Merge branch 'error_handling' of ettus.sourcerepo.com:ettus/uhdpriv into usrp_e

9 files changed, 126 insertions, 99 deletions

diff --git a/host/lib/transport/gen_vrt_if_packet.py b/host/lib/transport/gen_vrt_if_packet.py
index 9b5bfca02..07ce391ee 100755
--- a/host/lib/transport/gen_vrt_if_packet.py
+++ b/host/lib/transport/gen_vrt_if_packet.py
@@ -61,13 +61,6 @@ using namespace uhd::transport;
 #set $tsf_p = 0b01000
 #set $tlr_p = 0b10000
 
-static UHD_INLINE void pack_uint64_$(suffix)(boost::uint64_t num, boost::uint32_t *mem){
-    //*(reinterpret_cast<boost::uint64_t *>(mem)) = $(XE_MACRO)(num);
-    //second word is lower 32 bits due to fpga implementation
-    mem[1] = $(XE_MACRO)(boost::uint32_t(num >> 0));
-    mem[0] = $(XE_MACRO)(boost::uint32_t(num >> 32));
-}
-
 void vrt::if_hdr_pack_$(suffix)(
     boost::uint32_t *packet_buff,
     if_packet_info_t &if_packet_info
@@ -94,8 +87,10 @@ void vrt::if_hdr_pack_$(suffix)(
         #end if
         ########## Class ID ##########
         #if $pred & $cid_p
-            pack_uint64_$(suffix)(if_packet_info.cid, packet_buff+$num_header_words);
-            #set $num_header_words += 2
+            packet_buff[$num_header_words] = 0; //not implemented
+            #set $num_header_words += 1
+            packet_buff[$num_header_words] = 0; //not implemented
+            #set $num_header_words += 1
             #set $flags |= (0x1 << 27);
         #end if
         ########## Integer Time ##########
@@ -106,8 +101,10 @@ void vrt::if_hdr_pack_$(suffix)(
         #end if
         ########## Fractional Time ##########
         #if $pred & $tsf_p
-            pack_uint64_$(suffix)(if_packet_info.tsf, packet_buff+$num_header_words);
-            #set $num_header_words += 2
+            packet_buff[$num_header_words] = $(XE_MACRO)(boost::uint32_t(if_packet_info.tsf >> 32));
+            #set $num_header_words += 1
+            packet_buff[$num_header_words] = $(XE_MACRO)(boost::uint32_t(if_packet_info.tsf >> 0));
+            #set $num_header_words += 1
             #set $flags |= (0x1 << 20);
         #end if
         ########## Trailer ##########
@@ -116,7 +113,6 @@ void vrt::if_hdr_pack_$(suffix)(
             #set $flags |= (0x1 << 26);
             #set $num_trailer_words = 1;
         #else
-            //packet_buff[$num_header_words+if_packet_info.num_payload_words32] = 0;
             #set $num_trailer_words = 0;
         #end if
         ########## Variables ##########
@@ -139,13 +135,6 @@ void vrt::if_hdr_pack_$(suffix)(
     ));
 }
 
-static UHD_INLINE void unpack_uint64_$(suffix)(boost::uint64_t &num, const boost::uint32_t *mem){
-    //num = $(XE_MACRO)(*reinterpret_cast<const boost::uint64_t *>(mem));
-    //second word is lower 32 bits due to fpga implementation
-    num =  boost::uint64_t($(XE_MACRO)(mem[1])) << 0;
-    num |= boost::uint64_t($(XE_MACRO)(mem[0])) << 32;
-}
-
 void vrt::if_hdr_unpack_$(suffix)(
     const boost::uint32_t *packet_buff,
     if_packet_info_t &if_packet_info
@@ -153,13 +142,16 @@ void vrt::if_hdr_unpack_$(suffix)(
     //extract vrt header
     boost::uint32_t vrt_hdr_word = $(XE_MACRO)(packet_buff[0]);
     size_t packet_words32 = vrt_hdr_word & 0xffff;
-    if_packet_info.packet_count = (vrt_hdr_word >> 16) & 0xf;
 
-    //failure cases
+    //failure case
     if (if_packet_info.num_packet_words32 < packet_words32)
         throw std::runtime_error("bad vrt header or packet fragment");
-    if (vrt_hdr_word & (0x7 << 29))
-        throw std::runtime_error("bad vrt header or unsupported packet type");
+
+    //extract fields from the header
+    if_packet_info.packet_type = if_packet_info_t::packet_type_t(vrt_hdr_word >> 29);
+    if_packet_info.packet_count = (vrt_hdr_word >> 16) & 0xf;
+    if_packet_info.sob = bool(vrt_hdr_word & $hex(0x1 << 25));
+    if_packet_info.eob = bool(vrt_hdr_word & $hex(0x1 << 24));
 
     boost::uint8_t pred = 0;
     if(vrt_hdr_word & $hex(0x1 << 28)) pred |= $hex($sid_p);
@@ -184,7 +176,7 @@ void vrt::if_hdr_unpack_$(suffix)(
         ########## Class ID ##########
         #if $pred & $cid_p
             if_packet_info.has_cid = true;
-            unpack_uint64_$(suffix)(if_packet_info.cid, packet_buff+$num_header_words);
+            if_packet_info.cid = 0; //not implemented
             #set $num_header_words += 2
         #else
             if_packet_info.has_cid = false;
@@ -200,15 +192,17 @@ void vrt::if_hdr_unpack_$(suffix)(
         ########## Fractional Time ##########
         #if $pred & $tsf_p
             if_packet_info.has_tsf = true;
-            unpack_uint64_$(suffix)(if_packet_info.tsf, packet_buff+$num_header_words);
-            #set $num_header_words += 2
+            if_packet_info.tsf = boost::uint64_t($(XE_MACRO)(packet_buff[$num_header_words])) << 32;
+            #set $num_header_words += 1
+            if_packet_info.tsf |= boost::uint64_t($(XE_MACRO)(packet_buff[$num_header_words])) << 0;
+            #set $num_header_words += 1
         #else
             if_packet_info.has_tsf = false;
         #end if
         ########## Trailer ##########
         #if $pred & $tlr_p
             if_packet_info.has_tlr = true;
-            if_packet_info.tlr = $(XE_MACRO)(packet_buff[$num_header_words+packet_words32]);
+            if_packet_info.tlr = $(XE_MACRO)(packet_buff[packet_words32-1]);
             #set $num_trailer_words = 1;
         #else
             if_packet_info.has_tlr = false;
diff --git a/host/lib/transport/udp_zero_copy_asio.cpp b/host/lib/transport/udp_zero_copy_asio.cpp
index 7f9292d24..e3f3ef5bf 100644
--- a/host/lib/transport/udp_zero_copy_asio.cpp
+++ b/host/lib/transport/udp_zero_copy_asio.cpp
@@ -16,6 +16,7 @@
 //
 
 #include <uhd/transport/udp_zero_copy.hpp>
+#include <uhd/transport/udp_simple.hpp> //mtu
 #include <uhd/utils/assert.hpp>
 #include <boost/cstdint.hpp>
 #include <boost/asio.hpp>
@@ -29,7 +30,6 @@ using namespace uhd::transport;
  **********************************************************************/
 //enough buffering for half a second of samples at full rate on usrp2
 static const size_t MIN_SOCK_BUFF_SIZE = size_t(sizeof(boost::uint32_t) * 25e6 * 0.5);
-static const size_t MAX_DGRAM_SIZE = 1500; //assume max size on send and recv
 static const double RECV_TIMEOUT = 0.1; //100 ms
 
 /***********************************************************************
@@ -51,8 +51,8 @@ public:
         const std::string &addr,
         const std::string &port
     ):
-        phony_zero_copy_recv_if(MAX_DGRAM_SIZE),
-        phony_zero_copy_send_if(MAX_DGRAM_SIZE)
+        phony_zero_copy_recv_if(udp_simple::mtu),
+        phony_zero_copy_send_if(udp_simple::mtu)
     {
         //std::cout << boost::format("Creating udp transport for %s %s") % addr % port << std::endl;
 
@@ -93,11 +93,11 @@ public:
     //This way, the transport caller will have an idea about how much buffering to create.
 
     size_t get_num_recv_frames(void) const{
-        return this->get_buff_size<boost::asio::socket_base::receive_buffer_size>()/MAX_DGRAM_SIZE;
+        return this->get_buff_size<boost::asio::socket_base::receive_buffer_size>()/udp_simple::mtu;
     }
 
     size_t get_num_send_frames(void) const{
-        return this->get_buff_size<boost::asio::socket_base::send_buffer_size>()/MAX_DGRAM_SIZE;
+        return this->get_buff_size<boost::asio::socket_base::send_buffer_size>()/udp_simple::mtu;
     }
 
 private:
@@ -155,17 +155,17 @@ template<typename Opt> static void resize_buff_helper(
         else std::cout << boost::format(
             "Current %s sock buff size: %d bytes"
         ) % name % actual_size << std::endl;
+        if (actual_size < target_size) std::cerr << boost::format(
+            "Warning:\n"
+            "    The %s buffer is smaller than the requested size.\n"
+            "    The minimum recommended buffer size is %d bytes.\n"
+            "    See the USRP2 application notes on buffer resizing.\n"
+        ) % name % MIN_SOCK_BUFF_SIZE << std::endl;
     }
 
     //otherwise, ensure that the buffer is at least the minimum size
     else if (udp_trans->get_buff_size<Opt>() < MIN_SOCK_BUFF_SIZE){
         resize_buff_helper<Opt>(udp_trans, MIN_SOCK_BUFF_SIZE, name);
-        if (udp_trans->get_buff_size<Opt>() < MIN_SOCK_BUFF_SIZE){
-            std::cerr << boost::format(
-                "Warning: the %s buffer size is smaller than the recommended size of %d bytes.\n"
-                "    See the USRP2 application notes on buffer resizing."
-            ) % name % MIN_SOCK_BUFF_SIZE << std::endl;
-        }
     }
 }
 
diff --git a/host/lib/transport/vrt_packet_handler.hpp b/host/lib/transport/vrt_packet_handler.hpp
index 68edeb1e1..11d749a81 100644
--- a/host/lib/transport/vrt_packet_handler.hpp
+++ b/host/lib/transport/vrt_packet_handler.hpp
@@ -21,6 +21,7 @@
 #include <uhd/config.hpp>
 #include <uhd/device.hpp>
 #include <uhd/utils/assert.hpp>
+#include <uhd/utils/byteswap.hpp>
 #include <uhd/types/io_type.hpp>
 #include <uhd/types/otw_type.hpp>
 #include <uhd/types/metadata.hpp>
@@ -39,6 +40,9 @@ namespace vrt_packet_handler{
  **********************************************************************/
     typedef std::vector<uhd::transport::managed_recv_buffer::sptr> managed_recv_buffs_t;
     typedef boost::function<bool(managed_recv_buffs_t &)> get_recv_buffs_t;
+    typedef boost::function<void(size_t /*which channel*/)> handle_overrun_t;
+
+    void handle_overrun_nop(size_t){}
 
     struct recv_state{
         //width of the receiver in channels
@@ -53,7 +57,7 @@ namespace vrt_packet_handler{
         size_t size_of_copy_buffs;
         size_t fragment_offset_in_samps;
 
-        recv_state(size_t width):
+        recv_state(size_t width = 1):
             width(width),
             next_packet_seq(width, 0),
             managed_buffs(width),
@@ -75,20 +79,25 @@ namespace vrt_packet_handler{
         uhd::rx_metadata_t &metadata,
         double tick_rate,
         vrt_unpacker_type vrt_unpacker,
+        const handle_overrun_t &handle_overrun,
         size_t vrt_header_offset_words32
     ){
-        size_t num_packet_words32 = state.managed_buffs[0]->size()/sizeof(boost::uint32_t);
-        if (num_packet_words32 <= vrt_header_offset_words32){
-            state.size_of_copy_buffs = 0;
-            return; //must exit here after setting the buffer
-        }
-
         //vrt unpack each managed buffer
         uhd::transport::vrt::if_packet_info_t if_packet_info;
         for (size_t i = 0; i < state.width; i++){
+
+            //extract packet words and check thats its enough to move on
+            size_t num_packet_words32 = state.managed_buffs[i]->size()/sizeof(boost::uint32_t);
+            if (num_packet_words32 <= vrt_header_offset_words32){
+                state.size_of_copy_buffs = 0;
+                return; //must exit here after setting the buffer
+            }
+
+            //unpack the vrt header into the info struct
             const boost::uint32_t *vrt_hdr = state.managed_buffs[i]->cast<const boost::uint32_t *>() + vrt_header_offset_words32;
             if_packet_info.num_packet_words32 = num_packet_words32 - vrt_header_offset_words32;
             vrt_unpacker(vrt_hdr, if_packet_info);
+            const boost::uint32_t *vrt_data = vrt_hdr + if_packet_info.num_header_words32;
 
             //handle the packet count / sequence number
             if (if_packet_info.packet_count != state.next_packet_seq[i]){
@@ -96,8 +105,19 @@ namespace vrt_packet_handler{
             }
             state.next_packet_seq[i] = (if_packet_info.packet_count+1)%16;
 
+            //make sure that its a data packet (TODO handle non-data packets)
+            if (if_packet_info.packet_type != uhd::transport::vrt::if_packet_info_t::PACKET_TYPE_DATA){
+                std::cout << "vrt packet handler _recv1_helper got non data packet" << std::endl;
+                //extract the context word (we dont know the endianness so mirror the bytes)
+                boost::uint32_t word0 = vrt_data[0] | uhd::byteswap(vrt_data[0]);
+                if (word0 & 8) handle_overrun(i);
+                // 4: broken chain, 2: late command...
+                state.size_of_copy_buffs = 0;
+                return; //must exit here after setting the buffer
+            }
+
             //setup the buffer to point to the data
-            state.copy_buffs[i] = reinterpret_cast<const boost::uint8_t *>(vrt_hdr + if_packet_info.num_header_words32);
+            state.copy_buffs[i] = reinterpret_cast<const boost::uint8_t *>(vrt_data);
 
             //store the minimum payload length into the copy buffer length
             size_t num_payload_bytes = if_packet_info.num_payload_words32*sizeof(boost::uint32_t);
@@ -111,6 +131,9 @@ namespace vrt_packet_handler{
         metadata.time_spec = uhd::time_spec_t(
             time_t(if_packet_info.tsi), size_t(if_packet_info.tsf), tick_rate
         );
+        metadata.start_of_burst = if_packet_info.sob;
+        static const int tlr_eob_flags = (1 << 20) | (1 << 8); //enable and indicator bits
+        metadata.end_of_burst = if_packet_info.has_tlr and (int(if_packet_info.tlr & tlr_eob_flags) == tlr_eob_flags);
     }
 
     /*******************************************************************
@@ -129,7 +152,7 @@ namespace vrt_packet_handler{
         double tick_rate,
         vrt_unpacker_type vrt_unpacker,
         const get_recv_buffs_t &get_recv_buffs,
-        //use these two params to handle a layer above vrt
+        const handle_overrun_t &handle_overrun,
         size_t vrt_header_offset_words32
     ){
         metadata.has_time_spec = false; //false unless set in the helper
@@ -140,7 +163,9 @@ namespace vrt_packet_handler{
             if (not get_recv_buffs(state.managed_buffs)) return 0;
             try{
                 _recv1_helper(
-                    state, metadata, tick_rate, vrt_unpacker, vrt_header_offset_words32
+                    state, metadata, tick_rate,
+                    vrt_unpacker, handle_overrun,
+                    vrt_header_offset_words32
                 );
             }catch(const std::exception &e){
                 std::cerr << "Error (recv): " << e.what() << std::endl;
@@ -191,7 +216,7 @@ namespace vrt_packet_handler{
         double tick_rate,
         vrt_unpacker_type vrt_unpacker,
         const get_recv_buffs_t &get_recv_buffs,
-        //use these two params to handle a layer above vrt
+        const handle_overrun_t &handle_overrun = &handle_overrun_nop,
         size_t vrt_header_offset_words32 = 0
     ){
         switch(recv_mode){
@@ -208,6 +233,7 @@ namespace vrt_packet_handler{
                 tick_rate,
                 vrt_unpacker,
                 get_recv_buffs,
+                handle_overrun,
                 vrt_header_offset_words32
             );
         }
@@ -227,6 +253,7 @@ namespace vrt_packet_handler{
                     tick_rate,
                     vrt_unpacker,
                     get_recv_buffs,
+                    handle_overrun,
                     vrt_header_offset_words32
                 );
                 if (num_samps == 0) break; //had a recv timeout or error, break loop
@@ -315,7 +342,6 @@ namespace vrt_packet_handler{
         vrt_packer_type vrt_packer,
         const get_send_buffs_t &get_send_buffs,
         size_t max_samples_per_packet,
-        //use these two params to handle a layer above vrt
         size_t vrt_header_offset_words32 = 0
     ){
         //translate the metadata to vrt if packet info
diff --git a/host/lib/types.cpp b/host/lib/types.cpp
index 9cf2a2220..1e7917ad7 100644
--- a/host/lib/types.cpp
+++ b/host/lib/types.cpp
@@ -99,7 +99,9 @@ rx_metadata_t::rx_metadata_t(void):
     has_time_spec(false),
     time_spec(time_spec_t()),
     more_fragments(false),
-    fragment_offset(0)
+    fragment_offset(0),
+    start_of_burst(false),
+    end_of_burst(false)
 {
     /* NOP */
 }
diff --git a/host/lib/usrp/usrp2/fw_common.h b/host/lib/usrp/usrp2/fw_common.h
index 4c66aa41e..fd728e393 100644
--- a/host/lib/usrp/usrp2/fw_common.h
+++ b/host/lib/usrp/usrp2/fw_common.h
@@ -24,18 +24,14 @@
  * Therefore, this header may only contain valid C code.
  */
 #ifdef __cplusplus
-#include <boost/cstdint.hpp>
-#define _SINS_ boost:://stdint namespace when in c++
+    #include <boost/cstdint.hpp>
+    #define __stdint(type) boost::type
 extern "C" {
 #else
-#include <stdint.h>
-#define _SINS_
+    #include <stdint.h>
+    #define __stdint(type) type
 #endif
 
-// define limits on bytes per udp packet
-#define USRP2_MTU_BYTES 1500
-#define USRP2_UDP_BYTES ((USRP2_MTU_BYTES) - (2 + 14 + 20 + 8)) //size of headers (pad, eth, ip, udp)
-
 //defines the protocol version in this shared header
 //increment this value when the protocol is changed
 #define USRP2_PROTO_VERSION 5
@@ -43,10 +39,6 @@ extern "C" {
 //used to differentiate control packets over data port
 #define USRP2_INVALID_VRT_HEADER 0
 
-// size of the vrt header and trailer to the host
-#define USRP2_HOST_RX_VRT_HEADER_WORDS32 5
-#define USRP2_HOST_RX_VRT_TRAILER_WORDS32 1 //FIXME fpga sets wrong header size when no trailer present
-
 // udp ports for the usrp2 communication
 // Dynamic and/or private ports: 49152-65535
 #define USRP2_UDP_CTRL_PORT 49152
@@ -90,34 +82,35 @@ typedef enum{
 } usrp2_clk_edge_t;
 
 typedef struct{
-    _SINS_ uint32_t proto_ver;
-    _SINS_ uint32_t id;
-    _SINS_ uint32_t seq;
+    __stdint(uint32_t) proto_ver;
+    __stdint(uint32_t) id;
+    __stdint(uint32_t) seq;
     union{
-        _SINS_ uint32_t ip_addr;
+        __stdint(uint32_t) ip_addr;
         struct {
-            _SINS_ uint8_t dev;
-            _SINS_ uint8_t miso_edge;
-            _SINS_ uint8_t mosi_edge;
-            _SINS_ uint8_t readback;
-            _SINS_ uint32_t data;
-            _SINS_ uint8_t num_bits;
+            __stdint(uint8_t) dev;
+            __stdint(uint8_t) miso_edge;
+            __stdint(uint8_t) mosi_edge;
+            __stdint(uint8_t) readback;
+            __stdint(uint32_t) data;
+            __stdint(uint8_t) num_bits;
         } spi_args;
         struct {
-            _SINS_ uint8_t addr;
-            _SINS_ uint8_t bytes;
-            _SINS_ uint8_t data[20];
+            __stdint(uint8_t) addr;
+            __stdint(uint8_t) bytes;
+            __stdint(uint8_t) data[20];
         } i2c_args;
         struct {
-            _SINS_ uint32_t addr;
-            _SINS_ uint32_t data;
-            _SINS_ uint32_t addrhi;
-            _SINS_ uint32_t datahi;
-            _SINS_ uint8_t num_bytes; //1, 2, 4, 8
+            __stdint(uint32_t) addr;
+            __stdint(uint32_t) data;
+            __stdint(uint32_t) addrhi;
+            __stdint(uint32_t) datahi;
+            __stdint(uint8_t) num_bytes; //1, 2, 4, 8
         } poke_args;
     } data;
 } usrp2_ctrl_data_t;
 
+#undef __stdint
 #ifdef __cplusplus
 }
 #endif
diff --git a/host/lib/usrp/usrp2/io_impl.cpp b/host/lib/usrp/usrp2/io_impl.cpp
index c96528694..0853f48be 100644
--- a/host/lib/usrp/usrp2/io_impl.cpp
+++ b/host/lib/usrp/usrp2/io_impl.cpp
@@ -135,7 +135,7 @@ void usrp2_impl::io_init(void){
     for (size_t i = 0; i < _data_transports.size(); i++){
         _io_impl->recv_pirate_crew.create_thread(boost::bind(
             &usrp2_impl::io_impl::recv_pirate_loop,
-            _io_impl, _data_transports.at(i),
+            _io_impl.get(), _data_transports.at(i),
             _mboards.at(i), i
         ));
     }
@@ -195,6 +195,6 @@ size_t usrp2_impl::recv(
         io_type, _io_helper.get_rx_otw_type(),     //input and output types to convert
         _mboards.front()->get_master_clock_freq(), //master clock tick rate
         uhd::transport::vrt::if_hdr_unpack_be,
-        boost::bind(&usrp2_impl::io_impl::get_recv_buffs, _io_impl, _1)
+        boost::bind(&usrp2_impl::io_impl::get_recv_buffs, _io_impl.get(), _1)
     );
 }
diff --git a/host/lib/usrp/usrp2/usrp2_iface.cpp b/host/lib/usrp/usrp2/usrp2_iface.cpp
index 8552edd1f..eaaa722ac 100644
--- a/host/lib/usrp/usrp2/usrp2_iface.cpp
+++ b/host/lib/usrp/usrp2/usrp2_iface.cpp
@@ -26,13 +26,14 @@
 #include <algorithm>
 
 using namespace uhd;
+using namespace uhd::transport;
 
 class usrp2_iface_impl : public usrp2_iface{
 public:
 /***********************************************************************
  * Structors
  **********************************************************************/
-    usrp2_iface_impl(transport::udp_simple::sptr ctrl_transport){
+    usrp2_iface_impl(udp_simple::sptr ctrl_transport){
         _ctrl_transport = ctrl_transport;
     }
 
@@ -160,7 +161,7 @@ public:
         _ctrl_transport->send(boost::asio::buffer(&out_copy, sizeof(usrp2_ctrl_data_t)));
 
         //loop until we get the packet or timeout
-        boost::uint8_t usrp2_ctrl_data_in_mem[USRP2_UDP_BYTES]; //allocate max bytes for recv
+        boost::uint8_t usrp2_ctrl_data_in_mem[udp_simple::mtu]; //allocate max bytes for recv
         const usrp2_ctrl_data_t *ctrl_data_in = reinterpret_cast<const usrp2_ctrl_data_t *>(usrp2_ctrl_data_in_mem);
         while(true){
             size_t len = _ctrl_transport->recv(boost::asio::buffer(usrp2_ctrl_data_in_mem));
@@ -182,7 +183,7 @@ public:
 
 private:
     //this lovely lady makes it all possible
-    transport::udp_simple::sptr _ctrl_transport;
+    udp_simple::sptr _ctrl_transport;
 
     //used in send/recv
     boost::mutex _ctrl_mutex;
@@ -222,6 +223,6 @@ private:
 /***********************************************************************
  * Public make function for usrp2 interface
  **********************************************************************/
-usrp2_iface::sptr usrp2_iface::make(transport::udp_simple::sptr ctrl_transport){
+usrp2_iface::sptr usrp2_iface::make(udp_simple::sptr ctrl_transport){
     return usrp2_iface::sptr(new usrp2_iface_impl(ctrl_transport));
 }
diff --git a/host/lib/usrp/usrp2/usrp2_impl.cpp b/host/lib/usrp/usrp2/usrp2_impl.cpp
index 3402c26b1..02f53bc69 100644
--- a/host/lib/usrp/usrp2/usrp2_impl.cpp
+++ b/host/lib/usrp/usrp2/usrp2_impl.cpp
@@ -99,8 +99,8 @@ static uhd::device_addrs_t usrp2_find(const device_addr_t &hint){
     udp_transport->send(boost::asio::buffer(&ctrl_data_out, sizeof(ctrl_data_out)));
 
     //loop and recieve until the timeout
-    boost::uint8_t usrp2_ctrl_data_in_mem[USRP2_UDP_BYTES]; //allocate max bytes for recv
-    usrp2_ctrl_data_t *ctrl_data_in = reinterpret_cast<usrp2_ctrl_data_t *>(usrp2_ctrl_data_in_mem);
+    boost::uint8_t usrp2_ctrl_data_in_mem[udp_simple::mtu]; //allocate max bytes for recv
+    const usrp2_ctrl_data_t *ctrl_data_in = reinterpret_cast<const usrp2_ctrl_data_t *>(usrp2_ctrl_data_in_mem);
     while(true){
         size_t len = udp_transport->recv(asio::buffer(usrp2_ctrl_data_in_mem));
         //std::cout << len << "\n";
@@ -127,14 +127,25 @@ static uhd::device_addrs_t usrp2_find(const device_addr_t &hint){
 /***********************************************************************
  * Make
  **********************************************************************/
+template <typename out_type, typename in_type>
+out_type lexical_cast(const in_type &in){
+    try{
+        return boost::lexical_cast<out_type>(in);
+    }catch(...){
+        throw std::runtime_error(str(boost::format(
+            "failed to cast \"%s\" to type \"%s\""
+        ) % boost::lexical_cast<std::string>(in) % typeid(out_type).name()));
+    }
+}
+
 static device::sptr usrp2_make(const device_addr_t &device_addr){
     //extract the receive and send buffer sizes
     size_t recv_buff_size = 0, send_buff_size= 0 ;
     if (device_addr.has_key("recv_buff_size")){
-        recv_buff_size = size_t(boost::lexical_cast<double>(device_addr["recv_buff_size"]));
+        recv_buff_size = size_t(lexical_cast<double>(device_addr["recv_buff_size"]));
     }
     if (device_addr.has_key("send_buff_size")){
-        send_buff_size = size_t(boost::lexical_cast<double>(device_addr["send_buff_size"]));
+        send_buff_size = size_t(lexical_cast<double>(device_addr["send_buff_size"]));
     }
 
     //create a ctrl and data transport for each address
diff --git a/host/lib/usrp/usrp2/usrp2_impl.hpp b/host/lib/usrp/usrp2/usrp2_impl.hpp
index 42630a3e4..186516447 100644
--- a/host/lib/usrp/usrp2/usrp2_impl.hpp
+++ b/host/lib/usrp/usrp2/usrp2_impl.hpp
@@ -32,6 +32,7 @@
 #include <boost/shared_ptr.hpp>
 #include <boost/function.hpp>
 #include <uhd/transport/vrt_if_packet.hpp>
+#include <uhd/transport/udp_simple.hpp> //mtu
 #include <uhd/transport/udp_zero_copy.hpp>
 #include <uhd/usrp/dboard_manager.hpp>
 
@@ -106,15 +107,14 @@ public:
 
 private:
     uhd::otw_type_t _rx_otw_type, _tx_otw_type;
-    static const size_t _max_rx_bytes_per_packet =
-        USRP2_UDP_BYTES -
-        USRP2_HOST_RX_VRT_HEADER_WORDS32*sizeof(boost::uint32_t) -
-        USRP2_HOST_RX_VRT_TRAILER_WORDS32*sizeof(boost::uint32_t)
+    static const size_t _max_rx_bytes_per_packet = uhd::transport::udp_simple::mtu
+        - uhd::transport::vrt::max_if_hdr_words32*sizeof(boost::uint32_t)
+        - sizeof(uhd::transport::vrt::if_packet_info_t().tlr) //forced to have trailer
+        + sizeof(uhd::transport::vrt::if_packet_info_t().cid) //no class id ever used
     ;
-    static const size_t _max_tx_bytes_per_packet =
-        USRP2_UDP_BYTES -
-        uhd::transport::vrt::max_if_hdr_words32*sizeof(boost::uint32_t) -
-        sizeof(uhd::transport::vrt::if_packet_info_t().cid) //no class id ever used
+    static const size_t _max_tx_bytes_per_packet = uhd::transport::udp_simple::mtu
+        - uhd::transport::vrt::max_if_hdr_words32*sizeof(boost::uint32_t)
+        + sizeof(uhd::transport::vrt::if_packet_info_t().cid) //no class id ever used
     ;
 };