water/README.md

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# water
`water` is a native Go library for [TUN/TAP](http://en.wikipedia.org/wiki/TUN/TAP) interfaces.
`water` is designed to be simple and efficient. It
* wraps almost only syscalls and uses only Go standard types;
* exposes standard interfaces; plays well with standard packages like `io`, `bufio`, etc..
* does not handle memory management (allocating/destructing slice). It's up to user to decide whether/how to reuse buffers.
~~`water/waterutil` has some useful functions to interpret MAC frame headers and IP packet headers. It also contains some constants such as protocol numbers and ethernet frame types.~~
See https://github.com/songgao/packets for functions for parsing various packets.
## Supported Platforms
* Linux
* macOS (point-to-point TUN only)
## Installation
```
go get -u github.com/songgao/water
go get -u github.com/songgao/water/waterutil
```
## Documentation
[http://godoc.org/github.com/songgao/water](http://godoc.org/github.com/songgao/water)
## Example
### TAP on Linux:
```go
package main
import (
"log"
"github.com/songgao/packets/ethernet"
"github.com/songgao/water"
)
func main() {
ifce, err := water.NewTAP("O_O")
if err != nil {
log.Fatal(err)
}
var frame ethernet.Frame
for {
frame.Resize(1500)
n, err := ifce.Read([]byte(frame))
if err != nil {
log.Fatal(err)
}
frame = frame[:n]
log.Printf("Dst: %s\n", frame.Destination())
log.Printf("Src: %s\n", frame.Source())
log.Printf("Ethertype: % x\n", frame.Ethertype())
log.Printf("Payload: % x\n", frame.Payload())
}
}
```
This piece of code creates a `TAP` interface, and prints some header information for every frame. After pull up the `main.go`, you'll need to bring up the interface and assign an IP address. All of these need root permission.
```bash
sudo go run main.go
```
In a new terminal:
```bash
sudo ip addr add 10.1.0.10/24 dev O_O
sudo ip link set dev O_O up
```
Wait until the output `main.go` terminal, try sending some ICMP broadcast message:
```bash
ping -c1 -b 10.1.0.255
```
You'll see output containing the IPv4 ICMP frame:
```
2016/10/24 03:18:16 Dst: ff:ff:ff:ff:ff:ff
2016/10/24 03:18:16 Src: 72:3c:fc:29:1c:6f
2016/10/24 03:18:16 Ethertype: 08 00
2016/10/24 03:18:16 Payload: 45 00 00 54 00 00 40 00 40 01 25 9f 0a 01 00 0a 0a 01 00 ff 08 00 01 c1 08 49 00 01 78 7d 0d 58 00 00 00 00 a2 4c 07 00 00 00 00 00 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 34 35 36 37
```
### TUN on macOS
```go
package main
import (
"log"
"github.com/songgao/water"
)
func main() {
ifce, err := water.NewTUN("")
if err != nil {
log.Fatal(err)
}
log.Printf("Interface Name: %s\n", ifce.Name())
packet := make([]byte, 2000)
for {
n, err := ifce.Read(packet)
if err != nil {
log.Fatal(err)
}
log.Printf("Packet Received: % x\n", packet[:n])
}
}
```
Run it!
```bash
$ sudo go run main.go
```
This is a point-to-point only interface. Use `ifconfig` to see its attributes. You need to bring it up and assign IP addresses (apparently replace `utun2` if needed):
```bash
$ sudo ifconfig utun2 10.1.0.10 10.1.0.20 up
```
Now send some ICMP packets to the interface:
```bash
$ ping 10.1.0.20
```
You'd see the ICMP packets printed out:
```
2016/10/23 20:21:53 Interface Name: utun2
2016/10/23 20:22:40 Packet Received: 00 00 00 02 45 00 00 54 4a 2e 00 00 40 01 1c 5c 0a 01 00 0a 0a 01 00 14 08 00 31 51 f0 f9 00 00 58 0d 7e 80 00 03 14 21 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 34 35 36 37
```
## TODO
* tuntaposx for TAP on Darwin
## LICENSE
[BSD 3-Clause License](http://opensource.org/licenses/BSD-3-Clause)
## Alternatives
`tuntap`: [https://code.google.com/p/tuntap/](https://code.google.com/p/tuntap/)