BUG/MEDIUM: checks: make sure the connection is ready before trying to recv

As identified in issue #278, the backport of commit c594039225 ("BUG/MINOR:
checks: do not uselessly poll for reads before the connection is up")
introduced a regression in 2.0 when default checks are enabled (not
"option tcp-check"), but it did not affect 2.1.

What happens is that in 2.0 and earlier we have the fd cache which makes
a speculative call to the I/O functions after an attempt to connect, and
the __event_srv_chk_r() function was absolutely not designed to be called
while a connection attempt is still pending. Thus what happens is that the
test for success/failure expects the verdict to be final before waking up
the check task, and since the connection is not yet validated, it fails.
It will usually work over the loopback depending on scheduling, which is
why it doesn't fail in reg tests.

In 2.1 after the failed connect(), we subscribe to polling and usually come
back with a validated connection, so the function is not expected to be
called before it completes, except if it happens as a side effect of some
spurious wake calls, which should not have any effect on such a check.

The other check types are not impacted by this issue because they all
check for a minimum data length in the buffer, and wait for more data
until they are satisfied.

This patch fixes the issue by explicitly checking that the connection
is established before trying to read or to give a verdict. This way the
function becomes safe to call regardless of the connection status (even
if it's still totally ugly).

This fix must be backported to 2.0.

diff --git a/src/checks.c b/src/checks.c
index 6bde412919e831c1d4770b76604208cd941a9c9c..247caf12e2a34a98b0754b6777aba50d2cce9f55 100644 (file)
--- a/src/checks.c
+++ b/src/checks.c
@@ -875,6 +875,9 @@ static void __event_srv_chk_r(struct conn_stream *cs)
                }
        }
 
+       /* the rest of the code below expects the connection to be ready! */
+       if (!(conn->flags & CO_FL_CONNECTED) && !done)
+               goto wait_more_data;
 
        /* Intermediate or complete response received.
         * Terminate string in b_head(&check->bi) buffer.