Features/HelperNetworking
Summary
Introduce infrastructure to allowed QEMU network backends to be implemented outside of QEMU in a generic way.
Owner
- Name: Anthony Liguori
- Email: anthony@codemonkey.ws
- Name: Corey Bryant
- Email: coreyb@linux.vnet.ibm.com
- Name: Richa Marwaha
- Email: rmarwah@linux.vnet.ibm.com
Detailed Summary
Replace ad-hoc network backends with a single -net fd option that allows for precise control of how QEMU interacts with a given file descriptor. Then introduce external helpers that can be invoked to create appropriate file descriptors and pass them back to QEMU. These helpers can run as a higher privileged user allowing QEMU to use complex network setups while being invoked as a non-privileged user. This also allows third parties to implement user-visible network backends without having to introduce them into QEMU itself.
Network Helper
With the help of qemu_network_helper, an unprivileged user can configure the TAP interface which connects to a bridge. The helper can be invoked by using the br{bridge name} and helper{executable to configure the bridge} options in -net tap or by using -net bridge option which by default invokes br and helper options. The default helper implements the most common qemu-ifup script that can be safely given cap_net_admin.
Currently helper uses it's own ACL mechanism for access control as default,but future network helpers could be developed, for example, to support PolicyKit for access control.
Example
The following example shows how to launch Qemu instance with default as network helper
qemu-hda linux.img -net tap,br=br0,helper=/usr/local/libexec/qemu-bridge-helper
-net nic,model=virtio
qemu-hda linux.img -net bridge -net nic,model=virtio