On 17/06/2024 19:54, cjohn...@serranosystems.com wrote:
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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I have run into a similar issue, years ago, with a *1Gig* interface
blindly accepting a jumbo-frame MTU request, but
actually being unable to in reality honor it.
Now, that would be unusual with a 10GiG card--what card type do you
have? Are you running direct, or through a
switch?
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