DOS clients slow on Samba 4.1.7+ (bug 10422)

Volker Lendecke Volker.Lendecke at SerNet.DE
Fri Oct 10 07:26:51 MDT 2014

On Fri, Oct 10, 2014 at 02:08:30PM +0100, Dominic Raferd wrote:
> Sorry I am not a Samba technical expert, but I believe there is a
> new and quite severe bug for Samba 4.1.7+ introduced by bug fix
> 10422. Although intended to cope with max xmit > 64kb it is having
> unintended negative consequences for legacy client machines using
> DOS.
> This message appears hundreds of thousands of times in logs (even
> with log level 0), and file accesses are slow slow slow:
>   reply_read: requested read size (1024) is greater than maximum
> allowed (972/1024). Returning short read of maximum allowed for
> compatibility with Windows 2000.
> The problem seems to be that samba has max_send is 972 and the new
> bugfix code therefore blocks a *read* size of 1024. However the
> connections for these clients always worked perfectly before with
> the old test (which was against *max_recv* instead of max_send)
> (e.g. with Samba 4.1.5).
> The protocol my DOS clients are using is what Samba calls 'LANMAN2'
> (Microsoft Networking).
> I have tried different smb.conf settings (max xmit, socket options
> SO_SNDBUG and SO_RCVBUF) and also varied settings on the DOS
> clients, all to no avail. My conclusion is that Samba 4.1.7+ is
> broken, or at least badly wounded, for these clients.
> I would be very grateful if it could be fixed!

Can you send a network trace of such a client? Please
include the start of the connection. Please see



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