interfaces", rpc_token);
-
-    // discover path to device and tell MPM our MAC address seen at the data
-    // interfaces
-    // move this into make_transport
-    //for (const auto& iface : data_ifaces) {
-        //std::vector<std::string> addrs = rpc.call<std::vector<std::string>>(
-            //"get_interface_addrs", _rpc_token, iface);
-        //for (const auto& iface_addr : addrs) {
-            //if (rpc_client(iface_addr, MPM_RPC_PORT)
-                    //.call<bool>("probe_interface", _rpc_token)) {
-                //data_interfaces.emplace(iface, iface_addr);
-                //break;
-            //}
-        //}
-    //}
 }
 
 mpmd_mboard_impl::~mpmd_mboard_impl()
@@ -152,20 +124,6 @@ mpmd_mboard_impl::~mpmd_mboard_impl()
 /*****************************************************************************
  * API
  ****************************************************************************/
-uhd::sid_t mpmd_mboard_impl::allocate_sid(
-        const uint16_t port,
-        const uhd::sid_t address,
-        const uint32_t xbar_src_addr,
-        const uint32_t xbar_src_port,
-        const uint32_t dst_addr
-) {
-    const auto sid = rpc->request_with_token<uint32_t>(
-        "allocate_sid",
-        port, address.get(), xbar_src_addr, xbar_src_port, dst_addr
-    );
-    return uhd::sid_t(sid);
-}
-
 void mpmd_mboard_impl::set_xbar_local_addr(
         const size_t xbar_index,
         const size_t local_addr
@@ -175,6 +133,82 @@ void mpmd_mboard_impl::set_xbar_local_addr(
     xbar_local_addrs.at(xbar_index) = local_addr;
 }
 
+uhd::both_xports_t mpmd_mboard_impl::make_transport(
+        const sid_t& sid,
+        usrp::device3_impl::xport_type_t xport_type,
+        const uhd::device_addr_t& xport_args
+) {
+    const std::string xport_type_str = [xport_type](){
+        switch (xport_type) {
+        case mpmd_impl::CTRL:
+            return "CTRL";
+        case mpmd_impl::ASYNC_MSG:
+            return "ASYNC_MSG";
+        case mpmd_impl::RX_DATA:
+            return "RX_DATA";
+        case mpmd_impl::TX_DATA:
+            return "TX_DATA";
+        default:
+            UHD_THROW_INVALID_CODE_PATH();
+        };
+    }();
+
+    UHD_LOGGER_TRACE("MPMD")
+        << __func__ << "(): Creating new transport of type: "
+        << xport_type_str
+    ;
+
+    using namespace uhd::mpmd::xport;
+    const auto xport_info_list =
+        rpc->request_with_token<mpmd_xport_mgr::xport_info_list_t>(
+            "request_xport",
+            sid.get_dst(),
+            sid.get_src(),
+            xport_type_str
+    );
+    UHD_LOGGER_TRACE("MPMD")
+        << __func__
+        << "(): request_xport() gave us " << xport_info_list.size()
+        << " option(s)."
+    ;
+    if (xport_info_list.empty()) {
+        UHD_LOG_ERROR("MPMD", "No viable transport path found!");
+        throw uhd::runtime_error("No viable transport path found!");
+    }
+
+    xport::mpmd_xport_mgr::xport_info_t xport_info_out;
+    auto xports = _xport_mgr->make_transport(
+        xport_info_list,
+        xport_type,
+        xport_args,
+        xport_info_out
+    );
+
+    if (not rpc->request_with_token<bool>(
+                "commit_xport",
+                xport_info_out)) {
+        UHD_LOG_ERROR("MPMD", "Failed to create UDP transport!");
+        throw uhd::runtime_error("commit_xport() failed!");
+    }
+
+    return xports;
+}
+
+uhd::device_addr_t mpmd_mboard_impl::get_rx_hints() const
+{
+    // TODO: See if we need to do anything here. get_rx_stream() might care.
+    device_addr_t rx_hints;
+    return rx_hints;
+}
+
+uhd::device_addr_t mpmd_mboard_impl::get_tx_hints() const
+{
+    // TODO: See if we need to do anything here. get_tx_stream() might care.
+    device_addr_t tx_hints;
+    return tx_hints;
+}
+
+
 /*****************************************************************************
  * Private methods
  ****************************************************************************/
diff --git a/host/lib/usrp/mpmd/mpmd_xport.cpp b/host/lib/usrp/mpmd/mpmd_xport.cpp
index 5dd29a6f7..c21da3839 100644
--- a/host/lib/usrp/mpmd/mpmd_xport.cpp
+++ b/host/lib/usrp/mpmd/mpmd_xport.cpp
@@ -4,57 +4,39 @@
 // SPDX-License-Identifier: GPL-3.0
 //
 
-// make_transport logic for mpmd_impl.
-
+// make_transport logic for mpmd_impl. Note that mpmd_xport_mgr.* has most of
+// the actual transport logic, this for transport-related APIs.
 
 #include "mpmd_impl.hpp"
-#include "../transport/liberio_zero_copy.hpp"
-#include <uhd/transport/udp_zero_copy.hpp>
-#include <uhd/utils/byteswap.hpp>
+#include "mpmd_xport_mgr.hpp"
 
 using namespace uhd;
+using namespace uhd::mpmd;
 
-
-// TODO this does not consider the liberio use case!
-uhd::device_addr_t mpmd_impl::get_rx_hints(size_t /* mb_index */)
+uhd::device_addr_t mpmd_impl::get_rx_hints(size_t mb_index)
 {
-    //device_addr_t rx_hints = _mb[mb_index].recv_args;
-    device_addr_t rx_hints; // TODO don't ignore what the user tells us
-    // (default to a large recv buff)
-    if (not rx_hints.has_key("recv_buff_size"))
-    {
-        //For the ethernet transport, the buffer has to be set before creating
-        //the transport because it is independent of the frame size and # frames
-        //For nirio, the buffer size is not configurable by the user
-        #if defined(UHD_PLATFORM_MACOS) || defined(UHD_PLATFORM_BSD)
-            //limit buffer resize on macos or it will error
-            rx_hints["recv_buff_size"] = boost::lexical_cast<std::string>(MPMD_RX_SW_BUFF_SIZE_ETH_MACOS);
-        #elif defined(UHD_PLATFORM_LINUX) || defined(UHD_PLATFORM_WIN32)
-            //set to half-a-second of buffering at max rate
-            rx_hints["recv_buff_size"] = boost::lexical_cast<std::string>(MPMD_RX_SW_BUFF_SIZE_ETH);
-        #endif
-    }
-    return rx_hints;
+    return _mb.at(mb_index)->get_rx_hints();
 }
 
+uhd::device_addr_t mpmd_impl::get_tx_hints(size_t mb_index)
+{
+    return _mb.at(mb_index)->get_tx_hints();
+}
 
-/******************************************************************************
- * General make_transport() + helpers
- *****************************************************************************/
-size_t mpmd_impl::identify_mboard_by_sid(const size_t remote_addr)
+size_t mpmd_impl::identify_mboard_by_xbar_addr(const size_t xbar_addr) const
 {
     for (size_t mb_index = 0; mb_index < _mb.size(); mb_index++) {
         for (size_t xbar_index = 0;
                 xbar_index < _mb[mb_index]->num_xbars;
                 xbar_index++) {
-            if (_mb[mb_index]->get_xbar_local_addr(xbar_index) == remote_addr) {
+            if (_mb.at(mb_index)->get_xbar_local_addr(xbar_index) == xbar_addr) {
                 return mb_index;
             }
         }
     }
     throw uhd::lookup_error(str(
-        boost::format("Cannot identify mboard for remote address %d")
-        % remote_addr
+        boost::format("Cannot identify mboard for crossbar address %d")
+        % xbar_addr
     ));
 }
 
@@ -63,59 +45,27 @@ both_xports_t mpmd_impl::make_transport(
         usrp::device3_impl::xport_type_t xport_type,
         const uhd::device_addr_t& args
 ) {
-    const size_t mb_index = identify_mboard_by_sid(dst_address.get_dst_addr());
-    // Could also be a map...
-    const std::string xport_type_str = [xport_type](){
-        switch (xport_type) {
-        case CTRL:
-            return "CTRL";
-        case ASYNC_MSG:
-            return "ASYNC_MSG";
-        case RX_DATA:
-            return "RX_DATA";
-        case TX_DATA:
-            return "TX_DATA";
-        default:
-            UHD_THROW_INVALID_CODE_PATH();
-        };
-    }();
-
+    const size_t mb_index =
+        identify_mboard_by_xbar_addr(dst_address.get_dst_addr());
+
+    const sid_t sid(
+        0,
+        _sid_framer++, // FIXME make sure we only increment if actually valid
+        dst_address.get_dst_addr(),
+        dst_address.get_dst_endpoint()
+    );
     UHD_LOGGER_TRACE("MPMD")
-        << "Creating new transport of type: " << xport_type_str
-        << " To mboard: " << mb_index
-        << " Destination address: " << dst_address.to_pp_string_hex().substr(6)
+        << "Creating new transport to mboard: " << mb_index
+        << " SID: " << sid.to_pp_string_hex()
         << " User-defined xport args: " << args.to_string()
     ;
 
-    const auto xport_info_list =
-        _mb[mb_index]->rpc->request_with_token<xport_info_list_t>(
-            "request_xport",
-            dst_address.get_dst(),
-            _sid_framer++, // FIXME make sure we only increment if actually valid
-            xport_type_str
+    both_xports_t xports = _mb[mb_index]->make_transport(
+        sid,
+        xport_type,
+        args
     );
     UHD_LOGGER_TRACE("MPMD")
-        << "request_xport() gave us " << xport_info_list.size()
-        << " option(s)."
-    ;
-
-    // This is not very elegant, and needs some kind of factory model or
-    // whatnot.
-    auto xport_info = xport_info_list.at(0); // In the future, actually pick one
-                                           // sensibly. This is what would
-                                           // enable dual Eth support. FIXME
-    both_xports_t xports;
-    if (xport_info["type"] == "UDP") {
-        xports = make_transport_udp(mb_index, xport_info, xport_type, args);
-#ifdef HAVE_LIBERIO
-    } else if (xport_info["type"] == "liberio") {
-        xports = make_transport_liberio(mb_index, xport_info, xport_type, args);
-#endif
-    } else {
-        UHD_THROW_INVALID_CODE_PATH();
-    }
-
-    UHD_LOGGER_TRACE("MPMD")
         << "xport info: send_sid==" << xports.send_sid.to_pp_string_hex()
         << " recv_sid==" << xports.recv_sid.to_pp_string_hex()
         << " endianness=="
@@ -123,181 +73,6 @@ both_xports_t mpmd_impl::make_transport(
         << " recv_buff_size==" << xports.recv_buff_size
         << " send_buff_size==" << xports.send_buff_size
     ;
-
-    return xports;
-}
-
-
-/******************************************************************************
- * UDP Transport
- *****************************************************************************/
-both_xports_t mpmd_impl::make_transport_udp(
-        const size_t mb_index,
-        xport_info_t &xport_info,
-        const xport_type_t /*xport_type*/,
-        const uhd::device_addr_t& xport_args
-) {
-    auto &rpc = _mb[mb_index]->rpc;
-
-    transport::zero_copy_xport_params default_buff_args;
-    // Create actual UDP transport
-    // TODO don't hardcode these
-    default_buff_args.send_frame_size = 8000;
-    default_buff_args.recv_frame_size = 8000;
-    default_buff_args.num_recv_frames = 32;
-    default_buff_args.num_send_frames = 32;
-
-    transport::udp_zero_copy::buff_params buff_params;
-    auto recv = transport::udp_zero_copy::make(
-        xport_info["ipv4"],
-        xport_info["port"],
-        default_buff_args,
-        buff_params,
-        xport_args
-    );
-    const uint16_t port = recv->get_local_port();
-    const std::string src_ip_addr = recv->get_local_addr();
-    xport_info["src_port"] = std::to_string(port);
-    xport_info["src_ipv4"] = src_ip_addr;
-
-    // Communicate it all back to MPM
-    if (not rpc->request_with_token<bool>("commit_xport", xport_info)) {
-        UHD_LOG_ERROR("MPMD", "Failed to create UDP transport!");
-        throw uhd::runtime_error("commit_xport() failed!");
-    }
-
-    // Create both_xports_t object and finish:
-    both_xports_t xports;
-    xports.endianness = uhd::ENDIANNESS_BIG;
-    xports.send_sid = sid_t(xport_info["send_sid"]);
-    xports.recv_sid = xports.send_sid.reversed();
-    xports.recv_buff_size = buff_params.recv_buff_size;
-    xports.send_buff_size = buff_params.send_buff_size;
-    xports.recv = recv; // Note: This is a type cast!
-    xports.send = recv; // This too
-    return xports;
-}
-
-/******************************************************************************
- * Liberio Transport
- *****************************************************************************/
-#ifdef HAVE_LIBERIO
-static uint32_t extract_sid_from_pkt(void* pkt, size_t) {
-    return uhd::sid_t(uhd::wtohx(static_cast<const uint32_t*>(pkt)[1]))
-        .get_dst();
-}
-
-uhd::transport::muxed_zero_copy_if::sptr mpmd_impl::make_muxed_liberio_xport(
-        const std::string &tx_dev,
-        const std::string &rx_dev,
-        const uhd::transport::zero_copy_xport_params &buff_args,
-        const size_t max_muxed_ports
-) {
-    auto base_xport = transport::liberio_zero_copy::make(
-            tx_dev, rx_dev, buff_args);
-
-    return uhd::transport::muxed_zero_copy_if::make(
-            base_xport, extract_sid_from_pkt, max_muxed_ports);
-}
-
-both_xports_t mpmd_impl::make_transport_liberio(
-        const size_t mb_index,
-        xport_info_t &xport_info,
-        const xport_type_t xport_type,
-        const uhd::device_addr_t& xport_args
-) {
-    auto &rpc = _mb[mb_index]->rpc;
-
-    transport::zero_copy_xport_params default_buff_args;
-    /* default ones for RX / TX, override below */
-    default_buff_args.send_frame_size = 4 * getpagesize();
-    default_buff_args.recv_frame_size = 4 * getpagesize();
-    default_buff_args.num_recv_frames = 128;
-    default_buff_args.num_send_frames = 128;
-
-    if (xport_type == CTRL) {
-      default_buff_args.send_frame_size = 128;
-      default_buff_args.recv_frame_size = 128;
-    } else if (xport_type == ASYNC_MSG) {
-      default_buff_args.send_frame_size = 256;
-      default_buff_args.recv_frame_size = 256;
-    } else if (xport_type == RX_DATA) {
-      default_buff_args.send_frame_size = 64;
-    } else {
-      default_buff_args.recv_frame_size = 64;
-    }
-
-    const std::string tx_dev = xport_info["tx_dev"];
-    const std::string rx_dev = xport_info["rx_dev"];
-
-    both_xports_t xports;
-    xports.endianness = uhd::ENDIANNESS_LITTLE;
-    xports.send_sid = sid_t(xport_info["send_sid"]);
-    xports.recv_sid = xports.send_sid.reversed();
-
-    // this is kinda ghetto: scale buffer for muxed xports since we share the
-    // buffer...
-    float divisor = 1;
-    if (xport_type == CTRL)
-      divisor = 16;
-    else if (xport_type == ASYNC_MSG)
-      divisor = 4;
-
-
-    //if (xport_info["muxed"] == "True") {
-    //// FIXME tbw
-    //}
-    if (xport_type == CTRL) {
-        UHD_ASSERT_THROW(xport_info["muxed"] == "True");
-        if (not _ctrl_dma_xport) {
-            default_buff_args.send_frame_size = 128;
-            default_buff_args.recv_frame_size = 128;
-            _ctrl_dma_xport = make_muxed_liberio_xport(tx_dev, rx_dev,
-                    default_buff_args, int(divisor));
-        }
-
-        UHD_LOGGER_TRACE("MPMD")
-            << "Making (muxed) stream with num " << xports.recv_sid.get_dst();
-        xports.recv = _ctrl_dma_xport->make_stream(xports.recv_sid.get_dst());
-    } else if (xport_type == ASYNC_MSG) {
-        UHD_ASSERT_THROW(xport_info["muxed"] == "True");
-        if (not _async_msg_dma_xport) {
-            default_buff_args.send_frame_size = 256;
-            default_buff_args.recv_frame_size = 256;
-            _async_msg_dma_xport = make_muxed_liberio_xport(
-                    tx_dev, rx_dev, default_buff_args, int(divisor));
-        }
-
-        UHD_LOGGER_TRACE("MPMD")
-            << "making (muxed) stream with num " << xports.recv_sid.get_dst();
-        xports.recv =
-            _async_msg_dma_xport->make_stream(xports.recv_sid.get_dst());
-    } else {
-        xports.recv =
-            transport::liberio_zero_copy::make(
-                    tx_dev, rx_dev, default_buff_args);
-    }
-
-    transport::udp_zero_copy::buff_params buff_params;
-    buff_params.recv_buff_size =
-        float(default_buff_args.recv_frame_size) *
-        float(default_buff_args.num_recv_frames) / divisor;
-    buff_params.send_buff_size =
-        float(default_buff_args.send_frame_size) *
-        float(default_buff_args.num_send_frames) / divisor;
-
-
-    // Communicate it all back to MPM
-    if (not rpc->request_with_token<bool>("commit_xport", xport_info)) {
-        UHD_LOG_ERROR("MPMD", "Failed to create UDP transport!");
-        throw uhd::runtime_error("commit_xport() failed!");
-    }
-
-    // Finish both_xports_t object and return:
-    xports.recv_buff_size = buff_params.recv_buff_size;
-    xports.send_buff_size = buff_params.send_buff_size;
-    xports.send = xports.recv;
     return xports;
 }
 
-#endif /* HAVE_LIBERIO */
diff --git a/host/lib/usrp/mpmd/mpmd_xport_ctrl_base.hpp b/host/lib/usrp/mpmd/mpmd_xport_ctrl_base.hpp
new file mode 100644
index 000000000..e5a3b7e31
--- /dev/null
+++ b/host/lib/usrp/mpmd/mpmd_xport_ctrl_base.hpp
@@ -0,0 +1,45 @@
+//
+// Copyright 2017 Ettus Research, a National Instruments Company
+//
+// SPDX-License-Identifier: GPL-3.0
+//
+
+#ifndef INCLUDED_MPMD_XPORT_CTRL_BASE_HPP
+#define INCLUDED_MPMD_XPORT_CTRL_BASE_HPP
+
+#include "mpmd_xport_mgr.hpp"
+#include "../device3/device3_impl.hpp"
+#include <uhd/types/device_addr.hpp>
+#include <memory>
+
+namespace uhd { namespace mpmd { namespace xport {
+
+/*! Transport manager implementation base
+ */
+class mpmd_xport_ctrl_base
+{
+public:
+    using uptr = std::unique_ptr<mpmd_xport_ctrl_base>;
+
+    /*! This is the final step of a make_transport() sequence
+     *
+     * \param xport_info Contains all necessary transport info. The
+     *                   implementation may update this!
+     * \param xport_type CTRL, ASYNC_MSG, ... (see xport_type_t)
+     * \param xport_args Additional arguments. These can come from the user.
+     */
+    virtual both_xports_t make_transport(
+        mpmd_xport_mgr::xport_info_t& xport_info,
+        const usrp::device3_impl::xport_type_t xport_type,
+        const uhd::device_addr_t& xport_args
+    ) = 0;
+
+    //! Assert if an xport_info is even valid/feasible/available
+    virtual bool is_valid(
+        const mpmd_xport_mgr::xport_info_t& xport_info
+    ) const = 0;
+};
+
+}}} /* namespace uhd::mpmd::xport */
+
+#endif /* INCLUDED_MPMD_XPORT_CTRL_BASE_HPP */
diff --git a/host/lib/usrp/mpmd/mpmd_xport_ctrl_liberio.cpp b/host/lib/usrp/mpmd/mpmd_xport_ctrl_liberio.cpp
new file mode 100644
index 000000000..2e4f024b4
--- /dev/null
+++ b/host/lib/usrp/mpmd/mpmd_xport_ctrl_liberio.cpp
@@ -0,0 +1,145 @@
+//
+// Copyright 2017 Ettus Research, National Instruments Company
+//
+// SPDX-License-Identifier: GPL-3.0
+//
+
+#include "mpmd_xport_ctrl_liberio.hpp"
+#include "../transport/liberio_zero_copy.hpp"
+#include <uhd/transport/udp_zero_copy.hpp>
+#include <uhd/utils/byteswap.hpp>
+
+using namespace uhd;
+using namespace uhd::mpmd::xport;
+
+namespace {
+
+    uint32_t extract_sid_from_pkt(void* pkt, size_t) {
+        return uhd::sid_t(uhd::wtohx(static_cast<const uint32_t*>(pkt)[1]))
+            .get_dst();
+    }
+
+}
+
+mpmd_xport_ctrl_liberio::mpmd_xport_ctrl_liberio(
+        const uhd::device_addr_t& mb_args
+) : _mb_args(mb_args)
+  , _recv_args(filter_args(mb_args, "recv"))
+  , _send_args(filter_args(mb_args, "send"))
+{
+    // nop
+}
+
+
+uhd::both_xports_t
+mpmd_xport_ctrl_liberio::make_transport(
+        mpmd_xport_mgr::xport_info_t &xport_info,
+        const usrp::device3_impl::xport_type_t xport_type,
+        const uhd::device_addr_t& /*xport_args_*/
+) {
+    transport::zero_copy_xport_params default_buff_args;
+    /* default ones for RX / TX, override below */
+    default_buff_args.send_frame_size = 4 * getpagesize();
+    default_buff_args.recv_frame_size = 4 * getpagesize();
+    default_buff_args.num_recv_frames = 128;
+    default_buff_args.num_send_frames = 128;
+
+    if (xport_type == usrp::device3_impl::CTRL) {
+      default_buff_args.send_frame_size = 128;
+      default_buff_args.recv_frame_size = 128;
+    } else if (xport_type == usrp::device3_impl::ASYNC_MSG) {
+      default_buff_args.send_frame_size = 256;
+      default_buff_args.recv_frame_size = 256;
+    } else if (xport_type == usrp::device3_impl::RX_DATA) {
+      default_buff_args.send_frame_size = 64;
+    } else {
+      default_buff_args.recv_frame_size = 64;
+    }
+
+    const std::string tx_dev = xport_info["tx_dev"];
+    const std::string rx_dev = xport_info["rx_dev"];
+
+    both_xports_t xports;
+    xports.endianness = uhd::ENDIANNESS_LITTLE;
+    xports.send_sid = sid_t(xport_info["send_sid"]);
+    xports.recv_sid = xports.send_sid.reversed();
+
+    // this is kinda ghetto: scale buffer for muxed xports since we share the
+    // buffer...
+    float divisor = 1;
+    if (xport_type == usrp::device3_impl::CTRL)
+      divisor = 16;
+    else if (xport_type == usrp::device3_impl::ASYNC_MSG)
+      divisor = 4;
+
+
+    //if (xport_info["muxed"] == "True") {
+    //// FIXME tbw
+    //}
+    if (xport_type == usrp::device3_impl::CTRL) {
+        UHD_ASSERT_THROW(xport_info["muxed"] == "True");
+        if (not _ctrl_dma_xport) {
+            default_buff_args.send_frame_size = 128;
+            default_buff_args.recv_frame_size = 128;
+            _ctrl_dma_xport = make_muxed_liberio_xport(tx_dev, rx_dev,
+                    default_buff_args, int(divisor));
+        }
+
+        UHD_LOGGER_TRACE("MPMD")
+            << "Making (muxed) stream with num " << xports.recv_sid.get_dst();
+        xports.recv = _ctrl_dma_xport->make_stream(xports.recv_sid.get_dst());
+    } else if (xport_type == usrp::device3_impl::ASYNC_MSG) {
+        UHD_ASSERT_THROW(xport_info["muxed"] == "True");
+        if (not _async_msg_dma_xport) {
+            default_buff_args.send_frame_size = 256;
+            default_buff_args.recv_frame_size = 256;
+            _async_msg_dma_xport = make_muxed_liberio_xport(
+                    tx_dev, rx_dev, default_buff_args, int(divisor));
+        }
+
+        UHD_LOGGER_TRACE("MPMD")
+            << "making (muxed) stream with num " << xports.recv_sid.get_dst();
+        xports.recv =
+            _async_msg_dma_xport->make_stream(xports.recv_sid.get_dst());
+    } else {
+        xports.recv =
+            transport::liberio_zero_copy::make(
+                    tx_dev, rx_dev, default_buff_args);
+    }
+
+    transport::udp_zero_copy::buff_params buff_params;
+    buff_params.recv_buff_size =
+        float(default_buff_args.recv_frame_size) *
+        float(default_buff_args.num_recv_frames) / divisor;
+    buff_params.send_buff_size =
+        float(default_buff_args.send_frame_size) *
+        float(default_buff_args.num_send_frames) / divisor;
+
+
+    // Finish both_xports_t object and return:
+    xports.recv_buff_size = buff_params.recv_buff_size;
+    xports.send_buff_size = buff_params.send_buff_size;
+    xports.send = xports.recv;
+    return xports;
+}
+
+bool mpmd_xport_ctrl_liberio::is_valid(
+    const mpmd_xport_mgr::xport_info_t& xport_info
+) const {
+    return xport_info.at("type") == "liberio";
+}
+
+uhd::transport::muxed_zero_copy_if::sptr
+mpmd_xport_ctrl_liberio::make_muxed_liberio_xport(
+        const std::string &tx_dev,
+        const std::string &rx_dev,
+        const uhd::transport::zero_copy_xport_params &buff_args,
+        const size_t max_muxed_ports
+) {
+    auto base_xport = transport::liberio_zero_copy::make(
+            tx_dev, rx_dev, buff_args);
+
+    return uhd::transport::muxed_zero_copy_if::make(
+            base_xport, extract_sid_from_pkt, max_muxed_ports);
+}
+
diff --git a/host/lib/usrp/mpmd/mpmd_xport_ctrl_liberio.hpp b/host/lib/usrp/mpmd/mpmd_xport_ctrl_liberio.hpp
new file mode 100644
index 000000000..76bb88f03
--- /dev/null
+++ b/host/lib/usrp/mpmd/mpmd_xport_ctrl_liberio.hpp
@@ -0,0 +1,59 @@
+//
+// Copyright 2017 Ettus Research, a National Instruments Company
+//
+// SPDX-License-Identifier: GPL-3.0
+//
+
+#ifndef INCLUDED_MPMD_XPORT_ctrl_liberio_HPP
+#define INCLUDED_MPMD_XPORT_ctrl_liberio_HPP
+
+#include "mpmd_xport_ctrl_base.hpp"
+#include <uhd/types/device_addr.hpp>
+#include "../device3/device3_impl.hpp"
+#include <uhd/transport/muxed_zero_copy_if.hpp>
+
+namespace uhd { namespace mpmd { namespace xport {
+
+/*! Liberio transport manager
+ */
+class mpmd_xport_ctrl_liberio : public mpmd_xport_ctrl_base
+{
+public:
+    mpmd_xport_ctrl_liberio(
+        const uhd::device_addr_t& mb_args
+    );
+
+    /*! Open DMA interface to kernel (and thus to FPGA DMA engine)
+     */
+    both_xports_t make_transport(
+        mpmd_xport_mgr::xport_info_t& xport_info,
+        const usrp::device3_impl::xport_type_t xport_type,
+        const uhd::device_addr_t& xport_args
+    );
+
+    bool is_valid(
+        const mpmd_xport_mgr::xport_info_t& xport_info
+    ) const;
+
+private:
+    /*! Create a muxed liberio transport for control packets */
+    uhd::transport::muxed_zero_copy_if::sptr make_muxed_liberio_xport(
+            const std::string &tx_dev,
+            const std::string &rx_dev,
+            const uhd::transport::zero_copy_xport_params &buff_args,
+            const size_t max_muxed_ports
+    );
+
+    const uhd::device_addr_t _mb_args;
+    const uhd::dict<std::string, std::string> _recv_args;
+    const uhd::dict<std::string, std::string> _send_args;
+
+    //! Control transport for one liberio connection
+    uhd::transport::muxed_zero_copy_if::sptr _ctrl_dma_xport;
+    //! Control transport for one liberio connection
+    uhd::transport::muxed_zero_copy_if::sptr _async_msg_dma_xport;
+};
+
+}}} /* namespace uhd::mpmd::xport */
+
+#endif /* INCLUDED_MPMD_XPORT_ctrl_liberio_HPP */
diff --git a/host/lib/usrp/mpmd/mpmd_xport_ctrl_udp.cpp b/host/lib/usrp/mpmd/mpmd_xport_ctrl_udp.cpp
new file mode 100644
index 000000000..de4b3bbba
--- /dev/null
+++ b/host/lib/usrp/mpmd/mpmd_xport_ctrl_udp.cpp
@@ -0,0 +1,103 @@
+//
+// Copyright 2017 Ettus Research, National Instruments Company
+//
+// SPDX-License-Identifier: GPL-3.0
+//
+
+#include "mpmd_xport_mgr.hpp"
+#include "mpmd_xport_ctrl_udp.hpp"
+#include <uhd/transport/udp_zero_copy.hpp>
+
+using namespace uhd;
+using namespace uhd::mpmd::xport;
+
+namespace {
+
+    #if defined(UHD_PLATFORM_MACOS) || defined(UHD_PLATFORM_BSD)
+    const size_t MPMD_RX_SW_BUFF_SIZE_ETH        = 0x100000; // 1Mib
+    #elif defined(UHD_PLATFORM_LINUX) || defined(UHD_PLATFORM_WIN32)
+    //For an ~8k frame size any size >32MiB is just wasted buffer space:
+    const size_t MPMD_RX_SW_BUFF_SIZE_ETH        = 0x2000000; // 32 MiB
+    #endif
+
+    const size_t MPMD_10GE_DATA_FRAME_MAX_SIZE = 8000; // CHDR packet size in bytes
+
+    std::vector<std::string> get_addrs_from_mb_args(
+        const uhd::device_addr_t& mb_args
+    ) {
+        // mb_args must always include addr
+        std::vector<std::string> addrs{mb_args["addr"]};
+        if (mb_args.has_key("second_addr")){
+            addrs.push_back(mb_args["second_addr"]);
+        }
+        return addrs;
+    }
+}
+
+
+mpmd_xport_ctrl_udp::mpmd_xport_ctrl_udp(
+        const uhd::device_addr_t& mb_args
+) : _mb_args(mb_args)
+  , _recv_args(filter_args(mb_args, "recv"))
+  , _send_args(filter_args(mb_args, "send"))
+  , _available_addrs(get_addrs_from_mb_args(mb_args))
+{
+}
+
+uhd::both_xports_t
+mpmd_xport_ctrl_udp::make_transport(
+        mpmd_xport_mgr::xport_info_t &xport_info,
+        const usrp::device3_impl::xport_type_t xport_type,
+        const uhd::device_addr_t& xport_args_
+) {
+    auto xport_args = xport_args_;
+
+    if (xport_type == usrp::device3_impl::RX_DATA
+            and not xport_args.has_key("recv_buff_size")) {
+        xport_args["recv_buff_size"] =
+            std::to_string(MPMD_RX_SW_BUFF_SIZE_ETH);
+    }
+
+    transport::zero_copy_xport_params default_buff_args;
+    // Create actual UDP transport
+    // TODO don't hardcode these
+    default_buff_args.send_frame_size = 8000;
+    default_buff_args.recv_frame_size = 8000;
+    default_buff_args.num_recv_frames = 32;
+    default_buff_args.num_send_frames = 32;
+
+    transport::udp_zero_copy::buff_params buff_params;
+    auto recv = transport::udp_zero_copy::make(
+        xport_info["ipv4"],
+        xport_info["port"],
+        default_buff_args,
+        buff_params,
+        xport_args
+    );
+    const uint16_t port = recv->get_local_port();
+    const std::string src_ip_addr = recv->get_local_addr();
+    xport_info["src_port"] = std::to_string(port);
+    xport_info["src_ipv4"] = src_ip_addr;
+
+    // Create both_xports_t object and finish:
+    both_xports_t xports;
+    xports.endianness = uhd::ENDIANNESS_BIG;
+    xports.send_sid = sid_t(xport_info["send_sid"]);
+    xports.recv_sid = xports.send_sid.reversed();
+    xports.recv_buff_size = buff_params.recv_buff_size;
+    xports.send_buff_size = buff_params.send_buff_size;
+    xports.recv = recv; // Note: This is a type cast!
+    xports.send = recv; // This too
+    return xports;
+}
+
+bool mpmd_xport_ctrl_udp::is_valid(
+    const mpmd_xport_mgr::xport_info_t& xport_info
+) const {
+    return std::find(
+        _available_addrs.cbegin(),
+        _available_addrs.cend(),
+        xport_info.at("ipv4")
+    ) != _available_addrs.cend();
+}
+
diff --git a/host/lib/usrp/mpmd/mpmd_xport_ctrl_udp.hpp b/host/lib/usrp/mpmd/mpmd_xport_ctrl_udp.hpp
new file mode 100644
index 000000000..0c8c19479
--- /dev/null
+++ b/host/lib/usrp/mpmd/mpmd_xport_ctrl_udp.hpp
@@ -0,0 +1,46 @@
+//
+// Copyright 2017 Ettus Research, a National Instruments Company
+//
+// SPDX-License-Identifier: GPL-3.0
+//
+
+#ifndef INCLUDED_MPMD_XPORT_ctrl_udp_HPP
+#define INCLUDED_MPMD_XPORT_ctrl_udp_HPP
+
+#include "mpmd_xport_ctrl_base.hpp"
+#include <uhd/types/device_addr.hpp>
+#include "../device3/device3_impl.hpp"
+
+namespace uhd { namespace mpmd { namespace xport {
+
+/*! UDP transport manager
+ *
+ * Opens UDP sockets
+ */
+class mpmd_xport_ctrl_udp : public mpmd_xport_ctrl_base
+{
+public:
+    mpmd_xport_ctrl_udp(
+        const uhd::device_addr_t& mb_args
+    );
+
+    both_xports_t make_transport(
+        mpmd_xport_mgr::xport_info_t& xport_info,
+        const usrp::device3_impl::xport_type_t xport_type,
+        const uhd::device_addr_t& xport_args
+    );
+
+    bool is_valid(
+        const mpmd_xport_mgr::xport_info_t& xport_info
+    ) const;
+
+private:
+    const uhd::device_addr_t _mb_args;
+    const uhd::dict<std::string, std::string> _recv_args;
+    const uhd::dict<std::string, std::string> _send_args;
+    const std::vector<std::string> _available_addrs;
+};
+
+}}} /* namespace uhd::mpmd::xport */
+
+#endif /* INCLUDED_MPMD_XPORT_ctrl_udp_HPP */
diff --git a/host/lib/usrp/mpmd/mpmd_xport_mgr.cpp b/host/lib/usrp/mpmd/mpmd_xport_mgr.cpp
new file mode 100644
index 000000000..242a46527
--- /dev/null
+++ b/host/lib/usrp/mpmd/mpmd_xport_mgr.cpp
@@ -0,0 +1,148 @@
+//
+// Copyright 2017 Ettus Research, National Instruments Company
+//
+// SPDX-License-Identifier: GPL-3.0
+//
+
+#include "mpmd_impl.hpp"
+#include "mpmd_xport_mgr.hpp"
+#include "mpmd_xport_ctrl_base.hpp"
+#include "mpmd_xport_ctrl_udp.hpp"
+#ifdef HAVE_LIBERIO
+#  include "mpmd_xport_ctrl_liberio.hpp"
+#endif
+
+uhd::dict<std::string, std::string> uhd::mpmd::xport::filter_args(
+    const uhd::device_addr_t& args,
+    const std::string& prefix
+) {
+    uhd::dict<std::string, std::string> filtered_args;
+    for (const std::string& key : args.keys()) {
+        if (key.find(prefix) != std::string::npos) {
+            filtered_args[key] = args[key];
+        }
+    }
+
+    return filtered_args;
+}
+
+using namespace uhd::mpmd::xport;
+
+class mpmd_xport_mgr_impl : public mpmd_xport_mgr
+{
+public:
+    mpmd_xport_mgr_impl(
+        const uhd::device_addr_t& mb_args
+    ) : _mb_args(mb_args)
+    {
+        // nop
+    }
+
+    /**************************************************************************
+     * API (see mpmd_xport_mgr.hpp)
+     *************************************************************************/
+    uhd::both_xports_t make_transport(
+        const xport_info_list_t &xport_info_list,
+        const uhd::usrp::device3_impl::xport_type_t xport_type,
+        const uhd::device_addr_t& xport_args,
+        xport_info_t& xport_info_out
+    ) {
+        for (const auto &xport_info : xport_info_list) {
+            require_xport_mgr(xport_info.at("type"));
+        }
+
+        // Run our incredibly smart selection algorithm
+        xport_info_out = select_xport_option(xport_info_list);
+        const std::string xport_medium = xport_info_out.at("type");
+        UHD_LOG_TRACE("MPMD",
+                __func__ << "(): xport medium is " << xport_medium);
+
+        // When we've picked our preferred option, pass it to the transport
+        // implementation for execution:
+        return _xport_ctrls[xport_medium]->make_transport(
+            xport_info_out,
+            xport_type,
+            xport_args
+       );
+    }
+
+
+private:
+    /**************************************************************************
+     * Private methods / helpers
+     *************************************************************************/
+    /*! Picks a transport option based on available data
+     *
+     * \param xport_info_list List of available options, they all need to be
+     *                        valid choices.
+     *
+     * \returns One element of \p xport_info_list based on a selection
+     *          algorithm.
+     */
+    xport_info_t select_xport_option(
+        const xport_info_list_t &xport_info_list
+    ) const {
+        // Naive xport picking method, this needs fixing (FIXME).
+        // Have algorithm run on baseline score, allocation, and random soup
+        return xport_info_list.at(0);
+    }
+
+    //! Create an instance of an xport manager implementation
+    //
+    // \param xport_medium "UDP" or "liberio"
+    // \param mb_args Device args
+    mpmd_xport_ctrl_base::uptr make_mgr_impl(
+        const std::string &xport_medium,
+        const uhd::device_addr_t& mb_args
+    ) const {
+        if (xport_medium == "UDP") {
+            return mpmd_xport_ctrl_base::uptr(
+                new mpmd_xport_ctrl_udp(mb_args)
+            );
+#ifdef HAVE_LIBERIO
+        } else if (xport_medium == "liberio") {
+            return mpmd_xport_ctrl_base::uptr(
+                new mpmd_xport_ctrl_liberio(mb_args)
+            );
+#endif
+        } else {
+            throw uhd::key_error("Unknown transport medium!");
+        }
+    }
+
+    //! This will make sure that _xport_ctrls contains a valid transport manager
+    // for \p xport_medium
+    //
+    // When this function returns, it will be possible to access
+    // this->_xport_ctrls[xport_medium].
+    //
+    // \param xport_medium Type of transport, e.g. "UDP", "liberio", ...
+    //
+    // \throws uhd::key_error if \p xport_medium is not known or registered
+    void require_xport_mgr(const std::string &xport_medium)
+    {
+        if (_xport_ctrls.count(xport_medium) == 0) {
+            UHD_LOG_TRACE("MPMD",
+                "Instantiating transport manager `" << xport_medium << "'");
+            _xport_ctrls[xport_medium] = make_mgr_impl(xport_medium, _mb_args);
+        }
+    }
+
+    /**************************************************************************
+     * Private attributes
+     *************************************************************************/
+    //! Cache available xport manager implementations
+    //
+    // Should only every be populated by require_xport_mgr()
+    std::map<std::string, mpmd_xport_ctrl_base::uptr> _xport_ctrls;
+
+    //! Motherboard args, can contain things like 'recv_buff_size'
+    const uhd::device_addr_t _mb_args;
+};
+
+mpmd_xport_mgr::uptr mpmd_xport_mgr::make(
+    const uhd::device_addr_t& mb_args
+) {
+    return mpmd_xport_mgr::uptr(new mpmd_xport_mgr_impl(mb_args));
+}
+
diff --git a/host/lib/usrp/mpmd/mpmd_xport_mgr.hpp b/host/lib/usrp/mpmd/mpmd_xport_mgr.hpp
new file mode 100644
index 000000000..2da4af323
--- /dev/null
+++ b/host/lib/usrp/mpmd/mpmd_xport_mgr.hpp
@@ -0,0 +1,95 @@
+//
+// Copyright 2017 Ettus Research, a National Instruments Company
+//
+// SPDX-License-Identifier: GPL-3.0
+//
+
+#ifndef INCLUDED_MPMD_XPORT_MGR_HPP
+#define INCLUDED_MPMD_XPORT_MGR_HPP
+
+#include "../device3/device3_impl.hpp"
+#include <uhd/types/dict.hpp>
+#include <memory>
+#include <map>
+#include <vector>
+#include <string>
+
+namespace uhd { namespace mpmd { namespace xport {
+
+/*! Return filtered subset from a device_addr_t
+ *
+ * The return dictionary will contain all key/value pairs from \p args
+ * where the key begins with \p prefix.
+ *
+ * \param args Bucket of key/value pairs
+ * \param prefix Key prefix to match against
+ */
+uhd::dict<std::string, std::string> filter_args(
+    const uhd::device_addr_t& args,
+    const std::string& prefix
+);
+
+/*! MPMD Transport Manager
+ *
+ * A transport manager is an object which sets up a physical connection to a
+ * CHDR device. Its implementation is specific to the underlying transport
+ * medium. For example, if the medium is Ethernet/UDP, this class will create
+ * sockets.
+ */
+class mpmd_xport_mgr
+{
+public:
+    using uptr = std::unique_ptr<mpmd_xport_mgr>;
+    using xport_info_t = std::map<std::string, std::string>;
+    using xport_info_list_t = std::vector<std::map<std::string, std::string>>;
+
+    /*! Return a reference to a transport manager
+     *
+     * \param mb_args Additional args from the motherboard. These may contain
+     *                transport-related args (e.g., "recv_buff_size") which
+     *                can be relevant to the underlying implementation.
+     *
+     * \returns Reference to manager object
+     * \throws uhd::key_error if \p xport_medium is not supported. The ctor of
+     *         the underlying class that is requested can also throw.
+     */
+    static uptr make(
+        const uhd::device_addr_t& mb_args
+    );
+
+    /*! Create a transports object
+     *
+     * Implementation details depend on the underlying implementation.
+     * In general, the implementations will follow the following recipe:
+     * 1. Pick a suitable element from \p xport_info_list
+     * 2. Do whatever system calls are necessary to create the physical
+     *    transport; to do so, call the underlying implementation (UDP or
+     *    whatever)
+     * 3. Update the selected element from xport_info_list
+     * 5. Return results
+     *
+     * \param xport_info_list List of possible options to choose from. Every
+     *                        element of this argument needs to have the same
+     *                        "type" key (e.g., they all need to be "UDP").
+     * \param xport_type Transport type (CTRL, RX_DATA, ...)
+     * \param xport_args Arbitrary additional transport args. These could come
+     *                   from the user, or other places.
+     * \param xport_info_out The updated dictionary from xport_info_list that
+     *                       was eventually chosen
+     *
+     * \returns The both_xports_t object containing the actual transport info,
+     *          and xport_info_out contains the updated transport option info.
+     *          The latter needs to get sent back to MPM to complete the
+     *          transport handshake.
+     */
+    virtual both_xports_t make_transport(
+        const xport_info_list_t &xport_info_list,
+        const usrp::device3_impl::xport_type_t xport_type,
+        const uhd::device_addr_t& xport_args,
+        xport_info_t& xport_info_out
+    ) = 0;
+};
+
+}}} /* namespace uhd::mpmd::xport */
+
+#endif /* INCLUDED_MPMD_XPORT_MGR_HPP */