refactor: improve network interface validation

Add context parameter to validInterfacesMap for better error handling and
logging. Move Windows-specific network adapter validation logic to the
ctrld package. Key changes include:

- Add context parameter to validInterfacesMap across all platforms
- Move Windows validInterfaces to ctrld.ValidInterfaces
- Improve error handling for virtual interface detection on Linux
- Update all callers to pass appropriate context

This change improves error reporting and makes the interface validation
code more maintainable across different platforms.

cmd/cli/dns_proxy.go

@@ -1201,7 +1201,7 @@ func (p *prog) monitorNetworkChanges(ctx context.Context) error {
 
 	mon.RegisterChangeCallback(func(delta *netmon.ChangeDelta) {
 		// Get map of valid interfaces
-		validIfaces := validInterfacesMap()
+		validIfaces := validInterfacesMap(ctrld.LoggerCtx(ctx, p.logger.Load()))
 
 		isMajorChange := mon.IsMajorChangeFrom(delta.Old, delta.New)
 

cmd/cli/net_darwin.go

@@ -3,6 +3,7 @@ package cli
 import (
 	"bufio"
 	"bytes"
+	"context"
 	"io"
 	"net"
 	"os/exec"
@@ -51,7 +52,7 @@ func validInterface(iface *net.Interface, validIfacesMap map[string]struct{}) bo
 }
 
 // validInterfacesMap returns a set of all valid hardware ports.
-func validInterfacesMap() map[string]struct{} {
+func validInterfacesMap(ctx context.Context) map[string]struct{} {
 	b, err := exec.Command("networksetup", "-listallhardwareports").Output()
 	if err != nil {
 		return nil

cmd/cli/net_linux.go

@@ -1,12 +1,15 @@
 package cli
 
 import (
+	"context"
 	"net"
 	"net/netip"
 	"os"
 	"strings"
 
 	"tailscale.com/net/netmon"
+
+	"github.com/Control-D-Inc/ctrld"
 )
 
 func patchNetIfaceName(iface *net.Interface) (bool, error) { return true, nil }
@@ -19,16 +22,16 @@ func validInterface(iface *net.Interface, validIfacesMap map[string]struct{}) bo
 }
 
 // validInterfacesMap returns a set containing non virtual interfaces.
-func validInterfacesMap() map[string]struct{} {
+func validInterfacesMap(ctx context.Context) map[string]struct{} {
 	m := make(map[string]struct{})
-	vis := virtualInterfaces()
+	vis := virtualInterfaces(ctx)
 	netmon.ForeachInterface(func(i netmon.Interface, prefixes []netip.Prefix) {
 		if _, existed := vis[i.Name]; existed {
 			return
 		}
 		m[i.Name] = struct{}{}
 	})
-	// Fallback to default route interface if found nothing.
+	// Fallback to the default route interface if found nothing.
 	if len(m) == 0 {
 		defaultRoute, err := netmon.DefaultRoute()
 		if err != nil {
@@ -39,10 +42,15 @@ func validInterfacesMap() map[string]struct{} {
 	return m
 }
 
-// virtualInterfaces returns a map of virtual interfaces on current machine.
-func virtualInterfaces() map[string]struct{} {
+// virtualInterfaces returns a map of virtual interfaces on the current machine.
+func virtualInterfaces(ctx context.Context) map[string]struct{} {
+	logger := ctrld.LoggerFromCtx(ctx)
 	s := make(map[string]struct{})
-	entries, _ := os.ReadDir("/sys/devices/virtual/net")
+	entries, err := os.ReadDir("/sys/devices/virtual/net")
+	if err != nil {
+		logger.Error().Err(err).Msg("failed to read /sys/devices/virtual/net")
+		return nil
+	}
 	for _, entry := range entries {
 		if entry.IsDir() {
 			s[strings.TrimSpace(entry.Name())] = struct{}{}

cmd/cli/net_others.go

@@ -3,6 +3,7 @@
 package cli
 
 import (
+	"context"
 	"net"
 
 	"tailscale.com/net/netmon"
@@ -13,7 +14,7 @@ func patchNetIfaceName(iface *net.Interface) (bool, error) { return true, nil }
 func validInterface(iface *net.Interface, validIfacesMap map[string]struct{}) bool { return true }
 
 // validInterfacesMap returns a set containing only default route interfaces.
-func validInterfacesMap() map[string]struct{} {
+func validInterfacesMap(ctx context.Context) map[string]struct{} {
 	defaultRoute, err := netmon.DefaultRoute()
 	if err != nil {
 		return nil

cmd/cli/net_windows.go

@@ -1,16 +1,10 @@
 package cli
 
 import (
-	"io"
-	"log"
+	"context"
 	"net"
-	"os"
 
-	"github.com/microsoft/wmi/pkg/base/host"
-	"github.com/microsoft/wmi/pkg/base/instance"
-	"github.com/microsoft/wmi/pkg/base/query"
-	"github.com/microsoft/wmi/pkg/constant"
-	"github.com/microsoft/wmi/pkg/hardware/network/netadapter"
+	"github.com/Control-D-Inc/ctrld"
 )
 
 func patchNetIfaceName(iface *net.Interface) (bool, error) {
@@ -25,69 +19,10 @@ func validInterface(iface *net.Interface, validIfacesMap map[string]struct{}) bo
 }
 
 // validInterfacesMap returns a set of all physical interfaces.
-func validInterfacesMap() map[string]struct{} {
+func validInterfacesMap(ctx context.Context) map[string]struct{} {
 	m := make(map[string]struct{})
-	for _, ifaceName := range validInterfaces() {
+	for ifaceName := range ctrld.ValidInterfaces(ctx) {
 		m[ifaceName] = struct{}{}
 	}
 	return m
 }
-
-// validInterfaces returns a list of all physical interfaces.
-func validInterfaces() []string {
-	log.SetOutput(io.Discard)
-	defer log.SetOutput(os.Stderr)
-	whost := host.NewWmiLocalHost()
-	q := query.NewWmiQuery("MSFT_NetAdapter")
-	instances, err := instance.GetWmiInstancesFromHost(whost, string(constant.StadardCimV2), q)
-	if instances != nil {
-		defer instances.Close()
-	}
-	if err != nil {
-		mainLog.Load().Warn().Err(err).Msg("failed to get wmi network adapter")
-		return nil
-	}
-	var adapters []string
-	for _, i := range instances {
-		adapter, err := netadapter.NewNetworkAdapter(i)
-		if err != nil {
-			mainLog.Load().Warn().Err(err).Msg("failed to get network adapter")
-			continue
-		}
-
-		name, err := adapter.GetPropertyName()
-		if err != nil {
-			mainLog.Load().Warn().Err(err).Msg("failed to get interface name")
-			continue
-		}
-
-		// From: https://learn.microsoft.com/en-us/previous-versions/windows/desktop/legacy/hh968170(v=vs.85)
-		//
-		// "Indicates if a connector is present on the network adapter. This value is set to TRUE
-		// if this is a physical adapter or FALSE if this is not a physical adapter."
-		physical, err := adapter.GetPropertyConnectorPresent()
-		if err != nil {
-			mainLog.Load().Debug().Str("method", "validInterfaces").Str("interface", name).Msg("failed to get network adapter connector present property")
-			continue
-		}
-		if !physical {
-			mainLog.Load().Debug().Str("method", "validInterfaces").Str("interface", name).Msg("skipping non-physical adapter")
-			continue
-		}
-
-		// Check if it's a hardware interface. Checking only for connector present is not enough
-		// because some interfaces are not physical but have a connector.
-		hardware, err := adapter.GetPropertyHardwareInterface()
-		if err != nil {
-			mainLog.Load().Debug().Str("method", "validInterfaces").Str("interface", name).Msg("failed to get network adapter hardware interface property")
-			continue
-		}
-		if !hardware {
-			mainLog.Load().Debug().Str("method", "validInterfaces").Str("interface", name).Msg("skipping non-hardware interface")
-			continue
-		}
-
-		adapters = append(adapters, name)
-	}
-	return adapters
-}

cmd/cli/net_windows_test.go

@@ -3,18 +3,23 @@ package cli
 import (
 	"bufio"
 	"bytes"
+	"context"
+	"maps"
 	"slices"
 	"strings"
 	"testing"
 	"time"
+
+	"github.com/Control-D-Inc/ctrld"
 )
 
 func Test_validInterfaces(t *testing.T) {
 	verbose = 3
 	initConsoleLogging()
 	start := time.Now()
-	ifaces := validInterfaces()
+	im := ctrld.ValidInterfaces(ctrld.LoggerCtx(context.Background(), mainLog.Load()))
 	t.Logf("Using Windows API takes: %d", time.Since(start).Milliseconds())
+	ifaces := slices.Collect(maps.Keys(im))
 
 	start = time.Now()
 	ifacesPowershell := validInterfacesPowershell()

cmd/cli/prog.go

@@ -1320,8 +1320,8 @@ func canBeLocalUpstream(addr string) bool {
 // withEachPhysicalInterfaces runs the function f with each physical interfaces, excluding
 // the interface that matches excludeIfaceName. The context is used to clarify the
 // log message when error happens.
-func withEachPhysicalInterfaces(excludeIfaceName, context string, f func(i *net.Interface) error) {
-	validIfacesMap := validInterfacesMap()
+func withEachPhysicalInterfaces(excludeIfaceName, contextStr string, f func(i *net.Interface) error) {
+	validIfacesMap := validInterfacesMap(ctrld.LoggerCtx(context.Background(), mainLog.Load()))
 	netmon.ForeachInterface(func(i netmon.Interface, prefixes []netip.Prefix) {
 		// Skip loopback/virtual/down interface.
 		if i.IsLoopback() || len(i.HardwareAddr) == 0 {
@@ -1345,11 +1345,11 @@ func withEachPhysicalInterfaces(excludeIfaceName, context string, f func(i *net.
 		}
 		// TODO: investigate whether we should report this error?
 		if err := f(netIface); err == nil {
-			if context != "" {
-				mainLog.Load().Debug().Msgf("Ran %s for interface %q successfully", context, i.Name)
+			if contextStr != "" {
+				mainLog.Load().Debug().Msgf("Ran %s for interface %q successfully", contextStr, i.Name)
 			}
 		} else if !errors.Is(err, errSaveCurrentStaticDNSNotSupported) {
-			mainLog.Load().Err(err).Msgf("%s for interface %q failed", context, i.Name)
+			mainLog.Load().Err(err).Msgf("%s for interface %q failed", contextStr, i.Name)
 		}
 	})
 }

nameservers_windows.go

@@ -210,7 +210,7 @@ func getDNSServers(ctx context.Context) ([]string, error) {
 		}
 	}
 
-	validInterfacesMap := validInterfaces(ctx)
+	validInterfacesMap := ValidInterfaces(ctx)
 
 	// Collect DNS servers
 	for _, aa := range aas {
@@ -377,10 +377,9 @@ func getLocalADDomain() (string, error) {
 	return domainName, nil
 }
 
-// validInterfaces returns a list of all physical interfaces.
-// this is a duplicate of what is in net_windows.go, we should
-// clean this up so there is only one version
-func validInterfaces(ctx context.Context) map[string]struct{} {
+// ValidInterfaces returns a map of valid network interface names as keys with empty struct values.
+// It filters interfaces to include only physical, hardware-based adapters using WMI queries.
+func ValidInterfaces(ctx context.Context) map[string]struct{} {
 	log.SetOutput(io.Discard)
 	defer log.SetOutput(os.Stderr)