init

internal/tun/tun_linux.go

@@ -0,0 +1,61 @@
+//go:build !darwin
+
+package tun
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"os/exec"
+	"strings"
+
+	"github.com/songgao/water"
+)
+
+type linuxDevice struct {
+	ifce *water.Interface
+}
+
+func createTUN(name string) (Device, error) {
+	cfg := water.Config{DeviceType: water.TUN}
+	cfg.Name = name
+	ifce, err := water.New(cfg)
+	if err != nil {
+		return nil, fmt.Errorf("create tun: %w", err)
+	}
+	return &linuxDevice{ifce: ifce}, nil
+}
+
+func (d *linuxDevice) Name() string                { return d.ifce.Name() }
+func (d *linuxDevice) Read(p []byte) (int, error)  { return d.ifce.Read(p) }
+func (d *linuxDevice) Write(p []byte) (int, error) { return d.ifce.Write(p) }
+func (d *linuxDevice) Close() error                { return d.ifce.Close() }
+
+func (d *linuxDevice) Configure(localIP net.IP, prefix int, peerIP net.IP) error {
+	if err := execCmd("ip", "link", "set", "dev", d.Name(), "up"); err != nil {
+		return err
+	}
+	if localIP == nil {
+		return nil
+	}
+	localCidr := fmt.Sprintf("%s/%d", localIP.String(), prefix)
+	if err := execCmd("ip", "addr", "add", "dev", d.Name(), localCidr, "peer", peerIP.String()); err != nil {
+		// Fall back without peer (some kernels).
+		return execCmd("ip", "addr", "add", "dev", d.Name(), localCidr)
+	}
+	return nil
+}
+
+func (d *linuxDevice) SetMTU(mtu int) error {
+	return execCmd("ip", "link", "set", "dev", d.Name(), "mtu", fmt.Sprintf("%d", mtu))
+}
+
+func execCmd(name string, arg ...string) error {
+	cmd := exec.Command(name, arg...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("%s %s: %w", name, strings.Join(arg, " "), err)
+	}
+	return nil
+}