/*
* Copyright (c) 2013-2014 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 dnstap
import (
"io"
"log"
"os"
"time"
"github.com/farsightsec/golang-framestream"
)
// MaxPayloadSize sets the upper limit on input Dnstap payload sizes. If an Input
// receives a Dnstap payload over this size limit, ReadInto will log an error and
// return.
//
// EDNS0 and DNS over TCP use 2 octets for DNS message size, imposing a maximum
// size of 65535 octets for the DNS message, which is the bulk of the data carried
// in a Dnstap message. Protobuf encoding overhead and metadata with some size
// guidance (e.g., identity and version being DNS strings, which have a maximum
// length of 255) add up to less than 1KB. The default 96KiB size of the buffer
// allows a bit over 30KB space for "extra" metadata.
//
var MaxPayloadSize uint32 = 96 * 1024
// A FrameStreamInput reads dnstap data from an io.ReadWriter.
type FrameStreamInput struct {
wait chan bool
decoder *framestream.Decoder
timeout time.Duration
}
// NewFrameStreamInput creates a FrameStreamInput reading data from the given
// io.ReadWriter. If bi is true, the input will use the bidirectional
// framestream protocol suitable for TCP and unix domain socket connections.
func NewFrameStreamInput(r io.ReadWriter, bi bool) (input *FrameStreamInput, err error) {
return NewFrameStreamInputTimeout(r, bi, 0)
}
// NewFrameStreamInputTimeout creates a FramestreamInput reading data from the
// given io.ReadWriter with a timeout applied to reading and (for bidirectional
// inputs) writing control messages.
func NewFrameStreamInputTimeout(r io.ReadWriter, bi bool, timeout time.Duration) (input *FrameStreamInput, err error) {
input = new(FrameStreamInput)
decoderOptions := framestream.DecoderOptions{
MaxPayloadSize: MaxPayloadSize,
ContentType: FSContentType,
Bidirectional: bi,
Timeout: timeout,
}
input.decoder, err = framestream.NewDecoder(r, &decoderOptions)
if err != nil {
return
}
input.wait = make(chan bool)
return
}
// NewFrameStreamInputFromFilename creates a FrameStreamInput reading from
// the named file.
func NewFrameStreamInputFromFilename(fname string) (input *FrameStreamInput, err error) {
file, err := os.Open(fname)
if err != nil {
return nil, err
}
input, err = NewFrameStreamInput(file, false)
return
}
// ReadInto reads data from the FrameStreamInput into the output channel.
//
// ReadInto satisfies the dnstap Input interface.
func (input *FrameStreamInput) ReadInto(output chan []byte) {
for {
buf, err := input.decoder.Decode()
if err != nil {
if err != io.EOF {
log.Printf("framestream.Decoder.Decode() failed: %s\n", err)
}
break
}
newbuf := make([]byte, len(buf))
copy(newbuf, buf)
output <- newbuf
}
close(input.wait)
}
// Wait reeturns when ReadInto has finished.
//
// Wait satisfies the dnstap Input interface.
func (input *FrameStreamInput) Wait() {
<-input.wait
}