ping.c

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/*
 * INET     An implementation of the TCP/IP protocol suite for the LINUX
 *      operating system.  INET is implemented using the  BSD Socket
 *      interface as the means of communication with the user level.
 *
 *      "Ping" sockets
 *
 *      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.
 *
 * Based on ipv4/udp.c code.
 *
 * Authors: Vasiliy Kulikov / Openwall (for Linux 2.6),
 *      Pavel Kankovsky (for Linux 2.4.32)
 *
 * Pavel gave all rights to bugs to Vasiliy,
 * none of the bugs are Pavel's now.
 *
 */

#include <linux/uaccess.h>
#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <net/snmp.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include <net/icmp.h>
#include <net/protocol.h>
#include <linux/skbuff.h>
#include <linux/proc_fs.h>
#include <linux/export.h>
#include <net/sock.h>
#include <net/ping.h>
#include <net/udp.h>
#include <net/route.h>
#include <net/inet_common.h>
#include <net/checksum.h>


static struct ping_table ping_table;

static u16 ping_port_rover;

static inline int ping_hashfn(struct net *net, unsigned int num, unsigned int mask)
{
    int res = (num + net_hash_mix(net)) & mask;

    pr_debug("hash(%d) = %d\n", num, res);
    return res;
}

static inline struct hlist_nulls_head *ping_hashslot(struct ping_table *table,
                         struct net *net, unsigned int num)
{
    return &table->hash[ping_hashfn(net, num, PING_HTABLE_MASK)];
}

static int ping_v4_get_port(struct sock *sk, unsigned short ident)
{
    struct hlist_nulls_node *node;
    struct hlist_nulls_head *hlist;
    struct inet_sock *isk, *isk2;
    struct sock *sk2 = NULL;

    isk = inet_sk(sk);
    write_lock_bh(&ping_table.lock);
    if (ident == 0) {
        u32 i;
        u16 result = ping_port_rover + 1;

        for (i = 0; i < (1L << 16); i++, result++) {
            if (!result)
                result++; /* avoid zero */
            hlist = ping_hashslot(&ping_table, sock_net(sk),
                        result);
            ping_portaddr_for_each_entry(sk2, node, hlist) {
                isk2 = inet_sk(sk2);

                if (isk2->inet_num == result)
                    goto next_port;
            }

            /* found */
            ping_port_rover = ident = result;
            break;
next_port:
            ;
        }
        if (i >= (1L << 16))
            goto fail;
    } else {
        hlist = ping_hashslot(&ping_table, sock_net(sk), ident);
        ping_portaddr_for_each_entry(sk2, node, hlist) {
            isk2 = inet_sk(sk2);

            if ((isk2->inet_num == ident) &&
                (sk2 != sk) &&
                (!sk2->sk_reuse || !sk->sk_reuse))
                goto fail;
        }
    }

    pr_debug("found port/ident = %d\n", ident);
    isk->inet_num = ident;
    if (sk_unhashed(sk)) {
        pr_debug("was not hashed\n");
        sock_hold(sk);
        hlist_nulls_add_head(&sk->sk_nulls_node, hlist);
        sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
    }
    write_unlock_bh(&ping_table.lock);
    return 0;

fail:
    write_unlock_bh(&ping_table.lock);
    return 1;
}

static void ping_v4_hash(struct sock *sk)
{
    pr_debug("ping_v4_hash(sk->port=%u)\n", inet_sk(sk)->inet_num);
    BUG(); /* "Please do not press this button again." */
}

static void ping_v4_unhash(struct sock *sk)
{
    struct inet_sock *isk = inet_sk(sk);
    pr_debug("ping_v4_unhash(isk=%p,isk->num=%u)\n", isk, isk->inet_num);
    if (sk_hashed(sk)) {
        write_lock_bh(&ping_table.lock);
        hlist_nulls_del(&sk->sk_nulls_node);
        sock_put(sk);
        isk->inet_num = 0;
        isk->inet_sport = 0;
        sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
        write_unlock_bh(&ping_table.lock);
    }
}

static struct sock *ping_v4_lookup(struct net *net, __be32 saddr, __be32 daddr,
                   u16 ident, int dif)
{
    struct hlist_nulls_head *hslot = ping_hashslot(&ping_table, net, ident);
    struct sock *sk = NULL;
    struct inet_sock *isk;
    struct hlist_nulls_node *hnode;

    pr_debug("try to find: num = %d, daddr = %pI4, dif = %d\n",
         (int)ident, &daddr, dif);
    read_lock_bh(&ping_table.lock);

    ping_portaddr_for_each_entry(sk, hnode, hslot) {
        isk = inet_sk(sk);

        pr_debug("found: %p: num = %d, daddr = %pI4, dif = %d\n", sk,
             (int)isk->inet_num, &isk->inet_rcv_saddr,
             sk->sk_bound_dev_if);

        pr_debug("iterate\n");
        if (isk->inet_num != ident)
            continue;
        if (isk->inet_rcv_saddr && isk->inet_rcv_saddr != daddr)
            continue;
        if (sk->sk_bound_dev_if && sk->sk_bound_dev_if != dif)
            continue;

        sock_hold(sk);
        goto exit;
    }

    sk = NULL;
exit:
    read_unlock_bh(&ping_table.lock);

    return sk;
}

static void inet_get_ping_group_range_net(struct net *net, kgid_t *low,
                      kgid_t *high)
{
    kgid_t *data = net->ipv4.sysctl_ping_group_range;
    unsigned int seq;

    do {
        seq = read_seqbegin(&sysctl_local_ports.lock);

        *low = data[0];
        *high = data[1];
    } while (read_seqretry(&sysctl_local_ports.lock, seq));
}


static int ping_init_sock(struct sock *sk)
{
    struct net *net = sock_net(sk);
    kgid_t group = current_egid();
    struct group_info *group_info = get_current_groups();
    int i, j, count = group_info->ngroups;
    kgid_t low, high;

    inet_get_ping_group_range_net(net, &low, &high);
    if (gid_lte(low, group) && gid_lte(group, high))
        return 0;

    for (i = 0; i < group_info->nblocks; i++) {
        int cp_count = min_t(int, NGROUPS_PER_BLOCK, count);
        for (j = 0; j < cp_count; j++) {
            kgid_t gid = group_info->blocks[i][j];
            if (gid_lte(low, gid) && gid_lte(gid, high))
                return 0;
        }

        count -= cp_count;
    }

    return -EACCES;
}

static void ping_close(struct sock *sk, long timeout)
{
    pr_debug("ping_close(sk=%p,sk->num=%u)\n",
         inet_sk(sk), inet_sk(sk)->inet_num);
    pr_debug("isk->refcnt = %d\n", sk->sk_refcnt.counter);

    sk_common_release(sk);
}

/*
 * We need our own bind because there are no privileged id's == local ports.
 * Moreover, we don't allow binding to multi- and broadcast addresses.
 */

static int ping_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
{
    struct sockaddr_in *addr = (struct sockaddr_in *)uaddr;
    struct inet_sock *isk = inet_sk(sk);
    unsigned short snum;
    int chk_addr_ret;
    int err;

    if (addr_len < sizeof(struct sockaddr_in))
        return -EINVAL;

    pr_debug("ping_v4_bind(sk=%p,sa_addr=%08x,sa_port=%d)\n",
         sk, addr->sin_addr.s_addr, ntohs(addr->sin_port));

    chk_addr_ret = inet_addr_type(sock_net(sk), addr->sin_addr.s_addr);
    if (addr->sin_addr.s_addr == htonl(INADDR_ANY))
        chk_addr_ret = RTN_LOCAL;

    if ((sysctl_ip_nonlocal_bind == 0 &&
        isk->freebind == 0 && isk->transparent == 0 &&
         chk_addr_ret != RTN_LOCAL) ||
        chk_addr_ret == RTN_MULTICAST ||
        chk_addr_ret == RTN_BROADCAST)
        return -EADDRNOTAVAIL;

    lock_sock(sk);

    err = -EINVAL;
    if (isk->inet_num != 0)
        goto out;

    err = -EADDRINUSE;
    isk->inet_rcv_saddr = isk->inet_saddr = addr->sin_addr.s_addr;
    snum = ntohs(addr->sin_port);
    if (ping_v4_get_port(sk, snum) != 0) {
        isk->inet_saddr = isk->inet_rcv_saddr = 0;
        goto out;
    }

    pr_debug("after bind(): num = %d, daddr = %pI4, dif = %d\n",
         (int)isk->inet_num,
         &isk->inet_rcv_saddr,
         (int)sk->sk_bound_dev_if);

    err = 0;
    if (isk->inet_rcv_saddr)
        sk->sk_userlocks |= SOCK_BINDADDR_LOCK;
    if (snum)
        sk->sk_userlocks |= SOCK_BINDPORT_LOCK;
    isk->inet_sport = htons(isk->inet_num);
    isk->inet_daddr = 0;
    isk->inet_dport = 0;
    sk_dst_reset(sk);
out:
    release_sock(sk);
    pr_debug("ping_v4_bind -> %d\n", err);
    return err;
}

/*
 * Is this a supported type of ICMP message?
 */

static inline int ping_supported(int type, int code)
{
    if (type == ICMP_ECHO && code == 0)
        return 1;
    return 0;
}

/*
 * This routine is called by the ICMP module when it gets some
 * sort of error condition.
 */

static int ping_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);

void ping_err(struct sk_buff *skb, u32 info)
{
    struct iphdr *iph = (struct iphdr *)skb->data;
    struct icmphdr *icmph = (struct icmphdr *)(skb->data+(iph->ihl<<2));
    struct inet_sock *inet_sock;
    int type = icmph->type;
    int code = icmph->code;
    struct net *net = dev_net(skb->dev);
    struct sock *sk;
    int harderr;
    int err;

    /* We assume the packet has already been checked by icmp_unreach */

    if (!ping_supported(icmph->type, icmph->code))
        return;

    pr_debug("ping_err(type=%04x,code=%04x,id=%04x,seq=%04x)\n", type,
         code, ntohs(icmph->un.echo.id), ntohs(icmph->un.echo.sequence));

    sk = ping_v4_lookup(net, iph->daddr, iph->saddr,
                ntohs(icmph->un.echo.id), skb->dev->ifindex);
    if (sk == NULL) {
        pr_debug("no socket, dropping\n");
        return; /* No socket for error */
    }
    pr_debug("err on socket %p\n", sk);

    err = 0;
    harderr = 0;
    inet_sock = inet_sk(sk);

    switch (type) {
    default:
    case ICMP_TIME_EXCEEDED:
        err = EHOSTUNREACH;
        break;
    case ICMP_SOURCE_QUENCH:
        /* This is not a real error but ping wants to see it.
         * Report it with some fake errno. */
        err = EREMOTEIO;
        break;
    case ICMP_PARAMETERPROB:
        err = EPROTO;
        harderr = 1;
        break;
    case ICMP_DEST_UNREACH:
        if (code == ICMP_FRAG_NEEDED) { /* Path MTU discovery */
            ipv4_sk_update_pmtu(skb, sk, info);
            if (inet_sock->pmtudisc != IP_PMTUDISC_DONT) {
                err = EMSGSIZE;
                harderr = 1;
                break;
            }
            goto out;
        }
        err = EHOSTUNREACH;
        if (code <= NR_ICMP_UNREACH) {
            harderr = icmp_err_convert[code].fatal;
            err = icmp_err_convert[code].errno;
        }
        break;
    case ICMP_REDIRECT:
        /* See ICMP_SOURCE_QUENCH */
        ipv4_sk_redirect(skb, sk);
        err = EREMOTEIO;
        break;
    }

    /*
     *      RFC1122: OK.  Passes ICMP errors back to application, as per
     *  4.1.3.3.
     */
    if (!inet_sock->recverr) {
        if (!harderr || sk->sk_state != TCP_ESTABLISHED)
            goto out;
    } else {
        ip_icmp_error(sk, skb, err, 0 /* no remote port */,
             info, (u8 *)icmph);
    }
    sk->sk_err = err;
    sk->sk_error_report(sk);
out:
    sock_put(sk);
}

/*
 *  Copy and checksum an ICMP Echo packet from user space into a buffer.
 */

struct pingfakehdr {
    struct icmphdr icmph;
    struct iovec *iov;
    __wsum wcheck;
};

static int ping_getfrag(void *from, char *to,
            int offset, int fraglen, int odd, struct sk_buff *skb)
{
    struct pingfakehdr *pfh = (struct pingfakehdr *)from;

    if (offset == 0) {
        if (fraglen < sizeof(struct icmphdr))
            BUG();
        if (csum_partial_copy_fromiovecend(to + sizeof(struct icmphdr),
                pfh->iov, 0, fraglen - sizeof(struct icmphdr),
                &pfh->wcheck))
            return -EFAULT;

        return 0;
    }
    if (offset < sizeof(struct icmphdr))
        BUG();
    if (csum_partial_copy_fromiovecend
            (to, pfh->iov, offset - sizeof(struct icmphdr),
             fraglen, &pfh->wcheck))
        return -EFAULT;
    return 0;
}

static int ping_push_pending_frames(struct sock *sk, struct pingfakehdr *pfh,
                    struct flowi4 *fl4)
{
    struct sk_buff *skb = skb_peek(&sk->sk_write_queue);

    pfh->wcheck = csum_partial((char *)&pfh->icmph,
        sizeof(struct icmphdr), pfh->wcheck);
    pfh->icmph.checksum = csum_fold(pfh->wcheck);
    memcpy(icmp_hdr(skb), &pfh->icmph, sizeof(struct icmphdr));
    skb->ip_summed = CHECKSUM_NONE;
    return ip_push_pending_frames(sk, fl4);
}

static int ping_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
            size_t len)
{
    struct net *net = sock_net(sk);
    struct flowi4 fl4;
    struct inet_sock *inet = inet_sk(sk);
    struct ipcm_cookie ipc;
    struct icmphdr user_icmph;
    struct pingfakehdr pfh;
    struct rtable *rt = NULL;
    struct ip_options_data opt_copy;
    int free = 0;
    __be32 saddr, daddr, faddr;
    u8  tos;
    int err;

    pr_debug("ping_sendmsg(sk=%p,sk->num=%u)\n", inet, inet->inet_num);


    if (len > 0xFFFF)
        return -EMSGSIZE;

    /*
     *  Check the flags.
     */

    /* Mirror BSD error message compatibility */
    if (msg->msg_flags & MSG_OOB)
        return -EOPNOTSUPP;

    /*
     *  Fetch the ICMP header provided by the userland.
     *  iovec is modified!
     */

    if (memcpy_fromiovec((u8 *)&user_icmph, msg->msg_iov,
                 sizeof(struct icmphdr)))
        return -EFAULT;
    if (!ping_supported(user_icmph.type, user_icmph.code))
        return -EINVAL;

    /*
     *  Get and verify the address.
     */

    if (msg->msg_name) {
        struct sockaddr_in *usin = (struct sockaddr_in *)msg->msg_name;
        if (msg->msg_namelen < sizeof(*usin))
            return -EINVAL;
        if (usin->sin_family != AF_INET)
            return -EINVAL;
        daddr = usin->sin_addr.s_addr;
        /* no remote port */
    } else {
        if (sk->sk_state != TCP_ESTABLISHED)
            return -EDESTADDRREQ;
        daddr = inet->inet_daddr;
        /* no remote port */
    }

    ipc.addr = inet->inet_saddr;
    ipc.opt = NULL;
    ipc.oif = sk->sk_bound_dev_if;
    ipc.tx_flags = 0;
    err = sock_tx_timestamp(sk, &ipc.tx_flags);
    if (err)
        return err;

    if (msg->msg_controllen) {
        err = ip_cmsg_send(sock_net(sk), msg, &ipc);
        if (err)
            return err;
        if (ipc.opt)
            free = 1;
    }
    if (!ipc.opt) {
        struct ip_options_rcu *inet_opt;

        rcu_read_lock();
        inet_opt = rcu_dereference(inet->inet_opt);
        if (inet_opt) {
            memcpy(&opt_copy, inet_opt,
                   sizeof(*inet_opt) + inet_opt->opt.optlen);
            ipc.opt = &opt_copy.opt;
        }
        rcu_read_unlock();
    }

    saddr = ipc.addr;
    ipc.addr = faddr = daddr;

    if (ipc.opt && ipc.opt->opt.srr) {
        if (!daddr)
            return -EINVAL;
        faddr = ipc.opt->opt.faddr;
    }
    tos = RT_TOS(inet->tos);
    if (sock_flag(sk, SOCK_LOCALROUTE) ||
        (msg->msg_flags & MSG_DONTROUTE) ||
        (ipc.opt && ipc.opt->opt.is_strictroute)) {
        tos |= RTO_ONLINK;
    }

    if (ipv4_is_multicast(daddr)) {
        if (!ipc.oif)
            ipc.oif = inet->mc_index;
        if (!saddr)
            saddr = inet->mc_addr;
    } else if (!ipc.oif)
        ipc.oif = inet->uc_index;

    flowi4_init_output(&fl4, ipc.oif, sk->sk_mark, tos,
               RT_SCOPE_UNIVERSE, sk->sk_protocol,
               inet_sk_flowi_flags(sk), faddr, saddr, 0, 0);

    security_sk_classify_flow(sk, flowi4_to_flowi(&fl4));
    rt = ip_route_output_flow(net, &fl4, sk);
    if (IS_ERR(rt)) {
        err = PTR_ERR(rt);
        rt = NULL;
        if (err == -ENETUNREACH)
            IP_INC_STATS_BH(net, IPSTATS_MIB_OUTNOROUTES);
        goto out;
    }

    err = -EACCES;
    if ((rt->rt_flags & RTCF_BROADCAST) &&
        !sock_flag(sk, SOCK_BROADCAST))
        goto out;

    if (msg->msg_flags & MSG_CONFIRM)
        goto do_confirm;
back_from_confirm:

    if (!ipc.addr)
        ipc.addr = fl4.daddr;

    lock_sock(sk);

    pfh.icmph.type = user_icmph.type; /* already checked */
    pfh.icmph.code = user_icmph.code; /* ditto */
    pfh.icmph.checksum = 0;
    pfh.icmph.un.echo.id = inet->inet_sport;
    pfh.icmph.un.echo.sequence = user_icmph.un.echo.sequence;
    pfh.iov = msg->msg_iov;
    pfh.wcheck = 0;

    err = ip_append_data(sk, &fl4, ping_getfrag, &pfh, len,
            0, &ipc, &rt, msg->msg_flags);
    if (err)
        ip_flush_pending_frames(sk);
    else
        err = ping_push_pending_frames(sk, &pfh, &fl4);
    release_sock(sk);

out:
    ip_rt_put(rt);
    if (free)
        kfree(ipc.opt);
    if (!err) {
        icmp_out_count(sock_net(sk), user_icmph.type);
        return len;
    }
    return err;

do_confirm:
    dst_confirm(&rt->dst);
    if (!(msg->msg_flags & MSG_PROBE) || len)
        goto back_from_confirm;
    err = 0;
    goto out;
}

static int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
            size_t len, int noblock, int flags, int *addr_len)
{
    struct inet_sock *isk = inet_sk(sk);
    struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
    struct sk_buff *skb;
    int copied, err;

    pr_debug("ping_recvmsg(sk=%p,sk->num=%u)\n", isk, isk->inet_num);

    err = -EOPNOTSUPP;
    if (flags & MSG_OOB)
        goto out;

    if (addr_len)
        *addr_len = sizeof(*sin);

    if (flags & MSG_ERRQUEUE)
        return ip_recv_error(sk, msg, len);

    skb = skb_recv_datagram(sk, flags, noblock, &err);
    if (!skb)
        goto out;

    copied = skb->len;
    if (copied > len) {
        msg->msg_flags |= MSG_TRUNC;
        copied = len;
    }

    /* Don't bother checking the checksum */
    err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
    if (err)
        goto done;

    sock_recv_timestamp(msg, sk, skb);

    /* Copy the address. */
    if (sin) {
        sin->sin_family = AF_INET;
        sin->sin_port = 0 /* skb->h.uh->source */;
        sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
        memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
    }
    if (isk->cmsg_flags)
        ip_cmsg_recv(msg, skb);
    err = copied;

done:
    skb_free_datagram(sk, skb);
out:
    pr_debug("ping_recvmsg -> %d\n", err);
    return err;
}

static int ping_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
{
    pr_debug("ping_queue_rcv_skb(sk=%p,sk->num=%d,skb=%p)\n",
         inet_sk(sk), inet_sk(sk)->inet_num, skb);
    if (sock_queue_rcv_skb(sk, skb) < 0) {
        kfree_skb(skb);
        pr_debug("ping_queue_rcv_skb -> failed\n");
        return -1;
    }
    return 0;
}


/*
 *  All we need to do is get the socket.
 */

void ping_rcv(struct sk_buff *skb)
{
    struct sock *sk;
    struct net *net = dev_net(skb->dev);
    struct iphdr *iph = ip_hdr(skb);
    struct icmphdr *icmph = icmp_hdr(skb);
    __be32 saddr = iph->saddr;
    __be32 daddr = iph->daddr;

    /* We assume the packet has already been checked by icmp_rcv */

    pr_debug("ping_rcv(skb=%p,id=%04x,seq=%04x)\n",
         skb, ntohs(icmph->un.echo.id), ntohs(icmph->un.echo.sequence));

    /* Push ICMP header back */
    skb_push(skb, skb->data - (u8 *)icmph);

    sk = ping_v4_lookup(net, saddr, daddr, ntohs(icmph->un.echo.id),
                skb->dev->ifindex);
    if (sk != NULL) {
        pr_debug("rcv on socket %p\n", sk);
        ping_queue_rcv_skb(sk, skb_get(skb));
        sock_put(sk);
        return;
    }
    pr_debug("no socket, dropping\n");

    /* We're called from icmp_rcv(). kfree_skb() is done there. */
}

struct proto ping_prot = {
    .name =     "PING",
    .owner =    THIS_MODULE,
    .init =     ping_init_sock,
    .close =    ping_close,
    .connect =  ip4_datagram_connect,
    .disconnect =   udp_disconnect,
    .setsockopt =   ip_setsockopt,
    .getsockopt =   ip_getsockopt,
    .sendmsg =  ping_sendmsg,
    .recvmsg =  ping_recvmsg,
    .bind =     ping_bind,
    .backlog_rcv =  ping_queue_rcv_skb,
    .hash =     ping_v4_hash,
    .unhash =   ping_v4_unhash,
    .get_port = ping_v4_get_port,
    .obj_size = sizeof(struct inet_sock),
};
EXPORT_SYMBOL(ping_prot);

#ifdef CONFIG_PROC_FS

static struct sock *ping_get_first(struct seq_file *seq, int start)
{
    struct sock *sk;
    struct ping_iter_state *state = seq->private;
    struct net *net = seq_file_net(seq);

    for (state->bucket = start; state->bucket < PING_HTABLE_SIZE;
         ++state->bucket) {
        struct hlist_nulls_node *node;
        struct hlist_nulls_head *hslot;

        hslot = &ping_table.hash[state->bucket];

        if (hlist_nulls_empty(hslot))
            continue;

        sk_nulls_for_each(sk, node, hslot) {
            if (net_eq(sock_net(sk), net))
                goto found;
        }
    }
    sk = NULL;
found:
    return sk;
}

static struct sock *ping_get_next(struct seq_file *seq, struct sock *sk)
{
    struct ping_iter_state *state = seq->private;
    struct net *net = seq_file_net(seq);

    do {
        sk = sk_nulls_next(sk);
    } while (sk && (!net_eq(sock_net(sk), net)));

    if (!sk)
        return ping_get_first(seq, state->bucket + 1);
    return sk;
}

static struct sock *ping_get_idx(struct seq_file *seq, loff_t pos)
{
    struct sock *sk = ping_get_first(seq, 0);

    if (sk)
        while (pos && (sk = ping_get_next(seq, sk)) != NULL)
            --pos;
    return pos ? NULL : sk;
}

static void *ping_seq_start(struct seq_file *seq, loff_t *pos)
{
    struct ping_iter_state *state = seq->private;
    state->bucket = 0;

    read_lock_bh(&ping_table.lock);

    return *pos ? ping_get_idx(seq, *pos-1) : SEQ_START_TOKEN;
}

static void *ping_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
    struct sock *sk;

    if (v == SEQ_START_TOKEN)
        sk = ping_get_idx(seq, 0);
    else
        sk = ping_get_next(seq, v);

    ++*pos;
    return sk;
}

static void ping_seq_stop(struct seq_file *seq, void *v)
{
    read_unlock_bh(&ping_table.lock);
}

static void ping_format_sock(struct sock *sp, struct seq_file *f,
        int bucket, int *len)
{
    struct inet_sock *inet = inet_sk(sp);
    __be32 dest = inet->inet_daddr;
    __be32 src = inet->inet_rcv_saddr;
    __u16 destp = ntohs(inet->inet_dport);
    __u16 srcp = ntohs(inet->inet_sport);

    seq_printf(f, "%5d: %08X:%04X %08X:%04X"
        " %02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %pK %d%n",
        bucket, src, srcp, dest, destp, sp->sk_state,
        sk_wmem_alloc_get(sp),
        sk_rmem_alloc_get(sp),
        0, 0L, 0,
        from_kuid_munged(seq_user_ns(f), sock_i_uid(sp)),
        0, sock_i_ino(sp),
        atomic_read(&sp->sk_refcnt), sp,
        atomic_read(&sp->sk_drops), len);
}

static int ping_seq_show(struct seq_file *seq, void *v)
{
    if (v == SEQ_START_TOKEN)
        seq_printf(seq, "%-127s\n",
               "  sl  local_address rem_address   st tx_queue "
               "rx_queue tr tm->when retrnsmt   uid  timeout "
               "inode ref pointer drops");
    else {
        struct ping_iter_state *state = seq->private;
        int len;

        ping_format_sock(v, seq, state->bucket, &len);
        seq_printf(seq, "%*s\n", 127 - len, "");
    }
    return 0;
}

static const struct seq_operations ping_seq_ops = {
    .show       = ping_seq_show,
    .start      = ping_seq_start,
    .next       = ping_seq_next,
    .stop       = ping_seq_stop,
};

static int ping_seq_open(struct inode *inode, struct file *file)
{
    return seq_open_net(inode, file, &ping_seq_ops,
               sizeof(struct ping_iter_state));
}

static const struct file_operations ping_seq_fops = {
    .open       = ping_seq_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release_net,
};

static int ping_proc_register(struct net *net)
{
    struct proc_dir_entry *p;
    int rc = 0;

    p = proc_net_fops_create(net, "icmp", S_IRUGO, &ping_seq_fops);
    if (!p)
        rc = -ENOMEM;
    return rc;
}

static void ping_proc_unregister(struct net *net)
{
    proc_net_remove(net, "icmp");
}


static int __net_init ping_proc_init_net(struct net *net)
{
    return ping_proc_register(net);
}

static void __net_exit ping_proc_exit_net(struct net *net)
{
    ping_proc_unregister(net);
}

static struct pernet_operations ping_net_ops = {
    .init = ping_proc_init_net,
    .exit = ping_proc_exit_net,
};

int __init ping_proc_init(void)
{
    return register_pernet_subsys(&ping_net_ops);
}

void ping_proc_exit(void)
{
    unregister_pernet_subsys(&ping_net_ops);
}

#endif

void __init ping_init(void)
{
    int i;

    for (i = 0; i < PING_HTABLE_SIZE; i++)
        INIT_HLIST_NULLS_HEAD(&ping_table.hash[i], i);
    rwlock_init(&ping_table.lock);
}