BUG/MEDIUM: stream: Be sure to never assign a TCP backend to an HTX stream

With a TCP frontend, it is possible to upgrade a connection to HTTP when the
backend is in HTTP mode. Concretly the upgrade install a new mux. So, once it is
done, the downgrade to TCP is no longer possible. So we must take care to never
assign a TCP backend to a stream on this connection. Otherwise, HAProxy crashes
because raw data from the server are handled as structured data on the client
side.

This patch fixes the issue #420. It must be backported to all versions
supporting the HTX.

diff --git a/src/proxy.c b/src/proxy.c
index 838722d1e18dc20862b0e1abe4619eae2b678d8b..a5570dafa0718580df43b9af59c96a1f6f0e55fd 100644 (file)
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -1477,6 +1477,14 @@ int stream_set_backend(struct stream *s, struct proxy *be)
                                s->flags |= SF_HTX;
                        }
                }
+               else if (IS_HTX_STRM(s) && be->mode != PR_MODE_HTTP) {
+                       /* If a TCP backend is assgiend to an HTX stream, return
+                        * an error. It may happens for a new stream on a
+                        * previously upgraded connnections. */
+                       if (!(s->flags & SF_ERR_MASK))
+                               s->flags |= SF_ERR_INTERNAL;
+                       return 0;
+               }
 
                /* we may request to parse a request body */
                if (be->options & PR_O_WREQ_BODY)