Re: [Qemu-devel] [PATCH v8 1/2] block/vxhs.c: Add support for a new block device type called "vxhs"

[Daniel P. Berrange]

On Tue, Mar 07, 2017 at 05:27:55PM -0800, ashish mittal wrote:
> Thanks! There is one more input I need some help with!
> 
> VxHS network library opens a fixed number of connection channels to a
> given host, and all the vdisks (that connect to the same host) share
> these connection channels.
> 
> Therefore, we need to open secure channels to a specific target host
> only once for the first vdisk that connects to that host. All the
> other vdisks that connect to the same target host will share the same
> set of secure communication channels.
> 
> I hope the above scheme is acceptable?
> 
> If yes, then we have a couple of options to implement this:
> 
> (1) Accept the TLS credentials per vdisk using the previously
> discussed --object tls-creds-x509 mechanism. In this case, if more
> than one vdisk have the same host info, then we will use only the
> first one's creds to set up the secure connection, and ignore the
> others. vdisks that connect to different target hosts will use their
> individual tls-creds-x509 to set up the secure channels. This is, of
> course, not relevant for qemu-img/qemu-io as they can open only one
> vdisk at a time.

It looks like option 1 here is the way to go. Just report an error if
there are multiple creds provided for the same host and they don't
match.

> 
> (2) Instead of having a per-vdisk --object tls-creds-x509, have a
> single such argument on the command line for vxhs block device code to
> consume - if that is possible! One way to achieve this could be the
> user/password authentication we discussed earlier, which we could use
> to pass the directory where cert/keys are kept.
> 
> (3) Use the instance UUID, when available, to lookup the cert files
> per instance (i.e. for qemu-kvm), and use the --object tls-creds-x509
> mechanism, when instance UUID is NULL (i.e. qemu-io, qemu-img etc).
> The cert/key files are anyway protected by file permissions in either
> case, so I guess there is no additional security provided by either
> method.

Regards,
Daniel
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