net: dhcpv4: Implement DHCPv4 server

Add basic socket-based implementation of DHCPv4 sever.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>

include/zephyr/net/dhcpv4_server.h

@@ -0,0 +1,118 @@
+/** @file
+ *  @brief DHCPv4 Server API
+ */
+
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_INCLUDE_NET_DHCPV4_SERVER_H_
+#define ZEPHYR_INCLUDE_NET_DHCPV4_SERVER_H_
+
+#include <zephyr/net/net_ip.h>
+#include <zephyr/sys_clock.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief DHCPv4 server
+ * @defgroup dhcpv4_server DHCPv4 server
+ * @ingroup networking
+ * @{
+ */
+
+/** @cond INTERNAL_HIDDEN */
+
+struct net_if;
+
+#define DHCPV4_CLIENT_ID_MAX_SIZE 20
+
+enum dhcpv4_server_addr_state {
+	DHCPV4_SERVER_ADDR_FREE,
+	DHCPV4_SERVER_ADDR_RESERVED,
+	DHCPV4_SERVER_ADDR_ALLOCATED,
+	DHCPV4_SERVER_ADDR_DECLINED,
+};
+
+struct dhcpv4_client_id {
+	uint8_t buf[DHCPV4_CLIENT_ID_MAX_SIZE];
+	uint8_t len;
+};
+
+struct dhcpv4_addr_slot {
+	enum dhcpv4_server_addr_state state;
+	struct dhcpv4_client_id client_id;
+	struct in_addr addr;
+	uint32_t lease_time;
+	k_timepoint_t expiry;
+};
+
+/** @endcond */
+
+/**
+ *  @brief Start DHCPv4 server instance on an iface
+ *
+ *  @details Start DHCPv4 server on a given interface. The server will start
+ *  listening for DHCPv4 Discover/Request messages on the interface and assign
+ *  IPv4 addresses from the configured address pool accordingly.
+ *
+ *  @param iface A valid pointer on an interface
+ *  @param base_addr First IPv4 address from the DHCPv4 address pool. The number
+ *  of addresses in the pool is configured statically with Kconfig
+ *  (CONFIG_NET_DHCPV4_SERVER_ADDR_COUNT).
+ *
+ *  @return 0 on success, a negative error code otherwise.
+ */
+int net_dhcpv4_server_start(struct net_if *iface, struct in_addr *base_addr);
+
+/**
+ *  @brief Stop DHCPv4 server instance on an iface
+ *
+ *  @details Stop DHCPv4 server on a given interface. DHCPv4 requests will no
+ *  longer be handled on the interface, and all of the allocations are cleared.
+ *
+ *  @param iface A valid pointer on an interface
+ *
+ *  @return 0 on success, a negative error code otherwise.
+ */
+int net_dhcpv4_server_stop(struct net_if *iface);
+
+/**
+ * @typedef net_dhcpv4_lease_cb_t
+ * @brief Callback used while iterating over active DHCPv4 address leases
+ *
+ * @param iface Pointer to the network interface
+ * @param lease Pointer to the DHPCv4 address lease slot
+ * @param user_data A valid pointer to user data or NULL
+ */
+typedef void (*net_dhcpv4_lease_cb_t)(struct net_if *iface,
+				      struct dhcpv4_addr_slot *lease,
+				      void *user_data);
+
+/**
+ * @brief Iterate over all DHCPv4 address leases on a given network interface
+ * and call callback for each lease. In case no network interface is provided
+ * (NULL interface pointer), will iterate over all interfaces running DHCPv4
+ * server instance.
+ *
+ * @param iface Pointer to the network interface, can be NULL
+ * @param cb User-supplied callback function to call
+ * @param user_data User specified data
+ */
+int net_dhcpv4_server_foreach_lease(struct net_if *iface,
+				    net_dhcpv4_lease_cb_t cb,
+				    void *user_data);
+
+/**
+ * @}
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_INCLUDE_NET_DHCPV4_SERVER_H_ */

subsys/net/ip/dhcpv4.h

@@ -62,6 +62,7 @@ struct dhcp_msg {
 #define DHCPV4_OPTIONS_REQ_LIST		55
 #define DHCPV4_OPTIONS_RENEWAL		58
 #define DHCPV4_OPTIONS_REBINDING	59
+#define DHCPV4_OPTIONS_CLIENT_ID	61
 #define DHCPV4_OPTIONS_END		255
 
 /* Useful size macros */
@@ -142,4 +143,14 @@ static inline bool net_dhcpv4_accept_unicast(struct net_pkt *pkt)
 
 #endif /* CONFIG_NET_DHCPV4 && CONFIG_NET_DHCPV4_ACCEPT_UNICAST */
 
+#if defined(CONFIG_NET_DHCPV4_SERVER)
+
+void net_dhcpv4_server_init(void);
+
+#else
+
+#define net_dhcpv4_server_init()
+
+#endif /* CONFIG_NET_DHCPV4_SERVER */
+
 #endif /* __INTERNAL_DHCPV4_H */

subsys/net/ip/net_core.c

@@ -559,6 +559,8 @@ static inline int services_init(void)
 		return status;
 	}
 
+	net_dhcpv4_server_init();
+
 	dns_init_resolver();
 	websocket_init();
 

subsys/net/lib/CMakeLists.txt

@@ -15,6 +15,7 @@ add_subdirectory_ifdef(CONFIG_NET_CAPTURE            capture)
 add_subdirectory_ifdef(CONFIG_NET_ZPERF              zperf)
 add_subdirectory_ifdef(CONFIG_NET_SHELL              shell)
 add_subdirectory_ifdef(CONFIG_NET_TRICKLE            trickle)
+add_subdirectory_ifdef(CONFIG_NET_DHCPV4_SERVER      dhcpv4)
 
 if (CONFIG_DNS_RESOLVER
     OR CONFIG_MDNS_RESPONDER

subsys/net/lib/Kconfig

@@ -39,6 +39,8 @@ menu "Network additional services"
 
 source "subsys/net/lib/capture/Kconfig"
 
+source "subsys/net/lib/dhcpv4/Kconfig"
+
 source "subsys/net/lib/trickle/Kconfig"
 
 source "subsys/net/lib/zperf/Kconfig"

subsys/net/lib/dhcpv4/CMakeLists.txt

@@ -0,0 +1,11 @@
+# Copyright (c) 2024 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: Apache-2.0
+
+zephyr_library()
+
+zephyr_library_include_directories(${ZEPHYR_BASE}/subsys/net/ip)
+
+zephyr_library_sources(
+  dhcpv4_server.c
+  )

subsys/net/lib/dhcpv4/Kconfig

@@ -0,0 +1,46 @@
+# DHCPv4 server implementation for Zephyr
+
+# Copyright (c) 2024 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: Apache-2.0
+
+config NET_DHCPV4_SERVER
+	bool "DHCPv4 server"
+	depends on NET_IPV4 && NET_UDP
+	select NET_SOCKETS
+	select NET_SOCKETS_SERVICE
+
+if NET_DHCPV4_SERVER
+
+module = NET_DHCPV4_SERVER
+module-dep = NET_LOG
+module-str = Log level for DHCPv4 server
+module-help = Enables DHCPv4 server output debug messages
+source "subsys/net/Kconfig.template.log_config.net"
+
+config NET_DHCPV4_SERVER_INSTANCES
+	int "Maximum number of DHCPv4 server instances"
+	default 1
+	help
+	  Maximum number of DHCPv4 server instances supported by the system.
+	  Each network interface that wants to act as a DHCPv4 server requires
+	  a separate instance.
+
+config NET_DHCPV4_SERVER_ADDR_COUNT
+	int "Number of IPv4 addresses that can be assigned by the server"
+	default 4
+	help
+	  Maximum number of IPv4 addresses that can be assigned by the DHCPv4
+	  server instance. The base IPv4 address in the address pool is provided
+	  at runtime, during server initialization. Consecutive addresses in the
+	  pool have the lowest address octet incremented.
+
+config NET_DHCPV4_SERVER_ADDR_LEASE_TIME
+	int "Lease time for IPv4 addresses assigned by the server (seconds)"
+	default 86400
+	help
+	  Lease time in seconds for IPv4 addresses assigned by the server.
+	  The lease time determines when the IPv4 address lease expires if the
+	  client does not renew it.
+
+endif # NET_DHCPV4_SERVER