/* Structure dynamic extension infrastructure
   * Copyright (C) 2004 Rusty Russell IBM Corporation
   * Copyright (C) 2007 Netfilter Core Team <coreteam@netfilter.org>
   * Copyright (C) 2007 USAGI/WIDE Project <http://www.linux-ipv6.org>
   *
   *      This program is free software; you can redistribute it and/or
   *      modify it under the terms of the GNU General Public License
   *      as published by the Free Software Foundation; either version
   *      2 of the License, or (at your option) any later version.
   */
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/mutex.h>
  #include <linux/rcupdate.h>
  #include <linux/slab.h>
  #include <linux/skbuff.h>
  #include <net/netfilter/nf_conntrack_extend.h>

  static struct nf_ct_ext_type __rcu *nf_ct_ext_types[NF_CT_EXT_NUM];

  static DEFINE_MUTEX(nf_ct_ext_type_mutex);

  void __nf_ct_ext_destroy(struct nf_conn *ct)
  {
  	unsigned int i;
  	struct nf_ct_ext_type *t;

  	struct nf_ct_ext *ext = ct->ext;

  
  	for (i = 0; i < NF_CT_EXT_NUM; i++) {

  		if (!__nf_ct_ext_exist(ext, i))

  			continue;
  
  		rcu_read_lock();
  		t = rcu_dereference(nf_ct_ext_types[i]);
  
  		/* Here the nf_ct_ext_type might have been unregisterd.
  		 * I.e., it has responsible to cleanup private
  		 * area in all conntracks when it is unregisterd.
  		 */
  		if (t && t->destroy)
  			t->destroy(ct);
  		rcu_read_unlock();
  	}
  }
  EXPORT_SYMBOL(__nf_ct_ext_destroy);
  
  static void *
  nf_ct_ext_create(struct nf_ct_ext **ext, enum nf_ct_ext_id id, gfp_t gfp)
  {

  	unsigned int off, len;

  	struct nf_ct_ext_type *t;

  	size_t alloc_size;

  
  	rcu_read_lock();
  	t = rcu_dereference(nf_ct_ext_types[id]);
  	BUG_ON(t == NULL);
  	off = ALIGN(sizeof(struct nf_ct_ext), t->align);
  	len = off + t->len;

  	alloc_size = t->alloc_size;

  	rcu_read_unlock();

  	*ext = kzalloc(alloc_size, gfp);

  	if (!*ext)
  		return NULL;
  
  	(*ext)->offset[id] = off;
  	(*ext)->len = len;

  
  	return (void *)(*ext) + off;
  }

  static void __nf_ct_ext_free_rcu(struct rcu_head *head)
  {
  	struct nf_ct_ext *ext = container_of(head, struct nf_ct_ext, rcu);
  	kfree(ext);
  }

  void *__nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
  {

  	struct nf_ct_ext *old, *new;

  	int i, newlen, newoff;
  	struct nf_ct_ext_type *t;

  	/* Conntrack must not be confirmed to avoid races on reallocation. */
  	NF_CT_ASSERT(!nf_ct_is_confirmed(ct));

  	old = ct->ext;
  	if (!old)

  		return nf_ct_ext_create(&ct->ext, id, gfp);

  	if (__nf_ct_ext_exist(old, id))

  		return NULL;
  
  	rcu_read_lock();
  	t = rcu_dereference(nf_ct_ext_types[id]);
  	BUG_ON(t == NULL);

  	newoff = ALIGN(old->len, t->align);

  	newlen = newoff + t->len;
  	rcu_read_unlock();

  	new = __krealloc(old, newlen, gfp);

  	if (!new)
  		return NULL;

  	if (new != old) {

  		for (i = 0; i < NF_CT_EXT_NUM; i++) {

  			if (!__nf_ct_ext_exist(old, i))

  				continue;
  
  			rcu_read_lock();
  			t = rcu_dereference(nf_ct_ext_types[i]);
  			if (t && t->move)

  				t->move((void *)new + new->offset[i],

  					(void *)old + old->offset[i]);

  			rcu_read_unlock();
  		}

  		call_rcu(&old->rcu, __nf_ct_ext_free_rcu);

  		ct->ext = new;
  	}

  	new->offset[id] = newoff;
  	new->len = newlen;
  	memset((void *)new + newoff, 0, newlen - newoff);
  	return (void *)new + newoff;

  }
  EXPORT_SYMBOL(__nf_ct_ext_add);
  
  static void update_alloc_size(struct nf_ct_ext_type *type)
  {
  	int i, j;
  	struct nf_ct_ext_type *t1, *t2;
  	enum nf_ct_ext_id min = 0, max = NF_CT_EXT_NUM - 1;
  
  	/* unnecessary to update all types */
  	if ((type->flags & NF_CT_EXT_F_PREALLOC) == 0) {
  		min = type->id;
  		max = type->id;
  	}
  
  	/* This assumes that extended areas in conntrack for the types
  	   whose NF_CT_EXT_F_PREALLOC bit set are allocated in order */
  	for (i = min; i <= max; i++) {
  		t1 = nf_ct_ext_types[i];
  		if (!t1)
  			continue;
  
  		t1->alloc_size = sizeof(struct nf_ct_ext)
  				 + ALIGN(sizeof(struct nf_ct_ext), t1->align)
  				 + t1->len;
  		for (j = 0; j < NF_CT_EXT_NUM; j++) {
  			t2 = nf_ct_ext_types[j];
  			if (t2 == NULL || t2 == t1 ||
  			    (t2->flags & NF_CT_EXT_F_PREALLOC) == 0)
  				continue;
  
  			t1->alloc_size = ALIGN(t1->alloc_size, t2->align)
  					 + t2->len;
  		}

  	}
  }
  
  /* This MUST be called in process context. */
  int nf_ct_extend_register(struct nf_ct_ext_type *type)
  {
  	int ret = 0;
  
  	mutex_lock(&nf_ct_ext_type_mutex);
  	if (nf_ct_ext_types[type->id]) {
  		ret = -EBUSY;
  		goto out;
  	}
  
  	/* This ensures that nf_ct_ext_create() can allocate enough area
  	   before updating alloc_size */
  	type->alloc_size = ALIGN(sizeof(struct nf_ct_ext), type->align)
  			   + type->len;
  	rcu_assign_pointer(nf_ct_ext_types[type->id], type);
  	update_alloc_size(type);
  out:
  	mutex_unlock(&nf_ct_ext_type_mutex);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(nf_ct_extend_register);
  
  /* This MUST be called in process context. */
  void nf_ct_extend_unregister(struct nf_ct_ext_type *type)
  {
  	mutex_lock(&nf_ct_ext_type_mutex);
  	rcu_assign_pointer(nf_ct_ext_types[type->id], NULL);
  	update_alloc_size(type);
  	mutex_unlock(&nf_ct_ext_type_mutex);

  	rcu_barrier(); /* Wait for completion of call_rcu()'s */

  }
  EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);