Tcpdump for RoCE

Related to post Sniff RoCE traffic using tcpdump - #2 by samerka

I am able to collect packets, but it ends up collecting tcp, udp packets…
Using tcpdump options like “udp” or “udp port 4791” doesn’t collect any packets.
Any reason? Is there a different way to restrict to collecting only RoCE packets?

To capture RoCE offload packets, you need use latest libpcap and rebuild tcpdump.

Follow tcpdump guide compile libpcap and tcpdump.


Actual issue is that I’m not able to filter during collection (I can filter later in wireshark or by reading pcap file…)

sudo tcpdump -i mlx5_0 -s 0 -w rdma.pcap

  • This collects all packets, udp, tcp, any port, etc… This is too much for debugging…

sudo tcpdump -i mlx5_0 udp port 4791 -s 0 -w rdma.pcap

  • This collects 0 packets.

sudo tcpdump -i mlx5_0 udp -s 0 -w rdma.pcap

  • Same here… No packets collected.

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