net: dhcpv4: add vendor specific option callback

In certain scenarios, it may be necessary to get values of additional
options from the application layer. With this patch, this can be
accomplished by registering a callback with the DHCP client.

This change has been tested using the posix build in qemu.

Signed-off-by: Fin Maaß <f.maass@vogl-electronic.com>

include/zephyr/net/dhcpv4.h

@@ -163,6 +163,48 @@ int net_dhcpv4_remove_option_callback(struct net_dhcpv4_option_callback *cb);
 
 #endif /* CONFIG_NET_DHCPV4_OPTION_CALLBACKS */
 
+#ifdef CONFIG_NET_DHCPV4_OPTION_CALLBACKS_VENDOR_SPECIFIC
+
+/**
+ * @brief Helper to initialize a struct net_dhcpv4_option_callback for encapsulated vendor-specific
+ * options properly
+ * @param callback A valid Application's callback structure pointer.
+ * @param handler A valid handler function pointer.
+ * @param option The DHCP encapsulated vendor-specific option the callback responds to.
+ * @param data A pointer to a buffer for max_length bytes.
+ * @param max_length The maximum length of the data returned.
+ */
+static inline void
+net_dhcpv4_init_option_vendor_callback(struct net_dhcpv4_option_callback *callback,
+				       net_dhcpv4_option_callback_handler_t handler, uint8_t option,
+				       void *data, size_t max_length)
+{
+	__ASSERT(callback, "Callback pointer should not be NULL");
+	__ASSERT(handler, "Callback handler pointer should not be NULL");
+	__ASSERT(data, "Data pointer should not be NULL");
+
+	callback->handler = handler;
+	callback->option = option;
+	callback->data = data;
+	callback->max_length = max_length;
+}
+
+/**
+ * @brief Add an application callback for encapsulated vendor-specific options.
+ * @param cb A valid application's callback structure pointer.
+ * @return 0 if successful, negative errno code on failure.
+ */
+int net_dhcpv4_add_option_vendor_callback(struct net_dhcpv4_option_callback *cb);
+
+/**
+ * @brief Remove an application callback for encapsulated vendor-specific options.
+ * @param cb A valid application's callback structure pointer.
+ * @return 0 if successful, negative errno code on failure.
+ */
+int net_dhcpv4_remove_option_vendor_callback(struct net_dhcpv4_option_callback *cb);
+
+#endif /* CONFIG_NET_DHCPV4_OPTION_CALLBACKS_VENDOR_SPECIFIC */
+
 /**
  *  @brief Start DHCPv4 client on an iface
  *

subsys/net/lib/dhcpv4/Kconfig

@@ -46,6 +46,14 @@ config NET_DHCPV4_MAX_REQUESTED_OPTIONS
 	  DHCPv4 request message. The options are added using the
 	  net_dhcpv4_add_option_callback() API.
 
+config NET_DHCPV4_OPTION_CALLBACKS_VENDOR_SPECIFIC
+	bool "Encapsulated vendor specific option callbacks"
+	depends on NET_DHCPV4
+	select NET_DHCPV4_OPTION_CALLBACKS
+	help
+	  If set, custom callbacks for encapsulated vendor-specific
+	  information in DHCP option 43 can be added.
+
 config NET_DHCPV4_ACCEPT_UNICAST
 	bool "Accept unicast DHCPv4 traffic"
 	depends on NET_DHCPV4

subsys/net/lib/dhcpv4/dhcpv4.c

@@ -49,11 +49,18 @@ static sys_slist_t option_callbacks = SYS_SLIST_STATIC_INIT(&option_callbacks);
 static int unique_types_in_callbacks;
 #endif
 
+#if defined(CONFIG_NET_DHCPV4_OPTION_CALLBACKS_VENDOR_SPECIFIC)
+static sys_slist_t option_vendor_callbacks = SYS_SLIST_STATIC_INIT(&option_vendor_callbacks);
+#endif
+
 static const uint8_t min_req_options[] = {
 	DHCPV4_OPTIONS_SUBNET_MASK,
 	DHCPV4_OPTIONS_ROUTER,
 #ifdef CONFIG_NET_DHCPV4_OPTION_NTP_SERVER
 	DHCPV4_OPTIONS_NTP_SERVER,
+#endif
+#ifdef CONFIG_NET_DHCPV4_OPTION_CALLBACKS_VENDOR_SPECIFIC
+	DHCPV4_OPTIONS_VENDOR_SPECIFIC,
 #endif
 	DHCPV4_OPTIONS_DNS_SERVER
 };
@@ -752,6 +759,71 @@ static void dhcpv4_timeout(struct k_work *work)
 	}
 }
 
+#if defined(CONFIG_NET_DHCPV4_OPTION_CALLBACKS_VENDOR_SPECIFIC)
+
+static int dhcpv4_parse_option_vendor(struct net_pkt *pkt, struct net_if *iface,
+				      enum net_dhcpv4_msg_type *msg_type, int length)
+{
+	struct net_dhcpv4_option_callback *cb, *tmp;
+	struct net_pkt_cursor backup;
+	uint8_t len;
+	uint8_t type;
+
+	if (length < 3) {
+		NET_ERR("Vendor-specific option parsing, length too short");
+		net_pkt_skip(pkt, length);
+		return -EBADMSG;
+	}
+
+	while (!net_pkt_read_u8(pkt, &type)) {
+		if (type == DHCPV4_OPTIONS_END) {
+			NET_DBG("Vendor-specific options_end");
+			return 0;
+		}
+		length--;
+
+		if (length <= 0) {
+			NET_ERR("Vendor-specific option parsing, malformed option");
+			return -EBADMSG;
+		}
+
+		if (net_pkt_read_u8(pkt, &len)) {
+			NET_ERR("Vendor-specific option parsing, bad length");
+			return -ENOBUFS;
+		}
+		length--;
+		if (length < len) {
+			NET_ERR("Vendor-specific option parsing, length too long");
+			net_pkt_skip(pkt, length);
+			return -EBADMSG;
+		}
+		net_pkt_cursor_backup(pkt, &backup);
+
+		SYS_SLIST_FOR_EACH_CONTAINER_SAFE(&option_vendor_callbacks, cb, tmp, node) {
+			if (cb->option == type) {
+				NET_ASSERT(cb->handler, "No callback handler!");
+
+				if (net_pkt_read(pkt, cb->data, MIN(cb->max_length, len))) {
+					NET_DBG("option vendor callback, read err");
+					return -ENOBUFS;
+				}
+
+				cb->handler(cb, len, *msg_type, iface);
+				net_pkt_cursor_restore(pkt, &backup);
+			}
+		}
+		net_pkt_skip(pkt, len);
+		length = length - len;
+		if (length <= 0) {
+			NET_DBG("Vendor-specific options_end (no code 255)");
+			return 0;
+		}
+	}
+	return -ENOBUFS;
+}
+
+#endif /* CONFIG_NET_DHCPV4_OPTION_CALLBACKS_VENDOR_SPECIFIC */
+
 /* Parse DHCPv4 options and retrieve relevant information
  * as per RFC 2132.
  */
@@ -923,6 +995,24 @@ static bool dhcpv4_parse_options(struct net_pkt *pkt,
 			break;
 		}
 #endif /* CONFIG_NET_DHCPV4_OPTION_NTP_SERVER */
+#if defined(CONFIG_NET_DHCPV4_OPTION_CALLBACKS_VENDOR_SPECIFIC)
+		case DHCPV4_OPTIONS_VENDOR_SPECIFIC: {
+			if (!sys_slist_is_empty(&option_vendor_callbacks)) {
+				NET_DBG("options_vendor_specific");
+				if (dhcpv4_parse_option_vendor(pkt, iface, msg_type, length) ==
+				    -ENOBUFS) {
+					return false;
+				}
+			} else {
+				NET_DBG("options_vendor_specific, no callbacks");
+				if (net_pkt_skip(pkt, length)) {
+					NET_DBG("options_vendor_specific, skip err");
+					return false;
+				}
+			}
+			break;
+		}
+#endif
 		case DHCPV4_OPTIONS_LEASE_TIME:
 			if (length != 4U) {
 				NET_ERR("options_lease_time, bad length");
@@ -1424,6 +1514,38 @@ int net_dhcpv4_remove_option_callback(struct net_dhcpv4_option_callback *cb)
 
 #endif /* CONFIG_NET_DHCPV4_OPTION_CALLBACKS */
 
+#if defined(CONFIG_NET_DHCPV4_OPTION_CALLBACKS_VENDOR_SPECIFIC)
+
+int net_dhcpv4_add_option_vendor_callback(struct net_dhcpv4_option_callback *cb)
+{
+	if (cb == NULL || cb->handler == NULL) {
+		return -EINVAL;
+	}
+
+	k_mutex_lock(&lock, K_FOREVER);
+	sys_slist_prepend(&option_vendor_callbacks, &cb->node);
+	k_mutex_unlock(&lock);
+	return 0;
+}
+
+int net_dhcpv4_remove_option_vendor_callback(struct net_dhcpv4_option_callback *cb)
+{
+	int ret = 0;
+
+	if (cb == NULL || cb->handler == NULL) {
+		return -EINVAL;
+	}
+
+	k_mutex_lock(&lock, K_FOREVER);
+	if (!sys_slist_find_and_remove(&option_vendor_callbacks, &cb->node)) {
+		ret = -EINVAL;
+	}
+	k_mutex_unlock(&lock);
+	return ret;
+}
+
+#endif /* CONFIG_NET_DHCPV4_OPTION_CALLBACKS_VENDOR_SPECIFIC */
+
 void net_dhcpv4_start(struct net_if *iface)
 {
 	return dhcpv4_start_internal(iface, true);

subsys/net/lib/dhcpv4/dhcpv4_internal.h

@@ -56,6 +56,7 @@ struct dhcp_msg {
 #define DHCPV4_OPTIONS_DNS_SERVER	6
 #define DHCPV4_OPTIONS_HOST_NAME	12
 #define DHCPV4_OPTIONS_NTP_SERVER	42
+#define DHCPV4_OPTIONS_VENDOR_SPECIFIC	43
 #define DHCPV4_OPTIONS_REQ_IPADDR	50
 #define DHCPV4_OPTIONS_LEASE_TIME	51
 #define DHCPV4_OPTIONS_MSG_TYPE		53