// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      IPv6 Address [auto]configuration
 *      Linux INET6 implementation
 *
 *      Authors:
 *      Pedro Roque             <roque@di.fc.ul.pt>
 *      Alexey Kuznetsov        <kuznet@ms2.inr.ac.ru>
 */

/*
 *      Changes:
 *
 *      Janos Farkas                    :       delete timer on ifdown
 *      <chexum@bankinf.banki.hu>
 *      Andi Kleen                      :       kill double kfree on module
 *                                              unload.
 *      Maciej W. Rozycki               :       FDDI support
 *      sekiya@USAGI                    :       Don't send too many RS
 *                                              packets.
 *      yoshfuji@USAGI                  :       Fixed interval between DAD
 *                                              packets.
 *      YOSHIFUJI Hideaki @USAGI        :       improved accuracy of
 *                                              address validation timer.
 *      YOSHIFUJI Hideaki @USAGI        :       Privacy Extensions (RFC3041)
 *                                              support.
 *      Yuji SEKIYA @USAGI              :       Don't assign a same IPv6
 *                                              address on a same interface.
 *      YOSHIFUJI Hideaki @USAGI        :       ARCnet support
 *      YOSHIFUJI Hideaki @USAGI        :       convert /proc/net/if_inet6 to
 *                                              seq_file.
 *      YOSHIFUJI Hideaki @USAGI        :       improved source address
 *                                              selection; consider scope,
 *                                              status etc.
 */

#define pr_fmt(fmt) "IPv6: " fmt

#include <linux/errno.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched/signal.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/in6.h>
#include <linux/netdevice.h>
#include <linux/if_addr.h>
#include <linux/if_arp.h>
#include <linux/if_arcnet.h>
#include <linux/if_infiniband.h>
#include <linux/route.h>
#include <linux/inetdevice.h>
#include <linux/init.h>
#include <linux/slab.h>
#ifdef CONFIG_SYSCTL
#include <linux/sysctl.h>
#endif
#include <linux/capability.h>
#include <linux/delay.h>
#include <linux/notifier.h>
#include <linux/string.h>
#include <linux/hash.h>

#include <net/net_namespace.h>
#include <net/sock.h>
#include <net/snmp.h>

#include <net/6lowpan.h>
#include <net/firewire.h>
#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/ndisc.h>
#include <net/ip6_route.h>
#include <net/addrconf.h>
#include <net/tcp.h>
#include <net/ip.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/l3mdev.h>
#include <linux/if_tunnel.h>
#include <linux/rtnetlink.h>
#include <linux/netconf.h>
#include <linux/random.h>
#include <linux/uaccess.h>
#include <asm/unaligned.h>

#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/export.h>

#define INFINITY_LIFE_TIME      0xFFFFFFFF

#define IPV6_MAX_STRLEN \
        sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255")

static inline u32 cstamp_delta(unsigned long cstamp)
{
        return (cstamp - INITIAL_JIFFIES) * 100UL / HZ;
}

static inline s32 rfc3315_s14_backoff_init(s32 irt)
{
        /* multiply 'initial retransmission time' by 0.9 .. 1.1 */
        u64 tmp = (900000 + prandom_u32() % 200001) * (u64)irt;
        do_div(tmp, 1000000);
        return (s32)tmp;
}

static inline s32 rfc3315_s14_backoff_update(s32 rt, s32 mrt)
{
        /* multiply 'retransmission timeout' by 1.9 .. 2.1 */
        u64 tmp = (1900000 + prandom_u32() % 200001) * (u64)rt;
        do_div(tmp, 1000000);
        if ((s32)tmp > mrt) {
                /* multiply 'maximum retransmission time' by 0.9 .. 1.1 */
                tmp = (900000 + prandom_u32() % 200001) * (u64)mrt;
                do_div(tmp, 1000000);
        }
        return (s32)tmp;
}

#ifdef CONFIG_SYSCTL
static int addrconf_sysctl_register(struct inet6_dev *idev);
static void addrconf_sysctl_unregister(struct inet6_dev *idev);
#else
static inline int addrconf_sysctl_register(struct inet6_dev *idev)
{
        return 0;
}

static inline void addrconf_sysctl_unregister(struct inet6_dev *idev)
{
}
#endif

static void ipv6_gen_rnd_iid(struct in6_addr *addr);

static int ipv6_generate_eui64(u8 *eui, struct net_device *dev);
static int ipv6_count_addresses(const struct inet6_dev *idev);
static int ipv6_generate_stable_address(struct in6_addr *addr,
                                        u8 dad_count,
                                        const struct inet6_dev *idev);

#define IN6_ADDR_HSIZE_SHIFT    8
#define IN6_ADDR_HSIZE          (1 << IN6_ADDR_HSIZE_SHIFT)
/*
 *      Configured unicast address hash table
 */
static struct hlist_head inet6_addr_lst[IN6_ADDR_HSIZE];
static DEFINE_SPINLOCK(addrconf_hash_lock);

static void addrconf_verify(void);
static void addrconf_verify_rtnl(void);
static void addrconf_verify_work(struct work_struct *);

static struct workqueue_struct *addrconf_wq;
static DECLARE_DELAYED_WORK(addr_chk_work, addrconf_verify_work);

static void addrconf_join_anycast(struct inet6_ifaddr *ifp);
static void addrconf_leave_anycast(struct inet6_ifaddr *ifp);

static void addrconf_type_change(struct net_device *dev,
                                 unsigned long event);
static int addrconf_ifdown(struct net_device *dev, bool unregister);

static struct fib6_info *addrconf_get_prefix_route(const struct in6_addr *pfx,
                                                  int plen,
                                                  const struct net_device *dev,
                                                  u32 flags, u32 noflags,
                                                  bool no_gw);

static void addrconf_dad_start(struct inet6_ifaddr *ifp);
static void addrconf_dad_work(struct work_struct *w);
static void addrconf_dad_completed(struct inet6_ifaddr *ifp, bool bump_id,
                                   bool send_na);
static void addrconf_dad_run(struct inet6_dev *idev, bool restart);
static void addrconf_rs_timer(struct timer_list *t);
static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifa);
static void ipv6_ifa_notify(int event, struct inet6_ifaddr *ifa);

static void inet6_prefix_notify(int event, struct inet6_dev *idev,
                                struct prefix_info *pinfo);

static struct ipv6_devconf ipv6_devconf __read_mostly = {
        .forwarding             = 0,
        .hop_limit              = IPV6_DEFAULT_HOPLIMIT,
        .mtu6                   = IPV6_MIN_MTU,
        .accept_ra              = 1,
        .accept_redirects       = 1,
        .autoconf               = 1,
        .force_mld_version      = 0,
        .mldv1_unsolicited_report_interval = 10 * HZ,
        .mldv2_unsolicited_report_interval = HZ,
        .dad_transmits          = 1,
        .rtr_solicits           = MAX_RTR_SOLICITATIONS,
        .rtr_solicit_interval   = RTR_SOLICITATION_INTERVAL,
        .rtr_solicit_max_interval = RTR_SOLICITATION_MAX_INTERVAL,
        .rtr_solicit_delay      = MAX_RTR_SOLICITATION_DELAY,
        .use_tempaddr           = 0,
        .temp_valid_lft         = TEMP_VALID_LIFETIME,
        .temp_prefered_lft      = TEMP_PREFERRED_LIFETIME,
        .regen_max_retry        = REGEN_MAX_RETRY,
        .max_desync_factor      = MAX_DESYNC_FACTOR,
        .max_addresses          = IPV6_MAX_ADDRESSES,
        .accept_ra_defrtr       = 1,
        .ra_defrtr_metric       = IP6_RT_PRIO_USER,
        .accept_ra_from_local   = 0,
        .accept_ra_min_hop_limit= 1,
        .accept_ra_pinfo        = 1,
#ifdef CONFIG_IPV6_ROUTER_PREF
        .accept_ra_rtr_pref     = 1,
        .rtr_probe_interval     = 60 * HZ,
#ifdef CONFIG_IPV6_ROUTE_INFO
        .accept_ra_rt_info_min_plen = 0,
        .accept_ra_rt_info_max_plen = 0,
#endif
#endif
        .proxy_ndp              = 0,
        .accept_source_route    = 0,    /* we do not accept RH0 by default. */
        .disable_ipv6           = 0,
        .accept_dad             = 0,
        .suppress_frag_ndisc    = 1,
        .accept_ra_mtu          = 1,
        .stable_secret          = {
                .initialized = false,
        },
        .use_oif_addrs_only     = 0,
        .ignore_routes_with_linkdown = 0,
        .keep_addr_on_down      = 0,
        .seg6_enabled           = 0,
#ifdef CONFIG_IPV6_SEG6_HMAC
        .seg6_require_hmac      = 0,
#endif
        .enhanced_dad           = 1,
        .addr_gen_mode          = IN6_ADDR_GEN_MODE_EUI64,
        .disable_policy         = 0,
        .rpl_seg_enabled        = 0,
};

static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
        .forwarding             = 0,
        .hop_limit              = IPV6_DEFAULT_HOPLIMIT,
        .mtu6                   = IPV6_MIN_MTU,
        .accept_ra              = 1,
        .accept_redirects       = 1,
        .autoconf               = 1,
        .force_mld_version      = 0,
        .mldv1_unsolicited_report_interval = 10 * HZ,
        .mldv2_unsolicited_report_interval = HZ,
        .dad_transmits          = 1,
        .rtr_solicits           = MAX_RTR_SOLICITATIONS,
        .rtr_solicit_interval   = RTR_SOLICITATION_INTERVAL,
        .rtr_solicit_max_interval = RTR_SOLICITATION_MAX_INTERVAL,
        .rtr_solicit_delay      = MAX_RTR_SOLICITATION_DELAY,
        .use_tempaddr           = 0,
        .temp_valid_lft         = TEMP_VALID_LIFETIME,
        .temp_prefered_lft      = TEMP_PREFERRED_LIFETIME,
        .regen_max_retry        = REGEN_MAX_RETRY,
        .max_desync_factor      = MAX_DESYNC_FACTOR,
        .max_addresses          = IPV6_MAX_ADDRESSES,
        .accept_ra_defrtr       = 1,
        .ra_defrtr_metric       = IP6_RT_PRIO_USER,
        .accept_ra_from_local   = 0,
        .accept_ra_min_hop_limit= 1,
        .accept_ra_pinfo        = 1,
#ifdef CONFIG_IPV6_ROUTER_PREF
        .accept_ra_rtr_pref     = 1,
        .rtr_probe_interval     = 60 * HZ,
#ifdef CONFIG_IPV6_ROUTE_INFO
        .accept_ra_rt_info_min_plen = 0,
        .accept_ra_rt_info_max_plen = 0,
#endif
#endif
        .proxy_ndp              = 0,
        .accept_source_route    = 0,    /* we do not accept RH0 by default. */
        .disable_ipv6           = 0,
        .accept_dad             = 1,
        .suppress_frag_ndisc    = 1,
        .accept_ra_mtu          = 1,
        .stable_secret          = {
                .initialized = false,
        },
        .use_oif_addrs_only     = 0,
        .ignore_routes_with_linkdown = 0,
        .keep_addr_on_down      = 0,
        .seg6_enabled           = 0,
#ifdef CONFIG_IPV6_SEG6_HMAC
        .seg6_require_hmac      = 0,
#endif
        .enhanced_dad           = 1,
        .addr_gen_mode          = IN6_ADDR_GEN_MODE_EUI64,
        .disable_policy         = 0,
        .rpl_seg_enabled        = 0,
};

/* Check if link is ready: is it up and is a valid qdisc available */
static inline bool addrconf_link_ready(const struct net_device *dev)
{
        return netif_oper_up(dev) && !qdisc_tx_is_noop(dev);
}

static void addrconf_del_rs_timer(struct inet6_dev *idev)
{
        if (del_timer(&idev->rs_timer))
                __in6_dev_put(idev);
}

static void addrconf_del_dad_work(struct inet6_ifaddr *ifp)
{
        if (cancel_delayed_work(&ifp->dad_work))
                __in6_ifa_put(ifp);
}

static void addrconf_mod_rs_timer(struct inet6_dev *idev,
                                  unsigned long when)
{
        if (!timer_pending(&idev->rs_timer))
                in6_dev_hold(idev);
        mod_timer(&idev->rs_timer, jiffies + when);
}

static void addrconf_mod_dad_work(struct inet6_ifaddr *ifp,
                                   unsigned long delay)
{
        in6_ifa_hold(ifp);
        if (mod_delayed_work(addrconf_wq, &ifp->dad_work, delay))
                in6_ifa_put(ifp);
}

static int snmp6_alloc_dev(struct inet6_dev *idev)
{
        int i;

        idev->stats.ipv6 = alloc_percpu(struct ipstats_mib);
        if (!idev->stats.ipv6)
                goto err_ip;

        for_each_possible_cpu(i) {
                struct ipstats_mib *addrconf_stats;
                addrconf_stats = per_cpu_ptr(idev->stats.ipv6, i);
                u64_stats_init(&addrconf_stats->syncp);
        }


        idev->stats.icmpv6dev = kzalloc(sizeof(struct icmpv6_mib_device),
                                        GFP_KERNEL);
        if (!idev->stats.icmpv6dev)
                goto err_icmp;
        idev->stats.icmpv6msgdev = kzalloc(sizeof(struct icmpv6msg_mib_device),
                                           GFP_KERNEL);
        if (!idev->stats.icmpv6msgdev)
                goto err_icmpmsg;

        return 0;

err_icmpmsg:
        kfree(idev->stats.icmpv6dev);
err_icmp:
        free_percpu(idev->stats.ipv6);
err_ip:
        return -ENOMEM;
}

static struct inet6_dev *ipv6_add_dev(struct net_device *dev)
{
        struct inet6_dev *ndev;
        int err = -ENOMEM;

        ASSERT_RTNL();

        if (dev->mtu < IPV6_MIN_MTU)
                return ERR_PTR(-EINVAL);

        ndev = kzalloc(sizeof(struct inet6_dev), GFP_KERNEL);
        if (!ndev)
                return ERR_PTR(err);

        rwlock_init(&ndev->lock);
        ndev->dev = dev;
        INIT_LIST_HEAD(&ndev->addr_list);
        timer_setup(&ndev->rs_timer, addrconf_rs_timer, 0);
        memcpy(&ndev->cnf, dev_net(dev)->ipv6.devconf_dflt, sizeof(ndev->cnf));

        if (ndev->cnf.stable_secret.initialized)
                ndev->cnf.addr_gen_mode = IN6_ADDR_GEN_MODE_STABLE_PRIVACY;

        ndev->cnf.mtu6 = dev->mtu;
        ndev->nd_parms = neigh_parms_alloc(dev, &nd_tbl);
        if (!ndev->nd_parms) {
                kfree(ndev);
                return ERR_PTR(err);
        }
        if (ndev->cnf.forwarding)
                dev_disable_lro(dev);
        /* We refer to the device */
        dev_hold(dev);

        if (snmp6_alloc_dev(ndev) < 0) {
                netdev_dbg(dev, "%s: cannot allocate memory for statistics\n",
                           __func__);
                neigh_parms_release(&nd_tbl, ndev->nd_parms);
                dev_put(dev);
                kfree(ndev);
                return ERR_PTR(err);
        }

        if (snmp6_register_dev(ndev) < 0) {
                netdev_dbg(dev, "%s: cannot create /proc/net/dev_snmp6/%s\n",
                           __func__, dev->name);
                goto err_release;
        }

        /* One reference from device. */
        refcount_set(&ndev->refcnt, 1);

        if (dev->flags & (IFF_NOARP | IFF_LOOPBACK))
                ndev->cnf.accept_dad = -1;

#if IS_ENABLED(CONFIG_IPV6_SIT)
        if (dev->type == ARPHRD_SIT && (dev->priv_flags & IFF_ISATAP)) {
                pr_info("%s: Disabled Multicast RS\n", dev->name);
                ndev->cnf.rtr_solicits = 0;
        }
#endif

        INIT_LIST_HEAD(&ndev->tempaddr_list);
        ndev->desync_factor = U32_MAX;
        if ((dev->flags&IFF_LOOPBACK) ||
            dev->type == ARPHRD_TUNNEL ||
            dev->type == ARPHRD_TUNNEL6 ||
            dev->type == ARPHRD_SIT ||
            dev->type == ARPHRD_NONE) {
                ndev->cnf.use_tempaddr = -1;
        }

        ndev->token = in6addr_any;

        if (netif_running(dev) && addrconf_link_ready(dev))
                ndev->if_flags |= IF_READY;

        ipv6_mc_init_dev(ndev);
        ndev->tstamp = jiffies;
        err = addrconf_sysctl_register(ndev);
        if (err) {
                ipv6_mc_destroy_dev(ndev);
                snmp6_unregister_dev(ndev);
                goto err_release;
        }
        /* protected by rtnl_lock */
        rcu_assign_pointer(dev->ip6_ptr, ndev);

        /* Join interface-local all-node multicast group */
        ipv6_dev_mc_inc(dev, &in6addr_interfacelocal_allnodes);

        /* Join all-node multicast group */
        ipv6_dev_mc_inc(dev, &in6addr_linklocal_allnodes);

        /* Join all-router multicast group if forwarding is set */
        if (ndev->cnf.forwarding && (dev->flags & IFF_MULTICAST))
                ipv6_dev_mc_inc(dev, &in6addr_linklocal_allrouters);

        return ndev;

err_release:
        neigh_parms_release(&nd_tbl, ndev->nd_parms);
        ndev->dead = 1;
        in6_dev_finish_destroy(ndev);
        return ERR_PTR(err);
}

static struct inet6_dev *ipv6_find_idev(struct net_device *dev)
{
        struct inet6_dev *idev;

        ASSERT_RTNL();

        idev = __in6_dev_get(dev);
        if (!idev) {
                idev = ipv6_add_dev(dev);
                if (IS_ERR(idev))
                        return idev;
        }

        if (dev->flags&IFF_UP)
                ipv6_mc_up(idev);
        return idev;
}

static int inet6_netconf_msgsize_devconf(int type)
{
        int size =  NLMSG_ALIGN(sizeof(struct netconfmsg))
                    + nla_total_size(4);        /* NETCONFA_IFINDEX */
        bool all = false;

        if (type == NETCONFA_ALL)
                all = true;

        if (all || type == NETCONFA_FORWARDING)
                size += nla_total_size(4);
#ifdef CONFIG_IPV6_MROUTE
        if (all || type == NETCONFA_MC_FORWARDING)
                size += nla_total_size(4);
#endif
        if (all || type == NETCONFA_PROXY_NEIGH)
                size += nla_total_size(4);

        if (all || type == NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN)
                size += nla_total_size(4);

        return size;
}

static int inet6_netconf_fill_devconf(struct sk_buff *skb, int ifindex,
                                      struct ipv6_devconf *devconf, u32 portid,
                                      u32 seq, int event, unsigned int flags,
                                      int type)
{
        struct nlmsghdr  *nlh;
        struct netconfmsg *ncm;
        bool all = false;

        nlh = nlmsg_put(skb, portid, seq, event, sizeof(struct netconfmsg),
                        flags);
        if (!nlh)
                return -EMSGSIZE;

        if (type == NETCONFA_ALL)
                all = true;

        ncm = nlmsg_data(nlh);
        ncm->ncm_family = AF_INET6;

        if (nla_put_s32(skb, NETCONFA_IFINDEX, ifindex) < 0)
                goto nla_put_failure;

        if (!devconf)
                goto out;

        if ((all || type == NETCONFA_FORWARDING) &&
            nla_put_s32(skb, NETCONFA_FORWARDING, devconf->forwarding) < 0)
                goto nla_put_failure;
#ifdef CONFIG_IPV6_MROUTE
        if ((all || type == NETCONFA_MC_FORWARDING) &&
            nla_put_s32(skb, NETCONFA_MC_FORWARDING,
                        devconf->mc_forwarding) < 0)
                goto nla_put_failure;
#endif
        if ((all || type == NETCONFA_PROXY_NEIGH) &&
            nla_put_s32(skb, NETCONFA_PROXY_NEIGH, devconf->proxy_ndp) < 0)
                goto nla_put_failure;

        if ((all || type == NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN) &&
            nla_put_s32(skb, NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN,
                        devconf->ignore_routes_with_linkdown) < 0)
                goto nla_put_failure;

out:
        nlmsg_end(skb, nlh);
        return 0;

nla_put_failure:
        nlmsg_cancel(skb, nlh);
        return -EMSGSIZE;
}

void inet6_netconf_notify_devconf(struct net *net, int event, int type,
                                  int ifindex, struct ipv6_devconf *devconf)
{
        struct sk_buff *skb;
        int err = -ENOBUFS;

        skb = nlmsg_new(inet6_netconf_msgsize_devconf(type), GFP_KERNEL);
        if (!skb)
                goto errout;

        err = inet6_netconf_fill_devconf(skb, ifindex, devconf, 0, 0,
                                         event, 0, type);
        if (err < 0) {
                /* -EMSGSIZE implies BUG in inet6_netconf_msgsize_devconf() */
                WARN_ON(err == -EMSGSIZE);
                kfree_skb(skb);
                goto errout;
        }
        rtnl_notify(skb, net, 0, RTNLGRP_IPV6_NETCONF, NULL, GFP_KERNEL);
        return;
errout:
        rtnl_set_sk_err(net, RTNLGRP_IPV6_NETCONF, err);
}

static const struct nla_policy devconf_ipv6_policy[NETCONFA_MAX+1] = {
        [NETCONFA_IFINDEX]      = { .len = sizeof(int) },
        [NETCONFA_FORWARDING]   = { .len = sizeof(int) },
        [NETCONFA_PROXY_NEIGH]  = { .len = sizeof(int) },
        [NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN]  = { .len = sizeof(int) },
};

static int inet6_netconf_valid_get_req(struct sk_buff *skb,
                                       const struct nlmsghdr *nlh,
                                       struct nlattr **tb,
                                       struct netlink_ext_ack *extack)
{
        int i, err;

        if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(struct netconfmsg))) {
                NL_SET_ERR_MSG_MOD(extack, "Invalid header for netconf get request");
                return -EINVAL;
        }

        if (!netlink_strict_get_check(skb))
                return nlmsg_parse_deprecated(nlh, sizeof(struct netconfmsg),
                                              tb, NETCONFA_MAX,
                                              devconf_ipv6_policy, extack);

        err = nlmsg_parse_deprecated_strict(nlh, sizeof(struct netconfmsg),
                                            tb, NETCONFA_MAX,
                                            devconf_ipv6_policy, extack);
        if (err)
                return err;

        for (i = 0; i <= NETCONFA_MAX; i++) {
                if (!tb[i])
                        continue;

                switch (i) {
                case NETCONFA_IFINDEX:
                        break;
                default:
                        NL_SET_ERR_MSG_MOD(extack, "Unsupported attribute in netconf get request");
                        return -EINVAL;
                }
        }

        return 0;
}

static int inet6_netconf_get_devconf(struct sk_buff *in_skb,
                                     struct nlmsghdr *nlh,
                                     struct netlink_ext_ack *extack)
{
        struct net *net = sock_net(in_skb->sk);
        struct nlattr *tb[NETCONFA_MAX+1];
        struct inet6_dev *in6_dev = NULL;
        struct net_device *dev = NULL;
        struct sk_buff *skb;
        struct ipv6_devconf *devconf;
        int ifindex;
        int err;

        err = inet6_netconf_valid_get_req(in_skb, nlh, tb, extack);
        if (err < 0)
                return err;

        if (!tb[NETCONFA_IFINDEX])
                return -EINVAL;

        err = -EINVAL;
        ifindex = nla_get_s32(tb[NETCONFA_IFINDEX]);
        switch (ifindex) {
        case NETCONFA_IFINDEX_ALL:
                devconf = net->ipv6.devconf_all;
                break;
        case NETCONFA_IFINDEX_DEFAULT:
                devconf = net->ipv6.devconf_dflt;
                break;
        default:
                dev = dev_get_by_index(net, ifindex);
                if (!dev)
                        return -EINVAL;
                in6_dev = in6_dev_get(dev);
                if (!in6_dev)
                        goto errout;
                devconf = &in6_dev->cnf;
                break;
        }

        err = -ENOBUFS;
        skb = nlmsg_new(inet6_netconf_msgsize_devconf(NETCONFA_ALL), GFP_KERNEL);
        if (!skb)
                goto errout;

        err = inet6_netconf_fill_devconf(skb, ifindex, devconf,
                                         NETLINK_CB(in_skb).portid,
                                         nlh->nlmsg_seq, RTM_NEWNETCONF, 0,
                                         NETCONFA_ALL);
        if (err < 0) {
                /* -EMSGSIZE implies BUG in inet6_netconf_msgsize_devconf() */
                WARN_ON(err == -EMSGSIZE);
                kfree_skb(skb);
                goto errout;
        }
        err = rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);
errout:
        if (in6_dev)
                in6_dev_put(in6_dev);
        if (dev)
                dev_put(dev);
        return err;
}

static int inet6_netconf_dump_devconf(struct sk_buff *skb,
                                      struct netlink_callback *cb)
{
        const struct nlmsghdr *nlh = cb->nlh;
        struct net *net = sock_net(skb->sk);
        int h, s_h;
        int idx, s_idx;
        struct net_device *dev;
        struct inet6_dev *idev;
        struct hlist_head *head;

        if (cb->strict_check) {
                struct netlink_ext_ack *extack = cb->extack;
                struct netconfmsg *ncm;

                if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*ncm))) {
                        NL_SET_ERR_MSG_MOD(extack, "Invalid header for netconf dump request");
                        return -EINVAL;
                }

                if (nlmsg_attrlen(nlh, sizeof(*ncm))) {
                        NL_SET_ERR_MSG_MOD(extack, "Invalid data after header in netconf dump request");
                        return -EINVAL;
                }
        }

        s_h = cb->args[0];
        s_idx = idx = cb->args[1];

        for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
                idx = 0;
                head = &net->dev_index_head[h];
                rcu_read_lock();
                cb->seq = atomic_read(&net->ipv6.dev_addr_genid) ^
                          net->dev_base_seq;
                hlist_for_each_entry_rcu(dev, head, index_hlist) {
                        if (idx < s_idx)
                                goto cont;
                        idev = __in6_dev_get(dev);
                        if (!idev)
                                goto cont;

                        if (inet6_netconf_fill_devconf(skb, dev->ifindex,
                                                       &idev->cnf,
                                                       NETLINK_CB(cb->skb).portid,
                                                       nlh->nlmsg_seq,
                                                       RTM_NEWNETCONF,
                                                       NLM_F_MULTI,
                                                       NETCONFA_ALL) < 0) {
                                rcu_read_unlock();
                                goto done;
                        }
                        nl_dump_check_consistent(cb, nlmsg_hdr(skb));
cont:
                        idx++;
                }
                rcu_read_unlock();
        }
        if (h == NETDEV_HASHENTRIES) {
                if (inet6_netconf_fill_devconf(skb, NETCONFA_IFINDEX_ALL,
                                               net->ipv6.devconf_all,
                                               NETLINK_CB(cb->skb).portid,
                                               nlh->nlmsg_seq,
                                               RTM_NEWNETCONF, NLM_F_MULTI,
                                               NETCONFA_ALL) < 0)
                        goto done;
                else
                        h++;
        }
        if (h == NETDEV_HASHENTRIES + 1) {
                if (inet6_netconf_fill_devconf(skb, NETCONFA_IFINDEX_DEFAULT,
                                               net->ipv6.devconf_dflt,
                                               NETLINK_CB(cb->skb).portid,
                                               nlh->nlmsg_seq,
                                               RTM_NEWNETCONF, NLM_F_MULTI,
                                               NETCONFA_ALL) < 0)
                        goto done;
                else
                        h++;
        }
done:
        cb->args[0] = h;
        cb->args[1] = idx;

        return skb->len;
}

#ifdef CONFIG_SYSCTL
static void dev_forward_change(struct inet6_dev *idev)
{
        struct net_device *dev;
        struct inet6_ifaddr *ifa;

        if (!idev)
                return;
        dev = idev->dev;
        if (idev->cnf.forwarding)
                dev_disable_lro(dev);
        if (dev->flags & IFF_MULTICAST) {
                if (idev->cnf.forwarding) {
                        ipv6_dev_mc_inc(dev, &in6addr_linklocal_allrouters);
                        ipv6_dev_mc_inc(dev, &in6addr_interfacelocal_allrouters);
                        ipv6_dev_mc_inc(dev, &in6addr_sitelocal_allrouters);
                } else {
                        ipv6_dev_mc_dec(dev, &in6addr_linklocal_allrouters);
                        ipv6_dev_mc_dec(dev, &in6addr_interfacelocal_allrouters);
                        ipv6_dev_mc_dec(dev, &in6addr_sitelocal_allrouters);
                }
        }

        list_for_each_entry(ifa, &idev->addr_list, if_list) {
                if (ifa->flags&IFA_F_TENTATIVE)
                        continue;
                if (idev->cnf.forwarding)
                        addrconf_join_anycast(ifa);
                else
                        addrconf_leave_anycast(ifa);
        }
        inet6_netconf_notify_devconf(dev_net(dev), RTM_NEWNETCONF,
                                     NETCONFA_FORWARDING,
                                     dev->ifindex, &idev->cnf);
}


static void addrconf_forward_change(struct net *net, __s32 newf)
{
        struct net_device *dev;
        struct inet6_dev *idev;

        for_each_netdev(net, dev) {
                idev = __in6_dev_get(dev);
                if (idev) {
                        int changed = (!idev->cnf.forwarding) ^ (!newf);
                        idev->cnf.forwarding = newf;
                        if (changed)
                                dev_forward_change(idev);
                }
        }
}

static int addrconf_fixup_forwarding(struct ctl_table *table, int *p, int newf)
{
        struct net *net;
        int old;

        if (!rtnl_trylock())
                return restart_syscall();

        net = (struct net *)table->extra2;
        old = *p;
        *p = newf;

        if (p == &net->ipv6.devconf_dflt->forwarding) {
                if ((!newf) ^ (!old))
                        inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,
                                                     NETCONFA_FORWARDING,
                                                     NETCONFA_IFINDEX_DEFAULT,
                                                     net->ipv6.devconf_dflt);
                rtnl_unlock();
                return 0;
        }

        if (p == &net->ipv6.devconf_all->forwarding) {
                int old_dflt = net->ipv6.devconf_dflt->forwarding;

                net->ipv6.devconf_dflt->forwarding = newf;
                if ((!newf) ^ (!old_dflt))
                        inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,
                                                     NETCONFA_FORWARDING,
                                                     NETCONFA_IFINDEX_DEFAULT,
                                                     net->ipv6.devconf_dflt);

                addrconf_forward_change(net, newf);
                if ((!newf) ^ (!old))
                        inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,
                                                     NETCONFA_FORWARDING,
                                                     NETCONFA_IFINDEX_ALL,
                                                     net->ipv6.devconf_all);
        } else if ((!newf) ^ (!old))
                dev_forward_change((struct inet6_dev *)table->extra1);
        rtnl_unlock();

        if (newf)
                rt6_purge_dflt_routers(net);
        return 1;
}

static void addrconf_linkdown_change(struct net *net, __s32 newf)
{
        struct net_device *dev;
        struct inet6_dev *idev;

        for_each_netdev(net, dev) {
                idev = __in6_dev_get(dev);
                if (idev) {
                        int changed = (!idev->cnf.ignore_routes_with_linkdown) ^ (!newf);

                        idev->cnf.ignore_routes_with_linkdown = newf;
                        if (changed)
                                inet6_netconf_notify_devconf(dev_net(dev),
                                                             RTM_NEWNETCONF,
                                                             NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN,
                                                             dev->ifindex,
                                                             &idev->cnf);
                }
        }
}

static int addrconf_fixup_linkdown(struct ctl_table *table, int *p, int newf)
{
        struct net *net;
        int old;

        if (!rtnl_trylock())
                return restart_syscall();

        net = (struct net *)table->extra2;
        old = *p;
        *p = newf;

        if (p == &net->ipv6.devconf_dflt->ignore_routes_with_linkdown) {
                if ((!newf) ^ (!old))
                        inet6_netconf_notify_devconf(net,
                                                     RTM_NEWNETCONF,
                                                     NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN,
                                                     NETCONFA_IFINDEX_DEFAULT,
                                                     net->ipv6.devconf_dflt);
                rtnl_unlock();
                return 0;
        }

        if (p == &net->ipv6.devconf_all->ignore_routes_with_linkdown) {
                net->ipv6.devconf_dflt->ignore_routes_with_linkdown = newf;
                addrconf_linkdown_change(net, newf);
                if ((!newf) ^ (!old))
                        inet6_netconf_notify_devconf(net,
                                                     RTM_NEWNETCONF,
                                                     NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN,
                                                     NETCONFA_IFINDEX_ALL,
                                                     net->ipv6.devconf_all);
        }
        rtnl_unlock();

        return 1;
}

#endif

/* Nobody refers to this ifaddr, destroy it */
void inet6_ifa_finish_destroy(struct inet6_ifaddr *ifp)
{
        WARN_ON(!hlist_unhashed(&ifp->addr_lst));

#ifdef NET_REFCNT_DEBUG
        pr_debug("%s\n", __func__);
#endif

        in6_dev_put(ifp->idev);

        if (cancel_delayed_work(&ifp->dad_work))
                pr_notice("delayed DAD work was pending while freeing ifa=%p\n",
                          ifp);

        if (ifp->state != INET6_IFADDR_STATE_DEAD) {
                pr_warn("Freeing alive inet6 address %p\n", ifp);
                return;
        }

        kfree_rcu(ifp, rcu);
}

static void
ipv6_link_dev_addr(struct inet6_dev *idev, struct inet6_ifaddr *ifp)
{
        struct list_head *p;
        int ifp_scope = ipv6_addr_src_scope(&ifp->addr);

        /*
         * Each device address list is sorted in order of scope -
         * global before linklocal.
         */
        list_for_each(p, &idev->addr_list) {
                struct inet6_ifaddr *ifa
                        = list_entry(p, struct inet6_ifaddr, if_list);
                if (ifp_scope >= ipv6_addr_src_scope(&ifa->addr))
                        break;
        }

        list_add_tail_rcu(&ifp->if_list, p);
}

static u32 inet6_addr_hash(const struct net *net, const struct in6_addr *addr)
{
        u32 val = ipv6_addr_hash(addr) ^ net_hash_mix(net);

        return hash_32(val, IN6_ADDR_HSIZE_SHIFT);
}

static bool ipv6_chk_same_addr(struct net *net, const struct in6_addr *addr,

                               struct net_device *dev, unsigned int hash)
{
        struct inet6_ifaddr *ifp;

        hlist_for_each_entry(ifp, &inet6_addr_lst[hash], addr_lst) {
                if (!net_eq(dev_net(ifp->idev->dev), net))
                        continue;
                if (ipv6_addr_equal(&ifp->addr, addr)) {
                        if (!dev || ifp->idev->dev == dev)
                                return true;
                }
        }
        return false;
}

static int ipv6_add_addr_hash(struct net_device *dev, struct inet6_ifaddr *ifa)
{
        unsigned int hash = inet6_addr_hash(dev_net(dev), &ifa->addr);
        int err = 0;

        spin_lock(&addrconf_hash_lock);

        /* Ignore adding duplicate addresses on an interface */
        if (ipv6_chk_same_addr(dev_net(dev), &ifa->addr, dev, hash)) {
                netdev_dbg(dev, "ipv6_add_addr: already assigned\n");
                err = -EEXIST;
        } else {
                hlist_add_head_rcu(&ifa->addr_lst, &inet6_addr_lst[hash]);
        }

        spin_unlock(&addrconf_hash_lock);

        return err;
}

/* On success it returns ifp with increased reference count */

static struct inet6_ifaddr *
ipv6_add_addr(struct inet6_dev *idev, struct ifa6_config *cfg,
              bool can_block, struct netlink_ext_ack *extack)
{
        gfp_t gfp_flags = can_block ? GFP_KERNEL : GFP_ATOMIC;
        int addr_type = ipv6_addr_type(cfg->pfx);
        struct net *net = dev_net(idev->dev);
        struct inet6_ifaddr *ifa = NULL;
        struct fib6_info *f6i = NULL;
        int err = 0;

        if (addr_type == IPV6_ADDR_ANY ||
            (addr_type & IPV6_ADDR_MULTICAST &&
             !(cfg->ifa_flags & IFA_F_MCAUTOJOIN)) ||
            (!(idev->dev->flags & IFF_LOOPBACK) &&
             !netif_is_l3_master(idev->dev) &&
             addr_type & IPV6_ADDR_LOOPBACK))
                return ERR_PTR(-EADDRNOTAVAIL);

        if (idev->dead) {
                err = -ENODEV;                  /*XXX*/
                goto out;
        }

        if (idev->cnf.disable_ipv6) {
                err = -EACCES;
                goto out;
        }

        /* validator notifier needs to be blocking;
         * do not call in atomic context
         */
        if (can_block) {
                struct in6_validator_info i6vi = {
                        .i6vi_addr = *cfg->pfx,
                        .i6vi_dev = idev,
                        .extack = extack,
                };

                err = inet6addr_validator_notifier_call_chain(NETDEV_UP, &i6vi);
                err = notifier_to_errno(err);
                if (err < 0)
                        goto out;
        }

        ifa = kzalloc(sizeof(*ifa), gfp_flags);
        if (!ifa) {
                err = -ENOBUFS;
                goto out;
        }

        f6i = addrconf_f6i_alloc(net, idev, cfg->pfx, false, gfp_flags);
        if (IS_ERR(f6i)) {
                err = PTR_ERR(f6i);
                f6i = NULL;
                goto out;
        }

        if (net->ipv6.devconf_all->disable_policy ||
            idev->cnf.disable_policy)
                f6i->dst_nopolicy = true;

        neigh_parms_data_state_setall(idev->nd_parms);

        ifa->addr = *cfg->pfx;
        if (cfg->peer_pfx)
                ifa->peer_addr = *cfg->peer_pfx;

        spin_lock_init(&ifa->lock);
        INIT_DELAYED_WORK(&ifa->dad_work, addrconf_dad_work);
        INIT_HLIST_NODE(&ifa->addr_lst);
        ifa->scope = cfg->scope;
        ifa->prefix_len = cfg->plen;
        ifa->rt_priority = cfg->rt_priority;
        ifa->flags = cfg->ifa_flags;
        /* No need to add the TENTATIVE flag for addresses with NODAD */
        if (!(cfg->ifa_flags & IFA_F_NODAD))
                ifa->flags |= IFA_F_TENTATIVE;
        ifa->valid_lft = cfg->valid_lft;
        ifa->prefered_lft = cfg->preferred_lft;
        ifa->cstamp = ifa->tstamp = jiffies;
        ifa->tokenized = false;

        ifa->rt = f6i;

        ifa->idev = idev;
        in6_dev_hold(idev);

        /* For caller */
        refcount_set(&ifa->refcnt, 1);

        rcu_read_lock_bh();

        err = ipv6_add_addr_hash(idev->dev, ifa);
        if (err < 0) {
                rcu_read_unlock_bh();
                goto out;
        }

        write_lock(&idev->lock);

        /* Add to inet6_dev unicast addr list. */
        ipv6_link_dev_addr(idev, ifa);

        if (ifa->flags&IFA_F_TEMPORARY) {
                list_add(&ifa->tmp_list, &idev->tempaddr_list);
                in6_ifa_hold(ifa);
        }

        in6_ifa_hold(ifa);
        write_unlock(&idev->lock);

        rcu_read_unlock_bh();

        inet6addr_notifier_call_chain(NETDEV_UP, ifa);
out:
        if (unlikely(err < 0)) {
                fib6_info_release(f6i);

                if (ifa) {
                        if (ifa->idev)
                                in6_dev_put(ifa->idev);
                        kfree(ifa);
                }
                ifa = ERR_PTR(err);
        }

        return ifa;
}

enum cleanup_prefix_rt_t {
        CLEANUP_PREFIX_RT_NOP,    /* no cleanup action for prefix route */
        CLEANUP_PREFIX_RT_DEL,    /* delete the prefix route */
        CLEANUP_PREFIX_RT_EXPIRE, /* update the lifetime of the prefix route */
};

/*
 * Check, whether the prefix for ifp would still need a prefix route
 * after deleting ifp. The function returns one of the CLEANUP_PREFIX_RT_*
 * constants.
 *
 * 1) we don't purge prefix if address was not permanent.
 *    prefix is managed by its own lifetime.
 * 2) we also don't purge, if the address was IFA_F_NOPREFIXROUTE.
 * 3) if there are no addresses, delete prefix.
 * 4) if there are still other permanent address(es),
 *    corresponding prefix is still permanent.
 * 5) if there are still other addresses with IFA_F_NOPREFIXROUTE,
 *    don't purge the prefix, assume user space is managing it.
 * 6) otherwise, update prefix lifetime to the
 *    longest valid lifetime among the corresponding
 *    addresses on the device.
 *    Note: subsequent RA will update lifetime.
 **/
static enum cleanup_prefix_rt_t
check_cleanup_prefix_route(struct inet6_ifaddr *ifp, unsigned long *expires)
{
        struct inet6_ifaddr *ifa;
        struct inet6_dev *idev = ifp->idev;
        unsigned long lifetime;
        enum cleanup_prefix_rt_t action = CLEANUP_PREFIX_RT_DEL;

        *expires = jiffies;

        list_for_each_entry(ifa, &idev->addr_list, if_list) {
                if (ifa == ifp)
                        continue;
                if (ifa->prefix_len != ifp->prefix_len ||
                    !ipv6_prefix_equal(&ifa->addr, &ifp->addr,
                                       ifp->prefix_len))
                        continue;
                if (ifa->flags & (IFA_F_PERMANENT | IFA_F_NOPREFIXROUTE))
                        return CLEANUP_PREFIX_RT_NOP;

                action = CLEANUP_PREFIX_RT_EXPIRE;

                spin_lock(&ifa->lock);

                lifetime = addrconf_timeout_fixup(ifa->valid_lft, HZ);
                /*
                 * Note: Because this address is
                 * not permanent, lifetime <
                 * LONG_MAX / HZ here.
                 */
                if (time_before(*expires, ifa->tstamp + lifetime * HZ))
                        *expires = ifa->tstamp + lifetime * HZ;
                spin_unlock(&ifa->lock);
        }

        return action;
}

static void
cleanup_prefix_route(struct inet6_ifaddr *ifp, unsigned long expires,
                     bool del_rt, bool del_peer)
{
        struct fib6_info *f6i;

        f6i = addrconf_get_prefix_route(del_peer ? &ifp->peer_addr : &ifp->addr,
                                        ifp->prefix_len,
                                        ifp->idev->dev, 0, RTF_DEFAULT, true);
        if (f6i) {
                if (del_rt)
                        ip6_del_rt(dev_net(ifp->idev->dev), f6i, false);
                else {
                        if (!(f6i->fib6_flags & RTF_EXPIRES))
                                fib6_set_expires(f6i, expires);
                        fib6_info_release(f6i);
                }
        }
}


/* This function wants to get referenced ifp and releases it before return */

static void ipv6_del_addr(struct inet6_ifaddr *ifp)
{
        int state;
        enum cleanup_prefix_rt_t action = CLEANUP_PREFIX_RT_NOP;
        unsigned long expires;

        ASSERT_RTNL();

        spin_lock_bh(&ifp->lock);
        state = ifp->state;
        ifp->state = INET6_IFADDR_STATE_DEAD;
        spin_unlock_bh(&ifp->lock);

        if (state == INET6_IFADDR_STATE_DEAD)
                goto out;

        spin_lock_bh(&addrconf_hash_lock);
        hlist_del_init_rcu(&ifp->addr_lst);
        spin_unlock_bh(&addrconf_hash_lock);

        write_lock_bh(&ifp->idev->lock);

        if (ifp->flags&IFA_F_TEMPORARY) {
                list_del(&ifp->tmp_list);
                if (ifp->ifpub) {
                        in6_ifa_put(ifp->ifpub);
                        ifp->ifpub = NULL;
                }
                __in6_ifa_put(ifp);
        }

        if (ifp->flags & IFA_F_PERMANENT && !(ifp->flags & IFA_F_NOPREFIXROUTE))
                action = check_cleanup_prefix_route(ifp, &expires);

        list_del_rcu(&ifp->if_list);
        __in6_ifa_put(ifp);

        write_unlock_bh(&ifp->idev->lock);

        addrconf_del_dad_work(ifp);

        ipv6_ifa_notify(RTM_DELADDR, ifp);

        inet6addr_notifier_call_chain(NETDEV_DOWN, ifp);

        if (action != CLEANUP_PREFIX_RT_NOP) {
                cleanup_prefix_route(ifp, expires,
                        action == CLEANUP_PREFIX_RT_DEL, false);
        }

        /* clean up prefsrc entries */
        rt6_remove_prefsrc(ifp);
out:
        in6_ifa_put(ifp);
}

static int ipv6_create_tempaddr(struct inet6_ifaddr *ifp, bool block)
{
        struct inet6_dev *idev = ifp->idev;
        unsigned long tmp_tstamp, age;
        unsigned long regen_advance;
        unsigned long now = jiffies;
        s32 cnf_temp_preferred_lft;
        struct inet6_ifaddr *ift;
        struct ifa6_config cfg;
        long max_desync_factor;
        struct in6_addr addr;
        int ret = 0;

        write_lock_bh(&idev->lock);

retry:
        in6_dev_hold(idev);
        if (idev->cnf.use_tempaddr <= 0) {
                write_unlock_bh(&idev->lock);
                pr_info("%s: use_tempaddr is disabled\n", __func__);
                in6_dev_put(idev);
                ret = -1;
                goto out;
        }
        spin_lock_bh(&ifp->lock);
        if (ifp->regen_count++ >= idev->cnf.regen_max_retry) {
                idev->cnf.use_tempaddr = -1;    /*XXX*/
                spin_unlock_bh(&ifp->lock);
                write_unlock_bh(&idev->lock);
                pr_warn("%s: regeneration time exceeded - disabled temporary address support\n",
                        __func__);
                in6_dev_put(idev);
                ret = -1;
                goto out;
        }
        in6_ifa_hold(ifp);
        memcpy(addr.s6_addr, ifp->addr.s6_addr, 8);
        ipv6_gen_rnd_iid(&addr);

        age = (now - ifp->tstamp) / HZ;

        regen_advance = idev->cnf.regen_max_retry *
                        idev->cnf.dad_transmits *
                        max(NEIGH_VAR(idev->nd_parms, RETRANS_TIME), HZ/100) / HZ;

        /* recalculate max_desync_factor each time and update
         * idev->desync_factor if it's larger
         */
        cnf_temp_preferred_lft = READ_ONCE(idev->cnf.temp_prefered_lft);
        max_desync_factor = min_t(__u32,
                                  idev->cnf.max_desync_factor,
                                  cnf_temp_preferred_lft - regen_advance);

        if (unlikely(idev->desync_factor > max_desync_factor)) {
                if (max_desync_factor > 0) {
                        get_random_bytes(&idev->desync_factor,
                                         sizeof(idev->desync_factor));
                        idev->desync_factor %= max_desync_factor;
                } else {
                        idev->desync_factor = 0;
                }
        }

        memset(&cfg, 0, sizeof(cfg));
        cfg.valid_lft = min_t(__u32, ifp->valid_lft,
                              idev->cnf.temp_valid_lft + age);
        cfg.preferred_lft = cnf_temp_preferred_lft + age - idev->desync_factor;
        cfg.preferred_lft = min_t(__u32, ifp->prefered_lft, cfg.preferred_lft);

        cfg.plen = ifp->prefix_len;
        tmp_tstamp = ifp->tstamp;
        spin_unlock_bh(&ifp->lock);

        write_unlock_bh(&idev->lock);

        /* A temporary address is created only if this calculated Preferred
         * Lifetime is greater than REGEN_ADVANCE time units.  In particular,
         * an implementation must not create a temporary address with a zero
         * Preferred Lifetime.
         * Use age calculation as in addrconf_verify to avoid unnecessary
         * temporary addresses being generated.
         */
        age = (now - tmp_tstamp + ADDRCONF_TIMER_FUZZ_MINUS) / HZ;
        if (cfg.preferred_lft <= regen_advance + age) {
                in6_ifa_put(ifp);
                in6_dev_put(idev);
                ret = -1;
                goto out;
        }

        cfg.ifa_flags = IFA_F_TEMPORARY;
        /* set in addrconf_prefix_rcv() */
        if (ifp->flags & IFA_F_OPTIMISTIC)
                cfg.ifa_flags |= IFA_F_OPTIMISTIC;

        cfg.pfx = &addr;
        cfg.scope = ipv6_addr_scope(cfg.pfx);

        ift = ipv6_add_addr(idev, &cfg, block, NULL);
        if (IS_ERR(ift)) {
                in6_ifa_put(ifp);
                in6_dev_put(idev);
                pr_info("%s: retry temporary address regeneration\n", __func__);
                write_lock_bh(&idev->lock);
                goto retry;
        }

        spin_lock_bh(&ift->lock);
        ift->ifpub = ifp;
        ift->cstamp = now;
        ift->tstamp = tmp_tstamp;
        spin_unlock_bh(&ift->lock);

        addrconf_dad_start(ift);
        in6_ifa_put(ift);
        in6_dev_put(idev);
out:
        return ret;
}

/*
 *      Choose an appropriate source address (RFC3484)
 */
enum {
        IPV6_SADDR_RULE_INIT = 0,
        IPV6_SADDR_RULE_LOCAL,
        IPV6_SADDR_RULE_SCOPE,
        IPV6_SADDR_RULE_PREFERRED,
#ifdef CONFIG_IPV6_MIP6
        IPV6_SADDR_RULE_HOA,
#endif
        IPV6_SADDR_RULE_OIF,
        IPV6_SADDR_RULE_LABEL,
        IPV6_SADDR_RULE_PRIVACY,
        IPV6_SADDR_RULE_ORCHID,
        IPV6_SADDR_RULE_PREFIX,
#ifdef CONFIG_IPV6_OPTIMISTIC_DAD
        IPV6_SADDR_RULE_NOT_OPTIMISTIC,
#endif
        IPV6_SADDR_RULE_MAX
};

struct ipv6_saddr_score {
        int                     rule;
        int                     addr_type;
        struct inet6_ifaddr     *ifa;
        DECLARE_BITMAP(scorebits, IPV6_SADDR_RULE_MAX);
        int                     scopedist;
        int                     matchlen;
};

struct ipv6_saddr_dst {
        const struct in6_addr *addr;
        int ifindex;
        int scope;
        int label;
        unsigned int prefs;
};

static inline int ipv6_saddr_preferred(int type)
{
        if (type & (IPV6_ADDR_MAPPED|IPV6_ADDR_COMPATv4|IPV6_ADDR_LOOPBACK))
                return 1;
        return 0;
}

static bool ipv6_use_optimistic_addr(struct net *net,
                                     struct inet6_dev *idev)
{
#ifdef CONFIG_IPV6_OPTIMISTIC_DAD
        if (!idev)
                return false;
        if (!net->ipv6.devconf_all->optimistic_dad && !idev->cnf.optimistic_dad)
                return false;
        if (!net->ipv6.devconf_all->use_optimistic && !idev->cnf.use_optimistic)
                return false;

        return true;
#else
        return false;
#endif
}

static bool ipv6_allow_optimistic_dad(struct net *net,
                                      struct inet6_dev *idev)
{
#ifdef CONFIG_IPV6_OPTIMISTIC_DAD
        if (!idev)
                return false;
        if (!net->ipv6.devconf_all->optimistic_dad && !idev->cnf.optimistic_dad)
                return false;

        return true;
#else
        return false;
#endif
}

static int ipv6_get_saddr_eval(struct net *net,
                               struct ipv6_saddr_score *score,
                               struct ipv6_saddr_dst *dst,
                               int i)
{
        int ret;

        if (i <= score->rule) {
                switch (i) {
                case IPV6_SADDR_RULE_SCOPE:
                        ret = score->scopedist;
                        break;
                case IPV6_SADDR_RULE_PREFIX:
                        ret = score->matchlen;
                        break;
                default:
                        ret = !!test_bit(i, score->scorebits);
                }
                goto out;
        }

        switch (i) {
        case IPV6_SADDR_RULE_INIT:
                /* Rule 0: remember if hiscore is not ready yet */
                ret = !!score->ifa;
                break;
        case IPV6_SADDR_RULE_LOCAL:
                /* Rule 1: Prefer same address */
                ret = ipv6_addr_equal(&score->ifa->addr, dst->addr);
                break;
        case IPV6_SADDR_RULE_SCOPE:
                /* Rule 2: Prefer appropriate scope
                 *
                 *      ret
                 *       ^
                 *    -1 |  d 15
                 *    ---+--+-+---> scope
                 *       |
                 *       |             d is scope of the destination.
                 *  B-d  |  \
                 *       |   \      <- smaller scope is better if
                 *  B-15 |    \        if scope is enough for destination.
                 *       |             ret = B - scope (-1 <= scope >= d <= 15).
                 * d-C-1 | /
                 *       |/         <- greater is better
                 *   -C  /             if scope is not enough for destination.
                 *      /|             ret = scope - C (-1 <= d < scope <= 15).
                 *
                 * d - C - 1 < B -15 (for all -1 <= d <= 15).
                 * C > d + 14 - B >= 15 + 14 - B = 29 - B.
                 * Assume B = 0 and we get C > 29.
                 */
                ret = __ipv6_addr_src_scope(score->addr_type);
                if (ret >= dst->scope)
                        ret = -ret;
                else
                        ret -= 128;     /* 30 is enough */
                score->scopedist = ret;
                break;
        case IPV6_SADDR_RULE_PREFERRED:
            {
                /* Rule 3: Avoid deprecated and optimistic addresses */
                u8 avoid = IFA_F_DEPRECATED;

                if (!ipv6_use_optimistic_addr(net, score->ifa->idev))
                        avoid |= IFA_F_OPTIMISTIC;
                ret = ipv6_saddr_preferred(score->addr_type) ||
                      !(score->ifa->flags & avoid);
                break;
            }
#ifdef CONFIG_IPV6_MIP6
        case IPV6_SADDR_RULE_HOA:
            {
                /* Rule 4: Prefer home address */
                int prefhome = !(dst->prefs & IPV6_PREFER_SRC_COA);
                ret = !(score->ifa->flags & IFA_F_HOMEADDRESS) ^ prefhome;
                break;
            }
#endif
        case IPV6_SADDR_RULE_OIF:
                /* Rule 5: Prefer outgoing interface */
                ret = (!dst->ifindex ||
                       dst->ifindex == score->ifa->idev->dev->ifindex);
                break;
        case IPV6_SADDR_RULE_LABEL:
                /* Rule 6: Prefer matching label */
                ret = ipv6_addr_label(net,
                                      &score->ifa->addr, score->addr_type,
                                      score->ifa->idev->dev->ifindex) == dst->label;
                break;
        case IPV6_SADDR_RULE_PRIVACY:
            {
                /* Rule 7: Prefer public address
                 * Note: prefer temporary address if use_tempaddr >= 2
                 */
                int preftmp = dst->prefs & (IPV6_PREFER_SRC_PUBLIC|IPV6_PREFER_SRC_TMP) ?
                                !!(dst->prefs & IPV6_PREFER_SRC_TMP) :
                                score->ifa->idev->cnf.use_tempaddr >= 2;
                ret = (!(score->ifa->flags & IFA_F_TEMPORARY)) ^ preftmp;
                break;
            }
        case IPV6_SADDR_RULE_ORCHID:
                /* Rule 8-: Prefer ORCHID vs ORCHID or
                 *          non-ORCHID vs non-ORCHID
                 */
                ret = !(ipv6_addr_orchid(&score->ifa->addr) ^
                        ipv6_addr_orchid(dst->addr));
                break;
        case IPV6_SADDR_RULE_PREFIX:
                /* Rule 8: Use longest matching prefix */
                ret = ipv6_addr_diff(&score->ifa->addr, dst->addr);
                if (ret > score->ifa->prefix_len)
                        ret = score->ifa->prefix_len;
                score->matchlen = ret;
                break;
#ifdef CONFIG_IPV6_OPTIMISTIC_DAD
        case IPV6_SADDR_RULE_NOT_OPTIMISTIC:
                /* Optimistic addresses still have lower precedence than other
                 * preferred addresses.
                 */
                ret = !(score->ifa->flags & IFA_F_OPTIMISTIC);
                break;
#endif
        default:
                ret = 0;
        }

        if (ret)
                __set_bit(i, score->scorebits);
        score->rule = i;
out:
        return ret;
}

static int __ipv6_dev_get_saddr(struct net *net,
                                struct ipv6_saddr_dst *dst,
                                struct inet6_dev *idev,
                                struct ipv6_saddr_score *scores,
                                int hiscore_idx)
{
        struct ipv6_saddr_score *score = &scores[1 - hiscore_idx], *hiscore = &scores[hiscore_idx];

        list_for_each_entry_rcu(score->ifa, &idev->addr_list, if_list) {
                int i;

                /*
                 * - Tentative Address (RFC2462 section 5.4)
                 *  - A tentative address is not considered
                 *    "assigned to an interface" in the traditional
                 *    sense, unless it is also flagged as optimistic.
                 * - Candidate Source Address (section 4)
                 *  - In any case, anycast addresses, multicast
                 *    addresses, and the unspecified address MUST
                 *    NOT be included in a candidate set.
                 */
                if ((score->ifa->flags & IFA_F_TENTATIVE) &&
                    (!(score->ifa->flags & IFA_F_OPTIMISTIC)))
                        continue;

                score->addr_type = __ipv6_addr_type(&score->ifa->addr);

                if (unlikely(score->addr_type == IPV6_ADDR_ANY ||
                             score->addr_type & IPV6_ADDR_MULTICAST)) {
                        net_dbg_ratelimited("ADDRCONF: unspecified / multicast address assigned as unicast address on %s",
                                            idev->dev->name);
                        continue;
                }

                score->rule = -1;
                bitmap_zero(score->scorebits, IPV6_SADDR_RULE_MAX);

                for (i = 0; i < IPV6_SADDR_RULE_MAX; i++) {
                        int minihiscore, miniscore;

                        minihiscore = ipv6_get_saddr_eval(net, hiscore, dst, i);
                        miniscore = ipv6_get_saddr_eval(net, score, dst, i);

                        if (minihiscore > miniscore) {
                                if (i == IPV6_SADDR_RULE_SCOPE &&
                                    score->scopedist > 0) {
                                        /*
                                         * special case:
                                         * each remaining entry
                                         * has too small (not enough)
                                         * scope, because ifa entries
                                         * are sorted by their scope
                                         * values.
                                         */
                                        goto out;
                                }
                                break;
                        } else if (minihiscore < miniscore) {
                                swap(hiscore, score);
                                hiscore_idx = 1 - hiscore_idx;

                                /* restore our iterator */
                                score->ifa = hiscore->ifa;

                                break;
                        }
                }
        }
out:
        return hiscore_idx;
}

static int ipv6_get_saddr_master(struct net *net,
                                 const struct net_device *dst_dev,
                                 const struct net_device *master,
                                 struct ipv6_saddr_dst *dst,
                                 struct ipv6_saddr_score *scores,
                                 int hiscore_idx)
{
        struct inet6_dev *idev;

        idev = __in6_dev_get(dst_dev);
        if (idev)
                hiscore_idx = __ipv6_dev_get_saddr(net, dst, idev,
                                                   scores, hiscore_idx);

        idev = __in6_dev_get(master);
        if (idev)
                hiscore_idx = __ipv6_dev_get_saddr(net, dst, idev,
                                                   scores, hiscore_idx);

        return hiscore_idx;
}

int ipv6_dev_get_saddr(struct net *net, const struct net_device *dst_dev,
                       const struct in6_addr *daddr, unsigned int prefs,
                       struct in6_addr *saddr)
{
        struct ipv6_saddr_score scores[2], *hiscore;
        struct ipv6_saddr_dst dst;
        struct inet6_dev *idev;
        struct net_device *dev;
        int dst_type;
        bool use_oif_addr = false;
        int hiscore_idx = 0;
        int ret = 0;

        dst_type = __ipv6_addr_type(daddr);
        dst.addr = daddr;
        dst.ifindex = dst_dev ? dst_dev->ifindex : 0;
        dst.scope = __ipv6_addr_src_scope(dst_type);
        dst.label = ipv6_addr_label(net, daddr, dst_type, dst.ifindex);
        dst.prefs = prefs;

        scores[hiscore_idx].rule = -1;
        scores[hiscore_idx].ifa = NULL;

        rcu_read_lock();

        /* Candidate Source Address (section 4)
         *  - multicast and link-local destination address,
         *    the set of candidate source address MUST only
         *    include addresses assigned to interfaces
         *    belonging to the same link as the outgoing
         *    interface.
         * (- For site-local destination addresses, the
         *    set of candidate source addresses MUST only
         *    include addresses assigned to interfaces
         *    belonging to the same site as the outgoing
         *    interface.)
         *  - "It is RECOMMENDED that the candidate source addresses
         *    be the set of unicast addresses assigned to the
         *    interface that will be used to send to the destination
         *    (the 'outgoing' interface)." (RFC 6724)
         */
        if (dst_dev) {
                idev = __in6_dev_get(dst_dev);
                if ((dst_type & IPV6_ADDR_MULTICAST) ||
                    dst.scope <= IPV6_ADDR_SCOPE_LINKLOCAL ||
                    (idev && idev->cnf.use_oif_addrs_only)) {
                        use_oif_addr = true;
                }
        }

        if (use_oif_addr) {
                if (idev)
                        hiscore_idx = __ipv6_dev_get_saddr(net, &dst, idev, scores, hiscore_idx);
        } else {
                const struct net_device *master;
                int master_idx = 0;

                /* if dst_dev exists and is enslaved to an L3 device, then
                 * prefer addresses from dst_dev and then the master over
                 * any other enslaved devices in the L3 domain.
                 */
                master = l3mdev_master_dev_rcu(dst_dev);
                if (master) {
                        master_idx = master->ifindex;

                        hiscore_idx = ipv6_get_saddr_master(net, dst_dev,
                                                            master, &dst,
                                                            scores, hiscore_idx);

                        if (scores[hiscore_idx].ifa)
                                goto out;
                }

                for_each_netdev_rcu(net, dev) {
                        /* only consider addresses on devices in the
                         * same L3 domain
                         */
                        if (l3mdev_master_ifindex_rcu(dev) != master_idx)
                                continue;
                        idev = __in6_dev_get(dev);
                        if (!idev)
                                continue;
                        hiscore_idx = __ipv6_dev_get_saddr(net, &dst, idev, scores, hiscore_idx);
                }
        }

out:
        hiscore = &scores[hiscore_idx];
        if (!hiscore->ifa)
                ret = -EADDRNOTAVAIL;
        else
                *saddr = hiscore->ifa->addr;

        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL(ipv6_dev_get_saddr);

int __ipv6_get_lladdr(struct inet6_dev *idev, struct in6_addr *addr,
                      u32 banned_flags)
{
        struct inet6_ifaddr *ifp;
        int err = -EADDRNOTAVAIL;

        list_for_each_entry_reverse(ifp, &idev->addr_list, if_list) {
                if (ifp->scope > IFA_LINK)
                        break;
                if (ifp->scope == IFA_LINK &&
                    !(ifp->flags & banned_flags)) {
                        *addr = ifp->addr;
                        err = 0;
                        break;
                }
        }
        return err;
}

int ipv6_get_lladdr(struct net_device *dev, struct in6_addr *addr,
                    u32 banned_flags)
{
        struct inet6_dev *idev;
        int err = -EADDRNOTAVAIL;

        rcu_read_lock();
        idev = __in6_dev_get(dev);
        if (idev) {
                read_lock_bh(&idev->lock);
                err = __ipv6_get_lladdr(idev, addr, banned_flags);
                read_unlock_bh(&idev->lock);
        }
        rcu_read_unlock();
        return err;
}

static int ipv6_count_addresses(const struct inet6_dev *idev)
{
        const struct inet6_ifaddr *ifp;
        int cnt = 0;

        rcu_read_lock();
        list_for_each_entry_rcu(ifp, &idev->addr_list, if_list)
                cnt++;
        rcu_read_unlock();
        return cnt;
}

int ipv6_chk_addr(struct net *net, const struct in6_addr *addr,
                  const struct net_device *dev, int strict)
{
        return ipv6_chk_addr_and_flags(net, addr, dev, !dev,
                                       strict, IFA_F_TENTATIVE);
}
EXPORT_SYMBOL(ipv6_chk_addr);

/* device argument is used to find the L3 domain of interest. If
 * skip_dev_check is set, then the ifp device is not checked against
 * the passed in dev argument. So the 2 cases for addresses checks are:
 *   1. does the address exist in the L3 domain that dev is part of
 *      (skip_dev_check = true), or
 *
 *   2. does the address exist on the specific device
 *      (skip_dev_check = false)
 */
static struct net_device *
__ipv6_chk_addr_and_flags(struct net *net, const struct in6_addr *addr,
                          const struct net_device *dev, bool skip_dev_check,
                          int strict, u32 banned_flags)
{
        unsigned int hash = inet6_addr_hash(net, addr);
        struct net_device *l3mdev, *ndev;
        struct inet6_ifaddr *ifp;
        u32 ifp_flags;

        rcu_read_lock();

        l3mdev = l3mdev_master_dev_rcu(dev);
        if (skip_dev_check)
                dev = NULL;

        hlist_for_each_entry_rcu(ifp, &inet6_addr_lst[hash], addr_lst) {
                ndev = ifp->idev->dev;
                if (!net_eq(dev_net(ndev), net))
                        continue;

                if (l3mdev_master_dev_rcu(ndev) != l3mdev)
                        continue;

                /* Decouple optimistic from tentative for evaluation here.
                 * Ban optimistic addresses explicitly, when required.
                 */
                ifp_flags = (ifp->flags&IFA_F_OPTIMISTIC)
                            ? (ifp->flags&~IFA_F_TENTATIVE)
                            : ifp->flags;
                if (ipv6_addr_equal(&ifp->addr, addr) &&
                    !(ifp_flags&banned_flags) &&
                    (!dev || ndev == dev ||
                     !(ifp->scope&(IFA_LINK|IFA_HOST) || strict))) {
                        rcu_read_unlock();
                        return ndev;
                }
        }

        rcu_read_unlock();
        return NULL;
}

int ipv6_chk_addr_and_flags(struct net *net, const struct in6_addr *addr,
                            const struct net_device *dev, bool skip_dev_check,
                            int strict, u32 banned_flags)
{
        return __ipv6_chk_addr_and_flags(net, addr, dev, skip_dev_check,
                                         strict, banned_flags) ? 1 : 0;
}
EXPORT_SYMBOL(ipv6_chk_addr_and_flags);


/* Compares an address/prefix_len with addresses on device @dev.
 * If one is found it returns true.
 */
bool ipv6_chk_custom_prefix(const struct in6_addr *addr,
        const unsigned int prefix_len, struct net_device *dev)
{
        const struct inet6_ifaddr *ifa;
        const struct inet6_dev *idev;
        bool ret = false;

        rcu_read_lock();
        idev = __in6_dev_get(dev);
        if (idev) {
                list_for_each_entry_rcu(ifa, &idev->addr_list, if_list) {
                        ret = ipv6_prefix_equal(addr, &ifa->addr, prefix_len);
                        if (ret)
                                break;
                }
        }
        rcu_read_unlock();

        return ret;
}
EXPORT_SYMBOL(ipv6_chk_custom_prefix);

int ipv6_chk_prefix(const struct in6_addr *addr, struct net_device *dev)
{
        const struct inet6_ifaddr *ifa;
        const struct inet6_dev *idev;
        int     onlink;

        onlink = 0;
        rcu_read_lock();
        idev = __in6_dev_get(dev);
        if (idev) {
                list_for_each_entry_rcu(ifa, &idev->addr_list, if_list) {
                        onlink = ipv6_prefix_equal(addr, &ifa->addr,
                                                   ifa->prefix_len);
                        if (onlink)
                                break;
                }
        }
        rcu_read_unlock();
        return onlink;
}
EXPORT_SYMBOL(ipv6_chk_prefix);

/**
 * ipv6_dev_find - find the first device with a given source address.
 * @net: the net namespace