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tailscale/wgengine/tsdns/map.go

161 lines
3.8 KiB
Go

// 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 tsdns
import (
"sort"
"strings"
"inet.af/netaddr"
)
// Map is all the data Resolver needs to resolve DNS queries within the Tailscale network.
type Map struct {
// nameToIP is a mapping of Tailscale domain names to their IP addresses.
// For example, monitoring.tailscale.us -> 100.64.0.1.
nameToIP map[string]netaddr.IP
// ipToName is the inverse of nameToIP.
ipToName map[netaddr.IP]string
// names are the keys of nameToIP in sorted order.
names []string
// rootDomains are the domains whose subdomains should always
// be resolved locally to prevent leakage of sensitive names.
rootDomains []string // e.g. "user.provider.beta.tailscale.net."
}
// NewMap returns a new Map with name to address mapping given by nameToIP.
//
// rootDomains are the domains whose subdomains should always be
// resolved locally to prevent leakage of sensitive names. They should
// end in a period ("user-foo.tailscale.net.").
func NewMap(initNameToIP map[string]netaddr.IP, rootDomains []string) *Map {
// TODO(dmytro): we have to allocate names and ipToName, but nameToIP can be avoided.
// It is here because control sends us names not in canonical form. Change this.
names := make([]string, 0, len(initNameToIP))
nameToIP := make(map[string]netaddr.IP, len(initNameToIP))
ipToName := make(map[netaddr.IP]string, len(initNameToIP))
for name, ip := range initNameToIP {
if len(name) == 0 {
// Nothing useful can be done with empty names.
continue
}
if name[len(name)-1] != '.' {
name += "."
}
names = append(names, name)
nameToIP[name] = ip
ipToName[ip] = name
}
sort.Strings(names)
return &Map{
nameToIP: nameToIP,
ipToName: ipToName,
names: names,
rootDomains: rootDomains,
}
}
func printSingleNameIP(buf *strings.Builder, name string, ip netaddr.IP) {
buf.WriteString(name)
buf.WriteByte('\t')
buf.WriteString(ip.String())
buf.WriteByte('\n')
}
func (m *Map) Pretty() string {
buf := new(strings.Builder)
for _, name := range m.names {
printSingleNameIP(buf, name, m.nameToIP[name])
}
return buf.String()
}
func (m *Map) PrettyDiffFrom(old *Map) string {
var (
oldNameToIP map[string]netaddr.IP
newNameToIP map[string]netaddr.IP
oldNames []string
newNames []string
)
if old != nil {
oldNameToIP = old.nameToIP
oldNames = old.names
}
if m != nil {
newNameToIP = m.nameToIP
newNames = m.names
}
buf := new(strings.Builder)
space := func() bool {
return buf.Len() < (1 << 10)
}
for len(oldNames) > 0 && len(newNames) > 0 {
var name string
newName, oldName := newNames[0], oldNames[0]
switch {
case oldName < newName:
name = oldName
oldNames = oldNames[1:]
case oldName > newName:
name = newName
newNames = newNames[1:]
case oldNames[0] == newNames[0]:
name = oldNames[0]
oldNames = oldNames[1:]
newNames = newNames[1:]
}
if !space() {
continue
}
ipOld, inOld := oldNameToIP[name]
ipNew, inNew := newNameToIP[name]
switch {
case !inOld:
buf.WriteByte('+')
printSingleNameIP(buf, name, ipNew)
case !inNew:
buf.WriteByte('-')
printSingleNameIP(buf, name, ipOld)
case ipOld != ipNew:
buf.WriteByte('-')
printSingleNameIP(buf, name, ipOld)
buf.WriteByte('+')
printSingleNameIP(buf, name, ipNew)
}
}
for _, name := range oldNames {
if !space() {
break
}
if _, ok := newNameToIP[name]; !ok {
buf.WriteByte('-')
printSingleNameIP(buf, name, oldNameToIP[name])
}
}
for _, name := range newNames {
if !space() {
break
}
if _, ok := oldNameToIP[name]; !ok {
buf.WriteByte('+')
printSingleNameIP(buf, name, newNameToIP[name])
}
}
if !space() {
buf.WriteString("... [truncated]\n")
}
return buf.String()
}