/*
   * Network interface table.
   *
   * Network interfaces (devices) do not have a security field, so we
   * maintain a table associating each interface with a SID.
   *
   * Author: James Morris <jmorris@redhat.com>
   *
   * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
   * Copyright (C) 2007 Hewlett-Packard Development Company, L.P.
   *		      Paul Moore <paul@paul-moore.com>
   *
   * 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/init.h>
  #include <linux/types.h>
  #include <linux/slab.h>
  #include <linux/stddef.h>
  #include <linux/kernel.h>
  #include <linux/list.h>
  #include <linux/notifier.h>
  #include <linux/netdevice.h>
  #include <linux/rcupdate.h>
  #include <net/net_namespace.h>
  
  #include "security.h"
  #include "objsec.h"
  #include "netif.h"
  
  #define SEL_NETIF_HASH_SIZE	64
  #define SEL_NETIF_HASH_MAX	1024
  
  struct sel_netif {
  	struct list_head list;
  	struct netif_security_struct nsec;
  	struct rcu_head rcu_head;
  };
  
  static u32 sel_netif_total;
  static LIST_HEAD(sel_netif_list);
  static DEFINE_SPINLOCK(sel_netif_lock);
  static struct list_head sel_netif_hash[SEL_NETIF_HASH_SIZE];
  
  /**
   * sel_netif_hashfn - Hashing function for the interface table
   * @ifindex: the network interface
   *
   * Description:
   * This is the hashing function for the network interface table, it returns the
   * bucket number for the given interface.
   *
   */
  static inline u32 sel_netif_hashfn(int ifindex)
  {
  	return (ifindex & (SEL_NETIF_HASH_SIZE - 1));
  }
  
  /**
   * sel_netif_find - Search for an interface record
   * @ifindex: the network interface
   *
   * Description:
   * Search the network interface table and return the record matching @ifindex.
   * If an entry can not be found in the table return NULL.
   *
   */
  static inline struct sel_netif *sel_netif_find(int ifindex)
  {
  	int idx = sel_netif_hashfn(ifindex);
  	struct sel_netif *netif;
  
  	list_for_each_entry_rcu(netif, &sel_netif_hash[idx], list)
  		/* all of the devices should normally fit in the hash, so we
  		 * optimize for that case */
  		if (likely(netif->nsec.ifindex == ifindex))
  			return netif;
  
  	return NULL;
  }
  
  /**
   * sel_netif_insert - Insert a new interface into the table
   * @netif: the new interface record
   *
   * Description:
   * Add a new interface record to the network interface hash table.  Returns
   * zero on success, negative values on failure.
   *
   */
  static int sel_netif_insert(struct sel_netif *netif)
  {
  	int idx;
  
  	if (sel_netif_total >= SEL_NETIF_HASH_MAX)
  		return -ENOSPC;
  
  	idx = sel_netif_hashfn(netif->nsec.ifindex);
  	list_add_rcu(&netif->list, &sel_netif_hash[idx]);
  	sel_netif_total++;
  
  	return 0;
  }
  
  /**
   * sel_netif_destroy - Remove an interface record from the table
   * @netif: the existing interface record
   *
   * Description:
   * Remove an existing interface record from the network interface table.
   *
   */
  static void sel_netif_destroy(struct sel_netif *netif)
  {
  	list_del_rcu(&netif->list);
  	sel_netif_total--;
  	kfree_rcu(netif, rcu_head);
  }
  
  /**
   * sel_netif_sid_slow - Lookup the SID of a network interface using the policy
   * @ifindex: the network interface
   * @sid: interface SID
   *
   * Description:
   * This function determines the SID of a network interface by quering the
   * security policy.  The result is added to the network interface table to
   * speedup future queries.  Returns zero on success, negative values on
   * failure.
   *
   */
  static int sel_netif_sid_slow(int ifindex, u32 *sid)
  {
  	int ret;
  	struct sel_netif *netif;
  	struct sel_netif *new = NULL;
  	struct net_device *dev;
  
  	/* NOTE: we always use init's network namespace since we don't
  	 * currently support containers */
  
  	dev = dev_get_by_index(&init_net, ifindex);
  	if (unlikely(dev == NULL)) {
  		printk(KERN_WARNING
  		       "SELinux: failure in sel_netif_sid_slow(),"
  		       " invalid network interface (%d)
  ", ifindex);
  		return -ENOENT;
  	}
  
  	spin_lock_bh(&sel_netif_lock);
  	netif = sel_netif_find(ifindex);
  	if (netif != NULL) {
  		*sid = netif->nsec.sid;
  		ret = 0;
  		goto out;
  	}
  	new = kzalloc(sizeof(*new), GFP_ATOMIC);
  	if (new == NULL) {
  		ret = -ENOMEM;
  		goto out;
  	}
  	ret = security_netif_sid(dev->name, &new->nsec.sid);
  	if (ret != 0)
  		goto out;
  	new->nsec.ifindex = ifindex;
  	ret = sel_netif_insert(new);
  	if (ret != 0)
  		goto out;
  	*sid = new->nsec.sid;
  
  out:
  	spin_unlock_bh(&sel_netif_lock);
  	dev_put(dev);
  	if (unlikely(ret)) {
  		printk(KERN_WARNING
  		       "SELinux: failure in sel_netif_sid_slow(),"
  		       " unable to determine network interface label (%d)
  ",
  		       ifindex);
  		kfree(new);
  	}
  	return ret;
  }
  
  /**
   * sel_netif_sid - Lookup the SID of a network interface
   * @ifindex: the network interface
   * @sid: interface SID
   *
   * Description:
   * This function determines the SID of a network interface using the fastest
   * method possible.  First the interface table is queried, but if an entry
   * can't be found then the policy is queried and the result is added to the
   * table to speedup future queries.  Returns zero on success, negative values
   * on failure.
   *
   */
  int sel_netif_sid(int ifindex, u32 *sid)
  {
  	struct sel_netif *netif;
  
  	rcu_read_lock();
  	netif = sel_netif_find(ifindex);
  	if (likely(netif != NULL)) {
  		*sid = netif->nsec.sid;
  		rcu_read_unlock();
  		return 0;
  	}
  	rcu_read_unlock();
  
  	return sel_netif_sid_slow(ifindex, sid);
  }
  
  /**
   * sel_netif_kill - Remove an entry from the network interface table
   * @ifindex: the network interface
   *
   * Description:
   * This function removes the entry matching @ifindex from the network interface
   * table if it exists.
   *
   */
  static void sel_netif_kill(int ifindex)
  {
  	struct sel_netif *netif;
  
  	rcu_read_lock();
  	spin_lock_bh(&sel_netif_lock);
  	netif = sel_netif_find(ifindex);
  	if (netif)
  		sel_netif_destroy(netif);
  	spin_unlock_bh(&sel_netif_lock);
  	rcu_read_unlock();
  }
  
  /**
   * sel_netif_flush - Flush the entire network interface table
   *
   * Description:
   * Remove all entries from the network interface table.
   *
   */
  static void sel_netif_flush(void)
  {
  	int idx;
  	struct sel_netif *netif;
  
  	spin_lock_bh(&sel_netif_lock);
  	for (idx = 0; idx < SEL_NETIF_HASH_SIZE; idx++)
  		list_for_each_entry(netif, &sel_netif_hash[idx], list)
  			sel_netif_destroy(netif);
  	spin_unlock_bh(&sel_netif_lock);
  }
  
  static int sel_netif_avc_callback(u32 event)
  {
  	if (event == AVC_CALLBACK_RESET) {
  		sel_netif_flush();
  		synchronize_net();
  	}
  	return 0;
  }
  
  static int sel_netif_netdev_notifier_handler(struct notifier_block *this,
  					     unsigned long event, void *ptr)
  {
  	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
  
  	if (dev_net(dev) != &init_net)
  		return NOTIFY_DONE;
  
  	if (event == NETDEV_DOWN)
  		sel_netif_kill(dev->ifindex);
  
  	return NOTIFY_DONE;
  }
  
  static struct notifier_block sel_netif_netdev_notifier = {
  	.notifier_call = sel_netif_netdev_notifier_handler,
  };
  
  static __init int sel_netif_init(void)
  {
  	int i, err;
  
  	if (!selinux_enabled)
  		return 0;
  
  	for (i = 0; i < SEL_NETIF_HASH_SIZE; i++)
  		INIT_LIST_HEAD(&sel_netif_hash[i]);
  
  	register_netdevice_notifier(&sel_netif_netdev_notifier);
  
  	err = avc_add_callback(sel_netif_avc_callback, AVC_CALLBACK_RESET);
  	if (err)
  		panic("avc_add_callback() failed, error %d
  ", err);
  
  	return err;
  }
  
  __initcall(sel_netif_init);