4 files changed, 11 insertions, 9 deletions
diff --git a/host/lib/usrp/usrp2/fw_common.h b/host/lib/usrp/usrp2/fw_common.h
index 75f5b1779..242d268ec 100644
--- a/host/lib/usrp/usrp2/fw_common.h
+++ b/host/lib/usrp/usrp2/fw_common.h
@@ -32,9 +32,13 @@ extern "C" {
 #define _SINS_
 #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 3
+#define USRP2_PROTO_VERSION 4
 
 //used to differentiate control packets over data port
 #define USRP2_INVALID_VRT_HEADER 0
@@ -102,7 +106,7 @@ typedef struct{
         struct {
             _SINS_ uint8_t addr;
             _SINS_ uint8_t bytes;
-            _SINS_ uint8_t data[sizeof(_SINS_ uint32_t)];
+            _SINS_ uint8_t data[20];
         } i2c_args;
         struct {
             _SINS_ uint32_t addr;
diff --git a/host/lib/usrp/usrp2/usrp2_iface.cpp b/host/lib/usrp/usrp2/usrp2_iface.cpp
index 6e0d3266a..83e98904e 100644
--- a/host/lib/usrp/usrp2/usrp2_iface.cpp
+++ b/host/lib/usrp/usrp2/usrp2_iface.cpp
@@ -146,7 +146,7 @@ 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[1500]; //allocate MTU bytes for recv
+        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);
         while(true){
             size_t len = _ctrl_transport->recv(boost::asio::buffer(usrp2_ctrl_data_in_mem));
diff --git a/host/lib/usrp/usrp2/usrp2_impl.cpp b/host/lib/usrp/usrp2/usrp2_impl.cpp
index 0837f4ac4..36c264c3c 100644
--- a/host/lib/usrp/usrp2/usrp2_impl.cpp
+++ b/host/lib/usrp/usrp2/usrp2_impl.cpp
@@ -79,12 +79,12 @@ 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[1500]; //allocate MTU bytes for recv
+    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);
     while(true){
         size_t len = udp_transport->recv(asio::buffer(usrp2_ctrl_data_in_mem));
         //std::cout << len << "\n";
-        if (len >= sizeof(usrp2_ctrl_data_t)){
+        if (len > offsetof(usrp2_ctrl_data_t, data)){
             //handle the received data
             switch(ntohl(ctrl_data_in->id)){
             case USRP2_CTRL_ID_WAZZUP_DUDE:
diff --git a/host/lib/usrp/usrp2/usrp2_impl.hpp b/host/lib/usrp/usrp2/usrp2_impl.hpp
index ccc09003e..2126b9565 100644
--- a/host/lib/usrp/usrp2/usrp2_impl.hpp
+++ b/host/lib/usrp/usrp2/usrp2_impl.hpp
@@ -141,15 +141,13 @@ private:
     /*******************************************************************
      * Deal with the rx and tx packet sizes
      ******************************************************************/
-    static const size_t _mtu = 1500; //FIXME we have no idea
-    static const size_t _hdrs = (2 + 14 + 20 + 8); //size of headers (pad, eth, ip, udp)
     static const size_t _max_rx_bytes_per_packet =
-        _mtu - _hdrs -
+        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_tx_bytes_per_packet =
-        _mtu - _hdrs -
+        USRP2_UDP_BYTES -
         uhd::transport::vrt::max_header_words32*sizeof(boost::uint32_t)
     ;