Import CI ipv6-noproxy-cidr test from RHEL

This is from RHEL distgit tests/python-requests, directory
Sanity/ipv6-noproxy-cidr.
The commit hash this was copied from: 050c2979f27cc70506ddf669f9e0803a7b67c2d5

Only the necessary files were kept.

tests/ipv6-noproxy-cidr/main.fmf

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+require:
+- nmap-ncat
+- python3
+- python3-requests
+
+test: "${PYTHON:-python3} repro.py"
+tty: "true"

tests/ipv6-noproxy-cidr/repro.py

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+import subprocess
+import requests
+import os
+import time
+import atexit
+
+subprocesses = []
+
+python = os.environ.get("PYTHON","python3")
+server_url = os.environ.get("SERVER_URL", None)
+testing_no_proxy = os.environ.get("TESTING_NO_PROXY", None)
+
+# Clean up
+@atexit.register
+def cleanup():
+    print("Cleaning up subprocesses")
+    for process in subprocesses:
+        process.terminate()
+
+    time.sleep(1)
+
+    for process in subprocesses:
+        process.wait()
+
+# Part one, assert that everything works
+if server_url is None:
+    print("starting server")
+    p = subprocess.Popen([python, "server.py"], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    subprocesses.append(p)
+    time.sleep(1)
+    server_url = "http://[::1]:8888"
+    no_proxy = "::1/128"
+else:
+    print(f"using provided {server_url} as server")
+    print(f"using provided {testing_no_proxy} as NO_PROXY value")
+    assert testing_no_proxy, "TESTING_NO_PROXY envar missing"
+
+# Send request and check the response
+
+print("sending first request")
+assert requests.get(server_url, timeout=2).text.startswith("Hello")
+
+
+# Part two, dummy proxy causes timeout, that's fine
+
+# Start proxy
+print("starting proxy")
+p = subprocess.Popen(["nc", "-k", "-l", "10000"], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+subprocesses.append(p)
+time.sleep(1)
+
+# Set proxy to environment
+os.environ["HTTP_PROXY"] = "http://127.0.0.1:10000"
+
+# Send request, expect timeout because proxy is dummy and do not respond
+print("Sending request via proxy")
+try:
+    requests.get(server_url, timeout=2)
+except requests.exceptions.ReadTimeout:
+    print("timeout is fine, expected")
+    pass
+
+# Part three, NO_PROXY bypass the proxy and the request should work as before
+
+os.environ["NO_PROXY"] = testing_no_proxy or no_proxy
+
+print("sending last request")
+try:
+    assert requests.get(server_url, timeout=2).text.startswith("Hello")
+except requests.exceptions.ReadTimeout:
+    print("PROBLEM - the last request timed out, NO_PROXY setting does not work!")
+    raise SystemExit(1)
+else:
+    print("OK - NO_PROXY setting works fine - the last request bypassed proxy")

tests/ipv6-noproxy-cidr/server.py

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+from http.server import SimpleHTTPRequestHandler, HTTPServer
+import socket
+import sys
+class IPv6OnlyHandler(SimpleHTTPRequestHandler):
+    def do_GET(self):
+        client_address = self.client_address[0]
+        # Check if the client address is an IPv6 address
+        if ":" in client_address:
+            self.send_response(200)
+            self.send_header('Content-type', 'text/plain')
+            self.end_headers()
+            self.wfile.write(b'Hello')
+        else:
+            # Raise a RuntimeError if the client address is an IPv4 address
+            raise SystemExit(f"IPv4 address ({client_address}) detected. Only IPv6 addresses are allowed.")
+
+class HTTPServerV6(HTTPServer):
+  address_family = socket.AF_INET6
+
+if __name__ == '__main__':
+    # Use IPv6 address and port 8080
+    server_address = ('::', 8888)
+    httpd = HTTPServerV6(server_address, IPv6OnlyHandler)
+    print('Server running on port 8888...')
+    httpd.serve_forever()