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 2019 Tailscale & 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 magicsock
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import (
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"fmt"
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"net"
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)
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// DerpMagicIP is a fake WireGuard endpoint IP address that means
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// to use DERP. When used, the port number of the WireGuard endpoint
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// is the DERP server number to use.
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//
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// Mnemonic: 3.3.40 are numbers above the keys D, E, R, P.
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const DerpMagicIP = "127.3.3.40"
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var derpMagicIP = net.ParseIP(DerpMagicIP).To4()
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var (
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derpHostOfIndex = map[int]string{} // node ID index (fake port number) -> hostname
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derpIndexOfHost = map[string]int{} // derpHostOfIndex reversed
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derpNodeID []int
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)
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const (
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derpNYC = 1
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derpSF = 2
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)
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func init() {
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addDerper(derpNYC, "derp.tailscale.com")
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addDerper(derpSF, "derp2.tailscale.com")
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}
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func addDerper(i int, host string) {
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if other, dup := derpHostOfIndex[i]; dup {
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panic(fmt.Sprintf("duplicate DERP index %v (host %q and %q)", i, other, host))
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}
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if other, dup := derpIndexOfHost[host]; dup {
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panic(fmt.Sprintf("duplicate DERP host %q (index %v and %v)", host, other, i))
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}
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derpHostOfIndex[i] = host
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derpIndexOfHost[host] = i
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derpNodeID = append(derpNodeID, i)
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}
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// derpHost returns the hostname of a DERP server index (a fake port
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// number used with derpMagicIP). It always returns a non-empty string.
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func derpHost(i int) string {
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if h, ok := derpHostOfIndex[i]; ok {
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return h
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}
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if 1 <= i && i <= 64<<10 {
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return fmt.Sprintf("derp%v.tailscale.com", i)
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}
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return "derp.tailscale.com"
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}
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