reject legacy hex IPv4 literals in connector host resolution

[arshsmith1]

What do these changes do?

TCPConnector._resolve_host already rejects legacy numeric IPv4 aliases (2130706433, 017700000001, 127.1) so they cannot be resolved past a connector-level host policy that only inspects the raw host string. That rejection is gated on is_ip_address(host), whose heuristic is ":" in host or host.replace(".", "").isdigit(), so it only recognises the decimal-dotted forms. Hexadecimal literals like 0x7f000001 and 0x7f.0.0.1 are not seen as IPs at all, so they skip the is_canonical_ipv4_address guard and go straight to the resolver, where getaddrinfo/inet_aton maps them onto 127.0.0.1.

This adds a small is_ipv4_literal helper (backed by socket.inet_aton, so it recognises every form the resolver accepts) and widens the connector guard to use it, closing the hex gap while leaving canonical addresses and real hostnames untouched.

Are there changes in behavior for the user?

Only for the bypass case. Canonical dotted-quad IPs still short-circuit the resolver as before, and real hostnames still resolve normally. A hex/legacy numeric literal that is not canonical now raises InvalidUrlClientError, matching what already happens for the decimal and octal forms.

Is it a substantial burden for the maintainers to support this?

No. It reuses the existing guard and helper next to is_canonical_ipv4_address, and the regression sits in the test that already covers the decimal/octal/short aliases.

Related issue number

None.

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes -- N/A, the helper is internal and there is no public API change
• If you provide code modification, please add yourself to CONTRIBUTORS.txt -- already listed
• Add a new news fragment into the CHANGES/ folder

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.42%. Comparing base (7dc43ae) to head (d86d782).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #13436   +/-   ##
=======================================
  Coverage   98.42%   98.42%           
=======================================
  Files         133      133           
  Lines       49747    49760   +13     
  Branches     2628     2628           
=======================================
+ Hits        48961    48974   +13     
  Misses        662      662           
  Partials      124      124           

Flag	Coverage Δ
Autobahn	21.97% <66.66%> (+0.01%)	⬆️
CI-GHA	98.32% <100.00%> (+<0.01%)	⬆️
OS-Linux	98.09% <100.00%> (-0.01%)	⬇️
OS-Windows	96.45% <100.00%> (+<0.01%)	⬆️
OS-macOS	97.34% <100.00%> (+<0.01%)	⬆️
Py-3.10	97.54% <100.00%> (+<0.01%)	⬆️
Py-3.11	97.79% <100.00%> (-0.01%)	⬇️
Py-3.12	97.88% <100.00%> (-0.01%)	⬇️
Py-3.13	97.87% <100.00%> (+<0.01%)	⬆️
Py-3.14	97.89% <100.00%> (+<0.01%)	⬆️
Py-3.14t	96.98% <100.00%> (-0.01%)	⬇️
Py-pypy-3.11	96.84% <100.00%> (-0.02%)	⬇️
VM-macos	97.34% <100.00%> (+<0.01%)	⬆️
VM-ubuntu	98.09% <100.00%> (-0.01%)	⬇️
VM-windows	96.45% <100.00%> (+<0.01%)	⬆️
cython-coverage	82.19% <87.50%> (+<0.01%)	⬆️

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[codspeed-hq]

Merging this PR will not alter performance

✅ 84 untouched benchmarks
⏩ 83 skipped benchmarks¹

---

_{Comparing arshsmith1:connector-reject-hex-ipv4 (d86d782) with master (7dc43ae)}

Footnotes

1. 83 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩