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Date: Tue, 13 Jul 2021 13:29:21 +0200 (CEST)
From: dennis.wagner@tuta.io
To: users@dpdk.org
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Subject: [dpdk-users] DPDK layer 2 forwarding without modification / disable
 offloading
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Hello,

I am a student of computer science in Germany. Sorry, if this is a basic question.
I am trying to do some latency benchmarks with DPDK as a layer 2 relay. Here is what I did:

* my server is running Debian 10 and has 2 NICs Intel I210 Gigabit
* NICs are configured: dpdk-devbind.py --bind=uio_pci_generic 0000:02:00.0 / 0000:05:00.0
* examples/skeleton/basicfwd.c is used to relay traffic
* to measure the latency, traffic is recorded before and after the dpdk-box with tcpdump
* compare the 2 traces of a http download

I expected DPDK to pass all frames unmodified, but some frames after the handshake the traces start to diverge: the length of the frames change.

Could hardware offloading like TSO be the reason? How would I completely disable offloading?
Is this done in my DPDK application or with a tool like ethtool per interface?

Setting the offloads field in basicfwd.c (port_conf.txmode.offoads = 0; port_conf.rxmode.offoads = 0) did not work.

Thanks!

Dennis