Expanded the UDP api:

We can make simple udp transports for discovery and control.
We can support a udp zero copy transport (currently just asio).
Reworked the io_impl for usrp2 to work with the zero copy api.
So far, all of this untested other than compiling.
A cut-down vrt library is in the works to simplify the io impl.

7 files changed, 364 insertions, 237 deletions

diff --git a/host/lib/CMakeLists.txt b/host/lib/CMakeLists.txt
index 97f1ac52e..a52cd74a9 100644
--- a/host/lib/CMakeLists.txt
+++ b/host/lib/CMakeLists.txt
@@ -23,7 +23,7 @@ SET(libuhd_sources
     device_addr.cpp
     gain_handler.cpp
     wax.cpp
-    transport/udp.cpp
+    transport/udp_simple.cpp
     usrp/dboard/basic.cpp
     usrp/dboard_base.cpp
     usrp/dboard_id.cpp
@@ -38,6 +38,13 @@ SET(libuhd_sources
 )
 
 ########################################################################
+# Conditionally add the udp sources
+########################################################################
+LIST(APPEND libuhd_sources
+    transport/udp_zero_copy_none.cpp
+)
+
+########################################################################
 # Conditionally add the usrp1e sources
 ########################################################################
 LIST(APPEND libuhd_sources
diff --git a/host/lib/transport/udp.cpp b/host/lib/transport/udp.cpp
deleted file mode 100644
index 878f71410..000000000
--- a/host/lib/transport/udp.cpp
+++ /dev/null
@@ -1,98 +0,0 @@
-//
-// Copyright 2010 Ettus Research LLC
-//
-// 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/>.
-//
-
-#include <uhd/transport/udp.hpp>
-#include <boost/format.hpp>
-#include <iostream>
-
-/***********************************************************************
- * UDP implementation class
- **********************************************************************/
-class udp_impl : public uhd::transport::udp{
-public:
-    //structors
-    udp_impl(const std::string &addr, const std::string &port, bool bcast);
-    ~udp_impl(void);
-
-    //send/recv
-    size_t send(const std::vector<boost::asio::const_buffer> &buffs);
-    size_t send(const boost::asio::const_buffer &buff);
-    size_t recv(const std::vector<boost::asio::mutable_buffer> &buffs);
-    size_t recv(const boost::asio::mutable_buffer &buff);
-
-private:
-    boost::asio::ip::udp::socket   *_socket;
-    boost::asio::ip::udp::endpoint _receiver_endpoint;
-    boost::asio::ip::udp::endpoint _sender_endpoint;
-    boost::asio::io_service        _io_service;
-};
-
-/***********************************************************************
- * UDP public make function
- **********************************************************************/
-uhd::transport::udp::sptr uhd::transport::udp::make(
-    const std::string &addr,
-    const std::string &port,
-    bool bcast
-){
-    return uhd::transport::udp::sptr(new udp_impl(addr, port, bcast));
-}
-
-/***********************************************************************
- * UDP implementation methods
- **********************************************************************/
-udp_impl::udp_impl(const std::string &addr, const std::string &port, bool bcast){
-    //std::cout << boost::format("Creating udp transport for %s %s") % addr % port << std::endl;
-
-    // resolve the address
-    boost::asio::ip::udp::resolver resolver(_io_service);
-    boost::asio::ip::udp::resolver::query query(boost::asio::ip::udp::v4(), addr, port);
-    _receiver_endpoint = *resolver.resolve(query);
-
-    // Create and open the socket
-    _socket = new boost::asio::ip::udp::socket(_io_service);
-    _socket->open(boost::asio::ip::udp::v4());
-
-    if (bcast){
-        // Allow broadcasting
-        boost::asio::socket_base::broadcast option(true);
-        _socket->set_option(option);
-    }
-
-}
-
-udp_impl::~udp_impl(void){
-    delete _socket;
-}
-
-size_t udp_impl::send(const std::vector<boost::asio::const_buffer> &buffs){
-    return _socket->send_to(buffs, _receiver_endpoint);
-}
-
-size_t udp_impl::send(const boost::asio::const_buffer &buff){
-    return _socket->send_to(boost::asio::buffer(buff), _receiver_endpoint);
-}
-
-size_t udp_impl::recv(const std::vector<boost::asio::mutable_buffer> &buffs){
-    if (_socket->available() == 0) return 0;
-    return _socket->receive_from(buffs, _sender_endpoint);
-}
-
-size_t udp_impl::recv(const boost::asio::mutable_buffer &buff){
-    if (_socket->available() == 0) return 0;
-    return _socket->receive_from(boost::asio::buffer(buff), _sender_endpoint);
-}
diff --git a/host/lib/transport/udp_simple.cpp b/host/lib/transport/udp_simple.cpp
new file mode 100644
index 000000000..491cf59db
--- /dev/null
+++ b/host/lib/transport/udp_simple.cpp
@@ -0,0 +1,133 @@
+//
+// Copyright 2010 Ettus Research LLC
+//
+// 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/>.
+//
+
+#include <uhd/transport/udp_simple.hpp>
+#include <boost/format.hpp>
+#include <iostream>
+
+using namespace uhd::transport;
+
+/***********************************************************************
+ * UDP connected implementation class
+ **********************************************************************/
+class udp_connected_impl : public udp_simple{
+public:
+    //structors
+    udp_connected_impl(const std::string &addr, const std::string &port);
+    ~udp_connected_impl(void);
+
+    //send/recv
+    size_t send(const boost::asio::const_buffer &buff);
+    size_t recv(const boost::asio::mutable_buffer &buff);
+
+private:
+    boost::asio::ip::udp::socket   *_socket;
+    boost::asio::io_service        _io_service;
+};
+
+udp_connected_impl::udp_connected_impl(const std::string &addr, const std::string &port){
+    //std::cout << boost::format("Creating udp transport for %s %s") % addr % port << std::endl;
+
+    // resolve the address
+    boost::asio::ip::udp::resolver resolver(_io_service);
+    boost::asio::ip::udp::resolver::query query(boost::asio::ip::udp::v4(), addr, port);
+    boost::asio::ip::udp::endpoint receiver_endpoint = *resolver.resolve(query);
+
+    // Create, open, and connect the socket
+    _socket = new boost::asio::ip::udp::socket(_io_service);
+    _socket->open(boost::asio::ip::udp::v4());
+    _socket->connect(receiver_endpoint);
+}
+
+udp_connected_impl::~udp_connected_impl(void){
+    delete _socket;
+}
+
+size_t udp_connected_impl::send(const boost::asio::const_buffer &buff){
+    return _socket->send(boost::asio::buffer(buff));
+}
+
+size_t udp_connected_impl::recv(const boost::asio::mutable_buffer &buff){
+    if (_socket->available() == 0) return 0;
+    return _socket->receive(boost::asio::buffer(buff));
+}
+
+/***********************************************************************
+ * UDP broadcast implementation class
+ **********************************************************************/
+class udp_broadcast_impl : public udp_simple{
+public:
+    //structors
+    udp_broadcast_impl(const std::string &addr, const std::string &port);
+    ~udp_broadcast_impl(void);
+
+    //send/recv
+    size_t send(const boost::asio::const_buffer &buff);
+    size_t recv(const boost::asio::mutable_buffer &buff);
+
+private:
+    boost::asio::ip::udp::socket   *_socket;
+    boost::asio::ip::udp::endpoint _receiver_endpoint;
+    boost::asio::io_service        _io_service;
+};
+
+udp_broadcast_impl::udp_broadcast_impl(const std::string &addr, const std::string &port){
+    //std::cout << boost::format("Creating udp transport for %s %s") % addr % port << std::endl;
+
+    // resolve the address
+    boost::asio::ip::udp::resolver resolver(_io_service);
+    boost::asio::ip::udp::resolver::query query(boost::asio::ip::udp::v4(), addr, port);
+    _receiver_endpoint = *resolver.resolve(query);
+
+    // Create and open the socket
+    _socket = new boost::asio::ip::udp::socket(_io_service);
+    _socket->open(boost::asio::ip::udp::v4());
+
+    // Allow broadcasting
+    boost::asio::socket_base::broadcast option(true);
+    _socket->set_option(option);
+
+}
+
+udp_broadcast_impl::~udp_broadcast_impl(void){
+    delete _socket;
+}
+
+size_t udp_broadcast_impl::send(const boost::asio::const_buffer &buff){
+    return _socket->send_to(boost::asio::buffer(buff), _receiver_endpoint);
+}
+
+size_t udp_broadcast_impl::recv(const boost::asio::mutable_buffer &buff){
+    if (_socket->available() == 0) return 0;
+    boost::asio::ip::udp::endpoint sender_endpoint;
+    return _socket->receive_from(boost::asio::buffer(buff), sender_endpoint);
+}
+
+/***********************************************************************
+ * UDP public make functions
+ **********************************************************************/
+udp_simple::sptr udp_simple::make_connected(
+    const std::string &addr, const std::string &port
+){
+    return sptr(new udp_connected_impl(addr, port));
+}
+
+udp_simple::sptr udp_simple::make_broadcast(
+    const std::string &addr, const std::string &port
+){
+    return sptr(new udp_broadcast_impl(addr, port));
+}
diff --git a/host/lib/transport/udp_zero_copy_none.cpp b/host/lib/transport/udp_zero_copy_none.cpp
new file mode 100644
index 000000000..e95706d94
--- /dev/null
+++ b/host/lib/transport/udp_zero_copy_none.cpp
@@ -0,0 +1,117 @@
+//
+// Copyright 2010 Ettus Research LLC
+//
+// 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/>.
+//
+
+#include <uhd/transport/udp_zero_copy.hpp>
+
+using namespace uhd::transport;
+
+/***********************************************************************
+ * Smart buffer implementation for udp zerocopy none
+ *
+ * This smart buffer implemention houses a const buffer.
+ * When the smart buffer is deleted, the buffer is freed.
+ * The memory in the const buffer is allocated with new [],
+ * and so the destructor frees the buffer with delete [].
+ **********************************************************************/
+class smart_buffer_impl : public smart_buffer{
+public:
+    smart_buffer_impl(const boost::asio::const_buffer &buff){
+        _buff = buff;
+    }
+
+    ~smart_buffer_impl(void){
+        delete [] boost::asio::buffer_cast<const uint32_t *>(_buff);
+    }
+
+    const boost::asio::const_buffer &get(void) const{
+        return _buff;
+    }
+
+private:
+    boost::asio::const_buffer _buff;
+};
+
+/***********************************************************************
+ * UDP zero copy implementation class
+ *
+ * This is the portable zero copy implementation for systems
+ * where a faster, platform specific solution is not available.
+ *
+ * It uses boost asio udp sockets and the standard recv() class,
+ * and in-fact, is not actually doing a zero-copy implementation.
+ **********************************************************************/
+class udp_zero_copy_impl : public udp_zero_copy{
+public:
+    //structors
+    udp_zero_copy_impl(const std::string &addr, const std::string &port);
+    ~udp_zero_copy_impl(void);
+
+    //send/recv
+    size_t send(const boost::asio::const_buffer &buff);
+    smart_buffer::sptr recv(void);
+
+private:
+    boost::asio::ip::udp::socket   *_socket;
+    boost::asio::io_service        _io_service;
+};
+
+udp_zero_copy_impl::udp_zero_copy_impl(const std::string &addr, const std::string &port){
+    //std::cout << boost::format("Creating udp transport for %s %s") % addr % port << std::endl;
+
+    // resolve the address
+    boost::asio::ip::udp::resolver resolver(_io_service);
+    boost::asio::ip::udp::resolver::query query(boost::asio::ip::udp::v4(), addr, port);
+    boost::asio::ip::udp::endpoint receiver_endpoint = *resolver.resolve(query);
+
+    // Create, open, and connect the socket
+    _socket = new boost::asio::ip::udp::socket(_io_service);
+    _socket->open(boost::asio::ip::udp::v4());
+    _socket->connect(receiver_endpoint);
+}
+
+udp_zero_copy_impl::~udp_zero_copy_impl(void){
+    delete _socket;
+}
+
+size_t udp_zero_copy_impl::send(const boost::asio::const_buffer &buff){
+    return _socket->send(boost::asio::buffer(buff));
+}
+
+smart_buffer::sptr udp_zero_copy_impl::recv(void){
+    size_t available = _socket->available();
+
+    //allocate memory and create buffer
+    uint32_t *buff_mem = new uint32_t[available/sizeof(uint32_t)];
+    boost::asio::mutable_buffer buff(buff_mem, available);
+
+    //receive only if data is available
+    if (available > 0){
+        _socket->receive(boost::asio::buffer(buff));
+    }
+
+    //create a new smart buffer to house the data
+    return smart_buffer::sptr(new smart_buffer_impl(buff));
+}
+
+/***********************************************************************
+ * UDP zero copy make function
+ **********************************************************************/
+udp_zero_copy::sptr udp_zero_copy::make(
+    const std::string &addr, const std::string &port
+){
+    return sptr(new udp_zero_copy_impl(addr, port));
+}
diff --git a/host/lib/usrp/usrp2/io_impl.cpp b/host/lib/usrp/usrp2/io_impl.cpp
index 0ca2409c3..6969e0a89 100644
--- a/host/lib/usrp/usrp2/io_impl.cpp
+++ b/host/lib/usrp/usrp2/io_impl.cpp
@@ -36,12 +36,12 @@ static const float floats_per_short = 1.0/shorts_per_float;
  * Helper Functions
  **********************************************************************/
 void usrp2_impl::io_init(void){
-    //initially empty spillover buffer
-    _splillover_buff = asio::buffer(_spillover_mem, 0);
+    //initially empty copy buffer
+    _rx_copy_buff = asio::buffer("", 0);
 
     //send a small data packet so the usrp2 knows the udp source port
     uint32_t zero_data = 0;
-    _data_transport->send(boost::asio::buffer(&zero_data, sizeof(zero_data)));
+    _data_transport->send(asio::buffer(&zero_data, sizeof(zero_data)));
 }
 
 #define unrolled_loop(__i, __len, __inst) {\
@@ -57,6 +57,13 @@ void usrp2_impl::io_init(void){
     } \
 }
 
+// set a boolean flag that indicates the endianess
+#ifdef HAVE_BIG_ENDIAN
+static const bool is_big_endian = true;
+#else
+static const bool is_big_endian = false;
+#endif
+
 static inline void host_floats_to_usrp2_items(
     uint32_t *usrp2_items,
     const fc32_t *host_floats,
@@ -87,9 +94,12 @@ static inline void host_items_to_usrp2_items(
     const uint32_t *host_items,
     size_t num_samps
 ){
-    unrolled_loop(i, num_samps,
-        usrp2_items[i] = htonl(host_items[i])
-    );
+    if (is_big_endian){
+        std::memcpy(usrp2_items, host_items, num_samps*sizeof(uint32_t));
+    }
+    else{
+        unrolled_loop(i, num_samps, usrp2_items[i] = htonl(host_items[i]));
+    }
 }
 
 static inline void usrp2_items_to_host_items(
@@ -97,20 +107,22 @@ static inline void usrp2_items_to_host_items(
     const uint32_t *usrp2_items,
     size_t num_samps
 ){
-    unrolled_loop(i, num_samps,
-        host_items[i] = ntohl(usrp2_items[i])
-    );
+    if (is_big_endian){
+        std::memcpy(host_items, usrp2_items, num_samps*sizeof(uint32_t));
+    }
+    else{
+        unrolled_loop(i, num_samps, host_items[i] = ntohl(usrp2_items[i]));
+    }
 }
 
 /***********************************************************************
  * Send Raw Data
  **********************************************************************/
-size_t usrp2_impl::send_raw(
-    const boost::asio::const_buffer &buff,
-    const uhd::metadata_t &metadata
-){
-    std::vector<boost::asio::const_buffer> buffs(2);
-    uint32_t vrt_hdr[7]; //max size
+size_t usrp2_impl::send_raw(const uhd::metadata_t &metadata){
+    size_t num_items = asio::buffer_size(_tx_copy_buff)/sizeof(uint32_t);
+    const uint32_t *items = asio::buffer_cast<const uint32_t *>(_tx_copy_buff);
+
+    uint32_t vrt_hdr[_tx_vrt_max_offset_words32];
     uint32_t vrt_hdr_flags = 0;
     size_t num_vrt_hdr_words = 1;
 
@@ -131,60 +143,30 @@ size_t usrp2_impl::send_raw(
     //fill in complete header word
     vrt_hdr[0] = htonl(vrt_hdr_flags |
         ((_tx_stream_id_to_packet_seq[metadata.stream_id]++ & 0xf) << 16) |
-        ((num_vrt_hdr_words + asio::buffer_size(buff)/sizeof(uint32_t)) & 0xffff)
+        ((num_vrt_hdr_words + num_items) & 0xffff)
     );
 
-    //load the buffer vector
-    size_t vrt_hdr_size = num_vrt_hdr_words*sizeof(uint32_t);
-    buffs[0] = asio::buffer(&vrt_hdr, vrt_hdr_size);
-    buffs[1] = buff;
+    //copy in the vrt header (yes we left space)
+    std::memcpy(((uint32_t *)items) - num_vrt_hdr_words, vrt_hdr, num_vrt_hdr_words);
+    asio::const_buffer buff(items - num_vrt_hdr_words, (num_vrt_hdr_words + num_items)*sizeof(uint32_t));
 
     //send and return number of samples
-    return (_data_transport->send(buffs) - vrt_hdr_size)/sizeof(sc16_t);
+    return (_data_transport->send(buff) - num_vrt_hdr_words*sizeof(uint32_t))/sizeof(sc16_t);
 }
 
 /***********************************************************************
  * Receive Raw Data
  **********************************************************************/
-size_t usrp2_impl::recv_raw(
-    const boost::asio::mutable_buffer &buff,
-    uhd::metadata_t &metadata
-){
-    metadata = metadata_t(); //clear metadata
-
-    //handle the case where there is spillover
-    if (asio::buffer_size(_splillover_buff) != 0){
-        size_t bytes_to_copy = std::min(
-            asio::buffer_size(_splillover_buff),
-            asio::buffer_size(buff)
-        );
-        std::memcpy(
-            asio::buffer_cast<void*>(buff),
-            asio::buffer_cast<const void*>(_splillover_buff),
-            bytes_to_copy
-        );
-        _splillover_buff = asio::buffer(
-            asio::buffer_cast<uint8_t*>(_splillover_buff)+bytes_to_copy,
-            asio::buffer_size(_splillover_buff)-bytes_to_copy
-        );
-        //std::cout << boost::format("Copied spillover %d samples") % (bytes_to_copy/sizeof(sc16_t)) << std::endl;
-        return bytes_to_copy/sizeof(sc16_t);
-    }
-
-    //load the buffer vector
-    std::vector<boost::asio::mutable_buffer> buffs(3);
-    uint32_t vrt_hdr[USRP2_HOST_RX_VRT_HEADER_WORDS32];
-    buffs[0] = asio::buffer(vrt_hdr, sizeof(vrt_hdr));
-    buffs[1] = buff;
-    buffs[2] = asio::buffer(_spillover_mem, _mtu);
+void usrp2_impl::recv_raw(uhd::metadata_t &metadata){
+    //do a receive
+    _rx_smart_buff = _data_transport->recv();
 
-    //receive into the buffers
-    size_t bytes_recvd = _data_transport->recv(buffs);
-
-    //failure case
-    if (bytes_recvd < sizeof(vrt_hdr)) return 0;
+    ////////////////////////////////////////////////////////////////////
+    // !!!! FIXME this is very flawed, use a proper vrt unpacker !!!!!!!
+    ////////////////////////////////////////////////////////////////////
 
     //unpack the vrt header
+    const uint32_t *vrt_hdr = asio::buffer_cast<const uint32_t *>(_rx_smart_buff->get());
     metadata = uhd::metadata_t();
     uint32_t vrt_header = ntohl(vrt_hdr[0]);
     metadata.has_stream_id = true;
@@ -202,13 +184,12 @@ size_t usrp2_impl::recv_raw(
     size_t num_words = (vrt_header & 0xffff) -
         USRP2_HOST_RX_VRT_HEADER_WORDS32 -
         USRP2_HOST_RX_VRT_TRAILER_WORDS32;
-    size_t num_bytes = num_words*sizeof(uint32_t);
-
-    //handle the case where spillover memory was used
-    size_t spillover_size = num_bytes - std::min(num_bytes, asio::buffer_size(buff));
-    _splillover_buff = asio::buffer(_spillover_mem, spillover_size);
 
-    return (num_bytes - spillover_size)/sizeof(sc16_t);
+    //setup the rx buffer to point to the data
+    _rx_copy_buff = boost::asio::buffer(
+        vrt_hdr + USRP2_HOST_RX_VRT_HEADER_WORDS32,
+        num_words*sizeof(uint32_t)
+    );
 }
 
 /***********************************************************************
@@ -219,37 +200,26 @@ size_t usrp2_impl::send(
     const uhd::metadata_t &metadata,
     const std::string &type
 ){
-    if (type == "32fc"){
-        size_t num_samps = asio::buffer_size(buff)/sizeof(fc32_t);
-        boost::asio::mutable_buffer raw_buff(_tmp_send_mem, num_samps*sizeof(sc16_t));
+    uint32_t *items = _tx_mem + _tx_vrt_max_offset_words32; //offset for data
+    size_t num_samps = _max_samples_per_packet;
 
-        host_floats_to_usrp2_items(
-            asio::buffer_cast<uint32_t*>(raw_buff),
-            asio::buffer_cast<const fc32_t*>(buff),
-            num_samps
-        );
-
-        return send_raw(raw_buff, metadata);
+    //calculate the number of samples to be copied
+    //and copy the samples into the send buffer
+    if (type == "32fc"){
+        num_samps = std::min(asio::buffer_size(buff)/sizeof(fc32_t), num_samps);
+        host_floats_to_usrp2_items(items, asio::buffer_cast<const fc32_t*>(buff), num_samps);
     }
-
-    if (type == "16sc"){
-        #ifdef HAVE_BIG_ENDIAN
-        return send_raw(buff, metadata);
-        #else
-        size_t num_samps = asio::buffer_size(buff)/sizeof(sc16_t);
-        boost::asio::mutable_buffer raw_buff(_tmp_send_mem, num_samps*sizeof(sc16_t));
-
-        host_items_to_usrp2_items(
-            asio::buffer_cast<uint32_t*>(raw_buff),
-            asio::buffer_cast<const uint32_t*>(buff),
-            num_samps
-        );
-
-        return send_raw(raw_buff, metadata);
-        #endif
+    else if (type == "16sc"){
+        num_samps = std::min(asio::buffer_size(buff)/sizeof(sc16_t), num_samps);
+        host_items_to_usrp2_items(items, asio::buffer_cast<const uint32_t*>(buff), num_samps);
+    }
+    else{
+        throw std::runtime_error(str(boost::format("usrp2 send: cannot handle type \"%s\"") % type));
     }
 
-    throw std::runtime_error(str(boost::format("usrp2 send: cannot handle type \"%s\"") % type));
+    //send the samples (this line seems silly, will be better with vrt lib)
+    _tx_copy_buff = asio::buffer(items, num_samps*sizeof(uint32_t));
+    return send_raw(metadata); //return num_samps;
 }
 
 /***********************************************************************
@@ -260,39 +230,31 @@ size_t usrp2_impl::recv(
     uhd::metadata_t &metadata,
     const std::string &type
 ){
-    if (type == "32fc"){
-        size_t num_samps = asio::buffer_size(buff)/sizeof(fc32_t);
-        boost::asio::mutable_buffer raw_buff(_tmp_recv_mem, num_samps*sizeof(sc16_t));
-
-        num_samps = recv_raw(raw_buff, metadata);
+    //perform a receive if no rx data is waiting to be copied
+    if (asio::buffer_size(_rx_copy_buff) == 0) recv_raw(metadata);
+    //TODO otherwise flag the metadata to show that is is a fragment
 
-        usrp2_items_to_host_floats(
-            asio::buffer_cast<fc32_t*>(buff),
-            asio::buffer_cast<const uint32_t*>(raw_buff),
-            num_samps
-        );
+    //extract the number of samples available to copy
+    //and a pointer into the usrp2 received items memory
+    size_t num_samps = asio::buffer_size(_rx_copy_buff)/sizeof(uint32_t);
+    const uint32_t *items = asio::buffer_cast<const uint32_t*>(_rx_copy_buff);
 
-        return num_samps;
+    //calculate the number of samples to be copied
+    //and copy the samples from the recv buffer
+    if (type == "32fc"){
+        num_samps = std::min(asio::buffer_size(buff)/sizeof(fc32_t), num_samps);
+        usrp2_items_to_host_floats(asio::buffer_cast<fc32_t*>(buff), items, num_samps);
     }
-
-    if (type == "16sc"){
-        #ifdef HAVE_BIG_ENDIAN
-        return recv_raw(buff, metadata);
-        #else
-        size_t num_samps = asio::buffer_size(buff)/sizeof(sc16_t);
-        boost::asio::mutable_buffer raw_buff(_tmp_recv_mem, num_samps*sizeof(sc16_t));
-
-        num_samps = recv_raw(raw_buff, metadata);
-
-        usrp2_items_to_host_items(
-            asio::buffer_cast<uint32_t*>(buff),
-            asio::buffer_cast<const uint32_t*>(raw_buff),
-            num_samps
-        );
-
-        return num_samps;
-        #endif
+    else if (type == "16sc"){
+        num_samps = std::min(asio::buffer_size(buff)/sizeof(sc16_t), num_samps);
+        usrp2_items_to_host_items(asio::buffer_cast<uint32_t*>(buff), items, num_samps);
+    }
+    else{
+        throw std::runtime_error(str(boost::format("usrp2 recv: cannot handle type \"%s\"") % type));
     }
 
-    throw std::runtime_error(str(boost::format("usrp2 recv: cannot handle type \"%s\"") % type));
+    //update the rx copy buffer to reflect the bytes copied
+    _rx_copy_buff = asio::buffer(items + num_samps, num_samps*sizeof(uint32_t));
+
+    return num_samps;
 }
diff --git a/host/lib/usrp/usrp2/usrp2_impl.cpp b/host/lib/usrp/usrp2/usrp2_impl.cpp
index 700f94ae1..51082df15 100644
--- a/host/lib/usrp/usrp2/usrp2_impl.cpp
+++ b/host/lib/usrp/usrp2/usrp2_impl.cpp
@@ -23,6 +23,7 @@
 
 using namespace uhd;
 using namespace uhd::usrp;
+using namespace uhd::transport;
 
 /***********************************************************************
  * Discovery over the udp transport
@@ -33,8 +34,9 @@ uhd::device_addrs_t usrp2::discover(const device_addr_t &hint){
     //create a udp transport to communicate
     //TODO if an addr is not provided, search all interfaces?
     std::string ctrl_port = boost::lexical_cast<std::string>(USRP2_UDP_CTRL_PORT);
-    transport::udp::sptr udp_transport = \
-        transport::udp::make(hint["addr"], ctrl_port, true);
+    udp_simple::sptr udp_transport = udp_simple::make_broadcast(
+        hint["addr"], ctrl_port
+    );
 
     //send a hello control packet
     usrp2_ctrl_data_t ctrl_data_out;
@@ -76,16 +78,18 @@ uhd::device_addrs_t usrp2::discover(const device_addr_t &hint){
 /***********************************************************************
  * Make
  **********************************************************************/
-#define num2str(num) (boost::lexical_cast<std::string>(num))
+template <class T> std::string num2str(T num){
+    return boost::lexical_cast<std::string>(num);
+}
 
 device::sptr usrp2::make(const device_addr_t &device_addr){
     //create a control transport
-    transport::udp::sptr ctrl_transport = transport::udp::make(
+    udp_simple::sptr ctrl_transport = udp_simple::make_connected(
         device_addr["addr"], num2str(USRP2_UDP_CTRL_PORT)
     );
 
     //create a data transport
-    transport::udp::sptr data_transport = transport::udp::make(
+    udp_zero_copy::sptr data_transport = udp_zero_copy::make(
         device_addr["addr"], num2str(USRP2_UDP_DATA_PORT)
     );
 
@@ -99,8 +103,8 @@ device::sptr usrp2::make(const device_addr_t &device_addr){
  * Structors
  **********************************************************************/
 usrp2_impl::usrp2_impl(
-    transport::udp::sptr ctrl_transport,
-    transport::udp::sptr data_transport
+    udp_simple::sptr ctrl_transport,
+    udp_zero_copy::sptr data_transport
 ){
     _ctrl_transport = ctrl_transport;
     _data_transport = data_transport;
diff --git a/host/lib/usrp/usrp2/usrp2_impl.hpp b/host/lib/usrp/usrp2/usrp2_impl.hpp
index 037aed477..a58bf8471 100644
--- a/host/lib/usrp/usrp2/usrp2_impl.hpp
+++ b/host/lib/usrp/usrp2/usrp2_impl.hpp
@@ -22,7 +22,8 @@
 #include <boost/thread.hpp>
 #include <boost/shared_ptr.hpp>
 #include <boost/function.hpp>
-#include <uhd/transport/udp.hpp>
+#include <uhd/transport/udp_simple.hpp>
+#include <uhd/transport/udp_zero_copy.hpp>
 #include <uhd/usrp/dboard_manager.hpp>
 #include "fw_common.h"
 
@@ -81,8 +82,8 @@ public:
      * \param data_transport the udp transport for data
      */
     usrp2_impl(
-        uhd::transport::udp::sptr ctrl_transport,
-        uhd::transport::udp::sptr data_transport
+        uhd::transport::udp_simple::sptr ctrl_transport,
+        uhd::transport::udp_zero_copy::sptr data_transport
     );
 
     ~usrp2_impl(void);
@@ -103,8 +104,8 @@ public:
 
 private:
     //the raw io interface (samples are in the usrp2 native format)
-    size_t send_raw(const boost::asio::const_buffer &, const uhd::metadata_t &);
-    size_t recv_raw(const boost::asio::mutable_buffer &, uhd::metadata_t &);
+    size_t send_raw(const uhd::metadata_t &);
+    void recv_raw(uhd::metadata_t &);
     uhd::dict<uint32_t, size_t> _tx_stream_id_to_packet_seq;
     uhd::dict<uint32_t, size_t> _rx_stream_id_to_packet_seq;
     static const size_t _mtu = 1500; //FIXME we have no idea
@@ -114,15 +115,16 @@ private:
         USRP2_HOST_RX_VRT_TRAILER_WORDS32 -
         ((2 + 14 + 20 + 8)/sizeof(uint32_t)) //size of headers (pad, eth, ip, udp)
     ;
-    uint32_t _tmp_send_mem[_mtu/sizeof(uint32_t)];
-    uint32_t _tmp_recv_mem[_mtu/sizeof(uint32_t)];
-    uint32_t _spillover_mem[_mtu/sizeof(uint32_t)];
-    boost::asio::mutable_buffer _splillover_buff;
+    static const size_t _tx_vrt_max_offset_words32 = 7; //TODO move to future vrt lib
+    uint32_t _tx_mem[_mtu/sizeof(uint32_t)];
+    boost::asio::const_buffer _tx_copy_buff;
+    uhd::transport::smart_buffer::sptr _rx_smart_buff;
+    boost::asio::const_buffer _rx_copy_buff;
     void io_init(void);
 
     //udp transports for control and data
-    uhd::transport::udp::sptr _ctrl_transport;
-    uhd::transport::udp::sptr _data_transport;
+    uhd::transport::udp_simple::sptr _ctrl_transport;
+    uhd::transport::udp_zero_copy::sptr _data_transport;
 
     //private vars for dealing with send/recv control
     uint32_t _ctrl_seq_num;