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

[John Ferlan]

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 at redhat.com>
> ---
>  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?


> 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...

> +        </attribute>
> +        <optional>
> +          <attribute name="append">
> +            <ref name="virOnOff"/>
> +          </attribute>
> +        </optional>
> +      </element>
> +    </optional>
>    </define>
>    <!--
>        The description for a console
> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> index 56bd1aa..92c3ce9 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -1768,6 +1768,8 @@ virDomainChrSourceDefClear(virDomainChrSourceDefPtr def)
>          VIR_FREE(def->data.spiceport.channel);
>          break;
>      }
> +
> +    VIR_FREE(def->logfile);
>  }
>  
>  /* Deep copies the contents of src into dest.  Return -1 and report
> @@ -9396,6 +9398,8 @@ virDomainChrSourceDefParseXML(virDomainChrSourceDefPtr def,
>      char *connectHost = NULL;
>      char *connectService = NULL;
>      char *path = NULL;
> +    char *logfile = NULL;
> +    char *logappend = NULL;
>      char *mode = NULL;
>      char *protocol = NULL;
>      char *channel = NULL;
> @@ -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).


> +                if (!logappend)
> +                    logappend = virXMLPropString(cur, "append");
>              } else if (xmlStrEqual(cur->name, BAD_CAST "protocol")) {
>                  if (!protocol)
>                      protocol = virXMLPropString(cur, "type");
> @@ -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)


John
> @@ -20093,6 +20112,15 @@ virDomainChrSourceDefFormat(virBufferPtr buf,
>  
>      }
>  
> +    if (def->logfile) {
> +        virBufferEscapeString(buf, "<log file='%s'", def->logfile);
> +        if (def->logappend != VIR_TRISTATE_SWITCH_ABSENT) {
> +            virBufferAsprintf(buf, " append='%s'",
> +                              virTristateSwitchTypeToString(def->logappend));
> +        }
> +        virBufferAddLit(buf, "/>\n");
> +    }
> +
>      return 0;
>  }
>  
> diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
> index 1de3be3..2b2f75b 100644
> --- a/src/conf/domain_conf.h
> +++ b/src/conf/domain_conf.h
> @@ -1204,6 +1204,8 @@ struct _virDomainChrSourceDef {
>              char *channel;
>          } spiceport;
>      } data;
> +    char *logfile;
> +    int logappend;
>  };
>  
>  /* A complete character device, both host and domain views.  */
>