// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      Internet Control Message Protocol (ICMPv6)
 *      Linux INET6 implementation
 *
 *      Authors:
 *      Pedro Roque             <roque@di.fc.ul.pt>
 *
 *      Based on net/ipv4/icmp.c
 *
 *      RFC 1885
 */

/*
 *      Changes:
 *
 *      Andi Kleen              :       exception handling
 *      Andi Kleen                      add rate limits. never reply to a icmp.
 *                                      add more length checks and other fixes.
 *      yoshfuji                :       ensure to sent parameter problem for
 *                                      fragments.
 *      YOSHIFUJI Hideaki @USAGI:       added sysctl for icmp rate limit.
 *      Randy Dunlap and
 *      YOSHIFUJI Hideaki @USAGI:       Per-interface statistics support
 *      Kazunori MIYAZAWA @USAGI:       change output process to use ip6_append_data
 */

#define pr_fmt(fmt) "IPv6: " fmt

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/init.h>
#include <linux/netfilter.h>
#include <linux/slab.h>

#ifdef CONFIG_SYSCTL
#include <linux/sysctl.h>
#endif

#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/icmpv6.h>

#include <net/ip.h>
#include <net/sock.h>

#include <net/ipv6.h>
#include <net/ip6_checksum.h>
#include <net/ping.h>
#include <net/protocol.h>
#include <net/raw.h>
#include <net/rawv6.h>
#include <net/transp_v6.h>
#include <net/ip6_route.h>
#include <net/addrconf.h>
#include <net/icmp.h>
#include <net/xfrm.h>
#include <net/inet_common.h>
#include <net/dsfield.h>
#include <net/l3mdev.h>

#include <linux/uaccess.h>

/*
 *      The ICMP socket(s). This is the most convenient way to flow control
 *      our ICMP output as well as maintain a clean interface throughout
 *      all layers. All Socketless IP sends will soon be gone.
 *
 *      On SMP we have one ICMP socket per-cpu.
 */
static struct sock *icmpv6_sk(struct net *net)
{
        return this_cpu_read(*net->ipv6.icmp_sk);
}

static int icmpv6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
                       u8 type, u8 code, int offset, __be32 info)
{
        /* icmpv6_notify checks 8 bytes can be pulled, icmp6hdr is 8 bytes */
        struct icmp6hdr *icmp6 = (struct icmp6hdr *) (skb->data + offset);
        struct net *net = dev_net(skb->dev);

        if (type == ICMPV6_PKT_TOOBIG)
                ip6_update_pmtu(skb, net, info, skb->dev->ifindex, 0, sock_net_uid(net, NULL));
        else if (type == NDISC_REDIRECT)
                ip6_redirect(skb, net, skb->dev->ifindex, 0,
                             sock_net_uid(net, NULL));

        if (!(type & ICMPV6_INFOMSG_MASK))
                if (icmp6->icmp6_type == ICMPV6_ECHO_REQUEST)
                        ping_err(skb, offset, ntohl(info));

        return 0;
}

static int icmpv6_rcv(struct sk_buff *skb);

static const struct inet6_protocol icmpv6_protocol = {
        .handler        =       icmpv6_rcv,
        .err_handler    =       icmpv6_err,
        .flags          =       INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
};

/* Called with BH disabled */
static __inline__ struct sock *icmpv6_xmit_lock(struct net *net)
{
        struct sock *sk;

        sk = icmpv6_sk(net);
        if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
                /* This can happen if the output path (f.e. SIT or
                 * ip6ip6 tunnel) signals dst_link_failure() for an
                 * outgoing ICMP6 packet.
                 */
                return NULL;
        }
        return sk;
}

static __inline__ void icmpv6_xmit_unlock(struct sock *sk)
{
        spin_unlock(&sk->sk_lock.slock);
}

/*
 * Figure out, may we reply to this packet with icmp error.
 *
 * We do not reply, if:
 *      - it was icmp error message.
 *      - it is truncated, so that it is known, that protocol is ICMPV6
 *        (i.e. in the middle of some exthdr)
 *
 *      --ANK (980726)
 */

static bool is_ineligible(const struct sk_buff *skb)
{
        int ptr = (u8 *)(ipv6_hdr(skb) + 1) - skb->data;
        int len = skb->len - ptr;
        __u8 nexthdr = ipv6_hdr(skb)->nexthdr;
        __be16 frag_off;

        if (len < 0)
                return true;

        ptr = ipv6_skip_exthdr(skb, ptr, &nexthdr, &frag_off);
        if (ptr < 0)
                return false;
        if (nexthdr == IPPROTO_ICMPV6) {
                u8 _type, *tp;
                tp = skb_header_pointer(skb,
                        ptr+offsetof(struct icmp6hdr, icmp6_type),
                        sizeof(_type), &_type);

                /* Based on RFC 8200, Section 4.5 Fragment Header, return
                 * false if this is a fragment packet with no icmp header info.
                 */
                if (!tp && frag_off != 0)
                        return false;
                else if (!tp || !(*tp & ICMPV6_INFOMSG_MASK))
                        return true;
        }
        return false;
}

static bool icmpv6_mask_allow(struct net *net, int type)
{
        if (type > ICMPV6_MSG_MAX)
                return true;

        /* Limit if icmp type is set in ratemask. */
        if (!test_bit(type, net->ipv6.sysctl.icmpv6_ratemask))
                return true;

        return false;
}

static bool icmpv6_global_allow(struct net *net, int type)
{
        if (icmpv6_mask_allow(net, type))
                return true;

        if (icmp_global_allow())
                return true;

        return false;
}

/*
 * Check the ICMP output rate limit
 */
static bool icmpv6_xrlim_allow(struct sock *sk, u8 type,
                               struct flowi6 *fl6)
{
        struct net *net = sock_net(sk);
        struct dst_entry *dst;
        bool res = false;

        if (icmpv6_mask_allow(net, type))
                return true;

        /*
         * Look up the output route.
         * XXX: perhaps the expire for routing entries cloned by
         * this lookup should be more aggressive (not longer than timeout).
         */
        dst = ip6_route_output(net, sk, fl6);
        if (dst->error) {
                IP6_INC_STATS(net, ip6_dst_idev(dst),
                              IPSTATS_MIB_OUTNOROUTES);
        } else if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) {
                res = true;
        } else {
                struct rt6_info *rt = (struct rt6_info *)dst;
                int tmo = net->ipv6.sysctl.icmpv6_time;
                struct inet_peer *peer;

                /* Give more bandwidth to wider prefixes. */
                if (rt->rt6i_dst.plen < 128)
                        tmo >>= ((128 - rt->rt6i_dst.plen)>>5);

                peer = inet_getpeer_v6(net->ipv6.peers, &fl6->daddr, 1);
                res = inet_peer_xrlim_allow(peer, tmo);
                if (peer)
                        inet_putpeer(peer);
        }
        dst_release(dst);
        return res;
}

static bool icmpv6_rt_has_prefsrc(struct sock *sk, u8 type,
                                  struct flowi6 *fl6)
{
        struct net *net = sock_net(sk);
        struct dst_entry *dst;
        bool res = false;

        dst = ip6_route_output(net, sk, fl6);
        if (!dst->error) {
                struct rt6_info *rt = (struct rt6_info *)dst;
                struct in6_addr prefsrc;

                rt6_get_prefsrc(rt, &prefsrc);
                res = !ipv6_addr_any(&prefsrc);
        }
        dst_release(dst);
        return res;
}

/*
 *      an inline helper for the "simple" if statement below
 *      checks if parameter problem report is caused by an
 *      unrecognized IPv6 option that has the Option Type
 *      highest-order two bits set to 10
 */

static bool opt_unrec(struct sk_buff *skb, __u32 offset)
{
        u8 _optval, *op;

        offset += skb_network_offset(skb);
        op = skb_header_pointer(skb, offset, sizeof(_optval), &_optval);
        if (!op)
                return true;
        return (*op & 0xC0) == 0x80;
}

void icmpv6_push_pending_frames(struct sock *sk, struct flowi6 *fl6,
                                struct icmp6hdr *thdr, int len)
{
        struct sk_buff *skb;
        struct icmp6hdr *icmp6h;

        skb = skb_peek(&sk->sk_write_queue);
        if (!skb)
                return;

        icmp6h = icmp6_hdr(skb);
        memcpy(icmp6h, thdr, sizeof(struct icmp6hdr));
        icmp6h->icmp6_cksum = 0;

        if (skb_queue_len(&sk->sk_write_queue) == 1) {
                skb->csum = csum_partial(icmp6h,
                                        sizeof(struct icmp6hdr), skb->csum);
                icmp6h->icmp6_cksum = csum_ipv6_magic(&fl6->saddr,
                                                      &fl6->daddr,
                                                      len, fl6->flowi6_proto,
                                                      skb->csum);
        } else {
                __wsum tmp_csum = 0;

                skb_queue_walk(&sk->sk_write_queue, skb) {
                        tmp_csum = csum_add(tmp_csum, skb->csum);
                }

                tmp_csum = csum_partial(icmp6h,
                                        sizeof(struct icmp6hdr), tmp_csum);
                icmp6h->icmp6_cksum = csum_ipv6_magic(&fl6->saddr,
                                                      &fl6->daddr,
                                                      len, fl6->flowi6_proto,
                                                      tmp_csum);
        }
        ip6_push_pending_frames(sk);
}

struct icmpv6_msg {
        struct sk_buff  *skb;
        int             offset;
        uint8_t         type;
};

static int icmpv6_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
{
        struct icmpv6_msg *msg = (struct icmpv6_msg *) from;
        struct sk_buff *org_skb = msg->skb;
        __wsum csum;

        csum = skb_copy_and_csum_bits(org_skb, msg->offset + offset,
                                      to, len);
        skb->csum = csum_block_add(skb->csum, csum, odd);
        if (!(msg->type & ICMPV6_INFOMSG_MASK))
                nf_ct_attach(skb, org_skb);
        return 0;
}

#if IS_ENABLED(CONFIG_IPV6_MIP6)
static void mip6_addr_swap(struct sk_buff *skb)
{
        struct ipv6hdr *iph = ipv6_hdr(skb);
        struct inet6_skb_parm *opt = IP6CB(skb);
        struct ipv6_destopt_hao *hao;
        struct in6_addr tmp;
        int off;

        if (opt->dsthao) {
                off = ipv6_find_tlv(skb, opt->dsthao, IPV6_TLV_HAO);
                if (likely(off >= 0)) {
                        hao = (struct ipv6_destopt_hao *)
                                        (skb_network_header(skb) + off);
                        tmp = iph->saddr;
                        iph->saddr = hao->addr;
                        hao->addr = tmp;
                }
        }
}
#else
static inline void mip6_addr_swap(struct sk_buff *skb) {}
#endif

static struct dst_entry *icmpv6_route_lookup(struct net *net,
                                             struct sk_buff *skb,
                                             struct sock *sk,
                                             struct flowi6 *fl6)
{
        struct dst_entry *dst, *dst2;
        struct flowi6 fl2;
        int err;

        err = ip6_dst_lookup(net, sk, &dst, fl6);
        if (err)
                return ERR_PTR(err);

        /*
         * We won't send icmp if the destination is known
         * anycast.
         */
        if (ipv6_anycast_destination(dst, &fl6->daddr)) {
                net_dbg_ratelimited("icmp6_send: acast source\n");
                dst_release(dst);
                return ERR_PTR(-EINVAL);
        }

        /* No need to clone since we're just using its address. */
        dst2 = dst;

        dst = xfrm_lookup(net, dst, flowi6_to_flowi(fl6), sk, 0);
        if (!IS_ERR(dst)) {
                if (dst != dst2)
                        return dst;
        } else {
                if (PTR_ERR(dst) == -EPERM)
                        dst = NULL;
                else
                        return dst;
        }

        err = xfrm_decode_session_reverse(skb, flowi6_to_flowi(&fl2), AF_INET6);
        if (err)
                goto relookup_failed;

        err = ip6_dst_lookup(net, sk, &dst2, &fl2);
        if (err)
                goto relookup_failed;

        dst2 = xfrm_lookup(net, dst2, flowi6_to_flowi(&fl2), sk, XFRM_LOOKUP_ICMP);
        if (!IS_ERR(dst2)) {
                dst_release(dst);
                dst = dst2;
        } else {
                err = PTR_ERR(dst2);
                if (err == -EPERM) {
                        dst_release(dst);
                        return dst2;
                } else
                        goto relookup_failed;
        }

relookup_failed:
        if (dst)
                return dst;
        return ERR_PTR(err);
}

static struct net_device *icmp6_dev(const struct sk_buff *skb)
{
        struct net_device *dev = skb->dev;

        /* for local traffic to local address, skb dev is the loopback
         * device. Check if there is a dst attached to the skb and if so
         * get the real device index. Same is needed for replies to a link
         * local address on a device enslaved to an L3 master device
         */
        if (unlikely(dev->ifindex == LOOPBACK_IFINDEX || netif_is_l3_master(skb->dev))) {
                const struct rt6_info *rt6 = skb_rt6_info(skb);

                if (rt6)
                        dev = rt6->rt6i_idev->dev;
        }

        return dev;
}

static int icmp6_iif(const struct sk_buff *skb)
{
        return icmp6_dev(skb)->ifindex;
}

/*
 *      Send an ICMP message in response to a packet in error
 */
void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
                const struct in6_addr *force_saddr)
{
        struct inet6_dev *idev = NULL;
        struct ipv6hdr *hdr = ipv6_hdr(skb);
        struct sock *sk;
        struct net *net;
        struct ipv6_pinfo *np;
        const struct in6_addr *saddr = NULL;
        struct dst_entry *dst;
        struct icmp6hdr tmp_hdr;
        struct flowi6 fl6;
        struct icmpv6_msg msg;
        struct ipcm6_cookie ipc6;
        int iif = 0;
        int addr_type = 0;
        int len;
        u32 mark;

        if ((u8 *)hdr < skb->head ||
            (skb_network_header(skb) + sizeof(*hdr)) > skb_tail_pointer(skb))
                return;

        if (!skb->dev)
                return;
        net = dev_net(skb->dev);
        mark = IP6_REPLY_MARK(net, skb->mark);
        /*
         *      Make sure we respect the rules
         *      i.e. RFC 1885 2.4(e)
         *      Rule (e.1) is enforced by not using icmp6_send
         *      in any code that processes icmp errors.
         */
        addr_type = ipv6_addr_type(&hdr->daddr);

        if (ipv6_chk_addr(net, &hdr->daddr, skb->dev, 0) ||
            ipv6_chk_acast_addr_src(net, skb->dev, &hdr->daddr))
                saddr = &hdr->daddr;

        /*
         *      Dest addr check
         */

        if (addr_type & IPV6_ADDR_MULTICAST || skb->pkt_type != PACKET_HOST) {
                if (type != ICMPV6_PKT_TOOBIG &&
                    !(type == ICMPV6_PARAMPROB &&
                      code == ICMPV6_UNK_OPTION &&
                      (opt_unrec(skb, info))))
                        return;

                saddr = NULL;
        }

        addr_type = ipv6_addr_type(&hdr->saddr);

        /*
         *      Source addr check
         */

        if (__ipv6_addr_needs_scope_id(addr_type)) {
                iif = icmp6_iif(skb);
        } else {
                /*
                 * The source device is used for looking up which routing table
                 * to use for sending an ICMP error.
                 */
                iif = l3mdev_master_ifindex(skb->dev);
        }

        /*
         *      Must not send error if the source does not uniquely
         *      identify a single node (RFC2463 Section 2.4).
         *      We check unspecified / multicast addresses here,
         *      and anycast addresses will be checked later.
         */
        if ((addr_type == IPV6_ADDR_ANY) || (addr_type & IPV6_ADDR_MULTICAST)) {
                net_dbg_ratelimited("icmp6_send: addr_any/mcast source [%pI6c > %pI6c]\n",
                                    &hdr->saddr, &hdr->daddr);
                return;
        }

        /*
         *      Never answer to a ICMP packet.
         */
        if (is_ineligible(skb)) {
                net_dbg_ratelimited("icmp6_send: no reply to icmp error [%pI6c > %pI6c]\n",
                                    &hdr->saddr, &hdr->daddr);
                return;
        }

        /* Needed by both icmp_global_allow and icmpv6_xmit_lock */
        local_bh_disable();

        /* Check global sysctl_icmp_msgs_per_sec ratelimit */
        if (!(skb->dev->flags & IFF_LOOPBACK) && !icmpv6_global_allow(net, type))
                goto out_bh_enable;

        mip6_addr_swap(skb);

        sk = icmpv6_xmit_lock(net);
        if (!sk)
                goto out_bh_enable;

        memset(&fl6, 0, sizeof(fl6));
        fl6.flowi6_proto = IPPROTO_ICMPV6;
        fl6.daddr = hdr->saddr;
        if (force_saddr)
                saddr = force_saddr;
        if (saddr) {
                fl6.saddr = *saddr;
        } else if (!icmpv6_rt_has_prefsrc(sk, type, &fl6)) {
                /* select a more meaningful saddr from input if */
                struct net_device *in_netdev;

                in_netdev = dev_get_by_index(net, IP6CB(skb)->iif);
                if (in_netdev) {
                        ipv6_dev_get_saddr(net, in_netdev, &fl6.daddr,
                                           inet6_sk(sk)->srcprefs,
                                           &fl6.saddr);
                        dev_put(in_netdev);
                }
        }
        fl6.flowi6_mark = mark;
        fl6.flowi6_oif = iif;
        fl6.fl6_icmp_type = type;
        fl6.fl6_icmp_code = code;
        fl6.flowi6_uid = sock_net_uid(net, NULL);
        fl6.mp_hash = rt6_multipath_hash(net, &fl6, skb, NULL);
        security_skb_classify_flow(skb, flowi6_to_flowi_common(&fl6));

        np = inet6_sk(sk);

        if (!icmpv6_xrlim_allow(sk, type, &fl6))
                goto out;

        tmp_hdr.icmp6_type = type;
        tmp_hdr.icmp6_code = code;
        tmp_hdr.icmp6_cksum = 0;
        tmp_hdr.icmp6_pointer = htonl(info);

        if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
                fl6.flowi6_oif = np->mcast_oif;
        else if (!fl6.flowi6_oif)
                fl6.flowi6_oif = np->ucast_oif;

        ipcm6_init_sk(&ipc6, np);
        ipc6.sockc.mark = mark;
        fl6.flowlabel = ip6_make_flowinfo(ipc6.tclass, fl6.flowlabel);

        dst = icmpv6_route_lookup(net, skb, sk, &fl6);
        if (IS_ERR(dst))
                goto out;

        ipc6.hlimit = ip6_sk_dst_hoplimit(np, &fl6, dst);

        msg.skb = skb;
        msg.offset = skb_network_offset(skb);
        msg.type = type;

        len = skb->len - msg.offset;
        len = min_t(unsigned int, len, IPV6_MIN_MTU - sizeof(struct ipv6hdr) - sizeof(struct icmp6hdr));
        if (len < 0) {
                net_dbg_ratelimited("icmp: len problem [%pI6c > %pI6c]\n",
                                    &hdr->saddr, &hdr->daddr);
                goto out_dst_release;
        }

        rcu_read_lock();
        idev = __in6_dev_get(skb->dev);

        if (ip6_append_data(sk, icmpv6_getfrag, &msg,
                            len + sizeof(struct icmp6hdr),
                            sizeof(struct icmp6hdr),
                            &ipc6, &fl6, (struct rt6_info *)dst,
                            MSG_DONTWAIT)) {
                ICMP6_INC_STATS(net, idev, ICMP6_MIB_OUTERRORS);
                ip6_flush_pending_frames(sk);
        } else {
                icmpv6_push_pending_frames(sk, &fl6, &tmp_hdr,
                                           len + sizeof(struct icmp6hdr));
        }
        rcu_read_unlock();
out_dst_release:
        dst_release(dst);
out:
        icmpv6_xmit_unlock(sk);
out_bh_enable:
        local_bh_enable();
}
EXPORT_SYMBOL(icmp6_send);

/* Slightly more convenient version of icmp6_send.
 */
void icmpv6_param_prob(struct sk_buff *skb, u8 code, int pos)
{
        icmp6_send(skb, ICMPV6_PARAMPROB, code, pos, NULL);
        kfree_skb(skb);
}

/* Generate icmpv6 with type/code ICMPV6_DEST_UNREACH/ICMPV6_ADDR_UNREACH
 * if sufficient data bytes are available
 * @nhs is the size of the tunnel header(s) :
 *  Either an IPv4 header for SIT encap
 *         an IPv4 header + GRE header for GRE encap
 */
int ip6_err_gen_icmpv6_unreach(struct sk_buff *skb, int nhs, int type,
                               unsigned int data_len)
{
        struct in6_addr temp_saddr;
        struct rt6_info *rt;
        struct sk_buff *skb2;
        u32 info = 0;

        if (!pskb_may_pull(skb, nhs + sizeof(struct ipv6hdr) + 8))
                return 1;

        /* RFC 4884 (partial) support for ICMP extensions */
        if (data_len < 128 || (data_len & 7) || skb->len < data_len)
                data_len = 0;

        skb2 = data_len ? skb_copy(skb, GFP_ATOMIC) : skb_clone(skb, GFP_ATOMIC);

        if (!skb2)
                return 1;

        skb_dst_drop(skb2);
        skb_pull(skb2, nhs);
        skb_reset_network_header(skb2);

        rt = rt6_lookup(dev_net(skb->dev), &ipv6_hdr(skb2)->saddr, NULL, 0,
                        skb, 0);

        if (rt && rt->dst.dev)
                skb2->dev = rt->dst.dev;

        ipv6_addr_set_v4mapped(ip_hdr(skb)->saddr, &temp_saddr);

        if (data_len) {
                /* RFC 4884 (partial) support :
                 * insert 0 padding at the end, before the extensions
                 */
                __skb_push(skb2, nhs);
                skb_reset_network_header(skb2);
                memmove(skb2->data, skb2->data + nhs, data_len - nhs);
                memset(skb2->data + data_len - nhs, 0, nhs);
                /* RFC 4884 4.5 : Length is measured in 64-bit words,
                 * and stored in reserved[0]
                 */
                info = (data_len/8) << 24;
        }
        if (type == ICMP_TIME_EXCEEDED)
                icmp6_send(skb2, ICMPV6_TIME_EXCEED, ICMPV6_EXC_HOPLIMIT,
                           info, &temp_saddr);
        else
                icmp6_send(skb2, ICMPV6_DEST_UNREACH, ICMPV6_ADDR_UNREACH,
                           info, &temp_saddr);
        if (rt)
                ip6_rt_put(rt);

        kfree_skb(skb2);

        return 0;
}
EXPORT_SYMBOL(ip6_err_gen_icmpv6_unreach);

static void icmpv6_echo_reply(struct sk_buff *skb)
{
        struct net *net = dev_net(skb->dev);
        struct sock *sk;
        struct inet6_dev *idev;
        struct ipv6_pinfo *np;
        const struct in6_addr *saddr = NULL;
        struct icmp6hdr *icmph = icmp6_hdr(skb);
        struct icmp6hdr tmp_hdr;
        struct flowi6 fl6;
        struct icmpv6_msg msg;
        struct dst_entry *dst;
        struct ipcm6_cookie ipc6;
        u32 mark = IP6_REPLY_MARK(net, skb->mark);
        bool acast;

        if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr) &&
            net->ipv6.sysctl.icmpv6_echo_ignore_multicast)
                return;

        saddr = &ipv6_hdr(skb)->daddr;

        acast = ipv6_anycast_destination(skb_dst(skb), saddr);
        if (acast && net->ipv6.sysctl.icmpv6_echo_ignore_anycast)
                return;

        if (!ipv6_unicast_destination(skb) &&
            !(net->ipv6.sysctl.anycast_src_echo_reply && acast))
                saddr = NULL;

        memcpy(&tmp_hdr, icmph, sizeof(tmp_hdr));
        tmp_hdr.icmp6_type = ICMPV6_ECHO_REPLY;

        memset(&fl6, 0, sizeof(fl6));
        if (net->ipv6.sysctl.flowlabel_reflect & FLOWLABEL_REFLECT_ICMPV6_ECHO_REPLIES)
                fl6.flowlabel = ip6_flowlabel(ipv6_hdr(skb));

        fl6.flowi6_proto = IPPROTO_ICMPV6;
        fl6.daddr = ipv6_hdr(skb)->saddr;
        if (saddr)
                fl6.saddr = *saddr;
        fl6.flowi6_oif = icmp6_iif(skb);
        fl6.fl6_icmp_type = ICMPV6_ECHO_REPLY;
        fl6.flowi6_mark = mark;
        fl6.flowi6_uid = sock_net_uid(net, NULL);
        security_skb_classify_flow(skb, flowi6_to_flowi_common(&fl6));

        local_bh_disable();
        sk = icmpv6_xmit_lock(net);
        if (!sk)
                goto out_bh_enable;
        np = inet6_sk(sk);

        if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
                fl6.flowi6_oif = np->mcast_oif;
        else if (!fl6.flowi6_oif)
                fl6.flowi6_oif = np->ucast_oif;

        if (ip6_dst_lookup(net, sk, &dst, &fl6))
                goto out;
        dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), sk, 0);
        if (IS_ERR(dst))
                goto out;

        /* Check the ratelimit */
        if ((!(skb->dev->flags & IFF_LOOPBACK) && !icmpv6_global_allow(net, ICMPV6_ECHO_REPLY)) ||
            !icmpv6_xrlim_allow(sk, ICMPV6_ECHO_REPLY, &fl6))
                goto out_dst_release;

        idev = __in6_dev_get(skb->dev);

        msg.skb = skb;
        msg.offset = 0;
        msg.type = ICMPV6_ECHO_REPLY;

        ipcm6_init_sk(&ipc6, np);
        ipc6.hlimit = ip6_sk_dst_hoplimit(np, &fl6, dst);
        ipc6.tclass = ipv6_get_dsfield(ipv6_hdr(skb));
        ipc6.sockc.mark = mark;

        if (ip6_append_data(sk, icmpv6_getfrag, &msg,
                            skb->len + sizeof(struct icmp6hdr),
                            sizeof(struct icmp6hdr), &ipc6, &fl6,
                            (struct rt6_info *)dst, MSG_DONTWAIT)) {
                __ICMP6_INC_STATS(net, idev, ICMP6_MIB_OUTERRORS);
                ip6_flush_pending_frames(sk);
        } else {
                icmpv6_push_pending_frames(sk, &fl6, &tmp_hdr,
                                           skb->len + sizeof(struct icmp6hdr));
        }
out_dst_release:
        dst_release(dst);
out:
        icmpv6_xmit_unlock(sk);
out_bh_enable:
        local_bh_enable();
}

void icmpv6_notify(struct sk_buff *skb, u8 type, u8 code, __be32 info)
{
        const struct inet6_protocol *ipprot;
        int inner_offset;
        __be16 frag_off;
        u8 nexthdr;
        struct net *net = dev_net(skb->dev);

        if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
                goto out;

        nexthdr = ((struct ipv6hdr *)skb->data)->nexthdr;
        if (ipv6_ext_hdr(nexthdr)) {
                /* now skip over extension headers */
                inner_offset = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr),
                                                &nexthdr, &frag_off);
                if (inner_offset < 0)
                        goto out;
        } else {
                inner_offset = sizeof(struct ipv6hdr);
        }

        /* Checkin header including 8 bytes of inner protocol header. */
        if (!pskb_may_pull(skb, inner_offset+8))
                goto out;

        /* BUGGG_FUTURE: we should try to parse exthdrs in this packet.
           Without this we will not able f.e. to make source routed
           pmtu discovery.
           Corresponding argument (opt) to notifiers is already added.
           --ANK (980726)
         */

        ipprot = rcu_dereference(inet6_protos[nexthdr]);
        if (ipprot && ipprot->err_handler)
                ipprot->err_handler(skb, NULL, type, code, inner_offset, info);

        raw6_icmp_error(skb, nexthdr, type, code, inner_offset, info);
        return;

out:
        __ICMP6_INC_STATS(net, __in6_dev_get(skb->dev), ICMP6_MIB_INERRORS);
}

/*
 *      Handle icmp messages
 */

static int icmpv6_rcv(struct sk_buff *skb)
{
        struct net *net = dev_net(skb->dev);
        struct net_device *dev = icmp6_dev(skb);
        struct inet6_dev *idev = __in6_dev_get(dev);
        const struct in6_addr *saddr, *daddr;
        struct icmp6hdr *hdr;
        u8 type;
        bool success = false;

        if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
                struct sec_path *sp = skb_sec_path(skb);
                int nh;

                if (!(sp && sp->xvec[sp->len - 1]->props.flags &
                                 XFRM_STATE_ICMP))
                        goto drop_no_count;

                if (!pskb_may_pull(skb, sizeof(*hdr) + sizeof(struct ipv6hdr)))
                        goto drop_no_count;

                nh = skb_network_offset(skb);
                skb_set_network_header(skb, sizeof(*hdr));

                if (!xfrm6_policy_check_reverse(NULL, XFRM_POLICY_IN, skb))
                        goto drop_no_count;

                skb_set_network_header(skb, nh);
        }

        __ICMP6_INC_STATS(dev_net(dev), idev, ICMP6_MIB_INMSGS);

        saddr = &ipv6_hdr(skb)->saddr;
        daddr = &ipv6_hdr(skb)->daddr;

        if (skb_checksum_validate(skb, IPPROTO_ICMPV6, ip6_compute_pseudo)) {
                net_dbg_ratelimited("ICMPv6 checksum failed [%pI6c > %pI6c]\n",
                                    saddr, daddr);
                goto csum_error;
        }

        if (!pskb_pull(skb, sizeof(*hdr)))
                goto discard_it;

        hdr = icmp6_hdr(skb);

        type = hdr->icmp6_type;

        ICMP6MSGIN_INC_STATS(dev_net(dev), idev, type);

        switch (type) {
        case ICMPV6_ECHO_REQUEST:
                if (!net->ipv6.sysctl.icmpv6_echo_ignore_all)
                        icmpv6_echo_reply(skb);
                break;

        case ICMPV6_ECHO_REPLY:
                success = ping_rcv(skb);
                break;

        case ICMPV6_PKT_TOOBIG:
                /* BUGGG_FUTURE: if packet contains rthdr, we cannot update
                   standard destination cache. Seems, only "advanced"
                   destination cache will allow to solve this problem
                   --ANK (980726)
                 */
                if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
                        goto discard_it;
                hdr = icmp6_hdr(skb);

                /* to notify */
                fallthrough;
        case ICMPV6_DEST_UNREACH:
        case ICMPV6_TIME_EXCEED:
        case ICMPV6_PARAMPROB:
                icmpv6_notify(skb, type, hdr->icmp6_code, hdr->icmp6_mtu);
                break;

        case NDISC_ROUTER_SOLICITATION:
        case NDISC_ROUTER_ADVERTISEMENT:
        case NDISC_NEIGHBOUR_SOLICITATION:
        case NDISC_NEIGHBOUR_ADVERTISEMENT:
        case NDISC_REDIRECT:
                ndisc_rcv(skb);
                break;

        case ICMPV6_MGM_QUERY:
                igmp6_event_query(skb);
                break;

        case ICMPV6_MGM_REPORT:
                igmp6_event_report(skb);
                break;

        case ICMPV6_MGM_REDUCTION:
        case ICMPV6_NI_QUERY:
        case ICMPV6_NI_REPLY:
        case ICMPV6_MLD2_REPORT:
        case ICMPV6_DHAAD_REQUEST:
        case ICMPV6_DHAAD_REPLY:
        case ICMPV6_MOBILE_PREFIX_SOL:
        case ICMPV6_MOBILE_PREFIX_ADV:
                break;

        default:
                /* informational */
                if (type & ICMPV6_INFOMSG_MASK)
                        break;

                net_dbg_ratelimited("icmpv6: msg of unknown type [%pI6c > %pI6c]\n",
                                    saddr, daddr);

                /*
                 * error of unknown type.
                 * must pass to upper level
                 */

                icmpv6_notify(skb, type, hdr->icmp6_code, hdr->icmp6_mtu);
        }

        /* until the v6 path can be better sorted assume failure and
         * preserve the status quo behaviour for the rest of the paths to here
         */
        if (success)
                consume_skb(skb);
        else
                kfree_skb(skb);

        return 0;

csum_error:
        __ICMP6_INC_STATS(dev_net(dev), idev, ICMP6_MIB_CSUMERRORS);
discard_it:
        __ICMP6_INC_STATS(dev_net(dev), idev, ICMP6_MIB_INERRORS);
drop_no_count:
        kfree_skb(skb);
        return 0;
}

void icmpv6_flow_init(struct sock *sk, struct flowi6 *fl6,
                      u8 type,
                      const struct in6_addr *saddr,

                      const struct in6_addr *daddr,
                      int oif)
{
        memset(fl6, 0, sizeof(*fl6));
        fl6->saddr = *saddr;
        fl6->daddr = *daddr;
        fl6->flowi6_proto       = IPPROTO_ICMPV6;
        fl6->fl6_icmp_type      = type;
        fl6->fl6_icmp_code      = 0;
        fl6->flowi6_oif         = oif;
        security_sk_classify_flow(sk, flowi6_to_flowi_common(fl6));
}

static void __net_exit icmpv6_sk_exit(struct net *net)
{
        int i;

        for_each_possible_cpu(i)
                inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv6.icmp_sk, i));
        free_percpu(net->ipv6.icmp_sk);
}

static int __net_init icmpv6_sk_init(struct net *net)
{
        struct sock *sk;
        int err, i;

        net->ipv6.icmp_sk = alloc_percpu(struct sock *);
        if (!net->ipv6.icmp_sk)
                return -ENOMEM;

        for_each_possible_cpu(i) {
                err = inet_ctl_sock_create(&sk, PF_INET6,
                                           SOCK_RAW, IPPROTO_ICMPV6, net);
                if (err < 0) {
                        pr_err("Failed to initialize the ICMP6 control socket (err %d)\n",
                               err);
                        goto fail;
                }

                *per_cpu_ptr(net->ipv6.icmp_sk, i) = sk;

                /* Enough space for 2 64K ICMP packets, including
                 * sk_buff struct overhead.
                 */
                sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
        }
        return 0;

 fail:
        icmpv6_sk_exit(net);
        return err;
}

static struct pernet_operations icmpv6_sk_ops = {
        .init = icmpv6_sk_init,
        .exit = icmpv6_sk_exit,
};

int __init icmpv6_init(void)
{
        int err;

        err = register_pernet_subsys(&icmpv6_sk_ops);
        if (err < 0)
                return err;

        err = -EAGAIN;
        if (inet6_add_protocol(&icmpv6_protocol, IPPROTO_ICMPV6) < 0)
                goto fail;

        err = inet6_register_icmp_sender(icmp6_send);
        if (err)
                goto sender_reg_err;
        return 0;

sender_reg_err:
        inet6_del_protocol(&icmpv6_protocol, IPPROTO_ICMPV6);
fail:
        pr_err("Failed to register ICMP6 protocol\n");
        unregister_pernet_subsys(&icmpv6_sk_ops);
        return err;
}

void icmpv6_cleanup(void)
{
        inet6_unregister_icmp_sender(icmp6_send);
        unregister_pernet_subsys(&icmpv6_sk_ops);
        inet6_del_protocol(&icmpv6_protocol, IPPROTO_ICMPV6);
}


static const struct icmp6_err {
        int err;
        int fatal;
} tab_unreach[] = {
        {       /* NOROUTE */
                .err    = ENETUNREACH,
                .fatal  = 0,
        },
        {       /* ADM_PROHIBITED */
                .err    = EACCES,
                .fatal  = 1,
        },
        {       /* Was NOT_NEIGHBOUR, now reserved */
                .err    = EHOSTUNREACH,
                .fatal  = 0,
        },
        {       /* ADDR_UNREACH */
                .err    = EHOSTUNREACH,
                .fatal  = 0,
        },
        {       /* PORT_UNREACH */
                .err    = ECONNREFUSED,
                .fatal  = 1,
        },
        {       /* POLICY_FAIL */
                .err    = EACCES,
                .fatal  = 1,
        },
        {       /* REJECT_ROUTE */
                .err    = EACCES,
                .fatal  = 1,
        },
};

int icmpv6_err_convert(u8 type, u8 code, int *err)
{
        int fatal = 0;

        *err = EPROTO;

        switch (type) {
        case ICMPV6_DEST_UNREACH:
                fatal = 1;
                if (code < ARRAY_SIZE(tab_unreach)) {
                        *err  = tab_unreach[code].err;
                        fatal = tab_unreach[code].fatal;
                }
                break;

        case ICMPV6_PKT_TOOBIG:
                *err = EMSGSIZE;
                break;

        case ICMPV6_PARAMPROB:
                *err = EPROTO;
                fatal = 1;
                break;

        case ICMPV6_TIME_EXCEED:
                *err = EHOSTUNREACH;
                break;
        }

        return fatal;
}
EXPORT_SYMBOL(icmpv6_err_convert);

#ifdef CONFIG_SYSCTL
static struct ctl_table ipv6_icmp_table_template[] = {
        {
                .procname       = "ratelimit",
                .data           = &init_net.ipv6.sysctl.icmpv6_time,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_ms_jiffies,
        },
        {
                .procname       = "echo_ignore_all",
                .data           = &init_net.ipv6.sysctl.icmpv6_echo_ignore_all,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler = proc_dointvec,
        },
        {
                .procname       = "echo_ignore_multicast",
                .data           = &init_net.ipv6.sysctl.icmpv6_echo_ignore_multicast,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler = proc_dointvec,
        },
        {
                .procname       = "echo_ignore_anycast",
                .data           = &init_net.ipv6.sysctl.icmpv6_echo_ignore_anycast,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler = proc_dointvec,
        },
        {
                .procname       = "ratemask",
                .data           = &init_net.ipv6.sysctl.icmpv6_ratemask_ptr,
                .maxlen         = ICMPV6_MSG_MAX + 1,
                .mode           = 0644,
                .proc_handler = proc_do_large_bitmap,
        },
        { },
};

struct ctl_table * __net_init ipv6_icmp_sysctl_init(struct net *net)
{
        struct ctl_table *table;

        table = kmemdup(ipv6_icmp_table_template,
                        sizeof(ipv6_icmp_table_template),
                        GFP_KERNEL);

        if (table) {
                table[0].data = &net->ipv6.sysctl.icmpv6_time;
                table[1].data = &net->ipv6.sysctl.icmpv6_echo_ignore_all;
                table[2].data = &net->ipv6.sysctl.icmpv6_echo_ignore_multicast;
                table[3].data = &net->ipv6.sysctl.icmpv6_echo_ignore_anycast;
                table[4].data = &net->ipv6.sysctl.icmpv6_ratemask_ptr;
        }
        return table;
}
#endif