FQDNs don't work with a trailing period on Cloud Run

[Ahmet Alp Balkan]

local dig:

$ dig +search A hello.us-central1.run.internal


; <<>> DiG 9.14.12 <<>> +search A hello.us-central1.run.internal
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 9556
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;hello.us-central1.run.internal.	IN	A

;; ANSWER SECTION:
hello.us-central1.run.internal.	10 IN	A	127.0.0.1

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Wed Oct 07 02:34:08 UTC 2020
;; MSG SIZE  rcvd: 94

remote dig:

$ dig +search A hello.us-central1.run.internal


; <<>> DiG 9.16.6 <<>> +search A hello.us-central1.run.internal
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 27459
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;hello.us-central1.run.internal.google.internal.	IN A

;; AUTHORITY SECTION:
internal.		30	IN	SOA	ns.global.gcedns-prod.internal. cloud-dns-hostmaster.google.com. 2015030600 7200 3600 24796800 5

;; Query time: 3 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Wed Oct 07 02:34:03 UTC 2020
;; MSG SIZE  rcvd: 169

both have NDOTS configured to 4

local log:

I1007 02:34:08.533319       1 dns.go:50] [dns] type=A name=hello.us-central1.run.internal.us-central1.run.internal. dots=7
I1007 02:34:08.533364       1 dns.go:58] [dns] type=A name=hello.us-central1.run.internal.us-central1.run.internal. is too short or long (need ndots=4; got=7), nxdomain
I1007 02:34:08.533916       1 dns.go:50] [dns] type=A name=hello.us-central1.run.internal.run.internal. dots=6
I1007 02:34:08.533961       1 dns.go:58] [dns] type=A name=hello.us-central1.run.internal.run.internal. is too short or long (need ndots=4; got=6), nxdomain
I1007 02:34:08.534366       1 dns.go:50] [dns] type=A name=hello.us-central1.run.internal. dots=4
I1007 02:34:08.534407       1 dns.go:77] [dns] MATCH type=A name=hello.us-central1.run.internal.

remote log:

I1007 02:34:03.692093 1 dns.go:50] [dns] type=A name=hello.us-central1.run.internal.us-central1.run.internal. dots=7
I1007 02:34:03.692121 1 dns.go:58] [dns] type=A name=hello.us-central1.run.internal.us-central1.run.internal. is too short or long (need ndots=4; got=7), nxdomain
I1007 02:34:03.692628 1 dns.go:50] [dns] type=A name=hello.us-central1.run.internal.run.internal. dots=6
I1007 02:34:03.692650 1 dns.go:58] [dns] type=A name=hello.us-central1.run.internal.run.internal. is too short or long (need ndots=4; got=6), nxdomain
I1007 02:34:03.692950 1 dns.go:108] [dns] recursing type=A name=hello.us-central1.run.internal.google.internal.
I1007 02:34:03.696508 1 dns.go:118] [dns] recursed type=A name=hello.us-central1.run.internal.google.internal. resp_code=0

for some reason, while remote it skips trying the 4-dot version.

local resolv conf:

nameserver 127.0.0.1
nameserver ::1
search us-central1.run.internal run.internal
options ndots:4

remote resolv.conf:

nameserver 127.0.0.1
nameserver ::1
search us-central1.run.internal run.internal google.internal.
options ndots:4

(the only difference is google.internal. domain being added).

This was the case also before removing trailing periods from search domains.