merge with mainnaman/netstack-subnet-routing

Signed-off-by: Naman Sood <mail@nsood.in>

3 files changed, 145 insertions, 92 deletions

diff --git a/net/interfaces/interfaces.go b/net/interfaces/interfaces.go
index 3a0ffeb0b..f2988af34 100644
--- a/net/interfaces/interfaces.go
+++ b/net/interfaces/interfaces.go
@@ -6,10 +6,10 @@
 package interfaces
 
 import (
+	"bytes"
 	"fmt"
 	"net"
 	"net/http"
-	"reflect"
 	"runtime"
 	"sort"
 	"strings"
@@ -190,6 +190,9 @@ func ForeachInterface(fn func(Interface, []netaddr.IPPrefix)) error {
 				}
 			}
 		}
+		sort.Slice(pfxs, func(i, j int) bool {
+			return pfxs[i].IP.Less(pfxs[j].IP)
+		})
 		fn(Interface{iface}, pfxs)
 	}
 	return nil
@@ -204,7 +207,7 @@ type State struct {
 	// IPPrefix, where the IP is the interface IP address and Bits is
 	// the subnet mask.
 	InterfaceIPs map[string][]netaddr.IPPrefix
-	InterfaceUp  map[string]bool
+	Interface    map[string]Interface
 
 	// HaveV6Global is whether this machine has an IPv6 global address
 	// on some non-Tailscale interface that's up.
@@ -235,14 +238,14 @@ type State struct {
 func (s *State) String() string {
 	var sb strings.Builder
 	fmt.Fprintf(&sb, "interfaces.State{defaultRoute=%v ifs={", s.DefaultRouteInterface)
-	ifs := make([]string, 0, len(s.InterfaceUp))
-	for k := range s.InterfaceUp {
+	ifs := make([]string, 0, len(s.Interface))
+	for k := range s.Interface {
 		if anyInterestingIP(s.InterfaceIPs[k]) {
 			ifs = append(ifs, k)
 		}
 	}
 	sort.Slice(ifs, func(i, j int) bool {
-		upi, upj := s.InterfaceUp[ifs[i]], s.InterfaceUp[ifs[j]]
+		upi, upj := s.Interface[ifs[i]].IsUp(), s.Interface[ifs[j]].IsUp()
 		if upi != upj {
 			// Up sorts before down.
 			return upi
@@ -253,7 +256,7 @@ func (s *State) String() string {
 		if i > 0 {
 			sb.WriteString(" ")
 		}
-		if s.InterfaceUp[ifName] {
+		if s.Interface[ifName].IsUp() {
 			fmt.Fprintf(&sb, "%s:[", ifName)
 			needSpace := false
 			for _, pfx := range s.InterfaceIPs[ifName] {
@@ -286,50 +289,76 @@ func (s *State) String() string {
 	return sb.String()
 }
 
-func (s *State) Equal(s2 *State) bool {
-	return reflect.DeepEqual(s, s2)
-}
-
-func (s *State) HasPAC() bool { return s != nil && s.PAC != "" }
-
-// AnyInterfaceUp reports whether any interface seems like it has Internet access.
-func (s *State) AnyInterfaceUp() bool {
-	return s != nil && (s.HaveV4 || s.HaveV6Global)
-}
-
-// RemoveUninterestingInterfacesAndAddresses removes uninteresting IPs
-// from InterfaceIPs, also removing from both the InterfaceIPs and
-// InterfaceUp map any interfaces that don't have any interesting IPs.
-func (s *State) RemoveUninterestingInterfacesAndAddresses() {
-	for ifName := range s.InterfaceUp {
-		ips := s.InterfaceIPs[ifName]
-		keep := ips[:0]
-		for _, pfx := range ips {
-			if isInterestingIP(pfx.IP) {
-				keep = append(keep, pfx)
-			}
-		}
-		if len(keep) == 0 {
-			delete(s.InterfaceUp, ifName)
-			delete(s.InterfaceIPs, ifName)
+// EqualFiltered reports whether s and s2 are equal,
+// considering only interfaces in s for which filter returns true.
+func (s *State) EqualFiltered(s2 *State, filter func(i Interface, ips []netaddr.IPPrefix) bool) bool {
+	if s == nil && s2 == nil {
+		return true
+	}
+	if s == nil || s2 == nil {
+		return false
+	}
+	if s.HaveV6Global != s2.HaveV6Global ||
+		s.HaveV4 != s2.HaveV4 ||
+		s.IsExpensive != s2.IsExpensive ||
+		s.DefaultRouteInterface != s2.DefaultRouteInterface ||
+		s.HTTPProxy != s2.HTTPProxy ||
+		s.PAC != s2.PAC {
+		return false
+	}
+	for iname, i := range s.Interface {
+		ips := s.InterfaceIPs[iname]
+		if !filter(i, ips) {
 			continue
 		}
-		if len(keep) < len(ips) {
-			s.InterfaceIPs[ifName] = keep
+		i2, ok := s2.Interface[iname]
+		if !ok {
+			return false
+		}
+		ips2, ok := s2.InterfaceIPs[iname]
+		if !ok {
+			return false
+		}
+		if !interfacesEqual(i, i2) || !prefixesEqual(ips, ips2) {
+			return false
 		}
 	}
+	return true
+}
+
+func interfacesEqual(a, b Interface) bool {
+	return a.Index == b.Index &&
+		a.MTU == b.MTU &&
+		a.Name == b.Name &&
+		a.Flags == b.Flags &&
+		bytes.Equal([]byte(a.HardwareAddr), []byte(b.HardwareAddr))
 }
 
-// RemoveTailscaleInterfaces modifes s to remove any interfaces that
-// are owned by this process. (TODO: make this true; currently it
-// uses some heuristics)
-func (s *State) RemoveTailscaleInterfaces() {
-	for name, pfxs := range s.InterfaceIPs {
-		if isTailscaleInterface(name, pfxs) {
-			delete(s.InterfaceIPs, name)
-			delete(s.InterfaceUp, name)
+func prefixesEqual(a, b []netaddr.IPPrefix) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i, v := range a {
+		if b[i] != v {
+			return false
 		}
 	}
+	return true
+}
+
+// FilterInteresting reports whether i is an interesting non-Tailscale interface.
+func FilterInteresting(i Interface, ips []netaddr.IPPrefix) bool {
+	return !isTailscaleInterface(i.Name, ips) && anyInterestingIP(ips)
+}
+
+// FilterAll always returns true, to use EqualFiltered against all interfaces.
+func FilterAll(i Interface, ips []netaddr.IPPrefix) bool { return true }
+
+func (s *State) HasPAC() bool { return s != nil && s.PAC != "" }
+
+// AnyInterfaceUp reports whether any interface seems like it has Internet access.
+func (s *State) AnyInterfaceUp() bool {
+	return s != nil && (s.HaveV4 || s.HaveV6Global)
 }
 
 func hasTailscaleIP(pfxs []netaddr.IPPrefix) bool {
@@ -364,11 +393,11 @@ var getPAC func() string
 func GetState() (*State, error) {
 	s := &State{
 		InterfaceIPs: make(map[string][]netaddr.IPPrefix),
-		InterfaceUp:  make(map[string]bool),
+		Interface:    make(map[string]Interface),
 	}
 	if err := ForeachInterface(func(ni Interface, pfxs []netaddr.IPPrefix) {
 		ifUp := ni.IsUp()
-		s.InterfaceUp[ni.Name] = ifUp
+		s.Interface[ni.Name] = ni
 		s.InterfaceIPs[ni.Name] = append(s.InterfaceIPs[ni.Name], pfxs...)
 		if !ifUp || isTailscaleInterface(ni.Name, pfxs) {
 			return
diff --git a/net/interfaces/interfaces_test.go b/net/interfaces/interfaces_test.go
index 88948b579..ab0ee3734 100644
--- a/net/interfaces/interfaces_test.go
+++ b/net/interfaces/interfaces_test.go
@@ -5,6 +5,7 @@
 package interfaces
 
 import (
+	"encoding/json"
 	"testing"
 )
 
@@ -13,7 +14,11 @@ func TestGetState(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	t.Logf("Got: %#v", st)
+	j, err := json.MarshalIndent(st, "", "\t")
+	if err != nil {
+		t.Errorf("JSON: %v", err)
+	}
+	t.Logf("Got: %s", j)
 	t.Logf("As string: %s", st)
 
 	st2, err := GetState()
@@ -21,14 +26,13 @@ func TestGetState(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if !st.Equal(st2) {
+	if !st.EqualFiltered(st2, FilterAll) {
 		// let's assume nobody was changing the system network interfaces between
 		// the two GetState calls.
 		t.Fatal("two States back-to-back were not equal")
 	}
 
-	st.RemoveTailscaleInterfaces()
-	t.Logf("As string without Tailscale:\n\t%s", st)
+	t.Logf("As string:\n\t%s", st)
 }
 
 func TestLikelyHomeRouterIP(t *testing.T) {
diff --git a/net/interfaces/interfaces_windows.go b/net/interfaces/interfaces_windows.go
index 19e9b48b4..91f679c97 100644
--- a/net/interfaces/interfaces_windows.go
+++ b/net/interfaces/interfaces_windows.go
@@ -7,17 +7,19 @@ package interfaces
 import (
 	"fmt"
 	"log"
+	"net"
 	"net/url"
-	"os/exec"
 	"syscall"
 	"unsafe"
 
-	"go4.org/mem"
 	"golang.org/x/sys/windows"
 	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
 	"inet.af/netaddr"
 	"tailscale.com/tsconst"
-	"tailscale.com/util/lineread"
+)
+
+const (
+	fallbackInterfaceMetric = uint32(0) // Used if we cannot get the actual interface metric
 )
 
 func init() {
@@ -25,58 +27,76 @@ func init() {
 	getPAC = getPACWindows
 }
 
-/*
-Parse out 10.0.0.1 from:
-
-Z:\>route print -4
-===========================================================================
-Interface List
- 15...aa 15 48 ff 1c 72 ......Red Hat VirtIO Ethernet Adapter
-  5...........................Tailscale Tunnel
-  1...........................Software Loopback Interface 1
-===========================================================================
-
-IPv4 Route Table
-===========================================================================
-Active Routes:
-Network Destination        Netmask          Gateway       Interface  Metric
-          0.0.0.0          0.0.0.0         10.0.0.1       10.0.28.63      5
-         10.0.0.0      255.255.0.0         On-link        10.0.28.63    261
-       10.0.28.63  255.255.255.255         On-link        10.0.28.63    261
-        10.0.42.0    255.255.255.0   100.103.42.106   100.103.42.106      5
-     10.0.255.255  255.255.255.255         On-link        10.0.28.63    261
-   34.193.248.174  255.255.255.255   100.103.42.106   100.103.42.106      5
-
-*/
 func likelyHomeRouterIPWindows() (ret netaddr.IP, ok bool) {
-	cmd := exec.Command("route", "print", "-4")
-	cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
-	stdout, err := cmd.StdoutPipe()
+	rs, err := winipcfg.GetIPForwardTable2(windows.AF_INET)
 	if err != nil {
+		log.Printf("routerIP/GetIPForwardTable2 error: %v", err)
 		return
 	}
-	if err := cmd.Start(); err != nil {
+
+	var ifaceMetricCache map[winipcfg.LUID]uint32
+
+	getIfaceMetric := func(luid winipcfg.LUID) (metric uint32) {
+		if ifaceMetricCache == nil {
+			ifaceMetricCache = make(map[winipcfg.LUID]uint32)
+		} else if m, ok := ifaceMetricCache[luid]; ok {
+			return m
+		}
+
+		if iface, err := luid.IPInterface(windows.AF_INET); err == nil {
+			metric = iface.Metric
+		} else {
+			log.Printf("routerIP/luid.IPInterface error: %v", err)
+			metric = fallbackInterfaceMetric
+		}
+
+		ifaceMetricCache[luid] = metric
 		return
 	}
-	defer cmd.Wait()
 
-	var f []mem.RO
-	lineread.Reader(stdout, func(lineb []byte) error {
-		line := mem.B(lineb)
-		if !mem.Contains(line, mem.S("0.0.0.0")) {
-			return nil
+	unspec := net.IPv4(0, 0, 0, 0)
+	var best *winipcfg.MibIPforwardRow2 // best (lowest metric) found so far, or nil
+
+	for i := range rs {
+		r := &rs[i]
+		if r.Loopback || r.DestinationPrefix.PrefixLength != 0 || !r.DestinationPrefix.Prefix.IP().Equal(unspec) {
+			// Not a default route, so skip
+			continue
 		}
-		f = mem.AppendFields(f[:0], line)
-		if len(f) < 3 || !f[0].EqualString("0.0.0.0") || !f[1].EqualString("0.0.0.0") {
-			return nil
+
+		ip, ok := netaddr.FromStdIP(r.NextHop.IP())
+		if !ok {
+			// Not a valid gateway, so skip (won't happen though)
+			continue
 		}
-		ipm := f[2]
-		ip, err := netaddr.ParseIP(string(mem.Append(nil, ipm)))
-		if err == nil && isPrivateIP(ip) {
+
+		if best == nil {
+			best = r
 			ret = ip
+			continue
 		}
-		return nil
-	})
+
+		// We can get here only if there are multiple default gateways defined (rare case),
+		// in which case we need to calculate the effective metric.
+		// Effective metric is sum of interface metric and route metric offset
+		if ifaceMetricCache == nil {
+			// If we're here it means that previous route still isn't updated, so update it
+			best.Metric += getIfaceMetric(best.InterfaceLUID)
+		}
+		r.Metric += getIfaceMetric(r.InterfaceLUID)
+
+		if best.Metric > r.Metric || best.Metric == r.Metric && ret.Compare(ip) > 0 {
+			// Pick the route with lower metric, or lower IP if metrics are equal
+			best = r
+			ret = ip
+		}
+	}
+
+	if !ret.IsZero() && !isPrivateIP(ret) {
+		// Default route has a non-private gateway
+		return netaddr.IP{}, false
+	}
+
 	return ret, !ret.IsZero()
 }