fix(docs): fix dig commands for each CoreDNS instance in local tutorial

[mattwelke]

Resolves #1830.

Fixes the commands by removing "+tcp" from them, so that dig uses UDP instead.

Error before:

;; communications error to 127.0.0.1#5053: connection reset
;; communications error to 127.0.0.1#5053: connection reset
;; communications error to 127.0.0.1#5053: connection reset

; <<>> DiG 9.18.30-0ubuntu0.24.04.2-Ubuntu <<>> -p 5053 @localhost localtargets-roundrobin.cloud.example.com +tcp
; (1 server found)
;; global options: +cmd
;; no servers could be reached

Output after (example):

; <<>> DiG 9.18.30-0ubuntu0.24.04.2-Ubuntu <<>> -p 5053 @localhost localtargets-roundrobin.cloud.example.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 51033
;; flags: qr rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
; COOKIE: 507a607e1c0ee13c (echoed)
;; QUESTION SECTION:
;localtargets-roundrobin.cloud.example.com. IN A

;; ANSWER SECTION:
localtargets-roundrobin.cloud.example.com. 30 IN A 172.19.0.4
localtargets-roundrobin.cloud.example.com. 30 IN A 172.19.0.5

;; Query time: 0 msec
;; SERVER: 127.0.0.1#5053(localhost) (UDP)
;; WHEN: Wed Feb 12 18:20:01 EST 2025
;; MSG SIZE  rcvd: 196


; <<>> DiG 9.18.30-0ubuntu0.24.04.2-Ubuntu <<>> -p 5054 @localhost localtargets-roundrobin.cloud.example.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4687
;; flags: qr rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
; COOKIE: 16704ecdcd80ad83 (echoed)
;; QUESTION SECTION:
;localtargets-roundrobin.cloud.example.com. IN A

;; ANSWER SECTION:
localtargets-roundrobin.cloud.example.com. 30 IN A 172.19.0.7
localtargets-roundrobin.cloud.example.com. 30 IN A 172.19.0.8

;; Query time: 0 msec
;; SERVER: 127.0.0.1#5054(localhost) (UDP)
;; WHEN: Wed Feb 12 18:20:02 EST 2025
;; MSG SIZE  rcvd: 196

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[k0da]

LGTM

[k0da]

Although Colima on MacOS can't forward UDP traffic, so we setup TCP there

[mattwelke]

Ah so it's a Mac vs. Linux thing. Do you know if there's a way to write a command that works on both?

[kuritka]

Hi @mattwelke , The long story short, the Docker Desktop has strict licensing requirements for using in corporations. It is not free, so instead of Docker Desktop, Colima was chosen. Unfortunately, Colima does not support UDP, so we explicitly use TCP for testing.

[kuritka]

@k0da , @jkremser , @ytsarev , @abaguas -
Hi, in this PR, I wanted to ask whether we still want to maintain the TCP protocol in the testing environment. From my perspective – the strict security restrictions limit me a lot, so I no longer use Colima and develop k8gb on my personal computer with Docker Desktop. For me, TCP is just another layer of complexity. What’s your opinion on this?

[ytsarev]

Should we hide tcp behind the configuration flag and switch to udp by default?

[abaguas]

I develop using Docker Desktop, so I am also fine switching to udp by default