Re: Linux CIFS client module: login rate limiting

[Valentin Hilbig <externer.dl.hilbig-EnyPcy3oyxIb1SvskN2V4Q@public.gmane.org>]

On 2017-01-24 at 10:57, Sachin Prabhu wrote:
> On Mon, 2017-01-23 at 16:27 +0530, Sachin Prabhu wrote:
>> On Fri, 2017-01-20 at 15:30 -0600, Steve French wrote:

>> cifs_reconnect_tcon()
>> {
>> ..
>>          mutex_lock(&ses->session_mutex);
>>          rc = cifs_negotiate_protocol(0, ses);
>>          if (rc == 0 && ses->need_reconnect)
>>                  rc = cifs_setup_session(0, ses, nls_codepage);
>> ..
>> }
>> Where in case of EACCES, we can setup a delayed work to unlock ses-
>>> session_mutex set to run after the required interval.

> Attached is a patch which can work in this case. I use a cache interval
> of 10 seconds which can be extended further.

It took a while until I found time to test your suggested patch.
Sorry for the delay.  Please note that your patch needs a small patch:

In cifsglob.h (around line 835) the

+	bool cached_rc;

should read

+	int  cached_rc;

as it holds the rc, not a flag.

Then it works as expected!  As soon as the reconnect fails due to 
password trouble, CIFS pauses 10s until the next retry.  Wonderful. ;)

So thank you very much for pointing me into the right direction!

As soon as everything is finished here I will report back to this list 
to give you the link to GitHub where I pushed my patches against Ubuntu 
3.13 and 4.4 kernels.

CU
-Tino