commit a8fcdacb8cc0dddec72b1ddc4d9afc92d3684acd
Author: Willy Tarreau <w@1wt.eu>
Date:   Fri Aug 2 07:48:47 2019 +0200

    BUG/MEDIUM: mux-h2: unbreak receipt of large DATA frames
    
    Recent optimization in commit 4d7a88482 ("MEDIUM: mux-h2: don't try to
    read more than needed") broke the receipt of large DATA frames because
    it would unconditionally subscribe if there was some room left, thus
    preventing any new rx from being done since subscription may only be
    done once the end was reached, as indicated by ret == 0.
    
    However, fixing this uncovered that in HTX mode previous versions might
    occasionally be affected as well, when an available frame is the same
    size as the maximum data that may fit into an HTX buffer, we may end
    up reading that whole frame and still subscribe since it's still allowed
    to receive, thus causing issues to read the next frame.
    
    This patch will only work for 2.1-dev but a minor adaptation will be
    needed for earlier versions (down to 1.9, where subscribe() was added).
    
    (cherry picked from commit 9bc1c95855b9c6300de5ecf3720cbe4b2558c5a1)
    Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/src/mux_h2.c b/src/mux_h2.c
index 5bb85181..d605fe94 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -2766,7 +2766,7 @@ static int h2_recv(struct h2c *h2c)
 			ret = 0;
 	} while (ret > 0);
 
-	if (h2_recv_allowed(h2c) && (b_data(buf) < buf->size))
+	if (max && !ret && h2_recv_allowed(h2c))
 		conn->xprt->subscribe(conn, conn->xprt_ctx, SUB_RETRY_RECV, &h2c->wait_event);
 
 	if (!b_data(buf)) {