use saved static nameservers stored for the default router interface when doing nameserver discovery

fix bad logger usages

patch darwin interface name

patch darwin interface name, debugging

make resetDNS check for static config on startup, optionally restoring static confiration as needed

fix netmon logging

staticdns.go

@@ -0,0 +1,118 @@
+package ctrld
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"net"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+var homedir string
+
+// absHomeDir returns the absolute path to given filename using home directory as root dir.
+func absHomeDir(filename string) string {
+	if homedir != "" {
+		return filepath.Join(homedir, filename)
+	}
+	dir, err := userHomeDir()
+	if err != nil {
+		return filename
+	}
+	return filepath.Join(dir, filename)
+}
+
+func dirWritable(dir string) (bool, error) {
+	f, err := os.CreateTemp(dir, "")
+	if err != nil {
+		return false, err
+	}
+	defer os.Remove(f.Name())
+	return true, f.Close()
+}
+
+func userHomeDir() (string, error) {
+	// viper will expand for us.
+	if runtime.GOOS == "windows" {
+		// If we're on windows, use the install path for this.
+		exePath, err := os.Executable()
+		if err != nil {
+			return "", err
+		}
+
+		return filepath.Dir(exePath), nil
+	}
+	dir := "/etc/controld"
+	if err := os.MkdirAll(dir, 0750); err != nil {
+		return os.UserHomeDir() // fallback to user home directory
+	}
+	if ok, _ := dirWritable(dir); !ok {
+		return os.UserHomeDir()
+	}
+	return dir, nil
+}
+
+// SavedStaticDnsSettingsFilePath returns the file path where the static DNS settings
+// for the provided interface are saved.
+func SavedStaticDnsSettingsFilePath(iface *net.Interface) string {
+	// The file is stored in the user home directory under a hidden file.
+	return absHomeDir(".dns_" + iface.Name)
+}
+
+// SavedStaticNameservers returns the stored static nameservers for the given interface.
+func SavedStaticNameservers(iface *net.Interface) ([]string, string) {
+	file := SavedStaticDnsSettingsFilePath(iface)
+	data, err := os.ReadFile(file)
+	if err != nil || len(data) == 0 {
+		return nil, file
+	}
+	saveValues := strings.Split(string(data), ",")
+	var ns []string
+	for _, v := range saveValues {
+		// Skip any IP that is loopback
+		if ip := net.ParseIP(v); ip != nil && ip.IsLoopback() {
+			continue
+		}
+		ns = append(ns, v)
+	}
+	return ns, file
+}
+
+func patchNetIfaceName(iface *net.Interface) (bool, error) {
+	b, err := exec.Command("networksetup", "-listnetworkserviceorder").Output()
+	if err != nil {
+		return false, err
+	}
+
+	patched := false
+	if name := networkServiceName(iface.Name, bytes.NewReader(b)); name != "" {
+		patched = true
+		iface.Name = name
+	}
+	return patched, nil
+}
+
+func networkServiceName(ifaceName string, r io.Reader) string {
+	scanner := bufio.NewScanner(r)
+	prevLine := ""
+	for scanner.Scan() {
+		line := scanner.Text()
+		if strings.Contains(line, "*") {
+			// Network services is disabled.
+			continue
+		}
+		if !strings.Contains(line, "Device: "+ifaceName) {
+			prevLine = line
+			continue
+		}
+		parts := strings.SplitN(prevLine, " ", 2)
+		if len(parts) == 2 {
+			return strings.TrimSpace(parts[1])
+		}
+	}
+	return ""
+}