func answerCNAME(q *dns.Question, v *DNSValue) (dns.RR, string) {
// Info: http://en.wikipedia.org/wiki/CNAME_record
answer := new(dns.CNAME)
answer.Header().Name = q.Name
answer.Header().Rrtype = dns.TypeCNAME
answer.Header().Class = dns.ClassINET
answer.Target = strings.TrimSuffix(v.Value, ".") + "."
return answer, answer.Target
}
func (c *config) flattenCNAME(in *dns.CNAME) ([]dns.RR, error) { // TODO: cache CNAME lookups
h := in.Header()
answers := []dns.RR{}
m := new(dns.Msg)
m.SetQuestion(in.Target, dns.TypeA)
m.RecursionDesired = true
d := new(dns.Client)
record, _, err := d.Exchange(m, c.resolver) // TODO: try multiple resolvers
if err != nil {
return nil, err
}
if record == nil || record.Rcode == dns.RcodeNameError || record.Rcode != dns.RcodeSuccess {
return nil, fmt.Errorf("Record error code %s: %s", record.Rcode, err.Error())
}
for _, a := range record.Answer {
if r, ok := a.(*dns.A); ok {
out := new(dns.A)
out.Hdr = dns.RR_Header{Name: h.Name, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 300}
out.A = r.A
answers = append(answers, out)
}
}
return answers, nil
}
// forwardSearch resolves a query by suffixing with search paths
func (s *server) forwardSearch(req *dns.Msg, tcp bool) (*dns.Msg, error) {
var r *dns.Msg
var nodata *dns.Msg // stores the copy of a NODATA reply
var searchName string // stores the current name suffixed with search domain
var err error
var didSearch bool
name := req.Question[0].Name // original qname
reqCopy := req.Copy()
for _, domain := range s.config.SearchDomains {
if strings.HasSuffix(name, domain) {
continue
}
searchName = strings.ToLower(appendDomain(name, domain))
reqCopy.Question[0] = dns.Question{searchName, reqCopy.Question[0].Qtype, reqCopy.Question[0].Qclass}
didSearch = true
r, err = s.forwardQuery(reqCopy, tcp)
if err != nil {
// No server currently available, give up
break
}
switch r.Rcode {
case dns.RcodeSuccess:
// In case of NO_DATA keep searching, otherwise a wildcard entry
// could keep us from finding the answer higher in the search list
if len(r.Answer) == 0 && !r.MsgHdr.Truncated {
nodata = r.Copy()
continue
}
case dns.RcodeNameError:
fallthrough
case dns.RcodeServerFailure:
// try next search element if any
continue
}
// anything else implies that we are done searching
break
}
if !didSearch {
m := new(dns.Msg)
m.SetRcode(req, dns.RcodeNameError)
return m, nil
}
if err == nil {
if r.Rcode == dns.RcodeSuccess {
if len(r.Answer) > 0 {
cname := new(dns.CNAME)
cname.Hdr = dns.RR_Header{Name: name, Rrtype: dns.TypeCNAME, Class: dns.ClassINET, Ttl: 360}
cname.Target = searchName
answers := []dns.RR{cname}
for _, rr := range r.Answer {
answers = append(answers, rr)
}
r.Answer = answers
}
// If we ever got a NODATA, return this instead of a negative result
} else if nodata != nil {
r = nodata
}
// Restore original question
r.Question[0] = req.Question[0]
}
if err != nil && nodata != nil {
r = nodata
r.Question[0] = req.Question[0]
err = nil
}
return r, err
}
// TODO(axw) define an error for "no answer"
func (s *jujuNameServer) answer(q dns.Question) (dns.RR, error) {
if q.Qtype != dns.TypeA {
return nil, nil
}
var envName string
entityName := strings.ToLower(strings.TrimSuffix(q.Name, "."+zone))
if i := strings.IndexRune(entityName, '.'); i >= 0 {
envName = entityName[i+1:]
entityName = entityName[:i]
} else {
var err error
envName, err = envcmd.GetDefaultEnvironment()
if err != nil {
return nil, err
}
}
// TODO(axw) cache API connection
api, err := s.openAPI(envName)
if err != nil {
return nil, err
}
defer api.Close()
client := api.Client()
// If the entity name parses as a tag, extract the ID. This enables
// us to address "unit-mysql-0", where we couldn't otherwise, since
// slashes are not allowed in domain names. Similarly for container
// machines (e.g. to address "0/lxc/0", pass "machine-0-lxc-0").
if tag, err := names.ParseTag(entityName); err == nil {
entityName = tag.Id()
}
var addr string
if names.IsValidService(entityName) {
status, err := client.Status([]string{entityName})
if err != nil {
return nil, err
}
service := status.Services[entityName]
addresses := make([]string, 0, len(service.Units))
for _, unit := range service.Units {
if unit.PublicAddress == "" {
continue
}
if includeLost || unit.UnitAgent.Status != "lost" {
addresses = append(addresses, unit.PublicAddress)
}
}
// Might be nice to have additional info in TXT?
if len(addresses) == 0 {
return nil, nil
}
addr = addresses[rand.Intn(len(addresses))]
} else {
// Assume it's a machine or unit name.
addr, err = client.PublicAddress(entityName)
if err != nil {
return nil, err
}
}
ip := net.ParseIP(addr)
if ip != nil {
rr := new(dns.A)
rr.Hdr = dns.RR_Header{
Name: q.Name,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
Ttl: 0,
}
rr.A = ip
return rr, nil
} else {
rr := new(dns.CNAME)
rr.Hdr = dns.RR_Header{
Name: q.Name,
Rrtype: dns.TypeCNAME,
Class: dns.ClassINET,
Ttl: 0,
}
rr.Target = addr + "."
return rr, nil
}
}