/* * 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 dnstap import ( "io" "log" "os" "github.com/farsightsec/golang-framestream" ) // FrameStreamOutput implements a dnstap Output to an io.Writer. type FrameStreamOutput struct { outputChannel chan []byte wait chan bool enc *framestream.Encoder } // NewFrameStreamOutput creates a FrameStreamOutput writing dnstap data to // the given io.Writer. func NewFrameStreamOutput(w io.Writer) (o *FrameStreamOutput, err error) { o = new(FrameStreamOutput) o.outputChannel = make(chan []byte, outputChannelSize) o.enc, err = framestream.NewEncoder(w, &framestream.EncoderOptions{ContentType: FSContentType}) if err != nil { return } o.wait = make(chan bool) return } // NewFrameStreamOutputFromFilename creates a file with the namee fname, // truncates it if it exists, and returns a FrameStreamOutput writing to // the newly created or truncated file. func NewFrameStreamOutputFromFilename(fname string) (o *FrameStreamOutput, err error) { if fname == "" || fname == "-" { return NewFrameStreamOutput(os.Stdout) } w, err := os.Create(fname) if err != nil { return } return NewFrameStreamOutput(w) } // GetOutputChannel returns the channel on which the FrameStreamOutput accepts // data. // // GetOutputData satisfies the dnstap Output interface. func (o *FrameStreamOutput) GetOutputChannel() chan []byte { return o.outputChannel } // RunOutputLoop processes data received on the channel returned by // GetOutputChannel, returning after the CLose method is called. // If there is an error writing to the Output's writer, RunOutputLoop() // logs a fatal error exits the program. // // RunOutputLoop satisfies the dnstap Output interface. func (o *FrameStreamOutput) RunOutputLoop() { for frame := range o.outputChannel { if _, err := o.enc.Write(frame); err != nil { log.Fatalf("framestream.Encoder.Write() failed: %s\n", err) break } } close(o.wait) } // Close closes the channel returned from GetOutputChannel, and flushes // all pending output. // // Close satisifies the dnstap Output interface. func (o *FrameStreamOutput) Close() { close(o.outputChannel) <-o.wait o.enc.Flush() o.enc.Close() }