checkpt

overlay/vhostnet/options.go

@@ -0,0 +1,70 @@
+package vhostnet
+
+import (
+	"errors"
+
+	"github.com/hetznercloud/virtio-go/tuntap"
+	"github.com/hetznercloud/virtio-go/virtqueue"
+)
+
+type optionValues struct {
+	queueSize int
+	backendFD int
+}
+
+func (o *optionValues) apply(options []Option) {
+	for _, option := range options {
+		option(o)
+	}
+}
+
+func (o *optionValues) validate() error {
+	if o.queueSize == -1 {
+		return errors.New("queue size is required")
+	}
+	if err := virtqueue.CheckQueueSize(o.queueSize); err != nil {
+		return err
+	}
+	if o.backendFD == -1 {
+		return errors.New("backend file descriptor is required")
+	}
+	return nil
+}
+
+var optionDefaults = optionValues{
+	// Required.
+	queueSize: -1,
+	// Required.
+	backendFD: -1,
+}
+
+// Option can be passed to [NewDevice] to influence device creation.
+type Option func(*optionValues)
+
+// WithQueueSize returns an [Option] that sets the size of the TX and RX queues
+// that are to be created for the device. It specifies the number of
+// entries/buffers each queue can hold. This also affects the memory
+// consumption.
+// This is required and must be an integer from 1 to 32768 that is also a power
+// of 2.
+func WithQueueSize(queueSize int) Option {
+	return func(o *optionValues) { o.queueSize = queueSize }
+}
+
+// WithBackendFD returns an [Option] that sets the file descriptor of the
+// backend that will be used for the queues of the device. The device will write
+// and read packets to/from that backend. The file descriptor can either be of a
+// RAW socket or TUN/TAP device.
+// Either this or [WithBackendDevice] is required.
+func WithBackendFD(backendFD int) Option {
+	return func(o *optionValues) { o.backendFD = backendFD }
+}
+
+// WithBackendDevice returns an [Option] that sets the given TAP device as the
+// backend that will be used for the queues of the device. The device will
+// write and read packets to/from that backend. The TAP device should have been
+// created with the [tuntap.WithVirtioNetHdr] option enabled.
+// Either this or [WithBackendFD] is required.
+func WithBackendDevice(dev *tuntap.Device) Option {
+	return func(o *optionValues) { o.backendFD = int(dev.File().Fd()) }
+}