[Libguestfs] [nbdkit PATCH 3/7] RFC: protocol: Only send EOVERFLOW when valid

[Eric Blake]

On 4/23/19 7:38 AM, Eric Blake wrote:
> [adding NBD list]
> 
> On 4/23/19 2:36 AM, Richard W.M. Jones wrote:
>> On Mon, Apr 22, 2019 at 07:50:22PM -0500, Eric Blake wrote:
>>> Previously, we were squashing EOVERFLOW into EINVAL; continue to do so
>>> at points in the protocol where the client may not be expecting
>>> EOVERFLOW.
> 
>>
>> The protocol spec is unclear on whether EOVERFLOW can be returned in
>> cases other than the DF flag being set.  Whether we include this patch
>> or not seems to hinge on the interpretation of the protocol spec which
>> I'm not really in a position to make.

...

> 
> So the question at hand is whether I should patch the NBD spec to
> recommend that a server SHOULD NOT send EOVERFLOW except in response to
> NBD_CMD_READ when the NBD_CMD_FLAG_DF bit is set (similar to my proposed
> wording that a server SHOULD NOT send ENOTSUP except in response to
> NBD_CMD_FLAG_FAST_ZERO).

As I have now pushed my proposed changes to the NBD spec to clarify
this, I am also pushing the nbdkit patch to handle EOVERFLOW only when
NBD_CMD_FLAG_DF is in use.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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