Bluetooth: Mesh: Split out provisioning bearers

Splits PB-ADV and PB-GATT into separate modules with a common interface
to modularize prov.c.

Additional trivial fixes from testing:

- Reduces warnings for normal occurances like repeated packets.
- Makes link ack a non-reliable packet to prevent it from being repeated
  until prov invite.
- Provisioner does not send link fail, but closes the link (as per spec
  section 5.4.4). This prevents lingering zombie links on both sides.

Signed-off-by: Trond Einar Snekvik <Trond.Einar.Snekvik@nordicsemi.no>

subsys/bluetooth/mesh/prov_bearer.h

@@ -0,0 +1,113 @@
+/*  Bluetooth Mesh */
+
+/*
+ * Copyright (c) 2020 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define PROTOCOL_TIMEOUT     K_SECONDS(60)
+
+/** @def PROV_BEARER_BUF_HEADROOM
+ *
+ *  @brief Required headroom for the bearer packet buffers.
+ */
+#if defined(CONFIG_BT_MESH_PB_GATT)
+#define PROV_BEARER_BUF_HEADROOM 5
+#else
+#define PROV_BEARER_BUF_HEADROOM 0
+#endif
+
+enum prov_bearer_link_status {
+	PROV_BEARER_LINK_STATUS_SUCCESS,
+	PROV_BEARER_LINK_STATUS_TIMEOUT,
+	PROV_BEARER_LINK_STATUS_FAIL,
+};
+
+struct prov_bearer;
+
+/** Callbacks from bearer to host */
+struct prov_bearer_cb {
+
+	void (*link_opened)(const struct prov_bearer *bearer, void *cb_data);
+
+	void (*link_closed)(const struct prov_bearer *bearer, void *cb_data,
+			    enum prov_bearer_link_status reason);
+
+	void (*error)(const struct prov_bearer *bearer, void *cb_data,
+		      u8_t err);
+
+	void (*recv)(const struct prov_bearer *bearer, void *cb_data,
+		     struct net_buf_simple *buf);
+};
+
+typedef void (*prov_bearer_send_complete_t)(int err, void *cb_data);
+
+/** Provisioning bearer API */
+struct prov_bearer {
+	/** Provisioning bearer type. */
+	bt_mesh_prov_bearer_t type;
+
+	/** @brief Enable link establishment as a provisionee.
+	 *
+	 *  Prompts the bearer to make itself visible to provisioners, and
+	 *  start accepting link open messages.
+	 *
+	 *  @param cb Bearer event callbacks used for the duration of the link.
+	 *  @param cb_data Context parameter to pass to the bearer callbacks.
+	 *
+	 *  @return Zero on success, or (negative) error code otherwise.
+	 */
+	int (*link_accept)(const struct prov_bearer_cb *cb, void *cb_data);
+
+	/** @brief Send a packet on an established link.
+	 *
+	 *  @param buf     Payload buffer. Requires @ref
+	 *                 PROV_BEARER_BUF_HEADROOM bytes of headroom.
+	 *  @param cb      Callback to call when sending is complete.
+	 *  @param cb_data Callback data.
+	 *
+	 *  @return Zero on success, or (negative) error code otherwise.
+	 */
+	int (*send)(struct net_buf_simple *buf, prov_bearer_send_complete_t cb,
+		    void *cb_data);
+
+	/** @brief Clear any ongoing transmissions, if possible.
+	 *
+	 *  Bearers that don't support tx clearing must implement this callback
+	 *  and leave it empty.
+	 */
+	void (*clear_tx)(void);
+
+	/* Only available in provisioners: */
+
+	/** @brief Open a new link as a provisioner.
+	 *
+	 *  Only available in provisioners. Bearers that don't support the
+	 *  provisioner role should leave this as NULL.
+	 *
+	 *  @param uuid UUID of the node to establish a link to.
+	 *  @param timeout Protocol timeout.
+	 *  @param cb Bearer event callbacks used for the duration of the link.
+	 *  @param cb_data Context parameter to pass to the bearer callbacks.
+	 *
+	 *  @return Zero on success, or (negative) error code otherwise.
+	 */
+	int (*link_open)(const u8_t uuid[16], s32_t timeout,
+			 const struct prov_bearer_cb *cb, void *cb_data);
+
+	/** @brief Close the current link.
+	 *
+	 *  Only available in provisioners. Bearers that don't support the
+	 *  provisioner role should leave this as NULL.
+	 *
+	 *  @param status Link status for the link close message.
+	 */
+	void (*link_close)(enum prov_bearer_link_status status);
+};
+
+extern const struct prov_bearer pb_adv;
+extern const struct prov_bearer pb_gatt;
+
+void pb_adv_init(void);
+void pb_gatt_init(void);