MEDIUM: connection: make mux->detach() release the connection

For H2, only the mux's timeout or other conditions might cause a
release of the mux and the connection, no stream should be allowed
to kill such a shared connection. So a stream will only detach using
cs_destroy() which will call mux->detach() then free the cs.

For now it's only handled by mux_pt. The goal is that the data layer
never has to care about the connection, which will have to be released
depending on the mux's mood.

include/proto/connection.h

@@ -694,12 +694,7 @@ static inline void conn_free(struct connection *conn)
 /* Release a conn_stream, and kill the connection if it was the last one */
 static inline void cs_destroy(struct conn_stream *cs)
 {
-	struct connection *conn = cs->conn;
+	cs->conn->mux->detach(cs);
-
-	LIST_DEL(&conn->list);
-	conn_stop_tracking(conn);
-	conn_full_close(conn);
-	conn_free(conn);
 	cs_free(cs);
 }
 

src/mux_pt.c

@@ -113,11 +113,16 @@ static struct conn_stream *mux_pt_attach(struct connection *conn)
 }
 
 /*
- * Detach the stream from the connection
+ * Detach the stream from the connection and possibly release the connection.
- * (Used for outgoing connections)
  */
 static void mux_pt_detach(struct conn_stream *cs)
 {
+	struct connection *conn = cs->conn;
+
+	LIST_DEL(&conn->list);
+	conn_stop_tracking(conn);
+	conn_full_close(conn);
+	conn_free(conn);
 }
 
 static void mux_pt_shutr(struct conn_stream *cs, enum cs_shr_mode mode)