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This works around the 2.3s delay in short name lookups when SNR is enabled. C:\Windows\System32\drivers\etc\hosts file. We only add known hosts that match the search domains, and we populate the list in order of Search Domains so that our matching algorithm mimics what Windows would otherwise do itself if SNR was off. Updates #1659 Signed-off-by: Maisem Ali <maisem@tailscale.com>
104 lines
3.3 KiB
Go
104 lines
3.3 KiB
Go
// Copyright (c) 2021 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 dns
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import (
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"errors"
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"net/netip"
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"tailscale.com/util/dnsname"
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)
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// An OSConfigurator applies DNS settings to the operating system.
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type OSConfigurator interface {
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// SetDNS updates the OS's DNS configuration to match cfg.
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// If cfg is the zero value, all Tailscale-related DNS
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// configuration is removed.
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// SetDNS must not be called after Close.
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// SetDNS takes ownership of cfg.
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SetDNS(cfg OSConfig) error
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// SupportsSplitDNS reports whether the configurator is capable of
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// installing a resolver only for specific DNS suffixes. If false,
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// the configurator can only set a global resolver.
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SupportsSplitDNS() bool
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// GetBaseConfig returns the OS's "base" configuration, i.e. the
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// resolver settings the OS would use without Tailscale
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// contributing any configuration.
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// GetBaseConfig must return the tailscale-free base config even
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// after SetDNS has been called to set a Tailscale configuration.
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// Only works when SupportsSplitDNS=false.
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// Implementations that don't support getting the base config must
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// return ErrGetBaseConfigNotSupported.
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GetBaseConfig() (OSConfig, error)
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// Close removes Tailscale-related DNS configuration from the OS.
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Close() error
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}
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// HostEntry represents a single line in the OS's hosts file.
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type HostEntry struct {
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Addr netip.Addr
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Hosts []string
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}
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// OSConfig is an OS DNS configuration.
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type OSConfig struct {
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// Hosts is a map of DNS FQDNs to their IPs, which should be added to the
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// OS's hosts file. Currently, (2022-08-12) it is only populated for Windows
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// in SplitDNS mode and with Smart Name Resolution turned on.
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Hosts []*HostEntry
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// Nameservers are the IP addresses of the nameservers to use.
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Nameservers []netip.Addr
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// SearchDomains are the domain suffixes to use when expanding
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// single-label name queries. SearchDomains is additive to
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// whatever non-Tailscale search domains the OS has.
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SearchDomains []dnsname.FQDN
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// MatchDomains are the DNS suffixes for which Nameservers should
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// be used. If empty, Nameservers is installed as the "primary" resolver.
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// A non-empty MatchDomains requests a "split DNS" configuration
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// from the OS, which will only work with OSConfigurators that
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// report SupportsSplitDNS()=true.
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MatchDomains []dnsname.FQDN
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}
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func (o OSConfig) IsZero() bool {
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return len(o.Nameservers) == 0 && len(o.SearchDomains) == 0 && len(o.MatchDomains) == 0
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}
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func (a OSConfig) Equal(b OSConfig) bool {
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if len(a.Nameservers) != len(b.Nameservers) {
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return false
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}
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if len(a.SearchDomains) != len(b.SearchDomains) {
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return false
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}
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if len(a.MatchDomains) != len(b.MatchDomains) {
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return false
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}
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for i := range a.Nameservers {
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if a.Nameservers[i] != b.Nameservers[i] {
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return false
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}
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}
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for i := range a.SearchDomains {
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if a.SearchDomains[i] != b.SearchDomains[i] {
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return false
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}
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}
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for i := range a.MatchDomains {
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if a.MatchDomains[i] != b.MatchDomains[i] {
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return false
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}
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}
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return true
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}
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// ErrGetBaseConfigNotSupported is the error
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// OSConfigurator.GetBaseConfig returns when the OSConfigurator
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// doesn't support reading the underlying configuration out of the OS.
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var ErrGetBaseConfigNotSupported = errors.New("getting OS base config is not supported")
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