chore(internal/providers): simplify OpenVPN config building

internal/provider/mullvad/openvpnconf.go

@@ -1,8 +1,6 @@
 package mullvad
 
 import (
-	"strconv"
-
 	"github.com/qdm12/gluetun/internal/configuration/settings"
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/models"
@@ -10,73 +8,21 @@ import (
 )
 
 func (m *Mullvad) BuildConf(connection models.Connection,
-	settings settings.OpenVPN) (lines []string, err error) {
-	if len(settings.Ciphers) == 0 {
-		settings.Ciphers = []string{constants.AES256cbc, constants.AES128gcm}
+	settings settings.OpenVPN) (lines []string) {
+	//nolint:gomnd
+	providerSettings := utils.OpenVPNProviderSettings{
+		AuthUserPass: true,
+		Ciphers: []string{
+			constants.AES256cbc,
+			constants.AES128gcm,
+		},
+		Ping:          10,
+		RemoteCertTLS: true,
+		TLSCipher:     "TLS-DHE-RSA-WITH-AES-256-GCM-SHA384:TLS-DHE-RSA-WITH-AES-256-CBC-SHA",
+		SndBuf:        524288,
+		RcvBuf:        524288,
+		CA:            constants.MullvadCA,
+		UDPLines:      []string{"fast-io"},
 	}
-
-	lines = []string{
-		"client",
-		"nobind",
-		"tls-exit",
-		"dev " + settings.Interface,
-		"verb " + strconv.Itoa(*settings.Verbosity),
-		"auth-user-pass " + constants.OpenVPNAuthConf,
-
-		// Mullvad specific
-		"ping 10",
-		"remote-cert-tls server",
-		"sndbuf 524288",
-		"rcvbuf 524288",
-		"tls-cipher TLS-DHE-RSA-WITH-AES-256-GCM-SHA384:TLS-DHE-RSA-WITH-AES-256-CBC-SHA",
-
-		// Added constant values
-		"auth-nocache",
-		"mute-replay-warnings",
-		"pull-filter ignore \"auth-token\"", // prevent auth failed loops
-		"auth-retry nointeract",
-		"suppress-timestamps",
-
-		// Connection variables
-		connection.OpenVPNProtoLine(),
-		connection.OpenVPNRemoteLine(),
-	}
-
-	lines = append(lines, utils.CipherLines(settings.Ciphers, settings.Version)...)
-
-	if *settings.Auth != "" {
-		lines = append(lines, "auth "+*settings.Auth)
-	}
-
-	if connection.Protocol == constants.UDP {
-		lines = append(lines, "fast-io")
-		lines = append(lines, "explicit-exit-notify")
-	}
-
-	if !*settings.IPv6 {
-		lines = append(lines, `pull-filter ignore "route-ipv6"`)
-		lines = append(lines, `pull-filter ignore "ifconfig-ipv6"`)
-	}
-
-	if settings.ProcessUser != "root" {
-		lines = append(lines, "user "+settings.ProcessUser)
-		lines = append(lines, "persist-tun")
-		lines = append(lines, "persist-key")
-	}
-
-	if *settings.MSSFix > 0 {
-		lines = append(lines, "mssfix "+strconv.Itoa(int(*settings.MSSFix)))
-	}
-
-	if !*settings.IPv6 {
-		lines = append(lines, `pull-filter ignore "route-ipv6"`)
-		lines = append(lines, `pull-filter ignore "ifconfig-ipv6"`)
-	}
-
-	lines = append(lines, utils.WrapOpenvpnCA(
-		constants.MullvadCA)...)
-
-	lines = append(lines, "")
-
-	return lines, nil
+	return utils.OpenVPNConfig(providerSettings, connection, settings)
 }