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Re: [Qemu-devel] [PATCH v9 04/17] vnc: hoist allocation of VncBasicInfo
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH v9 04/17] vnc: hoist allocation of VncBasicInfo to callers |
Date: |
Fri, 23 Oct 2015 15:13:16 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) |
"Daniel P. Berrange" <address@hidden> writes:
> On Tue, Oct 20, 2015 at 04:53:24PM -0600, Eric Blake wrote:
>> On 10/20/2015 08:46 AM, Markus Armbruster wrote:
>> > Gerd Hoffmann <address@hidden> writes:
>> >
>> >> Hi,
>> >>
>> >>>> -static VncBasicInfo *vnc_basic_info_get(struct sockaddr_storage *sa,
>> >>>> - socklen_t salen)
>> >>>> +static void vnc_basic_info_get(struct sockaddr_storage *sa,
>> >>>> + socklen_t salen,
>> >>>> + VncBasicInfo *info,
>> >>>> + Error **errp)
>> >>
>> >>> The function no longer "gets info", it merely initializes it. Rename it
>> >>> accordingly? Gerd?
>> >>
>> >> vnc_fill_basic_info maybe?
>> >
>> > Fine with me. Could also call it _init_ instead of _fill_.
>>
>> I like init a bit better than fill.
>>
>> >
>> >>> Outside this patch's scope, but since I'm looking at the code already...
>>
>> I'm guessing that also means that fixing it is outside this series' scope.
>>
>> >>> When vnc_server_info_get() fails, the event is dropped. Why is that
>> >>> okay? Failure seems unlikely, though.
>> >>
>> >> Suggestions what else to do? I don't wanna crash qemu by calling
>> >> qapi_event_send_vnc_* with a NULL pointer. And, yes, it should be
>> >> highly unlikely so trying some more sophisticated error handling would
>> >> probably be dead code ...
>> >
>> > These events signal a state change. Dropping them make me feel uneasy,
>> > because if a client uses them to track state, it gets out of sync.
>>
>> Events are already best-effort; clients have to be prepared to miss an
>> event - but that's mainly when reconnecting (such as across libvirtd
>> restarts), and not while the monitor is reliably connected.
>>
>> > The events need to identify the server to be of any use for state
>> > tracking. Currently, this is members host, service, family of data
>> > member server.
>> >
>> > We could avoid failures in vnc_qmp_event() as follows:
>> >
>> > 1. When we create a server, we obtain its info with getsockname() and
>> > getnameinfo(). If they fail, we fail server creation. Else, we
>> > store the info for vnc_qmp_event().
>> >
>> > 2. When a client connects, we obtain its info with getpeername() and
>> > getnameinfo(). If they fail, we refuse the connection. Else, we
>> > store the infor for vnc_qmp_event().
>>
>> Seems reasonable to me, but starts to be out of scope for what I'm
>> currently tackling, so is this something I can hand to you, Gerd?
>
> My pending IO channel patches do exactly this
>
> Take a look at the QIOChannelSocket impl
>
> https://lists.gnu.org/archive/html/qemu-devel/2015-10/msg03440.html
>
> This caches the results of getpeername & getsockname in the
> QOIChannelSocket object.
>
> So my patches which convert VNC to use QIOChannelSOcket should solve
> this particular failure scenario you're discussing.
Great! No need to add a FIXME comment then.
- [Qemu-devel] [PATCH v9 00/17] qapi collision reduction (post-introspection subset B'), Eric Blake, 2015/10/16
- [Qemu-devel] [PATCH v9 04/17] vnc: hoist allocation of VncBasicInfo to callers, Eric Blake, 2015/10/16
- Re: [Qemu-devel] [PATCH v9 04/17] vnc: hoist allocation of VncBasicInfo to callers, Markus Armbruster, 2015/10/20
- Re: [Qemu-devel] [PATCH v9 04/17] vnc: hoist allocation of VncBasicInfo to callers, Gerd Hoffmann, 2015/10/20
- Re: [Qemu-devel] [PATCH v9 04/17] vnc: hoist allocation of VncBasicInfo to callers, Markus Armbruster, 2015/10/20
- Re: [Qemu-devel] [PATCH v9 04/17] vnc: hoist allocation of VncBasicInfo to callers, Eric Blake, 2015/10/20
- Re: [Qemu-devel] [PATCH v9 04/17] vnc: hoist allocation of VncBasicInfo to callers, Markus Armbruster, 2015/10/21
- Re: [Qemu-devel] [PATCH v9 04/17] vnc: hoist allocation of VncBasicInfo to callers, Daniel P. Berrange, 2015/10/21
- Re: [Qemu-devel] [PATCH v9 04/17] vnc: hoist allocation of VncBasicInfo to callers,
Markus Armbruster <=
- Re: [Qemu-devel] [PATCH v9 04/17] vnc: hoist allocation of VncBasicInfo to callers, Eric Blake, 2015/10/20
[Qemu-devel] [PATCH v9 10/17] nbd: Convert to new qapi union layout, Eric Blake, 2015/10/16
[Qemu-devel] [PATCH v9 01/17] qapi: Add tests for reserved name abuse, Eric Blake, 2015/10/16
[Qemu-devel] [PATCH v9 08/17] tests: Convert to new qapi union layout, Eric Blake, 2015/10/16