icmp.c

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/*
 *  NET3:   Implementation of the ICMP protocol layer.
 *
 *      Alan Cox, <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 *
 *  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/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 <asm/uaccess.h>
#include <net/checksum.h>
#include <net/xfrm.h>
#include <net/inet_common.h>
#include <net/ip_fib.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;
    struct ip_options_data 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 {
    void (*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];

/*
 *  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 *icmp_sk(struct net *net)
{
    return net->ipv4.icmp_sk[smp_processor_id()];
}

static inline struct sock *icmp_xmit_lock(struct net *net)
{
    struct sock *sk;

    local_bh_disable();

    sk = icmp_sk(net);

    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.
         */
        local_bh_enable();
        return NULL;
    }
    return sk;
}

static inline void icmp_xmit_unlock(struct sock *sk)
{
    spin_unlock_bh(&sk->sk_lock.slock);
}

/*
 *  Send an ICMP frame.
 */

static inline bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
                      struct flowi4 *fl4, int type, int code)
{
    struct dst_entry *dst = &rt->dst;
    bool rc = true;

    if (type > NR_ICMP_TYPES)
        goto out;

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

    /* No rate limit on loopback */
    if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
        goto out;

    /* Limit if icmp type is enabled in ratemask. */
    if ((1 << type) & net->ipv4.sysctl_icmp_ratemask) {
        struct inet_peer *peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, 1);
        rc = inet_peer_xrlim_allow(peer,
                       net->ipv4.sysctl_icmp_ratelimit);
        if (peer)
            inet_putpeer(peer);
    }
out:
    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)
{
    struct icmp_bxm *icmp_param = (struct icmp_bxm *)from;
    __wsum csum;

    csum = skb_copy_and_csum_bits(icmp_param->skb,
                      icmp_param->offset + offset,
                      to, len, 0);

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

    sk = icmp_sk(dev_net((*rt)->dst.dev));
    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_BH(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 = 0;
        struct sk_buff *skb1;

        skb_queue_walk(&sk->sk_write_queue, skb1) {
            csum = csum_add(csum, skb1->csum);
        }
        csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
                         (char *)icmph,
                         icmp_param->head_len, 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 ipcm_cookie ipc;
    struct rtable *rt = skb_rtable(skb);
    struct net *net = dev_net(rt->dst.dev);
    struct flowi4 fl4;
    struct sock *sk;
    struct inet_sock *inet;
    __be32 daddr, saddr;

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

    sk = icmp_xmit_lock(net);
    if (sk == NULL)
        return;
    inet = inet_sk(sk);

    icmp_param->data.icmph.checksum = 0;

    inet->tos = ip_hdr(skb)->tos;
    daddr = ipc.addr = ip_hdr(skb)->saddr;
    saddr = fib_compute_spec_dst(skb);
    ipc.opt = NULL;
    ipc.tx_flags = 0;
    if (icmp_param->replyopts.opt.opt.optlen) {
        ipc.opt = &icmp_param->replyopts.opt;
        if (ipc.opt->opt.srr)
            daddr = icmp_param->replyopts.opt.opt.faddr;
    }
    memset(&fl4, 0, sizeof(fl4));
    fl4.daddr = daddr;
    fl4.saddr = saddr;
    fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
    fl4.flowi4_proto = IPPROTO_ICMP;
    security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
    rt = ip_route_output_key(net, &fl4);
    if (IS_ERR(rt))
        goto out_unlock;
    if (icmpv4_xrlim_allow(net, rt, &fl4, icmp_param->data.icmph.type,
                   icmp_param->data.icmph.code))
        icmp_push_reply(icmp_param, &fl4, &ipc, &rt);
    ip_rt_put(rt);
out_unlock:
    icmp_xmit_unlock(sk);
}

static struct rtable *icmp_route_lookup(struct net *net,
                    struct flowi4 *fl4,
                    struct sk_buff *skb_in,
                    const struct iphdr *iph,
                    __be32 saddr, u8 tos,
                    int type, int code,
                    struct icmp_bxm *param)
{
    struct rtable *rt, *rt2;
    struct flowi4 fl4_dec;
    int err;

    memset(fl4, 0, sizeof(*fl4));
    fl4->daddr = (param->replyopts.opt.opt.srr ?
              param->replyopts.opt.opt.faddr : iph->saddr);
    fl4->saddr = saddr;
    fl4->flowi4_tos = RT_TOS(tos);
    fl4->flowi4_proto = IPPROTO_ICMP;
    fl4->fl4_icmp_type = type;
    fl4->fl4_icmp_code = code;
    security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4));
    rt = __ip_route_output_key(net, fl4);
    if (IS_ERR(rt))
        return rt;

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

    rt = (struct rtable *) xfrm_lookup(net, &rt->dst,
                       flowi4_to_flowi(fl4), NULL, 0);
    if (!IS_ERR(rt)) {
        if (rt != rt2)
            return rt;
    } else if (PTR_ERR(rt) == -EPERM) {
        rt = NULL;
    } else
        return rt;

    err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
    if (err)
        goto relookup_failed;

    if (inet_addr_type(net, 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_in->_skb_refdst; /* save old refdst */
        err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
                     RT_TOS(tos), rt2->dst.dev);

        dst_release(&rt2->dst);
        rt2 = skb_rtable(skb_in);
        skb_in->_skb_refdst = orefdst; /* restore old refdst */
    }

    if (err)
        goto relookup_failed;

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

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

/*
 *  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)
{
    struct iphdr *iph;
    int room;
    struct icmp_bxm icmp_param;
    struct rtable *rt = skb_rtable(skb_in);
    struct ipcm_cookie ipc;
    struct flowi4 fl4;
    __be32 saddr;
    u8  tos;
    struct net *net;
    struct sock *sk;

    if (!rt)
        goto out;
    net = dev_net(rt->dst.dev);

    /*
     *  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_in->network_header + sizeof(*iph)) > skb_in->tail)
        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 == NULL)
                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;
        }
    }

    sk = icmp_xmit_lock(net);
    if (sk == NULL)
        return;

    /*
     *  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) &&
            net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr)
            dev = dev_get_by_index_rcu(net, inet_iif(skb_in));

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

    tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) |
                       IPTOS_PREC_INTERNETCONTROL) :
                      iph->tos;

    if (ip_options_echo(&icmp_param.replyopts.opt.opt, skb_in))
        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);
    inet_sk(sk)->tos = tos;
    ipc.addr = iph->saddr;
    ipc.opt = &icmp_param.replyopts.opt;
    ipc.tx_flags = 0;

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

    if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code))
        goto ende;

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

    room = dst_mtu(&rt->dst);
    if (room > 576)
        room = 576;
    room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
    room -= sizeof(struct icmphdr);

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

    icmp_push_reply(&icmp_param, &fl4, &ipc, &rt);
ende:
    ip_rt_put(rt);
out_unlock:
    icmp_xmit_unlock(sk);
out:;
}
EXPORT_SYMBOL(icmp_send);


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))
        return;

    raw_icmp_error(skb, protocol, info);

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

/*
 *  Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH.
 */

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

    net = dev_net(skb_dst(skb)->dev);

    /*
     *  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. */
        goto out_err;

    if (icmph->type == 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:
            if (ipv4_config.no_pmtu_disc) {
                LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: fragmentation needed and DF set\n"),
                           &iph->daddr);
            } else {
                info = ntohs(icmph->un.frag.mtu);
                if (!info)
                    goto out;
            }
            break;
        case ICMP_SR_FAILED:
            LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: Source Route Failed\n"),
                       &iph->daddr);
            break;
        default:
            break;
        }
        if (icmph->code > NR_ICMP_UNREACH)
            goto out;
    } else if (icmph->type == ICMP_PARAMETERPROB)
        info = ntohl(icmph->un.gateway) >> 24;

    /*
     *  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 (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses &&
        inet_addr_type(net, 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;
out_err:
    ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
    goto out;
}


/*
 *  Handle ICMP_REDIRECT.
 */

static void icmp_redirect(struct sk_buff *skb)
{
    if (skb->len < sizeof(struct iphdr)) {
        ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS);
        return;
    }

    if (!pskb_may_pull(skb, sizeof(struct iphdr)))
        return;

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

/*
 *  Handle ICMP_ECHO ("ping") 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.
 *  See also WRT handling of options once they are done and working.
 */

static void icmp_echo(struct sk_buff *skb)
{
    struct net *net;

    net = dev_net(skb_dst(skb)->dev);
    if (!net->ipv4.sysctl_icmp_echo_ignore_all) {
        struct icmp_bxm icmp_param;

        icmp_param.data.icmph      = *icmp_hdr(skb);
        icmp_param.data.icmph.type = ICMP_ECHOREPLY;
        icmp_param.skb         = skb;
        icmp_param.offset      = 0;
        icmp_param.data_len    = skb->len;
        icmp_param.head_len    = sizeof(struct icmphdr);
        icmp_reply(&icmp_param, skb);
    }
}

/*
 *  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 void icmp_timestamp(struct sk_buff *skb)
{
    struct timespec tv;
    struct icmp_bxm icmp_param;
    /*
     *  Too short.
     */
    if (skb->len < 4)
        goto out_err;

    /*
     *  Fill in the current time as ms since midnight UT:
     */
    getnstimeofday(&tv);
    icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC +
                     tv.tv_nsec / NSEC_PER_MSEC);
    icmp_param.data.times[2] = icmp_param.data.times[1];
    if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4))
        BUG();
    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);
out:
    return;
out_err:
    ICMP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
    goto out;
}

static void icmp_discard(struct sk_buff *skb)
{
}

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

    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))
            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))
            goto drop;

        skb_set_network_header(skb, nh);
    }

    ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS);

    switch (skb->ip_summed) {
    case CHECKSUM_COMPLETE:
        if (!csum_fold(skb->csum))
            break;
        /* fall through */
    case CHECKSUM_NONE:
        skb->csum = 0;
        if (__skb_checksum_complete(skb))
            goto error;
    }

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

    icmph = icmp_hdr(skb);

    ICMPMSGIN_INC_STATS_BH(net, icmph->type);
    /*
     *  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)
        goto error;


    /*
     *  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) &&
            net->ipv4.sysctl_icmp_echo_ignore_broadcasts) {
            goto error;
        }
        if (icmph->type != ICMP_ECHO &&
            icmph->type != ICMP_TIMESTAMP &&
            icmph->type != ICMP_ADDRESS &&
            icmph->type != ICMP_ADDRESSREPLY) {
            goto error;
        }
    }

    icmp_pointers[icmph->type].handler(skb);

drop:
    kfree_skb(skb);
    return 0;
error:
    ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
    goto drop;
}

/*
 *  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 void __net_exit icmp_sk_exit(struct net *net)
{
    int i;

    for_each_possible_cpu(i)
        inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]);
    kfree(net->ipv4.icmp_sk);
    net->ipv4.icmp_sk = NULL;
}

static int __net_init icmp_sk_init(struct net *net)
{
    int i, err;

    net->ipv4.icmp_sk =
        kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL);
    if (net->ipv4.icmp_sk == NULL)
        return -ENOMEM;

    for_each_possible_cpu(i) {
        struct sock *sk;

        err = inet_ctl_sock_create(&sk, PF_INET,
                       SOCK_RAW, IPPROTO_ICMP, net);
        if (err < 0)
            goto fail;

        net->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;
    }

    /* Control parameters for ECHO replies. */
    net->ipv4.sysctl_icmp_echo_ignore_all = 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;

    return 0;

fail:
    for_each_possible_cpu(i)
        inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]);
    kfree(net->ipv4.icmp_sk);
    return err;
}

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

int __init icmp_init(void)
{
    return register_pernet_subsys(&icmp_sk_ops);
}