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stun.go
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stun.go
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/*
* Copyright (C) 2021 The "MysteriumNetwork/node" Authors.
*
* 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 p2p
import (
"fmt"
"net"
"sync"
"time"
"github.com/pion/stun"
"github.com/rs/zerolog/log"
"github.com/mysteriumnetwork/node/config"
"github.com/mysteriumnetwork/node/eventbus"
"github.com/mysteriumnetwork/node/identity"
"github.com/mysteriumnetwork/node/requests/resolver"
)
// AppTopicSTUN represents the STUN detection topic.
const AppTopicSTUN = "STUN detection"
// STUNDetectionStatus represents information about detected NAT type using STUN servers.
type STUNDetectionStatus struct {
Identity string
NATType string
}
func stunPorts(identity identity.Identity, eventBus eventbus.Publisher, localPorts ...int) (remotePorts []int) {
serverList := config.GetStringSlice(config.FlagSTUNservers)
if len(serverList) == 0 {
return localPorts
}
m := make(map[int]int)
mu := sync.Mutex{}
wg := sync.WaitGroup{}
wg.Add(len(localPorts))
for _, p := range localPorts {
go func(p int) {
defer wg.Done()
resp := multiServerSTUN(serverList, p, 2)
mu.Lock()
defer mu.Unlock()
natType := "unknown"
for _, port := range resp {
if m[p] != 0 {
switch {
case m[p] == port && p == port:
natType = "full"
case m[p] == port:
natType = "restricted"
default:
natType = "fail"
}
}
if port != 0 {
m[p] = port
}
}
if natType == "fail" {
delete(m, p)
}
if eventBus != nil {
eventBus.Publish(AppTopicSTUN, STUNDetectionStatus{
Identity: identity.Address,
NATType: natType,
})
}
}(p)
}
wg.Wait()
for _, p := range localPorts {
if port, ok := m[p]; ok {
remotePorts = append(remotePorts, port)
} else {
remotePorts = append(remotePorts, p)
}
}
return remotePorts
}
func multiServerSTUN(servers []string, p, limit int) (respPort []int) {
conn, err := net.ListenUDP("udp4", &net.UDPAddr{Port: p})
if err != nil {
log.Error().Err(err).Msg("failed to listen UDP address for STUN server")
return nil
}
if err := conn.SetDeadline(time.Now().Add(2 * time.Second)); err != nil {
log.Error().Err(err).Msg("failed to set connection deadline for STUN server")
return nil
}
defer conn.Close()
ch := make(chan int, len(servers))
wg := sync.WaitGroup{}
wg.Add(len(servers))
go func() {
wg.Wait()
close(ch)
}()
for _, server := range servers {
go func(server string) {
defer wg.Done()
port, err := stunPort(conn, server)
if err != nil {
log.Trace().Err(err).Msg("failed to get public UDP port from STUN server")
return
}
ch <- port
}(server)
}
for p := range ch {
respPort = append(respPort, p)
if len(respPort) == limit {
return respPort
}
}
return respPort
}
func stunPort(conn *net.UDPConn, server string) (remotePort int, err error) {
host, port, err := net.SplitHostPort(server)
if err != nil {
return 0, fmt.Errorf("failed to parse STUN server address: %w", err)
}
if addrs := resolver.FetchDNSFromCache(host); len(addrs) > 0 {
server = net.JoinHostPort(addrs[0], port)
}
serverAddr, err := net.ResolveUDPAddr("udp", server)
if err != nil {
return 0, fmt.Errorf("failed to resolve STUN server address: %w", err)
}
resolver.CacheDNSRecord(host, []string{serverAddr.IP.String()})
m := stun.MustBuild(stun.TransactionID, stun.BindingRequest)
if _, err = conn.WriteToUDP(m.Raw, serverAddr); err != nil {
return 0, fmt.Errorf("failed to send binding request to STUN server: %w", err)
}
msg := make([]byte, 1024)
n, _, err := conn.ReadFromUDP(msg)
if err != nil {
return 0, fmt.Errorf("failed to read message from STUN server: %w", err)
}
msg = msg[:n]
if !stun.IsMessage(msg) {
return 0, fmt.Errorf("not correct response from STUN server")
}
resp := &stun.Message{Raw: msg}
if err := resp.Decode(); err != nil {
return 0, fmt.Errorf("failed to decode STUN server message: %w", err)
}
var xorAddr stun.XORMappedAddress
if err := xorAddr.GetFrom(resp); err != nil {
return 0, fmt.Errorf("failed to decode STUN server message: %w", err)
}
return xorAddr.Port, nil
}