IPv6 support for SteamCMD update server

[mganter]

Your system information

• Distribution (e.g. Ubuntu): Ubuntu 24.04.1 LTS (GNU/Linux 6.8.0-45-generic x86_64)

Please describe your issue in as much detail as possible:

SteamCMD cannot start on IPv6 only Server, as there is probably no AAAA DNS-Record on the domain for the update server. (In Wiki in the manual install there is the server steamcdn-a.akamaihd.net referenced which has no AAAA Record)

I installed SteamCMD with apt and executed it.

$ steamcmd
Redirecting stderr to '/root/.local/share/Steam/logs/stderr.txt'
ILocalize::AddFile() failed to load file "public/steambootstrapper_english.txt".
[  0%] Checking for available update...
[----] Verifying installation...
[  0%] Downloading Update...
[  0%] Checking for available update...
[----] !!! Fatal Error: Steamcmd needs to be online to update.   Please confirm your network connection and try again.
threadtools.cpp (3294) : Assertion Failed: Illegal termination of worker thread 'Thread(0x0x5f9773f0/0x0xf6a45b'

DNS Lookup results in some CNAME records (which dont have AAAA either)

$ dig steamcdn-a.akamaihd.net AAAA

; <<>> DiG 9.18.28-0ubuntu0.24.04.1-Ubuntu <<>> steamcdn-a.akamaihd.net AAAA
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 54530
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 1, ADDITIONAL: 3

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;steamcdn-a.akamaihd.net.       IN      AAAA

;; ANSWER SECTION:
steamcdn-a.akamaihd.net. 33     IN      CNAME   steamcdn-a.akamaihd.net.edgesuite.net.
steamcdn-a.akamaihd.net.edgesuite.net. 33 IN CNAME a1843.g1.akamai.net.

;; AUTHORITY SECTION:
g1.akamai.net.          948     IN      SOA     n0g1.akamai.net. hostmaster.akamai.com. 1730651630 1000 1000 1000 1800

;; ADDITIONAL SECTION:
a1843.g1.akamai.net.    33      IN      A       184.24.77.156
a1843.g1.akamai.net.    33      IN      A       184.24.77.162

;; Query time: 0 msec
;; SERVER: 127.0.0.53#53(127.0.0.53) (UDP)
;; WHEN: Sun Nov 03 16:34:42 UTC 2024
;; MSG SIZE  rcvd: 224

Steps for reproducing this issue:

1. Start Ubuntu 24.04.1 LTS
2. Execute: sudo apt update and sudo apt upgrade
3. Execute: sudo apt install steamcmd
4. Execute: steamcmd