[libvirt] [PATCH] virsh: add transient interfaces check for iface-unbridge

[Michal Privoznik]

On 17.12.2014 11:34, Lin Ma wrote:
> iface-unbridge(netcf interface backend) checks multiple interfaces
> attaching based on static configuration.
> If guests interfaces(says tun/tap devices) are attaching to the bridge,
> iface-unbridge doesn't check them, It causes the bridge is removed
> although it's in use by other guests.
>
> Please refer to:
> https://bugzilla.suse.com/show_bug.cgi?id=813117

The bug is not publicly viewable. We tend to not put the BZ URL in the 
commit message in that case.

>
> Signed-off-by: Lin Ma <lma at suse.com>
> ---
>   tools/virsh-interface.c | 24 +++++++++++++++++++++---
>   1 file changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/tools/virsh-interface.c b/tools/virsh-interface.c
> index 5f848b6..63ba5bb 100644
> --- a/tools/virsh-interface.c
> +++ b/tools/virsh-interface.c
> @@ -1040,11 +1040,11 @@ cmdInterfaceUnbridge(vshControl *ctl, const vshCmd *cmd)
>       const char *br_name;
>       char *if_type = NULL, *if_name = NULL;
>       bool nostart = false;
> -    char *br_xml = NULL;
> +    char *br_xml = NULL, *br_xml_transient_if = NULL;
>       xmlChar *if_xml = NULL;
>       int if_xml_size;
> -    xmlDocPtr xml_doc = NULL;
> -    xmlXPathContextPtr ctxt = NULL;
> +    xmlDocPtr xml_doc = NULL, xml_doc_transient_if = NULL;
> +    xmlXPathContextPtr ctxt = NULL, ctxt_transient_if = NULL;
>       xmlNodePtr top_node, if_node, cur;
>
>       /* Get a handle to the original device */
> @@ -1103,6 +1103,21 @@ cmdInterfaceUnbridge(vshControl *ctl, const vshCmd *cmd)
>           goto cleanup;
>       }
>
> +    /* verify whether there is any transient interface attached to bridge. */
> +    if (!(br_xml_transient_if = virInterfaceGetXMLDesc(br_handle, 0)))
> +        goto cleanup;
> +    if (!(xml_doc_transient_if = virXMLParseStringCtxt(br_xml_transient_if,
> +                                          _("(bridge interface definition)"),
> +                                          &ctxt_transient_if))) {
> +        vshError(ctl, _("Failed to parse configuration of %s"), br_name);
> +        goto cleanup;
> +    }
> +
> +    if (virXPathNode("./bridge/interface[2]", ctxt_transient_if) != NULL) {
> +        vshError(ctl, "%s", _("The bridge is in use by transient interfaces"));
> +        goto cleanup;
> +    }
> +

This effectively copies the code just a few lines above (not to be seen 
in this context though). The only difference is, that your code gest 
LIVE bridge XML, while pre-exisitng code dumps INACTIVE XML. Can we turn 
already existing code into checking LIVE XML instead? It feels more 
appropriate too. Live bridge can have only one interface plugged in (due 
to hot-unplugging) regardless of what INACTIVE XML says.

Michal