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nicolasbeusen
Feb 19, 2025

Hello,

I would like to return a CNAME with value sinkhole.domain.xx if the A request is made on not allowed domain.

Basically, if my plugin receives a A request for baddomain.xyz, I would like to return a CNAME to sinkhole.abc

This is what I tried:

`
state := request.Request{W: w, Req: r}

answers := []dns.RR{}

cn := new(dns.CNAME)
cn.Hdr = dns.RR_Header{Name: state.Name(), Rrtype: dns.TypeCNAME, Class: dns.ClassINET, Ttl: 300}
cn.Target = "sinkhole.domain.xx"
answers = append(answers, cn)

switch state.Type() {
case "A":
	rr := new(dns.A)
	rr.Hdr = dns.RR_Header{Name: "sinkhole.domain.xx", Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 300}
	rr.A = net.ParseIP(sinkHoleIpv4)
	answers = append(answers, rr)
case "AAAA":
	rr := new(dns.AAAA)
	rr.Hdr = dns.RR_Header{Name: "sinkhole.domain.xx", Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: 300}
	rr.AAAA = net.ParseIP(sinkHoleIpv6)
	answers = append(answers, rr)
}


m := new(dns.Msg)
m.SetReply(r)
m.Question[0].Name = "sinkhole.domain.xx
m.Authoritative = true
m.Answer = answers

w.WriteMsg(m)
return dns.RcodeSuccess

Unfortunatly, I see a response in the console:
[INFO] 127.0.0.1:43986 - 49064 "A IN 0-1x.8632152.xyz. udp 34 false 512" NOERROR qr,aa,rd 112 0.000613969s
`

But nothing on the network... and so my nslookup returns:

`

0-1x.8632152.xyz
;; communications error to 127.0.0.1#1053: timed out
;; communications error to 127.0.0.1#1053: timed out
;; communications error to 127.0.0.1#1053: timed out
;; no servers could be reached

`

Do you have an idea what I'm doing wrong ?

THanks for your feedback.
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Replies: 1 comment · 1 reply

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rdrozhdzh
Feb 20, 2025
Collaborator

you should not change the question name in response, it should be the same as in query
You must be logged in to vote
1 reply
@nicolasbeusen
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nicolasbeusen Mar 16, 2025
Author

Thanks for feedback.
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