Jumbo Frames on Memif PMD

[Julien Plante <julien.plante@obspm.fr>]

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Hi,

I'm trying to use the memif PMD with Jumbo Frames, without any success yet.
Please note that I'm currently using DPDK 21.11, but could consider 
updating.


On standard packet size, I'm able to transmit packets using memif with 
the following commands:

Terminal 1 (receiver, launch first):
# ./dpdk-testpmd -l 2-3 --vdev=net_memif0,id=0,role=server 
--file-prefix=pmd1 -- --forward-mode=rxonly --max-pkt-len=1518

Terminal 2 (sender, launch second):
# ./dpdk-testpmd -l 0-1 --vdev=net_memif0,id=0,role=client 
--file-prefix=pmd2 -- --forward-mode=txonly --max-pkt-len=1518


When trying to send Jumbo Frames, I get an error on the server launch:

# ./dpdk-testpmd -l 2-3 --vdev=net_memif0,id=0,role=server 
--file-prefix=pmd1 -- --forward-mode=rxonly --max-pkt-len=9000
...
Frame size (9000) > device max frame size (1518) for port_id 0
...


Do you know if it is possible to increase this device max frame size for 
the memif PMD ?


About what I tried:

- Changing the bsize (Size of single packet buffer) option of the PMD to 
a value higher than 9000 (I tried 9000 and 2^14=16384).
  I did not understand what this parameter changes, but it did not seem 
to help, the error stayed the same.

- Reading the doc (both DPDK 
<https://doc.dpdk.org/guides/nics/memif.html>'s and VPP 
<https://docs.fd.io/vpp/17.10/libmemif_doc.html>'s), searching for MTU 
limitations, but saw no such thing.

- Start from the error message to find where the device max frame size 
is set. It is initialized at drivers/net/memif/rte_eth_memif.c:198,
  to the value RTE_ETHER_MAX_LEN (1518), and left untouched after that. 
Is there any reason to limit the PMD to this value, or we could
  add a setter for this value ?


Thanks for any help on this issue,
Julien



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