BUG/MINOR: mux-fcgi: Use relative offset to compute contig data in demux buf

b_contig_data() should be called with a head-relative offset (0 for the
beginning of readable data). However, in the FCGI multiplexer, to get
contiguous data available in the demux buffer, it is called with
b_head_ofs(dbuf) which returns an absolute buffer position (b->head). So
b->head is counted twice. Because of this bug, the demux buffer could be
realigned while it should not and conversely.

Instead, the offset 0 must be used. So let's fix it.

This patch must be backported as far as 2.4.

diff --git a/src/mux_fcgi.c b/src/mux_fcgi.c
index 7bd5d82de5be3d37c01265956de34219dc818fb2..88cbd18b17f661e09cd09d953e94f0b1ee912cf5 100644 (file)
--- a/src/mux_fcgi.c
+++ b/src/mux_fcgi.c
@@ -1595,7 +1595,7 @@ static int fcgi_conn_handle_values_result(struct fcgi_conn *fconn)
                return 0;
        }
 
-       if (unlikely(b_contig_data(dbuf, b_head_ofs(dbuf)) < fconn->drl)) {
+       if (unlikely(b_contig_data(dbuf, 0) < fconn->drl)) {
                /* Realign the dmux buffer if the record wraps. It is unexpected
                 * at this stage because it should be the first record received
                 * from the FCGI application.
@@ -2516,7 +2516,7 @@ static int fcgi_strm_handle_end_request(struct fcgi_conn *fconn, struct fcgi_str
                return 0;
        }
 
-       if (unlikely(b_contig_data(dbuf, b_head_ofs(dbuf)) < fconn->drl)) {
+       if (unlikely(b_contig_data(dbuf, 0) < fconn->drl)) {
                /* Realign the dmux buffer if the record wraps. It is unexpected
                 * at this stage because it should be the first record received
                 * from the FCGI application.