Interop Issue: SMB2+ async replies, and the kernel, Samba side fix enclosed.

[Pavel Shilovsky]

2016-02-27 12:11 GMT+03:00 Pavel Shilovsky <pshilovsky at samba.org>:
> 2016-02-23 15:55 GMT+03:00 Ira Cooper <ira at wakeful.net>:
>>
>> If the server sends an interim response, then the real response, the real
>> response, is handled by standard_receive3() in the kernel, instead of the
>> proper function, and this causes a disconnect.  If there isn't a
>> disconnect, I believe the reply will just be discarded if I understand the
>> code correctly.  (That is a big if here ;) )
>>
>> I've written a patch for Samba to stop sending interim replies on
>> SMB2_READ
>> and SMB2_WRITE, when non-compounded to stop the impact of this issue.  We
>> may want to add SMB2_CREATE to the list of ops we don't send async replies
>> for non-compounded, but I'm not sold either way, I know we CAN go async
>> there!  I want some opinions here.
>>
>> This is not hidden behind a flag because compatibility issues that don't
>> impact protocol correctness usually aren't.
>>
>> Setting req->async_te = talloc_new(NULL); is just ugly, though it works.
>> If you have a cleaner approach, I welcome it.
>>
>> I request you please ASK me before pushing this one, yes, that means you
>> jra!
>>
>> For those interested in reproduction: I'd suggest using a server that's
>> rebuilt with a lower timeout set in smb2_read.c, though we've hit it with
>> vfs_glusterfs straight up, in our testing.
>>
>> Thanks,
>>
>> -Ira / ira@(samba.org|redhat.com|wakeful.net)
>
>
>
> Thank you for catching this!
>
> It is the issue in the kernel client - a check for interim responses is
> missed for SMB2_READ command. I created a patch that should fix the problem.
>
> Could you please test it?
>
> --
> Best regards,
> Pavel Shilovsky

CC'ing @samba-technical.

Sorry for the spam.

-- 
Best regards,
Pavel Shilovsky
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