Add support for non-transparent framing of syslog messages (#5148)

plugins/inputs/syslog/framing.go

@@ -0,0 +1,64 @@
+package syslog
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Framing represents the framing technique we expect the messages to come.
+type Framing int
+
+const (
+	// OctetCounting indicates the transparent framing technique for syslog transport.
+	OctetCounting Framing = iota
+	// NonTransparent indicates the non-transparent framing technique for syslog transport.
+	NonTransparent
+)
+
+func (f Framing) String() string {
+	switch f {
+	case OctetCounting:
+		return "OCTET-COUNTING"
+	case NonTransparent:
+		return "NON-TRANSPARENT"
+	}
+	return ""
+}
+
+// UnmarshalTOML implements ability to unmarshal framing from TOML files.
+func (f *Framing) UnmarshalTOML(data []byte) (err error) {
+	return f.UnmarshalText(data)
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler
+func (f *Framing) UnmarshalText(data []byte) (err error) {
+	s := string(data)
+	switch strings.ToUpper(s) {
+	case `OCTET-COUNTING`:
+		fallthrough
+	case `"OCTET-COUNTING"`:
+		fallthrough
+	case `'OCTET-COUNTING'`:
+		*f = OctetCounting
+		return
+
+	case `NON-TRANSPARENT`:
+		fallthrough
+	case `"NON-TRANSPARENT"`:
+		fallthrough
+	case `'NON-TRANSPARENT'`:
+		*f = NonTransparent
+		return
+	}
+	*f = -1
+	return fmt.Errorf("unknown framing")
+}
+
+// MarshalText implements encoding.TextMarshaler
+func (f Framing) MarshalText() ([]byte, error) {
+	s := f.String()
+	if s != "" {
+		return []byte(s), nil
+	}
+	return nil, fmt.Errorf("unknown framing")
+}