[libvirt] [PATCH v3] Add support for Veritas HyperScale (VxHS) block device protocol

Tue Apr 11 22:47:37 UTC 2017

On 04/10/2017 07:32 PM, ashish mittal wrote:
> Hi,
> 
> I'm trying to figure out what changes are needed in the libvirt vxhs
> patch to support passing TLS X509 arguments to qemu, similar to the
> following -
> 
> Sample QEMU command line passing TLS credentials to the VxHS block
> device (run in secure mode):
> ./qemu-io --object
> tls-creds-x509,id=tls0,dir=/etc/pki/qemu/vxhs,endpoint=client -c 'read
> -v 66000 2.5k' 'json:{"server.host": "127.0.0.1", "server.port": "9999",
> "vdisk-id": "/test.raw", "driver": "vxhs", "tls-creds":"tls0"}'
> 
> I was hoping to find some NBD code related to this, but not able to
> locate it. Any pointers will be appreciated.

Well you have a couple of things to deal with... There's the creation of
the TLS object and there's altering the parameters used for the qemu
command based on your needs/model.

First off you'll need to figure out where/how you're going to define
where the TLS creds exist. For that, I suspect you'll have code similar
to how chardevTLS support was added.  Essentially some way to either use
an existing TLS environment or a way to allow someone to define a vxhs
specific environment (hint, see src/qemu/qemu_conf.c, src/qemu/qemu.conf
- I've made changes recently there too).

For the TLS object creation on the command line, see
qemuBuildTLSx509CommandLine to see how the code builds the
"tls-creds-x509,id=tls0,dir=/etc/pki/qemu/vxhs,endpoint=client" portion
of your command line.

I forget if hot plug was in your plan, but see qemuDomainGetTLSObjects,
qemuDomainAddTLSObjects, and qemuDomainDelTLSObjects for that.

The rest of the command line is going to be a bit tricky since using the
"newer" driver syntax for libvirt is "sparse". Traditionally libvirt has
used "-drive file=[$uri:]$path,format=$driver,..."  (use grep "\-drive
file" tests/*/*.args from a libvirt git directory - you can grep that
output for gluster or rbd to see the uri format).

IIUC the qemu changes correctly though, you cannot use that "file="
syntax, instead you'll need to format the command line similar to how
things were done for gluster to add multiple host support where the
syntax is "-drive 'file.driver=gluster,file.volume=..." (use grep
"\-drive file.driver" tests/*/*.args to see how this is done for gluster).

That code/support was added in a series starting at commit id '22ad4a7c'
and working your way forward through about 18 patches. Using a visual
tool like gitk helps a lot...

I think what will be easiest is to start at that commit and look "up"
for gluster specific changes.  Be careful not to fully cut-n-paste
because there have been patches since that time to fix some issues with
the initial implementation. I point it out only as a way for you to see
which modules and where "similar" code exists.

You'll also note there is an nbd patch in that series of patches - not
sure how much that helps, but it perhaps gives you some amount of
guidelines. Although I don't believe nbd was added to the command line -
it was just a way of syntax generation/testing.

John

> 
> Thanks,
> Ashish
> 
> On Wed, Feb 1, 2017 at 8:36 AM, John Ferlan <jferlan at redhat.com> wrote:
>> [...]
>> Pressed send too soon, sigh.
>>
>>
>>>>>
>>>>> #1. Based on Peter's v2 comments, we don't want to support the
>>>>> older/legacy syntax for VxHS, so it's something that should be removed -
>>>>> although we should check for it being present and fail if found.
>>>>>
>>>>
>>>> I am testing with changed code to return error if legacy syntax is
>>>> found for VxHS. Also added a test case to check for failure on legacy
>>>> syntax and it seems to pass (test #41 below).
>>>>
>>>> Then I added a pass test case to check conversion from new native
>>>> syntax to XML (test #40 below). That test fails with error
>>>> 'qemuParseCommandLineDisk:901 : internal error: missing file parameter
>>>> in drive 'file.driver=vxhs,file.vdisk-id=eb90327c-8302-4725-9e1b...'
>>>
>>> The qemu_parse_command.c changes while nice to have weren't even updated
>>> when multiple gluster servers were added (e.g. commit id '' or '7b7da9e28')
>>> Check the changes to add the new s
>>>
>>> IOW: This code knows how to parse something like:
>>>
>>> -drive
>>> 'file=gluster+unix:///Volume2/Image?socket=/path/to/sock,format=raw,if=none,id=drive-virtio-disk1'
>>>
>>> but it's clueless for:
>>>
>>> -drive file.driver=gluster,file.volume=Volume3,file.path=/Image.qcow2,\
>>> file.server.0.type=tcp,file.server.0.host=example.org,file.server.0.port=6000,\
>>> file.server.1.type=tcp,file.server.1.host=example.org,file.server.1.port=24007,\
>>> file.server.2.type=unix,file.server.2.socket=/path/to/sock,format=qcow2,\
>>> if=none,id=drive-virtio-disk2 \
>>> -device virtio-blk-pci,bus=pci.0,addr=0x5,drive=drive-virtio-disk2,\
>>> id=virtio-disk2
>>>
>>> See
>>>>
>>>> Looks like none of the existing tests in qemuargv2xmltest test for the
>>>> parsing of new syntax, and qemuParseCommandLineDisk() expects to find
>>>> 'file=' for a drive or it errors out. If this is true, will it be able
>>>> to parse the new syntax? Some help here please!
>>
>> So I wouldn't expect the VxHS code to be able to do that unless you
>> wanted to be adventurous.  The good news is that this code is primarily
>> for developers that need to take a qemu command line to generate the
>> libvirt syntax. It has not really been kept up to date with all the most
>> recent command line changes. I started to try over a year ago, but got
>> very side tracked.
>>
>>>>
>>>> Output from the newly added test cases (40 should pass and 41 checks
>>>> for error) :
>>>>
>>>> 40) QEMU ARGV-2-XML disk-drive-network-vxhs
>>>> ... Got unexpected warning from qemuParseCommandLineString:
>>>> 2017-01-28 00:57:30.814+0000: 10391: info : libvirt version: 3.0.0
>>>> 2017-01-28 00:57:30.814+0000: 10391: info : hostname: localhost.localdomain
>>>> 2017-01-28 00:57:30.814+0000: 10391: error :
>>>> qemuParseCommandLineDisk:901 : internal error: missing file parameter
>>>> in drive 'file.driver=vxhs,file.vdisk-id=eb90327c-8302-4725-9e1b-4e85ed4dc251,file.server.host=192.168.0.1,file.server.port=9999,format=raw,if=none,id=drive-virtio-disk0,cache=none'
>>>> libvirt: QEMU Driver error : internal error: missing file parameter in
>>>> drive 'file.driver=vxhs,file.vdisk-id=eb90327c-8302-4725-9e1b-4e85ed4dc251,file.server.host=192.168.0.1,file.server.port=9999,format=raw,if=none,id=drive-virtio-disk0,cache=none'
>>>> FAILED
>>>>
>>>> 41) QEMU ARGV-2-XML disk-drive-network-vxhs-fail
>>>> ... Got expected error from qemuParseCommandLineString:
>>>> libvirt: QEMU Driver error : internal error: VxHS protocol does not
>>>> support URI syntax
>>>> 'vxhs://192.168.0.1:9999/eb90327c-8302-4725-9e1b-4e85ed4dc251'
>>>> OK
>>>> 42) QEMU ARGV-2-XML disk-usb                                          ... OK
>>>>
>>>>
>>>>
>>>>> #2. Is the desire to ever support more than 1 host? If not, then is the
>>>>> "server" syntax you've borrowed from the Gluster code necessary? Could
>>>>> you just go with the single "host" like NBD and SSH. As it relates to
>>>>> the qemu command line - I'm not quite as clear. From the example I see
>>>>> in commit id '7b7da9e28', the gluster syntax would have:
>>>>>
>>>>
>>>> Present understanding is to have only one host. You are right, the
>>>> "server" part is not necessary. Will have to check with the qemu
>>>> community on this change.
>>>>
>>>>> +file.server.0.type=tcp,file.server.0.host=example.org,file.server.0.port=6000,\
>>>>> +file.server.1.type=tcp,file.server.1.host=example.org,file.server.1.port=24007,\
>>>>> +file.server.2.type=unix,file.server.2.socket=/path/to/sock,format=qcow2,\
>>>>>
>>>>> whereas, the VxHS syntax is:
>>>>>  +file.server.host=192.168.0.1,file.server.port=9999,format=raw,if=none,\
>>>>>
>>>>> FWIW: I also note there is no ".type=tcp" in your output - so perhaps
>>>>> the "default" is tcp unless otherwise specified, but I'm sure of the
>>>>> qemu syntax requirements in this area. I assume that since there's only
>>>>> 1 server, the ".0, .1, .2" become unnecessary (something added by commit
>>>>> id 'f1bbc7df4' for multiple gluster hosts).
>>>>>
>>>>
>>>> That's correct. TCP is the default.
>>>>
>>>>> I haven't closedly followed the qemu syntax discussion, but it would it
>>>>> would be possible to use:
>>>>>
>>>>> +file.host=192.168.0.1,file.port=9999
>>>>>
>>>>
>>>> That is correct. Above syntax would also work for us. I will pose this
>>>> suggestion to the qemu community and update with their response.
>>>>
>>
>> It's not that important... I was looking for a simplification and
>> generation of only what's required. You can continue using the server
>> syntax - perhaps just leave a note/comment in the code indicating the
>> decision point and move on.
>>
>> [...]
>>
>> John