[PATCH] kvm tools: Allow the user to pass a FD to use as a TAP device

[PATCH] kvm tools: Allow the user to pass a FD to use as a TAP device

[Sasha Levin]

This allows users to pass a pre-configured fd to use for the network
interface.

For example:
        kvm run -n mode=tap,fd=3 3<>/dev/net/tap3

Cc: Daniel P. Berrange <berrange@redhat.com>
Cc: Osier Yang <jyang@redhat.com>
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 tools/kvm/builtin-run.c            |    2 ++
 tools/kvm/include/kvm/virtio-net.h |    1 +
 tools/kvm/virtio/net.c             |    6 ++++++
 3 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/tools/kvm/builtin-run.c b/tools/kvm/builtin-run.c
index 9148d83..924ae80 100644
--- a/tools/kvm/builtin-run.c
+++ b/tools/kvm/builtin-run.c
@@ -220,6 +220,8 @@ static int set_net_param(struct virtio_net_params *p, const char *param,
 		p->host_ip = strdup(val);
 	} else if (strcmp(param, "vhost") == 0) {
 		p->vhost = atoi(val);
+	} else if (strcmp(param, "fd") == 0) {
+		p->fd = atoi(val);
 	}
 
 	return 0;
diff --git a/tools/kvm/include/kvm/virtio-net.h b/tools/kvm/include/kvm/virtio-net.h
index dade8cb..a3219b6 100644
--- a/tools/kvm/include/kvm/virtio-net.h
+++ b/tools/kvm/include/kvm/virtio-net.h
@@ -12,6 +12,7 @@ struct virtio_net_params {
 	struct kvm *kvm;
 	int mode;
 	int vhost;
+	int fd;
 };
 
 void virtio_net__init(const struct virtio_net_params *params);
diff --git a/tools/kvm/virtio/net.c b/tools/kvm/virtio/net.c
index 3fb5054..9b93c5d 100644
--- a/tools/kvm/virtio/net.c
+++ b/tools/kvm/virtio/net.c
@@ -178,6 +178,12 @@ static bool virtio_net__tap_init(const struct virtio_net_params *params,
 	struct sockaddr_in sin = {0};
 	struct ifreq ifr;
 
+	/* Did the user already gave us the FD? */
+	if (params->fd) {
+		ndev->tap_fd = params->fd;
+		return 1;
+	}
+
 	ndev->tap_fd = open("/dev/net/tun", O_RDWR);
 	if (ndev->tap_fd < 0) {
 		pr_warning("Unable to open /dev/net/tun");
-- 
1.7.8

Re: [PATCH] kvm tools: Allow the user to pass a FD to use as a TAP device

[Pekka Enberg]

On Wed, Dec 7, 2011 at 11:37 AM, Sasha Levin <levinsasha928@gmail.com> wrote:
> This allows users to pass a pre-configured fd to use for the network
> interface.
>
> For example:
>        kvm run -n mode=tap,fd=3 3<>/dev/net/tap3
>
> Cc: Daniel P. Berrange <berrange@redhat.com>
> Cc: Osier Yang <jyang@redhat.com>
> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>

Daniel, Osier, I assume this is useful for libvirt?

Re: [PATCH] kvm tools: Allow the user to pass a FD to use as a TAP device

[Daniel P. Berrange]

On Wed, Dec 07, 2011 at 06:28:12PM +0200, Pekka Enberg wrote:
> On Wed, Dec 7, 2011 at 11:37 AM, Sasha Levin <levinsasha928@gmail.com> wrote:
> > This allows users to pass a pre-configured fd to use for the network
> > interface.
> >
> > For example:
> >        kvm run -n mode=tap,fd=3 3<>/dev/net/tap3
> >
> > Cc: Daniel P. Berrange <berrange@redhat.com>
> > Cc: Osier Yang <jyang@redhat.com>
> > Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
> 
> Daniel, Osier, I assume this is useful for libvirt?

Yes, this works.

I don't know if kvmtool supports  the VNET_HDR extension yet, but if it
does, then we can make libvirt pass in a pre-opened FD for that too.


Daniel
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Re: [PATCH] kvm tools: Allow the user to pass a FD to use as a TAP device

[Pekka Enberg]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 602 bytes --]

On Wed, 7 Dec 2011, Daniel P. Berrange wrote:

> On Wed, Dec 07, 2011 at 06:28:12PM +0200, Pekka Enberg wrote:
>> On Wed, Dec 7, 2011 at 11:37 AM, Sasha Levin <levinsasha928@gmail.com> wrote:
>>> This allows users to pass a pre-configured fd to use for the network
>>> interface.
>>>
>>> For example:
>>>        kvm run -n mode=tap,fd=3 3<>/dev/net/tap3
>>>
>>> Cc: Daniel P. Berrange <berrange@redhat.com>
>>> Cc: Osier Yang <jyang@redhat.com>
>>> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
>>
>> Daniel, Osier, I assume this is useful for libvirt?
>
> Yes, this works.

Applied, thanks!

Re: [PATCH] kvm tools: Allow the user to pass a FD to use as a TAP device

[Osier Yang]

On 2011年12月08日 01:24, Pekka Enberg wrote:
> On Wed, 7 Dec 2011, Daniel P. Berrange wrote:
>
>> On Wed, Dec 07, 2011 at 06:28:12PM +0200, Pekka Enberg wrote:
>>> On Wed, Dec 7, 2011 at 11:37 AM, Sasha Levin
>>> <levinsasha928@gmail.com> wrote:
>>>> This allows users to pass a pre-configured fd to use for the network
>>>> interface.
>>>>
>>>> For example:
>>>>        kvm run -n mode=tap,fd=3 3<>/dev/net/tap3
>>>>
>>>> Cc: Daniel P. Berrange <berrange@redhat.com>
>>>> Cc: Osier Yang <jyang@redhat.com>
>>>> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
>>>
>>> Daniel, Osier, I assume this is useful for libvirt?
>>
>> Yes, this works.
>
> Applied, thanks!

/me late to see the news. :)

I'm going to update the codes to support that.

Regards,
Osier