Fix: only use Openvpn fast-io when using UDP

internal/provider/mullvad/openvpnconf.go

@@ -30,7 +30,6 @@ func (m *Mullvad) BuildConf(connection models.OpenVPNConnection,
 		"sndbuf 524288",
 		"rcvbuf 524288",
 		"tls-cipher TLS-DHE-RSA-WITH-AES-256-GCM-SHA384:TLS-DHE-RSA-WITH-AES-256-CBC-SHA",
-		"fast-io",
 		"script-security 2",
 
 		// Added constant values
@@ -53,6 +52,10 @@ func (m *Mullvad) BuildConf(connection models.OpenVPNConnection,
 		lines = append(lines, "auth "+settings.Auth)
 	}
 
+	if connection.Protocol == constants.UDP {
+		lines = append(lines, "fast-io")
+	}
+
 	if settings.Provider.ExtraConfigOptions.OpenVPNIPv6 {
 		lines = append(lines, "tun-ipv6")
 	} else {

internal/provider/nordvpn/openvpnconf.go

@@ -38,7 +38,6 @@ func (n *Nordvpn) BuildConf(connection models.OpenVPNConnection,
 		"mssfix " + strconv.Itoa(int(settings.MSSFix)),
 		"reneg-sec 0",
 		"comp-lzo no",
-		"fast-io",
 		"key-direction 1",
 		"ping 15",
 		"ping-restart 0",
@@ -60,6 +59,10 @@ func (n *Nordvpn) BuildConf(connection models.OpenVPNConnection,
 		"auth " + settings.Auth,
 	}
 
+	if connection.Protocol == constants.UDP {
+		lines = append(lines, "fast-io")
+	}
+
 	if !settings.Root {
 		lines = append(lines, "user "+username)
 	}

internal/provider/protonvpn/openvpnconf.go

@@ -37,7 +37,6 @@ func (p *Protonvpn) BuildConf(connection models.OpenVPNConnection,
 		"tun-mtu-extra 32",
 		"mssfix " + strconv.Itoa(int(settings.MSSFix)),
 		"reneg-sec 0",
-		"fast-io",
 		"key-direction 1",
 		"pull",
 		"comp-lzo no",
@@ -59,6 +58,10 @@ func (p *Protonvpn) BuildConf(connection models.OpenVPNConnection,
 		"auth " + settings.Auth,
 	}
 
+	if connection.Protocol == constants.UDP {
+		lines = append(lines, "fast-io")
+	}
+
 	if !settings.Root {
 		lines = append(lines, "user "+username)
 	}

internal/provider/surfshark/openvpnconf.go

@@ -39,7 +39,6 @@ func (s *Surfshark) BuildConf(connection models.OpenVPNConnection,
 		"tun-mtu-extra 32",
 		"mssfix " + strconv.Itoa(int(settings.MSSFix)),
 		"reneg-sec 0",
-		"fast-io",
 		"key-direction 1",
 		"script-security 2",
 		"ping-restart 0",

internal/provider/torguard/openvpnconf.go

@@ -37,7 +37,6 @@ func (t *Torguard) BuildConf(connection models.OpenVPNConnection,
 		"tun-mtu-extra 32",
 		"mssfix " + strconv.Itoa(int(settings.MSSFix)),
 		"reneg-sec 0",
-		"fast-io",
 		"key-direction 1",
 		"script-security 2",
 		"ncp-disable",
@@ -67,6 +66,10 @@ func (t *Torguard) BuildConf(connection models.OpenVPNConnection,
 		lines = append(lines, "user "+username)
 	}
 
+	if connection.Protocol == constants.UDP {
+		lines = append(lines, "fast-io")
+	}
+
 	lines = append(lines, utils.WrapOpenvpnCA(
 		constants.TorguardCertificate)...)
 	lines = append(lines, utils.WrapOpenvpnTLSAuth(