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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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
cmd/tailscale/netcheck.go
View File

@ -18,6 +18,7 @@
"github.com/peterbourgon/ff/v2/ffcli"
"tailscale.com/derp/derpmap"
"tailscale.com/net/dnscache"
"tailscale.com/net/interfaces"
"tailscale.com/net/netcheck"
"tailscale.com/tailcfg"
"tailscale.com/types/logger"
@ -50,6 +51,11 @@ func runNetcheck(ctx context.Context, args []string) error {
if netcheckArgs.verbose {
c.Logf = logger.WithPrefix(log.Printf, "netcheck: ")
c.Verbose = true
if gw, ok := interfaces.LikelyHomeRouterIP(); ok {
c.Logf("likely home router: %v", gw)
} else {
c.Logf("no likely home router IP found")
}
} else {
c.Logf = logger.Discard
}

2
go.mod
View File

@ -21,7 +21,7 @@ require (
github.com/tailscale/wireguard-go v0.0.0-20200624060658-de1f1af1f35f
github.com/tcnksm/go-httpstat v0.2.0
github.com/toqueteos/webbrowser v1.2.0
go4.org/mem v0.0.0-20200601023850-d8ee1dfa5518
go4.org/mem v0.0.0-20200706164138-185c595c3ecc
golang.org/x/crypto v0.0.0-20200317142112-1b76d66859c6
golang.org/x/net v0.0.0-20200301022130-244492dfa37a
golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d

2
go.sum
View File

@ -96,6 +96,8 @@ github.com/xi2/xz v0.0.0-20171230120015-48954b6210f8 h1:nIPpBwaJSVYIxUFsDv3M8ofm
github.com/xi2/xz v0.0.0-20171230120015-48954b6210f8/go.mod h1:HUYIGzjTL3rfEspMxjDjgmT5uz5wzYJKVo23qUhYTos=
go4.org/mem v0.0.0-20200601023850-d8ee1dfa5518 h1:AA3bSGklCgkrqIGnvL4894oa/2K9ltE0RejXh8CgyvA=
go4.org/mem v0.0.0-20200601023850-d8ee1dfa5518/go.mod h1:NEYvpHWemiG/E5UWfaN5QAIGZeT1sa0Z2UNk6oeMb/k=
go4.org/mem v0.0.0-20200706164138-185c595c3ecc h1:paujszgN6SpsO/UsXC7xax3gQAKz/XQKCYZLQdU34Tw=
go4.org/mem v0.0.0-20200706164138-185c595c3ecc/go.mod h1:NEYvpHWemiG/E5UWfaN5QAIGZeT1sa0Z2UNk6oeMb/k=
golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
golang.org/x/crypto v0.0.0-20191002192127-34f69633bfdc/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=

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
View File

@ -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
View File

@ -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()
}