[UDP]: Introduce UDP encapsulation type for L2TP

[linux-2.6/openmoko-kernel/knife-kernel.git] / net / ipv4 / udp.c

/*
 * 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 User Datagram Protocol (UDP).
 *
 * Version:     $Id: udp.c,v 1.102 2002/02/01 22:01:04 davem Exp $
 *
 * Authors:     Ross Biro
 *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 *              Alan Cox, <Alan.Cox@linux.org>
 *              Hirokazu Takahashi, <taka@valinux.co.jp>
 *
 * Fixes:
 *              Alan Cox        :       verify_area() calls
 *              Alan Cox        :       stopped close while in use off icmp
 *                                      messages. Not a fix but a botch that
 *                                      for udp at least is 'valid'.
 *              Alan Cox        :       Fixed icmp handling properly
 *              Alan Cox        :       Correct error for oversized datagrams
 *              Alan Cox        :       Tidied select() semantics.
 *              Alan Cox        :       udp_err() fixed properly, also now
 *                                      select and read wake correctly on errors
 *              Alan Cox        :       udp_send verify_area moved to avoid mem leak
 *              Alan Cox        :       UDP can count its memory
 *              Alan Cox        :       send to an unknown connection causes
 *                                      an ECONNREFUSED off the icmp, but
 *                                      does NOT close.
 *              Alan Cox        :       Switched to new sk_buff handlers. No more backlog!
 *              Alan Cox        :       Using generic datagram code. Even smaller and the PEEK
 *                                      bug no longer crashes it.
 *              Fred Van Kempen :       Net2e support for sk->broadcast.
 *              Alan Cox        :       Uses skb_free_datagram
 *              Alan Cox        :       Added get/set sockopt support.
 *              Alan Cox        :       Broadcasting without option set returns EACCES.
 *              Alan Cox        :       No wakeup calls. Instead we now use the callbacks.
 *              Alan Cox        :       Use ip_tos and ip_ttl
 *              Alan Cox        :       SNMP Mibs
 *              Alan Cox        :       MSG_DONTROUTE, and 0.0.0.0 support.
 *              Matt Dillon     :       UDP length checks.
 *              Alan Cox        :       Smarter af_inet used properly.
 *              Alan Cox        :       Use new kernel side addressing.
 *              Alan Cox        :       Incorrect return on truncated datagram receive.
 *      Arnt Gulbrandsen        :       New udp_send and stuff
 *              Alan Cox        :       Cache last socket
 *              Alan Cox        :       Route cache
 *              Jon Peatfield   :       Minor efficiency fix to sendto().
 *              Mike Shaver     :       RFC1122 checks.
 *              Alan Cox        :       Nonblocking error fix.
 *      Willy Konynenberg       :       Transparent proxying support.
 *              Mike McLagan    :       Routing by source
 *              David S. Miller :       New socket lookup architecture.
 *                                      Last socket cache retained as it
 *                                      does have a high hit rate.
 *              Olaf Kirch      :       Don't linearise iovec on sendmsg.
 *              Andi Kleen      :       Some cleanups, cache destination entry
 *                                      for connect.
 *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
 *              Melvin Smith    :       Check msg_name not msg_namelen in sendto(),
 *                                      return ENOTCONN for unconnected sockets (POSIX)
 *              Janos Farkas    :       don't deliver multi/broadcasts to a different
 *                                      bound-to-device socket
 *      Hirokazu Takahashi      :       HW checksumming for outgoing UDP
 *                                      datagrams.
 *      Hirokazu Takahashi      :       sendfile() on UDP works now.
 *              Arnaldo C. Melo :       convert /proc/net/udp to seq_file
 *      YOSHIFUJI Hideaki @USAGI and:   Support IPV6_V6ONLY socket option, which
 *      Alexey Kuznetsov:               allow both IPv4 and IPv6 sockets to bind
 *                                      a single port at the same time.
 *      Derek Atkins <derek@ihtfp.com>: Add Encapulation Support
 *      James Chapman           :       Add L2TP encapsulation type.
 *
 *
 *              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.
 */

#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/ioctls.h>
#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/module.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/igmp.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/tcp_states.h>
#include <linux/skbuff.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <net/icmp.h>
#include <net/route.h>
#include <net/checksum.h>
#include <net/xfrm.h>
#include "udp_impl.h"

/*
 *      Snmp MIB for the UDP layer
 */

DEFINE_SNMP_STAT(struct udp_mib, udp_statistics) __read_mostly;

struct hlist_head udp_hash[UDP_HTABLE_SIZE];
DEFINE_RWLOCK(udp_hash_lock);

static int udp_port_rover;

static inline int __udp_lib_lport_inuse(__u16 num, struct hlist_head udptable[])
{
        struct sock *sk;
        struct hlist_node *node;

        sk_for_each(sk, node, &udptable[num & (UDP_HTABLE_SIZE - 1)])
                if (sk->sk_hash == num)
                        return 1;
        return 0;
}

/**
 *  __udp_lib_get_port  -  UDP/-Lite port lookup for IPv4 and IPv6
 *
 *  @sk:          socket struct in question
 *  @snum:        port number to look up
 *  @udptable:    hash list table, must be of UDP_HTABLE_SIZE
 *  @port_rover:  pointer to record of last unallocated port
 *  @saddr_comp:  AF-dependent comparison of bound local IP addresses
 */
int __udp_lib_get_port(struct sock *sk, unsigned short snum,
                       struct hlist_head udptable[], int *port_rover,
                       int (*saddr_comp)(const struct sock *sk1,
                                         const struct sock *sk2 )    )
{
        struct hlist_node *node;
        struct hlist_head *head;
        struct sock *sk2;
        int    error = 1;

        write_lock_bh(&udp_hash_lock);
        if (snum == 0) {
                int best_size_so_far, best, result, i;

                if (*port_rover > sysctl_local_port_range[1] ||
                    *port_rover < sysctl_local_port_range[0])
                        *port_rover = sysctl_local_port_range[0];
                best_size_so_far = 32767;
                best = result = *port_rover;
                for (i = 0; i < UDP_HTABLE_SIZE; i++, result++) {
                        int size;

                        head = &udptable[result & (UDP_HTABLE_SIZE - 1)];
                        if (hlist_empty(head)) {
                                if (result > sysctl_local_port_range[1])
                                        result = sysctl_local_port_range[0] +
                                                ((result - sysctl_local_port_range[0]) &
                                                 (UDP_HTABLE_SIZE - 1));
                                goto gotit;
                        }
                        size = 0;
                        sk_for_each(sk2, node, head) {
                                if (++size >= best_size_so_far)
                                        goto next;
                        }
                        best_size_so_far = size;
                        best = result;
                next:
                        ;
                }
                result = best;
                for (i = 0; i < (1 << 16) / UDP_HTABLE_SIZE;
                     i++, result += UDP_HTABLE_SIZE) {
                        if (result > sysctl_local_port_range[1])
                                result = sysctl_local_port_range[0]
                                        + ((result - sysctl_local_port_range[0]) &
                                           (UDP_HTABLE_SIZE - 1));
                        if (! __udp_lib_lport_inuse(result, udptable))
                                break;
                }
                if (i >= (1 << 16) / UDP_HTABLE_SIZE)
                        goto fail;
gotit:
                *port_rover = snum = result;
        } else {
                head = &udptable[snum & (UDP_HTABLE_SIZE - 1)];

                sk_for_each(sk2, node, head)
                        if (sk2->sk_hash == snum                             &&
                            sk2 != sk                                        &&
                            (!sk2->sk_reuse        || !sk->sk_reuse)         &&
                            (!sk2->sk_bound_dev_if || !sk->sk_bound_dev_if
                             || sk2->sk_bound_dev_if == sk->sk_bound_dev_if) &&
                            (*saddr_comp)(sk, sk2)                             )
                                goto fail;
        }
        inet_sk(sk)->num = snum;
        sk->sk_hash = snum;
        if (sk_unhashed(sk)) {
                head = &udptable[snum & (UDP_HTABLE_SIZE - 1)];
                sk_add_node(sk, head);
                sock_prot_inc_use(sk->sk_prot);
        }
        error = 0;
fail:
        write_unlock_bh(&udp_hash_lock);
        return error;
}

int udp_get_port(struct sock *sk, unsigned short snum,
                        int (*scmp)(const struct sock *, const struct sock *))
{
        return  __udp_lib_get_port(sk, snum, udp_hash, &udp_port_rover, scmp);
}

int ipv4_rcv_saddr_equal(const struct sock *sk1, const struct sock *sk2)
{
        struct inet_sock *inet1 = inet_sk(sk1), *inet2 = inet_sk(sk2);

        return  ( !ipv6_only_sock(sk2)  &&
                  (!inet1->rcv_saddr || !inet2->rcv_saddr ||
                   inet1->rcv_saddr == inet2->rcv_saddr      ));
}

static inline int udp_v4_get_port(struct sock *sk, unsigned short snum)
{
        return udp_get_port(sk, snum, ipv4_rcv_saddr_equal);
}

/* UDP is nearly always wildcards out the wazoo, it makes no sense to try
 * harder than this. -DaveM
 */
static struct sock *__udp4_lib_lookup(__be32 saddr, __be16 sport,
                                      __be32 daddr, __be16 dport,
                                      int dif, struct hlist_head udptable[])
{
        struct sock *sk, *result = NULL;
        struct hlist_node *node;
        unsigned short hnum = ntohs(dport);
        int badness = -1;

        read_lock(&udp_hash_lock);
        sk_for_each(sk, node, &udptable[hnum & (UDP_HTABLE_SIZE - 1)]) {
                struct inet_sock *inet = inet_sk(sk);

                if (sk->sk_hash == hnum && !ipv6_only_sock(sk)) {
                        int score = (sk->sk_family == PF_INET ? 1 : 0);
                        if (inet->rcv_saddr) {
                                if (inet->rcv_saddr != daddr)
                                        continue;
                                score+=2;
                        }
                        if (inet->daddr) {
                                if (inet->daddr != saddr)
                                        continue;
                                score+=2;
                        }
                        if (inet->dport) {
                                if (inet->dport != sport)
                                        continue;
                                score+=2;
                        }
                        if (sk->sk_bound_dev_if) {
                                if (sk->sk_bound_dev_if != dif)
                                        continue;
                                score+=2;
                        }
                        if (score == 9) {
                                result = sk;
                                break;
                        } else if (score > badness) {
                                result = sk;
                                badness = score;
                        }
                }
        }
        if (result)
                sock_hold(result);
        read_unlock(&udp_hash_lock);
        return result;
}

static inline struct sock *udp_v4_mcast_next(struct sock *sk,
                                             __be16 loc_port, __be32 loc_addr,
                                             __be16 rmt_port, __be32 rmt_addr,
                                             int dif)
{
        struct hlist_node *node;
        struct sock *s = sk;
        unsigned short hnum = ntohs(loc_port);

        sk_for_each_from(s, node) {
                struct inet_sock *inet = inet_sk(s);

                if (s->sk_hash != hnum                                  ||
                    (inet->daddr && inet->daddr != rmt_addr)            ||
                    (inet->dport != rmt_port && inet->dport)            ||
                    (inet->rcv_saddr && inet->rcv_saddr != loc_addr)    ||
                    ipv6_only_sock(s)                                   ||
                    (s->sk_bound_dev_if && s->sk_bound_dev_if != dif))
                        continue;
                if (!ip_mc_sf_allow(s, loc_addr, rmt_addr, dif))
                        continue;
                goto found;
        }
        s = NULL;
found:
        return s;
}

/*
 * This routine is called by the ICMP module when it gets some
 * sort of error condition.  If err < 0 then the socket should
 * be closed and the error returned to the user.  If err > 0
 * it's just the icmp type << 8 | icmp code.
 * Header points to the ip header of the error packet. We move
 * on past this. Then (as it used to claim before adjustment)
 * header points to the first 8 bytes of the udp header.  We need
 * to find the appropriate port.
 */

void __udp4_lib_err(struct sk_buff *skb, u32 info, struct hlist_head udptable[])
{
        struct inet_sock *inet;
        struct iphdr *iph = (struct iphdr*)skb->data;
        struct udphdr *uh = (struct udphdr*)(skb->data+(iph->ihl<<2));
        const int type = icmp_hdr(skb)->type;
        const int code = icmp_hdr(skb)->code;
        struct sock *sk;
        int harderr;
        int err;

        sk = __udp4_lib_lookup(iph->daddr, uh->dest, iph->saddr, uh->source,
                               skb->dev->ifindex, udptable                  );
        if (sk == NULL) {
                ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
                return; /* No socket for error */
        }

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

        switch (type) {
        default:
        case ICMP_TIME_EXCEEDED:
                err = EHOSTUNREACH;
                break;
        case ICMP_SOURCE_QUENCH:
                goto out;
        case ICMP_PARAMETERPROB:
                err = EPROTO;
                harderr = 1;
                break;
        case ICMP_DEST_UNREACH:
                if (code == ICMP_FRAG_NEEDED) { /* Path MTU discovery */
                        if (inet->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;
        }

        /*
         *      RFC1122: OK.  Passes ICMP errors back to application, as per
         *      4.1.3.3.
         */
        if (!inet->recverr) {
                if (!harderr || sk->sk_state != TCP_ESTABLISHED)
                        goto out;
        } else {
                ip_icmp_error(sk, skb, err, uh->dest, info, (u8*)(uh+1));
        }
        sk->sk_err = err;
        sk->sk_error_report(sk);
out:
        sock_put(sk);
}

void udp_err(struct sk_buff *skb, u32 info)
{
        return __udp4_lib_err(skb, info, udp_hash);
}

/*
 * Throw away all pending data and cancel the corking. Socket is locked.
 */
static void udp_flush_pending_frames(struct sock *sk)
{
        struct udp_sock *up = udp_sk(sk);

        if (up->pending) {
                up->len = 0;
                up->pending = 0;
                ip_flush_pending_frames(sk);
        }
}

/**
 *      udp4_hwcsum_outgoing  -  handle outgoing HW checksumming
 *      @sk:    socket we are sending on
 *      @skb:   sk_buff containing the filled-in UDP header
 *              (checksum field must be zeroed out)
 */
static void udp4_hwcsum_outgoing(struct sock *sk, struct sk_buff *skb,
                                 __be32 src, __be32 dst, int len      )
{
        unsigned int offset;
        struct udphdr *uh = udp_hdr(skb);
        __wsum csum = 0;

        if (skb_queue_len(&sk->sk_write_queue) == 1) {
                /*
                 * Only one fragment on the socket.
                 */
                skb->csum_start = skb_transport_header(skb) - skb->head;
                skb->csum_offset = offsetof(struct udphdr, check);
                uh->check = ~csum_tcpudp_magic(src, dst, len, IPPROTO_UDP, 0);
        } else {
                /*
                 * HW-checksum won't work as there are two or more
                 * fragments on the socket so that all csums of sk_buffs
                 * should be together
                 */
                offset = skb_transport_offset(skb);
                skb->csum = skb_checksum(skb, offset, skb->len - offset, 0);

                skb->ip_summed = CHECKSUM_NONE;

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

                uh->check = csum_tcpudp_magic(src, dst, len, IPPROTO_UDP, csum);
                if (uh->check == 0)
                        uh->check = CSUM_MANGLED_0;
        }
}

/*
 * Push out all pending data as one UDP datagram. Socket is locked.
 */
static int udp_push_pending_frames(struct sock *sk)
{
        struct udp_sock  *up = udp_sk(sk);
        struct inet_sock *inet = inet_sk(sk);
        struct flowi *fl = &inet->cork.fl;
        struct sk_buff *skb;
        struct udphdr *uh;
        int err = 0;
        __wsum csum = 0;

        /* Grab the skbuff where UDP header space exists. */
        if ((skb = skb_peek(&sk->sk_write_queue)) == NULL)
                goto out;

        /*
         * Create a UDP header
         */
        uh = udp_hdr(skb);
        uh->source = fl->fl_ip_sport;
        uh->dest = fl->fl_ip_dport;
        uh->len = htons(up->len);
        uh->check = 0;

        if (up->pcflag)                                  /*     UDP-Lite      */
                csum  = udplite_csum_outgoing(sk, skb);

        else if (sk->sk_no_check == UDP_CSUM_NOXMIT) {   /* UDP csum disabled */

                skb->ip_summed = CHECKSUM_NONE;
                goto send;

        } else if (skb->ip_summed == CHECKSUM_PARTIAL) { /* UDP hardware csum */

                udp4_hwcsum_outgoing(sk, skb, fl->fl4_src,fl->fl4_dst, up->len);
                goto send;

        } else                                           /*   `normal' UDP    */
                csum = udp_csum_outgoing(sk, skb);

        /* add protocol-dependent pseudo-header */
        uh->check = csum_tcpudp_magic(fl->fl4_src, fl->fl4_dst, up->len,
                                      sk->sk_protocol, csum             );
        if (uh->check == 0)
                uh->check = CSUM_MANGLED_0;

send:
        err = ip_push_pending_frames(sk);
out:
        up->len = 0;
        up->pending = 0;
        return err;
}

int udp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
                size_t len)
{
        struct inet_sock *inet = inet_sk(sk);
        struct udp_sock *up = udp_sk(sk);
        int ulen = len;
        struct ipcm_cookie ipc;
        struct rtable *rt = NULL;
        int free = 0;
        int connected = 0;
        __be32 daddr, faddr, saddr;
        __be16 dport;
        u8  tos;
        int err, is_udplite = up->pcflag;
        int corkreq = up->corkflag || msg->msg_flags&MSG_MORE;
        int (*getfrag)(void *, char *, int, int, int, struct sk_buff *);

        if (len > 0xFFFF)
                return -EMSGSIZE;

        /*
         *      Check the flags.
         */

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

        ipc.opt = NULL;

        if (up->pending) {
                /*
                 * There are pending frames.
                 * The socket lock must be held while it's corked.
                 */
                lock_sock(sk);
                if (likely(up->pending)) {
                        if (unlikely(up->pending != AF_INET)) {
                                release_sock(sk);
                                return -EINVAL;
                        }
                        goto do_append_data;
                }
                release_sock(sk);
        }
        ulen += sizeof(struct udphdr);

        /*
         *      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) {
                        if (usin->sin_family != AF_UNSPEC)
                                return -EAFNOSUPPORT;
                }

                daddr = usin->sin_addr.s_addr;
                dport = usin->sin_port;
                if (dport == 0)
                        return -EINVAL;
        } else {
                if (sk->sk_state != TCP_ESTABLISHED)
                        return -EDESTADDRREQ;
                daddr = inet->daddr;
                dport = inet->dport;
                /* Open fast path for connected socket.
                   Route will not be used, if at least one option is set.
                 */
                connected = 1;
        }
        ipc.addr = inet->saddr;

        ipc.oif = sk->sk_bound_dev_if;
        if (msg->msg_controllen) {
                err = ip_cmsg_send(msg, &ipc);
                if (err)
                        return err;
                if (ipc.opt)
                        free = 1;
                connected = 0;
        }
        if (!ipc.opt)
                ipc.opt = inet->opt;

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

        if (ipc.opt && ipc.opt->srr) {
                if (!daddr)
                        return -EINVAL;
                faddr = ipc.opt->faddr;
                connected = 0;
        }
        tos = RT_TOS(inet->tos);
        if (sock_flag(sk, SOCK_LOCALROUTE) ||
            (msg->msg_flags & MSG_DONTROUTE) ||
            (ipc.opt && ipc.opt->is_strictroute)) {
                tos |= RTO_ONLINK;
                connected = 0;
        }

        if (MULTICAST(daddr)) {
                if (!ipc.oif)
                        ipc.oif = inet->mc_index;
                if (!saddr)
                        saddr = inet->mc_addr;
                connected = 0;
        }

        if (connected)
                rt = (struct rtable*)sk_dst_check(sk, 0);

        if (rt == NULL) {
                struct flowi fl = { .oif = ipc.oif,
                                    .nl_u = { .ip4_u =
                                              { .daddr = faddr,
                                                .saddr = saddr,
                                                .tos = tos } },
                                    .proto = sk->sk_protocol,
                                    .uli_u = { .ports =
                                               { .sport = inet->sport,
                                                 .dport = dport } } };
                security_sk_classify_flow(sk, &fl);
                err = ip_route_output_flow(&rt, &fl, sk, 1);
                if (err) {
                        if (err == -ENETUNREACH)
                                IP_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
                        goto out;
                }

                err = -EACCES;
                if ((rt->rt_flags & RTCF_BROADCAST) &&
                    !sock_flag(sk, SOCK_BROADCAST))
                        goto out;
                if (connected)
                        sk_dst_set(sk, dst_clone(&rt->u.dst));
        }

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

        saddr = rt->rt_src;
        if (!ipc.addr)
                daddr = ipc.addr = rt->rt_dst;

        lock_sock(sk);
        if (unlikely(up->pending)) {
                /* The socket is already corked while preparing it. */
                /* ... which is an evident application bug. --ANK */
                release_sock(sk);

                LIMIT_NETDEBUG(KERN_DEBUG "udp cork app bug 2\n");
                err = -EINVAL;
                goto out;
        }
        /*
         *      Now cork the socket to pend data.
         */
        inet->cork.fl.fl4_dst = daddr;
        inet->cork.fl.fl_ip_dport = dport;
        inet->cork.fl.fl4_src = saddr;
        inet->cork.fl.fl_ip_sport = inet->sport;
        up->pending = AF_INET;

do_append_data:
        up->len += ulen;
        getfrag  =  is_udplite ?  udplite_getfrag : ip_generic_getfrag;
        err = ip_append_data(sk, getfrag, msg->msg_iov, ulen,
                        sizeof(struct udphdr), &ipc, rt,
                        corkreq ? msg->msg_flags|MSG_MORE : msg->msg_flags);
        if (err)
                udp_flush_pending_frames(sk);
        else if (!corkreq)
                err = udp_push_pending_frames(sk);
        else if (unlikely(skb_queue_empty(&sk->sk_write_queue)))
                up->pending = 0;
        release_sock(sk);

out:
        ip_rt_put(rt);
        if (free)
                kfree(ipc.opt);
        if (!err) {
                UDP_INC_STATS_USER(UDP_MIB_OUTDATAGRAMS, is_udplite);
                return len;
        }
        /*
         * ENOBUFS = no kernel mem, SOCK_NOSPACE = no sndbuf space.  Reporting
         * ENOBUFS might not be good (it's not tunable per se), but otherwise
         * we don't have a good statistic (IpOutDiscards but it can be too many
         * things).  We could add another new stat but at least for now that
         * seems like overkill.
         */
        if (err == -ENOBUFS || test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
                UDP_INC_STATS_USER(UDP_MIB_SNDBUFERRORS, is_udplite);
        }
        return err;

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

int udp_sendpage(struct sock *sk, struct page *page, int offset,
                 size_t size, int flags)
{
        struct udp_sock *up = udp_sk(sk);
        int ret;

        if (!up->pending) {
                struct msghdr msg = {   .msg_flags = flags|MSG_MORE };

                /* Call udp_sendmsg to specify destination address which
                 * sendpage interface can't pass.
                 * This will succeed only when the socket is connected.
                 */
                ret = udp_sendmsg(NULL, sk, &msg, 0);
                if (ret < 0)
                        return ret;
        }

        lock_sock(sk);

        if (unlikely(!up->pending)) {
                release_sock(sk);

                LIMIT_NETDEBUG(KERN_DEBUG "udp cork app bug 3\n");
                return -EINVAL;
        }

        ret = ip_append_page(sk, page, offset, size, flags);
        if (ret == -EOPNOTSUPP) {
                release_sock(sk);
                return sock_no_sendpage(sk->sk_socket, page, offset,
                                        size, flags);
        }
        if (ret < 0) {
                udp_flush_pending_frames(sk);
                goto out;
        }

        up->len += size;
        if (!(up->corkflag || (flags&MSG_MORE)))
                ret = udp_push_pending_frames(sk);
        if (!ret)
                ret = size;
out:
        release_sock(sk);
        return ret;
}

/*
 *      IOCTL requests applicable to the UDP protocol
 */

int udp_ioctl(struct sock *sk, int cmd, unsigned long arg)
{
        switch (cmd) {
        case SIOCOUTQ:
        {
                int amount = atomic_read(&sk->sk_wmem_alloc);
                return put_user(amount, (int __user *)arg);
        }

        case SIOCINQ:
        {
                struct sk_buff *skb;
                unsigned long amount;

                amount = 0;
                spin_lock_bh(&sk->sk_receive_queue.lock);
                skb = skb_peek(&sk->sk_receive_queue);
                if (skb != NULL) {
                        /*
                         * We will only return the amount
                         * of this packet since that is all
                         * that will be read.
                         */
                        amount = skb->len - sizeof(struct udphdr);
                }
                spin_unlock_bh(&sk->sk_receive_queue.lock);
                return put_user(amount, (int __user *)arg);
        }

        default:
                return -ENOIOCTLCMD;
        }

        return 0;
}

/*
 *      This should be easy, if there is something there we
 *      return it, otherwise we block.
 */

int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
                size_t len, int noblock, int flags, int *addr_len)
{
        struct inet_sock *inet = inet_sk(sk);
        struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
        struct sk_buff *skb;
        unsigned int ulen, copied;
        int err;
        int is_udplite = IS_UDPLITE(sk);

        /*
         *      Check any passed addresses
         */
        if (addr_len)
                *addr_len=sizeof(*sin);

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

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

        ulen = skb->len - sizeof(struct udphdr);
        copied = len;
        if (copied > ulen)
                copied = ulen;
        else if (copied < ulen)
                msg->msg_flags |= MSG_TRUNC;

        /*
         * If checksum is needed at all, try to do it while copying the
         * data.  If the data is truncated, or if we only want a partial
         * coverage checksum (UDP-Lite), do it before the copy.
         */

        if (copied < ulen || UDP_SKB_CB(skb)->partial_cov) {
                if (udp_lib_checksum_complete(skb))
                        goto csum_copy_err;
        }

        if (skb_csum_unnecessary(skb))
                err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr),
                                              msg->msg_iov, copied       );
        else {
                err = skb_copy_and_csum_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov);

                if (err == -EINVAL)
                        goto csum_copy_err;
        }

        if (err)
                goto out_free;

        sock_recv_timestamp(msg, sk, skb);

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

        err = copied;
        if (flags & MSG_TRUNC)
                err = ulen;

out_free:
        skb_free_datagram(sk, skb);
out:
        return err;

csum_copy_err:
        UDP_INC_STATS_BH(UDP_MIB_INERRORS, is_udplite);

        skb_kill_datagram(sk, skb, flags);

        if (noblock)
                return -EAGAIN;
        goto try_again;
}


int udp_disconnect(struct sock *sk, int flags)
{
        struct inet_sock *inet = inet_sk(sk);
        /*
         *      1003.1g - break association.
         */

        sk->sk_state = TCP_CLOSE;
        inet->daddr = 0;
        inet->dport = 0;
        sk->sk_bound_dev_if = 0;
        if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
                inet_reset_saddr(sk);

        if (!(sk->sk_userlocks & SOCK_BINDPORT_LOCK)) {
                sk->sk_prot->unhash(sk);
                inet->sport = 0;
        }
        sk_dst_reset(sk);
        return 0;
}

/* return:
 *      1  if the UDP system should process it
 *      0  if we should drop this packet
 *      -1 if it should get processed by xfrm4_rcv_encap
 *      -2 if it should get processed by l2tp
 */
static int udp_encap_rcv(struct sock * sk, struct sk_buff *skb)
{
        struct udp_sock *up = udp_sk(sk);
        struct udphdr *uh;
        struct iphdr *iph;
        int iphlen, len;

        __u8 *udpdata;
        __be32 *udpdata32;
        __u16 encap_type = up->encap_type;

        /* if we're overly short, let UDP handle it */
        len = skb->len - sizeof(struct udphdr);
        if (len <= 0)
                return 1;

        /* if this is not encapsulated socket, then just return now */
        if (!encap_type)
                return 1;

        /* If this is a paged skb, make sure we pull up
         * whatever data we need to look at. */
        if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
                return 1;

        /* Now we can get the pointers */
        uh = udp_hdr(skb);
        udpdata = (__u8 *)uh + sizeof(struct udphdr);
        udpdata32 = (__be32 *)udpdata;

        switch (encap_type) {
        default:
        case UDP_ENCAP_ESPINUDP:
                /* Check if this is a keepalive packet.  If so, eat it. */
                if (len == 1 && udpdata[0] == 0xff) {
                        return 0;
                } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
                        /* ESP Packet without Non-ESP header */
                        len = sizeof(struct udphdr);
                } else
                        /* Must be an IKE packet.. pass it through */
                        return 1;
                break;
        case UDP_ENCAP_ESPINUDP_NON_IKE:
                /* Check if this is a keepalive packet.  If so, eat it. */
                if (len == 1 && udpdata[0] == 0xff) {
                        return 0;
                } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
                           udpdata32[0] == 0 && udpdata32[1] == 0) {

                        /* ESP Packet with Non-IKE marker */
                        len = sizeof(struct udphdr) + 2 * sizeof(u32);
                } else
                        /* Must be an IKE packet.. pass it through */
                        return 1;
                break;
        case UDP_ENCAP_L2TPINUDP:
                /* Let caller know to send this to l2tp */
                return -2;
        }

#ifndef CONFIG_XFRM
        return 1;
#else
        /* At this point we are sure that this is an ESPinUDP packet,
         * so we need to remove 'len' bytes from the packet (the UDP
         * header and optional ESP marker bytes) and then modify the
         * protocol to ESP, and then call into the transform receiver.
         */
        if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
                return 0;

        /* Now we can update and verify the packet length... */
        iph = ip_hdr(skb);
        iphlen = iph->ihl << 2;
        iph->tot_len = htons(ntohs(iph->tot_len) - len);
        if (skb->len < iphlen + len) {
                /* packet is too small!?! */
                return 0;
        }

        /* pull the data buffer up to the ESP header and set the
         * transport header to point to ESP.  Keep UDP on the stack
         * for later.
         */
        __skb_pull(skb, len);
        skb_reset_transport_header(skb);

        /* modify the protocol (it's ESP!) */
        iph->protocol = IPPROTO_ESP;

        /* and let the caller know to send this into the ESP processor... */
        return -1;
#endif
}

/* returns:
 *  -1: error
 *   0: success
 *  >0: "udp encap" protocol resubmission
 *
 * Note that in the success and error cases, the skb is assumed to
 * have either been requeued or freed.
 */
int udp_queue_rcv_skb(struct sock * sk, struct sk_buff *skb)
{
        struct udp_sock *up = udp_sk(sk);
        int rc;

        /*
         *      Charge it to the socket, dropping if the queue is full.
         */
        if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
                goto drop;
        nf_reset(skb);

        if (up->encap_type) {
                /*
                 * This is an encapsulation socket, so let's see if this is
                 * an encapsulated packet.
                 * If it's a keepalive packet, then just eat it.
                 * If it's an encapsulateed packet, then pass it to the
                 * IPsec xfrm input and return the response
                 * appropriately.  Otherwise, just fall through and
                 * pass this up the UDP socket.
                 */
                int ret;

                ret = udp_encap_rcv(sk, skb);
                if (ret == 0) {
                        /* Eat the packet .. */
                        kfree_skb(skb);
                        return 0;
                }
                if (ret == -1) {
                        /* process the ESP packet */
                        ret = xfrm4_rcv_encap(skb, up->encap_type);
                        UDP_INC_STATS_BH(UDP_MIB_INDATAGRAMS, up->pcflag);
                        return -ret;
                }
                if (ret == -2) {
                        /* process the L2TP packet */
                        if (up->encap_rcv != NULL) {
                                ret = (*up->encap_rcv)(sk, skb);
                                if (ret <= 0) {
                                        UDP_INC_STATS_BH(UDP_MIB_INDATAGRAMS, up->pcflag);
                                        return ret;
                                }

                                /* FALLTHROUGH -- pass up as UDP packet */
                        }
                }

                /* FALLTHROUGH -- it's a UDP Packet */
        }

        /*
         *      UDP-Lite specific tests, ignored on UDP sockets
         */
        if ((up->pcflag & UDPLITE_RECV_CC)  &&  UDP_SKB_CB(skb)->partial_cov) {

                /*
                 * MIB statistics other than incrementing the error count are
                 * disabled for the following two types of errors: these depend
                 * on the application settings, not on the functioning of the
                 * protocol stack as such.
                 *
                 * RFC 3828 here recommends (sec 3.3): "There should also be a
                 * way ... to ... at least let the receiving application block
                 * delivery of packets with coverage values less than a value
                 * provided by the application."
                 */
                if (up->pcrlen == 0) {          /* full coverage was set  */
                        LIMIT_NETDEBUG(KERN_WARNING "UDPLITE: partial coverage "
                                "%d while full coverage %d requested\n",
                                UDP_SKB_CB(skb)->cscov, skb->len);
                        goto drop;
                }
                /* The next case involves violating the min. coverage requested
                 * by the receiver. This is subtle: if receiver wants x and x is
                 * greater than the buffersize/MTU then receiver will complain
                 * that it wants x while sender emits packets of smaller size y.
                 * Therefore the above ...()->partial_cov statement is essential.
                 */
                if (UDP_SKB_CB(skb)->cscov  <  up->pcrlen) {
                        LIMIT_NETDEBUG(KERN_WARNING
                                "UDPLITE: coverage %d too small, need min %d\n",
                                UDP_SKB_CB(skb)->cscov, up->pcrlen);
                        goto drop;
                }
        }

        if (sk->sk_filter) {
                if (udp_lib_checksum_complete(skb))
                        goto drop;
        }

        if ((rc = sock_queue_rcv_skb(sk,skb)) < 0) {
                /* Note that an ENOMEM error is charged twice */
                if (rc == -ENOMEM)
                        UDP_INC_STATS_BH(UDP_MIB_RCVBUFERRORS, up->pcflag);
                goto drop;
        }

        UDP_INC_STATS_BH(UDP_MIB_INDATAGRAMS, up->pcflag);
        return 0;

drop:
        UDP_INC_STATS_BH(UDP_MIB_INERRORS, up->pcflag);
        kfree_skb(skb);
        return -1;
}

/*
 *      Multicasts and broadcasts go to each listener.
 *
 *      Note: called only from the BH handler context,
 *      so we don't need to lock the hashes.
 */
static int __udp4_lib_mcast_deliver(struct sk_buff *skb,
                                    struct udphdr  *uh,
                                    __be32 saddr, __be32 daddr,
                                    struct hlist_head udptable[])
{
        struct sock *sk;
        int dif;

        read_lock(&udp_hash_lock);
        sk = sk_head(&udptable[ntohs(uh->dest) & (UDP_HTABLE_SIZE - 1)]);
        dif = skb->dev->ifindex;
        sk = udp_v4_mcast_next(sk, uh->dest, daddr, uh->source, saddr, dif);
        if (sk) {
                struct sock *sknext = NULL;

                do {
                        struct sk_buff *skb1 = skb;

                        sknext = udp_v4_mcast_next(sk_next(sk), uh->dest, daddr,
                                                   uh->source, saddr, dif);
                        if (sknext)
                                skb1 = skb_clone(skb, GFP_ATOMIC);

                        if (skb1) {
                                int ret = udp_queue_rcv_skb(sk, skb1);
                                if (ret > 0)
                                        /* we should probably re-process instead
                                         * of dropping packets here. */
                                        kfree_skb(skb1);
                        }
                        sk = sknext;
                } while (sknext);
        } else
                kfree_skb(skb);
        read_unlock(&udp_hash_lock);
        return 0;
}

/* Initialize UDP checksum. If exited with zero value (success),
 * CHECKSUM_UNNECESSARY means, that no more checks are required.
 * Otherwise, csum completion requires chacksumming packet body,
 * including udp header and folding it to skb->csum.
 */
static inline int udp4_csum_init(struct sk_buff *skb, struct udphdr *uh,
                                 int proto)
{
        const struct iphdr *iph;
        int err;

        UDP_SKB_CB(skb)->partial_cov = 0;
        UDP_SKB_CB(skb)->cscov = skb->len;

        if (proto == IPPROTO_UDPLITE) {
                err = udplite_checksum_init(skb, uh);
                if (err)
                        return err;
        }

        iph = ip_hdr(skb);
        if (uh->check == 0) {
                skb->ip_summed = CHECKSUM_UNNECESSARY;
        } else if (skb->ip_summed == CHECKSUM_COMPLETE) {
               if (!csum_tcpudp_magic(iph->saddr, iph->daddr, skb->len,
                                      proto, skb->csum))
                        skb->ip_summed = CHECKSUM_UNNECESSARY;
        }
        if (!skb_csum_unnecessary(skb))
                skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
                                               skb->len, proto, 0);
        /* Probably, we should checksum udp header (it should be in cache
         * in any case) and data in tiny packets (< rx copybreak).
         */

        return 0;
}

/*
 *      All we need to do is get the socket, and then do a checksum.
 */

int __udp4_lib_rcv(struct sk_buff *skb, struct hlist_head udptable[],
                   int proto)
{
        struct sock *sk;
        struct udphdr *uh = udp_hdr(skb);
        unsigned short ulen;
        struct rtable *rt = (struct rtable*)skb->dst;
        __be32 saddr = ip_hdr(skb)->saddr;
        __be32 daddr = ip_hdr(skb)->daddr;

        /*
         *  Validate the packet.
         */
        if (!pskb_may_pull(skb, sizeof(struct udphdr)))
                goto drop;              /* No space for header. */

        ulen = ntohs(uh->len);
        if (ulen > skb->len)
                goto short_packet;

        if (proto == IPPROTO_UDP) {
                /* UDP validates ulen. */
                if (ulen < sizeof(*uh) || pskb_trim_rcsum(skb, ulen))
                        goto short_packet;
                uh = udp_hdr(skb);
        }

        if (udp4_csum_init(skb, uh, proto))
                goto csum_error;

        if (rt->rt_flags & (RTCF_BROADCAST|RTCF_MULTICAST))
                return __udp4_lib_mcast_deliver(skb, uh, saddr, daddr, udptable);

        sk = __udp4_lib_lookup(saddr, uh->source, daddr, uh->dest,
                               skb->dev->ifindex, udptable        );

        if (sk != NULL) {
                int ret = udp_queue_rcv_skb(sk, skb);
                sock_put(sk);

                /* a return value > 0 means to resubmit the input, but
                 * it wants the return to be -protocol, or 0
                 */
                if (ret > 0)
                        return -ret;
                return 0;
        }

        if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
                goto drop;
        nf_reset(skb);

        /* No socket. Drop packet silently, if checksum is wrong */
        if (udp_lib_checksum_complete(skb))
                goto csum_error;

        UDP_INC_STATS_BH(UDP_MIB_NOPORTS, proto == IPPROTO_UDPLITE);
        icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);

        /*
         * Hmm.  We got an UDP packet to a port to which we
         * don't wanna listen.  Ignore it.
         */
        kfree_skb(skb);
        return 0;

short_packet:
        LIMIT_NETDEBUG(KERN_DEBUG "UDP%s: short packet: From %u.%u.%u.%u:%u %d/%d to %u.%u.%u.%u:%u\n",
                       proto == IPPROTO_UDPLITE ? "-Lite" : "",
                       NIPQUAD(saddr),
                       ntohs(uh->source),
                       ulen,
                       skb->len,
                       NIPQUAD(daddr),
                       ntohs(uh->dest));
        goto drop;

csum_error:
        /*
         * RFC1122: OK.  Discards the bad packet silently (as far as
         * the network is concerned, anyway) as per 4.1.3.4 (MUST).
         */
        LIMIT_NETDEBUG(KERN_DEBUG "UDP%s: bad checksum. From %d.%d.%d.%d:%d to %d.%d.%d.%d:%d ulen %d\n",
                       proto == IPPROTO_UDPLITE ? "-Lite" : "",
                       NIPQUAD(saddr),
                       ntohs(uh->source),
                       NIPQUAD(daddr),
                       ntohs(uh->dest),
                       ulen);
drop:
        UDP_INC_STATS_BH(UDP_MIB_INERRORS, proto == IPPROTO_UDPLITE);
        kfree_skb(skb);
        return 0;
}

int udp_rcv(struct sk_buff *skb)
{
        return __udp4_lib_rcv(skb, udp_hash, IPPROTO_UDP);
}

int udp_destroy_sock(struct sock *sk)
{
        lock_sock(sk);
        udp_flush_pending_frames(sk);
        release_sock(sk);
        return 0;
}

/*
 *      Socket option code for UDP
 */
int udp_lib_setsockopt(struct sock *sk, int level, int optname,
                       char __user *optval, int optlen,
                       int (*push_pending_frames)(struct sock *))
{
        struct udp_sock *up = udp_sk(sk);
        int val;
        int err = 0;

        if (optlen<sizeof(int))
                return -EINVAL;

        if (get_user(val, (int __user *)optval))
                return -EFAULT;

        switch (optname) {
        case UDP_CORK:
                if (val != 0) {
                        up->corkflag = 1;
                } else {
                        up->corkflag = 0;
                        lock_sock(sk);
                        (*push_pending_frames)(sk);
                        release_sock(sk);
                }
                break;

        case UDP_ENCAP:
                switch (val) {
                case 0:
                case UDP_ENCAP_ESPINUDP:
                case UDP_ENCAP_ESPINUDP_NON_IKE:
                case UDP_ENCAP_L2TPINUDP:
                        up->encap_type = val;
                        break;
                default:
                        err = -ENOPROTOOPT;
                        break;
                }
                break;

        /*
         *      UDP-Lite's partial checksum coverage (RFC 3828).
         */
        /* The sender sets actual checksum coverage length via this option.
         * The case coverage > packet length is handled by send module. */
        case UDPLITE_SEND_CSCOV:
                if (!up->pcflag)         /* Disable the option on UDP sockets */
                        return -ENOPROTOOPT;
                if (val != 0 && val < 8) /* Illegal coverage: use default (8) */
                        val = 8;
                up->pcslen = val;
                up->pcflag |= UDPLITE_SEND_CC;
                break;

        /* The receiver specifies a minimum checksum coverage value. To make
         * sense, this should be set to at least 8 (as done below). If zero is
         * used, this again means full checksum coverage.                     */
        case UDPLITE_RECV_CSCOV:
                if (!up->pcflag)         /* Disable the option on UDP sockets */
                        return -ENOPROTOOPT;
                if (val != 0 && val < 8) /* Avoid silly minimal values.       */
                        val = 8;
                up->pcrlen = val;
                up->pcflag |= UDPLITE_RECV_CC;
                break;

        default:
                err = -ENOPROTOOPT;
                break;
        }

        return err;
}

int udp_setsockopt(struct sock *sk, int level, int optname,
                   char __user *optval, int optlen)
{
        if (level == SOL_UDP  ||  level == SOL_UDPLITE)
                return udp_lib_setsockopt(sk, level, optname, optval, optlen,
                                          udp_push_pending_frames);
        return ip_setsockopt(sk, level, optname, optval, optlen);
}

#ifdef CONFIG_COMPAT
int compat_udp_setsockopt(struct sock *sk, int level, int optname,
                          char __user *optval, int optlen)
{
        if (level == SOL_UDP  ||  level == SOL_UDPLITE)
                return udp_lib_setsockopt(sk, level, optname, optval, optlen,
                                          udp_push_pending_frames);
        return compat_ip_setsockopt(sk, level, optname, optval, optlen);
}
#endif

int udp_lib_getsockopt(struct sock *sk, int level, int optname,
                       char __user *optval, int __user *optlen)
{
        struct udp_sock *up = udp_sk(sk);
        int val, len;

        if (get_user(len,optlen))
                return -EFAULT;

        len = min_t(unsigned int, len, sizeof(int));

        if (len < 0)
                return -EINVAL;

        switch (optname) {
        case UDP_CORK:
                val = up->corkflag;
                break;

        case UDP_ENCAP:
                val = up->encap_type;
                break;

        /* The following two cannot be changed on UDP sockets, the return is
         * always 0 (which corresponds to the full checksum coverage of UDP). */
        case UDPLITE_SEND_CSCOV:
                val = up->pcslen;
                break;

        case UDPLITE_RECV_CSCOV:
                val = up->pcrlen;
                break;

        default:
                return -ENOPROTOOPT;
        }

        if (put_user(len, optlen))
                return -EFAULT;
        if (copy_to_user(optval, &val,len))
                return -EFAULT;
        return 0;
}

int udp_getsockopt(struct sock *sk, int level, int optname,
                   char __user *optval, int __user *optlen)
{
        if (level == SOL_UDP  ||  level == SOL_UDPLITE)
                return udp_lib_getsockopt(sk, level, optname, optval, optlen);
        return ip_getsockopt(sk, level, optname, optval, optlen);
}

#ifdef CONFIG_COMPAT
int compat_udp_getsockopt(struct sock *sk, int level, int optname,
                                 char __user *optval, int __user *optlen)
{
        if (level == SOL_UDP  ||  level == SOL_UDPLITE)
                return udp_lib_getsockopt(sk, level, optname, optval, optlen);
        return compat_ip_getsockopt(sk, level, optname, optval, optlen);
}
#endif
/**
 *      udp_poll - wait for a UDP event.
 *      @file - file struct
 *      @sock - socket
 *      @wait - poll table
 *
 *      This is same as datagram poll, except for the special case of
 *      blocking sockets. If application is using a blocking fd
 *      and a packet with checksum error is in the queue;
 *      then it could get return from select indicating data available
 *      but then block when reading it. Add special case code
 *      to work around these arguably broken applications.
 */
unsigned int udp_poll(struct file *file, struct socket *sock, poll_table *wait)
{
        unsigned int mask = datagram_poll(file, sock, wait);
        struct sock *sk = sock->sk;
        int     is_lite = IS_UDPLITE(sk);

        /* Check for false positives due to checksum errors */
        if ( (mask & POLLRDNORM) &&
             !(file->f_flags & O_NONBLOCK) &&
             !(sk->sk_shutdown & RCV_SHUTDOWN)){
                struct sk_buff_head *rcvq = &sk->sk_receive_queue;
                struct sk_buff *skb;

                spin_lock_bh(&rcvq->lock);
                while ((skb = skb_peek(rcvq)) != NULL &&
                       udp_lib_checksum_complete(skb)) {
                        UDP_INC_STATS_BH(UDP_MIB_INERRORS, is_lite);
                        __skb_unlink(skb, rcvq);
                        kfree_skb(skb);
                }
                spin_unlock_bh(&rcvq->lock);

                /* nothing to see, move along */
                if (skb == NULL)
                        mask &= ~(POLLIN | POLLRDNORM);
        }

        return mask;

}

struct proto udp_prot = {
        .name              = "UDP",
        .owner             = THIS_MODULE,
        .close             = udp_lib_close,
        .connect           = ip4_datagram_connect,
        .disconnect        = udp_disconnect,
        .ioctl             = udp_ioctl,
        .destroy           = udp_destroy_sock,
        .setsockopt        = udp_setsockopt,
        .getsockopt        = udp_getsockopt,
        .sendmsg           = udp_sendmsg,
        .recvmsg           = udp_recvmsg,
        .sendpage          = udp_sendpage,
        .backlog_rcv       = udp_queue_rcv_skb,
        .hash              = udp_lib_hash,
        .unhash            = udp_lib_unhash,
        .get_port          = udp_v4_get_port,
        .obj_size          = sizeof(struct udp_sock),
#ifdef CONFIG_COMPAT
        .compat_setsockopt = compat_udp_setsockopt,
        .compat_getsockopt = compat_udp_getsockopt,
#endif
};

/* ------------------------------------------------------------------------ */
#ifdef CONFIG_PROC_FS

static struct sock *udp_get_first(struct seq_file *seq)
{
        struct sock *sk;
        struct udp_iter_state *state = seq->private;

        for (state->bucket = 0; state->bucket < UDP_HTABLE_SIZE; ++state->bucket) {
                struct hlist_node *node;
                sk_for_each(sk, node, state->hashtable + state->bucket) {
                        if (sk->sk_family == state->family)
                                goto found;
                }
        }
        sk = NULL;
found:
        return sk;
}

static struct sock *udp_get_next(struct seq_file *seq, struct sock *sk)
{
        struct udp_iter_state *state = seq->private;

        do {
                sk = sk_next(sk);
try_again:
                ;
        } while (sk && sk->sk_family != state->family);

        if (!sk && ++state->bucket < UDP_HTABLE_SIZE) {
                sk = sk_head(state->hashtable + state->bucket);
                goto try_again;
        }
        return sk;
}

static struct sock *udp_get_idx(struct seq_file *seq, loff_t pos)
{
        struct sock *sk = udp_get_first(seq);

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

static void *udp_seq_start(struct seq_file *seq, loff_t *pos)
{
        read_lock(&udp_hash_lock);
        return *pos ? udp_get_idx(seq, *pos-1) : (void *)1;
}

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

        if (v == (void *)1)
                sk = udp_get_idx(seq, 0);
        else
                sk = udp_get_next(seq, v);

        ++*pos;
        return sk;
}

static void udp_seq_stop(struct seq_file *seq, void *v)
{
        read_unlock(&udp_hash_lock);
}

static int udp_seq_open(struct inode *inode, struct file *file)
{
        struct udp_seq_afinfo *afinfo = PDE(inode)->data;
        struct seq_file *seq;
        int rc = -ENOMEM;
        struct udp_iter_state *s = kzalloc(sizeof(*s), GFP_KERNEL);

        if (!s)
                goto out;
        s->family               = afinfo->family;
        s->hashtable            = afinfo->hashtable;
        s->seq_ops.start        = udp_seq_start;
        s->seq_ops.next         = udp_seq_next;
        s->seq_ops.show         = afinfo->seq_show;
        s->seq_ops.stop         = udp_seq_stop;

        rc = seq_open(file, &s->seq_ops);
        if (rc)
                goto out_kfree;

        seq          = file->private_data;
        seq->private = s;
out:
        return rc;
out_kfree:
        kfree(s);
        goto out;
}

/* ------------------------------------------------------------------------ */
int udp_proc_register(struct udp_seq_afinfo *afinfo)
{
        struct proc_dir_entry *p;
        int rc = 0;

        if (!afinfo)
                return -EINVAL;
        afinfo->seq_fops->owner         = afinfo->owner;
        afinfo->seq_fops->open          = udp_seq_open;
        afinfo->seq_fops->read          = seq_read;
        afinfo->seq_fops->llseek        = seq_lseek;
        afinfo->seq_fops->release       = seq_release_private;

        p = proc_net_fops_create(afinfo->name, S_IRUGO, afinfo->seq_fops);
        if (p)
                p->data = afinfo;
        else
                rc = -ENOMEM;
        return rc;
}

void udp_proc_unregister(struct udp_seq_afinfo *afinfo)
{
        if (!afinfo)
                return;
        proc_net_remove(afinfo->name);
        memset(afinfo->seq_fops, 0, sizeof(*afinfo->seq_fops));
}

/* ------------------------------------------------------------------------ */
static void udp4_format_sock(struct sock *sp, char *tmpbuf, int bucket)
{
        struct inet_sock *inet = inet_sk(sp);
        __be32 dest = inet->daddr;
        __be32 src  = inet->rcv_saddr;
        __u16 destp       = ntohs(inet->dport);
        __u16 srcp        = ntohs(inet->sport);

        sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
                " %02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %p",
                bucket, src, srcp, dest, destp, sp->sk_state,
                atomic_read(&sp->sk_wmem_alloc),
                atomic_read(&sp->sk_rmem_alloc),
                0, 0L, 0, sock_i_uid(sp), 0, sock_i_ino(sp),
                atomic_read(&sp->sk_refcnt), sp);
}

int udp4_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");
        else {
                char tmpbuf[129];
                struct udp_iter_state *state = seq->private;

                udp4_format_sock(v, tmpbuf, state->bucket);
                seq_printf(seq, "%-127s\n", tmpbuf);
        }
        return 0;
}

/* ------------------------------------------------------------------------ */
static struct file_operations udp4_seq_fops;
static struct udp_seq_afinfo udp4_seq_afinfo = {
        .owner          = THIS_MODULE,
        .name           = "udp",
        .family         = AF_INET,
        .hashtable      = udp_hash,
        .seq_show       = udp4_seq_show,
        .seq_fops       = &udp4_seq_fops,
};

int __init udp4_proc_init(void)
{
        return udp_proc_register(&udp4_seq_afinfo);
}

void udp4_proc_exit(void)
{
        udp_proc_unregister(&udp4_seq_afinfo);
}
#endif /* CONFIG_PROC_FS */

EXPORT_SYMBOL(udp_disconnect);
EXPORT_SYMBOL(udp_hash);
EXPORT_SYMBOL(udp_hash_lock);
EXPORT_SYMBOL(udp_ioctl);
EXPORT_SYMBOL(udp_get_port);
EXPORT_SYMBOL(udp_prot);
EXPORT_SYMBOL(udp_sendmsg);
EXPORT_SYMBOL(udp_lib_getsockopt);
EXPORT_SYMBOL(udp_lib_setsockopt);
EXPORT_SYMBOL(udp_poll);

#ifdef CONFIG_PROC_FS
EXPORT_SYMBOL(udp_proc_register);
EXPORT_SYMBOL(udp_proc_unregister);
#endif