Improve implementation around config (#1122)

* refactor config

* fix saas config

* feat(config): scanmodule for each server in config.toml

* feat(config): enable to specify containersOnly in config.toml

* add new keys of config.toml to discover.go

* fix summary output, logging

config/syslogconf.go

@@ -0,0 +1,129 @@
+package config
+
+import (
+	"errors"
+	"log/syslog"
+
+	"github.com/asaskevich/govalidator"
+	"golang.org/x/xerrors"
+)
+
+// SyslogConf is syslog config
+type SyslogConf struct {
+	Protocol string `json:"-"`
+	Host     string `valid:"host" json:"-"`
+	Port     string `valid:"port" json:"-"`
+	Severity string `json:"-"`
+	Facility string `json:"-"`
+	Tag      string `json:"-"`
+	Verbose  bool   `json:"-"`
+}
+
+// Validate validates configuration
+func (c *SyslogConf) Validate() (errs []error) {
+	if !Conf.ToSyslog {
+		return nil
+	}
+	//  If protocol is empty, it will connect to the local syslog server.
+	if len(c.Protocol) > 0 && c.Protocol != "tcp" && c.Protocol != "udp" {
+		errs = append(errs, errors.New(`syslog.protocol must be "tcp" or "udp"`))
+	}
+
+	// Default port: 514
+	if c.Port == "" {
+		c.Port = "514"
+	}
+
+	if _, err := c.GetSeverity(); err != nil {
+		errs = append(errs, err)
+	}
+
+	if _, err := c.GetFacility(); err != nil {
+		errs = append(errs, err)
+	}
+
+	if _, err := govalidator.ValidateStruct(c); err != nil {
+		errs = append(errs, err)
+	}
+	return errs
+}
+
+// GetSeverity gets severity
+func (c *SyslogConf) GetSeverity() (syslog.Priority, error) {
+	if c.Severity == "" {
+		return syslog.LOG_INFO, nil
+	}
+
+	switch c.Severity {
+	case "emerg":
+		return syslog.LOG_EMERG, nil
+	case "alert":
+		return syslog.LOG_ALERT, nil
+	case "crit":
+		return syslog.LOG_CRIT, nil
+	case "err":
+		return syslog.LOG_ERR, nil
+	case "warning":
+		return syslog.LOG_WARNING, nil
+	case "notice":
+		return syslog.LOG_NOTICE, nil
+	case "info":
+		return syslog.LOG_INFO, nil
+	case "debug":
+		return syslog.LOG_DEBUG, nil
+	default:
+		return -1, xerrors.Errorf("Invalid severity: %s", c.Severity)
+	}
+}
+
+// GetFacility gets facility
+func (c *SyslogConf) GetFacility() (syslog.Priority, error) {
+	if c.Facility == "" {
+		return syslog.LOG_AUTH, nil
+	}
+
+	switch c.Facility {
+	case "kern":
+		return syslog.LOG_KERN, nil
+	case "user":
+		return syslog.LOG_USER, nil
+	case "mail":
+		return syslog.LOG_MAIL, nil
+	case "daemon":
+		return syslog.LOG_DAEMON, nil
+	case "auth":
+		return syslog.LOG_AUTH, nil
+	case "syslog":
+		return syslog.LOG_SYSLOG, nil
+	case "lpr":
+		return syslog.LOG_LPR, nil
+	case "news":
+		return syslog.LOG_NEWS, nil
+	case "uucp":
+		return syslog.LOG_UUCP, nil
+	case "cron":
+		return syslog.LOG_CRON, nil
+	case "authpriv":
+		return syslog.LOG_AUTHPRIV, nil
+	case "ftp":
+		return syslog.LOG_FTP, nil
+	case "local0":
+		return syslog.LOG_LOCAL0, nil
+	case "local1":
+		return syslog.LOG_LOCAL1, nil
+	case "local2":
+		return syslog.LOG_LOCAL2, nil
+	case "local3":
+		return syslog.LOG_LOCAL3, nil
+	case "local4":
+		return syslog.LOG_LOCAL4, nil
+	case "local5":
+		return syslog.LOG_LOCAL5, nil
+	case "local6":
+		return syslog.LOG_LOCAL6, nil
+	case "local7":
+		return syslog.LOG_LOCAL7, nil
+	default:
+		return -1, xerrors.Errorf("Invalid facility: %s", c.Facility)
+	}
+}