tap.go

/*
GoVPN -- simple secure free software virtual private network daemon
Copyright (C) 2014-2015 Sergey Matveev <stargrave@stargrave.org>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

package govpn

import (
	"io"
	"log"

	"golang.org/x/crypto/poly1305"
)

type TAP struct {
	Name  string
	dev   io.ReadWriter
	buf   []byte
	sink  chan []byte
	ready chan struct{}
}

func NewTAP(ifaceName string) (*TAP, error) {
	maxIfacePktSize := MTU - poly1305.TagSize - NonceSize
	tapRaw, err := newTAPer(ifaceName)
	if err != nil {
		return nil, err
	}
	tap := TAP{
		Name:  ifaceName,
		dev:   tapRaw,
		buf:   make([]byte, maxIfacePktSize),
		sink:  make(chan []byte),
		ready: make(chan struct{}),
	}
	go func() {
		var n int
		var err error
		for {
			<-tap.ready
			n, err = tap.dev.Read(tap.buf)
			if err != nil {
				panic(err)
			}
			tap.sink <- tap.buf[:n]
		}
	}()
	return &tap, nil
}

func (t *TAP) Write(data []byte) {
	if _, err := t.dev.Write(data); err != nil {
		log.Println("Error writing to iface: ", err)
	}
}