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