Re: [PATCH 2/5] conf: allow use of a logfile with chardev backends

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On Fri, Feb 26, 2016 at 10:33:10AM -0500, John Ferlan wrote:
> 
> 
> On 02/23/2016 11:41 AM, Daniel P. Berrange wrote:
> > Extend the chardev source XML so that there is a new optional
> > <log/> element, which is applicable to all character device
> > backend types. For example, to log output of a TCP backed
> > serial port
> > 
> >     <serial type='tcp'>
> >       <source mode='connect' host='127.0.0.1' service='9999'/>
> >       <protocol type='raw'/>
> >       <log file='/var/log/libvirt/qemu/demo-serial0.log' append='on'/>
> >       <target port='0'/>
> >     </serial>
> > 
> > Not all hypervisors will support use of logfiles.
> > 
> > Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>
> > ---
> >  docs/schemas/domaincommon.rng | 12 ++++++++++++
> >  src/conf/domain_conf.c        | 28 ++++++++++++++++++++++++++++
> >  src/conf/domain_conf.h        |  2 ++
> >  3 files changed, 42 insertions(+)
> > 
> 
> Probably should be described in formatdomain.html.in too, right?

Yes, it should be.

> > diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
> > index 67af93a..b49d9eb 100644
> > --- a/docs/schemas/domaincommon.rng
> > +++ b/docs/schemas/domaincommon.rng
> > @@ -3276,6 +3276,18 @@
> >          </optional>
> >        </element>
> >      </optional>
> > +    <optional>
> > +      <element name="log">
> > +        <attribute name="file">
> > +          <ref name="absFilePath"/>
> 
> Although rng requires absFilePath, it's not checked during parse. I
> think what separates this from others is that it's going to be used for
> write purposes.
> 
> I see that virDomainSnapshotDefParse which seemingly can accept an file
> path as input does check if (def->file && def->file[0] == '/') to ensure
> absolute file path. I have a secondary concern about where the writing
> can occur...


> > @@ -9483,6 +9487,11 @@ virDomainChrSourceDefParseXML(virDomainChrSourceDefPtr def,
> >                      }
> >                      ctxt->node = saved_node;
> >                  }
> > +            } else if (xmlStrEqual(cur->name, BAD_CAST "log")) {
> > +                if (!logfile)
> > +                    logfile = virXMLPropString(cur, "file");
> 
> Shouldn't we validate the logfile path at least? Even virLogParseOutputs
> validates what's in logfile is at least an absFilePath. I looked forward
> to the next patch and see it's just supplied to qemu. Unlike a number of
> the absDirPath elements I looked at in domain_conf, this is a "write"
> path and I would think we want to be ultra conservative...
> 
> Secondary concern - not that it couldn't be done today w/ log_outputs
> file name in the libvirtd.conf file... What if someone supplied a name
> they shouldn't be supplying? That is somewhere they shouldn't be
> writing... Is there a way to "demand" that the value is to a specific
> path prefix?  or maybe we should just dictate providing a "name" and
> it's up to the hypervisor to prepend the hypervisor specific path (IOW:
> the /var/log/libvirt/qemu). That way someone could mount whatever they
> want at /var/log/libvirt/qemu in order to store inordinate amount of
> logs (not clogging /var unnecessarily).

The ability to define XML is considered to be equivalent to having
a root shell. We don't try to enforce rules for any of the paths
in the XML whether disk filenames, log file names or character
device backends. So this isn't causing a problem didn't already
have.

> > @@ -9641,6 +9650,16 @@ virDomainChrSourceDefParseXML(virDomainChrSourceDefPtr def,
> >          break;
> >      }
> >  
> > +    def->logfile = logfile;
> > +    logfile = NULL;
> > +
> > +    if (logappend != NULL &&
> > +        (def->logappend = virTristateSwitchTypeFromString(logappend)) <= 0) {
> > +        virReportError(VIR_ERR_INTERNAL_ERROR,
> > +                       _("Invalid append attribute value '%s'"), logappend);
> > +        goto error;
> > +    }
> > +
> >   cleanup:
> >      VIR_FREE(mode);
> >      VIR_FREE(protocol);
> 
> Need VIR_FREE(logfile) and VIR_FREE(logappend)

Ah yes.


Regards,
Daniel
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