ip_output.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.
 *
 *      The Internet Protocol (IP) output module.
 *
 * Authors: Ross Biro
 *      Fred N. van Kempen, <[email protected]>
 *      Donald Becker, <[email protected]>
 *      Alan Cox, <[email protected]>
 *      Richard Underwood
 *      Stefan Becker, <[email protected]>
 *      Jorge Cwik, <[email protected]>
 *      Arnt Gulbrandsen, <[email protected]>
 *      Hirokazu Takahashi, <[email protected]>
 *
 *  See ip_input.c for original log
 *
 *  Fixes:
 *      Alan Cox    :   Missing nonblock feature in ip_build_xmit.
 *      Mike Kilburn    :   htons() missing in ip_build_xmit.
 *      Bradford Johnson:   Fix faulty handling of some frames when
 *                  no route is found.
 *      Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
 *                  (in case if packet not accepted by
 *                  output firewall rules)
 *      Mike McLagan    :   Routing by source
 *      Alexey Kuznetsov:   use new route cache
 *      Andi Kleen:     Fix broken PMTU recovery and remove
 *                  some redundant tests.
 *  Vitaly E. Lavrov    :   Transparent proxy revived after year coma.
 *      Andi Kleen  :   Replace ip_reply with ip_send_reply.
 *      Andi Kleen  :   Split fast and slow ip_build_xmit path
 *                  for decreased register pressure on x86
 *                  and more readibility.
 *      Marc Boucher    :   When call_out_firewall returns FW_QUEUE,
 *                  silently drop skb instead of failing with -EPERM.
 *      Detlev Wengorz  :   Copy protocol for fragments.
 *      Hirokazu Takahashi: HW checksumming for outgoing UDP
 *                  datagrams.
 *      Hirokazu Takahashi: sendfile() on UDP works now.
 */

#include <asm/uaccess.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/highmem.h>
#include <linux/slab.h>

#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/init.h>

#include <net/snmp.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/route.h>
#include <net/xfrm.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/arp.h>
#include <net/icmp.h>
#include <net/checksum.h>
#include <net/inetpeer.h>
#include <linux/igmp.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_bridge.h>
#include <linux/mroute.h>
#include <linux/netlink.h>
#include <linux/tcp.h>

int sysctl_ip_default_ttl __read_mostly = IPDEFTTL;
EXPORT_SYMBOL(sysctl_ip_default_ttl);

/* Generate a checksum for an outgoing IP datagram. */
__inline__ void ip_send_check(struct iphdr *iph)
{
    iph->check = 0;
    iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
}
EXPORT_SYMBOL(ip_send_check);

int __ip_local_out(struct sk_buff *skb)
{
    struct iphdr *iph = ip_hdr(skb);

    iph->tot_len = htons(skb->len);
    ip_send_check(iph);
    return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT, skb, NULL,
               skb_dst(skb)->dev, dst_output);
}

int ip_local_out(struct sk_buff *skb)
{
    int err;

    err = __ip_local_out(skb);
    if (likely(err == 1))
        err = dst_output(skb);

    return err;
}
EXPORT_SYMBOL_GPL(ip_local_out);

static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
{
    int ttl = inet->uc_ttl;

    if (ttl < 0)
        ttl = ip4_dst_hoplimit(dst);
    return ttl;
}

/*
 *      Add an ip header to a skbuff and send it out.
 *
 */
int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
              __be32 saddr, __be32 daddr, struct ip_options_rcu *opt)
{
    struct inet_sock *inet = inet_sk(sk);
    struct rtable *rt = skb_rtable(skb);
    struct iphdr *iph;

    /* Build the IP header. */
    skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
    skb_reset_network_header(skb);
    iph = ip_hdr(skb);
    iph->version  = 4;
    iph->ihl      = 5;
    iph->tos      = inet->tos;
    if (ip_dont_fragment(sk, &rt->dst))
        iph->frag_off = htons(IP_DF);
    else
        iph->frag_off = 0;
    iph->ttl      = ip_select_ttl(inet, &rt->dst);
    iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
    iph->saddr    = saddr;
    iph->protocol = sk->sk_protocol;
    ip_select_ident(iph, &rt->dst, sk);

    if (opt && opt->opt.optlen) {
        iph->ihl += opt->opt.optlen>>2;
        ip_options_build(skb, &opt->opt, daddr, rt, 0);
    }

    skb->priority = sk->sk_priority;
    skb->mark = sk->sk_mark;

    /* Send it out. */
    return ip_local_out(skb);
}
EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);

static inline int ip_finish_output2(struct sk_buff *skb)
{
    struct dst_entry *dst = skb_dst(skb);
    struct rtable *rt = (struct rtable *)dst;
    struct net_device *dev = dst->dev;
    unsigned int hh_len = LL_RESERVED_SPACE(dev);
    struct neighbour *neigh;
    u32 nexthop;

    if (rt->rt_type == RTN_MULTICAST) {
        IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTMCAST, skb->len);
    } else if (rt->rt_type == RTN_BROADCAST)
        IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTBCAST, skb->len);

    /* Be paranoid, rather than too clever. */
    if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
        struct sk_buff *skb2;

        skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
        if (skb2 == NULL) {
            kfree_skb(skb);
            return -ENOMEM;
        }
        if (skb->sk)
            skb_set_owner_w(skb2, skb->sk);
        consume_skb(skb);
        skb = skb2;
    }

    rcu_read_lock_bh();
    nexthop = (__force u32) rt_nexthop(rt, ip_hdr(skb)->daddr);
    neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
    if (unlikely(!neigh))
        neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
    if (!IS_ERR(neigh)) {
        int res = dst_neigh_output(dst, neigh, skb);

        rcu_read_unlock_bh();
        return res;
    }
    rcu_read_unlock_bh();

    net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
                __func__);
    kfree_skb(skb);
    return -EINVAL;
}

static inline int ip_skb_dst_mtu(struct sk_buff *skb)
{
    struct inet_sock *inet = skb->sk ? inet_sk(skb->sk) : NULL;

    return (inet && inet->pmtudisc == IP_PMTUDISC_PROBE) ?
           skb_dst(skb)->dev->mtu : dst_mtu(skb_dst(skb));
}

static int ip_finish_output(struct sk_buff *skb)
{
#if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
    /* Policy lookup after SNAT yielded a new policy */
    if (skb_dst(skb)->xfrm != NULL) {
        IPCB(skb)->flags |= IPSKB_REROUTED;
        return dst_output(skb);
    }
#endif
    if (skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb))
        return ip_fragment(skb, ip_finish_output2);
    else
        return ip_finish_output2(skb);
}

int ip_mc_output(struct sk_buff *skb)
{
    struct sock *sk = skb->sk;
    struct rtable *rt = skb_rtable(skb);
    struct net_device *dev = rt->dst.dev;

    /*
     *  If the indicated interface is up and running, send the packet.
     */
    IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);

    skb->dev = dev;
    skb->protocol = htons(ETH_P_IP);

    /*
     *  Multicasts are looped back for other local users
     */

    if (rt->rt_flags&RTCF_MULTICAST) {
        if (sk_mc_loop(sk)
#ifdef CONFIG_IP_MROUTE
        /* Small optimization: do not loopback not local frames,
           which returned after forwarding; they will be  dropped
           by ip_mr_input in any case.
           Note, that local frames are looped back to be delivered
           to local recipients.

           This check is duplicated in ip_mr_input at the moment.
         */
            &&
            ((rt->rt_flags & RTCF_LOCAL) ||
             !(IPCB(skb)->flags & IPSKB_FORWARDED))
#endif
           ) {
            struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
            if (newskb)
                NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
                    newskb, NULL, newskb->dev,
                    dev_loopback_xmit);
        }

        /* Multicasts with ttl 0 must not go beyond the host */

        if (ip_hdr(skb)->ttl == 0) {
            kfree_skb(skb);
            return 0;
        }
    }

    if (rt->rt_flags&RTCF_BROADCAST) {
        struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
        if (newskb)
            NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, newskb,
                NULL, newskb->dev, dev_loopback_xmit);
    }

    return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, NULL,
                skb->dev, ip_finish_output,
                !(IPCB(skb)->flags & IPSKB_REROUTED));
}

int ip_output(struct sk_buff *skb)
{
    struct net_device *dev = skb_dst(skb)->dev;

    IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);

    skb->dev = dev;
    skb->protocol = htons(ETH_P_IP);

    return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, NULL, dev,
                ip_finish_output,
                !(IPCB(skb)->flags & IPSKB_REROUTED));
}

/*
 * copy saddr and daddr, possibly using 64bit load/stores
 * Equivalent to :
 *   iph->saddr = fl4->saddr;
 *   iph->daddr = fl4->daddr;
 */
static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
{
    BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
             offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
    memcpy(&iph->saddr, &fl4->saddr,
           sizeof(fl4->saddr) + sizeof(fl4->daddr));
}

int ip_queue_xmit(struct sk_buff *skb, struct flowi *fl)
{
    struct sock *sk = skb->sk;
    struct inet_sock *inet = inet_sk(sk);
    struct ip_options_rcu *inet_opt;
    struct flowi4 *fl4;
    struct rtable *rt;
    struct iphdr *iph;
    int res;

    /* Skip all of this if the packet is already routed,
     * f.e. by something like SCTP.
     */
    rcu_read_lock();
    inet_opt = rcu_dereference(inet->inet_opt);
    fl4 = &fl->u.ip4;
    rt = skb_rtable(skb);
    if (rt != NULL)
        goto packet_routed;

    /* Make sure we can route this packet. */
    rt = (struct rtable *)__sk_dst_check(sk, 0);
    if (rt == NULL) {
        __be32 daddr;

        /* Use correct destination address if we have options. */
        daddr = inet->inet_daddr;
        if (inet_opt && inet_opt->opt.srr)
            daddr = inet_opt->opt.faddr;

        /* If this fails, retransmit mechanism of transport layer will
         * keep trying until route appears or the connection times
         * itself out.
         */
        rt = ip_route_output_ports(sock_net(sk), fl4, sk,
                       daddr, inet->inet_saddr,
                       inet->inet_dport,
                       inet->inet_sport,
                       sk->sk_protocol,
                       RT_CONN_FLAGS(sk),
                       sk->sk_bound_dev_if);
        if (IS_ERR(rt))
            goto no_route;
        sk_setup_caps(sk, &rt->dst);
    }
    skb_dst_set_noref(skb, &rt->dst);

packet_routed:
    if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
        goto no_route;

    /* OK, we know where to send it, allocate and build IP header. */
    skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
    skb_reset_network_header(skb);
    iph = ip_hdr(skb);
    *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
    if (ip_dont_fragment(sk, &rt->dst) && !skb->local_df)
        iph->frag_off = htons(IP_DF);
    else
        iph->frag_off = 0;
    iph->ttl      = ip_select_ttl(inet, &rt->dst);
    iph->protocol = sk->sk_protocol;
    ip_copy_addrs(iph, fl4);

    /* Transport layer set skb->h.foo itself. */

    if (inet_opt && inet_opt->opt.optlen) {
        iph->ihl += inet_opt->opt.optlen >> 2;
        ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
    }

    ip_select_ident_more(iph, &rt->dst, sk,
                 (skb_shinfo(skb)->gso_segs ?: 1) - 1);

    skb->priority = sk->sk_priority;
    skb->mark = sk->sk_mark;

    res = ip_local_out(skb);
    rcu_read_unlock();
    return res;

no_route:
    rcu_read_unlock();
    IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
    kfree_skb(skb);
    return -EHOSTUNREACH;
}
EXPORT_SYMBOL(ip_queue_xmit);


static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
{
    to->pkt_type = from->pkt_type;
    to->priority = from->priority;
    to->protocol = from->protocol;
    skb_dst_drop(to);
    skb_dst_copy(to, from);
    to->dev = from->dev;
    to->mark = from->mark;

    /* Copy the flags to each fragment. */
    IPCB(to)->flags = IPCB(from)->flags;

#ifdef CONFIG_NET_SCHED
    to->tc_index = from->tc_index;
#endif
    nf_copy(to, from);
#if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
    defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
    to->nf_trace = from->nf_trace;
#endif
#if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
    to->ipvs_property = from->ipvs_property;
#endif
    skb_copy_secmark(to, from);
}

/*
 *  This IP datagram is too large to be sent in one piece.  Break it up into
 *  smaller pieces (each of size equal to IP header plus
 *  a block of the data of the original IP data part) that will yet fit in a
 *  single device frame, and queue such a frame for sending.
 */

int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
{
    struct iphdr *iph;
    int ptr;
    struct net_device *dev;
    struct sk_buff *skb2;
    unsigned int mtu, hlen, left, len, ll_rs;
    int offset;
    __be16 not_last_frag;
    struct rtable *rt = skb_rtable(skb);
    int err = 0;

    dev = rt->dst.dev;

    /*
     *  Point into the IP datagram header.
     */

    iph = ip_hdr(skb);

    if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->local_df) ||
             (IPCB(skb)->frag_max_size &&
              IPCB(skb)->frag_max_size > dst_mtu(&rt->dst)))) {
        IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
        icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
              htonl(ip_skb_dst_mtu(skb)));
        kfree_skb(skb);
        return -EMSGSIZE;
    }

    /*
     *  Setup starting values.
     */

    hlen = iph->ihl * 4;
    mtu = dst_mtu(&rt->dst) - hlen; /* Size of data space */
#ifdef CONFIG_BRIDGE_NETFILTER
    if (skb->nf_bridge)
        mtu -= nf_bridge_mtu_reduction(skb);
#endif
    IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;

    /* When frag_list is given, use it. First, check its validity:
     * some transformers could create wrong frag_list or break existing
     * one, it is not prohibited. In this case fall back to copying.
     *
     * LATER: this step can be merged to real generation of fragments,
     * we can switch to copy when see the first bad fragment.
     */
    if (skb_has_frag_list(skb)) {
        struct sk_buff *frag, *frag2;
        int first_len = skb_pagelen(skb);

        if (first_len - hlen > mtu ||
            ((first_len - hlen) & 7) ||
            ip_is_fragment(iph) ||
            skb_cloned(skb))
            goto slow_path;

        skb_walk_frags(skb, frag) {
            /* Correct geometry. */
            if (frag->len > mtu ||
                ((frag->len & 7) && frag->next) ||
                skb_headroom(frag) < hlen)
                goto slow_path_clean;

            /* Partially cloned skb? */
            if (skb_shared(frag))
                goto slow_path_clean;

            BUG_ON(frag->sk);
            if (skb->sk) {
                frag->sk = skb->sk;
                frag->destructor = sock_wfree;
            }
            skb->truesize -= frag->truesize;
        }

        /* Everything is OK. Generate! */

        err = 0;
        offset = 0;
        frag = skb_shinfo(skb)->frag_list;
        skb_frag_list_init(skb);
        skb->data_len = first_len - skb_headlen(skb);
        skb->len = first_len;
        iph->tot_len = htons(first_len);
        iph->frag_off = htons(IP_MF);
        ip_send_check(iph);

        for (;;) {
            /* Prepare header of the next frame,
             * before previous one went down. */
            if (frag) {
                frag->ip_summed = CHECKSUM_NONE;
                skb_reset_transport_header(frag);
                __skb_push(frag, hlen);
                skb_reset_network_header(frag);
                memcpy(skb_network_header(frag), iph, hlen);
                iph = ip_hdr(frag);
                iph->tot_len = htons(frag->len);
                ip_copy_metadata(frag, skb);
                if (offset == 0)
                    ip_options_fragment(frag);
                offset += skb->len - hlen;
                iph->frag_off = htons(offset>>3);
                if (frag->next != NULL)
                    iph->frag_off |= htons(IP_MF);
                /* Ready, complete checksum */
                ip_send_check(iph);
            }

            err = output(skb);

            if (!err)
                IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
            if (err || !frag)
                break;

            skb = frag;
            frag = skb->next;
            skb->next = NULL;
        }

        if (err == 0) {
            IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
            return 0;
        }

        while (frag) {
            skb = frag->next;
            kfree_skb(frag);
            frag = skb;
        }
        IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
        return err;

slow_path_clean:
        skb_walk_frags(skb, frag2) {
            if (frag2 == frag)
                break;
            frag2->sk = NULL;
            frag2->destructor = NULL;
            skb->truesize += frag2->truesize;
        }
    }

slow_path:
    left = skb->len - hlen;     /* Space per frame */
    ptr = hlen;     /* Where to start from */

    /* for bridged IP traffic encapsulated inside f.e. a vlan header,
     * we need to make room for the encapsulating header
     */
    ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, nf_bridge_pad(skb));

    /*
     *  Fragment the datagram.
     */

    offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
    not_last_frag = iph->frag_off & htons(IP_MF);

    /*
     *  Keep copying data until we run out.
     */

    while (left > 0) {
        len = left;
        /* IF: it doesn't fit, use 'mtu' - the data space left */
        if (len > mtu)
            len = mtu;
        /* IF: we are not sending up to and including the packet end
           then align the next start on an eight byte boundary */
        if (len < left) {
            len &= ~7;
        }
        /*
         *  Allocate buffer.
         */

        if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
            NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
            err = -ENOMEM;
            goto fail;
        }

        /*
         *  Set up data on packet
         */

        ip_copy_metadata(skb2, skb);
        skb_reserve(skb2, ll_rs);
        skb_put(skb2, len + hlen);
        skb_reset_network_header(skb2);
        skb2->transport_header = skb2->network_header + hlen;

        /*
         *  Charge the memory for the fragment to any owner
         *  it might possess
         */

        if (skb->sk)
            skb_set_owner_w(skb2, skb->sk);

        /*
         *  Copy the packet header into the new buffer.
         */

        skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);

        /*
         *  Copy a block of the IP datagram.
         */
        if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
            BUG();
        left -= len;

        /*
         *  Fill in the new header fields.
         */
        iph = ip_hdr(skb2);
        iph->frag_off = htons((offset >> 3));

        /* ANK: dirty, but effective trick. Upgrade options only if
         * the segment to be fragmented was THE FIRST (otherwise,
         * options are already fixed) and make it ONCE
         * on the initial skb, so that all the following fragments
         * will inherit fixed options.
         */
        if (offset == 0)
            ip_options_fragment(skb);

        /*
         *  Added AC : If we are fragmenting a fragment that's not the
         *         last fragment then keep MF on each bit
         */
        if (left > 0 || not_last_frag)
            iph->frag_off |= htons(IP_MF);
        ptr += len;
        offset += len;

        /*
         *  Put this fragment into the sending queue.
         */
        iph->tot_len = htons(len + hlen);

        ip_send_check(iph);

        err = output(skb2);
        if (err)
            goto fail;

        IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
    }
    consume_skb(skb);
    IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
    return err;

fail:
    kfree_skb(skb);
    IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
    return err;
}
EXPORT_SYMBOL(ip_fragment);

int
ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
{
    struct iovec *iov = from;

    if (skb->ip_summed == CHECKSUM_PARTIAL) {
        if (memcpy_fromiovecend(to, iov, offset, len) < 0)
            return -EFAULT;
    } else {
        __wsum csum = 0;
        if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
            return -EFAULT;
        skb->csum = csum_block_add(skb->csum, csum, odd);
    }
    return 0;
}
EXPORT_SYMBOL(ip_generic_getfrag);

static inline __wsum
csum_page(struct page *page, int offset, int copy)
{
    char *kaddr;
    __wsum csum;
    kaddr = kmap(page);
    csum = csum_partial(kaddr + offset, copy, 0);
    kunmap(page);
    return csum;
}

static inline int ip_ufo_append_data(struct sock *sk,
            struct sk_buff_head *queue,
            int getfrag(void *from, char *to, int offset, int len,
                   int odd, struct sk_buff *skb),
            void *from, int length, int hh_len, int fragheaderlen,
            int transhdrlen, int maxfraglen, unsigned int flags)
{
    struct sk_buff *skb;
    int err;

    /* There is support for UDP fragmentation offload by network
     * device, so create one single skb packet containing complete
     * udp datagram
     */
    if ((skb = skb_peek_tail(queue)) == NULL) {
        skb = sock_alloc_send_skb(sk,
            hh_len + fragheaderlen + transhdrlen + 20,
            (flags & MSG_DONTWAIT), &err);

        if (skb == NULL)
            return err;

        /* reserve space for Hardware header */
        skb_reserve(skb, hh_len);

        /* create space for UDP/IP header */
        skb_put(skb, fragheaderlen + transhdrlen);

        /* initialize network header pointer */
        skb_reset_network_header(skb);

        /* initialize protocol header pointer */
        skb->transport_header = skb->network_header + fragheaderlen;

        skb->ip_summed = CHECKSUM_PARTIAL;
        skb->csum = 0;

        /* specify the length of each IP datagram fragment */
        skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
        skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
        __skb_queue_tail(queue, skb);
    }

    return skb_append_datato_frags(sk, skb, getfrag, from,
                       (length - transhdrlen));
}

static int __ip_append_data(struct sock *sk,
                struct flowi4 *fl4,
                struct sk_buff_head *queue,
                struct inet_cork *cork,
                struct page_frag *pfrag,
                int getfrag(void *from, char *to, int offset,
                    int len, int odd, struct sk_buff *skb),
                void *from, int length, int transhdrlen,
                unsigned int flags)
{
    struct inet_sock *inet = inet_sk(sk);
    struct sk_buff *skb;

    struct ip_options *opt = cork->opt;
    int hh_len;
    int exthdrlen;
    int mtu;
    int copy;
    int err;
    int offset = 0;
    unsigned int maxfraglen, fragheaderlen;
    int csummode = CHECKSUM_NONE;
    struct rtable *rt = (struct rtable *)cork->dst;

    skb = skb_peek_tail(queue);

    exthdrlen = !skb ? rt->dst.header_len : 0;
    mtu = cork->fragsize;

    hh_len = LL_RESERVED_SPACE(rt->dst.dev);

    fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
    maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;

    if (cork->length + length > 0xFFFF - fragheaderlen) {
        ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
                   mtu-exthdrlen);
        return -EMSGSIZE;
    }

    /*
     * transhdrlen > 0 means that this is the first fragment and we wish
     * it won't be fragmented in the future.
     */
    if (transhdrlen &&
        length + fragheaderlen <= mtu &&
        rt->dst.dev->features & NETIF_F_V4_CSUM &&
        !exthdrlen)
        csummode = CHECKSUM_PARTIAL;

    cork->length += length;
    if (((length > mtu) || (skb && skb_is_gso(skb))) &&
        (sk->sk_protocol == IPPROTO_UDP) &&
        (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len) {
        err = ip_ufo_append_data(sk, queue, getfrag, from, length,
                     hh_len, fragheaderlen, transhdrlen,
                     maxfraglen, flags);
        if (err)
            goto error;
        return 0;
    }

    /* So, what's going on in the loop below?
     *
     * We use calculated fragment length to generate chained skb,
     * each of segments is IP fragment ready for sending to network after
     * adding appropriate IP header.
     */

    if (!skb)
        goto alloc_new_skb;

    while (length > 0) {
        /* Check if the remaining data fits into current packet. */
        copy = mtu - skb->len;
        if (copy < length)
            copy = maxfraglen - skb->len;
        if (copy <= 0) {
            char *data;
            unsigned int datalen;
            unsigned int fraglen;
            unsigned int fraggap;
            unsigned int alloclen;
            struct sk_buff *skb_prev;
alloc_new_skb:
            skb_prev = skb;
            if (skb_prev)
                fraggap = skb_prev->len - maxfraglen;
            else
                fraggap = 0;

            /*
             * If remaining data exceeds the mtu,
             * we know we need more fragment(s).
             */
            datalen = length + fraggap;
            if (datalen > mtu - fragheaderlen)
                datalen = maxfraglen - fragheaderlen;
            fraglen = datalen + fragheaderlen;

            if ((flags & MSG_MORE) &&
                !(rt->dst.dev->features&NETIF_F_SG))
                alloclen = mtu;
            else
                alloclen = fraglen;

            alloclen += exthdrlen;

            /* The last fragment gets additional space at tail.
             * Note, with MSG_MORE we overallocate on fragments,
             * because we have no idea what fragment will be
             * the last.
             */
            if (datalen == length + fraggap)
                alloclen += rt->dst.trailer_len;

            if (transhdrlen) {
                skb = sock_alloc_send_skb(sk,
                        alloclen + hh_len + 15,
                        (flags & MSG_DONTWAIT), &err);
            } else {
                skb = NULL;
                if (atomic_read(&sk->sk_wmem_alloc) <=
                    2 * sk->sk_sndbuf)
                    skb = sock_wmalloc(sk,
                               alloclen + hh_len + 15, 1,
                               sk->sk_allocation);
                if (unlikely(skb == NULL))
                    err = -ENOBUFS;
                else
                    /* only the initial fragment is
                       time stamped */
                    cork->tx_flags = 0;
            }
            if (skb == NULL)
                goto error;

            /*
             *  Fill in the control structures
             */
            skb->ip_summed = csummode;
            skb->csum = 0;
            skb_reserve(skb, hh_len);
            skb_shinfo(skb)->tx_flags = cork->tx_flags;

            /*
             *  Find where to start putting bytes.
             */
            data = skb_put(skb, fraglen + exthdrlen);
            skb_set_network_header(skb, exthdrlen);
            skb->transport_header = (skb->network_header +
                         fragheaderlen);
            data += fragheaderlen + exthdrlen;

            if (fraggap) {
                skb->csum = skb_copy_and_csum_bits(
                    skb_prev, maxfraglen,
                    data + transhdrlen, fraggap, 0);
                skb_prev->csum = csum_sub(skb_prev->csum,
                              skb->csum);
                data += fraggap;
                pskb_trim_unique(skb_prev, maxfraglen);
            }

            copy = datalen - transhdrlen - fraggap;
            if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
                err = -EFAULT;
                kfree_skb(skb);
                goto error;
            }

            offset += copy;
            length -= datalen - fraggap;
            transhdrlen = 0;
            exthdrlen = 0;
            csummode = CHECKSUM_NONE;

            /*
             * Put the packet on the pending queue.
             */
            __skb_queue_tail(queue, skb);
            continue;
        }

        if (copy > length)
            copy = length;

        if (!(rt->dst.dev->features&NETIF_F_SG)) {
            unsigned int off;

            off = skb->len;
            if (getfrag(from, skb_put(skb, copy),
                    offset, copy, off, skb) < 0) {
                __skb_trim(skb, off);
                err = -EFAULT;
                goto error;
            }
        } else {
            int i = skb_shinfo(skb)->nr_frags;

            err = -ENOMEM;
            if (!sk_page_frag_refill(sk, pfrag))
                goto error;

            if (!skb_can_coalesce(skb, i, pfrag->page,
                          pfrag->offset)) {
                err = -EMSGSIZE;
                if (i == MAX_SKB_FRAGS)
                    goto error;

                __skb_fill_page_desc(skb, i, pfrag->page,
                             pfrag->offset, 0);
                skb_shinfo(skb)->nr_frags = ++i;
                get_page(pfrag->page);
            }
            copy = min_t(int, copy, pfrag->size - pfrag->offset);
            if (getfrag(from,
                    page_address(pfrag->page) + pfrag->offset,
                    offset, copy, skb->len, skb) < 0)
                goto error_efault;

            pfrag->offset += copy;
            skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
            skb->len += copy;
            skb->data_len += copy;
            skb->truesize += copy;
            atomic_add(copy, &sk->sk_wmem_alloc);
        }
        offset += copy;
        length -= copy;
    }

    return 0;

error_efault:
    err = -EFAULT;
error:
    cork->length -= length;
    IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
    return err;
}

static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
             struct ipcm_cookie *ipc, struct rtable **rtp)
{
    struct inet_sock *inet = inet_sk(sk);
    struct ip_options_rcu *opt;
    struct rtable *rt;

    /*
     * setup for corking.
     */
    opt = ipc->opt;
    if (opt) {
        if (cork->opt == NULL) {
            cork->opt = kmalloc(sizeof(struct ip_options) + 40,
                        sk->sk_allocation);
            if (unlikely(cork->opt == NULL))
                return -ENOBUFS;
        }
        memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
        cork->flags |= IPCORK_OPT;
        cork->addr = ipc->addr;
    }
    rt = *rtp;
    if (unlikely(!rt))
        return -EFAULT;
    /*
     * We steal reference to this route, caller should not release it
     */
    *rtp = NULL;
    cork->fragsize = inet->pmtudisc == IP_PMTUDISC_PROBE ?
             rt->dst.dev->mtu : dst_mtu(&rt->dst);
    cork->dst = &rt->dst;
    cork->length = 0;
    cork->tx_flags = ipc->tx_flags;

    return 0;
}

/*
 *  ip_append_data() and ip_append_page() can make one large IP datagram
 *  from many pieces of data. Each pieces will be holded on the socket
 *  until ip_push_pending_frames() is called. Each piece can be a page
 *  or non-page data.
 *
 *  Not only UDP, other transport protocols - e.g. raw sockets - can use
 *  this interface potentially.
 *
 *  LATER: length must be adjusted by pad at tail, when it is required.
 */
int ip_append_data(struct sock *sk, struct flowi4 *fl4,
           int getfrag(void *from, char *to, int offset, int len,
                   int odd, struct sk_buff *skb),
           void *from, int length, int transhdrlen,
           struct ipcm_cookie *ipc, struct rtable **rtp,
           unsigned int flags)
{
    struct inet_sock *inet = inet_sk(sk);
    int err;

    if (flags&MSG_PROBE)
        return 0;

    if (skb_queue_empty(&sk->sk_write_queue)) {
        err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
        if (err)
            return err;
    } else {
        transhdrlen = 0;
    }

    return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
                sk_page_frag(sk), getfrag,
                from, length, transhdrlen, flags);
}

ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
               int offset, size_t size, int flags)
{
    struct inet_sock *inet = inet_sk(sk);
    struct sk_buff *skb;
    struct rtable *rt;
    struct ip_options *opt = NULL;
    struct inet_cork *cork;
    int hh_len;
    int mtu;
    int len;
    int err;
    unsigned int maxfraglen, fragheaderlen, fraggap;

    if (inet->hdrincl)
        return -EPERM;

    if (flags&MSG_PROBE)
        return 0;

    if (skb_queue_empty(&sk->sk_write_queue))
        return -EINVAL;

    cork = &inet->cork.base;
    rt = (struct rtable *)cork->dst;
    if (cork->flags & IPCORK_OPT)
        opt = cork->opt;

    if (!(rt->dst.dev->features&NETIF_F_SG))
        return -EOPNOTSUPP;

    hh_len = LL_RESERVED_SPACE(rt->dst.dev);
    mtu = cork->fragsize;

    fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
    maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;

    if (cork->length + size > 0xFFFF - fragheaderlen) {
        ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport, mtu);
        return -EMSGSIZE;
    }

    if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
        return -EINVAL;

    cork->length += size;
    if ((size + skb->len > mtu) &&
        (sk->sk_protocol == IPPROTO_UDP) &&
        (rt->dst.dev->features & NETIF_F_UFO)) {
        skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
        skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
    }


    while (size > 0) {
        int i;

        if (skb_is_gso(skb))
            len = size;
        else {

            /* Check if the remaining data fits into current packet. */
            len = mtu - skb->len;
            if (len < size)
                len = maxfraglen - skb->len;
        }
        if (len <= 0) {
            struct sk_buff *skb_prev;
            int alloclen;

            skb_prev = skb;
            fraggap = skb_prev->len - maxfraglen;

            alloclen = fragheaderlen + hh_len + fraggap + 15;
            skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
            if (unlikely(!skb)) {
                err = -ENOBUFS;
                goto error;
            }

            /*
             *  Fill in the control structures
             */
            skb->ip_summed = CHECKSUM_NONE;
            skb->csum = 0;
            skb_reserve(skb, hh_len);

            /*
             *  Find where to start putting bytes.
             */
            skb_put(skb, fragheaderlen + fraggap);
            skb_reset_network_header(skb);
            skb->transport_header = (skb->network_header +
                         fragheaderlen);
            if (fraggap) {
                skb->csum = skb_copy_and_csum_bits(skb_prev,
                                   maxfraglen,
                            skb_transport_header(skb),
                                   fraggap, 0);
                skb_prev->csum = csum_sub(skb_prev->csum,
                              skb->csum);
                pskb_trim_unique(skb_prev, maxfraglen);
            }

            /*
             * Put the packet on the pending queue.
             */
            __skb_queue_tail(&sk->sk_write_queue, skb);
            continue;
        }

        i = skb_shinfo(skb)->nr_frags;
        if (len > size)
            len = size;
        if (skb_can_coalesce(skb, i, page, offset)) {
            skb_frag_size_add(&skb_shinfo(skb)->frags[i-1], len);
        } else if (i < MAX_SKB_FRAGS) {
            get_page(page);
            skb_fill_page_desc(skb, i, page, offset, len);
        } else {
            err = -EMSGSIZE;
            goto error;
        }

        if (skb->ip_summed == CHECKSUM_NONE) {
            __wsum csum;
            csum = csum_page(page, offset, len);
            skb->csum = csum_block_add(skb->csum, csum, skb->len);
        }

        skb->len += len;
        skb->data_len += len;
        skb->truesize += len;
        atomic_add(len, &sk->sk_wmem_alloc);
        offset += len;
        size -= len;
    }
    return 0;

error:
    cork->length -= size;
    IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
    return err;
}

static void ip_cork_release(struct inet_cork *cork)
{
    cork->flags &= ~IPCORK_OPT;
    kfree(cork->opt);
    cork->opt = NULL;
    dst_release(cork->dst);
    cork->dst = NULL;
}

/*
 *  Combined all pending IP fragments on the socket as one IP datagram
 *  and push them out.
 */
struct sk_buff *__ip_make_skb(struct sock *sk,
                  struct flowi4 *fl4,
                  struct sk_buff_head *queue,
                  struct inet_cork *cork)
{
    struct sk_buff *skb, *tmp_skb;
    struct sk_buff **tail_skb;
    struct inet_sock *inet = inet_sk(sk);
    struct net *net = sock_net(sk);
    struct ip_options *opt = NULL;
    struct rtable *rt = (struct rtable *)cork->dst;
    struct iphdr *iph;
    __be16 df = 0;
    __u8 ttl;

    if ((skb = __skb_dequeue(queue)) == NULL)
        goto out;
    tail_skb = &(skb_shinfo(skb)->frag_list);

    /* move skb->data to ip header from ext header */
    if (skb->data < skb_network_header(skb))
        __skb_pull(skb, skb_network_offset(skb));
    while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
        __skb_pull(tmp_skb, skb_network_header_len(skb));
        *tail_skb = tmp_skb;
        tail_skb = &(tmp_skb->next);
        skb->len += tmp_skb->len;
        skb->data_len += tmp_skb->len;
        skb->truesize += tmp_skb->truesize;
        tmp_skb->destructor = NULL;
        tmp_skb->sk = NULL;
    }

    /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
     * to fragment the frame generated here. No matter, what transforms
     * how transforms change size of the packet, it will come out.
     */
    if (inet->pmtudisc < IP_PMTUDISC_DO)
        skb->local_df = 1;

    /* DF bit is set when we want to see DF on outgoing frames.
     * If local_df is set too, we still allow to fragment this frame
     * locally. */
    if (inet->pmtudisc >= IP_PMTUDISC_DO ||
        (skb->len <= dst_mtu(&rt->dst) &&
         ip_dont_fragment(sk, &rt->dst)))
        df = htons(IP_DF);

    if (cork->flags & IPCORK_OPT)
        opt = cork->opt;

    if (rt->rt_type == RTN_MULTICAST)
        ttl = inet->mc_ttl;
    else
        ttl = ip_select_ttl(inet, &rt->dst);

    iph = (struct iphdr *)skb->data;
    iph->version = 4;
    iph->ihl = 5;
    iph->tos = inet->tos;
    iph->frag_off = df;
    iph->ttl = ttl;
    iph->protocol = sk->sk_protocol;
    ip_copy_addrs(iph, fl4);
    ip_select_ident(iph, &rt->dst, sk);

    if (opt) {
        iph->ihl += opt->optlen>>2;
        ip_options_build(skb, opt, cork->addr, rt, 0);
    }

    skb->priority = sk->sk_priority;
    skb->mark = sk->sk_mark;
    /*
     * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
     * on dst refcount
     */
    cork->dst = NULL;
    skb_dst_set(skb, &rt->dst);

    if (iph->protocol == IPPROTO_ICMP)
        icmp_out_count(net, ((struct icmphdr *)
            skb_transport_header(skb))->type);

    ip_cork_release(cork);
out:
    return skb;
}

int ip_send_skb(struct net *net, struct sk_buff *skb)
{
    int err;

    err = ip_local_out(skb);
    if (err) {
        if (err > 0)
            err = net_xmit_errno(err);
        if (err)
            IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
    }

    return err;
}

int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
{
    struct sk_buff *skb;

    skb = ip_finish_skb(sk, fl4);
    if (!skb)
        return 0;

    /* Netfilter gets whole the not fragmented skb. */
    return ip_send_skb(sock_net(sk), skb);
}

/*
 *  Throw away all pending data on the socket.
 */
static void __ip_flush_pending_frames(struct sock *sk,
                      struct sk_buff_head *queue,
                      struct inet_cork *cork)
{
    struct sk_buff *skb;

    while ((skb = __skb_dequeue_tail(queue)) != NULL)
        kfree_skb(skb);

    ip_cork_release(cork);
}

void ip_flush_pending_frames(struct sock *sk)
{
    __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
}

struct sk_buff *ip_make_skb(struct sock *sk,
                struct flowi4 *fl4,
                int getfrag(void *from, char *to, int offset,
                    int len, int odd, struct sk_buff *skb),
                void *from, int length, int transhdrlen,
                struct ipcm_cookie *ipc, struct rtable **rtp,
                unsigned int flags)
{
    struct inet_cork cork;
    struct sk_buff_head queue;
    int err;

    if (flags & MSG_PROBE)
        return NULL;

    __skb_queue_head_init(&queue);

    cork.flags = 0;
    cork.addr = 0;
    cork.opt = NULL;
    err = ip_setup_cork(sk, &cork, ipc, rtp);
    if (err)
        return ERR_PTR(err);

    err = __ip_append_data(sk, fl4, &queue, &cork,
                   &current->task_frag, getfrag,
                   from, length, transhdrlen, flags);
    if (err) {
        __ip_flush_pending_frames(sk, &queue, &cork);
        return ERR_PTR(err);
    }

    return __ip_make_skb(sk, fl4, &queue, &cork);
}

/*
 *  Fetch data from kernel space and fill in checksum if needed.
 */
static int ip_reply_glue_bits(void *dptr, char *to, int offset,
                  int len, int odd, struct sk_buff *skb)
{
    __wsum csum;

    csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
    skb->csum = csum_block_add(skb->csum, csum, odd);
    return 0;
}

/*
 *  Generic function to send a packet as reply to another packet.
 *  Used to send some TCP resets/acks so far.
 *
 *  Use a fake percpu inet socket to avoid false sharing and contention.
 */
static DEFINE_PER_CPU(struct inet_sock, unicast_sock) = {
    .sk = {
        .__sk_common = {
            .skc_refcnt = ATOMIC_INIT(1),
        },
        .sk_wmem_alloc  = ATOMIC_INIT(1),
        .sk_allocation  = GFP_ATOMIC,
        .sk_flags   = (1UL << SOCK_USE_WRITE_QUEUE),
    },
    .pmtudisc   = IP_PMTUDISC_WANT,
    .uc_ttl     = -1,
};

void ip_send_unicast_reply(struct net *net, struct sk_buff *skb, __be32 daddr,
               __be32 saddr, const struct ip_reply_arg *arg,
               unsigned int len)
{
    struct ip_options_data replyopts;
    struct ipcm_cookie ipc;
    struct flowi4 fl4;
    struct rtable *rt = skb_rtable(skb);
    struct sk_buff *nskb;
    struct sock *sk;
    struct inet_sock *inet;

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

    ipc.addr = daddr;
    ipc.opt = NULL;
    ipc.tx_flags = 0;

    if (replyopts.opt.opt.optlen) {
        ipc.opt = &replyopts.opt;

        if (replyopts.opt.opt.srr)
            daddr = replyopts.opt.opt.faddr;
    }

    flowi4_init_output(&fl4, arg->bound_dev_if, 0,
               RT_TOS(arg->tos),
               RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
               ip_reply_arg_flowi_flags(arg),
               daddr, saddr,
               tcp_hdr(skb)->source, tcp_hdr(skb)->dest);
    security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
    rt = ip_route_output_key(net, &fl4);
    if (IS_ERR(rt))
        return;

    inet = &get_cpu_var(unicast_sock);

    inet->tos = arg->tos;
    sk = &inet->sk;
    sk->sk_priority = skb->priority;
    sk->sk_protocol = ip_hdr(skb)->protocol;
    sk->sk_bound_dev_if = arg->bound_dev_if;
    sock_net_set(sk, net);
    __skb_queue_head_init(&sk->sk_write_queue);
    sk->sk_sndbuf = sysctl_wmem_default;
    ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
               &ipc, &rt, MSG_DONTWAIT);
    nskb = skb_peek(&sk->sk_write_queue);
    if (nskb) {
        if (arg->csumoffset >= 0)
            *((__sum16 *)skb_transport_header(nskb) +
              arg->csumoffset) = csum_fold(csum_add(nskb->csum,
                                arg->csum));
        nskb->ip_summed = CHECKSUM_NONE;
        skb_orphan(nskb);
        skb_set_queue_mapping(nskb, skb_get_queue_mapping(skb));
        ip_push_pending_frames(sk, &fl4);
    }

    put_cpu_var(unicast_sock);

    ip_rt_put(rt);
}

void __init ip_init(void)
{
    ip_rt_init();
    inet_initpeers();

#if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
    igmp_mc_proc_init();
#endif
}