Maint: split custom config files in openvpn/custom

internal/openvpn/custom/extract.go

@@ -0,0 +1,139 @@
+package custom
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"strconv"
+	"strings"
+
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gluetun/internal/models"
+)
+
+var (
+	errRemoteLineNotFound = errors.New("remote line not found")
+)
+
+// extractConnectionFromLines always takes the first remote line only.
+func extractConnectionFromLines(lines []string) (
+	connection models.OpenVPNConnection, err error) {
+	for i, line := range lines {
+		newConnectionData, err := extractConnectionFromLine(line)
+		if err != nil {
+			return connection, fmt.Errorf("on line %d: %w", i+1, err)
+		}
+		connection.UpdateEmptyWith(newConnectionData)
+
+		if connection.Protocol != "" && connection.IP != nil {
+			break
+		}
+	}
+
+	if connection.IP == nil {
+		return connection, errRemoteLineNotFound
+	}
+
+	if connection.Protocol == "" {
+		connection.Protocol = constants.UDP
+	}
+
+	if connection.Port == 0 {
+		connection.Port = 1194
+		if connection.Protocol == constants.TCP {
+			connection.Port = 443
+		}
+	}
+
+	return connection, nil
+}
+
+var (
+	errExtractProto  = errors.New("failed extracting protocol from proto line")
+	errExtractRemote = errors.New("failed extracting protocol from remote line")
+)
+
+func extractConnectionFromLine(line string) (
+	connection models.OpenVPNConnection, err error) {
+	switch {
+	case strings.HasPrefix(line, "proto "):
+		connection.Protocol, err = extractProto(line)
+		if err != nil {
+			return connection, fmt.Errorf("%w: %s", errExtractProto, err)
+		}
+
+	// only take the first remote line
+	case strings.HasPrefix(line, "remote ") && connection.IP == nil:
+		connection.IP, connection.Port, connection.Protocol, err = extractRemote(line)
+		if err != nil {
+			return connection, fmt.Errorf("%w: %s", errExtractRemote, err)
+		}
+	}
+
+	return connection, nil
+}
+
+var (
+	errProtoLineFieldsCount = errors.New("proto line has not 2 fields as expected")
+	errProtocolNotSupported = errors.New("network protocol not supported")
+)
+
+func extractProto(line string) (protocol string, err error) {
+	fields := strings.Fields(line)
+	if len(fields) != 2 { //nolint:gomnd
+		return "", fmt.Errorf("%w: %s", errProtoLineFieldsCount, line)
+	}
+
+	switch fields[1] {
+	case "tcp", "udp":
+	default:
+		return "", fmt.Errorf("%w: %s", errProtocolNotSupported, fields[1])
+	}
+
+	return fields[1], nil
+}
+
+var (
+	errRemoteLineFieldsCount = errors.New("remote line has not 2 fields as expected")
+	errHostNotIP             = errors.New("host is not an an IP address")
+	errPortNotValid          = errors.New("port is not valid")
+)
+
+func extractRemote(line string) (ip net.IP, port uint16,
+	protocol string, err error) {
+	fields := strings.Fields(line)
+	n := len(fields)
+
+	if n < 2 || n > 4 {
+		return nil, 0, "", fmt.Errorf("%w: %s", errRemoteLineFieldsCount, line)
+	}
+
+	host := fields[1]
+	ip = net.ParseIP(host)
+	if ip == nil {
+		return nil, 0, "", fmt.Errorf("%w: %s", errHostNotIP, host)
+		// TODO resolve hostname once there is an option to allow it through
+		// the firewall before the VPN is up.
+	}
+
+	if n > 2 { //nolint:gomnd
+		portInt, err := strconv.Atoi(fields[2])
+		if err != nil {
+			return nil, 0, "", fmt.Errorf("%w: %s", errPortNotValid, line)
+		} else if portInt < 1 || portInt > 65535 {
+			return nil, 0, "", fmt.Errorf("%w: not between 1 and 65535: %d", errPortNotValid, portInt)
+		}
+		port = uint16(portInt)
+	}
+
+	if n > 3 { //nolint:gomnd
+		switch fields[3] {
+		case "tcp", "udp":
+			protocol = fields[3]
+		default:
+			return nil, 0, "", fmt.Errorf("%w: %s", errProtocolNotSupported, fields[3])
+		}
+	}
+
+	return ip, port, protocol, nil
+}