tree 3c4b20c3bd746f5991f49ee01df8dd2d88dbe254
parent c17c31c822dc4a5f3270f6ae4f96afa50fb7390f
author Christopher Faulet <cfaulet@haproxy.com> 1645452774 +0100
committer Christopher Faulet <cfaulet@haproxy.com> 1645455947 +0100

BUG/MAJOR: mux-h2: Be sure to always report HTX parsing error to the app layer

If a parsing error is detected and the corresponding HTX flag is set
(HTX_FL_PARSING_ERROR), we must be sure to always report it to the app
layer. It is especially important when the error occurs during the response
parsing, on the server side. In this case, the RX buffer contains an empty
HTX message to carry the flag. And it remains in this state till the info is
reported to the app layer. This must be done otherwise, on the conn-stream,
the CS_FL_ERR_PENDING flag cannot be switched to CS_FL_ERROR and the
CS_FL_WANT_ROOM flag is always set when h2_rcv_buf() is called. The result
is a ping-pong loop between the mux and the stream.

Note that this patch fixes a bug. But it also reveals a design issue. The
error must not be reported at the HTX level. The error is already carried by
the conn-stream. There is no reason to duplicate it. In addition, it is
errorprone to have an empty HTX message only to report the error to the app
layer.

This patch should fix the issue #1561. It must be backported as far as 2.0
but the bug only affects HAProxy >= 2.4.