Re: XSA-180 follow-up: repurpose xenconsoled for logging

From: Doug Goldstein <cardoe@cardoe.com>
To: George Dunlap <george.dunlap@citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Wei Liu <wei.liu2@citrix.com>,
	Xen-devel <xen-devel@lists.xenproject.org>
Cc: George Dunlap <george.dunlap@eu.citrix.com>,
	Ian Jackson <Ian.Jackson@eu.citrix.com>
Subject: Re: XSA-180 follow-up: repurpose xenconsoled for logging
Date: Mon, 6 Jun 2016 15:47:37 -0500	[thread overview]
Message-ID: <3a114c2e-198d-4ac3-5e9a-e1d1b63a056b@cardoe.com> (raw)
In-Reply-To: <57554C87.3040001@citrix.com>

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On 6/6/16 5:12 AM, George Dunlap wrote:
> On 03/06/16 18:38, Andrew Cooper wrote:
>> On 01/06/16 15:00, Wei Liu wrote:
>>> Hi all
>>>

<snip>

> FWIW, the libvirt project has exactly the same problem, and they did the
> analog of what Wei is proposing -- they added a new daemon, virtlogd, to
> handle all the console and debug log rotation in a fashion resistant to
> DoSing.  Without reading their discussion, it's reasonable to assume
> that using system logging was at least considered using system-level
> logging before deciding to write their own code.

If I recall they use RPCs and the logs are generated as a best effort to
not block QEMU.

> 
> We already have a daemon to do logging of consoles; it just doesn't have
> any of the logrotate features that are needed to make it robust against
> DoS.  There's no sense in having log rotation code in two places, so
> upgrading xenconsoled to do what virtlogd is doing makes more sense than
> say, either writing our own, or stealing virtlogd.

What if we made xl / libxl really good at the limited scope of things it
should be good at and left the other bits to others. At this point it
seems like yet another feature that xl / libxl is gaining that matches
what libvirt does. Maybe an approach is something you appear to suggest
and just point people to virtlogd and ask the libvirt guys if they would
make it a separate package. Honestly it seems like xl could slim down
from a feature set perspective and focus on improving libxl / libvirt
interaction. That's something that the Xen community has been interested
in to better support OpenStack anyway.

Just my 2 cents.

-- 
Doug Goldstein

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