Motivation:
Today, the HTTP codec in Netty responds to HTTP/1.1 requests containing
an "expect: 100-continue" header and a content-length that exceeds the
max content length for the server with a 417 status (Expectation
Failed). This is a violation of the HTTP specification. The purpose of
this commit is to address this situation by modifying the HTTP codec to
respond in this situation with a 413 status (Request Entity Too
Large). Additionally, the HTTP codec ignores expectations in the expect
header that are currently unsupported. This commit also addresses this
situation by responding with a 417 status.
Handling the expect header is tricky business as the specification (RFC
2616) is more complicated than it needs to be. The specification defines
the legitimate values for this header as "100-continue" and defines the
notion of expectatation extensions. Further, the specification defines a
417 status (Expectation Failed) and this is where implementations go
astray. The intent of the specification was for servers to respond with
417 status when they do not support the expectation in the expect
header.
The key sentence from the specification follows:
The server MUST respond with a 417 (Expectation Failed) status if
any of the expectations cannot be met or, if there are other
problems with the request, some other 4xx status.
That is, a server should respond with a 417 status if and only if there
is an expectation that the server does not support (whether it be
100-continue, or another expectation extension), and should respond with
another 4xx status code if the expectation is supported but there is
something else wrong with the request.
Modifications:
This commit modifies the HTTP codec by changing the handling for the
expect header in the HTTP object aggregator. In particular, the codec
will now respond with 417 status if any expectation other than
100-continue is present in the expect header, the codec will respond
with 413 status if the 100-continue expectation is present in the expect
header and the content-length is larger than the max content length for
the aggregator, and otherwise the codec will respond with 100 status.
Result:
The HTTP codec can now be used to correctly reply to clients that send a
100-continue expectation with a content-length that is too large for the
server with a 413 status, and servers that use the HTTP codec will now
no longer ignore expectations that are not supported (any value other
than 100-continue).
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