Fix connection termination when using HTTP proxies

[Claude]

When using HTTP proxies (e.g., v2ray), rtp2httpd forwarded upstream response headers without ensuring Connection: close was present, causing proxies to keep connections alive indefinitely even after clients disconnected or switched channels.

Changes

• Modified HTTP proxy response header handling (src/http_proxy.c:1027-1172)

  • Filter out upstream Connection headers in both redirect and normal response paths
  • Always inject Connection: close header before sending headers to clients
  • Ensures proper connection termination regardless of upstream behavior

• Added e2e tests (e2e/test_http_proxy.py:500-592)

  • Verify Connection: close presence in normal responses
  • Verify Connection: close presence in redirect responses
  • Verify upstream keep-alive is correctly overridden with close

Technical Details

The fix modifies http_proxy_parse_response_headers() to parse and rebuild response headers, skipping any Connection header from upstream:

/* Filter out Connection header from upstream */
while (orig_line != NULL) {
  if (strncasecmp(orig_line, "Connection:", 11) != 0) {
    /* Copy other headers */
  }
  orig_line = strtok(NULL, "\r\n");
}

/* Always add Connection: close */
connection_queue_output(session->conn, (const uint8_t *)"Connection: close\r\n", 19);

This ensures HTTP proxies correctly terminate connections when clients disconnect, fixing the issue where switching channels or closing browsers left connections hanging.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>系统代理环境下连接终止异常</issue_title>
<issue_description>在启用系统代理时，在自带网页播放器中换台甚至是关闭浏览器都无法终止连接。经观察未发现异常日志。

测试环境：
系统架构：X86_64
操作系统：Win10 22H2
浏览器：Chrome 146.0.7680.80
代理软件：V2rayN 7.18.0
代理模式：自动配置系统代理
代理路由：黑名单

关注到串流流量是通过直连。清除系统代理后，故障现象消失。

本人能力有限，暂不清楚导致该现象的原因。</issue_description>

<agent_instructions>尝试分析和修复。rtp2httpd 本身不支持 http keep-alive，预期每个客户端连接都是 short-lived，只有当客户端断开连接后才会释放资源（rtp2httpd 会发送 Connection: close）。是否由于用户设置了 http proxy，但是 http proxy 本身没有正确处理 Connection: close？

可以结合 https://github.com/2dust/v2rayn 源码，分析它是否正确支持 Connection: close

如果可以修复，需要补充 e2e 测试来复现本 issue 提出的问题。</agent_instructions>

Comments on the Issue (you are @claude[agent] in this section)

• Fixes 系统代理环境下连接终止异常 #418