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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2022 WireGuard LLC. All Rights Reserved.
*/
package tuntest
import (
"encoding/binary"
"io"
"net/netip"
"os"
"golang.zx2c4.com/wireguard/tun"
)
func Ping(dst, src netip.Addr) []byte {
localPort := uint16(1337)
seq := uint16(0)
payload := make([]byte, 4)
binary.BigEndian.PutUint16(payload[0:], localPort)
binary.BigEndian.PutUint16(payload[2:], seq)
return genICMPv4(payload, dst, src)
}
// Checksum is the "internet checksum" from https://tools.ietf.org/html/rfc1071.
func checksum(buf []byte, initial uint16) uint16 {
v := uint32(initial)
for i := 0; i < len(buf)-1; i += 2 {
v += uint32(binary.BigEndian.Uint16(buf[i:]))
}
if len(buf)%2 == 1 {
v += uint32(buf[len(buf)-1]) << 8
}
for v > 0xffff {
v = (v >> 16) + (v & 0xffff)
}
return ^uint16(v)
}
func genICMPv4(payload []byte, dst, src netip.Addr) []byte {
const (
icmpv4ProtocolNumber = 1
icmpv4Echo = 8
icmpv4ChecksumOffset = 2
icmpv4Size = 8
ipv4Size = 20
ipv4TotalLenOffset = 2
ipv4ChecksumOffset = 10
ttl = 65
headerSize = ipv4Size + icmpv4Size
)
pkt := make([]byte, headerSize+len(payload))
ip := pkt[0:ipv4Size]
icmpv4 := pkt[ipv4Size : ipv4Size+icmpv4Size]
// https://tools.ietf.org/html/rfc792
icmpv4[0] = icmpv4Echo // type
icmpv4[1] = 0 // code
chksum := ^checksum(icmpv4, checksum(payload, 0))
binary.BigEndian.PutUint16(icmpv4[icmpv4ChecksumOffset:], chksum)
// https://tools.ietf.org/html/rfc760 section 3.1
length := uint16(len(pkt))
ip[0] = (4 << 4) | (ipv4Size / 4)
binary.BigEndian.PutUint16(ip[ipv4TotalLenOffset:], length)
ip[8] = ttl
ip[9] = icmpv4ProtocolNumber
copy(ip[12:], src.AsSlice())
copy(ip[16:], dst.AsSlice())
chksum = ^checksum(ip[:], 0)
binary.BigEndian.PutUint16(ip[ipv4ChecksumOffset:], chksum)
copy(pkt[headerSize:], payload)
return pkt
}
type ChannelTUN struct {
Inbound chan []byte // incoming packets, closed on TUN close
Outbound chan []byte // outbound packets, blocks forever on TUN close
closed chan struct{}
events chan tun.Event
tun chTun
}
func NewChannelTUN() *ChannelTUN {
c := &ChannelTUN{
Inbound: make(chan []byte),
Outbound: make(chan []byte),
closed: make(chan struct{}),
events: make(chan tun.Event, 1),
}
c.tun.c = c
c.events <- tun.EventUp
return c
}
func (c *ChannelTUN) TUN() tun.Device {
return &c.tun
}
type chTun struct {
c *ChannelTUN
}
func (t *chTun) File() *os.File { return nil }
func (t *chTun) Read(data []byte, offset int) (int, error) {
select {
case <-t.c.closed:
return 0, os.ErrClosed
case msg := <-t.c.Outbound:
return copy(data[offset:], msg), nil
}
}
// Write is called by the wireguard device to deliver a packet for routing.
func (t *chTun) Write(data []byte, offset int) (int, error) {
if offset == -1 {
close(t.c.closed)
close(t.c.events)
return 0, io.EOF
}
msg := make([]byte, len(data)-offset)
copy(msg, data[offset:])
select {
case <-t.c.closed:
return 0, os.ErrClosed
case t.c.Inbound <- msg:
return len(data) - offset, nil
}
}
const DefaultMTU = 1420
func (t *chTun) Flush() error { return nil }
func (t *chTun) MTU() (int, error) { return DefaultMTU, nil }
func (t *chTun) Name() (string, error) { return "loopbackTun1", nil }
func (t *chTun) Events() chan tun.Event { return t.c.events }
func (t *chTun) Close() error {
t.Write(nil, -1)
return nil
}
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