Recursive resolution doesn't work if 2+ labels down delegation (example: `domain.com` delegating `subdomain.label2.label1.domain.com` directly).

[kakwa]

dnsr seems to have issues resolving records if there is a 2+ labels down delegation in the mix.

As a test example, I've delegated subdeleg.notdel.notdel.notdel.notdel.kakwalab.ovh. (note the notdel intermediary labels) from kakwalab.ovh. and created an A test record record.subdeleg.notdel.notdel.notdel.notdel.kakwalab.ovh. with value 1.1.1.1.

package main

import (
    "fmt"
    "os"
    "github.com/domainr/dnsr"
)

func main() {
    // Create a new DNS resolver
    resolver := dnsr.NewResolver()

    // The IP to reverse lookup (PTR query)
    rec := "record.subdeleg.notdel.notdel.notdel.notdel.kakwalab.ovh."
    dnsr.MaxNameservers = 1
    dnsr.MaxIPs = 1
    dnsr.DebugLogger = os.Stdout

    // Query A record (nil)
    results := resolver.Resolve(rec, "A")
    fmt.Printf("%#v\n", results)

    // Query again (has response (thanks to cache?))
    // results = resolver.Resolve(rec, "A")
    // fmt.Printf("%#v\n", results)
}

Using the above code returns a nil object while dig record.subdeleg.notdel.notdel.notdel.notdel.kakwalab.ovh. A properly returns 1.1.1.1.

This seems to come from the fact dnsr only query for NS one label down.

This issue is common for PTR resolution.

Note:

• with cache, a second resolution is successful
• Draft PR for a fix: Return parent NS if no NS is found and query type is NS #147

[case-fastly]

@kakwa Apologies for the delay here, we did a bit of work on this in #147 and I wanted to circle back to the issue you filed.

Does it still need to be addressed, from your vantage point?

[kakwa]

I think the issue is still present:

Nil result for 8.8.8.8 reverse/PTR:

kakwa@tsingtao ~/tmp » ./testdnsr 
╭─── resolve("8.8.8.8.in-addr.arpa.", "PTR", 1)
│   ╭─── resolve("8.8.8.8.in-addr.arpa.", "NS", 2)
│   │   ╭─── resolve("8.8.8.in-addr.arpa.", "NS", 3)
│   │   │   ╭─── resolve("8.8.in-addr.arpa.", "NS", 4)
│   │   │   │   ╭─── resolve("8.in-addr.arpa.", "NS", 5)
│   │   │   │   │   ╭─── resolve("in-addr.arpa.", "NS", 6)
│   │   │   │   │   │   ╭─── resolve("arpa.", "NS", 7)
│   │   │   │   │   │   │    63ms (T- 1999ms): dig +norecurse @g.root-servers.net. arpa. NS  # rmsg: NOERROR Answer: 12 NS: 0 Extra: 15
│   │   │   │   │   │   ╰─── 63ms: resolve("arpa.", "NS", 7) # [24]RR = NS(arpa.)=e.ns.arpa. NS(arpa.)=d.ns.arpa. ...
│   │   │   │   │   │    3ms (T- 1936ms): dig +norecurse @e.ns.arpa. in-addr.arpa. NS  # rmsg: NOERROR Answer: 0 NS: 6 Extra: 12
│   │   │   │   │   ╰─── 67ms: resolve("in-addr.arpa.", "NS", 6) # [12]RR = NS(in-addr.arpa.)=a.in-addr-servers.arpa. NS(in-addr.arpa.)=b.in-addr-servers.arpa. ...
│   │   │   │   │    101ms (T- 1932ms): dig +norecurse @a.in-addr-servers.arpa. 8.in-addr.arpa. NS  # rmsg: NOERROR Answer: 0 NS: 6 Extra: 0
│   │   │   │   │   │    79ms (T- 1831ms): dig +norecurse @a.in-addr-servers.arpa. u.arin.net. A  # rmsg: REFUSED Answer: 0 NS: 0 Extra: 0
│   │   │   │   │   │    82ms (T- 1751ms): dig +norecurse @a.in-addr-servers.arpa. arin.authdns.ripe.net. A  # rmsg: REFUSED Answer: 0 NS: 0 Extra: 0
│   │   │   │   │   │    102ms (T- 1668ms): dig +norecurse @a.in-addr-servers.arpa. y.arin.net. A  # rmsg: REFUSED Answer: 0 NS: 0 Extra: 0
│   │   │   │   │   │    81ms (T- 1566ms): dig +norecurse @a.in-addr-servers.arpa. z.arin.net. A  # rmsg: REFUSED Answer: 0 NS: 0 Extra: 0
│   │   │   │   │   │    98ms (T- 1484ms): dig +norecurse @a.in-addr-servers.arpa. r.arin.net. A  # rmsg: REFUSED Answer: 0 NS: 0 Extra: 0
│   │   │   │   │   │    99ms (T- 1385ms): dig +norecurse @a.in-addr-servers.arpa. x.arin.net. A  # rmsg: REFUSED Answer: 0 NS: 0 Extra: 0
│   │   │   │   ╰─── 713ms: resolve("8.in-addr.arpa.", "NS", 5) # [6]RR = NS(8.in-addr.arpa.)=u.arin.net. NS(8.in-addr.arpa.)=arin.authdns.ripe.net. ...
│   │   │   │   ╭─── resolve("u.arin.net.", "A", 5)
│   │   │   │   │   ╭─── resolve("u.arin.net.", "NS", 6)
│   │   │   │   │   │   ╭─── resolve("arin.net.", "NS", 7)
│   │   │   │   │   │   │   ╭─── resolve("net.", "NS", 8)
│   │   │   │   │   │   │   │    14ms (T- 1286ms): dig +norecurse @i.root-servers.net. net. NS  # rmsg: NOERROR Answer: 0 NS: 13 Extra: 15
│   │   │   │   │   │   │   ╰─── 14ms: resolve("net.", "NS", 8) # [26]RR = NS(net.)=f.gtld-servers.net. NS(net.)=l.gtld-servers.net. ...
│   │   │   │   │   │   │    11ms (T- 1272ms): dig +norecurse @f.gtld-servers.net. arin.net. NS  # rmsg: NOERROR Answer: 0 NS: 4 Extra: 8
│   │   │   │   │   │   ╰─── 26ms: resolve("arin.net.", "NS", 7) # [8]RR = NS(arin.net.)=ns1.arin.net. NS(arin.net.)=ns2.arin.net. ...
│   │   │   │   │   │    79ms (T- 1260ms): dig +norecurse @ns1.arin.net. u.arin.net. NS  # rmsg: NOERROR Answer: 0 NS: 1 Extra: 0
│   │   │   │   │   ╰─── 105ms: resolve("u.arin.net.", "NS", 6) # [1]RR = A(u.arin.net.)=204.61.216.50 
│   │   │   │   ╰─── 105ms: resolve("u.arin.net.", "A", 5) # [1]RR = A(u.arin.net.)=204.61.216.50 
│   │   │   │    3ms (T- 1180ms): dig +norecurse @u.arin.net. 8.8.in-addr.arpa. NS  # rmsg: NOERROR Answer: 0 NS: 1 Extra: 0
│   │   │   ╰─── 822ms: resolve("8.8.in-addr.arpa.", "NS", 4) # rrs = nil 
│   │   ╰─── 822ms: resolve("8.8.8.in-addr.arpa.", "NS", 3) # rrs = nil 
│   ╰─── 822ms: resolve("8.8.8.8.in-addr.arpa.", "NS", 2) # rrs = nil 
│   ╭─── resolve("8.8.8.in-addr.arpa.", "NS", 2)
│   │   ╭─── resolve("8.8.in-addr.arpa.", "NS", 3)
│   │   │    2ms (T- 1177ms): dig +norecurse @u.arin.net. 8.8.in-addr.arpa. NS  # rmsg: NOERROR Answer: 0 NS: 1 Extra: 0
│   │   ╰─── 2ms: resolve("8.8.in-addr.arpa.", "NS", 3) # rrs = nil 
│   ╰─── 2ms: resolve("8.8.8.in-addr.arpa.", "NS", 2) # rrs = nil 
│   ╭─── resolve("8.8.in-addr.arpa.", "NS", 2)
│   │    3ms (T- 1174ms): dig +norecurse @u.arin.net. 8.8.in-addr.arpa. NS  # rmsg: NOERROR Answer: 0 NS: 1 Extra: 0
│   ╰─── 3ms: resolve("8.8.in-addr.arpa.", "NS", 2) # rrs = nil 
│   ╭─── resolve("z.arin.net.", "A", 2)
│   │   ╭─── resolve("z.arin.net.", "NS", 3)
│   │   │    80ms (T- 1170ms): dig +norecurse @ns1.arin.net. z.arin.net. NS  # rmsg: NOERROR Answer: 0 NS: 1 Extra: 0
│   │   ╰─── 80ms: resolve("z.arin.net.", "NS", 3) # rrs = nil 
│   │    80ms (T- 1089ms): dig +norecurse @ns1.arin.net. z.arin.net. A  # rmsg: NOERROR Answer: 1 NS: 0 Extra: 0
│   ╰─── 161ms: resolve("z.arin.net.", "A", 2) # [1]RR = A(z.arin.net.)=199.180.180.63 
│    79ms (T- 1009ms): dig +norecurse @z.arin.net. 8.8.8.8.in-addr.arpa. PTR  # rmsg: NOERROR Answer: 0 NS: 4 Extra: 0
╰─── 1070ms: resolve("8.8.8.8.in-addr.arpa.", "PTR", 1) # rrs = nil 
=======================================
dnsr.RRs(nil)

But the value should actually be dns.google.:

kakwa@tsingtao ~/tmp » dig PTR +short 8.8.8.8.in-addr.arpa.
dns.google.

Versions used:

kakwa@tsingtao ~/tmp » cat go.mod 
module example.com/testdnsr

go 1.24.9

require (
	github.com/domainr/dnsr v0.0.0-20260123205859-058158ac5975 // indirect
	github.com/miekg/dns v1.1.70 // indirect
	golang.org/x/mod v0.31.0 // indirect
	golang.org/x/net v0.49.0 // indirect
	golang.org/x/sync v0.19.0 // indirect
	golang.org/x/sys v0.40.0 // indirect
	golang.org/x/tools v0.40.0 // indirect
)

Quick test:

package main

import (
    "fmt"
    "os"
    "github.com/domainr/dnsr"
)

func main() {
    // Create a new DNS resolver
    resolver := dnsr.NewResolver()

    // The IP to reverse lookup (PTR query)
    dnsr.MaxNameservers = 1
    dnsr.MaxIPs = 1
    dnsr.DebugLogger = os.Stdout

    // Query A record (nil)
    rrs, err := resolver.ResolveErr("8.8.8.8.in-addr.arpa", "PTR")
    fmt.Printf("=======================================\n")
    if err != nil {
        fmt.Printf("%e\n", err)
    }
    fmt.Printf("%#v\n", rrs)
}

test go mod:
testdnsr.tar.gz

[case-fastly]

This is addressed in #201.