/*
 *      Linux INET6 implementation
 *
 *      Authors:
 *      Pedro Roque             <roque@di.fc.ul.pt>
 *
 *      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.
 */

#ifndef _NET_IPV6_H
#define _NET_IPV6_H

#include <linux/ipv6.h>
#include <linux/hardirq.h>
#include <linux/jhash.h>
#include <net/if_inet6.h>
#include <net/ndisc.h>
#include <net/flow.h>
#include <net/flow_dissector.h>
#include <net/snmp.h>

#define SIN6_LEN_RFC2133        24

#define IPV6_MAXPLEN            65535

/*
 *      NextHeader field of IPv6 header
 */

#define NEXTHDR_HOP             0       /* Hop-by-hop option header. */
#define NEXTHDR_TCP             6       /* TCP segment. */
#define NEXTHDR_UDP             17      /* UDP message. */
#define NEXTHDR_IPV6            41      /* IPv6 in IPv6 */
#define NEXTHDR_ROUTING         43      /* Routing header. */
#define NEXTHDR_FRAGMENT        44      /* Fragmentation/reassembly header. */
#define NEXTHDR_GRE             47      /* GRE header. */
#define NEXTHDR_ESP             50      /* Encapsulating security payload. */
#define NEXTHDR_AUTH            51      /* Authentication header. */
#define NEXTHDR_ICMP            58      /* ICMP for IPv6. */
#define NEXTHDR_NONE            59      /* No next header */
#define NEXTHDR_DEST            60      /* Destination options header. */
#define NEXTHDR_SCTP            132     /* SCTP message. */
#define NEXTHDR_MOBILITY        135     /* Mobility header. */

#define NEXTHDR_MAX             255



#define IPV6_DEFAULT_HOPLIMIT   64
#define IPV6_DEFAULT_MCASTHOPS  1

/*
 *      Addr type
 *      
 *      type    -       unicast | multicast
 *      scope   -       local   | site      | global
 *      v4      -       compat
 *      v4mapped
 *      any
 *      loopback
 */

#define IPV6_ADDR_ANY           0x0000U

#define IPV6_ADDR_UNICAST       0x0001U 
#define IPV6_ADDR_MULTICAST     0x0002U 

#define IPV6_ADDR_LOOPBACK      0x0010U
#define IPV6_ADDR_LINKLOCAL     0x0020U
#define IPV6_ADDR_SITELOCAL     0x0040U

#define IPV6_ADDR_COMPATv4      0x0080U

#define IPV6_ADDR_SCOPE_MASK    0x00f0U

#define IPV6_ADDR_MAPPED        0x1000U

/*
 *      Addr scopes
 */
#define IPV6_ADDR_MC_SCOPE(a)   \
        ((a)->s6_addr[1] & 0x0f)        /* nonstandard */
#define __IPV6_ADDR_SCOPE_INVALID       -1
#define IPV6_ADDR_SCOPE_NODELOCAL       0x01
#define IPV6_ADDR_SCOPE_LINKLOCAL       0x02
#define IPV6_ADDR_SCOPE_SITELOCAL       0x05
#define IPV6_ADDR_SCOPE_ORGLOCAL        0x08
#define IPV6_ADDR_SCOPE_GLOBAL          0x0e

/*
 *      Addr flags
 */
#define IPV6_ADDR_MC_FLAG_TRANSIENT(a)  \
        ((a)->s6_addr[1] & 0x10)
#define IPV6_ADDR_MC_FLAG_PREFIX(a)     \
        ((a)->s6_addr[1] & 0x20)
#define IPV6_ADDR_MC_FLAG_RENDEZVOUS(a) \
        ((a)->s6_addr[1] & 0x40)

/*
 *      fragmentation header
 */

struct frag_hdr {
        __u8    nexthdr;
        __u8    reserved;
        __be16  frag_off;
        __be32  identification;
};

#define IP6_MF          0x0001
#define IP6_OFFSET      0xFFF8

#define IP6_REPLY_MARK(net, mark) \
        ((net)->ipv6_sysctl_fwmark_reflect ? (mark) : 0)

#include <net/sock.h>

/* sysctls */
extern int sysctl_mld_max_msf;
extern int sysctl_mld_qrv;

#define _DEVINC(net, statname, modifier, idev, field)                   \
({                                                                      \
        struct inet6_dev *_idev = (idev);                               \
        if (likely(_idev != NULL))                                      \
                SNMP_INC_STATS##modifier((_idev)->stats.statname, (field)); \
        SNMP_INC_STATS##modifier((net)->mib.statname##_statistics, (field));\
})

/* per device counters are atomic_long_t */
#define _DEVINCATOMIC(net, statname, modifier, idev, field)             \
({                                                                      \
        struct inet6_dev *_idev = (idev);                               \
        if (likely(_idev != NULL))                                      \
                SNMP_INC_STATS_ATOMIC_LONG((_idev)->stats.statname##dev, (field)); \
        SNMP_INC_STATS##modifier((net)->mib.statname##_statistics, (field));\
})

/* per device and per net counters are atomic_long_t */
#define _DEVINC_ATOMIC_ATOMIC(net, statname, idev, field)               \
({                                                                      \
        struct inet6_dev *_idev = (idev);                               \
        if (likely(_idev != NULL))                                      \
                SNMP_INC_STATS_ATOMIC_LONG((_idev)->stats.statname##dev, (field)); \
        SNMP_INC_STATS_ATOMIC_LONG((net)->mib.statname##_statistics, (field));\
})

#define _DEVADD(net, statname, modifier, idev, field, val)              \
({                                                                      \
        struct inet6_dev *_idev = (idev);                               \
        if (likely(_idev != NULL))                                      \
                SNMP_ADD_STATS##modifier((_idev)->stats.statname, (field), (val)); \
        SNMP_ADD_STATS##modifier((net)->mib.statname##_statistics, (field), (val));\
})

#define _DEVUPD(net, statname, modifier, idev, field, val)              \
({                                                                      \
        struct inet6_dev *_idev = (idev);                               \
        if (likely(_idev != NULL))                                      \
                SNMP_UPD_PO_STATS##modifier((_idev)->stats.statname, field, (val)); \
        SNMP_UPD_PO_STATS##modifier((net)->mib.statname##_statistics, field, (val));\
})

/* MIBs */

#define IP6_INC_STATS(net, idev,field)          \
                _DEVINC(net, ipv6, 64, idev, field)
#define IP6_INC_STATS_BH(net, idev,field)       \
                _DEVINC(net, ipv6, 64_BH, idev, field)
#define IP6_ADD_STATS(net, idev,field,val)      \
                _DEVADD(net, ipv6, 64, idev, field, val)
#define IP6_ADD_STATS_BH(net, idev,field,val)   \
                _DEVADD(net, ipv6, 64_BH, idev, field, val)
#define IP6_UPD_PO_STATS(net, idev,field,val)   \
                _DEVUPD(net, ipv6, 64, idev, field, val)
#define IP6_UPD_PO_STATS_BH(net, idev,field,val)   \
                _DEVUPD(net, ipv6, 64_BH, idev, field, val)
#define ICMP6_INC_STATS(net, idev, field)       \
                _DEVINCATOMIC(net, icmpv6, , idev, field)
#define ICMP6_INC_STATS_BH(net, idev, field)    \
                _DEVINCATOMIC(net, icmpv6, _BH, idev, field)

#define ICMP6MSGOUT_INC_STATS(net, idev, field)         \
        _DEVINC_ATOMIC_ATOMIC(net, icmpv6msg, idev, field +256)
#define ICMP6MSGOUT_INC_STATS_BH(net, idev, field)      \
        _DEVINC_ATOMIC_ATOMIC(net, icmpv6msg, idev, field +256)
#define ICMP6MSGIN_INC_STATS_BH(net, idev, field)       \
        _DEVINC_ATOMIC_ATOMIC(net, icmpv6msg, idev, field)

struct ip6_ra_chain {
        struct ip6_ra_chain     *next;
        struct sock             *sk;
        int                     sel;
        void                    (*destructor)(struct sock *);
};

extern struct ip6_ra_chain      *ip6_ra_chain;
extern rwlock_t ip6_ra_lock;

/*
   This structure is prepared by protocol, when parsing
   ancillary data and passed to IPv6.
 */

struct ipv6_txoptions {
        atomic_t                refcnt;
        /* Length of this structure */
        int                     tot_len;

        /* length of extension headers   */

        __u16                   opt_flen;       /* after fragment hdr */
        __u16                   opt_nflen;      /* before fragment hdr */

        struct ipv6_opt_hdr     *hopopt;
        struct ipv6_opt_hdr     *dst0opt;
        struct ipv6_rt_hdr      *srcrt; /* Routing Header */
        struct ipv6_opt_hdr     *dst1opt;
        struct rcu_head         rcu;
        /* Option buffer, as read by IPV6_PKTOPTIONS, starts here. */
};

struct ip6_flowlabel {
        struct ip6_flowlabel __rcu *next;
        __be32                  label;
        atomic_t                users;
        struct in6_addr         dst;
        struct ipv6_txoptions   *opt;
        unsigned long           linger;
        struct rcu_head         rcu;
        u8                      share;
        union {
                struct pid *pid;
                kuid_t uid;
        } owner;
        unsigned long           lastuse;
        unsigned long           expires;
        struct net              *fl_net;
};

#define IPV6_FLOWINFO_MASK      cpu_to_be32(0x0FFFFFFF)
#define IPV6_FLOWLABEL_MASK     cpu_to_be32(0x000FFFFF)
#define IPV6_TCLASS_MASK (IPV6_FLOWINFO_MASK & ~IPV6_FLOWLABEL_MASK)
#define IPV6_TCLASS_SHIFT       20

struct ipv6_fl_socklist {
        struct ipv6_fl_socklist __rcu   *next;
        struct ip6_flowlabel            *fl;
        struct rcu_head                 rcu;
};

static inline struct ipv6_txoptions *txopt_get(const struct ipv6_pinfo *np)
{
        struct ipv6_txoptions *opt;

        rcu_read_lock();
        opt = rcu_dereference(np->opt);
        if (opt && !atomic_inc_not_zero(&opt->refcnt))
                opt = NULL;
        rcu_read_unlock();
        return opt;
}

static inline void txopt_put(struct ipv6_txoptions *opt)
{
        if (opt && atomic_dec_and_test(&opt->refcnt))
                kfree_rcu(opt, rcu);
}

struct ip6_flowlabel *fl6_sock_lookup(struct sock *sk, __be32 label);
struct ipv6_txoptions *fl6_merge_options(struct ipv6_txoptions *opt_space,
                                         struct ip6_flowlabel *fl,
                                         struct ipv6_txoptions *fopt);
void fl6_free_socklist(struct sock *sk);
int ipv6_flowlabel_opt(struct sock *sk, char __user *optval, int optlen);
int ip6_flowlabel_init(void);
void ip6_flowlabel_cleanup(void);

static inline void fl6_sock_release(struct ip6_flowlabel *fl)
{
        if (fl)
                atomic_dec(&fl->users);
}

void icmpv6_notify(struct sk_buff *skb, u8 type, u8 code, __be32 info);

int ip6_ra_control(struct sock *sk, int sel);

int ipv6_parse_hopopts(struct sk_buff *skb);

struct ipv6_txoptions *ipv6_dup_options(struct sock *sk,
                                        struct ipv6_txoptions *opt);
struct ipv6_txoptions *ipv6_renew_options(struct sock *sk,
                                          struct ipv6_txoptions *opt,
                                          int newtype,
                                          struct ipv6_opt_hdr __user *newopt,
                                          int newoptlen);
struct ipv6_txoptions *ipv6_fixup_options(struct ipv6_txoptions *opt_space,
                                          struct ipv6_txoptions *opt);

bool ipv6_opt_accepted(const struct sock *sk, const struct sk_buff *skb);

static inline bool ipv6_accept_ra(struct inet6_dev *idev)
{
        /* If forwarding is enabled, RA are not accepted unless the special
         * hybrid mode (accept_ra=2) is enabled.
         */
        return idev->cnf.forwarding ? idev->cnf.accept_ra == 2 :
            idev->cnf.accept_ra;
}

#if IS_ENABLED(CONFIG_IPV6)
static inline int ip6_frag_nqueues(struct net *net)
{
        return net->ipv6.frags.nqueues;
}

static inline int ip6_frag_mem(struct net *net)
{
        return sum_frag_mem_limit(&net->ipv6.frags);
}
#endif

#define IPV6_FRAG_HIGH_THRESH   (4 * 1024*1024) /* 4194304 */
#define IPV6_FRAG_LOW_THRESH    (3 * 1024*1024) /* 3145728 */
#define IPV6_FRAG_TIMEOUT       (60 * HZ)       /* 60 seconds */

int __ipv6_addr_type(const struct in6_addr *addr);
static inline int ipv6_addr_type(const struct in6_addr *addr)
{
        return __ipv6_addr_type(addr) & 0xffff;
}

static inline int ipv6_addr_scope(const struct in6_addr *addr)
{
        return __ipv6_addr_type(addr) & IPV6_ADDR_SCOPE_MASK;
}

static inline int __ipv6_addr_src_scope(int type)
{
        return (type == IPV6_ADDR_ANY) ? __IPV6_ADDR_SCOPE_INVALID : (type >> 16);
}

static inline int ipv6_addr_src_scope(const struct in6_addr *addr)
{
        return __ipv6_addr_src_scope(__ipv6_addr_type(addr));
}

static inline bool __ipv6_addr_needs_scope_id(int type)
{
        return type & IPV6_ADDR_LINKLOCAL ||
               (type & IPV6_ADDR_MULTICAST &&
                (type & (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)));
}

static inline __u32 ipv6_iface_scope_id(const struct in6_addr *addr, int iface)
{
        return __ipv6_addr_needs_scope_id(__ipv6_addr_type(addr)) ? iface : 0;
}

static inline int ipv6_addr_cmp(const struct in6_addr *a1, const struct in6_addr *a2)
{
        return memcmp(a1, a2, sizeof(struct in6_addr));
}

static inline bool
ipv6_masked_addr_cmp(const struct in6_addr *a1, const struct in6_addr *m,
                     const struct in6_addr *a2)
{
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
        const unsigned long *ul1 = (const unsigned long *)a1;
        const unsigned long *ulm = (const unsigned long *)m;
        const unsigned long *ul2 = (const unsigned long *)a2;

        return !!(((ul1[0] ^ ul2[0]) & ulm[0]) |
                  ((ul1[1] ^ ul2[1]) & ulm[1]));
#else
        return !!(((a1->s6_addr32[0] ^ a2->s6_addr32[0]) & m->s6_addr32[0]) |
                  ((a1->s6_addr32[1] ^ a2->s6_addr32[1]) & m->s6_addr32[1]) |
                  ((a1->s6_addr32[2] ^ a2->s6_addr32[2]) & m->s6_addr32[2]) |
                  ((a1->s6_addr32[3] ^ a2->s6_addr32[3]) & m->s6_addr32[3]));
#endif
}

static inline void ipv6_addr_prefix(struct in6_addr *pfx, 
                                    const struct in6_addr *addr,
                                    int plen)
{
        /* caller must guarantee 0 <= plen <= 128 */
        int o = plen >> 3,
            b = plen & 0x7;

        memset(pfx->s6_addr, 0, sizeof(pfx->s6_addr));
        memcpy(pfx->s6_addr, addr, o);
        if (b != 0)
                pfx->s6_addr[o] = addr->s6_addr[o] & (0xff00 >> b);
}

static inline void ipv6_addr_prefix_copy(struct in6_addr *addr,
                                         const struct in6_addr *pfx,
                                         int plen)
{
        /* caller must guarantee 0 <= plen <= 128 */
        int o = plen >> 3,
            b = plen & 0x7;

        memcpy(addr->s6_addr, pfx, o);
        if (b != 0) {
                addr->s6_addr[o] &= ~(0xff00 >> b);
                addr->s6_addr[o] |= (pfx->s6_addr[o] & (0xff00 >> b));
        }
}

static inline void __ipv6_addr_set_half(__be32 *addr,
                                        __be32 wh, __be32 wl)
{
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
#if defined(__BIG_ENDIAN)
        if (__builtin_constant_p(wh) && __builtin_constant_p(wl)) {
                *(__force u64 *)addr = ((__force u64)(wh) << 32 | (__force u64)(wl));
                return;
        }
#elif defined(__LITTLE_ENDIAN)
        if (__builtin_constant_p(wl) && __builtin_constant_p(wh)) {
                *(__force u64 *)addr = ((__force u64)(wl) << 32 | (__force u64)(wh));
                return;
        }
#endif
#endif
        addr[0] = wh;
        addr[1] = wl;
}

static inline void ipv6_addr_set(struct in6_addr *addr, 
                                     __be32 w1, __be32 w2,
                                     __be32 w3, __be32 w4)
{
        __ipv6_addr_set_half(&addr->s6_addr32[0], w1, w2);
        __ipv6_addr_set_half(&addr->s6_addr32[2], w3, w4);
}

static inline bool ipv6_addr_equal(const struct in6_addr *a1,
                                   const struct in6_addr *a2)
{
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
        const unsigned long *ul1 = (const unsigned long *)a1;
        const unsigned long *ul2 = (const unsigned long *)a2;

        return ((ul1[0] ^ ul2[0]) | (ul1[1] ^ ul2[1])) == 0UL;
#else
        return ((a1->s6_addr32[0] ^ a2->s6_addr32[0]) |
                (a1->s6_addr32[1] ^ a2->s6_addr32[1]) |
                (a1->s6_addr32[2] ^ a2->s6_addr32[2]) |
                (a1->s6_addr32[3] ^ a2->s6_addr32[3])) == 0;
#endif
}

#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
static inline bool __ipv6_prefix_equal64_half(const __be64 *a1,
                                              const __be64 *a2,
                                              unsigned int len)
{
        if (len && ((*a1 ^ *a2) & cpu_to_be64((~0UL) << (64 - len))))
                return false;
        return true;
}

static inline bool ipv6_prefix_equal(const struct in6_addr *addr1,
                                     const struct in6_addr *addr2,
                                     unsigned int prefixlen)
{
        const __be64 *a1 = (const __be64 *)addr1;
        const __be64 *a2 = (const __be64 *)addr2;

        if (prefixlen >= 64) {
                if (a1[0] ^ a2[0])
                        return false;
                return __ipv6_prefix_equal64_half(a1 + 1, a2 + 1, prefixlen - 64);
        }
        return __ipv6_prefix_equal64_half(a1, a2, prefixlen);
}
#else
static inline bool ipv6_prefix_equal(const struct in6_addr *addr1,
                                     const struct in6_addr *addr2,
                                     unsigned int prefixlen)
{
        const __be32 *a1 = addr1->s6_addr32;
        const __be32 *a2 = addr2->s6_addr32;
        unsigned int pdw, pbi;

        /* check complete u32 in prefix */
        pdw = prefixlen >> 5;
        if (pdw && memcmp(a1, a2, pdw << 2))
                return false;

        /* check incomplete u32 in prefix */
        pbi = prefixlen & 0x1f;
        if (pbi && ((a1[pdw] ^ a2[pdw]) & htonl((0xffffffff) << (32 - pbi))))
                return false;

        return true;
}
#endif

struct inet_frag_queue;

enum ip6_defrag_users {
        IP6_DEFRAG_LOCAL_DELIVER,
        IP6_DEFRAG_CONNTRACK_IN,
        __IP6_DEFRAG_CONNTRACK_IN       = IP6_DEFRAG_CONNTRACK_IN + USHRT_MAX,
        IP6_DEFRAG_CONNTRACK_OUT,
        __IP6_DEFRAG_CONNTRACK_OUT      = IP6_DEFRAG_CONNTRACK_OUT + USHRT_MAX,
        IP6_DEFRAG_CONNTRACK_BRIDGE_IN,
        __IP6_DEFRAG_CONNTRACK_BRIDGE_IN = IP6_DEFRAG_CONNTRACK_BRIDGE_IN + USHRT_MAX,
};

struct ip6_create_arg {
        __be32 id;
        u32 user;
        const struct in6_addr *src;
        const struct in6_addr *dst;
        int iif;
        u8 ecn;
};

void ip6_frag_init(struct inet_frag_queue *q, void *a);
bool ip6_frag_match(struct inet_frag_queue *q, void *a);

/*
 *      Equivalent of ipv4 struct ip
 */
struct frag_queue {
        struct inet_frag_queue  q;

        __be32                  id;             /* fragment id          */
        u32                     user;
        struct in6_addr         saddr;
        struct in6_addr         daddr;

        int                     iif;
        unsigned int            csum;
        __u16                   nhoffset;
        u8                      ecn;
};

void ip6_expire_frag_queue(struct net *net, struct frag_queue *fq,
                           struct inet_frags *frags);

static inline bool ipv6_addr_any(const struct in6_addr *a)
{
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
        const unsigned long *ul = (const unsigned long *)a;

        return (ul[0] | ul[1]) == 0UL;
#else
        return (a->s6_addr32[0] | a->s6_addr32[1] |
                a->s6_addr32[2] | a->s6_addr32[3]) == 0;
#endif
}

static inline u32 ipv6_addr_hash(const struct in6_addr *a)
{
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
        const unsigned long *ul = (const unsigned long *)a;
        unsigned long x = ul[0] ^ ul[1];

        return (u32)(x ^ (x >> 32));
#else
        return (__force u32)(a->s6_addr32[0] ^ a->s6_addr32[1] ^
                             a->s6_addr32[2] ^ a->s6_addr32[3]);
#endif
}

/* more secured version of ipv6_addr_hash() */
static inline u32 __ipv6_addr_jhash(const struct in6_addr *a, const u32 initval)
{
        u32 v = (__force u32)a->s6_addr32[0] ^ (__force u32)a->s6_addr32[1];

        return jhash_3words(v,
                            (__force u32)a->s6_addr32[2],
                            (__force u32)a->s6_addr32[3],
                            initval);
}

static inline bool ipv6_addr_loopback(const struct in6_addr *a)
{
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
        const unsigned long *ul = (const unsigned long *)a;

        return (ul[0] | (ul[1] ^ cpu_to_be64(1))) == 0UL;
#else
        return (a->s6_addr32[0] | a->s6_addr32[1] |
                a->s6_addr32[2] | (a->s6_addr32[3] ^ htonl(1))) == 0;
#endif
}

static inline bool ipv6_addr_v4mapped(const struct in6_addr *a)
{
        return (
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
                *(__be64 *)a |
#else
                (a->s6_addr32[0] | a->s6_addr32[1]) |
#endif
                (a->s6_addr32[2] ^ htonl(0x0000ffff))) == 0UL;
}

/*
 * Check for a RFC 4843 ORCHID address
 * (Overlay Routable Cryptographic Hash Identifiers)
 */
static inline bool ipv6_addr_orchid(const struct in6_addr *a)
{
        return (a->s6_addr32[0] & htonl(0xfffffff0)) == htonl(0x20010010);
}

static inline void ipv6_addr_set_v4mapped(const __be32 addr,
                                          struct in6_addr *v4mapped)
{
        ipv6_addr_set(v4mapped,
                        0, 0,
                        htonl(0x0000FFFF),
                        addr);
}

/*
 * find the first different bit between two addresses
 * length of address must be a multiple of 32bits
 */
static inline int __ipv6_addr_diff32(const void *token1, const void *token2, int addrlen)
{
        const __be32 *a1 = token1, *a2 = token2;
        int i;

        addrlen >>= 2;

        for (i = 0; i < addrlen; i++) {
                __be32 xb = a1[i] ^ a2[i];
                if (xb)
                        return i * 32 + 31 - __fls(ntohl(xb));
        }

        /*
         *      we should *never* get to this point since that 
         *      would mean the addrs are equal
         *
         *      However, we do get to it 8) And exacly, when
         *      addresses are equal 8)
         *
         *      ip route add 1111::/128 via ...
         *      ip route add 1111::/64 via ...
         *      and we are here.
         *
         *      Ideally, this function should stop comparison
         *      at prefix length. It does not, but it is still OK,
         *      if returned value is greater than prefix length.
         *                                      --ANK (980803)
         */
        return addrlen << 5;
}

#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
static inline int __ipv6_addr_diff64(const void *token1, const void *token2, int addrlen)
{
        const __be64 *a1 = token1, *a2 = token2;
        int i;

        addrlen >>= 3;

        for (i = 0; i < addrlen; i++) {
                __be64 xb = a1[i] ^ a2[i];
                if (xb)
                        return i * 64 + 63 - __fls(be64_to_cpu(xb));
        }

        return addrlen << 6;
}
#endif

static inline int __ipv6_addr_diff(const void *token1, const void *token2, int addrlen)
{
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
        if (__builtin_constant_p(addrlen) && !(addrlen & 7))
                return __ipv6_addr_diff64(token1, token2, addrlen);
#endif
        return __ipv6_addr_diff32(token1, token2, addrlen);
}

static inline int ipv6_addr_diff(const struct in6_addr *a1, const struct in6_addr *a2)
{
        return __ipv6_addr_diff(a1, a2, sizeof(struct in6_addr));
}

__be32 ipv6_select_ident(struct net *net,
                         const struct in6_addr *daddr,
                         const struct in6_addr *saddr);
void ipv6_proxy_select_ident(struct net *net, struct sk_buff *skb);

int ip6_dst_hoplimit(struct dst_entry *dst);

/* copy IPv6 saddr & daddr to flow_keys, possibly using 64bit load/store
 * Equivalent to :      flow->v6addrs.src = iph->saddr;
 *                      flow->v6addrs.dst = iph->daddr;
 */
static inline void iph_to_flow_copy_v6addrs(struct flow_keys *flow,
                                            const struct ipv6hdr *iph)
{
        BUILD_BUG_ON(offsetof(typeof(flow->addrs), v6addrs.dst) !=
                     offsetof(typeof(flow->addrs), v6addrs.src) +
                     sizeof(flow->addrs.v6addrs.src));
        memcpy(&flow->addrs.v6addrs, &iph->saddr, sizeof(flow->addrs.v6addrs));
        flow->control.addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
}

#if IS_ENABLED(CONFIG_IPV6)
#else
static inline void ip6_set_txhash(struct sock *sk) { }
#endif

/*
 *      Header manipulation
 */
static inline void ip6_flow_hdr(struct ipv6hdr *hdr, unsigned int tclass,
                                __be32 flowlabel)
{
        *(__be32 *)hdr = htonl(0x60000000 | (tclass << 20)) | flowlabel;
}

static inline __be32 ip6_flowinfo(const struct ipv6hdr *hdr)
{
        return *(__be32 *)hdr & IPV6_FLOWINFO_MASK;
}

static inline __be32 ip6_flowlabel(const struct ipv6hdr *hdr)
{
        return *(__be32 *)hdr & IPV6_FLOWLABEL_MASK;
}

static inline u8 ip6_tclass(__be32 flowinfo)
{
        return ntohl(flowinfo & IPV6_TCLASS_MASK) >> IPV6_TCLASS_SHIFT;
}

static inline __be32 ip6_make_flowinfo(unsigned int tclass, __be32 flowlabel)
{
        return htonl(tclass << IPV6_TCLASS_SHIFT) | flowlabel;
}

/*
 *      Prototypes exported by ipv6
 */

/*
 *      rcv function (called from netdevice level)
 */

int ipv6_rcv(struct sk_buff *skb, struct net_device *dev,
             struct packet_type *pt, struct net_device *orig_dev);

int ip6_rcv_finish(struct sock *sk, struct sk_buff *skb);

/*
 *      upper-layer output functions
 */
int ip6_xmit(struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
             __u32 mark, struct ipv6_txoptions *opt, int tclass);

int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr);

int ip6_append_data(struct sock *sk,
                    int getfrag(void *from, char *to, int offset, int len,
                                int odd, struct sk_buff *skb),
                    void *from, int length, int transhdrlen, int hlimit,
                    int tclass, struct ipv6_txoptions *opt, struct flowi6 *fl6,
                    struct rt6_info *rt, unsigned int flags, int dontfrag);

int ip6_push_pending_frames(struct sock *sk);

void ip6_flush_pending_frames(struct sock *sk);

int ip6_send_skb(struct sk_buff *skb);

struct sk_buff *__ip6_make_skb(struct sock *sk, struct sk_buff_head *queue,
                               struct inet_cork_full *cork,
                               struct inet6_cork *v6_cork);

struct sk_buff *ip6_make_skb(struct sock *sk,
                             int getfrag(void *from, char *to, int offset,
                                         int len, int odd, struct sk_buff *skb),
                             void *from, int length, int transhdrlen,
                             int hlimit, int tclass, struct ipv6_txoptions *opt,
                             struct flowi6 *fl6, struct rt6_info *rt,
                             unsigned int flags, int dontfrag);

static inline struct sk_buff *ip6_finish_skb(struct sock *sk)
{
        return __ip6_make_skb(sk, &sk->sk_write_queue, &inet_sk(sk)->cork,
                              &inet6_sk(sk)->cork);
}

int ip6_dst_lookup(struct net *net, struct sock *sk, struct dst_entry **dst,
                   struct flowi6 *fl6);
struct dst_entry *ip6_dst_lookup_flow(struct net *net, const struct sock *sk, struct flowi6 *fl6,
                                      const struct in6_addr *final_dst);
struct dst_entry *ip6_sk_dst_lookup_flow(struct sock *sk, struct flowi6 *fl6,
                                         const struct in6_addr *final_dst);
struct dst_entry *ip6_blackhole_route(struct net *net,
                                      struct dst_entry *orig_dst);

/*
 *      skb processing functions
 */

int ip6_output(struct sock *sk, struct sk_buff *skb);
int ip6_forward(struct sk_buff *skb);
int ip6_input(struct sk_buff *skb);
int ip6_mc_input(struct sk_buff *skb);

int __ip6_local_out(struct sk_buff *skb);
int ip6_local_out_sk(struct sock *sk, struct sk_buff *skb);
int ip6_local_out(struct sk_buff *skb);

/*
 *      Extension header (options) processing
 */

void ipv6_push_nfrag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt,
                          u8 *proto, struct in6_addr **daddr_p);
void ipv6_push_frag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt,
                         u8 *proto);

int ipv6_skip_exthdr(const struct sk_buff *, int start, u8 *nexthdrp,
                     __be16 *frag_offp);

bool ipv6_ext_hdr(u8 nexthdr);

enum {
        IP6_FH_F_FRAG           = (1 << 0),
        IP6_FH_F_AUTH           = (1 << 1),
        IP6_FH_F_SKIP_RH        = (1 << 2),
};

/* find specified header and get offset to it */
int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset, int target,
                  unsigned short *fragoff, int *fragflg);

int ipv6_find_tlv(struct sk_buff *skb, int offset, int type);

struct in6_addr *fl6_update_dst(struct flowi6 *fl6,
                                const struct ipv6_txoptions *opt,
                                struct in6_addr *orig);

/*
 *      socket options (ipv6_sockglue.c)
 */

int ipv6_setsockopt(struct sock *sk, int level, int optname,
                    char __user *optval, unsigned int optlen);
int ipv6_getsockopt(struct sock *sk, int level, int optname,
                    char __user *optval, int __user *optlen);
int compat_ipv6_setsockopt(struct sock *sk, int level, int optname,
                           char __user *optval, unsigned int optlen);
int compat_ipv6_getsockopt(struct sock *sk, int level, int optname,
                           char __user *optval, int __user *optlen);

int ip6_datagram_connect(struct sock *sk, struct sockaddr *addr, int addr_len);
int ip6_datagram_dst_update(struct sock *sk, bool fix_sk_saddr);
void ip6_datagram_release_cb(struct sock *sk);

int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len,
                   int *addr_len);
int ipv6_recv_rxpmtu(struct sock *sk, struct msghdr *msg, int len,
                    int *addr_len);
void ipv6_icmp_error(struct sock *sk, struct sk_buff *skb, int err, __be16 port,
                     u32 info, u8 *payload);
void ipv6_local_error(struct sock *sk, int err, struct flowi6 *fl6, u32 info);
void ipv6_local_rxpmtu(struct sock *sk, struct flowi6 *fl6, u32 mtu);

int inet6_release(struct socket *sock);
int inet6_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len);
int inet6_getname(struct socket *sock, struct sockaddr *uaddr, int *uaddr_len,
                  int peer);
int inet6_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg);

int inet6_hash_connect(struct inet_timewait_death_row *death_row,
                              struct sock *sk);

/*
 * reassembly.c
 */
extern const struct proto_ops inet6_stream_ops;
extern const struct proto_ops inet6_dgram_ops;

struct group_source_req;
struct group_filter;

int ip6_mc_source(int add, int omode, struct sock *sk,
                  struct group_source_req *pgsr);
int ip6_mc_msfilter(struct sock *sk, struct group_filter *gsf);
int ip6_mc_msfget(struct sock *sk, struct group_filter *gsf,
                  struct group_filter __user *optval, int __user *optlen);

#ifdef CONFIG_PROC_FS
int ac6_proc_init(struct net *net);
void ac6_proc_exit(struct net *net);
int raw6_proc_init(void);
void raw6_proc_exit(void);
int tcp6_proc_init(struct net *net);
void tcp6_proc_exit(struct net *net);
int udp6_proc_init(struct net *net);
void udp6_proc_exit(struct net *net);
int udplite6_proc_init(void);
void udplite6_proc_exit(void);
int ipv6_misc_proc_init(void);
void ipv6_misc_proc_exit(void);
int snmp6_register_dev(struct inet6_dev *idev);
int snmp6_unregister_dev(struct inet6_dev *idev);

#else
static inline int ac6_proc_init(struct net *net) { return 0; }
static inline void ac6_proc_exit(struct net *net) { }
static inline int snmp6_register_dev(struct inet6_dev *idev) { return 0; }
static inline int snmp6_unregister_dev(struct inet6_dev *idev) { return 0; }
#endif

#ifdef CONFIG_SYSCTL
extern ctl_table ipv6_route_table_template[];

struct ctl_table *ipv6_icmp_sysctl_init(struct net *net);
struct ctl_table *ipv6_route_sysctl_init(struct net *net);
int ipv6_sysctl_register(void);
void ipv6_sysctl_unregister(void);
#endif

int ipv6_sock_mc_join(struct sock *sk, int ifindex,
                      const struct in6_addr *addr);
int ipv6_sock_mc_join_ssm(struct sock *sk, int ifindex,
                          const struct in6_addr *addr, unsigned int mode);
int ipv6_sock_mc_drop(struct sock *sk, int ifindex,
                      const struct in6_addr *addr);
#endif /* _NET_IPV6_H */