If you have problem with Ubuntu 18.04 or some Ubuntu like installation when you try to mount Samba/SMB/CIFS mount you get following error:
CIFS VFS: Error connecting to socket. Aborting operation
CIFS VFS: cifs_mount failed w/return code = -115
You have problem with DNS/IPv6 bug and to solve it you have 2 solutions.
First instead to use on this mount DNS name like cifs.example.com use IPv4 address like xxx.xxx.xxx.xxx (same applies to manual mount with mount command or by editing /etc/fstab).
Second solution is to turn off IPv6 for this computer. Edit /etc/sysctl.conf to insert lines in the form of
“net.ipv6.conf.*.disable_ipv6 = 1”, replacing * with “all“, “lo“, “default“, and “eth0” for exact interface,
then give the shell command “sudo sysctl -p“