// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      Anycast support for IPv6
 *      Linux INET6 implementation
 *
 *      Authors:
 *      David L Stevens (dlstevens@us.ibm.com)
 *
 *      based heavily on net/ipv6/mcast.c
 */

#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>

#define IN6_ADDR_HSIZE_SHIFT    8
#define IN6_ADDR_HSIZE          BIT(IN6_ADDR_HSIZE_SHIFT)
/*      anycast address hash table
 */
static struct hlist_head inet6_acaddr_lst[IN6_ADDR_HSIZE];
static DEFINE_SPINLOCK(acaddr_hash_lock);

#define ac_dereference(a, idev)                                         \
        rcu_dereference_protected(a, lockdep_is_held(&(idev)->lock))

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

static u32 inet6_acaddr_hash(const struct net *net,
                             const struct in6_addr *addr)
{
        u32 val = __ipv6_addr_jhash(addr, net_hash_mix(net));

        return hash_32(val, IN6_ADDR_HSIZE_SHIFT);
}

/*
 *      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 ipv6_ac_socklist *pac = NULL;
        struct net *net = sock_net(sk);
        netdevice_tracker dev_tracker;
        struct net_device *dev = NULL;
        struct inet6_dev *idev;
        int err = 0, ishost;

        if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
                return -EPERM;
        if (ipv6_addr_is_multicast(addr))
                return -EINVAL;

        if (ifindex)
                dev = netdev_get_by_index(net, ifindex, &dev_tracker, GFP_KERNEL);

        if (ipv6_chk_addr_and_flags(net, addr, dev, true, 0, IFA_F_TENTATIVE)) {
                err = -EINVAL;
                goto error;
        }

        pac = sock_kmalloc(sk, sizeof(struct ipv6_ac_socklist), GFP_KERNEL);
        if (!pac) {
                err = -ENOMEM;
                goto error;
        }

        pac->acl_next = NULL;
        pac->acl_addr = *addr;

        ishost = !READ_ONCE(net->ipv6.devconf_all->forwarding);

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

                rcu_read_lock();
                rt = rt6_lookup(net, addr, NULL, 0, NULL, 0);
                if (rt) {
                        dev = dst_dev_rcu(&rt->dst);
                        netdev_hold(dev, &dev_tracker, GFP_ATOMIC);
                        ip6_rt_put(rt);
                } else if (ishost) {
                        rcu_read_unlock();
                        err = -EADDRNOTAVAIL;
                        goto error;
                } else {
                        /* router, no matching interface: just pick one */
                        dev = netdev_get_by_flags_rcu(net, &dev_tracker, IFF_UP,
                                                      IFF_UP | IFF_LOOPBACK);
                }
                rcu_read_unlock();
        }

        if (!dev) {
                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 = !READ_ONCE(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_idev;
        }

        err = __ipv6_dev_ac_inc(idev, addr);
        if (!err) {
                pac->acl_next = np->ipv6_ac_list;
                np->ipv6_ac_list = pac;
                pac = NULL;
        }

error_idev:
        in6_dev_put(idev);
error:
        netdev_put(dev, &dev_tracker);

        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_ac_socklist *pac, *prev_pac;
        struct ipv6_pinfo *np = inet6_sk(sk);
        struct net *net = sock_net(sk);
        struct net_device *dev;

        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)
                return -ENOENT;
        if (prev_pac)
                prev_pac->acl_next = pac->acl_next;
        else
                np->ipv6_ac_list = pac->acl_next;

        dev = dev_get_by_index(net, pac->acl_ifindex);
        if (dev) {
                ipv6_dev_ac_dec(dev, &pac->acl_addr);
                dev_put(dev);
        }

        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 *net = sock_net(sk);
        struct net_device *dev = NULL;
        struct ipv6_ac_socklist *pac;
        int prev_index = 0;

        pac = np->ipv6_ac_list;
        np->ipv6_ac_list = NULL;

        while (pac) {
                struct ipv6_ac_socklist *next = pac->acl_next;

                if (pac->acl_ifindex != prev_index) {
                        dev_put(dev);
                        dev = dev_get_by_index(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;
        }

        dev_put(dev);
}

void ipv6_sock_ac_close(struct sock *sk)
{
        struct ipv6_pinfo *np = inet6_sk(sk);

        if (!np->ipv6_ac_list)
                return;

        __ipv6_sock_ac_close(sk);
}

static void ipv6_add_acaddr_hash(struct net *net, struct ifacaddr6 *aca)
{
        unsigned int hash = inet6_acaddr_hash(net, &aca->aca_addr);

        spin_lock(&acaddr_hash_lock);
        hlist_add_head_rcu(&aca->aca_addr_lst, &inet6_acaddr_lst[hash]);
        spin_unlock(&acaddr_hash_lock);
}

static void ipv6_del_acaddr_hash(struct ifacaddr6 *aca)
{
        spin_lock(&acaddr_hash_lock);
        hlist_del_init_rcu(&aca->aca_addr_lst);
        spin_unlock(&acaddr_hash_lock);
}

static void aca_get(struct ifacaddr6 *aca)
{
        refcount_inc(&aca->aca_refcnt);
}

static void aca_free_rcu(struct rcu_head *h)
{
        struct ifacaddr6 *aca = container_of(h, struct ifacaddr6, rcu);

        fib6_info_release(aca->aca_rt);
        kfree(aca);
}

static void aca_put(struct ifacaddr6 *ac)
{
        if (refcount_dec_and_test(&ac->aca_refcnt))
                call_rcu_hurry(&ac->rcu, aca_free_rcu);
}

static struct ifacaddr6 *aca_alloc(struct fib6_info *f6i,
                                   const struct in6_addr *addr)
{
        struct ifacaddr6 *aca;

        aca = kzalloc_obj(*aca, GFP_ATOMIC);
        if (!aca)
                return NULL;

        aca->aca_addr = *addr;
        fib6_info_hold(f6i);
        aca->aca_rt = f6i;
        INIT_HLIST_NODE(&aca->aca_addr_lst);
        aca->aca_users = 1;
        /* aca_tstamp should be updated upon changes */
        aca->aca_cstamp = aca->aca_tstamp = jiffies;
        refcount_set(&aca->aca_refcnt, 1);

        return aca;
}

static void inet6_ifacaddr_notify(struct net_device *dev,
                                  const struct ifacaddr6 *ifaca, int event)
{
        struct inet6_fill_args fillargs = {
                .event = event,
                .netnsid = -1,
        };
        struct net *net = dev_net(dev);
        struct sk_buff *skb;
        int err = -ENOMEM;

        skb = nlmsg_new(NLMSG_ALIGN(sizeof(struct ifaddrmsg)) +
                        nla_total_size(sizeof(struct in6_addr)) +
                        nla_total_size(sizeof(struct ifa_cacheinfo)),
                        GFP_KERNEL);
        if (!skb)
                goto error;

        err = inet6_fill_ifacaddr(skb, ifaca, &fillargs);
        if (err < 0) {
                pr_err("Failed to fill in anycast addresses (err %d)\n", err);
                nlmsg_free(skb);
                goto error;
        }

        rtnl_notify(skb, net, 0, RTNLGRP_IPV6_ACADDR, NULL, GFP_KERNEL);
        return;
error:
        rtnl_set_sk_err(net, RTNLGRP_IPV6_ACADDR, err);
}

/*
 *      device anycast group inc (add if not found)
 */
int __ipv6_dev_ac_inc(struct inet6_dev *idev, const struct in6_addr *addr)
{
        struct ifacaddr6 *aca;
        struct fib6_info *f6i;
        struct net *net;
        int err;

        write_lock_bh(&idev->lock);
        if (idev->dead) {
                err = -ENODEV;
                goto out;
        }

        for (aca = ac_dereference(idev->ac_list, idev); aca;
             aca = ac_dereference(aca->aca_next, idev)) {
                if (ipv6_addr_equal(&aca->aca_addr, addr)) {
                        aca->aca_users++;
                        err = 0;
                        goto out;
                }
        }

        net = dev_net(idev->dev);
        f6i = addrconf_f6i_alloc(net, idev, addr, true, GFP_ATOMIC, NULL);
        if (IS_ERR(f6i)) {
                err = PTR_ERR(f6i);
                goto out;
        }
        aca = aca_alloc(f6i, addr);
        if (!aca) {
                fib6_info_release(f6i);
                err = -ENOMEM;
                goto out;
        }

        /* Hold this for addrconf_join_solict() below before we unlock,
         * it is already exposed via idev->ac_list.
         */
        aca_get(aca);
        aca->aca_next = idev->ac_list;
        rcu_assign_pointer(idev->ac_list, aca);

        write_unlock_bh(&idev->lock);

        ipv6_add_acaddr_hash(net, aca);

        ip6_ins_rt(net, f6i);

        addrconf_join_solict(idev->dev, &aca->aca_addr);

        inet6_ifacaddr_notify(idev->dev, aca, RTM_NEWANYCAST);

        aca_put(aca);
        return 0;
out:
        write_unlock_bh(&idev->lock);
        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 = ac_dereference(idev->ac_list, idev); aca;
             aca = ac_dereference(aca->aca_next, idev)) {
                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)
                rcu_assign_pointer(prev_aca->aca_next, aca->aca_next);
        else
                rcu_assign_pointer(idev->ac_list, aca->aca_next);
        write_unlock_bh(&idev->lock);
        ipv6_del_acaddr_hash(aca);
        addrconf_leave_solict(idev, &aca->aca_addr);

        ip6_del_rt(dev_net(idev->dev), aca->aca_rt, false);

        inet6_ifacaddr_notify(idev->dev, aca, RTM_DELANYCAST);

        aca_put(aca);
        return 0;
}

static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr)
{
        struct inet6_dev *idev = in6_dev_get(dev);
        int err;

        if (!idev)
                return -ENODEV;

        err = __ipv6_dev_ac_dec(idev, addr);
        in6_dev_put(idev);

        return err;
}

void ipv6_ac_destroy_dev(struct inet6_dev *idev)
{
        struct ifacaddr6 *aca;

        write_lock_bh(&idev->lock);
        while ((aca = ac_dereference(idev->ac_list, idev)) != NULL) {
                rcu_assign_pointer(idev->ac_list, aca->aca_next);
                write_unlock_bh(&idev->lock);

                ipv6_del_acaddr_hash(aca);

                addrconf_leave_solict(idev, &aca->aca_addr);

                ip6_del_rt(dev_net(idev->dev), aca->aca_rt, false);

                aca_put(aca);

                write_lock_bh(&idev->lock);
        }
        write_unlock_bh(&idev->lock);
}

/*
 *      check if the interface has this anycast address
 *      called with rcu_read_lock()
 */
static bool 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) {
                for (aca = rcu_dereference(idev->ac_list); aca;
                     aca = rcu_dereference(aca->aca_next))
                        if (ipv6_addr_equal(&aca->aca_addr, addr))
                                break;
                return aca != NULL;
        }
        return false;
}

/*
 *      check if given interface (or any, if dev==0) has this anycast address
 */
bool ipv6_chk_acast_addr(struct net *net, struct net_device *dev,
                         const struct in6_addr *addr)
{
        struct net_device *nh_dev;
        struct ifacaddr6 *aca;
        bool found = false;

        rcu_read_lock();
        if (dev)
                found = ipv6_chk_acast_dev(dev, addr);
        else {
                unsigned int hash = inet6_acaddr_hash(net, addr);

                hlist_for_each_entry_rcu(aca, &inet6_acaddr_lst[hash],
                                         aca_addr_lst) {
                        nh_dev = fib6_info_nh_dev(aca->aca_rt);
                        if (!nh_dev || !net_eq(dev_net(nh_dev), net))
                                continue;
                        if (ipv6_addr_equal(&aca->aca_addr, addr)) {
                                found = true;
                                break;
                        }
                }
        }
        rcu_read_unlock();
        return found;
}

/*      check if this anycast address is link-local on given interface or
 *      is global
 */
bool ipv6_chk_acast_addr_src(struct net *net, struct net_device *dev,
                             const struct in6_addr *addr)
{
        return ipv6_chk_acast_addr(net,
                                   (ipv6_addr_type(addr) & IPV6_ADDR_LINKLOCAL ?
                                    dev : NULL),
                                   addr);
}

#ifdef CONFIG_PROC_FS
struct ac6_iter_state {
        struct seq_net_private p;
        struct net_device *dev;
};

#define ac6_seq_private(seq)    ((struct ac6_iter_state *)(seq)->private)

static inline struct ifacaddr6 *ac6_get_first(struct seq_file *seq)
{
        struct ac6_iter_state *state = ac6_seq_private(seq);
        struct net *net = seq_file_net(seq);
        struct ifacaddr6 *im = NULL;

        for_each_netdev_rcu(net, state->dev) {
                struct inet6_dev *idev;

                idev = __in6_dev_get(state->dev);
                if (!idev)
                        continue;
                im = rcu_dereference(idev->ac_list);
                if (im)
                        break;
        }
        return im;
}

static struct ifacaddr6 *ac6_get_next(struct seq_file *seq, struct ifacaddr6 *im)
{
        struct ac6_iter_state *state = ac6_seq_private(seq);
        struct inet6_dev *idev;

        im = rcu_dereference(im->aca_next);
        while (!im) {
                state->dev = next_net_device_rcu(state->dev);
                if (!state->dev)
                        break;
                idev = __in6_dev_get(state->dev);
                if (!idev)
                        continue;
                im = rcu_dereference(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)
{
        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\n",
                   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,
};

int __net_init ac6_proc_init(struct net *net)
{
        if (!proc_create_net("anycast6", 0444, net->proc_net, &ac6_seq_ops,
                        sizeof(struct ac6_iter_state)))
                return -ENOMEM;

        return 0;
}

void ac6_proc_exit(struct net *net)
{
        remove_proc_entry("anycast6", net->proc_net);
}
#endif

/*      Init / cleanup code
 */
int __init ipv6_anycast_init(void)
{
        int i;

        for (i = 0; i < IN6_ADDR_HSIZE; i++)
                INIT_HLIST_HEAD(&inet6_acaddr_lst[i]);
        return 0;
}

void ipv6_anycast_cleanup(void)
{
        int i;

        spin_lock(&acaddr_hash_lock);
        for (i = 0; i < IN6_ADDR_HSIZE; i++)
                WARN_ON(!hlist_empty(&inet6_acaddr_lst[i]));
        spin_unlock(&acaddr_hash_lock);
}