Re: [Qemu-devel] [PATCH] Add HTTP protocol using curl v2

[Kevin Wolf <kwolf@redhat.com>]

Daniel P. Berrange schrieb:
> On Wed, May 06, 2009 at 03:00:50AM +0200, alex@csgraf.de wrote:
>> From: Alexander Graf <alex@csgraf.de>
>>
>> Currently Qemu can read from posix I/O and NBD. This patch adds a
>> third protocol to the game: HTTP.
>>
>> In certain situations it can be useful to access HTTP data directly,
>> for example if you want to try out an http provided OS image, but
>> don't know if you want to download it yet.
>>
>> Using this patch you can now try it on on the fly. Just use it like:
>>
>> qemu -cdrom http://host/path/my.iso
> 
> I rather think there should be an explicit flag to allow use of http://
> URLs in filenames at runtime, not just 'configure' time. There are many
> apps out there using QEMU which will be assuming QEMU treats all disk
> paths as local files, and thus not got explicit code to check whether 
> a URI is passed. I could well see that some will consider it a security
> issue to allow QEMU to download off the net, but if they updated to
> a new QEMU with this patch, downloading would be allowed by default.

If apps want to be sure that they are accessing a local file, they must
ensure not to have a colon in the file name. Otherwise this specifies a
protocol for the qemu block layer.

Btw, we could use a way to escape colons in a file name. Using such
files isn't possible currently.

> Perhaps only enable these remote URIs with the -drive parameter, when
> an explicit fmt=http option is set. But can this be layered into the
> other protocols, eg could the remote URI be in qcow, vmdk, etc formats,
> or are you assuming the remote uri is raw file ?

It should work with all formats. This is why fmt=http is wrong. It's not
a format, but a protocol.

Kevin