tree 01bd522f7c201a34d6895c5eecefa9d58bd56373
parent 3777e3ad14f2ce54b6662fd0db56413dde9ec9fa
author Christopher Faulet <cfaulet@haproxy.com> 1575537817 +0100
committer Christopher Faulet <cfaulet@haproxy.com> 1575549076 +0100

BUG/MEDIUM: mux-h1: Never reuse H1 connection if a shutw is pending

On the server side, when a H1 stream is detached from the connection, if the
connection is not reusable but some outgoing data remain, the connection is not
immediatly released. In this case, the connection is not inserted in any idle
connection list. But it is still attached to the session. Because of that, it
can be erroneously reused. h1_avail_streams() always report a free slot if no
stream is attached to the connection, independently on the connection's
state. It is obviously a bug. If a second request is handled by the same session
(it happens with H2 connections on the client side), this connection is reused
before we close it.

There is small window to hit the bug, but it may lead to very strange
behaviors. For instance, if a first h2 request is quickly aborted by the client
while it is blocked in the mux on the server side (so before any response is
received), a second request can be processed and sent to the server. Because the
connection was not closed, the possible reply to the first request will be
interpreted as a reply to the second one. It is probably the bug described by
Peter Fröhlich in the issue #290.

To fix the bug, a new flag has been added to know if an H1 connection is idle or
not. So now, H1C_F_CS_IDLE is set when a connection is idle and useable to
handle a new request. If it is set, we try to add the connection in an idle
connection list. And h1_avail_streams() only relies on this flag
now. Concretely, this flag is set when a K/A stream is detached and both the
request and the response are in DONE state. It is exclusive to other H1C_F_CS
flags.

This patch must be backported as far as 1.9.