RFR: 8263031: HttpClient throws Exception if it receives a Push Promise that is too large [v5]

[Daniel Fuchs]

On Tue, 22 Mar 2022 10:31:25 GMT, Conor Cleary <ccleary at openjdk.org> wrote:

>> **Problem**
>> When a Continuation Frame is received by the httpclient using HTTP/2 after a Push Promise frame (can happen if the amount of headers to be sent in a single Push Promise frame exceeds the maximum frame size, so a Continuation frame is required), the following exception occurs:
>> 
>> 
>> java.io.IOException: no statuscode in response
>> at java.net.http/jdk.internal.net.http.HttpClientImpl.send(HttpClientImpl.java:565)
>> at java.net.http/jdk.internal.net.http.HttpClientFacade.send(HttpClientFacade.java:119)
>> ...
>> 
>> This exception occurs because there is no existing flow in `jdk/internal/net/http/Http2Connection.java` which accounts for the case where a PushPromiseFrame is received with the END_HEADERS flag set to 0x0. When this occurs, the only acceptable frame/s (as multiple continuations are also acceptable) that can be received by the client on the same stream is a continuation frame.
>> 
>> **Fix**
>> To ensure correct behavior, the following changes were made to `jdk/internal/net/http/Http2Connection.java`.
>> 
>> - The existing method `handlePushPromise()` was modified so that if the END_HEADERS flag is _unset_ (flags equal to 0x0), then a record used to track the state of the Push Promise containing a shared `HeaderDecoder` and the received `PushPromiseFrame` is initialised.
>> - When the subsequent `ContinuationFrame` is received in `processFrame()`, the method `handlePushContinuation()` is called instead of the default flow resulting in `stream.incoming(frame)` being called (the source of the incorrect behaviour originally).
>> - In `handlePushContinuation()`, the shared decoder is used to decode the received `ContinuationFrame` headers and if the `END_HEADERS` flag is set (flags equal to 0x4), the `HttpHeaders` object for the Push Promise as a whole is constructed which serves to combine the headers from both the `PushPromiseFrame` and the `ContinuationFrame`.
>> 
>> A regression test was included which verifies that the exception is not thrown and that the headers arrive correctly.
>
> Conor Cleary has updated the pull request incrementally with four additional commits since the last revision:
> 
>  - 8263031: Added return statements and pcs var
>  - 8263031: Test cleanup, added third case
>  - Revert "Test cleanup, added third case"
>    
>    This reverts commit 5c1c0f5fea801923bc3352bf88c701768d78b11d.
>  - Test cleanup, added third case

Thanks for making these changes! Still a few comments...

src/java.net.http/share/classes/jdk/internal/net/http/Http2Connection.java line 28:

> 26: package jdk.internal.net.http;
> 27: 
> 28: import jdk.internal.net.http.HttpConnection.HttpPublisher;

Could this line be pushed down to where other `jdk.*` imports are made?

test/jdk/java/net/httpclient/http2/PushPromiseContinuation.java line 158:

> 156:         CompletableFuture<HttpResponse<String>> cf =
> 157:                 client.sendAsync(hreq, HttpResponse.BodyHandlers.ofString(UTF_8), pph);
> 158:         cf.join();

I'd suggest checking that we received the expected response code + body too

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PR: https://git.openjdk.java.net/jdk/pull/7696