[Pdns-users] Recursor and LUA scripting: I don't understand why preresolve answering a CNAME won't cascade to other records

[Oscar Koeroo via Pdns-users]

Hi,

I’m using my the Recursor version 4.3.1 on my Pi and building the following. I 
have a VPS and a home-server. I use “domain.net” for the internet access and in 
my home I use “domain.local”.

Due to NAT and how my home router works, I intercept the DNS requests and 
provide a local answer instead of the WAN IP address for example. In other case 
I would like to use “domain.net” 


I’m using the following LUA script to intercept, but I don’t understand the 
results. Why doesn’t the dig get the CNAME to got to the A record I have in my 
domain.local zone? I expected dig to try to get the CNAME value of 
qr.domain.net and the CNAME value of that result, which seems to halt there.




The expected result I was looking for was:


dig qr.domain.net

;; ANSWER SECTION:
qr.domain.net.          3600    IN      CNAME   qr.domain.local.
qr.domain.local.        41584   IN      CNAME   apps.domain.local.
apps.koeroo.local.      40931   IN      A       192.168.1.28
- EOL



I got:


dig qr.domain.net

;; ANSWER SECTION:
qr.domain.net.          3600    IN      CNAME   qr.domain.local.
- EOL


dig cloud.domain.net

;; ANSWER SECTION:
cloud.domain.net.       3600    IN      A       192.168.1.15
- EOL



Script:

function preresolve(dq)
    if dq.qtype == pdns.A then
        if (dq.qname:toString() == "cloud.domain.net.") then
            pdnslog("preresolve: " .. dq.qname:toString(), pdns.loglevels.Info)
            dq:addAnswer(pdns.A, "192.168.1.15")
            dq.rcode = pdns.NOERROR
            return true
        elseif (dq.qname:toString() == "vpn.domain.net.") then
            pdnslog("preresolve: " .. dq.qname:toString(), pdns.loglevels.Info)
            dq:addAnswer(pdns.A, "192.168.1.37")
            dq.rcode = pdns.NOERROR
            return true
        elseif (dq.qname:toString() == "qr.domain.net.") then
            pdnslog("preresolve: " .. dq.qname:toString(), pdns.loglevels.Info)
            dq:addAnswer(pdns.CNAME, "qr.domain.local")
            dq.rcode = pdns.NOERROR
            return true
        end
    end
    return false
end


Oscar Koeroo



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