We have followed all instructions on the website and searched the forums with no solutions. I have provided much evidence below that USRP/UHD driver is not behaving properly in this case.\ \ We are trying to send a 8192 byte packet to the x310 with the latest UHD 4.6 (FPGA 39.2) which also didn’t seem to work with UHD 4.3 using the 10GigE interface. We technically have a USRP-2974, but I think it is irrelevant.
\ The 8192 data is being fragmented into 2 packets (Length 8042 and 266 on the wire using tcpdump). **You will be able to demonstrate very similar behavior by making the following change to host/examples/tx_samples_c.c (which sends a Length 8034 and 258 on the the wire).**\ // Set up buffer\ \#if 1\ samps_per_buff = 2048; // (\~8192 bytes)\ \#else\ EXECUTE_OR_GOTO(\ free_tx_streamer, uhd_tx_streamer_max_num_samps(tx_streamer, &samps_per_buff))\ fprintf(stderr, “Buffer size in samples: %zu\\n”, samps_per_buff);#endif\ **Please note, the interface has been configured to MTU 9000 along with the other changes mentioned in <https://files.ettus.com/manual/page_usrp_x3x0_config.html>**\ enp1s0f0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 9000inet 192.168.40.1 netmask 255.255.255.0 broadcast 192.168.40.255\ **When I run the program, you can see an indication of a USRP problem** “Maximum frame size: 8000 bytes.”\ >: \~/uhd-4.6.0.0/host/build/examples$ ./tx_samples_c\ Creating USRP with args “”...\ \[INFO\] \[UHD\] linux; GNU C++ version 9.4.0; Boost_107100; UHD_4.6.0.0-1-ga9f0b4c7\ \[INFO\] \[X300\] X300 initialization sequence...\ \[INFO\] \[X300\] Maximum frame size: 8000 bytes.\ \[INFO\] \[GPS\] Found an internal GPSDO: LC_XO, Firmware Rev 0.929a\ \[INFO\] \[X300\] Radio 1x clock: 200 MHz\ Setting TX Rate: 200000000.000000...\ Actual TX Rate: 200000000.000000...\ Setting TX Gain: 0.000000 db...\ Actual TX Gain: 0.000000...\ Setting TX frequency: 2000.000000 MHz...\ Actual TX frequency: 2000.000000 MHz...\ \[WARNING\] \[0/Radio#0\] Attempting to set tick rate to 0. Skipping.\ Press Ctrl+C to stop streaming...\ **I have change parameters (**send_frame_size) **to force the tx packet to 9000 in USRP stream, but I get this message which makes no sense. Also tried 8500, same complaint.**\ \[WARNING\] \[X300\] You requested a send frame size of (9000) but your NIC’s max frame size is (8000).Please verify your NIC’s MTU setting using ‘ip link’ or set the send_frame_size argument appropriately.UHD will use the auto-detected max frame size for this connection.\ Interesting enough, at 8000 it does not complain. Of course we are fragmenting because 8192 bytes packet.\ \------\ **I have confirmed that ping with larger size packet doesn’t work.**\ cjohnson@USRP-1:\~$ ping -s 8200 192.168.40.2\ PING 192.168.40.2 (192.168.40.2) 8200(8228) bytes of data.\ ^C\ \--- 192.168.40.2 ping statistics ---\ 33 packets transmitted, 0 received, 100% packet loss, time 32758ms
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