nat: introduce new NAT traversal package with UPnP/NAT-PMP implementations
In this commit, we introduce a new package `nat`. This package is responsible for handling the different techniques for NAT traversals. Specifically, we have implemented UPnP and NAT-PMP support. This will allow users to easily advertise their nodes to the network as long as their devices are behind a single NAT. Devices behind multiple NATs are not supported.
This commit is contained in:
Wilmer Paulino
parent
8651b4a422
commit
377e770db4
117
nat/pmp.go
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117
nat/pmp.go
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package nat
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import (
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"fmt"
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"net"
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"sync"
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"time"
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"github.com/jackpal/gateway"
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natpmp "github.com/jackpal/go-nat-pmp"
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)
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// Compile-time check to ensure PMP implements the Traversal interface.
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var _ Traversal = (*PMP)(nil)
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// PMP is a concrete implementation of the Traversal interface that uses the
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// NAT-PMP technique.
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type PMP struct {
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client *natpmp.Client
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forwardedPortsMtx sync.Mutex
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forwardedPorts map[uint16]struct{}
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}
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// DiscoverPMP attempts to scan the local network for a NAT-PMP enabled device
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// within the given timeout.
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func DiscoverPMP(timeout time.Duration) (*PMP, error) {
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// Retrieve the gateway IP address of the local network.
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gatewayIP, err := gateway.DiscoverGateway()
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if err != nil {
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return nil, err
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}
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pmp := &PMP{
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client: natpmp.NewClientWithTimeout(gatewayIP, timeout),
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forwardedPorts: make(map[uint16]struct{}),
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}
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// We'll then attempt to retrieve the external IP address of this
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// device to ensure it is not behind multiple NATs.
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if _, err := pmp.ExternalIP(); err != nil {
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return nil, err
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}
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return pmp, nil
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}
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// ExternalIP returns the external IP address of the NAT-PMP enabled device.
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func (p *PMP) ExternalIP() (net.IP, error) {
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res, err := p.client.GetExternalAddress()
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if err != nil {
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return nil, err
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}
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ip := net.IP(res.ExternalIPAddress[:])
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if isPrivateIP(ip) {
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return nil, ErrMultipleNAT
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}
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return ip, nil
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}
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// AddPortMapping enables port forwarding for the given port.
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func (p *PMP) AddPortMapping(port uint16) error {
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p.forwardedPortsMtx.Lock()
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defer p.forwardedPortsMtx.Unlock()
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if _, exists := p.forwardedPorts[port]; exists {
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return nil
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}
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_, err := p.client.AddPortMapping("tcp", int(port), int(port), 0)
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if err != nil {
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return err
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}
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p.forwardedPorts[port] = struct{}{}
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return nil
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}
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// DeletePortMapping disables port forwarding for the given port.
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func (p *PMP) DeletePortMapping(port uint16) error {
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p.forwardedPortsMtx.Lock()
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defer p.forwardedPortsMtx.Unlock()
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if _, exists := p.forwardedPorts[port]; !exists {
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return fmt.Errorf("port %d is not being forwarded", port)
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}
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_, err := p.client.AddPortMapping("tcp", int(port), 0, 0)
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if err != nil {
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return err
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}
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delete(p.forwardedPorts, port)
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return nil
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}
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// ForwardedPorts returns a list of ports currently being forwarded.
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func (p *PMP) ForwardedPorts() []uint16 {
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p.forwardedPortsMtx.Lock()
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defer p.forwardedPortsMtx.Unlock()
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ports := make([]uint16, 0, len(p.forwardedPorts))
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for port := range p.forwardedPorts {
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ports = append(ports, port)
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}
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return ports
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}
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// Name returns the name of the specific NAT traversal technique used.
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func (p *PMP) Name() string {
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return "NAT-PMP"
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}
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58
nat/traversal.go
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58
nat/traversal.go
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package nat
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import (
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"errors"
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"net"
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)
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var (
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// private24BitBlock contains the set of private IPv4 addresses within
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// the 10.0.0.0/8 adddress space.
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private24BitBlock *net.IPNet
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// private20BitBlock contains the set of private IPv4 addresses within
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// the 172.16.0.0/12 address space.
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private20BitBlock *net.IPNet
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// private16BitBlock contains the set of private IPv4 addresses within
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// the 192.168.0.0/16 address space.
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private16BitBlock *net.IPNet
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// ErrMultipleNAT is an error returned when multiple NATs have been
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// detected.
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ErrMultipleNAT = errors.New("multiple NATs detected")
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)
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func init() {
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_, private24BitBlock, _ = net.ParseCIDR("10.0.0.0/8")
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_, private20BitBlock, _ = net.ParseCIDR("172.16.0.0/12")
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_, private16BitBlock, _ = net.ParseCIDR("192.168.0.0/16")
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}
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// Traversal is an interface that brings together the different NAT traversal
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// techniques.
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type Traversal interface {
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// ExternalIP returns the external IP address.
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ExternalIP() (net.IP, error)
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// AddPortMapping adds a port mapping for the given port between the
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// private and public addresses.
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AddPortMapping(port uint16) error
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// DeletePortMapping deletes a port mapping for the given port between
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// the private and public addresses.
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DeletePortMapping(port uint16) error
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// ForwardedPorts returns the ports currently being forwarded using NAT
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// traversal.
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ForwardedPorts() []uint16
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// Name returns the name of the specific NAT traversal technique used.
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Name() string
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}
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// isPrivateIP determines if the IP is private.
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func isPrivateIP(ip net.IP) bool {
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return private24BitBlock.Contains(ip) ||
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private20BitBlock.Contains(ip) || private16BitBlock.Contains(ip)
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}
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112
nat/upnp.go
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112
nat/upnp.go
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@ -0,0 +1,112 @@
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package nat
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import (
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"context"
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"fmt"
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"net"
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"sync"
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upnp "github.com/NebulousLabs/go-upnp"
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)
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// Compile-time check to ensure UPnP implements the Traversal interface.
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var _ Traversal = (*UPnP)(nil)
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// UPnP is a concrete implementation of the Traversal interface that uses the
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// UPnP technique.
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type UPnP struct {
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device *upnp.IGD
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forwardedPortsMtx sync.Mutex
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forwardedPorts map[uint16]struct{}
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}
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// DiscoverUPnP scans the local network for a UPnP enabled device.
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func DiscoverUPnP(ctx context.Context) (*UPnP, error) {
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// Scan the local network for a UPnP-enabled device.
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device, err := upnp.DiscoverCtx(ctx)
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if err != nil {
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return nil, err
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}
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u := &UPnP{
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device: device,
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forwardedPorts: make(map[uint16]struct{}),
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}
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// We'll then attempt to retrieve the external IP address of this
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// device to ensure it is not behind multiple NATs.
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if _, err := u.ExternalIP(); err != nil {
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return nil, err
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}
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return u, nil
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}
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// ExternalIP returns the external IP address of the UPnP enabled device.
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func (u *UPnP) ExternalIP() (net.IP, error) {
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ip, err := u.device.ExternalIP()
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if err != nil {
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return nil, err
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}
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if isPrivateIP(net.ParseIP(ip)) {
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return nil, ErrMultipleNAT
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}
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return net.ParseIP(ip), nil
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}
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// AddPortMapping enables port forwarding for the given port.
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func (u *UPnP) AddPortMapping(port uint16) error {
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u.forwardedPortsMtx.Lock()
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defer u.forwardedPortsMtx.Unlock()
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if _, exists := u.forwardedPorts[port]; exists {
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return nil
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}
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if err := u.device.Forward(port, ""); err != nil {
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return err
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}
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u.forwardedPorts[port] = struct{}{}
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return nil
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}
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// DeletePortMapping disables port forwarding for the given port.
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func (u *UPnP) DeletePortMapping(port uint16) error {
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u.forwardedPortsMtx.Lock()
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defer u.forwardedPortsMtx.Unlock()
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if _, exists := u.forwardedPorts[port]; !exists {
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return fmt.Errorf("port %d is not being forwarded", port)
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}
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if err := u.device.Clear(port); err != nil {
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return err
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}
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delete(u.forwardedPorts, port)
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return nil
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}
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// ForwardedPorts returns a list of ports currently being forwarded.
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func (u *UPnP) ForwardedPorts() []uint16 {
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u.forwardedPortsMtx.Lock()
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defer u.forwardedPortsMtx.Unlock()
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ports := make([]uint16, 0, len(u.forwardedPorts))
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for port := range u.forwardedPorts {
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ports = append(ports, port)
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}
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return ports
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}
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// Name returns the name of the specific NAT traversal technique used.
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func (u *UPnP) Name() string {
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return "UPnP"
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}
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