TUN inbound: Support autoSystemRoutingTable and autoOutboundsInterface on macOS and Linux as well (#6366)

https://github.com/XTLS/Xray-core/pull/6366#issuecomment-4788510365

proxy/tun/tun_windows.go

@@ -8,6 +8,8 @@ import (
 	go_errors "errors"
 	"net"
 	"net/netip"
+	"sort"
+	"strings"
 	"sync"
 	"unsafe"
 
@@ -307,3 +309,77 @@ func setinterface(network, address string, fd uintptr, iface *net.Interface) err
 
 	return errors.Combine(err1, err2, err3, err4)
 }
+
+func findOutboundInterface(tunIndex int, fixedName string) (*net.Interface, error) {
+	interfaces, err := net.Interfaces()
+	if err != nil {
+		return nil, err
+	}
+
+	if fixedName != "" {
+		for _, iface := range interfaces {
+			if iface.Index != tunIndex && iface.Name == fixedName {
+				return &iface, nil
+			}
+		}
+		return nil, nil
+	}
+
+	var candidates []struct {
+		index int
+		score int
+	}
+	for i, iface := range interfaces {
+		if iface.Index == tunIndex {
+			continue
+		}
+		if strings.Contains(iface.Name, "vEthernet") {
+			continue
+		}
+		if iface.Flags&net.FlagUp == 0 {
+			continue
+		}
+		if iface.Flags&net.FlagLoopback != 0 {
+			continue
+		}
+		addrs, err := iface.Addrs()
+		if err != nil || len(addrs) == 0 {
+			continue
+		}
+		candidates = append(candidates, struct {
+			index int
+			score int
+		}{i, scoreWindowsInterface(&iface, addrs)})
+	}
+
+	sort.Slice(candidates, func(i, j int) bool {
+		if candidates[i].score != candidates[j].score {
+			return candidates[i].score > candidates[j].score
+		}
+		return interfaces[candidates[i].index].Name < interfaces[candidates[j].index].Name
+	})
+	if len(candidates) == 0 {
+		return nil, nil
+	}
+
+	iface := interfaces[candidates[0].index]
+	return &iface, nil
+}
+
+func scoreWindowsInterface(iface *net.Interface, addrs []net.Addr) int {
+	score := 0
+
+	name := strings.ToLower(iface.Name)
+	if strings.Contains(name, "wlan") || strings.Contains(name, "wi-fi") {
+		score += 2
+	}
+
+	for _, addr := range addrs {
+		if strings.HasPrefix(addr.String(), "192.168.") {
+			score++
+			break
+		}
+	}
+
+	return score
+}