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tailscale/net/dns/manager_darwin.go

127 lines
3.2 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package dns
import (
"bytes"
"os"
"go4.org/mem"
"tailscale.com/control/controlknobs"
"tailscale.com/health"
"tailscale.com/types/logger"
"tailscale.com/util/mak"
)
// NewOSConfigurator creates a new OS configurator.
//
// The health tracker and the knobs may be nil and are ignored on this platform.
func NewOSConfigurator(logf logger.Logf, _ *health.Tracker, _ *controlknobs.Knobs, ifName string) (OSConfigurator, error) {
return &darwinConfigurator{logf: logf, ifName: ifName}, nil
}
// darwinConfigurator is the tailscaled-on-macOS DNS OS configurator that
// maintains the Split DNS nameserver entries pointing MagicDNS DNS suffixes
// to 100.100.100.100 using the macOS /etc/resolver/$SUFFIX files.
type darwinConfigurator struct {
logf logger.Logf
ifName string
}
func (c *darwinConfigurator) Close() error {
c.removeResolverFiles(func(domain string) bool { return true })
return nil
}
func (c *darwinConfigurator) SupportsSplitDNS() bool {
return true
}
func (c *darwinConfigurator) SetDNS(cfg OSConfig) error {
var buf bytes.Buffer
buf.WriteString(macResolverFileHeader)
for _, ip := range cfg.Nameservers {
buf.WriteString("nameserver ")
buf.WriteString(ip.String())
buf.WriteString("\n")
}
if err := os.MkdirAll("/etc/resolver", 0755); err != nil {
return err
}
var keep map[string]bool
// Add a dummy file to /etc/resolver with a "search ..." directive if we have
// search suffixes to add.
if len(cfg.SearchDomains) > 0 {
const searchFile = "search.tailscale" // fake DNS suffix+TLD to put our search
mak.Set(&keep, searchFile, true)
var sbuf bytes.Buffer
sbuf.WriteString(macResolverFileHeader)
sbuf.WriteString("search")
for _, d := range cfg.SearchDomains {
sbuf.WriteString(" ")
sbuf.WriteString(string(d.WithoutTrailingDot()))
}
sbuf.WriteString("\n")
if err := os.WriteFile("/etc/resolver/"+searchFile, sbuf.Bytes(), 0644); err != nil {
return err
}
}
for _, d := range cfg.MatchDomains {
fileBase := string(d.WithoutTrailingDot())
mak.Set(&keep, fileBase, true)
fullPath := "/etc/resolver/" + fileBase
if err := os.WriteFile(fullPath, buf.Bytes(), 0644); err != nil {
return err
}
}
return c.removeResolverFiles(func(domain string) bool { return !keep[domain] })
}
func (c *darwinConfigurator) GetBaseConfig() (OSConfig, error) {
return OSConfig{}, ErrGetBaseConfigNotSupported
}
const macResolverFileHeader = "# Added by tailscaled\n"
// removeResolverFiles deletes all files in /etc/resolver for which the shouldDelete
// func returns true.
func (c *darwinConfigurator) removeResolverFiles(shouldDelete func(domain string) bool) error {
dents, err := os.ReadDir("/etc/resolver")
if os.IsNotExist(err) {
return nil
}
if err != nil {
return err
}
for _, de := range dents {
if !de.Type().IsRegular() {
continue
}
name := de.Name()
if !shouldDelete(name) {
continue
}
fullPath := "/etc/resolver/" + name
contents, err := os.ReadFile(fullPath)
if err != nil {
if os.IsNotExist(err) { // race?
continue
}
return err
}
if !mem.HasPrefix(mem.B(contents), mem.S(macResolverFileHeader)) {
continue
}
if err := os.Remove(fullPath); err != nil {
return err
}
}
return nil
}