WIP: middleware/dnstap (#711)

middleware/dnstap add

vendor/github.com/farsightsec/golang-framestream/Decoder.go

@@ -0,0 +1,154 @@
+/*
+ * Copyright (c) 2014 by Farsight Security, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package framestream
+
+import (
+	"bufio"
+	"encoding/binary"
+	"io"
+)
+
+type DecoderOptions struct {
+	MaxPayloadSize uint32
+	ContentType    []byte
+	Bidirectional  bool
+}
+
+type Decoder struct {
+	buf     []byte
+	opt     DecoderOptions
+	reader  *bufio.Reader
+	writer  *bufio.Writer
+	stopped bool
+}
+
+func NewDecoder(r io.Reader, opt *DecoderOptions) (dec *Decoder, err error) {
+	if opt == nil {
+		opt = &DecoderOptions{}
+	}
+	if opt.MaxPayloadSize == 0 {
+		opt.MaxPayloadSize = DEFAULT_MAX_PAYLOAD_SIZE
+	}
+	dec = &Decoder{
+		buf:    make([]byte, opt.MaxPayloadSize),
+		opt:    *opt,
+		reader: bufio.NewReader(r),
+		writer: nil,
+	}
+
+	var cf ControlFrame
+	if opt.Bidirectional {
+		w, ok := r.(io.Writer)
+		if !ok {
+			return dec, ErrType
+		}
+		dec.writer = bufio.NewWriter(w)
+
+		// Read the ready control frame.
+		err = cf.DecodeTypeEscape(dec.reader, CONTROL_READY)
+		if err != nil {
+			return
+		}
+
+		// Check content type.
+		if !cf.MatchContentType(dec.opt.ContentType) {
+			return dec, ErrContentTypeMismatch
+		}
+
+		// Send the accept control frame.
+		accept := ControlAccept
+		accept.SetContentType(dec.opt.ContentType)
+		err = accept.EncodeFlush(dec.writer)
+		if err != nil {
+			return
+		}
+	}
+
+	// Read the start control frame.
+	err = cf.DecodeTypeEscape(dec.reader, CONTROL_START)
+	if err != nil {
+		return
+	}
+
+	// Check content type.
+	if !cf.MatchContentType(dec.opt.ContentType) {
+		return dec, ErrContentTypeMismatch
+	}
+
+	return
+}
+
+func (dec *Decoder) readFrame(frameLen uint32) (err error) {
+	// Enforce limits on frame size.
+	if frameLen > dec.opt.MaxPayloadSize {
+		err = ErrDataFrameTooLarge
+		return
+	}
+
+	// Read the frame.
+	n, err := io.ReadFull(dec.reader, dec.buf[0:frameLen])
+	if err != nil || uint32(n) != frameLen {
+		return
+	}
+	return
+}
+
+func (dec *Decoder) Decode() (frameData []byte, err error) {
+	if dec.stopped {
+		err = EOF
+		return
+	}
+
+	// Read the frame length.
+	var frameLen uint32
+	err = binary.Read(dec.reader, binary.BigEndian, &frameLen)
+	if err != nil {
+		return
+	}
+	if frameLen == 0 {
+		// This is a control frame.
+		var cf ControlFrame
+		err = cf.Decode(dec.reader)
+		if err != nil {
+			return
+		}
+		if cf.ControlType == CONTROL_STOP {
+			dec.stopped = true
+			if dec.opt.Bidirectional {
+				ff := &ControlFrame{ControlType: CONTROL_FINISH}
+				err = ff.EncodeFlush(dec.writer)
+				if err != nil {
+					return
+				}
+			}
+			return nil, EOF
+		}
+		if err != nil {
+			return nil, err
+		}
+
+	} else {
+		// This is a data frame.
+		err = dec.readFrame(frameLen)
+		if err != nil {
+			return
+		}
+		frameData = dec.buf[0:frameLen]
+	}
+
+	return
+}