Added some initial support for a userspace server to receive requests.

7 files changed, 597 insertions, 67 deletions

diff --git a/ncr-storage-low.c b/ncr-storage-low.c
index 47cd8e84d8e..418bc8ff969 100644
--- a/ncr-storage-low.c
+++ b/ncr-storage-low.c
@@ -41,6 +41,7 @@ struct event_item_st {
 	struct completion completed;
 	void* reply;
 	size_t reply_size;
+	uint32_t ireply;
 	uint32_t id;
 };
 
@@ -68,10 +69,11 @@ struct event_item_st* item;
 	return 0;
 }
 
-static void event_wait(uint32_t id)
+static int event_wait(uint32_t id)
 {
 struct event_item_st* item;
 struct completion* completed = NULL;
+int ret = 0;
 
 	down(&event_list.sem);
 
@@ -82,10 +84,13 @@ struct completion* completed = NULL;
 		}
 	}
 	up(&event_list.sem);
-	if (completed)
-		wait_for_completion(completed);
+	if (completed) {
+		ret = wait_for_completion_interruptible(completed);
+	}
+	return 0;
 }
 
+
 static void event_complete(uint32_t id)
 {
 struct event_item_st* item;
@@ -119,6 +124,23 @@ struct event_item_st* item;
 	return;
 }
 
+static void event_set_idata(uint32_t id, uint32_t data)
+{
+struct event_item_st* item;
+
+	down(&event_list.sem);
+
+	list_for_each_entry(item, &event_list.list, list) {
+		if (id == item->id) {
+			item->ireply = data;
+			break;
+		}
+	}
+	up(&event_list.sem);
+	
+	return;
+}
+
 static void* event_get_data(uint32_t id, size_t *reply_size)
 {
 struct event_item_st* item;
@@ -138,6 +160,24 @@ void* reply = NULL;
 	return reply;
 }
 
+static uint32_t event_get_idata(uint32_t id)
+{
+struct event_item_st* item;
+uint32_t reply = -1;
+
+	down(&event_list.sem);
+
+	list_for_each_entry(item, &event_list.list, list) {
+		if (id == item->id) {
+			reply = item->ireply;
+			break;
+		}
+	}
+	up(&event_list.sem);
+	
+	return reply;
+}
+
 static void event_remove(uint32_t id)
 {
 struct event_item_st* item, *tmp;
@@ -157,22 +197,14 @@ struct event_item_st* item, *tmp;
 }
 
 
-/* attributes (variables): the index in this enum is used as a reference for the type,
- *             userspace application has to indicate the corresponding type
- *             the policy is used for security considerations 
- */
-enum {
-	ATTR_UNSPEC,
-	ATTR_DATA,
-	__ATTR_MAX,
-};
-#define ATTR_MAX (__ATTR_MAX - 1)
-
 /* attribute policy: defines which attribute has which type (e.g int, char * etc)
  * possible values defined in net/netlink.h 
  */
 static struct nla_policy ncr_genl_policy[ATTR_MAX + 1] = {
-	[ATTR_DATA] = { .type = NLA_BINARY },
+	[ATTR_STRUCT_LOAD] = { .type = NLA_BINARY },
+	[ATTR_STRUCT_LOADED] = { .type = NLA_BINARY },
+	[ATTR_STORE_ACK] = { .type = NLA_BINARY },
+	[ATTR_STRUCT_STORE] = { .type = NLA_BINARY },
 };
 
 static atomic_t ncr_event_sr;
@@ -183,31 +215,19 @@ static uint32_t listener_pid = -1;
 static struct genl_family ncr_gnl_family = {
 	.id = GENL_ID_GENERATE,         //genetlink should generate an id
 	.hdrsize = 0,
-	.name = "KEY_STORAGE",        //the name of this family, used by userspace application
+	.name = NCR_NL_STORAGE_NAME,        //the name of this family, used by userspace application
 	.version = VERSION_NR,                   //version number  
 	.maxattr = ATTR_MAX,
 };
 
-/* commands: enumeration of all commands (functions), 
- * used by userspace application to identify command to be ececuted
- */
-enum {
-	CMD_LISTENING,
-	CMD_STORE,
-	CMD_LOAD,
-	CMD_STORE_ACK,
-	CMD_LOADED_DATA,
-	__CMD_MAX,
-};
-#define CMD_MAX (__CMD_MAX - 1)
 
 /* an echo command, receives a message, prints it and sends another message back */
 int _ncr_store(const struct storage_item_st * tostore)
 {
 	struct sk_buff *skb;
 	int ret;
-	uint8_t *reply;
-	size_t size, reply_size;
+	uint32_t reply;
+	size_t size;
 	struct nlattr *attr;
 	void* msg, *msg_head;
 	uint32_t id;
@@ -238,7 +258,7 @@ int _ncr_store(const struct storage_item_st * tostore)
 	}
 
 	/* fill the data */
-	attr = nla_reserve(skb, ATTR_DATA,
+	attr = nla_reserve(skb, ATTR_STRUCT_STORE,
 					sizeof(struct storage_item_st));
 	if (!attr) {
 		err();
@@ -264,13 +284,16 @@ int _ncr_store(const struct storage_item_st * tostore)
 		goto out;
 
 	/* wait for an acknowledgment */
-	event_wait(id);
+	ret = event_wait(id);
+	if (ret) {
+		goto out;
+	}
 
-	reply = event_get_data(id, &reply_size);
-	if (reply_size < 1)
+	reply = event_get_idata(id, &reply_size);
+	if (reply == (uint32_t)-1)
 		BUG();
 
-	if (reply[0] != 0) {
+	if (reply != 0) {
 		/* write failed */
 		ret = -EIO;
 	} else {
@@ -325,7 +348,7 @@ int _ncr_load(struct storage_item_st * toload)
 	}
 
 	/* fill the data */
-	attr = nla_reserve(skb, ATTR_DATA,
+	attr = nla_reserve(skb, ATTR_STRUCT_LOAD,
 					sizeof(struct ncr_gnl_load_cmd_st));
 	if (!attr) {
 		err();
@@ -361,7 +384,10 @@ int _ncr_load(struct storage_item_st * toload)
 		goto out;
 
 	/* wait for an answer */
-	event_wait(id);
+	ret = event_wait(id);
+	if (ret) {
+		goto out;
+	}
 
 	reply = event_get_data(id, &reply_size);
 	if (reply_size != sizeof(struct storage_item_st))
@@ -406,7 +432,7 @@ int ncr_gnl_store_ack(struct sk_buff *skb, struct genl_info *info)
 	/*for each attribute there is an index in info->attrs which points to a nlattr structure
 	 *in this structure the data is given
 	 */
-	na = info->attrs[ATTR_DATA];
+	na = info->attrs[ATTR_STORE_ACK];
 	if (na) {
 		len = nla_len(na);
 		data = (void *)nla_data(na);
@@ -415,17 +441,13 @@ int ncr_gnl_store_ack(struct sk_buff *skb, struct genl_info *info)
 		else {
 			
 			memcpy( &reply, data, sizeof(reply));
-			event_reply = kmalloc(1, GFP_KERNEL);
-			if (event_reply != NULL) {
-				if (reply.reply == 0)
-					event_reply[0] = 0;
-				else event_reply[0] = 1; /* fail */
-				event_set_data(reply.id, event_reply, 1);
-			}
+
+			event_set_idata(reply.id, (uint32_t)reply.reply[0]);
+
 			event_complete(reply.id);
 		}
 	} else
-		printk(KERN_DEBUG"no info->attrs %i\n", ATTR_DATA);
+		printk(KERN_DEBUG"no info->attrs %i\n", ATTR_STORE_ACK);
 
 	return 0;
 }
@@ -444,7 +466,7 @@ int ncr_gnl_loaded_data(struct sk_buff *skb, struct genl_info *info)
 	/*for each attribute there is an index in info->attrs which points to a nlattr structure
 	 *in this structure the data is given
 	 */
-	na = info->attrs[ATTR_DATA];
+	na = info->attrs[ATTR_STRUCT_LOADED];
 	if (na) {
 		len = nla_len(na);
 		data = (void *)nla_data(na);
@@ -461,7 +483,7 @@ int ncr_gnl_loaded_data(struct sk_buff *skb, struct genl_info *info)
 			event_complete(reply.id);
 		}
 	} else
-		printk(KERN_DEBUG"no info->attrs %i\n", ATTR_DATA);
+		printk(KERN_DEBUG"no info->attrs %i\n", ATTR_STRUCT_LOADED);
 
 	return 0;
 }
diff --git a/ncr-storage-low.h b/ncr-storage-low.h
index 2578ac9bf7b..814b0df2893 100644
--- a/ncr-storage-low.h
+++ b/ncr-storage-low.h
@@ -1,6 +1,60 @@
 #ifndef _STORAGE_LOW
 #define _STORAGE_LOW
 
+#include <ncr.h>
+
+#define NCR_NL_STORAGE_NAME "KEY_STORAGE"
+
+#define NCR_NL_STORAGE_VERSION 1
+
+/* commands: enumeration of all commands (functions), 
+ * used by userspace application to identify command to be ececuted
+ */
+enum {
+	CMD_LISTENING, /* sent by server */
+	CMD_STORE, /* sent by kernel */
+	CMD_LOAD, /* sent by kernel */
+	CMD_STORE_ACK, /* sent by server */
+	CMD_LOADED_DATA, /* sent by server */
+	__CMD_MAX,
+};
+#define CMD_MAX (__CMD_MAX - 1)
+
+/* attributes (variables): the index in this enum is used as a reference for the type,
+ *             userspace application has to indicate the corresponding type
+ *             the policy is used for security considerations 
+ */
+enum {
+	ATTR_UNSPEC,
+	ATTR_STRUCT_LOAD,
+	ATTR_STRUCT_LOADED,
+	ATTR_STRUCT_STORE,
+	ATTR_STORE_ACK, /* u8*/
+	__ATTR_MAX,
+};
+#define ATTR_MAX (__ATTR_MAX - 1)
+
+#define MAX_DATA_SIZE 10*1024
+#define MAX_RAW_KEY_SIZE 4096
+
+struct storage_item_st {
+	/* metadata */
+	uint8_t label[MAX_LABEL_SIZE];
+	uint32_t owner;
+	uint32_t group;
+	mode_t mode;
+
+	uint16_t algorithm;
+	uint8_t type;
+
+	uint8_t key_id[MAX_KEY_ID_SIZE];
+	uint8_t key_id_size;
+
+	/* data */
+	uint8_t raw_key[MAX_RAW_KEY_SIZE];
+	uint16_t raw_key_size;
+} __attribute__ ((__packed__));
+
 struct ncr_gnl_load_cmd_st {
 	uint8_t label[MAX_LABEL_SIZE];
 	uint32_t owner;
diff --git a/ncr-storage.h b/ncr-storage.h
index e1016e82b1a..9384b6ef6f5 100644
--- a/ncr-storage.h
+++ b/ncr-storage.h
@@ -1,25 +1,7 @@
 #ifndef NCR_STORAGE_H
 # define NCR_STORAGE_H
 
-#define MAX_RAW_KEY_SIZE 4096
-
-struct storage_item_st {
-	/* metadata */
-	uint8_t label[MAX_LABEL_SIZE];
-	uint32_t owner;
-	uint32_t group;
-	mode_t mode;
-
-	uint16_t algorithm;
-	uint8_t type;
-
-	uint8_t key_id[MAX_KEY_ID_SIZE];
-	uint8_t key_id_size;
-
-	/* data */
-	uint8_t raw_key[MAX_RAW_KEY_SIZE];
-	uint16_t raw_key_size;
-} __attribute__ ((__packed__));
+#include "ncr-storage-low.h" /* for struct storage_item_st */
 
 int ncr_storage_store(struct list_sem_st* key_lst, void __user* arg);
 int ncr_storage_load(struct list_sem_st* key_lst, void __user* arg);
diff --git a/userspace/ncr-server/Makefile b/userspace/ncr-server/Makefile
new file mode 100644
index 00000000000..ee46dd6ae46
--- /dev/null
+++ b/userspace/ncr-server/Makefile
@@ -0,0 +1,7 @@
+all: ncr-server
+
+CFLAGS=-O2 -Wall -g -I.. -I.
+CC=gcc
+
+ncr-server: ncr-server.c ncr-server.h
+	$(CC) $(CFLAGS) ncr-server.c -o ncr-server 
diff --git a/userspace/ncr-server/list.h b/userspace/ncr-server/list.h
new file mode 100644
index 00000000000..3a7688566a6
--- /dev/null
+++ b/userspace/ncr-server/list.h
@@ -0,0 +1,244 @@
+#ifndef __LIST_H
+#define __LIST_H
+
+/* This file is from Linux Kernel (include/linux/list.h) 
+ * and modified by simply removing hardware prefetching of list items. 
+ * Here by copyright, credits attributed to wherever they belong.
+ * Kulesh Shanmugasundaram (kulesh [squiggly] isis.poly.edu)
+ */
+
+/*
+ * Simple doubly linked list implementation.
+ *
+ * Some of the internal functions ("__xxx") are useful when
+ * manipulating whole lists rather than single entries, as
+ * sometimes we already know the next/prev entries and we can
+ * generate better code by using them directly rather than
+ * using the generic single-entry routines.
+ */
+
+struct list_head {
+	struct list_head *next, *prev;
+};
+
+#define LIST_HEAD_INIT(name) { &(name), &(name) }
+
+#define LIST_HEAD(name) \
+	struct list_head name = LIST_HEAD_INIT(name)
+
+#define INIT_LIST_HEAD(ptr) do { \
+	(ptr)->next = (ptr); (ptr)->prev = (ptr); \
+} while (0)
+
+/*
+ * Insert a new entry between two known consecutive entries. 
+ *
+ * This is only for internal list manipulation where we know
+ * the prev/next entries already!
+ */
+static inline void __list_add(struct list_head *new,
+			      struct list_head *prev,
+			      struct list_head *next)
+{
+	next->prev = new;
+	new->next = next;
+	new->prev = prev;
+	prev->next = new;
+}
+
+/**
+ * list_add - add a new entry
+ * @new: new entry to be added
+ * @head: list head to add it after
+ *
+ * Insert a new entry after the specified head.
+ * This is good for implementing stacks.
+ */
+static inline void list_add(struct list_head *new, struct list_head *head)
+{
+	__list_add(new, head, head->next);
+}
+
+/**
+ * list_add_tail - add a new entry
+ * @new: new entry to be added
+ * @head: list head to add it before
+ *
+ * Insert a new entry before the specified head.
+ * This is useful for implementing queues.
+ */
+static inline void list_add_tail(struct list_head *new, struct list_head *head)
+{
+	__list_add(new, head->prev, head);
+}
+
+/*
+ * Delete a list entry by making the prev/next entries
+ * point to each other.
+ *
+ * This is only for internal list manipulation where we know
+ * the prev/next entries already!
+ */
+static inline void __list_del(struct list_head *prev, struct list_head *next)
+{
+	next->prev = prev;
+	prev->next = next;
+}
+
+/**
+ * list_del - deletes entry from list.
+ * @entry: the element to delete from the list.
+ * Note: list_empty on entry does not return true after this, the entry is in an undefined state.
+ */
+static inline void list_del(struct list_head *entry)
+{
+	__list_del(entry->prev, entry->next);
+	entry->next = (void *) 0;
+	entry->prev = (void *) 0;
+}
+
+/**
+ * list_del_init - deletes entry from list and reinitialize it.
+ * @entry: the element to delete from the list.
+ */
+static inline void list_del_init(struct list_head *entry)
+{
+	__list_del(entry->prev, entry->next);
+	INIT_LIST_HEAD(entry); 
+}
+
+/**
+ * list_move - delete from one list and add as another's head
+ * @list: the entry to move
+ * @head: the head that will precede our entry
+ */
+static inline void list_move(struct list_head *list, struct list_head *head)
+{
+        __list_del(list->prev, list->next);
+        list_add(list, head);
+}
+
+/**
+ * list_move_tail - delete from one list and add as another's tail
+ * @list: the entry to move
+ * @head: the head that will follow our entry
+ */
+static inline void list_move_tail(struct list_head *list,
+				  struct list_head *head)
+{
+        __list_del(list->prev, list->next);
+        list_add_tail(list, head);
+}
+
+/**
+ * list_empty - tests whether a list is empty
+ * @head: the list to test.
+ */
+static inline int list_empty(struct list_head *head)
+{
+	return head->next == head;
+}
+
+static inline void __list_splice(struct list_head *list,
+				 struct list_head *head)
+{
+	struct list_head *first = list->next;
+	struct list_head *last = list->prev;
+	struct list_head *at = head->next;
+
+	first->prev = head;
+	head->next = first;
+
+	last->next = at;
+	at->prev = last;
+}
+
+/**
+ * list_splice - join two lists
+ * @list: the new list to add.
+ * @head: the place to add it in the first list.
+ */
+static inline void list_splice(struct list_head *list, struct list_head *head)
+{
+	if (!list_empty(list))
+		__list_splice(list, head);
+}
+
+/**
+ * list_splice_init - join two lists and reinitialise the emptied list.
+ * @list: the new list to add.
+ * @head: the place to add it in the first list.
+ *
+ * The list at @list is reinitialised
+ */
+static inline void list_splice_init(struct list_head *list,
+				    struct list_head *head)
+{
+	if (!list_empty(list)) {
+		__list_splice(list, head);
+		INIT_LIST_HEAD(list);
+	}
+}
+
+/**
+ * list_entry - get the struct for this entry
+ * @ptr:	the &struct list_head pointer.
+ * @type:	the type of the struct this is embedded in.
+ * @member:	the name of the list_struct within the struct.
+ */
+#define list_entry(ptr, type, member) \
+	((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
+
+/**
+ * list_for_each	-	iterate over a list
+ * @pos:	the &struct list_head to use as a loop counter.
+ * @head:	the head for your list.
+ */
+#define list_for_each(pos, head) \
+	for (pos = (head)->next; pos != (head); \
+        	pos = pos->next)
+/**
+ * list_for_each_prev	-	iterate over a list backwards
+ * @pos:	the &struct list_head to use as a loop counter.
+ * @head:	the head for your list.
+ */
+#define list_for_each_prev(pos, head) \
+	for (pos = (head)->prev; pos != (head); \
+        	pos = pos->prev)
+        	
+/**
+ * list_for_each_safe	-	iterate over a list safe against removal of list entry
+ * @pos:	the &struct list_head to use as a loop counter.
+ * @n:		another &struct list_head to use as temporary storage
+ * @head:	the head for your list.
+ */
+#define list_for_each_safe(pos, n, head) \
+	for (pos = (head)->next, n = pos->next; pos != (head); \
+		pos = n, n = pos->next)
+
+/**
+ * list_for_each_entry	-	iterate over list of given type
+ * @pos:	the type * to use as a loop counter.
+ * @head:	the head for your list.
+ * @member:	the name of the list_struct within the struct.
+ */
+#define list_for_each_entry(pos, head, member)				\
+	for (pos = list_entry((head)->next, typeof(*pos), member);	\
+	     &pos->member != (head); 					\
+	     pos = list_entry(pos->member.next, typeof(*pos), member))
+
+/**
+ * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
+ * @pos:	the type * to use as a loop counter.
+ * @n:		another type * to use as temporary storage
+ * @head:	the head for your list.
+ * @member:	the name of the list_struct within the struct.
+ */
+#define list_for_each_entry_safe(pos, n, head, member)			\
+	for (pos = list_entry((head)->next, typeof(*pos), member),	\
+		n = list_entry(pos->member.next, typeof(*pos), member);	\
+	     &pos->member != (head); 					\
+	     pos = n, n = list_entry(n->member.next, typeof(*n), member))
+
+
+#endif
diff --git a/userspace/ncr-server/ncr-server.c b/userspace/ncr-server/ncr-server.c
new file mode 100644
index 00000000000..3b3c72ad145
--- /dev/null
+++ b/userspace/ncr-server/ncr-server.c
@@ -0,0 +1,210 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <netlink/netlink.h>
+#include <netlink/socket.h>
+#include <netlink/genl/genl.h>
+#include <netlink/genl/ctrl.h>
+#include "../ncr-storage-low.h"
+#include "ncr-server.h"
+#include <list.h>
+
+static int _notify_listening(struct nl_sock * sock);
+
+static struct nla_policy def_policy[ATTR_MAX+1] =
+{
+     [ATTR_STRUCT_STORE] = { .type = NLA_UNSPEC,
+                          .minlen = sizeof(struct storage_item_st) },
+     [ATTR_STRUCT_LOAD] = { .type = NLA_UNSPEC,
+                          .minlen = sizeof(struct ncr_gnl_load_cmd_st) },
+};
+
+static struct actions {
+	list_head list;
+	int cmd; /* CMD_* */
+	union {
+		struct storage_item_st tostore;
+		struct ncr_gnl_load_cmd_st toload;
+	} data;
+} todo;
+
+static int add_store_cmd(struct storage_item_st* tostore)
+{
+	struct actions* item;
+
+	item = malloc(sizeof(*item));
+	if (item == NULL) {
+		err();
+		return -ERR_MEM;
+	}
+	item->cmd = CMD_STORE;
+	memcpy(item->data.tostore, tostore, sizeof(item->data.tostore));
+
+	list_add(item, &todo.list);
+	return 0;
+}
+
+static int add_load_cmd(struct ncr_gnl_load_cmd_st* toload)
+{
+	struct actions* item;
+
+	item = malloc(sizeof(*item));
+	if (item == NULL) {
+		err();
+		return -ERR_MEM;
+	}
+	item->cmd = CMD_LOAD;
+	memcpy(item->data.toload, toload, sizeof(item->data.toload));
+
+	list_add(item, &todo.list);
+	return 0;
+}
+
+static int msg_cb(struct nl_msg *msg, void *arg)
+{
+	struct nlmsghdr *nlh = nlmsg_hdr(msg);
+	struct nlattr *attrs[ATTR_MAX+1];
+
+		// Validate message and parse attributes
+	genlmsg_parse(nlh, 0, attrs, ATTR_MAX, def_policy);
+
+	if (attrs[ATTR_STRUCT_STORE]) {
+		struct storage_item_st *item = nla_get(attrs[ATTR_STRUCT_STORE]);
+		fprintf(stderr, "asked to store: %s\n", item->label);
+
+		add_store_cmd(item);
+	}
+
+	if (attrs[ATTR_STRUCT_LOAD]) {
+		struct ncr_gnl_load_cmd_st *load = nla_get(attrs[ATTR_STRUCT_LOAD]);
+		fprintf(stderr, "asked to load: %s\n", load->label);
+
+		add_load_cmd(item);
+	}
+
+	return NL_STOP;
+}
+
+
+int main()
+{
+struct nl_sock *sock;
+int ret;
+
+	memset(&todo, 0, sizeof(todo));
+	LIST_HEAD_INIT(&todo.list);
+
+	// Allocate a new netlink socket
+	sock = nl_socket_alloc();
+	if (sock == NULL) {
+		err();
+		return ERR_CONNECT;
+	}
+
+	// Connect to generic netlink socket on kernel side
+	ret = genl_connect(sock);
+	if (ret < 0) {
+		err();
+		return ERR_CONNECT;
+	}
+	
+	// Ask kernel to resolve family name to family id
+	family = genl_ctrl_resolve(sock, NCR_NL_STORAGE_NAME);
+	if (family < 0) {
+		err();
+		return ERR_CONNECT;
+	}
+
+	/* set our callback to receive messages */
+	ret = nl_socket_modify_cb(sock, NL_CB_VALID, NL_CB_CUSTOM, msg_cb, NULL);
+	if (ret < 0) {
+		fprintf(stderr, "Could not set listening callback.\n");
+		exit(1);
+	}
+
+	ret = _notify_listening(sock);
+	if (ret < 0) {
+		fprintf(stderr, "Could not notify kernel subsystem.\n");
+		exit(1);
+	}
+
+	// Wait for the answer and receive it
+	do {
+		ret = nl_recvmsgs_default(sock);
+
+		/* we have to consume the todo list */
+		if (ret == 0) {
+			//store_if_needed(sock);
+			//load_if_needed(sock);
+		}
+	} while (ret == 0);
+	fprintf(stderr, "received: %d\n", ret);
+
+}
+
+static int _notify_listening(struct nl_sock * sock)
+{
+struct nl_msg *msg;
+int family, ret;
+
+	// Construct a generic netlink by allocating a new message, fill in
+	// the header and append a simple integer attribute.
+	msg = nlmsg_alloc();
+	if (msg == NULL) {
+		err();
+		return ERR_MEM;
+	}
+
+	genlmsg_put(msg, NL_AUTO_PID, NL_AUTO_SEQ, family, 0, NLM_F_REQUEST,
+	 CMD_LISTENING, NCR_NL_STORAGE_VERSION);
+
+	// Send message over netlink socket
+	ret = nl_send_auto_complete(sock, msg);
+	nlmsg_free(msg);
+
+	if (ret < 0) {
+		err();
+		return ERR_CONNECT;
+	}
+
+	return 0;
+}
+
+
+static int send_store_ack(struct nl_sock * sock, uint8_t val)
+{
+struct nl_msg *msg;
+int family, ret;
+
+	// Construct a generic netlink by allocating a new message, fill in
+	// the header and append a simple integer attribute.
+	msg = nlmsg_alloc();
+	if (msg == NULL) {
+		err();
+		return ERR_MEM;
+	}
+
+	genlmsg_put(msg, NL_AUTO_PID, NL_AUTO_SEQ, family, 0, NLM_F_REQUEST,
+	 CMD_STORE_ACK, NCR_NL_STORAGE_VERSION);
+
+	ret = nla_put_u8(msg, ATTR_STORE_ACK, val);
+	if (ret < 0) {
+		err();
+		ret = ERR_SEND;
+		goto fail;
+	}
+
+	// Send message over netlink socket
+	ret = nl_send_auto_complete(sock, msg);
+	nlmsg_free(msg);
+
+	if (ret < 0) {
+		err();
+		return ERR_SEND;
+	}
+
+	return 0;
+fail:
+	nlmsg_free(msg);
+	return ret;
+}
diff --git a/userspace/ncr-server/ncr-server.h b/userspace/ncr-server/ncr-server.h
new file mode 100644
index 00000000000..dae0757ed09
--- /dev/null
+++ b/userspace/ncr-server/ncr-server.h
@@ -0,0 +1,11 @@
+#ifndef NCR_SERVER_H
+#define NCR_SERVER_H
+
+#define err() fprintf(stderr, "Error in %s:%d\n", __FILE__, __LINE__);
+
+#define ERR_CONNECT -1
+#define ERR_MEM -2
+#define ERR_SEND -3
+
+
+#endif