Attached is a preliminary version of Wireshark with InfiniBand support for RoCEv2. In time, it will be added to the Wireshark upstream.
After the installation, click Edit -> Preferences -> Protocols -> InfiniBand, and perform the following adjustments:
1. Type the UDP port as 4791 (RoCEv2 default).
2. Make sure the two check boxes on top are cleared.
Following the steps above, you can open any *.pcapng file to see the InfiniBand parsing of the RoCE traffic.
Here is a parsing example of the BTH header of a CNP packet, OpCode 0x81 (RoCEv2 Congestion Management Ack):