virtual-net: initial (#4751)

pkg/vnet/tun_linux.go

@@ -0,0 +1,84 @@
+// Copyright 2025 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package vnet
+
+import (
+	"context"
+	"fmt"
+	"net"
+
+	"github.com/vishvananda/netlink"
+	"golang.zx2c4.com/wireguard/tun"
+)
+
+const (
+	defaultTunName = "utun"
+	defaultMTU     = 1420
+)
+
+func openTun(_ context.Context, addr string) (tun.Device, error) {
+	dev, err := tun.CreateTUN(defaultTunName, defaultMTU)
+	if err != nil {
+		return nil, err
+	}
+
+	name, err := dev.Name()
+	if err != nil {
+		return nil, err
+	}
+
+	ifn, err := net.InterfaceByName(name)
+	if err != nil {
+		return nil, err
+	}
+
+	link, err := netlink.LinkByName(name)
+	if err != nil {
+		return nil, err
+	}
+
+	ip, cidr, err := net.ParseCIDR(addr)
+	if err != nil {
+		return nil, err
+	}
+	if err := netlink.AddrAdd(link, &netlink.Addr{
+		IPNet: &net.IPNet{
+			IP:   ip,
+			Mask: cidr.Mask,
+		},
+	}); err != nil {
+		return nil, err
+	}
+
+	if err := netlink.LinkSetUp(link); err != nil {
+		return nil, err
+	}
+
+	if err = addRoutes(ifn, cidr); err != nil {
+		return nil, err
+	}
+	return dev, nil
+}
+
+func addRoutes(ifn *net.Interface, cidr *net.IPNet) error {
+	r := netlink.Route{
+		Dst:       cidr,
+		LinkIndex: ifn.Index,
+	}
+	if err := netlink.RouteReplace(&r); err != nil {
+		return fmt.Errorf("add route to %v error: %v", r.Dst, err)
+	}
+	return nil
+}