// lookupNameservers returns the authoritative nameservers for the given fqdn.
func lookupNameservers(fqdn string) ([]string, error) {
var authoritativeNss []string
r, err := dnsQuery(fqdn, dns.TypeNS, recursiveNameserver, true)
if err != nil {
return nil, err
}
for _, rr := range r.Answer {
if ns, ok := rr.(*dns.NS); ok {
authoritativeNss = append(authoritativeNss, strings.ToLower(ns.Ns))
}
}
if len(authoritativeNss) > 0 {
return authoritativeNss, nil
}
// Strip of the left most label to get the parent domain.
offset, _ := dns.NextLabel(fqdn, 0)
next := fqdn[offset:]
if dns.CountLabel(next) < 2 {
return nil, fmt.Errorf("Could not determine authoritative nameservers")
}
return lookupNameservers(next)
}
// needFromPunycode returns true for strings that require punycode decoding.
func needFromPunycode(s string) bool {
if s == "." {
return false
}
off := 0
end := false
pl := len(_PREFIX)
sl := len(s)
// If s starts with _PREFIX.
if sl > pl && s[off:off+pl] == _PREFIX {
return true
}
for {
// Find the part after the next ".".
off, end = dns.NextLabel(s, off)
if end {
return false
}
// If this parts starts with _PREFIX.
if sl-off > pl && s[off:off+pl] == _PREFIX {
return true
}
}
}
// ClosestEncloser returns the closest encloser for rr.
func (z *Zone) ClosestEncloser(qname string, qtype uint16) string {
// tree/tree.go does not store a parent *Node pointer, so we can't
// just follow up the tree. TODO(miek): fix.
offset, end := dns.NextLabel(qname, 0)
for !end {
elem, _ := z.Tree.Search(qname, qtype)
if elem != nil {
return elem.Name()
}
qname = qname[offset:]
offset, end = dns.NextLabel(qname, offset)
}
return z.Apex.SOA.Header().Name
}
func (zs *ZoneStore) match(q string, t uint16) (*Zone, string) {
zs.RLock()
defer zs.RUnlock()
var zone *Zone
var name string
b := make([]byte, len(q)) // worst case, one label of length q
off := 0
end := false
for {
l := len(q[off:])
for i := 0; i < l; i++ {
b[i] = q[off+i]
if b[i] >= 'A' && b[i] <= 'Z' {
b[i] |= ('a' - 'A')
}
}
if z, ok := zs.store[string(b[:l])]; ok { // 'causes garbage, might want to change the map key
if t != dns.TypeDS {
return &z, string(b[:l])
}
// Continue for DS to see if we have a parent too, if so delegate to the parent
zone = &z
name = string(b[:l])
}
off, end = dns.NextLabel(q, off)
if end {
break
}
}
return zone, name
}
// NewMX returns a new MX record based on the Service.
func (s *Service) NewMX(name string) *dns.MX {
host := dns.Fqdn(s.Host)
offset, end := 0, false
for i := 0; i < s.TargetStrip; i++ {
offset, end = dns.NextLabel(host, offset)
}
if end {
// We overshot the name, use the orignal one.
offset = 0
}
host = host[offset:]
return &dns.MX{Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypeMX, Class: dns.ClassINET, Ttl: s.Ttl},
Preference: uint16(s.Priority), Mx: host}
}
// NewSRV returns a new SRV record based on the Service.
func (s *Service) NewSRV(name string, weight uint16) *dns.SRV {
host := dns.Fqdn(s.Host)
offset, end := 0, false
for i := 0; i < s.TargetStrip; i++ {
offset, end = dns.NextLabel(host, offset)
}
if end {
// We overshot the name, use the orignal one.
offset = 0
}
host = host[offset:]
return &dns.SRV{Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypeSRV, Class: dns.ClassINET, Ttl: s.Ttl},
Priority: uint16(s.Priority), Weight: weight, Port: uint16(s.Port), Target: host}
}
// targetStrip strips "targetstrip" labels from the left side of the fully qualified name.
func targetStrip(name string, targetStrip int) string {
if targetStrip == 0 {
return name
}
offset, end := 0, false
for i := 0; i < targetStrip; i++ {
offset, end = dns.NextLabel(name, offset)
}
if end {
// We overshot the name, use the orignal one.
offset = 0
}
name = name[offset:]
return name
}
// ServeDNS is the entry point for every request to the address that s
// is bound to. It acts as a multiplexer for the requests zonename as
// defined in the request so that the correct zone
// (configuration and middleware stack) will handle the request.
func (s *Server) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
defer func() {
// In case the user doesn't enable error middleware, we still
// need to make sure that we stay alive up here
if rec := recover(); rec != nil {
DefaultErrorFunc(w, r, dns.RcodeServerFailure)
}
}()
if m, err := middleware.Edns0Version(r); err != nil { // Wrong EDNS version, return at once.
rc := middleware.RcodeToString(dns.RcodeBadVers)
state := middleware.State{W: w, Req: r}
metrics.Report(state, metrics.Dropped, rc, m.Len(), time.Now())
w.WriteMsg(m)
return
}
// Execute the optional request callback if it exists
if s.ReqCallback != nil && s.ReqCallback(w, r) {
return
}
q := r.Question[0].Name
b := make([]byte, len(q))
off, end := 0, false
ctx := context.Background()
for {
l := len(q[off:])
for i := 0; i < l; i++ {
b[i] = q[off+i]
// normalize the name for the lookup
if b[i] >= 'A' && b[i] <= 'Z' {
b[i] |= ('a' - 'A')
}
}
if h, ok := s.zones[string(b[:l])]; ok {
if r.Question[0].Qtype != dns.TypeDS {
rcode, _ := h.stack.ServeDNS(ctx, w, r)
if RcodeNoClientWrite(rcode) {
DefaultErrorFunc(w, r, rcode)
}
return
}
}
off, end = dns.NextLabel(q, off)
if end {
break
}
}
// Wildcard match, if we have found nothing try the root zone as a last resort.
if h, ok := s.zones["."]; ok {
rcode, _ := h.stack.ServeDNS(ctx, w, r)
if RcodeNoClientWrite(rcode) {
DefaultErrorFunc(w, r, rcode)
}
return
}
// Still here? Error out with REFUSED and some logging
remoteHost := w.RemoteAddr().String()
DefaultErrorFunc(w, r, dns.RcodeRefused)
log.Printf("[INFO] \"%s %s %s\" - No such zone at %s (Remote: %s)", dns.Type(r.Question[0].Qtype), dns.Class(r.Question[0].Qclass), q, s.Addr, remoteHost)
}
