BUG/MEDIUM: mux-fcgi: Try to fully fill demux buffer on receive if not empty

Don't reserve space for the HTX overhead on receive if the demux buffer is
not empty. Otherwise, the demux buffer may be erroneously reported as full
and this may block records processing. Because of this bug, a ping-pong loop
till timeout between data reception and demux process can be observed.

This bug was introduced by the commit 5f927f603 ("BUG/MEDIUM: mux-fcgi:
Properly handle read0 on partial records"). To fix the issue, if the demux
buffer is not empty when we try to receive more data, all free space in the
buffer can now be used. However, if the demux buffer is empty, we still try
to keep it aligned with the HTX.

This patch must be backported to 3.1.

diff --git a/src/mux_fcgi.c b/src/mux_fcgi.c
index 289c85c238ed77de699c7f91ae4a8c719e3de8ab..fe46e184e1f5ee5144ce1d3564fdf42dab8b9621 100644 (file)
--- a/src/mux_fcgi.c
+++ b/src/mux_fcgi.c
@@ -2842,7 +2842,7 @@ static int fcgi_recv(struct fcgi_conn *fconn)
                buf->head = sizeof(struct htx) - (fconn->state == FCGI_CS_RECORD_H ? FCGI_RECORD_HEADER_SZ : 0);
        }
        else
-               max = buf_room_for_htx_data(buf);
+               max = b_room(buf);
 
        ret = max ? conn->xprt->rcv_buf(conn, conn->xprt_ctx, buf, max, 0) : 0;