Stop handling a domain if all nameservers don't provide sufficient glue records when they should

[phillip-stephens]

Description

Wanted to get a specific review on this since it seems to core logic that affects more than just IPv6 lookups.

The issue that caused me to look into this was trying to get A records for esrg.stanford.edu from Stanford.edu nameservers over IPv6

$ dig -t A esrg.stanford.edu @avallone.stanford.edu -6

; <<>> DiG 9.10.6 <<>> -t A esrg.stanford.edu @avallone.stanford.edu -6
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20243
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 3
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;esrg.stanford.edu.		IN	A

;; AUTHORITY SECTION:
esrg.stanford.edu.	1800	IN	NS	dns-02.esrg.stanford.edu.
esrg.stanford.edu.	1800	IN	NS	dns-01.esrg.stanford.edu.

;; ADDITIONAL SECTION:
dns-02.esrg.stanford.edu. 1800	IN	A	171.67.68.26
dns-01.esrg.stanford.edu. 1800	IN	A	171.67.68.25

;; Query time: 84 msec
;; SERVER: 2620:6c:40c0:0:204:63:224:53#53(2620:6c:40c0:0:204:63:224:53)
;; WHEN: Mon Aug 12 12:17:07 EDT 2024
;; MSG SIZE  rcvd: 120

We can't proceed to look up dns-01.esrg.stanford.edu any further, and without an AAAA record to continue IPv6 iteration, we cannot proceed.

Solution

• Add a new NONEEDEDGLUE status that is returned if a given name is beneath the current layer (esrg.stanford.edu is beneath Stanford.edu and the glue doesn't contain a next hop.)
• If all authorities in iterateOnAuthorities return this, we'll terminate the iteration

Testing

esrg.stanford.edu lookup

ipv6 base branch

$ echo "esrg.stanford.edu" | ./zdns A --6 --iterative
{"data":{"protocol":"","resolver":""},"duration":15.001968875,"name":"esrg.stanford.edu","status":"TIMEOUT","timestamp":"2024-08-12T12:22:51-04:00"}

ipv6-recursive-base

$ echo "esrg.stanford.edu" | ./zdns A --6 --iterative
{"data":{"protocol":"","resolver":""},"duration":0.21923125,"name":"esrg.stanford.edu","status":"NONEEDEDGLUE","timestamp":"2024-08-12T12:23:26-04:00"}

Ensuring this doesn't break known working domains

main

Benchmarking ZDNS, Resolving 2000 domains... 100% 
Benchmark took:                                                       23.12s
Min resolution time:                                                 27.35µs
Max resolution time:                                                  15.00s
Average resolution time:                                            744.78ms

Domains resolved successfully:                                     1830/2000
Domains that timed out:                                                  152
Domains that failed:                                                      18

ipv6-recursive-base

~/zdns on  phillip/ipv6-recursive-base! ⌚ 16:24:40
$ make benchmark
go build -o zdns
cd ./benchmark && go run main.go stats.go
Benchmarking ZDNS, Resolving 2000 domains... 100% 
Benchmark took:                                                       23.98s
Min resolution time:                                                 28.17µs
Max resolution time:                                                  15.00s

Domains resolved successfully:                                     1803/2000
Domains that timed out:                                                  180
Domains that failed:                                                      17