dns

Documentation

Index

• Variables
• func Cleanup(logf logger.Logf, interfaceName string)
• func NewNoopManager() (noopManager, error)
• type Config
  • func (c *Config) WriteToBufioWriter(w *bufio.Writer)
• type HostEntry
• type Manager
  • func NewManager(logf logger.Logf, oscfg OSConfigurator, linkMon *monitor.Mon, ...) *Manager
  • func (m *Manager) Down() error
  • func (m *Manager) EnqueuePacket(bs []byte, proto ipproto.Proto, from, to netip.AddrPort) error
  • func (m *Manager) FlushCaches() error
  • func (m *Manager) HandleTCPConn(conn net.Conn, srcAddr netip.AddrPort)
  • func (m *Manager) NextPacket() ([]byte, error)
  • func (m *Manager) Query(ctx context.Context, bs []byte, from netip.AddrPort) ([]byte, error)
  • func (m *Manager) Resolver() *resolver.Resolver
  • func (m *Manager) Set(cfg Config) error
• type OSConfig
  • func (a OSConfig) Equal(b OSConfig) bool
  • func (a OSConfig) Format(f fmt.State, verb rune)
  • func (o OSConfig) IsZero() bool
• type OSConfigurator
  • func NewOSConfigurator(logf logger.Logf, interfaceName string) (ret OSConfigurator, err error)

Variables

var ErrGetBaseConfigNotSupported = errors.New("getting OS base config is not supported")

ErrGetBaseConfigNotSupported is the error OSConfigurator.GetBaseConfig returns when the OSConfigurator doesn't support reading the underlying configuration out of the OS.

Functions

func Cleanup

func Cleanup(logf logger.Logf, interfaceName string)

Cleanup restores the system DNS configuration to its original state in case the Tailscale daemon terminated without closing the router. No other state needs to be instantiated before this runs.

func NewNoopManager

func NewNoopManager() (noopManager, error)

Types

type Config

type Config struct {
	// DefaultResolvers are the DNS resolvers to use for DNS names
	// which aren't covered by more specific per-domain routes below.
	// If empty, the OS's default resolvers (the ones that predate
	// Tailscale altering the configuration) are used.
	DefaultResolvers []*dnstype.Resolver
	// Routes maps a DNS suffix to the resolvers that should be used
	// for queries that fall within that suffix.
	// If a query doesn't match any entry in Routes, the
	// DefaultResolvers are used.
	// A Routes entry with no resolvers means the route should be
	// authoritatively answered using the contents of Hosts.
	Routes map[dnsname.FQDN][]*dnstype.Resolver
	// SearchDomains are DNS suffixes to try when expanding
	// single-label queries.
	SearchDomains []dnsname.FQDN
	// Hosts maps DNS FQDNs to their IPs, which can be a mix of IPv4
	// and IPv6.
	// Queries matching entries in Hosts are resolved locally by
	// 100.100.100.100 without leaving the machine.
	// Adding an entry to Hosts merely creates the record. If you want
	// it to resolve, you also need to add appropriate routes to
	// Routes.
	Hosts map[dnsname.FQDN][]netip.Addr
	// OnlyIPv6, if true, uses the IPv6 service IP (for MagicDNS)
	// instead of the IPv4 version (100.100.100.100).
	OnlyIPv6 bool
}

Config is a DNS configuration.

func (*Config) WriteToBufioWriter

func (c *Config) WriteToBufioWriter(w *bufio.Writer)

WriteToBufioWriter write a debug version of c for logs to w, omitting spammy stuff like *.arpa entries and replacing it with a total count.

type HostEntry

type HostEntry struct {
	Addr  netip.Addr
	Hosts []string
}

HostEntry represents a single line in the OS's hosts file.

type Manager

type Manager struct {
	// contains filtered or unexported fields
}

Manager manages system DNS settings.

func NewManager

func NewManager(logf logger.Logf, oscfg OSConfigurator, linkMon *monitor.Mon, dialer *tsdial.Dialer, linkSel resolver.ForwardLinkSelector) *Manager

NewManagers created a new manager from the given config.

func (*Manager) Down

func (m *Manager) Down() error

func (*Manager) EnqueuePacket

func (m *Manager) EnqueuePacket(bs []byte, proto ipproto.Proto, from, to netip.AddrPort) error

EnqueuePacket is the legacy path for handling magic DNS traffic, and is called with a DNS request payload.

TODO(tom): Rip out once all platforms use netstack.

func (*Manager) FlushCaches

func (m *Manager) FlushCaches() error

func (*Manager) HandleTCPConn

func (m *Manager) HandleTCPConn(conn net.Conn, srcAddr netip.AddrPort)

HandleTCPConn implements magicDNS over TCP, taking a connection and servicing DNS requests sent down it.

func (*Manager) NextPacket

func (m *Manager) NextPacket() ([]byte, error)

NextPacket is the legacy path for obtaining DNS results in response to magic DNS queries. It blocks until a response is available.

TODO(tom): Rip out once all platforms use netstack.

func (*Manager) Query

func (m *Manager) Query(ctx context.Context, bs []byte, from netip.AddrPort) ([]byte, error)

Query executes a DNS query received from the given address. The query is provided in bs as a wire-encoded DNS query without any transport header. This method is called for requests arriving over UDP and TCP.

func (*Manager) Resolver

func (m *Manager) Resolver() *resolver.Resolver

Resolver returns the Manager's DNS Resolver.

func (*Manager) Set

func (m *Manager) Set(cfg Config) error

type OSConfig

type OSConfig struct {
	// Hosts is a map of DNS FQDNs to their IPs, which should be added to the
	// OS's hosts file. Currently, (2022-08-12) it is only populated for Windows
	// in SplitDNS mode and with Smart Name Resolution turned on.
	Hosts []*HostEntry
	// Nameservers are the IP addresses of the nameservers to use.
	Nameservers []netip.Addr
	// SearchDomains are the domain suffixes to use when expanding
	// single-label name queries. SearchDomains is additive to
	// whatever non-Tailscale search domains the OS has.
	SearchDomains []dnsname.FQDN
	// MatchDomains are the DNS suffixes for which Nameservers should
	// be used. If empty, Nameservers is installed as the "primary" resolver.
	// A non-empty MatchDomains requests a "split DNS" configuration
	// from the OS, which will only work with OSConfigurators that
	// report SupportsSplitDNS()=true.
	MatchDomains []dnsname.FQDN
}

OSConfig is an OS DNS configuration.

func (OSConfig) Equal

func (a OSConfig) Equal(b OSConfig) bool

func (OSConfig) Format

func (a OSConfig) Format(f fmt.State, verb rune)

Format implements the fmt.Formatter interface to ensure that Hosts is printed correctly (i.e. not as a bunch of pointers).

Fixes https://github.com/tailscale/tailscale/issues/5669

func (OSConfig) IsZero

func (o OSConfig) IsZero() bool

type OSConfigurator

type OSConfigurator interface {
	// SetDNS updates the OS's DNS configuration to match cfg.
	// If cfg is the zero value, all Tailscale-related DNS
	// configuration is removed.
	// SetDNS must not be called after Close.
	// SetDNS takes ownership of cfg.
	SetDNS(cfg OSConfig) error
	// SupportsSplitDNS reports whether the configurator is capable of
	// installing a resolver only for specific DNS suffixes. If false,
	// the configurator can only set a global resolver.
	SupportsSplitDNS() bool

	// Implementations that don't support getting the base config must
	// return ErrGetBaseConfigNotSupported.
	GetBaseConfig() (OSConfig, error)
	// Close removes Tailscale-related DNS configuration from the OS.
	Close() error
}

An OSConfigurator applies DNS settings to the operating system.

func NewOSConfigurator

func NewOSConfigurator(logf logger.Logf, interfaceName string) (ret OSConfigurator, err error)