Re: [PATCH] macvlan: Introduce 'passthru' mode to takeover the underlying device
From: Sridhar Samudrala s...@us.ibm.com Date: Thu, 28 Oct 2010 16:10:50 -0700 With the current default 'vepa' mode, a KVM guest using virtio with macvtap backend has the following limitations. - cannot change/add a mac address on the guest virtio-net - cannot create a vlan device on the guest virtio-net - cannot enable promiscuous mode on guest virtio-net To address these limitations, this patch introduces a new mode called 'passthru' when creating a macvlan device which allows takeover of the underlying device and passing it to a guest using virtio with macvtap backend. Only one macvlan device is allowed in passthru mode and it inherits the mac address from the underlying device and sets it in promiscuous mode to receive and forward all the packets. Signed-off-by: Sridhar Samudrala s...@us.ibm.com Applied, thanks Sridhar. -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] macvlan: Introduce 'passthru' mode to takeover the underlying device
On 10/29/2010 6:45 AM, Arnd Bergmann wrote: On Friday 29 October 2010, Sridhar Samudrala wrote: With the current default 'vepa' mode, a KVM guest using virtio with macvtap backend has the following limitations. - cannot change/add a mac address on the guest virtio-net I believe this could be changed if there is a neeed, but I actually consider it one of the design points of macvlan that the guest is not able to change the mac address. With 802.1Qbg you rely on the switch being able to identify the guest by its MAC address, which the host kernel must ensure. Currently the host cannot prevent a guest user from trying to change/add a mac address on the guest virtio-net. From guest point of view, the request succeeds, but the incoming packets are dropped siliently by the host interface. - cannot create a vlan device on the guest virtio-net Why not? If this doesn't work, it's probably a bug! Because the host is not aware of the guest vlan tag and the host external interface will filter out incoming vlan tagged packets. Why does the passthru mode enable it if it doesn't work already? passthru mode puts the host external interface in promiscuous mode which allows vlan tagged packets to be received. Even in tap/bridge mode, this works because adding an external interface to the bridge causes it to be put in promiscuous mode. Thanks Sridhar -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] macvlan: Introduce 'passthru' mode to takeover the underlying device
On Fri, Oct 29, 2010 at 03:45:17PM +0200, Arnd Bergmann wrote: On Friday 29 October 2010, Sridhar Samudrala wrote: With the current default 'vepa' mode, a KVM guest using virtio with macvtap backend has the following limitations. - cannot change/add a mac address on the guest virtio-net I believe this could be changed if there is a neeed, but I actually consider it one of the design points of macvlan that the guest is not able to change the mac address. With 802.1Qbg you rely on the switch being able to identify the guest by its MAC address, which the host kernel must ensure. - cannot create a vlan device on the guest virtio-net Why not? If this doesn't work, it's probably a bug! Why does the passthru mode enable it if it doesn't work already? - cannot enable promiscuous mode on guest virtio-net Could you elaborate why such a setup would be useful? Arnd E.g. to support bridging in the guest. -- MST -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] macvlan: Introduce 'passthru' mode to takeover the underlying device
On Fri, Oct 29, 2010 at 03:45:17PM +0200, Arnd Bergmann wrote: On Friday 29 October 2010, Sridhar Samudrala wrote: With the current default 'vepa' mode, a KVM guest using virtio with macvtap backend has the following limitations. - cannot change/add a mac address on the guest virtio-net I believe this could be changed if there is a neeed, but I actually consider it one of the design points of macvlan that the guest is not able to change the mac address. It's a policy question that we should not set at the kernel level. With 802.1Qbg you rely on the switch being able to identify the guest by its MAC address, which the host kernel must ensure. This is required to be able to get feature parity with both tun and device assignment. At the moment, changing the mac when using macvtap silently breaks guest networking. -- MST -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] macvlan: Introduce 'passthru' mode to takeover the underlying device
On Friday 29 October 2010, Sridhar Samudrala wrote: With the current default 'vepa' mode, a KVM guest using virtio with macvtap backend has the following limitations. - cannot change/add a mac address on the guest virtio-net I believe this could be changed if there is a neeed, but I actually consider it one of the design points of macvlan that the guest is not able to change the mac address. With 802.1Qbg you rely on the switch being able to identify the guest by its MAC address, which the host kernel must ensure. - cannot create a vlan device on the guest virtio-net Why not? If this doesn't work, it's probably a bug! Why does the passthru mode enable it if it doesn't work already? - cannot enable promiscuous mode on guest virtio-net Could you elaborate why such a setup would be useful? Arnd -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
