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tailscale/net/dns/config.go

124 lines
3.4 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 dns
import (
"sort"
"inet.af/netaddr"
"tailscale.com/util/dnsname"
)
// Config is a DNS configuration.
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 []netaddr.IPPort
// 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.
Routes map[dnsname.FQDN][]netaddr.IPPort
// 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 without
// recursing off-machine.
Hosts map[dnsname.FQDN][]netaddr.IP
// AuthoritativeSuffixes is a list of fully-qualified DNS suffixes
// for which the in-process Tailscale resolver is authoritative.
// Queries for names within AuthoritativeSuffixes can only be
// fulfilled by entries in Hosts. Queries with no match in Hosts
// return NXDOMAIN.
AuthoritativeSuffixes []dnsname.FQDN
}
// needsAnyResolvers reports whether c requires a resolver to be set
// at the OS level.
func (c Config) needsOSResolver() bool {
return c.hasDefaultResolvers() || c.hasRoutes() || c.hasHosts()
}
func (c Config) hasRoutes() bool {
return len(c.Routes) > 0
}
// hasDefaultResolversOnly reports whether the only resolvers in c are
// DefaultResolvers.
func (c Config) hasDefaultResolversOnly() bool {
return c.hasDefaultResolvers() && !c.hasRoutes() && !c.hasHosts()
}
func (c Config) hasDefaultResolvers() bool {
return len(c.DefaultResolvers) > 0
}
// singleResolverSet returns the resolvers used by c.Routes if all
// routes use the same resolvers, or nil if multiple sets of resolvers
// are specified.
func (c Config) singleResolverSet() []netaddr.IPPort {
var first []netaddr.IPPort
for _, resolvers := range c.Routes {
if first == nil {
first = resolvers
continue
}
if !sameIPPorts(first, resolvers) {
return nil
}
}
return first
}
// hasHosts reports whether c requires resolution of MagicDNS hosts or
// domains.
func (c Config) hasHosts() bool {
return len(c.Hosts) > 0 || len(c.AuthoritativeSuffixes) > 0
}
// matchDomains returns the list of match suffixes needed by Routes,
// AuthoritativeSuffixes. Hosts is not considered as we assume that
// they're covered by AuthoritativeSuffixes for now.
func (c Config) matchDomains() []dnsname.FQDN {
ret := make([]dnsname.FQDN, 0, len(c.Routes)+len(c.AuthoritativeSuffixes))
seen := map[dnsname.FQDN]bool{}
for _, suffix := range c.AuthoritativeSuffixes {
if seen[suffix] {
continue
}
ret = append(ret, suffix)
seen[suffix] = true
}
for suffix := range c.Routes {
if seen[suffix] {
continue
}
ret = append(ret, suffix)
seen[suffix] = true
}
sort.Slice(ret, func(i, j int) bool {
return ret[i].WithTrailingDot() < ret[j].WithTrailingDot()
})
return ret
}
func sameIPPorts(a, b []netaddr.IPPort) bool {
if len(a) != len(b) {
return false
}
for i := range a {
if a[i] != b[i] {
return false
}
}
return true
}