Comment 0 for bug 1749214

Firstly, apologies if this isn't a bug in cifs.mount - I know it's intimitly connected to a recent kernel updates which changed the default SMB version cifs connects with, but I'm having trouble distinguishing whether this behaviour is caused by the kernel change or a problem with cifs.

On a recently built 16.04.3 LTS box with kernel 4.4.0-109, I was able to mount to a network DFS share with the following

mount.cifs -o user=username //pathto/share /mountpoint

and after doing so, I was able to navigate through the mounted share, and through the underlying DFS structure with no problems. The mount command notably contained 'vers=1.0' - which was expected.

After updating the kernel to 4.13.0.32, if I run the same command, the share appears to mount, but I get a 'cannot access ...: Input/Output error' when trying to move through a DFS mount within the mounted filesystem.

Notably, the output from the mount command has 'vers=default'.

I understand from various sources, that the default SMB vers is now 3.0 - and if I mount this share explicitly with

mount.cifs -o user=username,vers=3.0 //pathto/share /mountpoint

Then I see 'vers=3' on the output from mount, and am able to use the share as expected.

The man page for the cifs.mount cmd still says the default is SMB1.0 (this appeared to be the case with a kernel previous to 4.13). The kernel sources now say the default is SMB 3.0 - which would also be find, if the share is mounted with vers=3.0.

But instead I'm seeing 'vers=default' - and I'm unsure as to what version of SMB it's actually trying to use (if any) - whatever it is, it doesn't work unless I explicitly set vers=3.0.