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From:   Yang Yang <yang.yang29@zte.com.cn>
To:     willemdebruijn.kernel@gmail.com
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Subject: RE: [PATCH linux-next 1/3] selftests: net: udpgso_bench_rx: Fix verifty exceptions
Date:   Tue, 18 Apr 2023 09:29:10 +0800
Message-Id: <20230418012910.194745-1-yang.yang29@zte.com.cn>
In-Reply-To: <643d62b28e413_29adc929416@willemb.c.googlers.com.notmuch>
References: <643d62b28e413_29adc929416@willemb.c.googlers.com.notmuch>
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> Why are you running two senders concurrently? The test is not intended
> to handle that case.

Sorry for the inaccuracy of the description here, these two commands,
i.e. with or without GSO, cause the problem. The same goes for patch 2/3.
The problem is easily reproducible in the latest kernel, QEMU environment, E1000.

bash# udpgso_bench_tx -l 4 -4 -D "$DST" 
udpgso_bench_tx: write: Connection refused
bash# udpgso_bench_rx -4 -G -S 1472 -v
udpgso_bench_rx: data[1472]: len 17664, a(97) != q(113)

bash# udpgso_bench_tx -l 4 -4 -D "$DST" -S 0
udpgso_bench_tx: sendmsg: Connection refused
bash# udpgso_bench_rx -4 -G -S 1472 -v
udpgso_bench_rx: data[61824]: len 64768, a(97) != w(119)

In one test, the verification data is printed as follows:
abcd...xyz
...
abcd...xyz
abcd...opabcd...xyz

This is because the sender intercepts from the buf at a certain length,
which is not aligned according to 26 bytes, and multiple packets are
merged. The verification of the receiving end needs to be performed
after splitting.