Add disableDNS option

README.md

@@ -43,6 +43,9 @@ ipv6: false
 driver: wireguard
 # When pppd driver is used, you can specify a list of extra pppd arguments
 PPPdArgs: []
+# disableDNS allows to completely disable DNS handling,
+# i.e. don't alter the /etc/resolv.conf file at all
+disableDNS: false
 # a list of DNS zones to be resolved by VPN DNS servers
 # when empty, every DNS query will be resolved by VPN DNS servers
 dns:

pkg/config.go

@@ -174,10 +174,12 @@ func readConfig() (*Config, error) {
 		return nil, fmt.Errorf("%q driver is unsupported, supported drivers are: %q", config.Driver, supportedDrivers)
 	}
 
-	// read current resolv.conf
-	config.resolvConf, err = ioutil.ReadFile(resolvPath)
-	if err != nil {
-		return nil, fmt.Errorf("cannot read %s: %s", resolvPath, err)
+	if !config.DisableDNS {
+		// read current resolv.conf
+		config.resolvConf, err = ioutil.ReadFile(resolvPath)
+		if err != nil {
+			return nil, fmt.Errorf("cannot read %s: %s", resolvPath, err)
+		}
 	}
 
 	if len(config.DNSServers) == 0 {

pkg/link.go

@@ -256,14 +256,16 @@ func (l *vpnLink) waitAndConfig(config *Config) {
 	l.Lock()
 	defer l.Unlock()
 
-	// define DNS servers, provided by F5
-	log.Printf("Setting %s", resolvPath)
-	if err = configureDNS(config); err != nil {
-		l.errChan <- err
-	}
+	if !config.DisableDNS {
+		// define DNS servers, provided by F5
+		log.Printf("Setting %s", resolvPath)
+		if err = configureDNS(config); err != nil {
+			l.errChan <- err
+		}
 
-	if len(config.DNS) > 0 {
-		startDNS(l, config)
+		if len(config.DNS) > 0 {
+			startDNS(l, config)
+		}
 	}
 
 	// set routes
@@ -321,7 +323,9 @@ func (l *vpnLink) restoreConfig(config *Config) {
 		}
 	}()
 
-	restoreDNS(config)
+	if !config.DisableDNS {
+		restoreDNS(config)
+	}
 
 	if l.serverRoutesReady {
 		// remove F5 gateway route

pkg/types.go

@@ -139,6 +139,8 @@ type Config struct {
 	InsecureTLS bool         `yaml:"insecureTLS"`
 	DTLS        bool         `yaml:"dtls"`
 	IPv6        bool         `yaml:"ipv6"`
+	// completely disable DNS servers handling
+	DisableDNS bool `yaml:"disableDNS"`
 	// list of DNS local servers
 	// when list is empty, parsed from /etc/resolv.conf
 	DNSServers []net.IP `yaml:"-"`