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Better handle networks with multiple NATS #9

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Better handle networks with multiple NATS #9

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943d7b3
expose all discovered NATs
Stebalien Mar 6, 2019
c8594db
try to pick the best NAT when multiple NATs are discovered
Stebalien Mar 6, 2019
6994e2e
don't mask context
Stebalien May 3, 2019
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93 changes: 83 additions & 10 deletions nat.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2,11 +2,14 @@
package nat

import (
"context"
"errors"
"math"
"math/rand"
"net"
"time"

"github.com/jackpal/gateway"
)

var ErrNoExternalAddress = errors.New("no external address")
Expand Down Expand Up @@ -34,20 +37,90 @@ type NAT interface {
DeletePortMapping(protocol string, internalPort int) (err error)
}

// DiscoverNATs returns all NATs discovered in the network.
func DiscoverNATs(ctx context.Context) <-chan NAT {
nats := make(chan NAT)

go func() {
defer close(nats)

ctx, cancel := context.WithCancel(context.Background())
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Just curious what is the difference from the first input ctx argument?

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That's a bug.

defer cancel()

upnpIg1 := discoverUPNP_IG1(ctx)
upnpIg2 := discoverUPNP_IG2(ctx)
natpmp := discoverNATPMP(ctx)
upnpGenIGDev := discoverUPNP_GenIGDev(ctx)
for upnpIg1 != nil || upnpIg2 != nil || natpmp != nil {
var (
nat NAT
ok bool
)
select {
case nat, ok = <-upnpIg1:
if !ok {
upnpIg1 = nil
}
case nat, ok = <-upnpIg2:
if !ok {
upnpIg2 = nil
}
case nat, ok = <-upnpGenIGDev:
if !ok {
upnpGenIGDev = nil
}
case nat, ok = <-natpmp:
if !ok {
natpmp = nil
}
}
if ok {
select {
case nats <- nat:
case <-ctx.Done():
return
}
}
}
}()
return nats
}

// DiscoverGateway attempts to find a gateway device.
func DiscoverGateway() (NAT, error) {
select {
case nat := <-discoverUPNP_IG1():
return nat, nil
case nat := <-discoverUPNP_IG2():
return nat, nil
case nat := <-discoverUPNP_GenIGDev():
return nat, nil
case nat := <-discoverNATPMP():
return nat, nil
case <-time.After(10 * time.Second):
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()

var nats []NAT
for nat := range DiscoverNATs(ctx) {
nats = append(nats, nat)
}
switch len(nats) {
case 0:
return nil, ErrNoNATFound
case 1:
return nats[0], nil
}
gw, _ := gateway.DiscoverGateway()
bestNAT := nats[0]
natGw, _ := bestNAT.GetDeviceAddress()
bestNATIsGw := gw != nil && natGw.Equal(gw)
// 1. Prefer gateways discovered _last_. This is an OK heuristic for
// discovering the most-upstream (furthest) NAT.
// 2. Prefer gateways that actually match our known gateway address.
// Some relays like to claim to be NATs even if they aren't.
for _, nat := range nats[1:] {
natGw, _ := nat.GetDeviceAddress()
natIsGw := gw != nil && natGw.Equal(gw)

if bestNATIsGw && !natIsGw {
continue
}

bestNATIsGw = natIsGw
bestNAT = nat
}
return bestNAT, nil
}

func randomPort() int {
Expand Down
40 changes: 29 additions & 11 deletions natpmp.go
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
package nat

import (
"context"
"net"
"time"

Expand All @@ -12,25 +13,42 @@ var (
_ NAT = (*natpmpNAT)(nil)
)

func discoverNATPMP() <-chan NAT {
func discoverNATPMP(ctx context.Context) <-chan NAT {
res := make(chan NAT, 1)

ip, err := gateway.DiscoverGateway()
if err == nil {
go discoverNATPMPWithAddr(res, ip)
go func() {
defer close(res)
// Unfortunately, we can't actually _stop_ the natpmp
// library. However, we can at least close _our_ channel
// and walk away.
select {
case client, ok := <-discoverNATPMPWithAddr(ip):
if ok {
res <- &natpmpNAT{client, ip, make(map[int]int)}
}
case <-ctx.Done():
}
}()
} else {
close(res)
}

return res
}

func discoverNATPMPWithAddr(c chan NAT, ip net.IP) {
client := natpmp.NewClient(ip)
_, err := client.GetExternalAddress()
if err != nil {
return
}

c <- &natpmpNAT{client, ip, make(map[int]int)}
func discoverNATPMPWithAddr(ip net.IP) <-chan *natpmp.Client {
res := make(chan *natpmp.Client, 1)
go func() {
defer close(res)
client := natpmp.NewClient(ip)
_, err := client.GetExternalAddress()
if err != nil {
return
}
res <- client
}()
return res
}

type natpmpNAT struct {
Expand Down
66 changes: 47 additions & 19 deletions upnp.go
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
package nat

import (
"context"
"net"
"net/url"
"strings"
Expand All @@ -17,9 +18,10 @@ var (
_ NAT = (*upnp_NAT)(nil)
)

func discoverUPNP_IG1() <-chan NAT {
res := make(chan NAT, 1)
func discoverUPNP_IG1(ctx context.Context) <-chan NAT {
res := make(chan NAT)
go func() {
defer close(res)

// find devices
devs, err := goupnp.DiscoverDevices(internetgateway1.URN_WANConnectionDevice_1)
Expand All @@ -33,6 +35,9 @@ func discoverUPNP_IG1() <-chan NAT {
}

dev.Root.Device.VisitServices(func(srv *goupnp.Service) {
if ctx.Err() != nil {
return
}
switch srv.ServiceType {
case internetgateway1.URN_WANIPConnection_1:
client := &internetgateway1.WANIPConnection1{ServiceClient: goupnp.ServiceClient{
Expand All @@ -42,8 +47,10 @@ func discoverUPNP_IG1() <-chan NAT {
}}
_, isNat, err := client.GetNATRSIPStatus()
if err == nil && isNat {
res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG1-IP1)", dev.Root}
return
select {
case res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG1-IP1)", dev.Root}:
case <-ctx.Done():
}
}

case internetgateway1.URN_WANPPPConnection_1:
Expand All @@ -54,8 +61,10 @@ func discoverUPNP_IG1() <-chan NAT {
}}
_, isNat, err := client.GetNATRSIPStatus()
if err == nil && isNat {
res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG1-PPP1)", dev.Root}
return
select {
case res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG1-PPP1)", dev.Root}:
case <-ctx.Done():
}
}

}
Expand All @@ -66,9 +75,10 @@ func discoverUPNP_IG1() <-chan NAT {
return res
}

func discoverUPNP_IG2() <-chan NAT {
res := make(chan NAT, 1)
func discoverUPNP_IG2(ctx context.Context) <-chan NAT {
res := make(chan NAT)
go func() {
defer close(res)

// find devices
devs, err := goupnp.DiscoverDevices(internetgateway2.URN_WANConnectionDevice_2)
Expand All @@ -82,6 +92,9 @@ func discoverUPNP_IG2() <-chan NAT {
}

dev.Root.Device.VisitServices(func(srv *goupnp.Service) {
if ctx.Err() != nil {
return
}
switch srv.ServiceType {
case internetgateway2.URN_WANIPConnection_1:
client := &internetgateway2.WANIPConnection1{ServiceClient: goupnp.ServiceClient{
Expand All @@ -91,8 +104,10 @@ func discoverUPNP_IG2() <-chan NAT {
}}
_, isNat, err := client.GetNATRSIPStatus()
if err == nil && isNat {
res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG2-IP1)", dev.Root}
return
select {
case res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG2-IP1)", dev.Root}:
case <-ctx.Done():
}
}

case internetgateway2.URN_WANIPConnection_2:
Expand All @@ -103,8 +118,10 @@ func discoverUPNP_IG2() <-chan NAT {
}}
_, isNat, err := client.GetNATRSIPStatus()
if err == nil && isNat {
res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG2-IP2)", dev.Root}
return
select {
case res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG2-IP2)", dev.Root}:
case <-ctx.Done():
}
}

case internetgateway2.URN_WANPPPConnection_1:
Expand All @@ -115,8 +132,10 @@ func discoverUPNP_IG2() <-chan NAT {
}}
_, isNat, err := client.GetNATRSIPStatus()
if err == nil && isNat {
res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG2-PPP1)", dev.Root}
return
select {
case res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG2-PPP1)", dev.Root}:
case <-ctx.Done():
}
}

}
Expand All @@ -127,9 +146,11 @@ func discoverUPNP_IG2() <-chan NAT {
return res
}

func discoverUPNP_GenIGDev() <-chan NAT {
func discoverUPNP_GenIGDev(ctx context.Context) <-chan NAT {
res := make(chan NAT, 1)
go func() {
defer close(res)

DeviceList, err := ssdp.Search(ssdp.All, 5, "")
if err != nil {
return
Expand All @@ -152,6 +173,9 @@ func discoverUPNP_GenIGDev() <-chan NAT {
}

RootDevice.Device.VisitServices(func(srv *goupnp.Service) {
if ctx.Err() != nil {
return
}
switch srv.ServiceType {
case internetgateway1.URN_WANIPConnection_1:
client := &internetgateway1.WANIPConnection1{ServiceClient: goupnp.ServiceClient{
Expand All @@ -161,8 +185,10 @@ func discoverUPNP_GenIGDev() <-chan NAT {
}}
_, isNat, err := client.GetNATRSIPStatus()
if err == nil && isNat {
res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG1-IP1)", RootDevice}
return
select {
case res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG1-IP1)", RootDevice}:
case <-ctx.Done():
}
}

case internetgateway1.URN_WANPPPConnection_1:
Expand All @@ -173,8 +199,10 @@ func discoverUPNP_GenIGDev() <-chan NAT {
}}
_, isNat, err := client.GetNATRSIPStatus()
if err == nil && isNat {
res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG1-PPP1)", RootDevice}
return
select {
case res <- &upnp_NAT{client, make(map[int]int), "UPNP (IG1-PPP1)", RootDevice}:
case <-ctx.Done():
}
}

}
Expand Down