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Update parameters for clarity

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Hijack the final A record in a CNAME chain if it is in our records
This commit is contained in:
lordwelch 2021-05-23 17:49:15 -07:00
parent 9ee285e139
commit 29eaa11052
1 changed files with 16 additions and 4 deletions
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20
internal/dns/dns.go
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@ -227,10 +227,10 @@ func (s *Server) hostByIP(n string) (string, bool) {
return r, ok
}
func (s *Server) subname(hostname, host string) (IP, bool) {
func (s *Server) subname(domain, host string) (IP, bool) {
s.mu.Lock()
defer s.mu.Unlock()
r, ok := s.subnames[lcHostname(strings.ToLower(hostname))][lcHostname(strings.ToLower(host))]
r, ok := s.subnames[lcHostname(strings.ToLower(domain))][lcHostname(strings.ToLower(host))]
return r, ok
}
@ -544,6 +544,18 @@ func (s *Server) handleRequest(w dns.ResponseWriter, r *dns.Msg) {
}
continue // fall back to next-slower upstream
}
if len(in.Answer) > 1 {
if in.Answer[0].Header().Rrtype == dns.TypeCNAME {
for _, rr := range in.Answer {
if rr.Header().Rrtype == dns.TypeA {
if newRR, err := s.resolveSubname("", dns.Question{strings.ToLower(rr.Header().Name), dns.TypeA, dns.ClassINET}); err != nil {
in.Answer[len(in.Answer)-1] = newRR
}
}
}
}
}
w.WriteMsg(in)
if idx > 0 {
// re-order this upstream to the front of s.upstream.
@ -587,13 +599,13 @@ func (s *Server) promInc(label string, r *dns.Msg) {
s.prom.upstream.WithLabelValues(label).Inc()
}
func (s *Server) subnameHandler(hostname lcHostname) func(w dns.ResponseWriter, r *dns.Msg) {
func (s *Server) subnameHandler(domain lcHostname) func(w dns.ResponseWriter, r *dns.Msg) {
return func(w dns.ResponseWriter, r *dns.Msg) {
if len(r.Question) != 1 { // TODO: answer all questions we can answer
s.promInc("local", r)
return
}
rr, err := s.resolveSubname(string(hostname), r.Question[0])
rr, err := s.resolveSubname(string(domain), r.Question[0])
if err != nil {
s.promInc("local", r)