/*
   *	Anycast support for IPv6

   *	Linux INET6 implementation

   *
   *	Authors:
   *	David L Stevens (dlstevens@us.ibm.com)
   *
   *	based heavily on net/ipv6/mcast.c
   *
   *	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/capability.h>

  #include <linux/module.h>
  #include <linux/errno.h>
  #include <linux/types.h>
  #include <linux/random.h>
  #include <linux/string.h>
  #include <linux/socket.h>
  #include <linux/sockios.h>

  #include <linux/net.h>
  #include <linux/in6.h>
  #include <linux/netdevice.h>
  #include <linux/if_arp.h>
  #include <linux/route.h>
  #include <linux/init.h>
  #include <linux/proc_fs.h>
  #include <linux/seq_file.h>

  #include <linux/slab.h>

  #include <net/net_namespace.h>

  #include <net/sock.h>
  #include <net/snmp.h>
  
  #include <net/ipv6.h>
  #include <net/protocol.h>
  #include <net/if_inet6.h>
  #include <net/ndisc.h>
  #include <net/addrconf.h>
  #include <net/ip6_route.h>
  
  #include <net/checksum.h>

  static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr);

  
  /* Big ac list lock for all the sockets */
  static DEFINE_RWLOCK(ipv6_sk_ac_lock);

  
  /*
   *	socket join an anycast group
   */

  int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)

  {
  	struct ipv6_pinfo *np = inet6_sk(sk);
  	struct net_device *dev = NULL;
  	struct inet6_dev *idev;
  	struct ipv6_ac_socklist *pac;

  	struct net *net = sock_net(sk);

  	int	ishost = !net->ipv6.devconf_all->forwarding;

  	int	err = 0;
  
  	if (!capable(CAP_NET_ADMIN))
  		return -EPERM;
  	if (ipv6_addr_is_multicast(addr))
  		return -EINVAL;

  	if (ipv6_chk_addr(net, addr, NULL, 0))

  		return -EINVAL;
  
  	pac = sock_kmalloc(sk, sizeof(struct ipv6_ac_socklist), GFP_KERNEL);
  	if (pac == NULL)
  		return -ENOMEM;
  	pac->acl_next = NULL;

  	pac->acl_addr = *addr;

  	rcu_read_lock();

  	if (ifindex == 0) {
  		struct rt6_info *rt;

  		rt = rt6_lookup(net, addr, NULL, 0, 0);

  		if (rt) {

  			dev = rt->dst.dev;

  			dst_release(&rt->dst);

  		} else if (ishost) {
  			err = -EADDRNOTAVAIL;

  			goto error;

  		} else {
  			/* router, no matching interface: just pick one */

  			dev = dev_get_by_flags_rcu(net, IFF_UP,
  						   IFF_UP | IFF_LOOPBACK);

  		}
  	} else

  		dev = dev_get_by_index_rcu(net, ifindex);

  
  	if (dev == NULL) {
  		err = -ENODEV;

  		goto error;

  	}

  	idev = __in6_dev_get(dev);

  	if (!idev) {
  		if (ifindex)
  			err = -ENODEV;
  		else
  			err = -EADDRNOTAVAIL;

  		goto error;

  	}
  	/* reset ishost, now that we have a specific device */
  	ishost = !idev->cnf.forwarding;

  
  	pac->acl_ifindex = dev->ifindex;
  
  	/* XXX
  	 * For hosts, allow link-local or matching prefix anycasts.
  	 * This obviates the need for propagating anycast routes while
  	 * still allowing some non-router anycast participation.
  	 */

  	if (!ipv6_chk_prefix(addr, dev)) {

  		if (ishost)
  			err = -EADDRNOTAVAIL;
  		if (err)

  			goto error;

  	}
  
  	err = ipv6_dev_ac_inc(dev, addr);

  	if (!err) {
  		write_lock_bh(&ipv6_sk_ac_lock);
  		pac->acl_next = np->ipv6_ac_list;
  		np->ipv6_ac_list = pac;
  		write_unlock_bh(&ipv6_sk_ac_lock);
  		pac = NULL;
  	}

  error:
  	rcu_read_unlock();
  	if (pac)
  		sock_kfree_s(sk, pac, sizeof(*pac));

  	return err;
  }
  
  /*
   *	socket leave an anycast group
   */

  int ipv6_sock_ac_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)

  {
  	struct ipv6_pinfo *np = inet6_sk(sk);
  	struct net_device *dev;
  	struct ipv6_ac_socklist *pac, *prev_pac;

  	struct net *net = sock_net(sk);

  
  	write_lock_bh(&ipv6_sk_ac_lock);
  	prev_pac = NULL;
  	for (pac = np->ipv6_ac_list; pac; pac = pac->acl_next) {
  		if ((ifindex == 0 || pac->acl_ifindex == ifindex) &&
  		     ipv6_addr_equal(&pac->acl_addr, addr))
  			break;
  		prev_pac = pac;
  	}
  	if (!pac) {
  		write_unlock_bh(&ipv6_sk_ac_lock);
  		return -ENOENT;
  	}
  	if (prev_pac)
  		prev_pac->acl_next = pac->acl_next;
  	else
  		np->ipv6_ac_list = pac->acl_next;
  
  	write_unlock_bh(&ipv6_sk_ac_lock);

  	rcu_read_lock();
  	dev = dev_get_by_index_rcu(net, pac->acl_ifindex);
  	if (dev)

  		ipv6_dev_ac_dec(dev, &pac->acl_addr);

  	rcu_read_unlock();

  	sock_kfree_s(sk, pac, sizeof(*pac));
  	return 0;
  }
  
  void ipv6_sock_ac_close(struct sock *sk)
  {
  	struct ipv6_pinfo *np = inet6_sk(sk);
  	struct net_device *dev = NULL;
  	struct ipv6_ac_socklist *pac;

  	struct net *net = sock_net(sk);

  	int	prev_index;
  
  	write_lock_bh(&ipv6_sk_ac_lock);
  	pac = np->ipv6_ac_list;
  	np->ipv6_ac_list = NULL;
  	write_unlock_bh(&ipv6_sk_ac_lock);
  
  	prev_index = 0;

  	rcu_read_lock();

  	while (pac) {
  		struct ipv6_ac_socklist *next = pac->acl_next;
  
  		if (pac->acl_ifindex != prev_index) {

  			dev = dev_get_by_index_rcu(net, pac->acl_ifindex);

  			prev_index = pac->acl_ifindex;
  		}
  		if (dev)
  			ipv6_dev_ac_dec(dev, &pac->acl_addr);
  		sock_kfree_s(sk, pac, sizeof(*pac));
  		pac = next;
  	}

  	rcu_read_unlock();

  }
  
  #if 0
  /* The function is not used, which is funny. Apparently, author
   * supposed to use it to filter out datagrams inside udp/raw but forgot.
   *
   * It is OK, anycasts are not special comparing to delivery to unicasts.
   */
  
  int inet6_ac_check(struct sock *sk, struct in6_addr *addr, int ifindex)
  {
  	struct ipv6_ac_socklist *pac;
  	struct ipv6_pinfo *np = inet6_sk(sk);
  	int	found;
  
  	found = 0;
  	read_lock(&ipv6_sk_ac_lock);
  	for (pac=np->ipv6_ac_list; pac; pac=pac->acl_next) {
  		if (ifindex && pac->acl_ifindex != ifindex)
  			continue;
  		found = ipv6_addr_equal(&pac->acl_addr, addr);
  		if (found)
  			break;
  	}
  	read_unlock(&ipv6_sk_ac_lock);
  
  	return found;
  }
  
  #endif
  
  static void aca_put(struct ifacaddr6 *ac)
  {
  	if (atomic_dec_and_test(&ac->aca_refcnt)) {
  		in6_dev_put(ac->aca_idev);

  		dst_release(&ac->aca_rt->dst);

  		kfree(ac);
  	}
  }
  
  /*
   *	device anycast group inc (add if not found)
   */

  int ipv6_dev_ac_inc(struct net_device *dev, const struct in6_addr *addr)

  {
  	struct ifacaddr6 *aca;
  	struct inet6_dev *idev;
  	struct rt6_info *rt;
  	int err;
  
  	idev = in6_dev_get(dev);
  
  	if (idev == NULL)
  		return -EINVAL;
  
  	write_lock_bh(&idev->lock);
  	if (idev->dead) {
  		err = -ENODEV;
  		goto out;
  	}
  
  	for (aca = idev->ac_list; aca; aca = aca->aca_next) {
  		if (ipv6_addr_equal(&aca->aca_addr, addr)) {
  			aca->aca_users++;
  			err = 0;
  			goto out;
  		}
  	}
  
  	/*
  	 *	not found: create a new one.
  	 */

  	aca = kzalloc(sizeof(struct ifacaddr6), GFP_ATOMIC);

  
  	if (aca == NULL) {
  		err = -ENOMEM;
  		goto out;
  	}

  	rt = addrconf_dst_alloc(idev, addr, true);

  	if (IS_ERR(rt)) {
  		kfree(aca);
  		err = PTR_ERR(rt);
  		goto out;
  	}

  	aca->aca_addr = *addr;

  	aca->aca_idev = idev;
  	aca->aca_rt = rt;
  	aca->aca_users = 1;
  	/* aca_tstamp should be updated upon changes */
  	aca->aca_cstamp = aca->aca_tstamp = jiffies;
  	atomic_set(&aca->aca_refcnt, 2);
  	spin_lock_init(&aca->aca_lock);
  
  	aca->aca_next = idev->ac_list;
  	idev->ac_list = aca;
  	write_unlock_bh(&idev->lock);

  	ip6_ins_rt(rt);

  
  	addrconf_join_solict(dev, &aca->aca_addr);
  
  	aca_put(aca);
  	return 0;
  out:
  	write_unlock_bh(&idev->lock);
  	in6_dev_put(idev);
  	return err;
  }
  
  /*
   *	device anycast group decrement
   */

  int __ipv6_dev_ac_dec(struct inet6_dev *idev, const struct in6_addr *addr)

  {
  	struct ifacaddr6 *aca, *prev_aca;
  
  	write_lock_bh(&idev->lock);
  	prev_aca = NULL;
  	for (aca = idev->ac_list; aca; aca = aca->aca_next) {
  		if (ipv6_addr_equal(&aca->aca_addr, addr))
  			break;
  		prev_aca = aca;
  	}
  	if (!aca) {
  		write_unlock_bh(&idev->lock);
  		return -ENOENT;
  	}
  	if (--aca->aca_users > 0) {
  		write_unlock_bh(&idev->lock);
  		return 0;
  	}
  	if (prev_aca)
  		prev_aca->aca_next = aca->aca_next;
  	else
  		idev->ac_list = aca->aca_next;
  	write_unlock_bh(&idev->lock);
  	addrconf_leave_solict(idev, &aca->aca_addr);

  	dst_hold(&aca->aca_rt->dst);

  	ip6_del_rt(aca->aca_rt);

  
  	aca_put(aca);
  	return 0;
  }

  /* called with rcu_read_lock() */

  static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr)

  {

  	struct inet6_dev *idev = __in6_dev_get(dev);

  	if (idev == NULL)
  		return -ENODEV;

  	return __ipv6_dev_ac_dec(idev, addr);

  }

  /*
   *	check if the interface has this anycast address

   *	called with rcu_read_lock()

   */

  static int ipv6_chk_acast_dev(struct net_device *dev, const struct in6_addr *addr)

  {
  	struct inet6_dev *idev;
  	struct ifacaddr6 *aca;

  	idev = __in6_dev_get(dev);

  	if (idev) {
  		read_lock_bh(&idev->lock);
  		for (aca = idev->ac_list; aca; aca = aca->aca_next)
  			if (ipv6_addr_equal(&aca->aca_addr, addr))
  				break;
  		read_unlock_bh(&idev->lock);

  		return aca != NULL;

  	}
  	return 0;
  }
  
  /*
   *	check if given interface (or any, if dev==0) has this anycast address
   */

  int ipv6_chk_acast_addr(struct net *net, struct net_device *dev,

  			const struct in6_addr *addr)

  {

  	int found = 0;

  	rcu_read_lock();

  	if (dev)
  		found = ipv6_chk_acast_dev(dev, addr);
  	else
  		for_each_netdev_rcu(net, dev)
  			if (ipv6_chk_acast_dev(dev, addr)) {
  				found = 1;
  				break;
  			}

  	rcu_read_unlock();

  	return found;

  }
  
  
  #ifdef CONFIG_PROC_FS
  struct ac6_iter_state {

  	struct seq_net_private p;

  	struct net_device *dev;
  	struct inet6_dev *idev;
  };
  
  #define ac6_seq_private(seq)	((struct ac6_iter_state *)(seq)->private)
  
  static inline struct ifacaddr6 *ac6_get_first(struct seq_file *seq)
  {
  	struct ifacaddr6 *im = NULL;
  	struct ac6_iter_state *state = ac6_seq_private(seq);

  	struct net *net = seq_file_net(seq);

  	state->idev = NULL;

  	for_each_netdev_rcu(net, state->dev) {

  		struct inet6_dev *idev;

  		idev = __in6_dev_get(state->dev);

  		if (!idev)
  			continue;
  		read_lock_bh(&idev->lock);
  		im = idev->ac_list;
  		if (im) {
  			state->idev = idev;
  			break;
  		}
  		read_unlock_bh(&idev->lock);
  	}
  	return im;
  }
  
  static struct ifacaddr6 *ac6_get_next(struct seq_file *seq, struct ifacaddr6 *im)
  {
  	struct ac6_iter_state *state = ac6_seq_private(seq);
  
  	im = im->aca_next;
  	while (!im) {

  		if (likely(state->idev != NULL))

  			read_unlock_bh(&state->idev->lock);

  
  		state->dev = next_net_device_rcu(state->dev);

  		if (!state->dev) {
  			state->idev = NULL;
  			break;
  		}

  		state->idev = __in6_dev_get(state->dev);

  		if (!state->idev)
  			continue;
  		read_lock_bh(&state->idev->lock);
  		im = state->idev->ac_list;
  	}
  	return im;
  }
  
  static struct ifacaddr6 *ac6_get_idx(struct seq_file *seq, loff_t pos)
  {
  	struct ifacaddr6 *im = ac6_get_first(seq);
  	if (im)
  		while (pos && (im = ac6_get_next(seq, im)) != NULL)
  			--pos;
  	return pos ? NULL : im;
  }
  
  static void *ac6_seq_start(struct seq_file *seq, loff_t *pos)

  	__acquires(RCU)

  {

  	rcu_read_lock();

  	return ac6_get_idx(seq, *pos);
  }
  
  static void *ac6_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  {

  	struct ifacaddr6 *im = ac6_get_next(seq, v);

  	++*pos;
  	return im;
  }
  
  static void ac6_seq_stop(struct seq_file *seq, void *v)

  	__releases(RCU)

  {
  	struct ac6_iter_state *state = ac6_seq_private(seq);

  	if (likely(state->idev != NULL)) {
  		read_unlock_bh(&state->idev->lock);

  		state->idev = NULL;

  	}

  	rcu_read_unlock();

  }
  
  static int ac6_seq_show(struct seq_file *seq, void *v)
  {
  	struct ifacaddr6 *im = (struct ifacaddr6 *)v;
  	struct ac6_iter_state *state = ac6_seq_private(seq);

  	seq_printf(seq, "%-4d %-15s %pi6 %5d
  ",

  		   state->dev->ifindex, state->dev->name,

  		   &im->aca_addr, im->aca_users);

  	return 0;
  }

  static const struct seq_operations ac6_seq_ops = {

  	.start	=	ac6_seq_start,
  	.next	=	ac6_seq_next,
  	.stop	=	ac6_seq_stop,
  	.show	=	ac6_seq_show,
  };
  
  static int ac6_seq_open(struct inode *inode, struct file *file)
  {

  	return seq_open_net(inode, file, &ac6_seq_ops,
  			    sizeof(struct ac6_iter_state));

  }

  static const struct file_operations ac6_seq_fops = {

  	.owner		=	THIS_MODULE,
  	.open		=	ac6_seq_open,
  	.read		=	seq_read,
  	.llseek		=	seq_lseek,

  	.release	=	seq_release_net,

  };

  int __net_init ac6_proc_init(struct net *net)

  {

  	if (!proc_net_fops_create(net, "anycast6", S_IRUGO, &ac6_seq_fops))

  		return -ENOMEM;
  
  	return 0;
  }

  void ac6_proc_exit(struct net *net)

  {

  	proc_net_remove(net, "anycast6");

  }
  #endif