/*
   * NetLabel Domain Hash Table
   *
   * This file manages the domain hash table that NetLabel uses to determine
   * which network labeling protocol to use for a given domain.  The NetLabel
   * system manages static and dynamic label mappings for network protocols such
   * as CIPSO and RIPSO.
   *
   * Author: Paul Moore <paul.moore@hp.com>
   *
   */
  
  /*
   * (c) Copyright Hewlett-Packard Development Company, L.P., 2006
   *
   * 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.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY;  without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
   * the GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program;  if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
   *
   */
  
  #include <linux/types.h>
  #include <linux/rcupdate.h>
  #include <linux/list.h>
  #include <linux/skbuff.h>
  #include <linux/spinlock.h>
  #include <linux/string.h>

  #include <linux/audit.h>

  #include <net/netlabel.h>
  #include <net/cipso_ipv4.h>
  #include <asm/bug.h>
  
  #include "netlabel_mgmt.h"
  #include "netlabel_domainhash.h"

  #include "netlabel_user.h"

  
  struct netlbl_domhsh_tbl {
  	struct list_head *tbl;
  	u32 size;
  };
  
  /* Domain hash table */
  /* XXX - updates should be so rare that having one spinlock for the entire
   * hash table should be okay */

  static DEFINE_SPINLOCK(netlbl_domhsh_lock);

  static struct netlbl_domhsh_tbl *netlbl_domhsh = NULL;
  
  /* Default domain mapping */

  static DEFINE_SPINLOCK(netlbl_domhsh_def_lock);

  static struct netlbl_dom_map *netlbl_domhsh_def = NULL;
  
  /*
   * Domain Hash Table Helper Functions
   */
  
  /**
   * netlbl_domhsh_free_entry - Frees a domain hash table entry
   * @entry: the entry's RCU field
   *
   * Description:
   * This function is designed to be used as a callback to the call_rcu()
   * function so that the memory allocated to a hash table entry can be released
   * safely.
   *
   */
  static void netlbl_domhsh_free_entry(struct rcu_head *entry)
  {
  	struct netlbl_dom_map *ptr;
  
  	ptr = container_of(entry, struct netlbl_dom_map, rcu);
  	kfree(ptr->domain);
  	kfree(ptr);
  }
  
  /**
   * netlbl_domhsh_hash - Hashing function for the domain hash table
   * @domain: the domain name to hash
   *
   * Description:
   * This is the hashing function for the domain hash table, it returns the
   * correct bucket number for the domain.  The caller is responsibile for
   * calling the rcu_read_[un]lock() functions.
   *
   */
  static u32 netlbl_domhsh_hash(const char *key)
  {
  	u32 iter;
  	u32 val;
  	u32 len;
  
  	/* This is taken (with slight modification) from
  	 * security/selinux/ss/symtab.c:symhash() */
  
  	for (iter = 0, val = 0, len = strlen(key); iter < len; iter++)
  		val = (val << 4 | (val >> (8 * sizeof(u32) - 4))) ^ key[iter];
  	return val & (rcu_dereference(netlbl_domhsh)->size - 1);
  }
  
  /**
   * netlbl_domhsh_search - Search for a domain entry
   * @domain: the domain
   * @def: return default if no match is found
   *
   * Description:
   * Searches the domain hash table and returns a pointer to the hash table
   * entry if found, otherwise NULL is returned.  If @def is non-zero and a
   * match is not found in the domain hash table the default mapping is returned
   * if it exists.  The caller is responsibile for the rcu hash table locks
   * (i.e. the caller much call rcu_read_[un]lock()).
   *
   */
  static struct netlbl_dom_map *netlbl_domhsh_search(const char *domain, u32 def)
  {
  	u32 bkt;
  	struct netlbl_dom_map *iter;
  
  	if (domain != NULL) {
  		bkt = netlbl_domhsh_hash(domain);
  		list_for_each_entry_rcu(iter, &netlbl_domhsh->tbl[bkt], list)
  			if (iter->valid && strcmp(iter->domain, domain) == 0)
  				return iter;
  	}
  
  	if (def != 0) {
  		iter = rcu_dereference(netlbl_domhsh_def);
  		if (iter != NULL && iter->valid)
  			return iter;
  	}
  
  	return NULL;
  }
  
  /*
   * Domain Hash Table Functions
   */
  
  /**
   * netlbl_domhsh_init - Init for the domain hash
   * @size: the number of bits to use for the hash buckets
   *
   * Description:
   * Initializes the domain hash table, should be called only by
   * netlbl_user_init() during initialization.  Returns zero on success, non-zero
   * values on error.
   *
   */
  int netlbl_domhsh_init(u32 size)
  {
  	u32 iter;
  	struct netlbl_domhsh_tbl *hsh_tbl;
  
  	if (size == 0)
  		return -EINVAL;
  
  	hsh_tbl = kmalloc(sizeof(*hsh_tbl), GFP_KERNEL);
  	if (hsh_tbl == NULL)
  		return -ENOMEM;
  	hsh_tbl->size = 1 << size;
  	hsh_tbl->tbl = kcalloc(hsh_tbl->size,
  			       sizeof(struct list_head),
  			       GFP_KERNEL);
  	if (hsh_tbl->tbl == NULL) {
  		kfree(hsh_tbl);
  		return -ENOMEM;
  	}
  	for (iter = 0; iter < hsh_tbl->size; iter++)
  		INIT_LIST_HEAD(&hsh_tbl->tbl[iter]);
  
  	rcu_read_lock();
  	spin_lock(&netlbl_domhsh_lock);
  	rcu_assign_pointer(netlbl_domhsh, hsh_tbl);
  	spin_unlock(&netlbl_domhsh_lock);
  	rcu_read_unlock();
  
  	return 0;
  }
  
  /**
   * netlbl_domhsh_add - Adds a entry to the domain hash table
   * @entry: the entry to add

   * @audit_info: NetLabel audit information

   *
   * Description:
   * Adds a new entry to the domain hash table and handles any updates to the
   * lower level protocol handler (i.e. CIPSO).  Returns zero on success,
   * negative on failure.
   *
   */

  int netlbl_domhsh_add(struct netlbl_dom_map *entry,
  		      struct netlbl_audit *audit_info)

  {
  	int ret_val;
  	u32 bkt;

  	struct audit_buffer *audit_buf;

  
  	switch (entry->type) {
  	case NETLBL_NLTYPE_UNLABELED:
  		ret_val = 0;
  		break;
  	case NETLBL_NLTYPE_CIPSOV4:
  		ret_val = cipso_v4_doi_domhsh_add(entry->type_def.cipsov4,
  						  entry->domain);
  		break;
  	default:
  		return -EINVAL;
  	}
  	if (ret_val != 0)
  		return ret_val;
  
  	entry->valid = 1;
  	INIT_RCU_HEAD(&entry->rcu);
  
  	ret_val = 0;
  	rcu_read_lock();
  	if (entry->domain != NULL) {
  		bkt = netlbl_domhsh_hash(entry->domain);
  		spin_lock(&netlbl_domhsh_lock);
  		if (netlbl_domhsh_search(entry->domain, 0) == NULL)
  			list_add_tail_rcu(&entry->list,
  					  &netlbl_domhsh->tbl[bkt]);
  		else
  			ret_val = -EEXIST;
  		spin_unlock(&netlbl_domhsh_lock);
  	} else if (entry->domain == NULL) {
  		INIT_LIST_HEAD(&entry->list);
  		spin_lock(&netlbl_domhsh_def_lock);
  		if (rcu_dereference(netlbl_domhsh_def) == NULL)
  			rcu_assign_pointer(netlbl_domhsh_def, entry);
  		else
  			ret_val = -EEXIST;
  		spin_unlock(&netlbl_domhsh_def_lock);
  	} else
  		ret_val = -EINVAL;

  	audit_buf = netlbl_audit_start_common(AUDIT_MAC_MAP_ADD, audit_info);

  	if (audit_buf != NULL) {

  		audit_log_format(audit_buf,

  				 " nlbl_domain=%s",
  				 entry->domain ? entry->domain : "(default)");
  		switch (entry->type) {
  		case NETLBL_NLTYPE_UNLABELED:
  			audit_log_format(audit_buf, " nlbl_protocol=unlbl");
  			break;
  		case NETLBL_NLTYPE_CIPSOV4:
  			audit_log_format(audit_buf,
  					 " nlbl_protocol=cipsov4 cipso_doi=%u",
  					 entry->type_def.cipsov4->doi);
  			break;
  		}
  		audit_log_format(audit_buf, " res=%u", ret_val == 0 ? 1 : 0);
  		audit_log_end(audit_buf);

  	}

  	rcu_read_unlock();
  
  	if (ret_val != 0) {
  		switch (entry->type) {
  		case NETLBL_NLTYPE_CIPSOV4:
  			if (cipso_v4_doi_domhsh_remove(entry->type_def.cipsov4,
  						       entry->domain) != 0)
  				BUG();
  			break;
  		}
  	}
  
  	return ret_val;
  }
  
  /**
   * netlbl_domhsh_add_default - Adds the default entry to the domain hash table
   * @entry: the entry to add

   * @audit_info: NetLabel audit information

   *
   * Description:
   * Adds a new default entry to the domain hash table and handles any updates
   * to the lower level protocol handler (i.e. CIPSO).  Returns zero on success,
   * negative on failure.
   *
   */

  int netlbl_domhsh_add_default(struct netlbl_dom_map *entry,
  			      struct netlbl_audit *audit_info)

  {

  	return netlbl_domhsh_add(entry, audit_info);

  }
  
  /**
   * netlbl_domhsh_remove - Removes an entry from the domain hash table
   * @domain: the domain to remove

   * @audit_info: NetLabel audit information

   *
   * Description:
   * Removes an entry from the domain hash table and handles any updates to the
   * lower level protocol handler (i.e. CIPSO).  Returns zero on success,
   * negative on failure.
   *
   */

  int netlbl_domhsh_remove(const char *domain, struct netlbl_audit *audit_info)

  {
  	int ret_val = -ENOENT;
  	struct netlbl_dom_map *entry;

  	struct audit_buffer *audit_buf;

  
  	rcu_read_lock();
  	if (domain != NULL)
  		entry = netlbl_domhsh_search(domain, 0);
  	else
  		entry = netlbl_domhsh_search(domain, 1);
  	if (entry == NULL)
  		goto remove_return;
  	switch (entry->type) {
  	case NETLBL_NLTYPE_UNLABELED:
  		break;
  	case NETLBL_NLTYPE_CIPSOV4:
  		ret_val = cipso_v4_doi_domhsh_remove(entry->type_def.cipsov4,
  						     entry->domain);
  		if (ret_val != 0)
  			goto remove_return;
  		break;
  	}
  	ret_val = 0;
  	if (entry != rcu_dereference(netlbl_domhsh_def)) {
  		spin_lock(&netlbl_domhsh_lock);
  		if (entry->valid) {
  			entry->valid = 0;
  			list_del_rcu(&entry->list);
  		} else
  			ret_val = -ENOENT;
  		spin_unlock(&netlbl_domhsh_lock);
  	} else {
  		spin_lock(&netlbl_domhsh_def_lock);
  		if (entry->valid) {
  			entry->valid = 0;
  			rcu_assign_pointer(netlbl_domhsh_def, NULL);
  		} else
  			ret_val = -ENOENT;
  		spin_unlock(&netlbl_domhsh_def_lock);
  	}

  	audit_buf = netlbl_audit_start_common(AUDIT_MAC_MAP_DEL, audit_info);

  	if (audit_buf != NULL) {
  		audit_log_format(audit_buf,
  				 " nlbl_domain=%s res=%u",
  				 entry->domain ? entry->domain : "(default)",
  				 ret_val == 0 ? 1 : 0);
  		audit_log_end(audit_buf);
  	}

  
  	if (ret_val == 0)

  		call_rcu(&entry->rcu, netlbl_domhsh_free_entry);
  
  remove_return:
  	rcu_read_unlock();
  	return ret_val;
  }
  
  /**
   * netlbl_domhsh_remove_default - Removes the default entry from the table

   * @audit_info: NetLabel audit information

   *
   * Description:
   * Removes/resets the default entry for the domain hash table and handles any
   * updates to the lower level protocol handler (i.e. CIPSO).  Returns zero on
   * success, non-zero on failure.
   *
   */

  int netlbl_domhsh_remove_default(struct netlbl_audit *audit_info)

  {

  	return netlbl_domhsh_remove(NULL, audit_info);

  }
  
  /**
   * netlbl_domhsh_getentry - Get an entry from the domain hash table
   * @domain: the domain name to search for
   *
   * Description:
   * Look through the domain hash table searching for an entry to match @domain,
   * return a pointer to a copy of the entry or NULL.  The caller is responsibile
   * for ensuring that rcu_read_[un]lock() is called.
   *
   */
  struct netlbl_dom_map *netlbl_domhsh_getentry(const char *domain)
  {
  	return netlbl_domhsh_search(domain, 1);
  }
  
  /**

   * netlbl_domhsh_walk - Iterate through the domain mapping hash table
   * @skip_bkt: the number of buckets to skip at the start
   * @skip_chain: the number of entries to skip in the first iterated bucket
   * @callback: callback for each entry
   * @cb_arg: argument for the callback function

   *
   * Description:

   * Interate over the domain mapping hash table, skipping the first @skip_bkt
   * buckets and @skip_chain entries.  For each entry in the table call
   * @callback, if @callback returns a negative value stop 'walking' through the
   * table and return.  Updates the values in @skip_bkt and @skip_chain on
   * return.  Returns zero on succcess, negative values on failure.

   *
   */

  int netlbl_domhsh_walk(u32 *skip_bkt,
  		     u32 *skip_chain,
  		     int (*callback) (struct netlbl_dom_map *entry, void *arg),
  		     void *cb_arg)

  {

  	int ret_val = -ENOENT;
  	u32 iter_bkt;
  	struct netlbl_dom_map *iter_entry;
  	u32 chain_cnt = 0;

  	rcu_read_lock();

  	for (iter_bkt = *skip_bkt;
  	     iter_bkt < rcu_dereference(netlbl_domhsh)->size;
  	     iter_bkt++, chain_cnt = 0) {
  		list_for_each_entry_rcu(iter_entry,
  					&netlbl_domhsh->tbl[iter_bkt],
  					list)
  			if (iter_entry->valid) {
  				if (chain_cnt++ < *skip_chain)
  					continue;
  				ret_val = callback(iter_entry, cb_arg);
  				if (ret_val < 0) {
  					chain_cnt--;
  					goto walk_return;
  				}

  			}

  	}

  walk_return:

  	rcu_read_unlock();

  	*skip_bkt = iter_bkt;
  	*skip_chain = chain_cnt;
  	return ret_val;

  }