Hi, Curt, last time I observed it working was on combination of CentOS-7.2 + MOFED-3.3-1.0.4.0.
Indeed worked as advertised: set sniffer flags using patched ethtool (e.g. installed on my system /opt/mellanox/ethtool/sbin/ethtool), tcpdump -i <interface> -w <file> does the job. Latest stable of wireshark does not decode traffic for me well, but unstable build does ok (I browse captured files on Windows using wireshark 2.1.1).
Regard,
Philip