changes: modify ngx.read_body api limitation in HTTP/2 and HTTP/3#2237
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zhuizhuhaomeng merged 1 commit intoNov 5, 2023
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| if (r->http_version == NGX_HTTP_VERSION_30 | ||
| && r->headers_in.content_length_n < 0) | ||
| { | ||
| ngx_log_error(NGX_LOG_WARN, r->connection->log, 0, |
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Yes, HTTP/3 has same problem.
oowl
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Oct 17, 2023
| **phase:** *depends on usage* | ||
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| Due to the stream processing feature of HTTP2, it does not support HTTP2 connection. | ||
| Due to the stream processing feature of HTTP/2 or HTTP/3, this configuration could potentially block the entire request. Therefore, this configuration is effective only when HTTP/2 or HTTP/3 requests send content-length header. For requests with versions lower than HTTP/2, this configuration can still be used without any problems. |
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We have discussed this problem and reached an agreement that enables read_body API in the HTTP2 request contain the content-length header
And why chunk-transfer not enabled? from RFC
In https://greenbytes.de/tech/webdav/rfc7540.html#rfc.section.8.1.p.4:
HTTP/2 uses DATA frames to carry message payloads. The chunked transfer encoding defined in Section 4.1 of [RFC7230] MUST NOT be used in HTTP/2.
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@zhuizhuhaomeng Hi, Can you help us take a look at this PR?
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…ength header This check ensures that the underlying lua-nginx-module will not crash when trying to fetch the body of a POST request made with HTTP2 or HTTP3 with an unspecified Content-Length header. See openresty/lua-nginx-module#2237
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This check ensures that the underlying lua-nginx-module will not crash when trying to fetch the body of a POST request made with HTTP2 or HTTP3 with an unspecified Content-Length header. See openresty/lua-nginx-module#2237
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I hereby granted the copyright of the changes in this pull request
to the authors of this lua-nginx-module project.
#2174 mentioned an issue where there is a chance of blocking the ngx.read_body API when using HTTP/2. As a result, #2174 disabled the ngx.read_body API in HTTP/2. However, #2211 also suggested that perhaps we should not completely disable the ngx.read_body API in HTTP/2, as many HTTP/2 requests could still benefit from this.
To address this, I attempted to define the minimum limitations for using ngx.read_body in HTTP/2. From what I understand, ngx.read_body is based on the Nginx core to handle the client's body, and the Nginx core typically reads the entire client body before calling the callback registered by the lua-nginx-module. There are two scenarios in which HTTP/2 can trigger this callback. First, when the Content-Length header is used, Nginx core can determine the exact number of bytes to read from the client side. The second scenario is when an HTTP/2 request sends the entire body and immediately closes the HTTP/2 stream. Additionally, HTTP/2 does not support the chunked transfer encoding.
The first scenario is relatively straightforward to detect in the lua-nginx-module. However, the second scenario is challenging to identify because Nginx core takes over the remaining part, and the lua-nginx-module can only wait to be called by the Nginx core. Therefore, in this pull request, I propose to only allow HTTP/2 requests that carry the Content-Length header. So in the second scenario, If someone want to use ngx.read_body, need to add the Content-Length header.
I also considered adding a timeout option for the read_body API. However, I decided against it for two reasons:
Nginx already has a timeout option for reading the client's body, which is configured using client_body_timeout. This configuration terminates the HTTP request when a timeout occurs. Introducing another timeout option, which would keep the rest of the Lua thread logic running, seemed redundant.
Secondly, I believe that scenarios causing the blocking of the ngx.read_body API should not use ngx.read_body. Adding a timeout option may not immediately expose the real problem.
It's worth noting that HTTP/3 faces a similar problem, and this pr implemented the same solution for it.