/*
   * Network node table
   *
   * SELinux must keep a mapping of network nodes to labels/SIDs.  This
   * mapping is maintained as part of the normal policy but a fast cache is
   * needed to reduce the lookup overhead since most of these queries happen on
   * a per-packet basis.
   *
   * Author: Paul Moore <paul@paul-moore.com>
   *
   * This code is heavily based on the "netif" concept originally developed by
   * James Morris <jmorris@redhat.com>
   *   (see security/selinux/netif.c for more information)
   *
   */
  
  /*
   * (c) Copyright Hewlett-Packard Development Company, L.P., 2007
   *
   * This program is free software: you can redistribute it and/or modify
   * it under the terms of version 2 of the GNU General Public License as
   * published by the Free Software Foundation.
   *
   * 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.
   *
   */
  
  #include <linux/types.h>
  #include <linux/rcupdate.h>
  #include <linux/list.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/in.h>
  #include <linux/in6.h>
  #include <linux/ip.h>
  #include <linux/ipv6.h>
  #include <net/ip.h>
  #include <net/ipv6.h>
  
  #include "netnode.h"
  #include "objsec.h"
  
  #define SEL_NETNODE_HASH_SIZE       256
  #define SEL_NETNODE_HASH_BKT_LIMIT   16
  
  struct sel_netnode_bkt {
  	unsigned int size;
  	struct list_head list;
  };
  
  struct sel_netnode {
  	struct netnode_security_struct nsec;
  
  	struct list_head list;
  	struct rcu_head rcu;
  };
  
  /* NOTE: we are using a combined hash table for both IPv4 and IPv6, the reason
   * for this is that I suspect most users will not make heavy use of both
   * address families at the same time so one table will usually end up wasted,
   * if this becomes a problem we can always add a hash table for each address
   * family later */
  
  static LIST_HEAD(sel_netnode_list);
  static DEFINE_SPINLOCK(sel_netnode_lock);
  static struct sel_netnode_bkt sel_netnode_hash[SEL_NETNODE_HASH_SIZE];
  
  /**
   * sel_netnode_hashfn_ipv4 - IPv4 hashing function for the node table
   * @addr: IPv4 address
   *
   * Description:
   * This is the IPv4 hashing function for the node interface table, it returns
   * the bucket number for the given IP address.
   *
   */
  static unsigned int sel_netnode_hashfn_ipv4(__be32 addr)
  {
  	/* at some point we should determine if the mismatch in byte order
  	 * affects the hash function dramatically */
  	return (addr & (SEL_NETNODE_HASH_SIZE - 1));
  }
  
  /**
   * sel_netnode_hashfn_ipv6 - IPv6 hashing function for the node table
   * @addr: IPv6 address
   *
   * Description:
   * This is the IPv6 hashing function for the node interface table, it returns
   * the bucket number for the given IP address.
   *
   */
  static unsigned int sel_netnode_hashfn_ipv6(const struct in6_addr *addr)
  {
  	/* just hash the least significant 32 bits to keep things fast (they
  	 * are the most likely to be different anyway), we can revisit this
  	 * later if needed */
  	return (addr->s6_addr32[3] & (SEL_NETNODE_HASH_SIZE - 1));
  }
  
  /**
   * sel_netnode_find - Search for a node record
   * @addr: IP address
   * @family: address family
   *
   * Description:
   * Search the network node table and return the record matching @addr.  If an
   * entry can not be found in the table return NULL.
   *
   */
  static struct sel_netnode *sel_netnode_find(const void *addr, u16 family)
  {
  	unsigned int idx;
  	struct sel_netnode *node;
  
  	switch (family) {
  	case PF_INET:
  		idx = sel_netnode_hashfn_ipv4(*(__be32 *)addr);
  		break;
  	case PF_INET6:
  		idx = sel_netnode_hashfn_ipv6(addr);
  		break;
  	default:
  		BUG();
  		return NULL;
  	}
  
  	list_for_each_entry_rcu(node, &sel_netnode_hash[idx].list, list)
  		if (node->nsec.family == family)
  			switch (family) {
  			case PF_INET:
  				if (node->nsec.addr.ipv4 == *(__be32 *)addr)
  					return node;
  				break;
  			case PF_INET6:
  				if (ipv6_addr_equal(&node->nsec.addr.ipv6,
  						    addr))
  					return node;
  				break;
  			}
  
  	return NULL;
  }
  
  /**
   * sel_netnode_insert - Insert a new node into the table
   * @node: the new node record
   *
   * Description:
   * Add a new node record to the network address hash table.
   *
   */
  static void sel_netnode_insert(struct sel_netnode *node)
  {
  	unsigned int idx;
  
  	switch (node->nsec.family) {
  	case PF_INET:
  		idx = sel_netnode_hashfn_ipv4(node->nsec.addr.ipv4);
  		break;
  	case PF_INET6:
  		idx = sel_netnode_hashfn_ipv6(&node->nsec.addr.ipv6);
  		break;
  	default:
  		BUG();
  		return;
  	}
  
  	/* we need to impose a limit on the growth of the hash table so check
  	 * this bucket to make sure it is within the specified bounds */
  	list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
  	if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
  		struct sel_netnode *tail;
  		tail = list_entry(
  			rcu_dereference_protected(sel_netnode_hash[idx].list.prev,
  						  lockdep_is_held(&sel_netnode_lock)),
  			struct sel_netnode, list);
  		list_del_rcu(&tail->list);
  		kfree_rcu(tail, rcu);
  	} else
  		sel_netnode_hash[idx].size++;
  }
  
  /**
   * sel_netnode_sid_slow - Lookup the SID of a network address using the policy
   * @addr: the IP address
   * @family: the address family
   * @sid: node SID
   *
   * Description:
   * This function determines the SID of a network address by quering the
   * security policy.  The result is added to the network address table to
   * speedup future queries.  Returns zero on success, negative values on
   * failure.
   *
   */
  static int sel_netnode_sid_slow(void *addr, u16 family, u32 *sid)
  {
  	int ret = -ENOMEM;
  	struct sel_netnode *node;
  	struct sel_netnode *new = NULL;
  
  	spin_lock_bh(&sel_netnode_lock);
  	node = sel_netnode_find(addr, family);
  	if (node != NULL) {
  		*sid = node->nsec.sid;
  		spin_unlock_bh(&sel_netnode_lock);
  		return 0;
  	}
  	new = kzalloc(sizeof(*new), GFP_ATOMIC);
  	if (new == NULL)
  		goto out;
  	switch (family) {
  	case PF_INET:
  		ret = security_node_sid(PF_INET,
  					addr, sizeof(struct in_addr), sid);
  		new->nsec.addr.ipv4 = *(__be32 *)addr;
  		break;
  	case PF_INET6:
  		ret = security_node_sid(PF_INET6,
  					addr, sizeof(struct in6_addr), sid);
  		new->nsec.addr.ipv6 = *(struct in6_addr *)addr;
  		break;
  	default:
  		BUG();
  		ret = -EINVAL;
  	}
  	if (ret != 0)
  		goto out;
  
  	new->nsec.family = family;
  	new->nsec.sid = *sid;
  	sel_netnode_insert(new);
  
  out:
  	spin_unlock_bh(&sel_netnode_lock);
  	if (unlikely(ret)) {
  		printk(KERN_WARNING
  		       "SELinux: failure in sel_netnode_sid_slow(),"
  		       " unable to determine network node label
  ");
  		kfree(new);
  	}
  	return ret;
  }
  
  /**
   * sel_netnode_sid - Lookup the SID of a network address
   * @addr: the IP address
   * @family: the address family
   * @sid: node SID
   *
   * Description:
   * This function determines the SID of a network address using the fastest
   * method possible.  First the address 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_netnode_sid(void *addr, u16 family, u32 *sid)
  {
  	struct sel_netnode *node;
  
  	rcu_read_lock();
  	node = sel_netnode_find(addr, family);
  	if (node != NULL) {
  		*sid = node->nsec.sid;
  		rcu_read_unlock();
  		return 0;
  	}
  	rcu_read_unlock();
  
  	return sel_netnode_sid_slow(addr, family, sid);
  }
  
  /**
   * sel_netnode_flush - Flush the entire network address table
   *
   * Description:
   * Remove all entries from the network address table.
   *
   */
  static void sel_netnode_flush(void)
  {
  	unsigned int idx;
  	struct sel_netnode *node, *node_tmp;
  
  	spin_lock_bh(&sel_netnode_lock);
  	for (idx = 0; idx < SEL_NETNODE_HASH_SIZE; idx++) {
  		list_for_each_entry_safe(node, node_tmp,
  					 &sel_netnode_hash[idx].list, list) {
  				list_del_rcu(&node->list);
  				kfree_rcu(node, rcu);
  		}
  		sel_netnode_hash[idx].size = 0;
  	}
  	spin_unlock_bh(&sel_netnode_lock);
  }
  
  static int sel_netnode_avc_callback(u32 event)
  {
  	if (event == AVC_CALLBACK_RESET) {
  		sel_netnode_flush();
  		synchronize_net();
  	}
  	return 0;
  }
  
  static __init int sel_netnode_init(void)
  {
  	int iter;
  	int ret;
  
  	if (!selinux_enabled)
  		return 0;
  
  	for (iter = 0; iter < SEL_NETNODE_HASH_SIZE; iter++) {
  		INIT_LIST_HEAD(&sel_netnode_hash[iter].list);
  		sel_netnode_hash[iter].size = 0;
  	}
  
  	ret = avc_add_callback(sel_netnode_avc_callback, AVC_CALLBACK_RESET);
  	if (ret != 0)
  		panic("avc_add_callback() failed, error %d
  ", ret);
  
  	return ret;
  }
  
  __initcall(sel_netnode_init);