// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      NET3:   Implementation of the ICMP protocol layer.
 *
 *              Alan Cox, <alan@lxorguk.ukuu.org.uk>
 *
 *      Some of the function names and the icmp unreach table for this
 *      module were derived from [icmp.c 1.0.11 06/02/93] by
 *      Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting.
 *      Other than that this module is a complete rewrite.
 *
 *      Fixes:
 *      Clemens Fruhwirth       :       introduce global icmp rate limiting
 *                                      with icmp type masking ability instead
 *                                      of broken per type icmp timeouts.
 *              Mike Shaver     :       RFC1122 checks.
 *              Alan Cox        :       Multicast ping reply as self.
 *              Alan Cox        :       Fix atomicity lockup in ip_build_xmit
 *                                      call.
 *              Alan Cox        :       Added 216,128 byte paths to the MTU
 *                                      code.
 *              Martin Mares    :       RFC1812 checks.
 *              Martin Mares    :       Can be configured to follow redirects
 *                                      if acting as a router _without_ a
 *                                      routing protocol (RFC 1812).
 *              Martin Mares    :       Echo requests may be configured to
 *                                      be ignored (RFC 1812).
 *              Martin Mares    :       Limitation of ICMP error message
 *                                      transmit rate (RFC 1812).
 *              Martin Mares    :       TOS and Precedence set correctly
 *                                      (RFC 1812).
 *              Martin Mares    :       Now copying as much data from the
 *                                      original packet as we can without
 *                                      exceeding 576 bytes (RFC 1812).
 *      Willy Konynenberg       :       Transparent proxying support.
 *              Keith Owens     :       RFC1191 correction for 4.2BSD based
 *                                      path MTU bug.
 *              Thomas Quinot   :       ICMP Dest Unreach codes up to 15 are
 *                                      valid (RFC 1812).
 *              Andi Kleen      :       Check all packet lengths properly
 *                                      and moved all kfree_skb() up to
 *                                      icmp_rcv.
 *              Andi Kleen      :       Move the rate limit bookkeeping
 *                                      into the dest entry and use a token
 *                                      bucket filter (thanks to ANK). Make
 *                                      the rates sysctl configurable.
 *              Yu Tianli       :       Fixed two ugly bugs in icmp_send
 *                                      - IP option length was accounted wrongly
 *                                      - ICMP header length was not accounted
 *                                        at all.
 *              Tristan Greaves :       Added sysctl option to ignore bogus
 *                                      broadcast responses from broken routers.
 *
 * To Fix:
 *
 *      - Should use skb_pull() instead of all the manual checking.
 *        This would also greatly simply some upper layer error handlers. --AK
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/types.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/fcntl.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <linux/string.h>
#include <linux/netfilter_ipv4.h>
#include <linux/slab.h>
#include <net/flow.h>
#include <net/snmp.h>
#include <net/ip.h>
#include <net/route.h>
#include <net/protocol.h>
#include <net/icmp.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/raw.h>
#include <net/ping.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <linux/init.h>
#include <linux/uaccess.h>
#include <net/checksum.h>
#include <net/xfrm.h>
#include <net/inet_common.h>
#include <net/ip_fib.h>
#include <net/l3mdev.h>
#include <net/addrconf.h>
#include <net/inet_dscp.h>
#define CREATE_TRACE_POINTS
#include <trace/events/icmp.h>

/*
 *      Build xmit assembly blocks
 */

struct icmp_bxm {
        struct sk_buff *skb;
        int offset;
        int data_len;

        struct {
                struct icmphdr icmph;
                __be32         times[3];
        } data;
        int head_len;

        /* Must be last as it ends in a flexible-array member. */
        struct ip_options_rcu replyopts;
};

/* An array of errno for error messages from dest unreach. */
/* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */

const struct icmp_err icmp_err_convert[] = {
        {
                .errno = ENETUNREACH,   /* ICMP_NET_UNREACH */
                .fatal = 0,
        },
        {
                .errno = EHOSTUNREACH,  /* ICMP_HOST_UNREACH */
                .fatal = 0,
        },
        {
                .errno = ENOPROTOOPT    /* ICMP_PROT_UNREACH */,
                .fatal = 1,
        },
        {
                .errno = ECONNREFUSED,  /* ICMP_PORT_UNREACH */
                .fatal = 1,
        },
        {
                .errno = EMSGSIZE,      /* ICMP_FRAG_NEEDED */
                .fatal = 0,
        },
        {
                .errno = EOPNOTSUPP,    /* ICMP_SR_FAILED */
                .fatal = 0,
        },
        {
                .errno = ENETUNREACH,   /* ICMP_NET_UNKNOWN */
                .fatal = 1,
        },
        {
                .errno = EHOSTDOWN,     /* ICMP_HOST_UNKNOWN */
                .fatal = 1,
        },
        {
                .errno = ENONET,        /* ICMP_HOST_ISOLATED */
                .fatal = 1,
        },
        {
                .errno = ENETUNREACH,   /* ICMP_NET_ANO */
                .fatal = 1,
        },
        {
                .errno = EHOSTUNREACH,  /* ICMP_HOST_ANO */
                .fatal = 1,
        },
        {
                .errno = ENETUNREACH,   /* ICMP_NET_UNR_TOS */
                .fatal = 0,
        },
        {
                .errno = EHOSTUNREACH,  /* ICMP_HOST_UNR_TOS */
                .fatal = 0,
        },
        {
                .errno = EHOSTUNREACH,  /* ICMP_PKT_FILTERED */
                .fatal = 1,
        },
        {
                .errno = EHOSTUNREACH,  /* ICMP_PREC_VIOLATION */
                .fatal = 1,
        },
        {
                .errno = EHOSTUNREACH,  /* ICMP_PREC_CUTOFF */
                .fatal = 1,
        },
};
EXPORT_SYMBOL(icmp_err_convert);

/*
 *      ICMP control array. This specifies what to do with each ICMP.
 */

struct icmp_control {
        enum skb_drop_reason (*handler)(struct sk_buff *skb);
        short   error;          /* This ICMP is classed as an error message */
};

static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];

static DEFINE_PER_CPU(struct sock *, ipv4_icmp_sk);

/* Called with BH disabled */
static inline struct sock *icmp_xmit_lock(struct net *net)
{
        struct sock *sk;

        sk = this_cpu_read(ipv4_icmp_sk);

        if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
                /* This can happen if the output path signals a
                 * dst_link_failure() for an outgoing ICMP packet.
                 */
                return NULL;
        }
        sock_net_set(sk, net);
        return sk;
}

static inline void icmp_xmit_unlock(struct sock *sk)
{
        sock_net_set(sk, &init_net);
        spin_unlock(&sk->sk_lock.slock);
}

/**
 * icmp_global_allow - Are we allowed to send one more ICMP message ?
 * @net: network namespace
 *
 * Uses a token bucket to limit our ICMP messages to ~sysctl_icmp_msgs_per_sec.
 * Returns false if we reached the limit and can not send another packet.
 * Works in tandem with icmp_global_consume().
 */
bool icmp_global_allow(struct net *net)
{
        u32 delta, now, oldstamp;
        int incr, new, old;

        /* Note: many cpus could find this condition true.
         * Then later icmp_global_consume() could consume more credits,
         * this is an acceptable race.
         */
        if (atomic_read(&net->ipv4.icmp_global_credit) > 0)
                return true;

        now = jiffies;
        oldstamp = READ_ONCE(net->ipv4.icmp_global_stamp);
        delta = min_t(u32, now - oldstamp, HZ);
        if (delta < HZ / 50)
                return false;

        incr = READ_ONCE(net->ipv4.sysctl_icmp_msgs_per_sec);
        incr = div_u64((u64)incr * delta, HZ);
        if (!incr)
                return false;

        if (cmpxchg(&net->ipv4.icmp_global_stamp, oldstamp, now) == oldstamp) {
                old = atomic_read(&net->ipv4.icmp_global_credit);
                do {
                        new = min(old + incr, READ_ONCE(net->ipv4.sysctl_icmp_msgs_burst));
                } while (!atomic_try_cmpxchg(&net->ipv4.icmp_global_credit, &old, new));
        }
        return true;
}
EXPORT_SYMBOL(icmp_global_allow);

void icmp_global_consume(struct net *net)
{
        int credits = get_random_u32_below(3);

        /* Note: this might make icmp_global.credit negative. */
        if (credits)
                atomic_sub(credits, &net->ipv4.icmp_global_credit);
}
EXPORT_SYMBOL(icmp_global_consume);

static bool icmpv4_mask_allow(struct net *net, int type, int code)
{
        if (type > NR_ICMP_TYPES)
                return true;

        /* Don't limit PMTU discovery. */
        if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
                return true;

        /* Limit if icmp type is enabled in ratemask. */
        if (!((1 << type) & READ_ONCE(net->ipv4.sysctl_icmp_ratemask)))
                return true;

        return false;
}

static bool icmpv4_global_allow(struct net *net, int type, int code,
                                bool *apply_ratelimit)
{
        if (icmpv4_mask_allow(net, type, code))
                return true;

        if (icmp_global_allow(net)) {
                *apply_ratelimit = true;
                return true;
        }
        __ICMP_INC_STATS(net, ICMP_MIB_RATELIMITGLOBAL);
        return false;
}

/*
 *      Send an ICMP frame.
 */

static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
                               struct flowi4 *fl4, int type, int code,
                               bool apply_ratelimit)
{
        struct dst_entry *dst = &rt->dst;
        struct inet_peer *peer;
        struct net_device *dev;
        int peer_timeout;
        bool rc = true;

        if (!apply_ratelimit)
                return true;

        peer_timeout = READ_ONCE(net->ipv4.sysctl_icmp_ratelimit);
        if (!peer_timeout)
                goto out;

        /* No rate limit on loopback */
        rcu_read_lock();
        dev = dst_dev_rcu(dst);
        if (dev && (dev->flags & IFF_LOOPBACK))
                goto out_unlock;

        peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr,
                               l3mdev_master_ifindex_rcu(dev));
        rc = inet_peer_xrlim_allow(peer, peer_timeout);

out_unlock:
        rcu_read_unlock();
out:
        if (!rc)
                __ICMP_INC_STATS(net, ICMP_MIB_RATELIMITHOST);
        else
                icmp_global_consume(net);
        return rc;
}

/*
 *      Maintain the counters used in the SNMP statistics for outgoing ICMP
 */
void icmp_out_count(struct net *net, unsigned char type)
{
        ICMPMSGOUT_INC_STATS(net, type);
        ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
}

/*
 *      Checksum each fragment, and on the first include the headers and final
 *      checksum.
 */
static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
                          struct sk_buff *skb)
{
        DEFINE_RAW_FLEX(struct icmp_bxm, icmp_param, replyopts.opt.__data,
                        IP_OPTIONS_DATA_FIXED_SIZE);
        __wsum csum;

        icmp_param = from;

        csum = skb_copy_and_csum_bits(icmp_param->skb,
                                      icmp_param->offset + offset,
                                      to, len);

        skb->csum = csum_block_add(skb->csum, csum, odd);
        if (icmp_pointers[icmp_param->data.icmph.type].error)
                nf_ct_attach(skb, icmp_param->skb);
        return 0;
}

static void icmp_push_reply(struct sock *sk,
                            struct icmp_bxm *icmp_param,
                            struct flowi4 *fl4,
                            struct ipcm_cookie *ipc, struct rtable **rt)
{
        struct sk_buff *skb;

        if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
                           icmp_param->data_len+icmp_param->head_len,
                           icmp_param->head_len,
                           ipc, rt, MSG_DONTWAIT) < 0) {
                __ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS);
                ip_flush_pending_frames(sk);
        } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
                struct icmphdr *icmph = icmp_hdr(skb);
                __wsum csum;
                struct sk_buff *skb1;

                csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
                                                 (char *)icmph,
                                                 icmp_param->head_len);
                skb_queue_walk(&sk->sk_write_queue, skb1) {
                        csum = csum_add(csum, skb1->csum);
                }
                icmph->checksum = csum_fold(csum);
                skb->ip_summed = CHECKSUM_NONE;
                ip_push_pending_frames(sk, fl4);
        }
}

/*
 *      Driving logic for building and sending ICMP messages.
 */

static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
{
        struct rtable *rt = skb_rtable(skb);
        struct net *net = dev_net_rcu(rt->dst.dev);
        bool apply_ratelimit = false;
        struct ipcm_cookie ipc;
        struct flowi4 fl4;
        struct sock *sk;
        __be32 daddr, saddr;
        u32 mark = IP4_REPLY_MARK(net, skb->mark);
        int type = icmp_param->data.icmph.type;
        int code = icmp_param->data.icmph.code;

        if (ip_options_echo(net, &icmp_param->replyopts.opt, skb))
                return;

        /* Needed by both icmpv4_global_allow and icmp_xmit_lock */
        local_bh_disable();

        /* is global icmp_msgs_per_sec exhausted ? */
        if (!icmpv4_global_allow(net, type, code, &apply_ratelimit))
                goto out_bh_enable;

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

        icmp_param->data.icmph.checksum = 0;

        ipcm_init(&ipc);
        ipc.tos = ip_hdr(skb)->tos;
        ipc.sockc.mark = mark;
        daddr = ipc.addr = ip_hdr(skb)->saddr;
        saddr = fib_compute_spec_dst(skb);

        if (icmp_param->replyopts.opt.optlen) {
                ipc.opt = &icmp_param->replyopts;
                if (ipc.opt->opt.srr)
                        daddr = icmp_param->replyopts.opt.faddr;
        }
        memset(&fl4, 0, sizeof(fl4));
        fl4.daddr = daddr;
        fl4.saddr = saddr;
        fl4.flowi4_mark = mark;
        fl4.flowi4_uid = sock_net_uid(net, NULL);
        fl4.flowi4_dscp = ip4h_dscp(ip_hdr(skb));
        fl4.flowi4_proto = IPPROTO_ICMP;
        fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev);
        security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
        rt = ip_route_output_key(net, &fl4);
        if (IS_ERR(rt))
                goto out_unlock;
        if (icmpv4_xrlim_allow(net, rt, &fl4, type, code, apply_ratelimit))
                icmp_push_reply(sk, icmp_param, &fl4, &ipc, &rt);
        ip_rt_put(rt);
out_unlock:
        icmp_xmit_unlock(sk);
out_bh_enable:
        local_bh_enable();
}

/*
 * The device used for looking up which routing table to use for sending an ICMP
 * error is preferably the source whenever it is set, which should ensure the
 * icmp error can be sent to the source host, else lookup using the routing
 * table of the destination device, else use the main routing table (index 0).
 */
static struct net_device *icmp_get_route_lookup_dev(struct sk_buff *skb)
{
        struct net_device *dev = skb->dev;
        const struct dst_entry *dst;

        if (dev)
                return dev;
        dst = skb_dst(skb);
        return dst ? dst_dev(dst) : NULL;
}

static struct rtable *icmp_route_lookup(struct net *net, struct flowi4 *fl4,
                                        struct sk_buff *skb_in,
                                        const struct iphdr *iph, __be32 saddr,
                                        dscp_t dscp, u32 mark, int type,
                                        int code, struct icmp_bxm *param)
{
        struct net_device *route_lookup_dev;
        struct dst_entry *dst, *dst2;
        struct rtable *rt, *rt2;
        struct flowi4 fl4_dec;
        int err;

        memset(fl4, 0, sizeof(*fl4));
        fl4->daddr = (param->replyopts.opt.srr ?
                      param->replyopts.opt.faddr : iph->saddr);
        fl4->saddr = saddr;
        fl4->flowi4_mark = mark;
        fl4->flowi4_uid = sock_net_uid(net, NULL);
        fl4->flowi4_dscp = dscp;
        fl4->flowi4_proto = IPPROTO_ICMP;
        fl4->fl4_icmp_type = type;
        fl4->fl4_icmp_code = code;
        route_lookup_dev = icmp_get_route_lookup_dev(skb_in);
        fl4->flowi4_oif = l3mdev_master_ifindex(route_lookup_dev);

        security_skb_classify_flow(skb_in, flowi4_to_flowi_common(fl4));
        rt = ip_route_output_key_hash(net, fl4, skb_in);
        if (IS_ERR(rt))
                return rt;

        /* No need to clone since we're just using its address. */
        rt2 = rt;

        dst = xfrm_lookup(net, &rt->dst,
                          flowi4_to_flowi(fl4), NULL, 0);
        rt = dst_rtable(dst);
        if (!IS_ERR(dst)) {
                if (rt != rt2)
                        return rt;
                if (inet_addr_type_dev_table(net, route_lookup_dev,
                                             fl4->daddr) == RTN_LOCAL)
                        return rt;
        } else if (PTR_ERR(dst) == -EPERM) {
                rt = NULL;
        } else {
                return rt;
        }
        err = xfrm_decode_session_reverse(net, skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
        if (err)
                goto relookup_failed;

        if (inet_addr_type_dev_table(net, route_lookup_dev,
                                     fl4_dec.saddr) == RTN_LOCAL) {
                rt2 = __ip_route_output_key(net, &fl4_dec);
                if (IS_ERR(rt2))
                        err = PTR_ERR(rt2);
        } else {
                struct flowi4 fl4_2 = {};
                unsigned long orefdst;

                fl4_2.daddr = fl4_dec.saddr;
                rt2 = ip_route_output_key(net, &fl4_2);
                if (IS_ERR(rt2)) {
                        err = PTR_ERR(rt2);
                        goto relookup_failed;
                }
                /* Ugh! */
                orefdst = skb_dstref_steal(skb_in);
                err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
                                     dscp, rt2->dst.dev) ? -EINVAL : 0;

                dst_release(&rt2->dst);
                rt2 = skb_rtable(skb_in);
                /* steal dst entry from skb_in, don't drop refcnt */
                skb_dstref_steal(skb_in);
                skb_dstref_restore(skb_in, orefdst);

                /*
                 * At this point, fl4_dec.daddr should NOT be local (we
                 * checked fl4_dec.saddr above). However, a race condition
                 * may occur if the address is added to the interface
                 * concurrently. In that case, ip_route_input() returns a
                 * LOCAL route with dst.output=ip_rt_bug, which must not
                 * be used for output.
                 */
                if (!err && rt2 && rt2->rt_type == RTN_LOCAL) {
                        net_warn_ratelimited("detected local route for %pI4 during ICMP sending, src %pI4\n",
                                             &fl4_dec.daddr, &fl4_dec.saddr);
                        dst_release(&rt2->dst);
                        err = -EINVAL;
                }
        }

        if (err)
                goto relookup_failed;

        dst2 = xfrm_lookup(net, &rt2->dst, flowi4_to_flowi(&fl4_dec), NULL,
                           XFRM_LOOKUP_ICMP);
        rt2 = dst_rtable(dst2);
        if (!IS_ERR(dst2)) {
                dst_release(&rt->dst);
                memcpy(fl4, &fl4_dec, sizeof(*fl4));
                rt = rt2;
        } else if (PTR_ERR(dst2) == -EPERM) {
                if (rt)
                        dst_release(&rt->dst);
                return rt2;
        } else {
                err = PTR_ERR(dst2);
                goto relookup_failed;
        }
        return rt;

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

struct icmp_ext_iio_addr4_subobj {
        __be16 afi;
        __be16 reserved;
        __be32 addr4;
};

static unsigned int icmp_ext_iio_len(void)
{
        return sizeof(struct icmp_extobj_hdr) +
                /* ifIndex */
                sizeof(__be32) +
                /* Interface Address Sub-Object */
                sizeof(struct icmp_ext_iio_addr4_subobj) +
                /* Interface Name Sub-Object. Length must be a multiple of 4
                 * bytes.
                 */
                ALIGN(sizeof(struct icmp_ext_iio_name_subobj), 4) +
                /* MTU */
                sizeof(__be32);
}

static unsigned int icmp_ext_max_len(u8 ext_objs)
{
        unsigned int ext_max_len;

        ext_max_len = sizeof(struct icmp_ext_hdr);

        if (ext_objs & BIT(ICMP_ERR_EXT_IIO_IIF))
                ext_max_len += icmp_ext_iio_len();

        return ext_max_len;
}

static __be32 icmp_ext_iio_addr4_find(const struct net_device *dev)
{
        struct in_device *in_dev;
        struct in_ifaddr *ifa;

        in_dev = __in_dev_get_rcu(dev);
        if (!in_dev)
                return 0;

        /* It is unclear from RFC 5837 which IP address should be chosen, but
         * it makes sense to choose a global unicast address.
         */
        in_dev_for_each_ifa_rcu(ifa, in_dev) {
                if (READ_ONCE(ifa->ifa_flags) & IFA_F_SECONDARY)
                        continue;
                if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
                    ipv4_is_multicast(ifa->ifa_address))
                        continue;
                return ifa->ifa_address;
        }

        return 0;
}

static void icmp_ext_iio_iif_append(struct net *net, struct sk_buff *skb,
                                    int iif)
{
        struct icmp_ext_iio_name_subobj *name_subobj;
        struct icmp_extobj_hdr *objh;
        struct net_device *dev;
        __be32 data;

        if (!iif)
                return;

        /* Add the fields in the order specified by RFC 5837. */
        objh = skb_put(skb, sizeof(*objh));
        objh->class_num = ICMP_EXT_OBJ_CLASS_IIO;
        objh->class_type = ICMP_EXT_CTYPE_IIO_ROLE(ICMP_EXT_CTYPE_IIO_ROLE_IIF);

        data = htonl(iif);
        skb_put_data(skb, &data, sizeof(__be32));
        objh->class_type |= ICMP_EXT_CTYPE_IIO_IFINDEX;

        rcu_read_lock();

        dev = dev_get_by_index_rcu(net, iif);
        if (!dev)
                goto out;

        data = icmp_ext_iio_addr4_find(dev);
        if (data) {
                struct icmp_ext_iio_addr4_subobj *addr4_subobj;

                addr4_subobj = skb_put_zero(skb, sizeof(*addr4_subobj));
                addr4_subobj->afi = htons(ICMP_AFI_IP);
                addr4_subobj->addr4 = data;
                objh->class_type |= ICMP_EXT_CTYPE_IIO_IPADDR;
        }

        name_subobj = skb_put_zero(skb, ALIGN(sizeof(*name_subobj), 4));
        name_subobj->len = ALIGN(sizeof(*name_subobj), 4);
        netdev_copy_name(dev, name_subobj->name);
        objh->class_type |= ICMP_EXT_CTYPE_IIO_NAME;

        data = htonl(READ_ONCE(dev->mtu));
        skb_put_data(skb, &data, sizeof(__be32));
        objh->class_type |= ICMP_EXT_CTYPE_IIO_MTU;

out:
        rcu_read_unlock();
        objh->length = htons(skb_tail_pointer(skb) - (unsigned char *)objh);
}

static void icmp_ext_objs_append(struct net *net, struct sk_buff *skb,
                                 u8 ext_objs, int iif)
{
        if (ext_objs & BIT(ICMP_ERR_EXT_IIO_IIF))
                icmp_ext_iio_iif_append(net, skb, iif);
}

static struct sk_buff *
icmp_ext_append(struct net *net, struct sk_buff *skb_in, struct icmphdr *icmph,
                unsigned int room, int iif)
{
        unsigned int payload_len, ext_max_len, ext_len;
        struct icmp_ext_hdr *ext_hdr;
        struct sk_buff *skb;
        u8 ext_objs;
        int nhoff;

        switch (icmph->type) {
        case ICMP_DEST_UNREACH:
        case ICMP_TIME_EXCEEDED:
        case ICMP_PARAMETERPROB:
                break;
        default:
                return NULL;
        }

        ext_objs = READ_ONCE(net->ipv4.sysctl_icmp_errors_extension_mask);
        if (!ext_objs)
                return NULL;

        ext_max_len = icmp_ext_max_len(ext_objs);
        if (ICMP_EXT_ORIG_DGRAM_MIN_LEN + ext_max_len > room)
                return NULL;

        skb = skb_clone(skb_in, GFP_ATOMIC);
        if (!skb)
                return NULL;

        nhoff = skb_network_offset(skb);
        payload_len = min(skb->len - nhoff, ICMP_EXT_ORIG_DGRAM_MIN_LEN);

        if (!pskb_network_may_pull(skb, payload_len))
                goto free_skb;

        if (pskb_trim(skb, nhoff + ICMP_EXT_ORIG_DGRAM_MIN_LEN) ||
            __skb_put_padto(skb, nhoff + ICMP_EXT_ORIG_DGRAM_MIN_LEN, false))
                goto free_skb;

        if (pskb_expand_head(skb, 0, ext_max_len, GFP_ATOMIC))
                goto free_skb;

        ext_hdr = skb_put_zero(skb, sizeof(*ext_hdr));
        ext_hdr->version = ICMP_EXT_VERSION_2;

        icmp_ext_objs_append(net, skb, ext_objs, iif);

        /* Do not send an empty extension structure. */
        ext_len = skb_tail_pointer(skb) - (unsigned char *)ext_hdr;
        if (ext_len == sizeof(*ext_hdr))
                goto free_skb;

        ext_hdr->checksum = ip_compute_csum(ext_hdr, ext_len);
        /* The length of the original datagram in 32-bit words (RFC 4884). */
        icmph->un.reserved[1] = ICMP_EXT_ORIG_DGRAM_MIN_LEN / sizeof(u32);

        return skb;

free_skb:
        consume_skb(skb);
        return NULL;
}

/*
 *      Send an ICMP message in response to a situation
 *
 *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
 *                MAY send more (we do).
 *                      MUST NOT change this header information.
 *                      MUST NOT reply to a multicast/broadcast IP address.
 *                      MUST NOT reply to a multicast/broadcast MAC address.
 *                      MUST reply to only the first fragment.
 */

void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
                 const struct inet_skb_parm *parm)
{
        DEFINE_RAW_FLEX(struct icmp_bxm, icmp_param, replyopts.opt.__data,
                        IP_OPTIONS_DATA_FIXED_SIZE);
        struct iphdr *iph;
        int room;
        struct rtable *rt = skb_rtable(skb_in);
        bool apply_ratelimit = false;
        struct sk_buff *ext_skb;
        struct ipcm_cookie ipc;
        struct flowi4 fl4;
        __be32 saddr;
        u8  tos;
        u32 mark;
        struct net *net;
        struct sock *sk;

        if (!rt)
                return;

        rcu_read_lock();

        if (rt->dst.dev)
                net = dev_net_rcu(rt->dst.dev);
        else if (skb_in->dev)
                net = dev_net_rcu(skb_in->dev);
        else
                goto out;

        /*
         *      Find the original header. It is expected to be valid, of course.
         *      Check this, icmp_send is called from the most obscure devices
         *      sometimes.
         */
        iph = ip_hdr(skb_in);

        if ((u8 *)iph < skb_in->head ||
            (skb_network_header(skb_in) + sizeof(*iph)) >
            skb_tail_pointer(skb_in))
                goto out;

        /*
         *      No replies to physical multicast/broadcast
         */
        if (skb_in->pkt_type != PACKET_HOST)
                goto out;

        /*
         *      Now check at the protocol level
         */
        if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
                goto out;

        /*
         *      Only reply to fragment 0. We byte re-order the constant
         *      mask for efficiency.
         */
        if (iph->frag_off & htons(IP_OFFSET))
                goto out;

        /*
         *      If we send an ICMP error to an ICMP error a mess would result..
         */
        if (icmp_pointers[type].error) {
                /*
                 *      We are an error, check if we are replying to an
                 *      ICMP error
                 */
                if (iph->protocol == IPPROTO_ICMP) {
                        u8 _inner_type, *itp;

                        itp = skb_header_pointer(skb_in,
                                                 skb_network_header(skb_in) +
                                                 (iph->ihl << 2) +
                                                 offsetof(struct icmphdr,
                                                          type) -
                                                 skb_in->data,
                                                 sizeof(_inner_type),
                                                 &_inner_type);
                        if (!itp)
                                goto out;

                        /*
                         *      Assume any unknown ICMP type is an error. This
                         *      isn't specified by the RFC, but think about it..
                         */
                        if (*itp > NR_ICMP_TYPES ||
                            icmp_pointers[*itp].error)
                                goto out;
                }
        }

        /* Needed by both icmpv4_global_allow and icmp_xmit_lock */
        local_bh_disable();

        /* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
         * incoming dev is loopback.  If outgoing dev change to not be
         * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
         */
        if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
              !icmpv4_global_allow(net, type, code, &apply_ratelimit))
                goto out_bh_enable;

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

        /*
         *      Construct source address and options.
         */

        saddr = iph->daddr;
        if (!(rt->rt_flags & RTCF_LOCAL)) {
                struct net_device *dev = NULL;

                rcu_read_lock();
                if (rt_is_input_route(rt) &&
                    READ_ONCE(net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr))
                        dev = dev_get_by_index_rcu(net, parm->iif ? parm->iif :
                                                   inet_iif(skb_in));

                if (dev)
                        saddr = inet_select_addr(dev, iph->saddr,
                                                 RT_SCOPE_LINK);
                else
                        saddr = 0;
                rcu_read_unlock();
        }

        tos = icmp_pointers[type].error ? (RT_TOS(iph->tos) |
                                           IPTOS_PREC_INTERNETCONTROL) :
                                           iph->tos;
        mark = IP4_REPLY_MARK(net, skb_in->mark);

        if (__ip_options_echo(net, &icmp_param->replyopts.opt, skb_in,
                              &parm->opt))
                goto out_unlock;


        /*
         *      Prepare data for ICMP header.
         */

        icmp_param->data.icmph.type      = type;
        icmp_param->data.icmph.code      = code;
        icmp_param->data.icmph.un.gateway = info;
        icmp_param->data.icmph.checksum  = 0;
        icmp_param->skb   = skb_in;
        icmp_param->offset = skb_network_offset(skb_in);
        ipcm_init(&ipc);
        ipc.tos = tos;
        ipc.addr = iph->saddr;
        ipc.opt = &icmp_param->replyopts;
        ipc.sockc.mark = mark;

        rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr,
                               inet_dsfield_to_dscp(tos), mark, type, code,
                               icmp_param);
        if (IS_ERR(rt))
                goto out_unlock;

        /* peer icmp_ratelimit */
        if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code, apply_ratelimit))
                goto ende;

        /* RFC says return as much as we can without exceeding 576 bytes. */

        room = dst4_mtu(&rt->dst);
        if (room > 576)
                room = 576;
        room -= sizeof(struct iphdr) + icmp_param->replyopts.opt.optlen;
        room -= sizeof(struct icmphdr);
        /* Guard against tiny mtu. We need to include at least one
         * IP network header for this message to make any sense.
         */
        if (room <= (int)sizeof(struct iphdr))
                goto ende;

        ext_skb = icmp_ext_append(net, skb_in, &icmp_param->data.icmph, room,
                                  parm->iif);
        if (ext_skb)
                icmp_param->skb = ext_skb;

        icmp_param->data_len = icmp_param->skb->len - icmp_param->offset;
        if (icmp_param->data_len > room)
                icmp_param->data_len = room;
        icmp_param->head_len = sizeof(struct icmphdr);

        /* if we don't have a source address at this point, fall back to the
         * dummy address instead of sending out a packet with a source address
         * of 0.0.0.0
         */
        if (!fl4.saddr)
                fl4.saddr = htonl(INADDR_DUMMY);

        trace_icmp_send(skb_in, type, code);

        icmp_push_reply(sk, icmp_param, &fl4, &ipc, &rt);

        if (ext_skb)
                consume_skb(ext_skb);
ende:
        ip_rt_put(rt);
out_unlock:
        icmp_xmit_unlock(sk);
out_bh_enable:
        local_bh_enable();
out:
        rcu_read_unlock();
}
EXPORT_SYMBOL(__icmp_send);

#if IS_ENABLED(CONFIG_NF_NAT)
#include <net/netfilter/nf_conntrack.h>
void icmp_ndo_send(struct sk_buff *skb_in, int type, int code, __be32 info)
{
        struct sk_buff *cloned_skb = NULL;
        enum ip_conntrack_info ctinfo;
        enum ip_conntrack_dir dir;
        struct inet_skb_parm parm;
        struct nf_conn *ct;
        __be32 orig_ip;

        memset(&parm, 0, sizeof(parm));
        ct = nf_ct_get(skb_in, &ctinfo);
        if (!ct || !(READ_ONCE(ct->status) & IPS_NAT_MASK)) {
                __icmp_send(skb_in, type, code, info, &parm);
                return;
        }

        if (skb_shared(skb_in))
                skb_in = cloned_skb = skb_clone(skb_in, GFP_ATOMIC);

        if (unlikely(!skb_in || skb_network_header(skb_in) < skb_in->head ||
            (skb_network_header(skb_in) + sizeof(struct iphdr)) >
            skb_tail_pointer(skb_in) || skb_ensure_writable(skb_in,
            skb_network_offset(skb_in) + sizeof(struct iphdr))))
                goto out;

        orig_ip = ip_hdr(skb_in)->saddr;
        dir = CTINFO2DIR(ctinfo);
        ip_hdr(skb_in)->saddr = ct->tuplehash[dir].tuple.src.u3.ip;
        __icmp_send(skb_in, type, code, info, &parm);
        ip_hdr(skb_in)->saddr = orig_ip;
out:
        consume_skb(cloned_skb);
}
EXPORT_SYMBOL(icmp_ndo_send);
#endif

static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
{
        const struct iphdr *iph = (const struct iphdr *)skb->data;
        const struct net_protocol *ipprot;
        int protocol = iph->protocol;

        /* Checkin full IP header plus 8 bytes of protocol to
         * avoid additional coding at protocol handlers.
         */
        if (!pskb_may_pull(skb, iph->ihl * 4 + 8))
                goto out;

        /* IPPROTO_RAW sockets are not supposed to receive anything. */
        if (protocol == IPPROTO_RAW)
                goto out;

        raw_icmp_error(skb, protocol, info);

        ipprot = rcu_dereference(inet_protos[protocol]);
        if (ipprot && ipprot->err_handler)
                ipprot->err_handler(skb, info);
        return;

out:
        __ICMP_INC_STATS(dev_net_rcu(skb->dev), ICMP_MIB_INERRORS);
}

static bool icmp_tag_validation(int proto)
{
        const struct net_protocol *ipprot;
        bool ok;

        rcu_read_lock();
        ipprot = rcu_dereference(inet_protos[proto]);
        ok = ipprot ? ipprot->icmp_strict_tag_validation : false;
        rcu_read_unlock();
        return ok;
}

/*
 *      Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and
 *      ICMP_PARAMETERPROB.
 */

static enum skb_drop_reason icmp_unreach(struct sk_buff *skb)
{
        enum skb_drop_reason reason = SKB_NOT_DROPPED_YET;
        const struct iphdr *iph;
        struct icmphdr *icmph;
        struct net *net;
        u32 info = 0;

        net = skb_dst_dev_net_rcu(skb);

        /*
         *      Incomplete header ?
         *      Only checks for the IP header, there should be an
         *      additional check for longer headers in upper levels.
         */

        if (!pskb_may_pull(skb, sizeof(struct iphdr)))
                goto out_err;

        icmph = icmp_hdr(skb);
        iph   = (const struct iphdr *)skb->data;

        if (iph->ihl < 5)  { /* Mangled header, drop. */
                reason = SKB_DROP_REASON_IP_INHDR;
                goto out_err;
        }

        switch (icmph->type) {
        case ICMP_DEST_UNREACH:
                switch (icmph->code & 15) {
                case ICMP_NET_UNREACH:
                case ICMP_HOST_UNREACH:
                case ICMP_PROT_UNREACH:
                case ICMP_PORT_UNREACH:
                        break;
                case ICMP_FRAG_NEEDED:
                        /* for documentation of the ip_no_pmtu_disc
                         * values please see
                         * Documentation/networking/ip-sysctl.rst
                         */
                        switch (READ_ONCE(net->ipv4.sysctl_ip_no_pmtu_disc)) {
                        default:
                                net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n",
                                                    &iph->daddr);
                                break;
                        case 2:
                                goto out;
                        case 3:
                                if (!icmp_tag_validation(iph->protocol))
                                        goto out;
                                fallthrough;
                        case 0:
                                info = ntohs(icmph->un.frag.mtu);
                        }
                        break;
                case ICMP_SR_FAILED:
                        net_dbg_ratelimited("%pI4: Source Route Failed\n",
                                            &iph->daddr);
                        break;
                default:
                        break;
                }
                if (icmph->code > NR_ICMP_UNREACH)
                        goto out;
                break;
        case ICMP_PARAMETERPROB:
                info = ntohl(icmph->un.gateway) >> 24;
                break;
        case ICMP_TIME_EXCEEDED:
                __ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS);
                if (icmph->code == ICMP_EXC_FRAGTIME)
                        goto out;
                break;
        }

        /*
         *      Throw it at our lower layers
         *
         *      RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
         *                header.
         *      RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
         *                transport layer.
         *      RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
         *                transport layer.
         */

        /*
         *      Check the other end isn't violating RFC 1122. Some routers send
         *      bogus responses to broadcast frames. If you see this message
         *      first check your netmask matches at both ends, if it does then
         *      get the other vendor to fix their kit.
         */

        if (!READ_ONCE(net->ipv4.sysctl_icmp_ignore_bogus_error_responses) &&
            inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) {
                net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
                                     &ip_hdr(skb)->saddr,
                                     icmph->type, icmph->code,
                                     &iph->daddr, skb->dev->name);
                goto out;
        }

        icmp_socket_deliver(skb, info);

out:
        return reason;
out_err:
        __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
        return reason ?: SKB_DROP_REASON_NOT_SPECIFIED;
}


/*
 *      Handle ICMP_REDIRECT.
 */

static enum skb_drop_reason icmp_redirect(struct sk_buff *skb)
{
        if (skb->len < sizeof(struct iphdr)) {
                __ICMP_INC_STATS(dev_net_rcu(skb->dev), ICMP_MIB_INERRORS);
                return SKB_DROP_REASON_PKT_TOO_SMALL;
        }

        if (!pskb_may_pull(skb, sizeof(struct iphdr))) {
                /* there aught to be a stat */
                return SKB_DROP_REASON_NOMEM;
        }

        icmp_socket_deliver(skb, ntohl(icmp_hdr(skb)->un.gateway));
        return SKB_NOT_DROPPED_YET;
}

/*
 *      Handle ICMP_ECHO ("ping") and ICMP_EXT_ECHO ("PROBE") requests.
 *
 *      RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
 *                requests.
 *      RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
 *                included in the reply.
 *      RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
 *                echo requests, MUST have default=NOT.
 *      RFC 8335: 8 MUST have a config option to enable/disable ICMP
 *                Extended Echo Functionality, MUST be disabled by default
 *      See also WRT handling of options once they are done and working.
 */

static enum skb_drop_reason icmp_echo(struct sk_buff *skb)
{
        DEFINE_RAW_FLEX(struct icmp_bxm, icmp_param, replyopts.opt.__data,
                        IP_OPTIONS_DATA_FIXED_SIZE);
        struct net *net;

        net = skb_dst_dev_net_rcu(skb);
        /* should there be an ICMP stat for ignored echos? */
        if (READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_all))
                return SKB_NOT_DROPPED_YET;

        icmp_param->data.icmph     = *icmp_hdr(skb);
        icmp_param->skb            = skb;
        icmp_param->offset         = 0;
        icmp_param->data_len       = skb->len;
        icmp_param->head_len       = sizeof(struct icmphdr);

        if (icmp_param->data.icmph.type == ICMP_ECHO)
                icmp_param->data.icmph.type = ICMP_ECHOREPLY;
        else if (!icmp_build_probe(skb, &icmp_param->data.icmph))
                return SKB_NOT_DROPPED_YET;

        icmp_reply(icmp_param, skb);
        return SKB_NOT_DROPPED_YET;
}

/*      Helper for icmp_echo and icmpv6_echo_reply.
 *      Searches for net_device that matches PROBE interface identifier
 *              and builds PROBE reply message in icmphdr.
 *
 *      Returns false if PROBE responses are disabled via sysctl
 */

bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr)
{
        struct net *net = dev_net_rcu(skb->dev);
        struct icmp_ext_hdr *ext_hdr, _ext_hdr;
        struct icmp_ext_echo_iio *iio, _iio;
        struct inet6_dev *in6_dev;
        struct in_device *in_dev;
        struct net_device *dev;
        char buff[IFNAMSIZ];
        u16 ident_len;
        u8 status;

        if (!READ_ONCE(net->ipv4.sysctl_icmp_echo_enable_probe))
                return false;

        /* We currently only support probing interfaces on the proxy node
         * Check to ensure L-bit is set
         */
        if (!(ntohs(icmphdr->un.echo.sequence) & 1))
                return false;
        /* Clear status bits in reply message */
        icmphdr->un.echo.sequence &= htons(0xFF00);
        if (icmphdr->type == ICMP_EXT_ECHO)
                icmphdr->type = ICMP_EXT_ECHOREPLY;
        else
                icmphdr->type = ICMPV6_EXT_ECHO_REPLY;
        ext_hdr = skb_header_pointer(skb, 0, sizeof(_ext_hdr), &_ext_hdr);
        /* Size of iio is class_type dependent.
         * Only check header here and assign length based on ctype in the switch statement
         */
        iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(iio->extobj_hdr), &_iio);
        if (!ext_hdr || !iio)
                goto send_mal_query;
        if (ntohs(iio->extobj_hdr.length) <= sizeof(iio->extobj_hdr) ||
            ntohs(iio->extobj_hdr.length) > sizeof(_iio))
                goto send_mal_query;
        ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio->extobj_hdr);
        iio = skb_header_pointer(skb, sizeof(_ext_hdr),
                                 sizeof(iio->extobj_hdr) + ident_len, &_iio);
        if (!iio)
                goto send_mal_query;

        status = 0;
        dev = NULL;
        switch (iio->extobj_hdr.class_type) {
        case ICMP_EXT_ECHO_CTYPE_NAME:
                if (ident_len >= IFNAMSIZ)
                        goto send_mal_query;
                memset(buff, 0, sizeof(buff));
                memcpy(buff, &iio->ident.name, ident_len);
                dev = dev_get_by_name(net, buff);
                break;
        case ICMP_EXT_ECHO_CTYPE_INDEX:
                if (ident_len != sizeof(iio->ident.ifindex))
                        goto send_mal_query;
                dev = dev_get_by_index(net, ntohl(iio->ident.ifindex));
                break;
        case ICMP_EXT_ECHO_CTYPE_ADDR:
                if (ident_len < sizeof(iio->ident.addr.ctype3_hdr) ||
                    ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
                                 iio->ident.addr.ctype3_hdr.addrlen)
                        goto send_mal_query;
                switch (ntohs(iio->ident.addr.ctype3_hdr.afi)) {
                case ICMP_AFI_IP:
                        if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in_addr))
                                goto send_mal_query;
                        dev = ip_dev_find(net, iio->ident.addr.ip_addr.ipv4_addr);
                        break;
#if IS_ENABLED(CONFIG_IPV6)
                case ICMP_AFI_IP6:
                        if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in6_addr))
                                goto send_mal_query;
                        dev = ipv6_stub->ipv6_dev_find(net, &iio->ident.addr.ip_addr.ipv6_addr, dev);
                        dev_hold(dev);
                        break;
#endif
                default:
                        goto send_mal_query;
                }
                break;
        default:
                goto send_mal_query;
        }
        if (!dev) {
                icmphdr->code = ICMP_EXT_CODE_NO_IF;
                return true;
        }
        /* Fill bits in reply message */
        if (dev->flags & IFF_UP)
                status |= ICMP_EXT_ECHOREPLY_ACTIVE;

        in_dev = __in_dev_get_rcu(dev);
        if (in_dev && rcu_access_pointer(in_dev->ifa_list))
                status |= ICMP_EXT_ECHOREPLY_IPV4;

        in6_dev = __in6_dev_get(dev);
        if (in6_dev && !list_empty(&in6_dev->addr_list))
                status |= ICMP_EXT_ECHOREPLY_IPV6;

        dev_put(dev);
        icmphdr->un.echo.sequence |= htons(status);
        return true;
send_mal_query:
        icmphdr->code = ICMP_EXT_CODE_MAL_QUERY;
        return true;
}
EXPORT_SYMBOL_GPL(icmp_build_probe);

/*
 *      Handle ICMP Timestamp requests.
 *      RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
 *                SHOULD be in the kernel for minimum random latency.
 *                MUST be accurate to a few minutes.
 *                MUST be updated at least at 15Hz.
 */
static enum skb_drop_reason icmp_timestamp(struct sk_buff *skb)
{
        DEFINE_RAW_FLEX(struct icmp_bxm, icmp_param, replyopts.opt.__data,
                        IP_OPTIONS_DATA_FIXED_SIZE);
        /*
         *      Too short.
         */
        if (skb->len < 4)
                goto out_err;

        /*
         *      Fill in the current time as ms since midnight UT:
         */
        icmp_param->data.times[1] = inet_current_timestamp();
        icmp_param->data.times[2] = icmp_param->data.times[1];

        BUG_ON(skb_copy_bits(skb, 0, &icmp_param->data.times[0], 4));

        icmp_param->data.icmph     = *icmp_hdr(skb);
        icmp_param->data.icmph.type = ICMP_TIMESTAMPREPLY;
        icmp_param->data.icmph.code = 0;
        icmp_param->skb            = skb;
        icmp_param->offset         = 0;
        icmp_param->data_len       = 0;
        icmp_param->head_len       = sizeof(struct icmphdr) + 12;
        icmp_reply(icmp_param, skb);
        return SKB_NOT_DROPPED_YET;

out_err:
        __ICMP_INC_STATS(skb_dst_dev_net_rcu(skb), ICMP_MIB_INERRORS);
        return SKB_DROP_REASON_PKT_TOO_SMALL;
}

static enum skb_drop_reason icmp_discard(struct sk_buff *skb)
{
        /* pretend it was a success */
        return SKB_NOT_DROPPED_YET;
}

/*
 *      Deal with incoming ICMP packets.
 */
int icmp_rcv(struct sk_buff *skb)
{
        enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
        struct rtable *rt = skb_rtable(skb);
        struct net *net = dev_net_rcu(rt->dst.dev);
        struct icmphdr *icmph;

        if (!xfrm4_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)) {
                        reason = SKB_DROP_REASON_XFRM_POLICY;
                        goto drop;
                }

                if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
                        goto drop;

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

                if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN,
                                                skb)) {
                        reason = SKB_DROP_REASON_XFRM_POLICY;
                        goto drop;
                }

                skb_set_network_header(skb, nh);
        }

        __ICMP_INC_STATS(net, ICMP_MIB_INMSGS);

        if (skb_checksum_simple_validate(skb))
                goto csum_error;

        if (!pskb_pull(skb, sizeof(*icmph)))
                goto error;

        icmph = icmp_hdr(skb);

        ICMPMSGIN_INC_STATS(net, icmph->type);

        /* Check for ICMP Extended Echo (PROBE) messages */
        if (icmph->type == ICMP_EXT_ECHO) {
                /* We can't use icmp_pointers[].handler() because it is an array of
                 * size NR_ICMP_TYPES + 1 (19 elements) and PROBE has code 42.
                 */
                reason = icmp_echo(skb);
                goto reason_check;
        }

        /*
         *      Parse the ICMP message
         */

        if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
                /*
                 *      RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
                 *        silently ignored (we let user decide with a sysctl).
                 *      RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
                 *        discarded if to broadcast/multicast.
                 */
                if ((icmph->type == ICMP_ECHO ||
                     icmph->type == ICMP_TIMESTAMP) &&
                    READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_broadcasts)) {
                        reason = SKB_DROP_REASON_INVALID_PROTO;
                        goto error;
                }
                if (icmph->type != ICMP_ECHO &&
                    icmph->type != ICMP_TIMESTAMP &&
                    icmph->type != ICMP_ADDRESS &&
                    icmph->type != ICMP_ADDRESSREPLY) {
                        reason = SKB_DROP_REASON_INVALID_PROTO;
                        goto error;
                }
        }

        if (icmph->type == ICMP_EXT_ECHOREPLY ||
            icmph->type == ICMP_ECHOREPLY) {
                reason = ping_rcv(skb);
                return reason ? NET_RX_DROP : NET_RX_SUCCESS;
        }

        /*
         *      18 is the highest 'known' ICMP type. Anything else is a mystery
         *
         *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
         *                discarded.
         */
        if (icmph->type > NR_ICMP_TYPES) {
                reason = SKB_DROP_REASON_UNHANDLED_PROTO;
                goto error;
        }

        reason = icmp_pointers[icmph->type].handler(skb);
reason_check:
        if (!reason)  {
                consume_skb(skb);
                return NET_RX_SUCCESS;
        }

drop:
        kfree_skb_reason(skb, reason);
        return NET_RX_DROP;
csum_error:
        reason = SKB_DROP_REASON_ICMP_CSUM;
        __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
error:
        __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
        goto drop;
}

static bool ip_icmp_error_rfc4884_validate(const struct sk_buff *skb, int off)
{
        struct icmp_extobj_hdr *objh, _objh;
        struct icmp_ext_hdr *exth, _exth;
        u16 olen;

        exth = skb_header_pointer(skb, off, sizeof(_exth), &_exth);
        if (!exth)
                return false;
        if (exth->version != 2)
                return true;

        if (exth->checksum &&
            csum_fold(skb_checksum(skb, off, skb->len - off, 0)))
                return false;

        off += sizeof(_exth);
        while (off < skb->len) {
                objh = skb_header_pointer(skb, off, sizeof(_objh), &_objh);
                if (!objh)
                        return false;

                olen = ntohs(objh->length);
                if (olen < sizeof(_objh))
                        return false;

                off += olen;
                if (off > skb->len)
                        return false;
        }

        return true;
}

void ip_icmp_error_rfc4884(const struct sk_buff *skb,
                           struct sock_ee_data_rfc4884 *out,
                           int thlen, int off)
{
        int hlen;

        /* original datagram headers: end of icmph to payload (skb->data) */
        hlen = -skb_transport_offset(skb) - thlen;

        /* per rfc 4884: minimal datagram length of 128 bytes */
        if (off < 128 || off < hlen)
                return;

        /* kernel has stripped headers: return payload offset in bytes */
        off -= hlen;
        if (off + sizeof(struct icmp_ext_hdr) > skb->len)
                return;

        out->len = off;

        if (!ip_icmp_error_rfc4884_validate(skb, off))
                out->flags |= SO_EE_RFC4884_FLAG_INVALID;
}
EXPORT_SYMBOL_GPL(ip_icmp_error_rfc4884);

int icmp_err(struct sk_buff *skb, u32 info)
{
        struct iphdr *iph = (struct iphdr *)skb->data;
        int offset = iph->ihl<<2;
        struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
        struct net *net = dev_net_rcu(skb->dev);
        int type = icmp_hdr(skb)->type;
        int code = icmp_hdr(skb)->code;

        /*
         * Use ping_err to handle all icmp errors except those
         * triggered by ICMP_ECHOREPLY which sent from kernel.
         */
        if (icmph->type != ICMP_ECHOREPLY) {
                ping_err(skb, offset, info);
                return 0;
        }

        if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
                ipv4_update_pmtu(skb, net, info, 0, IPPROTO_ICMP);
        else if (type == ICMP_REDIRECT)
                ipv4_redirect(skb, net, 0, IPPROTO_ICMP);

        return 0;
}

/*
 *      This table is the definition of how we handle ICMP.
 */
static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
        [ICMP_ECHOREPLY] = {
                .handler = ping_rcv,
        },
        [1] = {
                .handler = icmp_discard,
                .error = 1,
        },
        [2] = {
                .handler = icmp_discard,
                .error = 1,
        },
        [ICMP_DEST_UNREACH] = {
                .handler = icmp_unreach,
                .error = 1,
        },
        [ICMP_SOURCE_QUENCH] = {
                .handler = icmp_unreach,
                .error = 1,
        },
        [ICMP_REDIRECT] = {
                .handler = icmp_redirect,
                .error = 1,
        },
        [6] = {
                .handler = icmp_discard,
                .error = 1,
        },
        [7] = {
                .handler = icmp_discard,
                .error = 1,
        },
        [ICMP_ECHO] = {
                .handler = icmp_echo,
        },
        [9] = {
                .handler = icmp_discard,
                .error = 1,
        },
        [10] = {
                .handler = icmp_discard,
                .error = 1,
        },
        [ICMP_TIME_EXCEEDED] = {
                .handler = icmp_unreach,
                .error = 1,
        },
        [ICMP_PARAMETERPROB] = {
                .handler = icmp_unreach,
                .error = 1,
        },
        [ICMP_TIMESTAMP] = {
                .handler = icmp_timestamp,
        },
        [ICMP_TIMESTAMPREPLY] = {
                .handler = icmp_discard,
        },
        [ICMP_INFO_REQUEST] = {
                .handler = icmp_discard,
        },
        [ICMP_INFO_REPLY] = {
                .handler = icmp_discard,
        },
        [ICMP_ADDRESS] = {
                .handler = icmp_discard,
        },
        [ICMP_ADDRESSREPLY] = {
                .handler = icmp_discard,
        },
};

static int __net_init icmp_sk_init(struct net *net)
{
        /* Control parameters for ECHO replies. */
        net->ipv4.sysctl_icmp_echo_ignore_all = 0;
        net->ipv4.sysctl_icmp_echo_enable_probe = 0;
        net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;

        /* Control parameter - ignore bogus broadcast responses? */
        net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;

        /*
         *      Configurable global rate limit.
         *
         *      ratelimit defines tokens/packet consumed for dst->rate_token
         *      bucket ratemask defines which icmp types are ratelimited by
         *      setting it's bit position.
         *
         *      default:
         *      dest unreachable (3), source quench (4),
         *      time exceeded (11), parameter problem (12)
         */

        net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
        net->ipv4.sysctl_icmp_ratemask = 0x1818;
        net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
        net->ipv4.sysctl_icmp_errors_extension_mask = 0;
        net->ipv4.sysctl_icmp_msgs_per_sec = 1000;
        net->ipv4.sysctl_icmp_msgs_burst = 50;

        return 0;
}

static struct pernet_operations __net_initdata icmp_sk_ops = {
       .init = icmp_sk_init,
};

int __init icmp_init(void)
{
        int err, i;

        for_each_possible_cpu(i) {
                struct sock *sk;

                err = inet_ctl_sock_create(&sk, PF_INET,
                                           SOCK_RAW, IPPROTO_ICMP, &init_net);
                if (err < 0)
                        return err;

                per_cpu(ipv4_icmp_sk, i) = sk;

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

                /*
                 * Speedup sock_wfree()
                 */
                sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
                inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
        }
        return register_pernet_subsys(&icmp_sk_ops);
}