From cdb8c53cdea8d8ac6e6f2112e4a5e844bffd01a4 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Mon, 20 May 2019 14:18:01 +0200
Subject: service: split into tunnel and manager

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 tunnel/defaultroutemonitor.go | 150 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 150 insertions(+)
 create mode 100644 tunnel/defaultroutemonitor.go

(limited to 'tunnel/defaultroutemonitor.go')

diff --git a/tunnel/defaultroutemonitor.go b/tunnel/defaultroutemonitor.go
new file mode 100644
index 00000000..1ffce5fa
--- /dev/null
+++ b/tunnel/defaultroutemonitor.go
@@ -0,0 +1,150 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package tunnel
+
+import (
+	"log"
+	"time"
+
+	"golang.org/x/sys/windows"
+	"golang.zx2c4.com/winipcfg"
+	"golang.zx2c4.com/wireguard/device"
+	"golang.zx2c4.com/wireguard/tun"
+)
+
+func bindSocketRoute(family winipcfg.AddressFamily, device *device.Device, ourLUID uint64, lastLUID *uint64, lastIndex *uint32) error {
+	routes, err := winipcfg.GetRoutes(family)
+	if err != nil {
+		return err
+	}
+	lowestMetric := ^uint32(0)
+	index := uint32(0) // Zero is "unspecified", which for IP_UNICAST_IF resets the value, which is what we want.
+	luid := uint64(0)  // Hopefully luid zero is unspecified, but hard to find docs saying so.
+	for _, route := range routes {
+		if route.DestinationPrefix.PrefixLength != 0 || route.InterfaceLUID == ourLUID {
+			continue
+		}
+		ifrow, err := winipcfg.GetIfRow(route.InterfaceLUID)
+		if err != nil || ifrow.OperStatus != winipcfg.IfOperStatusUp {
+			log.Printf("Found default route for interface %d, but not up, so skipping", route.InterfaceIndex)
+			continue
+		}
+		if route.Metric < lowestMetric {
+			lowestMetric = route.Metric
+			index = route.InterfaceIndex
+			luid = route.InterfaceLUID
+		}
+	}
+	if luid == *lastLUID && index == *lastIndex {
+		return nil
+	}
+	*lastLUID = luid
+	*lastIndex = index
+	if family == windows.AF_INET {
+		log.Printf("Binding UDPv4 socket to interface %d", index)
+		return device.BindSocketToInterface4(index)
+	} else if family == windows.AF_INET6 {
+		log.Printf("Binding UDPv6 socket to interface %d", index)
+		return device.BindSocketToInterface6(index)
+	}
+	return nil
+}
+
+func getIPInterfaceRetry(luid uint64, family winipcfg.AddressFamily, retry bool) (ipi *winipcfg.IPInterface, err error) {
+	const maxRetries = 100
+	for i := 0; i < maxRetries; i++ {
+		ipi, err = winipcfg.GetIPInterface(luid, family)
+		if retry && i != maxRetries-1 && err == windows.ERROR_NOT_FOUND {
+			time.Sleep(time.Millisecond * 50)
+			continue
+		}
+		break
+	}
+	return
+}
+
+func monitorDefaultRoutes(device *device.Device, autoMTU bool, tun *tun.NativeTun) (*winipcfg.RouteChangeCallback, error) {
+	ourLUID := tun.LUID()
+	lastLUID4 := uint64(0)
+	lastLUID6 := uint64(0)
+	lastIndex4 := uint32(0)
+	lastIndex6 := uint32(0)
+	lastMTU := uint32(0)
+	doIt := func(retry bool) error {
+		err := bindSocketRoute(windows.AF_INET, device, ourLUID, &lastLUID4, &lastIndex4)
+		if err != nil {
+			return err
+		}
+		err = bindSocketRoute(windows.AF_INET6, device, ourLUID, &lastLUID6, &lastIndex6)
+		if err != nil {
+			return err
+		}
+		if !autoMTU {
+			return nil
+		}
+		mtu := uint32(0)
+		if lastLUID4 != 0 {
+			iface, err := winipcfg.InterfaceFromLUID(lastLUID4)
+			if err != nil {
+				return err
+			}
+			if iface.MTU > 0 {
+				mtu = iface.MTU
+			}
+		}
+		if lastLUID6 != 0 {
+			iface, err := winipcfg.InterfaceFromLUID(lastLUID6)
+			if err != nil {
+				return err
+			}
+			if iface.MTU > 0 && iface.MTU < mtu {
+				mtu = iface.MTU
+			}
+		}
+		if mtu > 0 && (lastMTU == 0 || lastMTU != mtu) {
+			iface, err := getIPInterfaceRetry(ourLUID, windows.AF_INET, retry)
+			if err != nil {
+				return err
+			}
+			iface.NLMTU = mtu - 80
+			if iface.NLMTU < 576 {
+				iface.NLMTU = 576
+			}
+			err = iface.Set()
+			if err != nil {
+				return err
+			}
+			tun.ForceMTU(int(iface.NLMTU)) //TODO: it sort of breaks the model with v6 mtu and v4 mtu being different. Just set v4 one for now.
+			iface, err = getIPInterfaceRetry(ourLUID, windows.AF_INET6, retry)
+			if err != nil {
+				return err
+			}
+			iface.NLMTU = mtu - 80
+			if iface.NLMTU < 1280 {
+				iface.NLMTU = 1280
+			}
+			err = iface.Set()
+			if err != nil {
+				return err
+			}
+			lastMTU = mtu
+		}
+		return nil
+	}
+	err := doIt(true)
+	if err != nil {
+		return nil, err
+	}
+	cb, err := winipcfg.RegisterRouteChangeCallback(func(notificationType winipcfg.MibNotificationType, route *winipcfg.Route) {
+		if route.DestinationPrefix.PrefixLength == 0 {
+			_ = doIt(false)
+		}
+	})
+	if err != nil {
+		return nil, err
+	}
+	return cb, nil
+}
-- 
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