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support tap devices in qemu backend

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The motivation for this is networking out (in particular, testing NFS
support) from the VM.

We could be a lot more user friendly (a la libvirt) by creating the tap
device for users and allowing them to specify a bridge instead, but then
we'd need root to create this tap device. For now, let's make people do
their own tap devices, and just use them. A tap device can be created for a
bridge as follows:

    # ip tuntap add linuxkit0 mode tap user `whoami`
    # ip link set linuxkit0 up
    # ip link set linuxkit0 master $bridge_name

and then used by:

    $ ./bin/linuxkit run qemu -tap-device linuxkit0 linuxkit

Signed-off-by: Tycho Andersen <tycho@docker.com>
This commit is contained in:
Tycho Andersen 2017-07-20 12:36:07 -06:00
parent c76096e4d5
commit d237c92273
1 changed files with 9 additions and 0 deletions
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9
src/cmd/linuxkit/run_qemu.go
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@ -35,6 +35,7 @@ type QemuConfig struct {
QemuBinPath string QemuBinPath string
QemuImgPath string QemuImgPath string
PublishedPorts []string PublishedPorts []string
TapDevice string
} }
func haveKVM() bool { func haveKVM() bool {
@ -96,6 +97,7 @@ func runQemu(args []string) {
publishFlags := multipleFlag{} publishFlags := multipleFlag{}
flags.Var(&publishFlags, "publish", "Publish a vm's port(s) to the host (default [])") flags.Var(&publishFlags, "publish", "Publish a vm's port(s) to the host (default [])")
tapDevice := flags.String("tap-device", "", "Tap device to use as eth0 (optional)")
if err := flags.Parse(args); err != nil { if err := flags.Parse(args); err != nil {
log.Fatal("Unable to parse args") log.Fatal("Unable to parse args")
@ -215,6 +217,7 @@ func runQemu(args []string) {
KVM: *enableKVM, KVM: *enableKVM,
Containerized: *qemuContainerized, Containerized: *qemuContainerized,
PublishedPorts: publishFlags, PublishedPorts: publishFlags,
TapDevice: *tapDevice,
} }
config = discoverBackend(config) config = discoverBackend(config)
@ -447,6 +450,12 @@ func buildQemuCmdline(config QemuConfig) (QemuConfig, []string) {
qemuArgs = append(qemuArgs, "-net", "nic") qemuArgs = append(qemuArgs, "-net", "nic")
} }
if config.TapDevice != "" {
qemuArgs = append(qemuArgs, "-net", "nic,model=virtio")
tapArg := fmt.Sprintf("tap,ifname=%s,script=no,downscript=no", config.TapDevice)
qemuArgs = append(qemuArgs, "-net", tapArg)
}
if config.GUI != true { if config.GUI != true {
qemuArgs = append(qemuArgs, "-nographic") qemuArgs = append(qemuArgs, "-nographic")
} }