Bluetooth: Mesh: Add bridging functionality

Adds subnet bridging functionality to the network layer.
Also fixes brg_cfg_srv for minor issues to get it working.

Signed-off-by: Omkar Kulkarni <omkar.kulkarni@nordicsemi.no>

include/zephyr/bluetooth/mesh/brg_cfg_srv.h

@@ -32,8 +32,8 @@ extern "C" {
 			 NULL, NULL, &bt_mesh_brg_cfg_srv_cb)
 
 /** @cond INTERNAL_HIDDEN */
-extern const struct bt_mesh_model_op bt_mesh_brg_cfg_srv_op[];
-extern const struct bt_mesh_model_cb bt_mesh_brg_cfg_srv_cb;
+extern const struct bt_mesh_model_op _bt_mesh_brg_cfg_srv_op[];
+extern const struct bt_mesh_model_cb _bt_mesh_brg_cfg_srv_cb;
 /** @endcond */
 
 /**

subsys/bluetooth/mesh/Kconfig

@@ -664,12 +664,20 @@ menu "Replay Protection List"
 
 config BT_MESH_CRPL
 	int "Maximum capacity of the replay protection list"
+	default 26 if BT_MESH_BRG_CFG_SRV
 	default 10
 	range 2 $(UINT16_MAX)
 	help
-	  This options specifies the maximum capacity of the replay
+	  This option specifies the maximum capacity of the replay
 	  protection list. This option is similar to the network message
-	  cache size, but has a different purpose.
+	  cache size, but has a purpose of preventing replay attacks.
+
+	  Note that: To ensure sufficient space in CRPL for normal node
+	  operations and as specified by other Bluetooth specification
+	  requirements, when subnet bridge functionality is enabled on a node,
+	  you should increase the CRPL capacity in your project configuration
+	  file with the number of bridging table entries
+	  (BT_MESH_BRG_TABLE_ITEMS_MAX) specified for the project as a minimum.
 
 choice BT_MESH_RPL_STORAGE_MODE
 	prompt "Replay protection list storage mode"

subsys/bluetooth/mesh/brg_cfg_srv.c

@@ -6,6 +6,7 @@
 
 #include <zephyr/bluetooth/mesh.h>
 #include <zephyr/bluetooth/mesh/brg_cfg.h>
+#include "access.h"
 #include "brg_cfg.h"
 #include "foundation.h"
 #include "subnet.h"
@@ -307,6 +308,13 @@ static int brg_cfg_srv_init(const struct bt_mesh_model *model)
 		return -EINVAL;
 	}
 
+	/*
+	 * Bridge Configuration Server model security is device key based and only the local
+	 * device key is allowed to access this model.
+	 */
+	model->keys[0] = BT_MESH_KEY_DEV_LOCAL;
+	model->rt->flags |= BT_MESH_MOD_DEVKEY_ONLY;
+
 	bt_mesh_model_extend(model, config_srv);
 
 	return 0;

subsys/bluetooth/mesh/net.c

@@ -36,6 +36,7 @@
 #include "cfg.h"
 #include "statistic.h"
 #include "sar_cfg_internal.h"
+#include "brg_cfg.h"
 
 #define LOG_LEVEL CONFIG_BT_MESH_NET_LOG_LEVEL
 #include <zephyr/logging/log.h>
@@ -54,6 +55,13 @@ LOG_MODULE_REGISTER(bt_mesh_net);
 #define SRC(pdu)           (sys_get_be16(&(pdu)[5]))
 #define DST(pdu)           (sys_get_be16(&(pdu)[7]))
 
+/* Information needed for bridging the network PDUs */
+struct pdu_ctx {
+	struct net_buf_simple *sbuf;
+	struct net_buf_simple_state *state;
+	struct bt_mesh_net_rx *rx;
+};
+
 /* Mesh network information for persistent storage. */
 struct net_val {
 	uint16_t primary_addr;
@@ -756,6 +764,19 @@ static void bt_mesh_net_relay(struct net_buf_simple *sbuf,
 	bt_mesh_adv_unref(adv);
 }
 
+#if IS_ENABLED(CONFIG_BT_MESH_BRG_CFG_SRV)
+static void bt_mesh_sbr_check_cb(uint16_t new_net_idx, void *user_data)
+{
+	struct pdu_ctx *ctx = (struct pdu_ctx *)user_data;
+
+	if (new_net_idx < BT_MESH_BRG_CFG_NETIDX_NOMATCH) {
+		ctx->rx->ctx.net_idx = new_net_idx;
+		net_buf_simple_restore(ctx->sbuf, ctx->state);
+		bt_mesh_net_relay(ctx->sbuf, ctx->rx);
+	}
+}
+#endif
+
 void bt_mesh_net_header_parse(struct net_buf_simple *buf,
 			      struct bt_mesh_net_rx *rx)
 {
@@ -893,6 +914,28 @@ void bt_mesh_net_recv(struct net_buf_simple *data, int8_t rssi,
 		net_buf_simple_restore(&buf, &state);
 		bt_mesh_net_relay(&buf, &rx);
 	}
+
+#if IS_ENABLED(CONFIG_BT_MESH_BRG_CFG_SRV)
+	struct pdu_ctx tx_ctx = {
+		.sbuf = &buf,
+		.state = &state,
+		.rx = &rx,
+	};
+
+	/* Bridge the traffic if enabled */
+	if (!bt_mesh_brg_cfg_enable_get()) {
+		return;
+	}
+
+	struct bt_mesh_rpl *rpl = NULL;
+
+	if (bt_mesh_rpl_check(&rx, &rpl)) {
+		return;
+	}
+
+	bt_mesh_brg_cfg_tbl_foreach_subnet(rx.ctx.addr, rx.ctx.recv_dst, rx.ctx.net_idx,
+					    bt_mesh_sbr_check_cb, &tx_ctx);
+#endif
 }
 
 static void ivu_refresh(struct k_work *work)