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tailscale/wgengine/magicsock/derpmap.go

58 lines
1.5 KiB
Go

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