Created attachment 12306 [details]
Network capture with cifs of kernel 3.19 (Mint 17.3)
When cifs connects to a LANMAN2 server it sends invalid TRANS2 requests on certain file operations, probably at stat().
In fact cifs requests info level ALL_INFO (263) at QUERY_PATH_INFO. This info level did not exist at the LANMAN2 protocol level and so the server responds with unknown info level (126).
AFAIK the appropriate info level for this purpose should be STANDARD (1).
Some applications seem to ignore this response and work, e.g. mc is able to browse directories and open files. Other applications dislike the errors and quit or have malfunction, e.g. git, Eclipse.
In fact connections to OS/2 and probably Win98 are unusable.
I attached a Wireshark capture from Linux Mint 17.3, kernel 3.19.0 (cifs 2.06) accessing an OS/2 (eCS 1.05) share with IBM Peer server (latest fixpacks applied). The capture includes the session setup. The problem happens first at #23.
Other TRANS2 requests seem to share similar problems, e.g. #15 QUERY_DEVICE_INFO.
Created attachment 12307 [details]
Network capture with cifs of kernel 4.4 (Raspbian Jessie)
I just tested with a newer cifs version (2.08). Same problem. See attached network trace.