#1432 HTTP/2 --next flag extra connections and duplicate requests

[Scott Mitchell]

The --next flag for HTTP/2 is openeing an extra connection and duplicates requests on the second connection.

The scenario is described here: http://curl.haxx.se/mail/archive-2014-10/0008.html.

[Daniel Stenberg]

Sorry, but that is a seriously wrong conclusion of what you see. It has nothing to do with --next. It relates to the connection being re-used and curl wrongly thinking it is dead. But we don't know why the connection breaks, figuring that out could lead to us understanding what's going on.

[Scott Mitchell]

Feel free to re-categorize or re-file if you are unhappy with the description. If you do decide to re-file lets just make sure the issue described here is also addressed.

Do you need additional information from me? The issue is reliably reproducable in the scenario I described on the mailing list.

[Scott Mitchell]

I had posted this to the mailing list but it may be more appropraite to put it directly in the issue:

I found where the PROTOCOL_EXCEPTION exception is being generated in the curl code. The following if statement is evaluating to true and is resulting in a protocol error being sent
https://github.com/bagder/curl/blob/7d9bef9286cd8efbed032d41a36e82d1c44058a7/lib/http2.c#L484? Each response has a ":status" header and also some other headers (content-type, custom "x-" extension headers, etc...) this check is evaluating to true because c->status_code == -1 is true.

status_code is reset to -1 here https://github.com/bagder/curl/blob/7d9bef9286cd8efbed032d41a36e82d1c44058a7/lib/http2.c#L984 and here https://github.com/bagder/curl/blob/7d9bef9286cd8efbed032d41a36e82d1c44058a7/lib/http2.c#L251. The issue is both of these lines are hit in between receiving the ":status" header and the next headers for a given stream. I am not sure what the fix would be because I am a bit confused about the granularity of the http_conn object within the connectdata structure. It seems like there should be a collection of these (1 per stream) and not just one for the whole connection?

Additional information

The Curl_http2_setup(...) method is being called here https://github.com/bagder/curl/blob/7d9bef9286cd8efbed032d41a36e82d1c44058a7/lib/http.c#L1765 in between processing streams on a given connection.

[Daniel Stenberg]

Since this particular case was due to a server malfunction I'm closing this issue. There may still be other problems lurking but they're not easy to trigger or debug. Hopefully a future http2 test suite should help us with this.