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net/interfaces: add func LikelyHomeRouterIP

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For discovering where we might direct NAT-PMP/PCP/UPnP queries at in
the future.
This commit is contained in:
Brad Fitzpatrick
2020-07-06 10:34:52 -07:00
parent c3c607e78a
commit 32156330a8
8 changed files with 222 additions and 1 deletions
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12
net/interfaces/interfaces.go
View File

@@ -230,6 +230,18 @@ func HTTPOfListener(ln net.Listener) string {
}
var likelyHomeRouterIP func() (netaddr.IP, bool)
// LikelyHomeRouterIP returns the likely IP of the residential router,
// which will always be an IPv4 private address, if found.
// This is used as the destination for UPnP, NAT-PMP, PCP, etc queries.
func LikelyHomeRouterIP() (ip netaddr.IP, ok bool) {
if likelyHomeRouterIP != nil {
return likelyHomeRouterIP()
}
return ip, false
}
func isPrivateIP(ip netaddr.IP) bool {
return private1.Contains(ip) || private2.Contains(ip) || private3.Contains(ip)
}

66
net/interfaces/interfaces_darwin.go Normal file
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@@ -0,0 +1,66 @@
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package interfaces
import (
"os/exec"
"go4.org/mem"
"inet.af/netaddr"
"tailscale.com/util/lineread"
)
func init() {
likelyHomeRouterIP = likelyHomeRouterIPDarwin
}
/*
Parse out 10.0.0.1 from:
$ netstat -r -n -f inet
Routing tables
Internet:
Destination Gateway Flags Netif Expire
default 10.0.0.1 UGSc en0
default link#14 UCSI utun2
10/16 link#4 UCS en0 !
10.0.0.1/32 link#4 UCS en0 !
...
*/
func likelyHomeRouterIPDarwin() (ret netaddr.IP, ok bool) {
cmd := exec.Command("/usr/sbin/netstat", "-r", "-n", "-f", "inet")
stdout, err := cmd.StdoutPipe()
if err != nil {
return
}
if err := cmd.Start(); err != nil {
return
}
defer cmd.Wait()
var f []mem.RO
lineread.Reader(stdout, func(lineb []byte) error {
line := mem.B(lineb)
if !mem.Contains(line, mem.S("default")) {
return nil
}
f = mem.AppendFields(f[:0], line)
if len(f) < 3 || !f[0].EqualString("default") {
return nil
}
ipm, flagsm := f[1], f[2]
if !mem.Contains(flagsm, mem.S("G")) {
return nil
}
ip, err := netaddr.ParseIP(string(mem.Append(nil, ipm)))
if err == nil && isPrivateIP(ip) {
ret = ip
}
return nil
})
return ret, !ret.IsZero()
}

59
net/interfaces/interfaces_linux.go Normal file
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@@ -0,0 +1,59 @@
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package interfaces
import (
"go4.org/mem"
"inet.af/netaddr"
"tailscale.com/util/lineread"
)
func init() {
likelyHomeRouterIP = likelyHomeRouterIPLinux
}
/*
Parse 10.0.0.1 out of:
$ cat /proc/net/route
Iface Destination Gateway Flags RefCnt Use Metric Mask MTU Window IRTT
ens18 00000000 0100000A 0003 0 0 0 00000000 0 0 0
ens18 0000000A 00000000 0001 0 0 0 0000FFFF 0 0 0
*/
func likelyHomeRouterIPLinux() (ret netaddr.IP, ok bool) {
lineNum := 0
var f []mem.RO
lineread.File("/proc/net/route", func(line []byte) error {
lineNum++
if lineNum == 1 {
// Skip header line.
return nil
}
f = mem.AppendFields(f[:0], mem.B(line))
if len(f) < 4 {
return nil
}
gwHex, flagsHex := f[2], f[3]
flags, err := mem.ParseUint(flagsHex, 16, 16)
if err != nil {
return nil // ignore error, skip line and keep going
}
const RTF_UP = 0x0001
const RTF_GATEWAY = 0x0002
if flags&(RTF_UP|RTF_GATEWAY) != RTF_UP|RTF_GATEWAY {
return nil
}
ipu32, err := mem.ParseUint(gwHex, 16, 32)
if err != nil {
return nil // ignore error, skip line and keep going
}
ip := netaddr.IPv4(byte(ipu32), byte(ipu32>>8), byte(ipu32>>16), byte(ipu32>>24))
if isPrivateIP(ip) {
ret = ip
}
return nil
})
return ret, !ret.IsZero()
}

5
net/interfaces/interfaces_test.go
View File

@@ -47,3 +47,8 @@ func TestGetState(t *testing.T) {
t.Fatal("two States back-to-back were not equal")
}
}
func TestLikelyHomeRouterIP(t *testing.T) {
ip, ok := LikelyHomeRouterIP()
t.Logf("got %v, %v", ip, ok)
}

71
net/interfaces/interfaces_windows.go Normal file
View File

@@ -0,0 +1,71 @@
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package interfaces
import (
"os/exec"
"go4.org/mem"
"inet.af/netaddr"
"tailscale.com/util/lineread"
)
func init() {
likelyHomeRouterIP = likelyHomeRouterIPWindows
}
/*
Parse out 10.0.0.1 from:
Z:\>route print -4
===========================================================================
Interface List
15...aa 15 48 ff 1c 72 ......Red Hat VirtIO Ethernet Adapter
5...........................Tailscale Tunnel
1...........................Software Loopback Interface 1
===========================================================================
IPv4 Route Table
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 10.0.0.1 10.0.28.63 5
10.0.0.0 255.255.0.0 On-link 10.0.28.63 261
10.0.28.63 255.255.255.255 On-link 10.0.28.63 261
10.0.42.0 255.255.255.0 100.103.42.106 100.103.42.106 5
10.0.255.255 255.255.255.255 On-link 10.0.28.63 261
34.193.248.174 255.255.255.255 100.103.42.106 100.103.42.106 5
*/
func likelyHomeRouterIPWindows() (ret netaddr.IP, ok bool) {
cmd := exec.Command("route", "print", "-4")
stdout, err := cmd.StdoutPipe()
if err != nil {
return
}
if err := cmd.Start(); err != nil {
return
}
defer cmd.Wait()
var f []mem.RO
lineread.Reader(stdout, func(lineb []byte) error {
line := mem.B(lineb)
if !mem.Contains(line, mem.S("0.0.0.0")) {
return nil
}
f = mem.AppendFields(f[:0], line)
if len(f) < 3 || !f[0].EqualString("0.0.0.0") || !f[1].EqualString("0.0.0.0") {
return nil
}
ipm := f[2]
ip, err := netaddr.ParseIP(string(mem.Append(nil, ipm)))
if err == nil && isPrivateIP(ip) {
ret = ip
}
return nil
})
return ret, !ret.IsZero()
}