MEDIUM: connection: start to introduce a mux layer between xprt and data
For HTTP/2 and QUIC, we'll need to deal with multiplexed streams inside
a connection. After quite a long brainstorming, it appears that the
connection interface to the existing streams is appropriate just like
the connection interface to the lower layers. In fact we need to have
the mux layer in the middle of the connection, between the transport
and the data layer.
A mux can exist on two directions/sides. On the inbound direction, it
instanciates new streams from incoming connections, while on the outbound
direction it muxes streams into outgoing connections. The difference is
visible on the mux->init() call : in one case, an upper context is already
known (outgoing connection), and in the other case, the upper context is
not yet known (incoming connection) and will have to be allocated by the
mux. The session doesn't have to create the new streams anymore, as this
is performed by the mux itself.
This patch introduces this and creates a pass-through mux called
"mux_pt" which is used for all new connections and which only
calls the data layer's recv,send,wake() calls. One incoming stream
is immediately created when init() is called on the inbound direction.
There should not be any visible impact.
Note that the connection's mux is purposely not set until the session
is completed so that we don't accidently run with the wrong mux. This
must not cause any issue as the xprt_done_cb function is always called
prior to using mux's recv/send functions.
diff --git a/include/types/connection.h b/include/types/connection.h
index eee75ec..f720601 100644
--- a/include/types/connection.h
+++ b/include/types/connection.h
@@ -243,6 +243,22 @@
char name[8]; /* transport layer name, zero-terminated */
};
+/* mux_ops describes the mux operations, which are to be performed at the
+ * connection level after data are exchanged with the transport layer in order
+ * to propagate them to streams. The <init> function will automatically be
+ * called once the mux is instanciated by the connection's owner at the end
+ * of a transport handshake, when it is about to transfer data and the data
+ * layer is not ready yet.
+ */
+struct mux_ops {
+ int (*init)(struct connection *conn); /* early initialization */
+ void (*recv)(struct connection *conn); /* mux-layer recv callback */
+ void (*send)(struct connection *conn); /* mux-layer send callback */
+ int (*wake)(struct connection *conn); /* mux-layer callback to report activity, mandatory */
+ void (*release)(struct connection *conn); /* release all resources allocated by the mux */
+ char name[8]; /* mux layer name, zero-terminated */
+};
+
/* data_cb describes the data layer's recv and send callbacks which are called
* when I/O activity was detected after the transport layer is ready. These
* callbacks are supposed to make use of the xprt_ops above to exchange data
@@ -297,11 +313,13 @@
unsigned int flags; /* CO_FL_* */
const struct protocol *ctrl; /* operations at the socket layer */
const struct xprt_ops *xprt; /* operations at the transport layer */
+ const struct mux_ops *mux; /* mux layer opreations. Must be set before xprt->init() */
const struct data_cb *data; /* data layer callbacks. Must be set before xprt->init() */
void *xprt_ctx; /* general purpose pointer, initialized to NULL */
- int tmp_early_data; /* 1st byte of early data, if any */
+ void *mux_ctx; /* mux-specific context, initialized to NULL */
void *owner; /* pointer to upper layer's entity (eg: session, stream interface) */
int xprt_st; /* transport layer state, initialized to zero */
+ int tmp_early_data; /* 1st byte of early data, if any */
union conn_handle handle; /* connection handle at the socket layer */
enum obj_type *target; /* the target to connect to (server, proxy, applet, ...) */
struct list list; /* attach point to various connection lists (idle, ...) */