From 3974133ddf46eb016cde4a99900294faa08fbf84 Mon Sep 17 00:00:00 2001
From: Andrey Filatov <filatov.andrey.m@gmail.com>
Date: Fri, 6 Feb 2026 12:55:56 +0300
Subject: [PATCH] feat: add InterfaceMetric and RouteMetric fields

---
 tun.go         |  2 ++
 tun_linux.go   |  6 +++++-
 tun_windows.go | 18 ++++++++++++------
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/tun.go b/tun.go
index 35cd095..a5a73cd 100644
--- a/tun.go
+++ b/tun.go
@@ -74,6 +74,8 @@ type Options struct {
 	Inet6Address                          []netip.Prefix
 	MTU                                   uint32
 	GSO                                   bool
+	InterfaceMetric                       uint32
+	RouteMetric                           uint32
 	AutoRoute                             bool
 	InterfaceScope                        bool
 	Inet4Gateway                          netip.Addr
diff --git a/tun_linux.go b/tun_linux.go
index f35921e..27828c0 100644
--- a/tun_linux.go
+++ b/tun_linux.go
@@ -520,12 +520,16 @@ func (t *NativeTun) routes(tunLink netlink.Link) ([]netlink.Route, error) {
 		} else if it.Addr().Is6() && !gateway6.IsUnspecified() {
 			gateway = gateway6.AsSlice()
 		}
-		return netlink.Route{
+		route := netlink.Route{
 			Dst:       prefixToIPNet(it),
 			Gw:        gateway,
 			LinkIndex: tunLink.Attrs().Index,
 			Table:     t.options.IPRoute2TableIndex,
 		}
+		if t.options.RouteMetric > 0 {
+			route.Priority = int(t.options.RouteMetric)
+		}
+		return route
 	}), nil
 }
 
diff --git a/tun_windows.go b/tun_windows.go
index 54e7395..89e9104 100644
--- a/tun_windows.go
+++ b/tun_windows.go
@@ -129,7 +129,10 @@ func (t *NativeTun) configure() error {
 		inetIf.ManagedAddressConfigurationSupported = false
 		inetIf.OtherStatefulConfigurationSupported = false
 		inetIf.NLMTU = t.options.MTU
-		if t.options.AutoRoute {
+		if t.options.InterfaceMetric > 0 {
+			inetIf.UseAutomaticMetric = false
+			inetIf.Metric = t.options.InterfaceMetric
+		} else if t.options.AutoRoute {
 			inetIf.UseAutomaticMetric = false
 			inetIf.Metric = 0
 		}
@@ -148,7 +151,10 @@ func (t *NativeTun) configure() error {
 		inet6If.ManagedAddressConfigurationSupported = false
 		inet6If.OtherStatefulConfigurationSupported = false
 		inet6If.NLMTU = t.options.MTU
-		if t.options.AutoRoute {
+		if t.options.InterfaceMetric > 0 {
+			inet6If.UseAutomaticMetric = false
+			inet6If.Metric = t.options.InterfaceMetric
+		} else if t.options.AutoRoute {
 			inet6If.UseAutomaticMetric = false
 			inet6If.Metric = 0
 		}
@@ -175,7 +181,7 @@ func (t *NativeTun) Start() error {
 	if err != nil {
 		return err
 	}
-	err = addRouteList(luid, routeRanges, gateway4, gateway6, 0)
+	err = t.addRouteList(luid, routeRanges, gateway4, gateway6)
 	if err != nil {
 		return err
 	}
@@ -584,7 +590,7 @@ func (t *NativeTun) UpdateRouteOptions(tunOptions Options) error {
 	if err != nil {
 		return err
 	}
-	err = addRouteList(luid, routeRanges, gateway4, gateway6, 0)
+	err = t.addRouteList(luid, routeRanges, gateway4, gateway6)
 	if err != nil {
 		return err
 	}
@@ -595,11 +601,11 @@ func (t *NativeTun) UpdateRouteOptions(tunOptions Options) error {
 	return nil
 }
 
-func addRouteList(luid winipcfg.LUID, destinations []netip.Prefix, gateway4 netip.Addr, gateway6 netip.Addr, metric uint32) error {
+func (t *NativeTun) addRouteList(luid winipcfg.LUID, destinations []netip.Prefix, gateway4 netip.Addr, gateway6 netip.Addr) error {
 	row := winipcfg.MibIPforwardRow2{}
 	row.Init()
 	row.InterfaceLUID = luid
-	row.Metric = metric
+	row.Metric = t.options.RouteMetric
 	nextHop4 := row.NextHop
 	nextHop6 := row.NextHop
 	if gateway4.IsValid() {