[Bug 1767454] Re: "Other Locations" does not automatically find Samba servers in Ubuntu 18.04

[Andreas Hasenack]

Defaults for xenial (samba 4.3.11):
  client min protocol = CORE
  client max protocol = default (which is NT1 in this version of samba)

Defaults for artful (samba 4.6.7):
  client min protocol = CORE
  client max protocol = default (which is NT1 in this version of samba)

Defaults for bionic (samba 4.7.6):
  client min protocol = CORE
  client max protocol = default (which is SMB3_11 in this version of samba)

So before bionic, if you wanted a more secure protocol, you had to
specify it (like smbclient's -m SMB3 option).

Now in bionic, if you want a *less* secure protocol. you have to specify
it.

Ideally, computer browsing and actually connecting to shares should
happen with different protocol versions.

smbclient in bionic does a quick downgrade to NT1 when needed. Notice the "Reconnecting" message intertwined in the output below:
ubuntu at bionic-desktop:~$ smbclient -L xenial -N -m SMB3
Anonymous login successful

	Sharename       Type      Comment
	---------       ----      -------
	print$          Disk      Printer Drivers
	public          Disk      Public share
	IPC$            IPC       IPC Service (xenial-desktop server (Samba, Ubuntu))
Reconnecting with SMB1 for workgroup listing.
Anonymous login successful

	Server               Comment
	---------            -------

	Workgroup            Master
	---------            -------
	UBUNTU               XENIAL


In artful, that downgrade does not happen, and we don't get the workgroup listing:
ubuntu at artful-desktop:~$ smbclient -L xenial -N -m SMB3
Anonymous login successful

	Sharename       Type      Comment
	---------       ----      -------
	print$          Disk      Printer Drivers
	public          Disk      Public share
	IPC$            IPC       IPC Service (xenial-desktop server (Samba, Ubuntu))
Anonymous login successful

	Server               Comment
	---------            -------

	Workgroup            Master
	---------            -------
ubuntu at artful-desktop:~$ 


I suspect smbtree does the same. In bionic, where max protocol is SMB3_11 by default, it works out of the box. But in artful, if I set client max protocol to SMB3_11, it stops working:
ubuntu at artful-desktop:~$ testparm -s -v 2>/dev/null|grep "client max protocol"
	client max protocol = default
ubuntu at artful-desktop:~$ smbtree
UBUNTU
	\\XENIAL         		xenial-desktop server (Samba, Ubuntu)
		\\XENIAL\IPC$           	IPC Service (xenial-desktop server (Samba, Ubuntu))
		\\XENIAL\public         	Public share
		\\XENIAL\print$         	Printer Drivers
	\\BIONIC         		bionic-desktop server (Samba, Ubuntu)
		\\BIONIC\IPC$           	IPC Service (bionic-desktop server (Samba, Ubuntu))
		\\BIONIC\public         	Public share
		\\BIONIC\print$         	Printer Drivers
	\\ARTFUL         		artful-desktop server (Samba, Ubuntu)
		\\ARTFUL\IPC$           	IPC Service (artful-desktop server (Samba, Ubuntu))
		\\ARTFUL\public         	Public share
		\\ARTFUL\print$         	Printer Drivers
ubuntu at artful-desktop:~$ sudo vi /etc/samba/smb.conf 
ubuntu at artful-desktop:~$ testparm -s -v 2>/dev/null|grep "client max protocol"
	client max protocol = SMB3
ubuntu at artful-desktop:~$ smbtree
ubuntu at artful-desktop:~$ 


So in summay, bionic samba's own tools seem to know when NT1 is needed and downgrade appropriately. Ideally the rest of the smb ecosystem should do the same, assuming there is no way to get the computer listing with non-NT1 protocols.

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https://bugs.launchpad.net/bugs/1767454

Title:
  "Other Locations" does not automatically find Samba servers in Ubuntu
  18.04

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