fix: avoid hanging on 101 switching protocol responses

[arpitjain099]

This fixes a hang when a target returns 101 Switching Protocols and keeps the upgraded connection open.\n\nThe request path still installed a body-drain defer when MaxResponseBodySizeToRead was set. For upgrade responses, that defer could block forever on io.Copy(io.Discard, body) even though we intentionally skip body reads for websocket-style responses.\n\nI now skip that drain defer for the same status codes where body reads are skipped (101, 304), and reuse that guard for the read branch too.\n\nI also added a regression test that stubs a 101 response with a body reader that never returns, and asserts Do returns instead of hanging.\n\nFixes #2517\n\n### Verification\n- go test ./common/httpx -run "TestDoSwitchingProtocolsDoesNotHang|TestSetCustomHeaders|TestParseCustomCookies|TestHTTP11DisablesRetryableHTTP2FallbackClient|TestDefaultProtocolKeepsRetryableHTTP2FallbackClient" -count=1\n- go build ./cmd/httpx\n- go run ./cmd/httpx -u "http://cediplast.myqnapcloud.com:8085" -stats -v -timeout 5 -nc

Summary by CodeRabbit

• Bug Fixes
  • Fixed a potential hanging issue when handling HTTP 101 Switching Protocols responses.
  • Optimized response body handling for specific HTTP status codes to improve reliability.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 6ec00995-a786-4665-b764-4f3f22bfd678

📥 Commits

Reviewing files that changed from the base of the PR and between c59ccc5 and 5e0cb4e.

📒 Files selected for processing (2)

• common/httpx/httpx.go
• common/httpx/httpx_test.go

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Walkthrough

HTTPX.Do is refactored to compute a single shouldSkipBodyRead flag for HTTP status codes 101 and 304, then gates both the deferred body drain/discard+close and the io.ReadAll call on that flag. A new test injects a round tripper returning a 101 response with a permanently blocking body and asserts Do completes within 4 seconds.

Changes

Fix hang on 101 Switching Protocols / 304 Not Modified

Layer / File(s)	Summary
shouldSkipBodyRead flag and body drain gate common/httpx/httpx.go	Computes shouldSkipBodyRead for status codes 101 and 304 once; uses it to skip the deferred drain+close and the io.ReadAll call, replacing the previous duplicated inline status-code checks.
Regression test for 101 hang common/httpx/httpx_test.go	Adds TestDoSwitchingProtocolsDoesNotHang with a switchingProtocolsRoundTripper that returns a 101 response backed by a permanently blocking reader; asserts ht.Do returns within 4 seconds.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐇 A websocket knock, the server said "101!"
httpx once froze — now that nightmare is done.
A flag called shouldSkip says "read not required,"
No draining, no hanging, no goroutines mired.
The rabbit hops free, four seconds or less! 🎉

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main fix: avoiding hangs when processing 101 Switching Protocol responses, which is the core issue addressed in the changeset.
Linked Issues check	✅ Passed	The PR successfully addresses issue #2517 by fixing the hang that occurs with 101 Switching Protocols responses through refactored body-handling logic and added regression testing.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing the 101 Switching Protocols hang issue: refactored httpx.Do body handling, added test with blocking body reader, and imported time package for timeout assertions.

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✨ Finishing Touches

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