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/*
* Copyright (c) 2013-2019 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"
"os"
"time"
)
// 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
reader Reader
log Logger
}
// 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) {
reader, err := NewReader(r, &ReaderOptions{
Bidirectional: bi,
Timeout: timeout,
})
if err != nil {
return nil, err
}
return &FrameStreamInput{
wait: make(chan bool),
reader: reader,
log: nullLogger{},
}, nil
}
// 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
}
return NewFrameStreamInput(file, false)
}
// SetLogger configures a logger for FrameStreamInput read error reporting.
func (input *FrameStreamInput) SetLogger(logger Logger) {
input.log = logger
}
// ReadInto reads data from the FrameStreamInput into the output channel.
//
// ReadInto satisfies the dnstap Input interface.
func (input *FrameStreamInput) ReadInto(output chan []byte) {
buf := make([]byte, MaxPayloadSize)
for {
n, err := input.reader.ReadFrame(buf)
if err == nil {
newbuf := make([]byte, n)
copy(newbuf, buf)
output <- newbuf
continue
}
if err != io.EOF {
input.log.Printf("FrameStreamInput: Read error: %v", err)
}
break
}
close(input.wait)
}
// Wait reeturns when ReadInto has finished.
//
// Wait satisfies the dnstap Input interface.
func (input *FrameStreamInput) Wait() {
<-input.wait
}
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