dissertation-2-code/tun/tun.go

package tun

import (
	"github.com/pkg/taptun"
	"io"
	"log"
	"mpbl3p/proxy"
	"net"
	"os"
	"strings"
	"sync"
	"time"
)

type SourceSink struct {
	tun        *taptun.Tun
	bufferSize int

	up   bool
	upMu sync.Mutex
}

func NewTun(namingScheme string, bufferSize int) (ss *SourceSink, err error) {
	ss = &SourceSink{}

	ss.tun, err = taptun.NewTun(namingScheme)
	if err != nil {
		return
	}

	ss.bufferSize = bufferSize

	ss.upMu.Lock()
	go func() {
		defer ss.upMu.Unlock()

		for {
			iface, err := net.InterfaceByName(ss.tun.String())
			if err != nil {
				panic(err)
			}
			if strings.Contains(iface.Flags.String(), "up") {
				log.Println("tun is up")
				ss.up = true
				return
			}
			time.Sleep(100 * time.Millisecond)
		}
	}()

	return
}

func (t *SourceSink) Source() (proxy.Packet, error) {
	if !t.up {
		t.upMu.Lock()
		t.upMu.Unlock()
	}

	buf := make([]byte, t.bufferSize)

	read, err := t.tun.Read(buf)
	if err != nil {
		return nil, err
	}

	if read == 0 {
		return nil, io.EOF
	}

	return proxy.SimplePacket(buf[:read]), nil
}

var good, bad float64

func (t *SourceSink) Sink(packet proxy.Packet) error {
	if !t.up {
		t.upMu.Lock()
		t.upMu.Unlock()
	}

	_, err := t.tun.Write(packet.Contents())
	if err != nil {
		switch err.(type) {
		case *os.PathError:
			bad += 1
			log.Printf("packet loss: %f%%\n", bad*100/(good+bad))
			return nil
		default:
			return err
		}
	}

	good += 1
	return nil
}