/*
   *	IEEE 802.1D Generic Attribute Registration Protocol (GARP)
   *
   *	Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
   *
   *	This program is free software; you can redistribute it and/or
   *	modify it under the terms of the GNU General Public License
   *	version 2 as published by the Free Software Foundation.
   */
  #include <linux/kernel.h>
  #include <linux/timer.h>
  #include <linux/skbuff.h>
  #include <linux/netdevice.h>
  #include <linux/etherdevice.h>
  #include <linux/rtnetlink.h>
  #include <linux/llc.h>
  #include <linux/slab.h>
  #include <linux/module.h>
  #include <net/llc.h>
  #include <net/llc_pdu.h>
  #include <net/garp.h>
  #include <asm/unaligned.h>
  
  static unsigned int garp_join_time __read_mostly = 200;
  module_param(garp_join_time, uint, 0644);
  MODULE_PARM_DESC(garp_join_time, "Join time in ms (default 200ms)");
  MODULE_LICENSE("GPL");
  
  static const struct garp_state_trans {
  	u8	state;
  	u8	action;
  } garp_applicant_state_table[GARP_APPLICANT_MAX + 1][GARP_EVENT_MAX + 1] = {
  	[GARP_APPLICANT_VA] = {
  		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_AA,
  						    .action = GARP_ACTION_S_JOIN_IN },
  		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_AA },
  		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VA },
  		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VA },
  		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VA },
  		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_INVALID },
  		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_LA },
  	},
  	[GARP_APPLICANT_AA] = {
  		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_QA,
  						    .action = GARP_ACTION_S_JOIN_IN },
  		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_QA },
  		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VA },
  		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VA },
  		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VA },
  		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_INVALID },
  		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_LA },
  	},
  	[GARP_APPLICANT_QA] = {
  		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_INVALID },
  		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_QA },
  		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VA },
  		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VA },
  		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_INVALID },
  		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_LA },
  	},
  	[GARP_APPLICANT_LA] = {
  		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_VO,
  						    .action = GARP_ACTION_S_LEAVE_EMPTY },
  		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_LA },
  		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_LA },
  		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_LA },
  		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_VA },
  		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_INVALID },
  	},
  	[GARP_APPLICANT_VP] = {
  		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_AA,
  						    .action = GARP_ACTION_S_JOIN_IN },
  		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_AP },
  		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_INVALID },
  		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_VO },
  	},
  	[GARP_APPLICANT_AP] = {
  		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_QA,
  						    .action = GARP_ACTION_S_JOIN_IN },
  		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_QP },
  		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_INVALID },
  		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_AO },
  	},
  	[GARP_APPLICANT_QP] = {
  		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_INVALID },
  		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_QP },
  		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_INVALID },
  		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_QO },
  	},
  	[GARP_APPLICANT_VO] = {
  		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_INVALID },
  		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_AO },
  		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_VP },
  		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_INVALID },
  	},
  	[GARP_APPLICANT_AO] = {
  		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_INVALID },
  		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_QO },
  		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_AP },
  		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_INVALID },
  	},
  	[GARP_APPLICANT_QO] = {
  		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_INVALID },
  		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_QO },
  		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VO },
  		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_QP },
  		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_INVALID },
  	},
  };
  
  static int garp_attr_cmp(const struct garp_attr *attr,
  			 const void *data, u8 len, u8 type)
  {
  	if (attr->type != type)
  		return attr->type - type;
  	if (attr->dlen != len)
  		return attr->dlen - len;
  	return memcmp(attr->data, data, len);
  }
  
  static struct garp_attr *garp_attr_lookup(const struct garp_applicant *app,
  					  const void *data, u8 len, u8 type)
  {
  	struct rb_node *parent = app->gid.rb_node;
  	struct garp_attr *attr;
  	int d;
  
  	while (parent) {
  		attr = rb_entry(parent, struct garp_attr, node);
  		d = garp_attr_cmp(attr, data, len, type);
  		if (d > 0)
  			parent = parent->rb_left;
  		else if (d < 0)
  			parent = parent->rb_right;
  		else
  			return attr;
  	}
  	return NULL;
  }
  
  static struct garp_attr *garp_attr_create(struct garp_applicant *app,
  					  const void *data, u8 len, u8 type)
  {
  	struct rb_node *parent = NULL, **p = &app->gid.rb_node;
  	struct garp_attr *attr;
  	int d;
  
  	while (*p) {
  		parent = *p;
  		attr = rb_entry(parent, struct garp_attr, node);
  		d = garp_attr_cmp(attr, data, len, type);
  		if (d > 0)
  			p = &parent->rb_left;
  		else if (d < 0)
  			p = &parent->rb_right;
  		else {
  			/* The attribute already exists; re-use it. */
  			return attr;
  		}
  	}
  	attr = kmalloc(sizeof(*attr) + len, GFP_ATOMIC);
  	if (!attr)
  		return attr;
  	attr->state = GARP_APPLICANT_VO;
  	attr->type  = type;
  	attr->dlen  = len;
  	memcpy(attr->data, data, len);
  
  	rb_link_node(&attr->node, parent, p);
  	rb_insert_color(&attr->node, &app->gid);
  	return attr;
  }
  
  static void garp_attr_destroy(struct garp_applicant *app, struct garp_attr *attr)
  {
  	rb_erase(&attr->node, &app->gid);
  	kfree(attr);
  }
  
  static int garp_pdu_init(struct garp_applicant *app)
  {
  	struct sk_buff *skb;
  	struct garp_pdu_hdr *gp;
  
  #define LLC_RESERVE	sizeof(struct llc_pdu_un)
  	skb = alloc_skb(app->dev->mtu + LL_RESERVED_SPACE(app->dev),
  			GFP_ATOMIC);
  	if (!skb)
  		return -ENOMEM;
  
  	skb->dev = app->dev;
  	skb->protocol = htons(ETH_P_802_2);
  	skb_reserve(skb, LL_RESERVED_SPACE(app->dev) + LLC_RESERVE);
  
  	gp = (struct garp_pdu_hdr *)__skb_put(skb, sizeof(*gp));
  	put_unaligned(htons(GARP_PROTOCOL_ID), &gp->protocol);
  
  	app->pdu = skb;
  	return 0;
  }
  
  static int garp_pdu_append_end_mark(struct garp_applicant *app)
  {
  	if (skb_tailroom(app->pdu) < sizeof(u8))
  		return -1;
  	*(u8 *)__skb_put(app->pdu, sizeof(u8)) = GARP_END_MARK;
  	return 0;
  }
  
  static void garp_pdu_queue(struct garp_applicant *app)
  {
  	if (!app->pdu)
  		return;
  
  	garp_pdu_append_end_mark(app);
  	garp_pdu_append_end_mark(app);
  
  	llc_pdu_header_init(app->pdu, LLC_PDU_TYPE_U, LLC_SAP_BSPAN,
  			    LLC_SAP_BSPAN, LLC_PDU_CMD);
  	llc_pdu_init_as_ui_cmd(app->pdu);
  	llc_mac_hdr_init(app->pdu, app->dev->dev_addr,
  			 app->app->proto.group_address);
  
  	skb_queue_tail(&app->queue, app->pdu);
  	app->pdu = NULL;
  }
  
  static void garp_queue_xmit(struct garp_applicant *app)
  {
  	struct sk_buff *skb;
  
  	while ((skb = skb_dequeue(&app->queue)))
  		dev_queue_xmit(skb);
  }
  
  static int garp_pdu_append_msg(struct garp_applicant *app, u8 attrtype)
  {
  	struct garp_msg_hdr *gm;
  
  	if (skb_tailroom(app->pdu) < sizeof(*gm))
  		return -1;
  	gm = (struct garp_msg_hdr *)__skb_put(app->pdu, sizeof(*gm));
  	gm->attrtype = attrtype;
  	garp_cb(app->pdu)->cur_type = attrtype;
  	return 0;
  }
  
  static int garp_pdu_append_attr(struct garp_applicant *app,
  				const struct garp_attr *attr,
  				enum garp_attr_event event)
  {
  	struct garp_attr_hdr *ga;
  	unsigned int len;
  	int err;
  again:
  	if (!app->pdu) {
  		err = garp_pdu_init(app);
  		if (err < 0)
  			return err;
  	}
  
  	if (garp_cb(app->pdu)->cur_type != attr->type) {
  		if (garp_cb(app->pdu)->cur_type &&
  		    garp_pdu_append_end_mark(app) < 0)
  			goto queue;
  		if (garp_pdu_append_msg(app, attr->type) < 0)
  			goto queue;
  	}
  
  	len = sizeof(*ga) + attr->dlen;
  	if (skb_tailroom(app->pdu) < len)
  		goto queue;
  	ga = (struct garp_attr_hdr *)__skb_put(app->pdu, len);
  	ga->len   = len;
  	ga->event = event;
  	memcpy(ga->data, attr->data, attr->dlen);
  	return 0;
  
  queue:
  	garp_pdu_queue(app);
  	goto again;
  }
  
  static void garp_attr_event(struct garp_applicant *app,
  			    struct garp_attr *attr, enum garp_event event)
  {
  	enum garp_applicant_state state;
  
  	state = garp_applicant_state_table[attr->state][event].state;
  	if (state == GARP_APPLICANT_INVALID)
  		return;
  
  	switch (garp_applicant_state_table[attr->state][event].action) {
  	case GARP_ACTION_NONE:
  		break;
  	case GARP_ACTION_S_JOIN_IN:
  		/* When appending the attribute fails, don't update state in
  		 * order to retry on next TRANSMIT_PDU event. */
  		if (garp_pdu_append_attr(app, attr, GARP_JOIN_IN) < 0)
  			return;
  		break;
  	case GARP_ACTION_S_LEAVE_EMPTY:
  		garp_pdu_append_attr(app, attr, GARP_LEAVE_EMPTY);
  		/* As a pure applicant, sending a leave message implies that
  		 * the attribute was unregistered and can be destroyed. */
  		garp_attr_destroy(app, attr);
  		return;
  	default:
  		WARN_ON(1);
  	}
  
  	attr->state = state;
  }
  
  int garp_request_join(const struct net_device *dev,
  		      const struct garp_application *appl,
  		      const void *data, u8 len, u8 type)
  {
  	struct garp_port *port = rtnl_dereference(dev->garp_port);
  	struct garp_applicant *app = rtnl_dereference(port->applicants[appl->type]);
  	struct garp_attr *attr;
  
  	spin_lock_bh(&app->lock);
  	attr = garp_attr_create(app, data, len, type);
  	if (!attr) {
  		spin_unlock_bh(&app->lock);
  		return -ENOMEM;
  	}
  	garp_attr_event(app, attr, GARP_EVENT_REQ_JOIN);
  	spin_unlock_bh(&app->lock);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(garp_request_join);
  
  void garp_request_leave(const struct net_device *dev,
  			const struct garp_application *appl,
  			const void *data, u8 len, u8 type)
  {
  	struct garp_port *port = rtnl_dereference(dev->garp_port);
  	struct garp_applicant *app = rtnl_dereference(port->applicants[appl->type]);
  	struct garp_attr *attr;
  
  	spin_lock_bh(&app->lock);
  	attr = garp_attr_lookup(app, data, len, type);
  	if (!attr) {
  		spin_unlock_bh(&app->lock);
  		return;
  	}
  	garp_attr_event(app, attr, GARP_EVENT_REQ_LEAVE);
  	spin_unlock_bh(&app->lock);
  }
  EXPORT_SYMBOL_GPL(garp_request_leave);
  
  static void garp_gid_event(struct garp_applicant *app, enum garp_event event)
  {
  	struct rb_node *node, *next;
  	struct garp_attr *attr;
  
  	for (node = rb_first(&app->gid);
  	     next = node ? rb_next(node) : NULL, node != NULL;
  	     node = next) {
  		attr = rb_entry(node, struct garp_attr, node);
  		garp_attr_event(app, attr, event);
  	}
  }
  
  static void garp_join_timer_arm(struct garp_applicant *app)
  {
  	unsigned long delay;
  
  	delay = (u64)msecs_to_jiffies(garp_join_time) * prandom_u32() >> 32;
  	mod_timer(&app->join_timer, jiffies + delay);
  }
  
  static void garp_join_timer(unsigned long data)
  {
  	struct garp_applicant *app = (struct garp_applicant *)data;
  
  	spin_lock(&app->lock);
  	garp_gid_event(app, GARP_EVENT_TRANSMIT_PDU);
  	garp_pdu_queue(app);
  	spin_unlock(&app->lock);
  
  	garp_queue_xmit(app);
  	garp_join_timer_arm(app);
  }
  
  static int garp_pdu_parse_end_mark(struct sk_buff *skb)
  {
  	if (!pskb_may_pull(skb, sizeof(u8)))
  		return -1;
  	if (*skb->data == GARP_END_MARK) {
  		skb_pull(skb, sizeof(u8));
  		return -1;
  	}
  	return 0;
  }
  
  static int garp_pdu_parse_attr(struct garp_applicant *app, struct sk_buff *skb,
  			       u8 attrtype)
  {
  	const struct garp_attr_hdr *ga;
  	struct garp_attr *attr;
  	enum garp_event event;
  	unsigned int dlen;
  
  	if (!pskb_may_pull(skb, sizeof(*ga)))
  		return -1;
  	ga = (struct garp_attr_hdr *)skb->data;
  	if (ga->len < sizeof(*ga))
  		return -1;
  
  	if (!pskb_may_pull(skb, ga->len))
  		return -1;
  	skb_pull(skb, ga->len);
  	dlen = sizeof(*ga) - ga->len;
  
  	if (attrtype > app->app->maxattr)
  		return 0;
  
  	switch (ga->event) {
  	case GARP_LEAVE_ALL:
  		if (dlen != 0)
  			return -1;
  		garp_gid_event(app, GARP_EVENT_R_LEAVE_EMPTY);
  		return 0;
  	case GARP_JOIN_EMPTY:
  		event = GARP_EVENT_R_JOIN_EMPTY;
  		break;
  	case GARP_JOIN_IN:
  		event = GARP_EVENT_R_JOIN_IN;
  		break;
  	case GARP_LEAVE_EMPTY:
  		event = GARP_EVENT_R_LEAVE_EMPTY;
  		break;
  	case GARP_EMPTY:
  		event = GARP_EVENT_R_EMPTY;
  		break;
  	default:
  		return 0;
  	}
  
  	if (dlen == 0)
  		return -1;
  	attr = garp_attr_lookup(app, ga->data, dlen, attrtype);
  	if (attr == NULL)
  		return 0;
  	garp_attr_event(app, attr, event);
  	return 0;
  }
  
  static int garp_pdu_parse_msg(struct garp_applicant *app, struct sk_buff *skb)
  {
  	const struct garp_msg_hdr *gm;
  
  	if (!pskb_may_pull(skb, sizeof(*gm)))
  		return -1;
  	gm = (struct garp_msg_hdr *)skb->data;
  	if (gm->attrtype == 0)
  		return -1;
  	skb_pull(skb, sizeof(*gm));
  
  	while (skb->len > 0) {
  		if (garp_pdu_parse_attr(app, skb, gm->attrtype) < 0)
  			return -1;
  		if (garp_pdu_parse_end_mark(skb) < 0)
  			break;
  	}
  	return 0;
  }
  
  static void garp_pdu_rcv(const struct stp_proto *proto, struct sk_buff *skb,
  			 struct net_device *dev)
  {
  	struct garp_application *appl = proto->data;
  	struct garp_port *port;
  	struct garp_applicant *app;
  	const struct garp_pdu_hdr *gp;
  
  	port = rcu_dereference(dev->garp_port);
  	if (!port)
  		goto err;
  	app = rcu_dereference(port->applicants[appl->type]);
  	if (!app)
  		goto err;
  
  	if (!pskb_may_pull(skb, sizeof(*gp)))
  		goto err;
  	gp = (struct garp_pdu_hdr *)skb->data;
  	if (get_unaligned(&gp->protocol) != htons(GARP_PROTOCOL_ID))
  		goto err;
  	skb_pull(skb, sizeof(*gp));
  
  	spin_lock(&app->lock);
  	while (skb->len > 0) {
  		if (garp_pdu_parse_msg(app, skb) < 0)
  			break;
  		if (garp_pdu_parse_end_mark(skb) < 0)
  			break;
  	}
  	spin_unlock(&app->lock);
  err:
  	kfree_skb(skb);
  }
  
  static int garp_init_port(struct net_device *dev)
  {
  	struct garp_port *port;
  
  	port = kzalloc(sizeof(*port), GFP_KERNEL);
  	if (!port)
  		return -ENOMEM;
  	rcu_assign_pointer(dev->garp_port, port);
  	return 0;
  }
  
  static void garp_release_port(struct net_device *dev)
  {
  	struct garp_port *port = rtnl_dereference(dev->garp_port);
  	unsigned int i;
  
  	for (i = 0; i <= GARP_APPLICATION_MAX; i++) {
  		if (rtnl_dereference(port->applicants[i]))
  			return;
  	}
  	RCU_INIT_POINTER(dev->garp_port, NULL);
  	kfree_rcu(port, rcu);
  }
  
  int garp_init_applicant(struct net_device *dev, struct garp_application *appl)
  {
  	struct garp_applicant *app;
  	int err;
  
  	ASSERT_RTNL();
  
  	if (!rtnl_dereference(dev->garp_port)) {
  		err = garp_init_port(dev);
  		if (err < 0)
  			goto err1;
  	}
  
  	err = -ENOMEM;
  	app = kzalloc(sizeof(*app), GFP_KERNEL);
  	if (!app)
  		goto err2;
  
  	err = dev_mc_add(dev, appl->proto.group_address);
  	if (err < 0)
  		goto err3;
  
  	app->dev = dev;
  	app->app = appl;
  	app->gid = RB_ROOT;
  	spin_lock_init(&app->lock);
  	skb_queue_head_init(&app->queue);
  	rcu_assign_pointer(dev->garp_port->applicants[appl->type], app);
  	setup_timer(&app->join_timer, garp_join_timer, (unsigned long)app);
  	garp_join_timer_arm(app);
  	return 0;
  
  err3:
  	kfree(app);
  err2:
  	garp_release_port(dev);
  err1:
  	return err;
  }
  EXPORT_SYMBOL_GPL(garp_init_applicant);
  
  void garp_uninit_applicant(struct net_device *dev, struct garp_application *appl)
  {
  	struct garp_port *port = rtnl_dereference(dev->garp_port);
  	struct garp_applicant *app = rtnl_dereference(port->applicants[appl->type]);
  
  	ASSERT_RTNL();
  
  	RCU_INIT_POINTER(port->applicants[appl->type], NULL);
  
  	/* Delete timer and generate a final TRANSMIT_PDU event to flush out
  	 * all pending messages before the applicant is gone. */
  	del_timer_sync(&app->join_timer);
  
  	spin_lock_bh(&app->lock);
  	garp_gid_event(app, GARP_EVENT_TRANSMIT_PDU);
  	garp_pdu_queue(app);
  	spin_unlock_bh(&app->lock);
  
  	garp_queue_xmit(app);
  
  	dev_mc_del(dev, appl->proto.group_address);
  	kfree_rcu(app, rcu);
  	garp_release_port(dev);
  }
  EXPORT_SYMBOL_GPL(garp_uninit_applicant);
  
  int garp_register_application(struct garp_application *appl)
  {
  	appl->proto.rcv = garp_pdu_rcv;
  	appl->proto.data = appl;
  	return stp_proto_register(&appl->proto);
  }
  EXPORT_SYMBOL_GPL(garp_register_application);
  
  void garp_unregister_application(struct garp_application *appl)
  {
  	stp_proto_unregister(&appl->proto);
  }
  EXPORT_SYMBOL_GPL(garp_unregister_application);