net: ethernet: bridging support

This adds the ability to create Ethernet bridges for connecting
separate Ethernet segments together to appear as a single
Ethernet network.

This mimics the Linux functionality of the same name.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>

include/linker/common-ram.ld

@@ -5,7 +5,8 @@
 #define NETWORK_RAM_SECTIONS \
 	Z_ITERABLE_SECTION_RAM(net_if, 4) \
 	Z_ITERABLE_SECTION_RAM(net_if_dev, 4) \
-	Z_ITERABLE_SECTION_RAM(net_l2, 4)
+	Z_ITERABLE_SECTION_RAM(net_l2, 4) \
+	Z_ITERABLE_SECTION_RAM(eth_bridge, 4)
 #endif
 #endif /* NETWORKING */
 

include/net/ethernet.h

@@ -34,6 +34,10 @@
 #include <net/dsa.h>
 #endif
 
+#if defined(CONFIG_NET_ETHERNET_BRIDGE)
+#include <net/ethernet_bridge.h>
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -521,6 +525,10 @@ struct ethernet_context {
 	ATOMIC_DEFINE(interfaces, NET_VLAN_MAX_COUNT);
 #endif
 
+#if defined(CONFIG_NET_ETHERNET_BRIDGE)
+	struct eth_bridge_iface_context bridge;
+#endif
+
 	/** Carrier ON/OFF handler worker. This is used to create
 	 * network interface UP/DOWN event when ethernet L2 driver
 	 * notices carrier ON/OFF situation. We must not create another

include/net/ethernet_bridge.h

@@ -0,0 +1,189 @@
+/** @file
+ * @brief Ethernet Bridge public header file
+ *
+ * Ethernet Bridges connect two or more Ethernet networks together and
+ * transparently forward packets from one network to the others as if
+ * they were part of the same network.
+ */
+
+/*
+ * Copyright (c) 2021 BayLibre SAS
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_INCLUDE_NET_ETHERNET_BRIDGE_H_
+#define ZEPHYR_INCLUDE_NET_ETHERNET_BRIDGE_H_
+
+#include <sys/slist.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Ethernet Bridging API
+ * @defgroup eth_bridge Ethernet Bridging API
+ * @ingroup networking
+ * @{
+ */
+
+/** @cond INTERNAL_HIDDEN */
+
+struct eth_bridge {
+	struct k_mutex lock;
+	sys_slist_t interfaces;
+	sys_slist_t listeners;
+};
+
+#define ETH_BRIDGE_INITIALIZER(obj) \
+	{ \
+		.lock		= { }, \
+		.interfaces	= SYS_SLIST_STATIC_INIT(&obj.interfaces), \
+		.listeners	= SYS_SLIST_STATIC_INIT(&obj.listeners), \
+	}
+
+/** @endcond */
+
+/**
+ * @brief Statically define and initialize a bridge instance.
+ *
+ * @param name Name of the bridge object
+ */
+#define ETH_BRIDGE_INIT(name) \
+	Z_STRUCT_SECTION_ITERABLE(eth_bridge, name) = \
+		ETH_BRIDGE_INITIALIZER(name)
+
+struct eth_bridge_iface_context {
+	sys_snode_t node;
+	struct eth_bridge *instance;
+	bool allow_tx;
+};
+
+struct eth_bridge_listener {
+	sys_snode_t node;
+	struct k_fifo pkt_queue;
+};
+
+/**
+ * @brief Add an Ethernet network interface to a bridge
+ *
+ * This adds a network interface to a bridge. The interface is then put
+ * into promiscuous mode, all packets received by this interface are sent
+ * to the bridge, and any other packets sent to the bridge (with some
+ * exceptions) are transmitted via this interface.
+ *
+ * For transmission from the bridge to occur via this interface, it is
+ * necessary to enable TX mode with eth_bridge_iface_tx(). TX mode is
+ * initially disabled.
+ *
+ * Once an interface is added to a bridge, all its incoming traffic is
+ * diverted to the bridge. However, packets sent out with net_if_queue_tx()
+ * via this interface are not subjected to the bridge.
+ *
+ * @param br A pointer to an initialized bridge object
+ * @param iface Interface to add
+ *
+ * @return 0 if OK, negative error code otherwise.
+ */
+int eth_bridge_iface_add(struct eth_bridge *br, struct net_if *iface);
+
+/**
+ * @brief Remove an Ethernet network interface from a bridge
+ *
+ * @param br A pointer to an initialized bridge object
+ * @param iface Interface to remove
+ *
+ * @return 0 if OK, negative error code otherwise.
+ */
+int eth_bridge_iface_remove(struct eth_bridge *br, struct net_if *iface);
+
+/**
+ * @brief Enable/disable transmission mode for a bridged interface
+ *
+ * When TX mode is off, the interface may receive packets and send them to
+ * the bridge but no packets coming from the bridge will be sent through this
+ * interface. When TX mode is on, both incoming and outgoing packets are
+ * allowed.
+ *
+ * @param iface Interface to configure
+ * @param allow true to activate TX mode, false otherwise
+ *
+ * @return 0 if OK, negative error code otherwise.
+ */
+int eth_bridge_iface_allow_tx(struct net_if *iface, bool allow);
+
+/**
+ * @brief Add (register) a listener to the bridge
+ *
+ * This lets a software listener register a pointer to a provided FIFO for
+ * receiving packets sent to the bridge. The listener is responsible for
+ * emptying the FIFO with k_fifo_get() which will return a struct net_pkt
+ * pointer, and releasing the packet with net_pkt_unref() when done with it.
+ *
+ * The listener wishing not to receive any more packets should simply
+ * unregister itself with eth_bridge_listener_remove().
+ *
+ * @param br A pointer to an initialized bridge object
+ * @param l A pointer to an initialized listener instance.
+ *
+ * @return 0 if OK, negative error code otherwise.
+ */
+int eth_bridge_listener_add(struct eth_bridge *br, struct eth_bridge_listener *l);
+
+/**
+ * @brief Remove (unregister) a listener from the bridge
+ *
+ * @param br A pointer to an initialized bridge object
+ * @param l A pointer to the listener instance to be removed.
+ *
+ * @return 0 if OK, negative error code otherwise.
+ */
+int eth_bridge_listener_remove(struct eth_bridge *br, struct eth_bridge_listener *l);
+
+/**
+ * @brief Get bridge index according to pointer
+ *
+ * @param br Pointer to bridge instance
+ *
+ * @return Bridge index
+ */
+int eth_bridge_get_index(struct eth_bridge *br);
+
+/**
+ * @brief Get bridge instance according to index
+ *
+ * @param index Bridge instance index
+ *
+ * @return Pointer to bridge instance or NULL if not found.
+ */
+struct eth_bridge *eth_bridge_get_by_index(int index);
+
+/**
+ * @typedef eth_bridge_cb_t
+ * @brief Callback used while iterating over bridge instances
+ *
+ * @param br Pointer to bridge instance
+ * @param user_data User supplied data
+ */
+typedef void (*eth_bridge_cb_t)(struct eth_bridge *br, void *user_data);
+
+/**
+ * @brief Go through all the bridge instances in order to get
+ *        information about them. This is mainly useful in
+ *        net-shell to print data about currently active bridges.
+ *
+ * @param cb Callback to call for each bridge instance
+ * @param user_data User supplied data
+ */
+void net_eth_bridge_foreach(eth_bridge_cb_t cb, void *user_data);
+
+/**
+ * @}
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_INCLUDE_NET_ETHERNET_BRIDGE_H_ */

include/net/net_pkt.h

@@ -181,10 +181,17 @@ struct net_pkt {
 					* segment.
 					*/
 #endif
+
 	uint8_t captured : 1; /* Set to 1 if this packet is already being
 			       * captured
 			       */
 
+	uint8_t l2_bridged : 1; /* set to 1 if this packet comes from a bridge
+				 * and already contains its L2 header to be
+				 * preserved. Useful only if
+				 * defined(CONFIG_NET_ETHERNET_BRIDGE).
+				 */
+
 	union {
 		/* IPv6 hop limit or IPv4 ttl for this network packet.
 		 * The value is shared between IPv6 and IPv4.
@@ -349,6 +356,18 @@ static inline void net_pkt_set_captured(struct net_pkt *pkt, bool is_captured)
 	pkt->captured = is_captured;
 }
 
+static inline bool net_pkt_is_l2_bridged(struct net_pkt *pkt)
+{
+	return IS_ENABLED(CONFIG_NET_ETHERNET_BRIDGE) ? !!(pkt->l2_bridged) : 0;
+}
+
+static inline void net_pkt_set_l2_bridged(struct net_pkt *pkt, bool is_l2_bridged)
+{
+	if (IS_ENABLED(CONFIG_NET_ETHERNET_BRIDGE)) {
+		pkt->l2_bridged = is_l2_bridged;
+	}
+}
+
 static inline uint8_t net_pkt_ip_hdr_len(struct net_pkt *pkt)
 {
 	return pkt->ip_hdr_len;