Direct RNIC connection fails, but works when connected through IB Switch

[LiuMicheal]

My environment:
Ubuntu 18.04
Kernel: 4.15.0-46-generic
RNIC: CX4 (MCX456A-ECAT) in IB mode
MLNX_OFED_LINUX-4.9-3.1.5.0

I compiled and insmod KRdmaKitSyscall.ko correctly. When I used rc_connect_client_kernel.cc to test, I found that if two RNICs were directly connected, an error would be reported, as shown in the figure below.

However, if the two RNICs were connected through an IB Switch, it would run correctly! It is recommended that you use KRCORE in a network connected by IB Switch :)

[wxdwfc]

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