syncthing/lib/nat/service.go
2019-02-02 12:16:27 +01:00

334 lines
9.0 KiB
Go

// Copyright (C) 2015 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
package nat
import (
"fmt"
"hash/fnv"
"math/rand"
"net"
stdsync "sync"
"time"
"github.com/syncthing/syncthing/lib/config"
"github.com/syncthing/syncthing/lib/protocol"
"github.com/syncthing/syncthing/lib/sync"
)
// Service runs a loop for discovery of IGDs (Internet Gateway Devices) and
// setup/renewal of a port mapping.
type Service struct {
id protocol.DeviceID
cfg *config.Wrapper
stop chan struct{}
mappings []*Mapping
timer *time.Timer
mut sync.RWMutex
}
func NewService(id protocol.DeviceID, cfg *config.Wrapper) *Service {
return &Service{
id: id,
cfg: cfg,
timer: time.NewTimer(0),
mut: sync.NewRWMutex(),
}
}
func (s *Service) Serve() {
announce := stdsync.Once{}
s.mut.Lock()
s.timer.Reset(0)
s.stop = make(chan struct{})
s.mut.Unlock()
for {
select {
case <-s.timer.C:
if found := s.process(); found != -1 {
announce.Do(func() {
suffix := "s"
if found == 1 {
suffix = ""
}
l.Infoln("Detected", found, "NAT service"+suffix)
})
}
case <-s.stop:
s.timer.Stop()
s.mut.RLock()
for _, mapping := range s.mappings {
mapping.clearAddresses()
}
s.mut.RUnlock()
return
}
}
}
func (s *Service) process() int {
// toRenew are mappings which are due for renewal
// toUpdate are the remaining mappings, which will only be updated if one of
// the old IGDs has gone away, or a new IGD has appeared, but only if we
// actually need to perform a renewal.
var toRenew, toUpdate []*Mapping
renewIn := time.Duration(s.cfg.Options().NATRenewalM) * time.Minute
if renewIn == 0 {
// We always want to do renewal so lets just pick a nice sane number.
renewIn = 30 * time.Minute
}
s.mut.RLock()
for _, mapping := range s.mappings {
if mapping.expires.Before(time.Now()) {
toRenew = append(toRenew, mapping)
} else {
toUpdate = append(toUpdate, mapping)
mappingRenewIn := time.Until(mapping.expires)
if mappingRenewIn < renewIn {
renewIn = mappingRenewIn
}
}
}
// Reset the timer while holding the lock, because of the following race:
// T1: process acquires lock
// T1: process checks the mappings and gets next renewal time in 30m
// T2: process releases the lock
// T2: NewMapping acquires the lock
// T2: NewMapping adds mapping
// T2: NewMapping releases the lock
// T2: NewMapping resets timer to 1s
// T1: process resets timer to 30
s.timer.Reset(renewIn)
s.mut.RUnlock()
// Don't do anything, unless we really need to renew
if len(toRenew) == 0 {
return -1
}
nats := discoverAll(time.Duration(s.cfg.Options().NATRenewalM)*time.Minute, time.Duration(s.cfg.Options().NATTimeoutS)*time.Second)
for _, mapping := range toRenew {
s.updateMapping(mapping, nats, true)
}
for _, mapping := range toUpdate {
s.updateMapping(mapping, nats, false)
}
return len(nats)
}
func (s *Service) Stop() {
s.mut.RLock()
close(s.stop)
s.mut.RUnlock()
}
func (s *Service) NewMapping(protocol Protocol, ip net.IP, port int) *Mapping {
mapping := &Mapping{
protocol: protocol,
address: Address{
IP: ip,
Port: port,
},
extAddresses: make(map[string]Address),
mut: sync.NewRWMutex(),
}
s.mut.Lock()
s.mappings = append(s.mappings, mapping)
// Reset the timer while holding the lock, see process() for explanation
s.timer.Reset(time.Second)
s.mut.Unlock()
return mapping
}
// RemoveMapping does not actually remove the mapping from the IGD, it just
// internally removes it which stops renewing the mapping. Also, it clears any
// existing mapped addresses from the mapping, which as a result should cause
// discovery to reannounce the new addresses.
func (s *Service) RemoveMapping(mapping *Mapping) {
s.mut.Lock()
defer s.mut.Unlock()
for i, existing := range s.mappings {
if existing == mapping {
mapping.clearAddresses()
last := len(s.mappings) - 1
s.mappings[i] = s.mappings[last]
s.mappings[last] = nil
s.mappings = s.mappings[:last]
return
}
}
}
// updateMapping compares the addresses of the existing mapping versus the natds
// discovered, and removes any addresses of natds that do not exist, or tries to
// acquire mappings for natds which the mapping was unaware of before.
// Optionally takes renew flag which indicates whether or not we should renew
// mappings with existing natds
func (s *Service) updateMapping(mapping *Mapping, nats map[string]Device, renew bool) {
var added, removed []Address
renewalTime := time.Duration(s.cfg.Options().NATRenewalM) * time.Minute
mapping.expires = time.Now().Add(renewalTime)
newAdded, newRemoved := s.verifyExistingMappings(mapping, nats, renew)
added = append(added, newAdded...)
removed = append(removed, newRemoved...)
newAdded, newRemoved = s.acquireNewMappings(mapping, nats)
added = append(added, newAdded...)
removed = append(removed, newRemoved...)
if len(added) > 0 || len(removed) > 0 {
mapping.notify(added, removed)
}
}
func (s *Service) verifyExistingMappings(mapping *Mapping, nats map[string]Device, renew bool) ([]Address, []Address) {
var added, removed []Address
leaseTime := time.Duration(s.cfg.Options().NATLeaseM) * time.Minute
for id, address := range mapping.addressMap() {
// Delete addresses for NATDevice's that do not exist anymore
nat, ok := nats[id]
if !ok {
mapping.removeAddress(id)
removed = append(removed, address)
continue
} else if renew {
// Only perform renewals on the nat's that have the right local IP
// address
localIP := nat.GetLocalIPAddress()
if !mapping.validGateway(localIP) {
l.Debugf("Skipping %s for %s because of IP mismatch. %s != %s", id, mapping, mapping.address.IP, localIP)
continue
}
l.Debugf("Renewing %s -> %s mapping on %s", mapping, address, id)
addr, err := s.tryNATDevice(nat, mapping.address.Port, address.Port, leaseTime)
if err != nil {
l.Debugf("Failed to renew %s -> mapping on %s", mapping, address, id)
mapping.removeAddress(id)
removed = append(removed, address)
continue
}
l.Debugf("Renewed %s -> %s mapping on %s", mapping, address, id)
if !addr.Equal(address) {
mapping.removeAddress(id)
mapping.setAddress(id, addr)
removed = append(removed, address)
added = append(added, address)
}
}
}
return added, removed
}
func (s *Service) acquireNewMappings(mapping *Mapping, nats map[string]Device) ([]Address, []Address) {
var added, removed []Address
leaseTime := time.Duration(s.cfg.Options().NATLeaseM) * time.Minute
addrMap := mapping.addressMap()
for id, nat := range nats {
if _, ok := addrMap[id]; ok {
continue
}
// Only perform mappings on the nat's that have the right local IP
// address
localIP := nat.GetLocalIPAddress()
if !mapping.validGateway(localIP) {
l.Debugf("Skipping %s for %s because of IP mismatch. %s != %s", id, mapping, mapping.address.IP, localIP)
continue
}
l.Debugf("Acquiring %s mapping on %s", mapping, id)
addr, err := s.tryNATDevice(nat, mapping.address.Port, 0, leaseTime)
if err != nil {
l.Debugf("Failed to acquire %s mapping on %s", mapping, id)
continue
}
l.Debugf("Acquired %s -> %s mapping on %s", mapping, addr, id)
mapping.setAddress(id, addr)
added = append(added, addr)
}
return added, removed
}
// tryNATDevice tries to acquire a port mapping for the given internal address to
// the given external port. If external port is 0, picks a pseudo-random port.
func (s *Service) tryNATDevice(natd Device, intPort, extPort int, leaseTime time.Duration) (Address, error) {
var err error
var port int
// Generate a predictable random which is based on device ID + local port + hash of the device ID
// number so that the ports we'd try to acquire for the mapping would always be the same for the
// same device trying to get the same internal port.
predictableRand := rand.New(rand.NewSource(int64(s.id.Short()) + int64(intPort) + hash(natd.ID())))
if extPort != 0 {
// First try renewing our existing mapping, if we have one.
name := fmt.Sprintf("syncthing-%d", extPort)
port, err = natd.AddPortMapping(TCP, intPort, extPort, name, leaseTime)
if err == nil {
extPort = port
goto findIP
}
l.Debugln("Error extending lease on", natd.ID(), err)
}
for i := 0; i < 10; i++ {
// Then try up to ten random ports.
extPort = 1024 + predictableRand.Intn(65535-1024)
name := fmt.Sprintf("syncthing-%d", extPort)
port, err = natd.AddPortMapping(TCP, intPort, extPort, name, leaseTime)
if err == nil {
extPort = port
goto findIP
}
l.Debugln("Error getting new lease on", natd.ID(), err)
}
return Address{}, err
findIP:
ip, err := natd.GetExternalIPAddress()
if err != nil {
l.Debugln("Error getting external ip on", natd.ID(), err)
ip = nil
}
return Address{
IP: ip,
Port: extPort,
}, nil
}
func hash(input string) int64 {
h := fnv.New64a()
h.Write([]byte(input))
return int64(h.Sum64())
}