[cifs-protocol] Endpoint mapper max_towers parameter behavior in Map call

Samuel Cabrero scabrero at samba.org
Tue Dec 22 13:00:36 UTC 2020


Hi DocHelp,

I have found a strange behavior of the max_towers parameter in the EPM
Map call when it is issued to an address assigned to a clustered file
server role.

After booting the cluster, all EPM Map calls issued to the IP address
assigned to the clustered file server role, asking for the witness
endpoint, and having max_towers equal to 1 return 0x16C9A0D6 (There are
no elements satisfying the specified search criteria, according to MS-
RPCE). Once a call having max_towers greater than 1 is issued,
subsequent requests having max_towers equal to 1 succeed.

Please check the attached capture for an example of this behavior. The
IP address 192.168.103.200 is assigned to a clustered file server as
you can see in the screenshot.

* Map requests having max_tower == 1 in frames 34, 37, 40, 43 and 46
does not return the tower.
* Map request having max_tower == 2 in frame 49 succeed.
* Map requests having max_tower == 1 in frames 53, 56, 59, 62 and 65
succeed.

I have not found any requirements for the max_towers parameter in MS-
RPCE. Is there a minimum value for any particular case? Could you
please explain this behavior?

-- 
Samuel
-------------- next part --------------
A non-text attachment was scrubbed...
Name: test_epm_max_towers.pcapng
Type: application/x-pcapng
Size: 13032 bytes
Desc: not available
URL: <http://lists.samba.org/pipermail/cifs-protocol/attachments/20201222/d3c42f8f/test_epm_max_towers.bin>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: fs_role.png
Type: image/png
Size: 95443 bytes
Desc: not available
URL: <http://lists.samba.org/pipermail/cifs-protocol/attachments/20201222/d3c42f8f/fs_role.png>


More information about the cifs-protocol mailing list