Hello Martin!
You are having a strange and unexpected experience with the CDN, I only see this happening if your network is redirecting traffic to GitHub endpoints.
Here are some techie stuff that might help you and your network team diagnose the issue if it persists on your end.
Currently if you make an HTTP request (non HTTPS), it will respond with a permanent redirect to HTTPS endpoint, so your result very strange for us.
I have just checked and I am getting the expected values:
- HTTP - 301 redirect, invalid resource address
$ curl -i http://speed.ext.net/ext.net/3.3.0
HTTP/1.1 301 Moved Permanently
- HTTPS - 404 not found, invalid resource address
$ curl -i https://speed.ext.net/ext.net/3.3.0/
HTTP/2 404
- HTTP - 301 redirect, valid resource address
$ curl -I http://speed.ext.net/ext.net/3.3.0/extnet/extnet-all.js
HTTP/1.1 301 Moved Permanently
- HTTS - 200 found, valid resource address
$ curl -I https://speed.ext.net/ext.net/3.3.0/extnet/extnet-all.js
HTTP/2 200
Check again, if you still get this error, check from other networks and check with your network if you are having any redirects to GitHub resources.
Currently, speed.ext.net should be resolving, DNS-wise, to the following IP addresses:
;; ANSWER SECTION:
speed.ext.net. 98 IN CNAME extnet.github.io.
extnet.github.io. 3010 IN A 185.199.110.153
extnet.github.io. 3010 IN A 185.199.111.153
extnet.github.io. 3010 IN A 185.199.108.153
extnet.github.io. 3010 IN A 185.199.109.153
Queries to one of those IP addresses should show the following headers; different headers suggest tampering with your connection:
$ curl -I http://185.199.110.153/
HTTP/1.1 404 Not Found
Server: GitHub.com
Content-Type: text/html; charset=utf-8
x-origin-cache: HIT
ETag: "5f77c9f3-239b"
Content-Security-Policy: default-src 'none'; style-src 'unsafe-inline'; img-src data:; connect-src 'self'
X-GitHub-Request-Id: BD62:29B2:A886C:3AECE1:60706D5E
Content-Length: 9115
Accept-Ranges: bytes
Date: Fri, 09 Apr 2021 15:06:06 GMT
Via: 1.1 varnish
Age: 0
Connection: keep-alive
X-Served-By: cache-gig17035-GIG
X-Cache: MISS
X-Cache-Hits: 0
X-Timer: S1617980766.200696,VS0,VE116
Vary: Accept-Encoding
X-Fastly-Request-ID: eadf4d4a1c52f881c0f800feb9ef190b3348e5ea
While the output above is correct for current state, this may change without notice in the future, so you should use these headers as base within the next few days but there's no guarantee the HTTP headers will look the same, say, in year 2022 or later.
Hope this helps!