dns

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

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.
	MatchDomains []dnsname.FQDN
}

type OSConfigurator interface {
	// SetDNS updates the OS's DNS configuration to match cfg.
	// If cfg is the zero value, all ctrld-related DNS
	// configuration is removed.
	// SetDNS must not be called after Close.
	// SetDNS takes ownership of cfg.
	SetDNS(cfg OSConfig) error

	// Close removes ctrld-related DNS configuration from the OS.
	Close() error

	Mode() string
}