tree 3264827eed8d8fecb79de6bc0768cc4ae7293449
parent 216d3352b1aac1bff19383b6a6e5476e11e613e9
author Christopher Faulet <cfaulet@haproxy.com> 1632116847 +0200
committer Christopher Faulet <cfaulet@haproxy.com> 1632406397 +0200

BUG/MEDIUM: mux-h1: Adjust conditions to ask more space in the channel buffer

When a message is parsed and copied into the channel buffer, in
h1_process_demux(), more space is requested if some pending data remain
after the parsing while the channel buffer is not empty. To do so,
CS_FL_WANT_ROOM flag is set. It means the H1 parser needs more space in the
channel buffer to continue. In the stream-interface, when this flag is set,
the SI is considered as blocked on the RX path. It is only unblocked when
some data are sent.

However, it is not accurrate because the parsing may be stopped because
there is not enough data to continue. For instance in the middle of a chunk
size. In this case, some data may have been already copied but the parser is
blocked because it must receive more data to continue. If the calling SI is
blocked on RX at this stage when the stream is waiting for the payload
(because http-buffer-request is set for instance), the stream remains stuck
infinitely.

To fix the bug, we must request more space to the app layer only when it is
not possible to copied more data. Actually, this happens when data remain in
the input buffer while the H1 parser is in states MSG_DATA or MSG_TUNNEL, or
when we are unable to copy headers or trailers into a non-empty buffer.

The first condition is quite easy to handle. The second one requires an API
refactoring. h1_parse_msg_hdrs() and h1_parse_msg_tlrs() fnuctions have been
updated. Now it is possible to know when we need more space in the buffer to
copy headers or trailers (-2 is returned). In the H1 mux, a new H1S flag
(H1S_F_RX_CONGESTED) is used to track this state inside h1_process_demux().

This patch is part of a series related to the issue #1362. It should be
backported as far as 2.0, probably with some adaptations. So be careful
during backports.