[libvirt] [Xen-devel] [PATCH v2] libxl: free ifname on libxlDomainMigrationPrepareDef
Joao Martins
joao.m.martins at oracle.com
Sun Dec 6 23:27:32 UTC 2015
On 12/06/2015 06:11 PM, Jim Fehlig wrote:
> On 12/06/2015 10:59 AM, Jim Fehlig wrote:
>> On 12/06/2015 10:04 AM, Jim Fehlig wrote:
>>> On 12/04/2015 12:45 PM, Joao Martins wrote:
>>>> Commit d2e5538b1 changes virDomainDef to include ifnames
>>>> that autogenerated by libxl, and that are also cleared
>>>> on domain cleanup. One place that's missing is on
>>>> migration, when domain xml is sent to dst libvirtd and
>>>> would contain ifnames from the source libvirtd. This
>>>> would lead to erronous behaviour (as seen in osstest CI)
>>>> such as failing to migrate when a vif with the same name
>>>> existed (belonging to another domain) on destination.
>>> Your patch is certainly one way to fix this issue, but I wonder if we should be
>>> adding the generated ifname to the XML that is sent to the destination.
>>> virDomainNetDefFormat() has this interesting piece of logic
>>>
>>> if (def->ifname &&
>>> !((flags & VIR_DOMAIN_DEF_FORMAT_INACTIVE) &&
>>> (STRPREFIX(def->ifname, VIR_NET_GENERATED_PREFIX)))) {
>>> /* Skip auto-generated target names for inactive config. */
>>> virBufferEscapeString(buf, "<target dev='%s'/>\n", def->ifname);
>>> }
>>>
>>> In the Begin phase, we format the XML that will be sent to the destination based
>>> on current vm->def of the machine running on the source. Calling
>>> virDomainDefFormat() with VIR_DOMAIN_DEF_FORMAT_INACTIVE doesn't seem right. I
>>> tried to see how this is handled in the qemu driver, but couldn't quite figure
>>> it out. Jirka is one of the experts of the qemu migration code, adding him to cc
>>> to see if he has any insights.
>> I think this is actually handled on the destination when parsing the incoming
>> XML in the Prepare phase. Something like the below patch may be a better solution.
>
> Sorry for spamming with all the self-replies...
>
>> >From 8556bf5a116edf5989eac40f0a90feed6c003b38 Mon Sep 17 00:00:00 2001
>> From: Jim Fehlig <jfehlig at suse.com>
>> Date: Sun, 6 Dec 2015 10:46:28 -0700
>> Subject: [PATCH] conf: add net device prefix for Xen
>>
>> Commit d2e5538b1 changes virDomainDef to include ifnames autogenerated
>> by libxl. When migrating a domain, the autogenerated name is included
>> in the XML sent to the destination host. This would lead to erronous
>> behaviour (as seen in osstest CI) such as failing to migrate when
>> a vif with the same name existed (belonging to another domain) on
>> destination.
>>
>> This patch defines another VIR_NET_GENERATED_PREFIX for Xen allowing
>> the autogenerated names to be excluded when parsing and formatting
>> inactive config.
>>
>> Signed-off-by: Jim Fehlig <jfehlig at suse.com>
>> ---
>> src/conf/domain_conf.c | 6 ++++--
>> src/conf/domain_conf.h | 4 ++++
>> 2 files changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
>> index 2f5c0ed..debcf4e 100644
>> --- a/src/conf/domain_conf.c
>> +++ b/src/conf/domain_conf.c
>> @@ -8428,7 +8428,8 @@ virDomainNetDefParseXML(virDomainXMLOptionPtr xmlopt,
>> ifname = virXMLPropString(cur, "dev");
>> if (ifname &&
>> (flags & VIR_DOMAIN_DEF_PARSE_INACTIVE) &&
>> - STRPREFIX(ifname, VIR_NET_GENERATED_PREFIX)) {
>> + (STRPREFIX(ifname, VIR_NET_GENERATED_PREFIX) ||
>> + STRPREFIX(ifname, VIR_NET_GENERATED_PREFIX_XEN))) {
>> /* An auto-generated target name, blank it out */
>> VIR_FREE(ifname);
>> }
>> @@ -19790,7 +19791,8 @@ virDomainNetDefFormat(virBufferPtr buf,
>> virBufferEscapeString(buf, "<backenddomain name='%s'/>\n", def->domain_name);
>> if (def->ifname &&
>> !((flags & VIR_DOMAIN_DEF_FORMAT_INACTIVE) &&
>> - (STRPREFIX(def->ifname, VIR_NET_GENERATED_PREFIX)))) {
>> + (STRPREFIX(def->ifname, VIR_NET_GENERATED_PREFIX) ||
>> + STRPREFIX(def->ifname, VIR_NET_GENERATED_PREFIX_XEN)))) {
>> /* Skip auto-generated target names for inactive config. */
>> virBufferEscapeString(buf, "<target dev='%s'/>\n", def->ifname);
>> }
>> diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
>> index 90d8e13..d2cc26f 100644
>> --- a/src/conf/domain_conf.h
>> +++ b/src/conf/domain_conf.h
>> @@ -1085,6 +1085,10 @@ struct _virDomainNetDef {
>> * by libvirt, and cannot be used for a persistent network name. */
>> # define VIR_NET_GENERATED_PREFIX "vnet"
>>
>> +/* Used for prefix of ifname of any network name generated dynamically
>> + * by libvirt for Xen, and cannot be used for a persistent network name. */
>> +# define VIR_NET_GENERATED_PREFIX_XEN "vif"
>> +
>> typedef enum {
>> VIR_DOMAIN_CHR_DEVICE_STATE_DEFAULT = 0,
>> VIR_DOMAIN_CHR_DEVICE_STATE_CONNECTED,
>
> If this is acceptable, the below diff should be squashed in to use the #define
> instead of hardcoded "vif" in the libxl driver.
>
Wasn't aware that virDomainNetDefParseXML took care of removing ifnames already
in Prepare phase. If so, your solution appears to be a better approach indeed.
Regards,
Joao
> Regards,
> Jim
>
> diff --git a/src/libxl/libxl_domain.c b/src/libxl/libxl_domain.c
> index ef92974..c5d84a4 100644
> --- a/src/libxl/libxl_domain.c
> +++ b/src/libxl/libxl_domain.c
> @@ -734,7 +734,7 @@ libxlDomainCleanup(libxlDriverPrivatePtr driver,
> for (i = 0; i < vm->def->nnets; i++) {
> virDomainNetDefPtr net = vm->def->nets[i];
>
> - if (STRPREFIX(net->ifname, "vif"))
> + if (STRPREFIX(net->ifname, VIR_NET_GENERATED_PREFIX_XEN))
> VIR_FREE(net->ifname);
> }
> }
> @@ -918,7 +918,8 @@ libxlDomainCreateIfaceNames(virDomainDefPtr def,
> libxl_domain_config *d_config)
> if (net->ifname)
> continue;
>
> - ignore_value(virAsprintf(&net->ifname, "vif%d.%d%s",
> + ignore_value(virAsprintf(&net->ifname,
> + VIR_NET_GENERATED_PREFIX_XEN "%d.%d%s",
> def->id, x_nic->devid, suffix));
> }
> }
>
>
>
>
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