如何要求客户端将HTTP2连接降级为HTTP1.1

Question

这主要是出于好奇；说我有一个HTTP1.1兼容服务器。我没有资源，无法向该服务器添加完整的HTTP2支持。

仍然我希望通过告诉他们使用HTTP1.1来提供clients which open a connection with a HTTP2 connection preface（PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n）。请注意，这是关于do n't >>通过带有Upgrade标头的HTTP1.1请求启动连接的客户端。

这是我想要实现的行为：

CLIENT                 SERVER
  | ------ http2 GET --> |
  | <----need http1 ---- |
  | ------ http1 GET --> |
  ... (normal http1 processing)
该规范包含错误代码HTTP_1_1_REQUIRED (0xd)，这听起来与我所需要的差不多。而且，从阅读的情况来看，该错误代码似乎在必要时用于降级连接（显然是TLS重新协商？）。但是我似乎似乎无法使它正常工作...

char const Http2EmptySettingsFrame[] =
  {
   // Frame Header
   0, 0, 0,
   0x4,
   0,
   0 & 0x7F, 0, 0, 0
  };

char const Http2RstStreamFrame[] =
  {
   // Frame Header
   0, 0, 4, // Length of frame content
   0x3, // Type: RST_STREAM
   0, // Flags
   0 & 0x7F, 0, 0, 1, // Stream identifier 1 ; also tried with 0

   // Frame content
   0, 0, 0, 0xD // Error code (RST_STREAM frame)
  };

char const Http2GoAwayFrame[] =
  {
   // Frame Header
   0, 0, 8,
   0x7,
   0,
   0 & 0x7F, 0, 0, 0,

   0 & 0x7F, 0, 0, 0, // GO_AWAY stream id
   0, 0, 0, 0xD // GO_AWAY error code: HTTP_1_1_REQUIRED
  };

使用上面的代码和fwrite(frame, sizeof(frame), 1, stdout)在一个小的测试程序中，我创建了要发送到客户端的帧[（C0]）。然后，我启动我的“服务器”：

./a.out > frame.bin
使用http2客户端，然后得到...

cat emptysettings.bin rststream.bin goaway.bin - | netcat -l -p 8888 -s 127.0.0.1
...或使用curl ...

# this was when just sending empty SETTINGS and RST_STREAM frame
nghttp -v http://127.0.0.1:8888
[  0.000] Connected
[  0.000] recv SETTINGS frame <length=0, flags=0x00, stream_id=0>
          (niv=0)
[  0.000] [INVALID; error=Protocol error] recv RST_STREAM frame <length=4, flags=0x00, stream_id=1>
          (error_code=HTTP_1_1_REQUIRED(0x0d))
[  0.000] send SETTINGS frame <length=12, flags=0x00, stream_id=0>
          (niv=2)
          [SETTINGS_MAX_CONCURRENT_STREAMS(0x03):100]
          [SETTINGS_INITIAL_WINDOW_SIZE(0x04):65535]
[  0.000] send GOAWAY frame <length=34, flags=0x00, stream_id=0>
          (last_stream_id=0, error_code=PROTOCOL_ERROR(0x01), opaque_data(26)=[RST_STREAM: stream in idle])
[ERROR] request http://127.0.0.1:8888 failed: request HEADERS is not allowed
Some requests were not processed. total=1, processed=0
...因此：我需要向客户端发起一个HTTP2连接以将其降级到HTTP1.1的方式发送给客户端什么响应？

发送

curl -v --http2-prior-knowledge http://127.0.0.1:8888
*   Trying 127.0.0.1:8888...
* TCP_NODELAY set
* Connected to 127.0.0.1 (127.0.0.1) port 8888 (#0)
* Using HTTP2, server supports multi-use
* Connection state changed (HTTP/2 confirmed)
* Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
* Using Stream ID: 1 (easy handle 0x16887f0)
> GET / HTTP/2
> Host: 127.0.0.1:8888
> User-Agent: curl/7.66.0
> Accept: */*
> 
* Connection state changed (MAX_CONCURRENT_STREAMS == 4294967295)!
* stopped the pause stream!
* Connection #0 to host 127.0.0.1 left intact
curl: (16) Error in the HTTP2 framing layer

（505 = HTTP/1.1 505 hmmm\n\n）也无济于事...

这主要是出于好奇；说我有一个HTTP1.1兼容服务器。我没有资源/无法向该服务器添加完整的HTTP2支持。我还是想服务...

Answer 1

我需要向客户端发起http2连接以将其降级到HTTP1.1的发送给客户端什么响应？