forked from subutai-io/p2p
/
discover.go
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/
discover.go
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// Copyright 2013, Cong Ding. All rights reserved.
//
// 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.
//
// Author: Cong Ding <dinggnu@gmail.com>
package stun
import (
"errors"
"fmt"
"net"
)
// Padding the length of the byte slice to multiple of 4.
func padding(bytes []byte) []byte {
length := uint16(len(bytes))
return append(bytes, make([]byte, align(length)-length)...)
}
// Align the uint16 number to the smallest multiple of 4, which is larger than
// or equal to the uint16 number.
func align(n uint16) uint16 {
return (n + 3) & 0xfffc
}
func sendBindingReq(serverAddr string, c *Client) (*packet, string, error) {
var conn net.Conn
var err error
var saddr *net.UDPAddr
var laddr *net.UDPAddr
var flag bool = true
laddr, err = net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", c.LocalAddr, c.LocalPort))
flag = flag && (err == nil)
saddr, err = net.ResolveUDPAddr("udp", serverAddr)
flag = flag && (err == nil)
if !flag {
conn, err = net.Dial("udp", serverAddr)
if err != nil {
return nil, "", err
}
} else {
conn, err = net.DialUDP("udp", laddr, saddr)
if err != nil {
return nil, "", err
}
}
// Construct packet.
packet := newPacket()
packet.types = type_BINDING_REQUEST
attribute := newSoftwareAttribute(packet, DefaultSoftwareName)
packet.addAttribute(*attribute)
attribute = newFingerprintAttribute(packet)
packet.addAttribute(*attribute)
// Send packet.
localAddr := conn.LocalAddr().String()
packet, err = packet.send(conn)
if err != nil {
return nil, "", err
}
err = conn.Close()
return packet, localAddr, err
}
func sendChangeReq(serverAddr string, changeIP bool, changePort bool, c *Client) (*packet, error) {
var conn net.Conn
var err error
var saddr *net.UDPAddr
var laddr *net.UDPAddr
var flag bool = true
laddr, err = net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", c.LocalAddr, c.LocalPort))
flag = flag && (err == nil)
saddr, err = net.ResolveUDPAddr("udp", serverAddr)
flag = flag && (err == nil)
if !flag {
conn, err = net.Dial("udp", serverAddr)
if err != nil {
return nil, err
}
} else {
conn, err = net.DialUDP("udp", laddr, saddr)
if err != nil {
return nil, err
}
}
// Construct packet.
packet := newPacket()
packet.types = type_BINDING_REQUEST
attribute := newSoftwareAttribute(packet, DefaultSoftwareName)
packet.addAttribute(*attribute)
attribute = newChangeReqAttribute(packet, changeIP, changePort)
packet.addAttribute(*attribute)
attribute = newFingerprintAttribute(packet)
packet.addAttribute(*attribute)
// Send packet.
packet, err = packet.send(conn)
if err != nil {
return nil, err
}
err = conn.Close()
return packet, err
}
func test1(serverAddr string, c *Client) (*packet, string, bool, *Host, error) {
packet, localAddr, err := sendBindingReq(serverAddr, c)
if err != nil {
return nil, "", false, nil, err
}
if packet == nil {
return nil, "", false, nil, nil
}
// RFC 3489 doesn't require the server return XOR mapped address.
hostMappedAddr := packet.xorMappedAddr()
if hostMappedAddr == nil {
hostMappedAddr = packet.mappedAddr()
if hostMappedAddr == nil {
return nil, "", false, nil, errors.New("No mapped address.")
}
}
hostChangedAddr := packet.changedAddr()
if hostChangedAddr == nil {
return nil, "", false, nil, errors.New("No changed address.")
}
changeAddr := hostChangedAddr.TransportAddr()
identical := localAddr == hostMappedAddr.TransportAddr()
return packet, changeAddr, identical, hostMappedAddr, nil
}
func test2(serverAddr string, c *Client) (*packet, error) {
return sendChangeReq(serverAddr, true, true, c)
}
func test3(serverAddr string, c *Client) (*packet, error) {
return sendChangeReq(serverAddr, false, true, c)
}
// Follow RFC 3489 and RFC 5389.
// Figure 2: Flow for type discovery process (from RFC 3489).
// +--------+
// | Test |
// | I |
// +--------+
// |
// |
// V
// /\ /\
// N / \ Y / \ Y +--------+
// UDP <-------/Resp\--------->/ IP \------------->| Test |
// Blocked \ ? / \Same/ | II |
// \ / \? / +--------+
// \/ \/ |
// | N |
// | V
// V /\
// +--------+ Sym. N / \
// | Test | UDP <---/Resp\
// | II | Firewall \ ? /
// +--------+ \ /
// | \/
// V |Y
// /\ /\ |
// Symmetric N / \ +--------+ N / \ V
// NAT <--- / IP \<-----| Test |<--- /Resp\ Open
// \Same/ | I | \ ? / Internet
// \? / +--------+ \ /
// \/ \/
// |Y |Y
// | |
// | V
// | Full
// | Cone
// V /\
// +--------+ / \ Y
// | Test |------>/Resp\---->Restricted
// | III | \ ? /
// +--------+ \ /
// \/
// |N
// | Port
// +------>Restricted
func discover(c *Client) (NATType, *Host, error) {
packet, changeAddr, identical, host, err := test1(c.ServerAddr(), c)
if err != nil {
return NAT_ERROR, nil, err
}
if packet == nil {
return NAT_BLOCKED, nil, nil
}
packet, err = test2(c.ServerAddr(), c)
if err != nil {
return NAT_ERROR, host, err
}
if identical {
if packet == nil {
return NAT_SYMETRIC_UDP_FIREWALL, host, nil
}
return NAT_NONE, host, nil
}
if packet != nil {
return NAT_FULL, host, nil
}
packet, _, identical, _, err = test1(changeAddr, c)
if err != nil {
return NAT_ERROR, host, err
}
if packet == nil {
// It should be NAT_BLOCKED, but will be detected in the first
// step. So this will never happen.
return NAT_UNKNOWN, host, nil
}
if identical {
packet, err = test3(c.ServerAddr(), c)
if err != nil {
return NAT_ERROR, host, err
}
if packet == nil {
return NAT_PORT_RESTRICTED, host, nil
}
return NAT_RESTRICTED, host, nil
}
return NAT_SYMETRIC, host, nil
}