Ok. I didn't make 2.4.0 in 2000. Tough. I tried, but we had some

[davej-history.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 1.91 2000/11/28 13:38:38 davem Exp $
 *
 * Authors:     Ross Biro, <bir7@leland.Stanford.Edu>
 *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 *              Alan Cox, <Alan.Cox@linux.org>
 *
 * 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
 *
 *
 *              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.
 */
 
/* RFC1122 Status:
   4.1.3.1 (Ports):
     SHOULD send ICMP_PORT_UNREACHABLE in response to datagrams to 
       an un-listened port. (OK)
   4.1.3.2 (IP Options)
     MUST pass IP options from IP -> application (OK)
     MUST allow application to specify IP options (OK)
   4.1.3.3 (ICMP Messages)
     MUST pass ICMP error messages to application (OK -- except when SO_BSDCOMPAT is set)
   4.1.3.4 (UDP Checksums)
     MUST provide facility for checksumming (OK)
     MAY allow application to control checksumming (OK)
     MUST default to checksumming on (OK)
     MUST discard silently datagrams with bad csums (OK, except during debugging)
   4.1.3.5 (UDP Multihoming)
     MUST allow application to specify source address (OK)
     SHOULD be able to communicate the chosen src addr up to application
       when application doesn't choose (DOES - use recvmsg cmsgs)
   4.1.3.6 (Invalid Addresses)
     MUST discard invalid source addresses (OK -- done in the new routing code)
     MUST only send datagrams with one of our addresses (OK)
*/

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

/*
 *      Snmp MIB for the UDP layer
 */

struct udp_mib          udp_statistics[NR_CPUS*2];

struct sock *udp_hash[UDP_HTABLE_SIZE];
rwlock_t udp_hash_lock = RW_LOCK_UNLOCKED;

/* Shared by v4/v6 udp. */
int udp_port_rover;

static int udp_v4_get_port(struct sock *sk, unsigned short snum)
{
        write_lock_bh(&udp_hash_lock);
        if (snum == 0) {
                int best_size_so_far, best, result, i;

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

                        sk = udp_hash[result & (UDP_HTABLE_SIZE - 1)];
                        if (!sk) {
                                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;
                        do {
                                if (++size >= best_size_so_far)
                                        goto next;
                        } while ((sk = sk->next) != NULL);
                        best_size_so_far = size;
                        best = result;
                next:
                }
                result = best;
                for(;; 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_lport_inuse(result))
                                break;
                }
gotit:
                udp_port_rover = snum = result;
        } else {
                struct sock *sk2;

                for (sk2 = udp_hash[snum & (UDP_HTABLE_SIZE - 1)];
                     sk2 != NULL;
                     sk2 = sk2->next) {
                        if (sk2->num == snum &&
                            sk2 != sk &&
                            sk2->bound_dev_if == sk->bound_dev_if &&
                            (!sk2->rcv_saddr ||
                             !sk->rcv_saddr ||
                             sk2->rcv_saddr == sk->rcv_saddr) &&
                            (!sk2->reuse || !sk->reuse))
                                goto fail;
                }
        }
        sk->num = snum;
        if (sk->pprev == NULL) {
                struct sock **skp = &udp_hash[snum & (UDP_HTABLE_SIZE - 1)];
                if ((sk->next = *skp) != NULL)
                        (*skp)->pprev = &sk->next;
                *skp = sk;
                sk->pprev = skp;
                sock_prot_inc_use(sk->prot);
                sock_hold(sk);
        }
        write_unlock_bh(&udp_hash_lock);
        return 0;

fail:
        write_unlock_bh(&udp_hash_lock);
        return 1;
}

static void udp_v4_hash(struct sock *sk)
{
        BUG();
}

static void udp_v4_unhash(struct sock *sk)
{
        write_lock_bh(&udp_hash_lock);
        if (sk->pprev) {
                if (sk->next)
                        sk->next->pprev = sk->pprev;
                *sk->pprev = sk->next;
                sk->pprev = NULL;
                sk->num = 0;
                sock_prot_dec_use(sk->prot);
                __sock_put(sk);
        }
        write_unlock_bh(&udp_hash_lock);
}

/* UDP is nearly always wildcards out the wazoo, it makes no sense to try
 * harder than this. -DaveM
 */
struct sock *udp_v4_lookup_longway(u32 saddr, u16 sport, u32 daddr, u16 dport, int dif)
{
        struct sock *sk, *result = NULL;
        unsigned short hnum = ntohs(dport);
        int badness = -1;

        for(sk = udp_hash[hnum & (UDP_HTABLE_SIZE - 1)]; sk != NULL; sk = sk->next) {
                if(sk->num == hnum) {
                        int score = 0;
                        if(sk->rcv_saddr) {
                                if(sk->rcv_saddr != daddr)
                                        continue;
                                score++;
                        }
                        if(sk->daddr) {
                                if(sk->daddr != saddr)
                                        continue;
                                score++;
                        }
                        if(sk->dport) {
                                if(sk->dport != sport)
                                        continue;
                                score++;
                        }
                        if(sk->bound_dev_if) {
                                if(sk->bound_dev_if != dif)
                                        continue;
                                score++;
                        }
                        if(score == 4) {
                                result = sk;
                                break;
                        } else if(score > badness) {
                                result = sk;
                                badness = score;
                        }
                }
        }
        return result;
}

__inline__ struct sock *udp_v4_lookup(u32 saddr, u16 sport, u32 daddr, u16 dport, int dif)
{
        struct sock *sk;

        read_lock(&udp_hash_lock);
        sk = udp_v4_lookup_longway(saddr, sport, daddr, dport, dif);
        if (sk)
                sock_hold(sk);
        read_unlock(&udp_hash_lock);
        return sk;
}

static inline struct sock *udp_v4_mcast_next(struct sock *sk,
                                             u16 loc_port, u32 loc_addr,
                                             u16 rmt_port, u32 rmt_addr,
                                             int dif)
{
        struct sock *s = sk;
        unsigned short hnum = ntohs(loc_port);
        for(; s; s = s->next) {
                if ((s->num != hnum)                                    ||
                    (s->daddr && s->daddr!=rmt_addr)                    ||
                    (s->dport != rmt_port && s->dport != 0)                     ||
                    (s->rcv_saddr  && s->rcv_saddr != loc_addr)         ||
                    (s->bound_dev_if && s->bound_dev_if != dif))
                        continue;
                break;
        }
        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 udp_err(struct sk_buff *skb, unsigned char *dp, int len)
{
        struct iphdr *iph = (struct iphdr*)dp;
        struct udphdr *uh = (struct udphdr*)(dp+(iph->ihl<<2));
        int type = skb->h.icmph->type;
        int code = skb->h.icmph->code;
        struct sock *sk;
        int harderr;
        u32 info;
        int err;

        if (len < (iph->ihl<<2)+sizeof(struct udphdr)) {
                ICMP_INC_STATS_BH(IcmpInErrors);
                return;
        }

        sk = udp_v4_lookup(iph->daddr, uh->dest, iph->saddr, uh->source, skb->dev->ifindex);
        if (sk == NULL) {
                ICMP_INC_STATS_BH(IcmpInErrors);
                return; /* No socket for error */
        }

        err = 0;
        info = 0;
        harderr = 0;

        switch (type) {
        default:
        case ICMP_TIME_EXCEEDED:
                err = EHOSTUNREACH;
                break;
        case ICMP_SOURCE_QUENCH:
                goto out;
        case ICMP_PARAMETERPROB:
                err = EPROTO;
                info = ntohl(skb->h.icmph->un.gateway)>>24;
                harderr = 1;
                break;
        case ICMP_DEST_UNREACH:
                if (code == ICMP_FRAG_NEEDED) { /* Path MTU discovery */
                        if (sk->protinfo.af_inet.pmtudisc != IP_PMTUDISC_DONT) {
                                err = EMSGSIZE;
                                info = ntohs(skb->h.icmph->un.frag.mtu);
                                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 (!sk->protinfo.af_inet.recverr) {
                if (!harderr || sk->state != TCP_ESTABLISHED)
                        goto out;
        } else {
                ip_icmp_error(sk, skb, err, uh->dest, info, (u8*)(uh+1));
        }
        sk->err = err;
        sk->error_report(sk);
out:
        sock_put(sk);
}


static unsigned short udp_check(struct udphdr *uh, int len, unsigned long saddr, unsigned long daddr, unsigned long base)
{
        return(csum_tcpudp_magic(saddr, daddr, len, IPPROTO_UDP, base));
}

struct udpfakehdr 
{
        struct udphdr uh;
        u32 saddr;
        u32 daddr;
        struct iovec *iov;
        u32 wcheck;
};

/*
 *      Copy and checksum a UDP packet from user space into a buffer. We still have
 *      to do the planning to get ip_build_xmit to spot direct transfer to network
 *      card and provide an additional callback mode for direct user->board I/O
 *      transfers. That one will be fun.
 */
 
static int udp_getfrag(const void *p, char * to, unsigned int offset, unsigned int fraglen) 
{
        struct udpfakehdr *ufh = (struct udpfakehdr *)p;
        if (offset==0) {
                if (csum_partial_copy_fromiovecend(to+sizeof(struct udphdr), ufh->iov, offset,
                                                   fraglen-sizeof(struct udphdr), &ufh->wcheck))
                        return -EFAULT;
                ufh->wcheck = csum_partial((char *)ufh, sizeof(struct udphdr),
                                           ufh->wcheck);
                ufh->uh.check = csum_tcpudp_magic(ufh->saddr, ufh->daddr, 
                                          ntohs(ufh->uh.len),
                                          IPPROTO_UDP, ufh->wcheck);
                if (ufh->uh.check == 0)
                        ufh->uh.check = -1;
                memcpy(to, ufh, sizeof(struct udphdr));
                return 0;
        }
        if (csum_partial_copy_fromiovecend(to, ufh->iov, offset-sizeof(struct udphdr),
                                           fraglen, &ufh->wcheck))
                return -EFAULT;
        return 0;
}

/*
 *      Unchecksummed UDP is sufficiently critical to stuff like ATM video conferencing
 *      that we use two routines for this for speed. Probably we ought to have a
 *      CONFIG_FAST_NET set for >10Mb/second boards to activate this sort of coding.
 *      Timing needed to verify if this is a valid decision.
 */
 
static int udp_getfrag_nosum(const void *p, char * to, unsigned int offset, unsigned int fraglen) 
{
        struct udpfakehdr *ufh = (struct udpfakehdr *)p;

        if (offset==0) {
                memcpy(to, ufh, sizeof(struct udphdr));
                return memcpy_fromiovecend(to+sizeof(struct udphdr), ufh->iov, offset,
                                           fraglen-sizeof(struct udphdr));
        }
        return memcpy_fromiovecend(to, ufh->iov, offset-sizeof(struct udphdr),
                                   fraglen);
}

int udp_sendmsg(struct sock *sk, struct msghdr *msg, int len)
{
        int ulen = len + sizeof(struct udphdr);
        struct ipcm_cookie ipc;
        struct udpfakehdr ufh;
        struct rtable *rt = NULL;
        int free = 0;
        int connected = 0;
        u32 daddr;
        u8  tos;
        int err;

        /* This check is ONLY to check for arithmetic overflow
           on integer(!) len. Not more! Real check will be made
           in ip_build_xmit --ANK

           BTW socket.c -> af_*.c -> ... make multiple
           invalid conversions size_t -> int. We MUST repair it f.e.
           by replacing all of them with size_t and revise all
           the places sort of len += sizeof(struct iphdr)
           If len was ULONG_MAX-10 it would be cathastrophe  --ANK
         */

        if (len < 0 || len > 0xFFFF)
                return -EMSGSIZE;

        /* 
         *      Check the flags.
         */

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

        /*
         *      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 -EINVAL;
                }

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

        ipc.opt = NULL;
        ipc.oif = 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 = sk->protinfo.af_inet.opt;

        ufh.saddr = ipc.addr;
        ipc.addr = daddr = ufh.daddr;

        if (ipc.opt && ipc.opt->srr) {
                if (!daddr)
                        return -EINVAL;
                daddr = ipc.opt->faddr;
                connected = 0;
        }
        tos = RT_TOS(sk->protinfo.af_inet.tos);
        if (sk->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 = sk->protinfo.af_inet.mc_index;
                if (!ufh.saddr)
                        ufh.saddr = sk->protinfo.af_inet.mc_addr;
                connected = 0;
        }

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

        if (rt == NULL) {
                err = ip_route_output(&rt, daddr, ufh.saddr, tos, ipc.oif);
                if (err)
                        goto out;

                err = -EACCES;
                if (rt->rt_flags&RTCF_BROADCAST && !sk->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:

        ufh.saddr = rt->rt_src;
        if (!ipc.addr)
                ufh.daddr = ipc.addr = rt->rt_dst;
        ufh.uh.len = htons(ulen);
        ufh.uh.check = 0;
        ufh.iov = msg->msg_iov;
        ufh.wcheck = 0;

        /* RFC1122: OK.  Provides the checksumming facility (MUST) as per */
        /* 4.1.3.4. It's configurable by the application via setsockopt() */
        /* (MAY) and it defaults to on (MUST). */

        err = ip_build_xmit(sk,
                            (sk->no_check == UDP_CSUM_NOXMIT ?
                             udp_getfrag_nosum :
                             udp_getfrag),
                            &ufh, ulen, &ipc, rt, msg->msg_flags);

out:
        ip_rt_put(rt);
        if (free)
                kfree(ipc.opt);
        if (!err) {
                UDP_INC_STATS_USER(UdpOutDatagrams);
                return len;
        }
        return err;

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

/*
 *      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->wmem_alloc);
                        return put_user(amount, (int *)arg);
                }

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

                        amount = 0;
                        spin_lock_irq(&sk->receive_queue.lock);
                        skb = skb_peek(&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_irq(&sk->receive_queue.lock);
                        return put_user(amount, (int *)arg);
                }

                default:
                        return -ENOIOCTLCMD;
        }
        return(0);
}

static __inline__ int __udp_checksum_complete(struct sk_buff *skb)
{
        return (unsigned short)csum_fold(csum_partial(skb->h.raw, skb->len, skb->csum));
}

static __inline__ int udp_checksum_complete(struct sk_buff *skb)
{
        return skb->ip_summed != CHECKSUM_UNNECESSARY &&
                __udp_checksum_complete(skb);
}

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

int udp_recvmsg(struct sock *sk, struct msghdr *msg, int len,
                int noblock, int flags, int *addr_len)
{
        struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
        struct sk_buff *skb;
        int copied, err;

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

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

        /*
         *      From here the generic datagram does a lot of the work. Come
         *      the finished NET3, it will do _ALL_ the work!
         */

        skb = skb_recv_datagram(sk, flags, noblock, &err);
        if (!skb)
                goto out;
  
        copied = skb->len - sizeof(struct udphdr);
        if (copied > len) {
                copied = len;
                msg->msg_flags |= MSG_TRUNC;
        }

        if (skb->ip_summed==CHECKSUM_UNNECESSARY) {
                err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov,
                                              copied);
        } else if (msg->msg_flags&MSG_TRUNC) {
                if (__udp_checksum_complete(skb))
                        goto csum_copy_err;
                err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov,
                                              copied);
        } else {
                err = copy_and_csum_toiovec(msg->msg_iov, skb, sizeof(struct udphdr));

                if (err)
                        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 = skb->h.uh->source;
                sin->sin_addr.s_addr = skb->nh.iph->saddr;
                memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
        }
        if (sk->protinfo.af_inet.cmsg_flags)
                ip_cmsg_recv(msg, skb);
        err = copied;
  
out_free:
        skb_free_datagram(sk, skb);
out:
        return err;

csum_copy_err:
        UDP_INC_STATS_BH(UdpInErrors);

        /* Clear queue. */
        if (flags&MSG_PEEK) {
                int clear = 0;
                spin_lock_irq(&sk->receive_queue.lock);
                if (skb == skb_peek(&sk->receive_queue)) {
                        __skb_unlink(skb, &sk->receive_queue);
                        clear = 1;
                }
                spin_unlock_irq(&sk->receive_queue.lock);
                if (clear)
                        kfree_skb(skb);
        }

        skb_free_datagram(sk, skb);

        return -EAGAIN; 
}

int udp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
{
        struct sockaddr_in *usin = (struct sockaddr_in *) uaddr;
        struct rtable *rt;
        int err;

        
        if (addr_len < sizeof(*usin)) 
                return -EINVAL;

        if (usin->sin_family != AF_INET) 
                return -EAFNOSUPPORT;

        sk_dst_reset(sk);

        err = ip_route_connect(&rt, usin->sin_addr.s_addr, sk->saddr,
                               sk->protinfo.af_inet.tos|sk->localroute, sk->bound_dev_if);
        if (err)
                return err;
        if ((rt->rt_flags&RTCF_BROADCAST) && !sk->broadcast) {
                ip_rt_put(rt);
                return -EACCES;
        }
        if(!sk->saddr)
                sk->saddr = rt->rt_src;         /* Update source address */
        if(!sk->rcv_saddr)
                sk->rcv_saddr = rt->rt_src;
        sk->daddr = rt->rt_dst;
        sk->dport = usin->sin_port;
        sk->state = TCP_ESTABLISHED;

        sk_dst_set(sk, &rt->u.dst);
        return(0);
}

int udp_disconnect(struct sock *sk, int flags)
{
        /*
         *      1003.1g - break association.
         */
         
        sk->state = TCP_CLOSE;
        sk->daddr = 0;
        sk->dport = 0;
        sk->bound_dev_if = 0;
        if (!(sk->userlocks&SOCK_BINDADDR_LOCK)) {
                sk->rcv_saddr = 0;
                sk->saddr = 0;
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
                memset(&sk->net_pinfo.af_inet6.saddr, 0, 16);
                memset(&sk->net_pinfo.af_inet6.rcv_saddr, 0, 16);
#endif
        }
        if (!(sk->userlocks&SOCK_BINDPORT_LOCK)) {
                sk->prot->unhash(sk);
                sk->sport = 0;
        }
        sk_dst_reset(sk);
        return 0;
}

static void udp_close(struct sock *sk, long timeout)
{
        inet_sock_release(sk);
}

static int udp_queue_rcv_skb(struct sock * sk, struct sk_buff *skb)
{
        /*
         *      Charge it to the socket, dropping if the queue is full.
         */

#if defined(CONFIG_FILTER)
        if (sk->filter && skb->ip_summed != CHECKSUM_UNNECESSARY) {
                if (__udp_checksum_complete(skb)) {
                        UDP_INC_STATS_BH(UdpInErrors);
                        IP_INC_STATS_BH(IpInDiscards);
                        ip_statistics[smp_processor_id()*2].IpInDelivers--;
                        kfree_skb(skb);
                        return -1;
                }
                skb->ip_summed = CHECKSUM_UNNECESSARY;
        }
#endif

        if (sock_queue_rcv_skb(sk,skb)<0) {
                UDP_INC_STATS_BH(UdpInErrors);
                IP_INC_STATS_BH(IpInDiscards);
                ip_statistics[smp_processor_id()*2].IpInDelivers--;
                kfree_skb(skb);
                return -1;
        }
        UDP_INC_STATS_BH(UdpInDatagrams);
        return 0;
}

/*
 *      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 udp_v4_mcast_deliver(struct sk_buff *skb, struct udphdr *uh,
                                 u32 saddr, u32 daddr)
{
        struct sock *sk;
        int dif;

        read_lock(&udp_hash_lock);
        sk = udp_hash[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, uh->dest, daddr,
                                                   uh->source, saddr, dif);
                        if(sknext)
                                skb1 = skb_clone(skb, GFP_ATOMIC);

                        if(skb1)
                                udp_queue_rcv_skb(sk, 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 int udp_checksum_init(struct sk_buff *skb, struct udphdr *uh,
                             unsigned short ulen, u32 saddr, u32 daddr)
{
        if (uh->check == 0) {
                skb->ip_summed = CHECKSUM_UNNECESSARY;
        } else if (skb->ip_summed == CHECKSUM_HW) {
                if (udp_check(uh, ulen, saddr, daddr, skb->csum))
                        return -1;
                skb->ip_summed = CHECKSUM_UNNECESSARY;
        } else if (skb->ip_summed != CHECKSUM_UNNECESSARY)
                skb->csum = csum_tcpudp_nofold(saddr, daddr, ulen, IPPROTO_UDP, 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 udp_rcv(struct sk_buff *skb, unsigned short len)
{
        struct sock *sk;
        struct udphdr *uh;
        unsigned short ulen;
        struct rtable *rt = (struct rtable*)skb->dst;
        u32 saddr = skb->nh.iph->saddr;
        u32 daddr = skb->nh.iph->daddr;

        /*
         *      Get the header.
         */
         
        uh = skb->h.uh;
        __skb_pull(skb, skb->h.raw - skb->data);

        IP_INC_STATS_BH(IpInDelivers);

        /*
         *      Validate the packet and the UDP length.
         */
         
        ulen = ntohs(uh->len);

        if (ulen > len || ulen < sizeof(*uh)) {
                NETDEBUG(printk(KERN_DEBUG "UDP: short packet: %d/%d\n", ulen, len));
                UDP_INC_STATS_BH(UdpInErrors);
                kfree_skb(skb);
                return(0);
        }
        skb_trim(skb, ulen);

        if (udp_checksum_init(skb, uh, ulen, saddr, daddr) < 0)
                goto csum_error;

        if(rt->rt_flags & (RTCF_BROADCAST|RTCF_MULTICAST))
                return udp_v4_mcast_deliver(skb, uh, saddr, daddr);

        sk = udp_v4_lookup(saddr, uh->source, daddr, uh->dest, skb->dev->ifindex);

        if (sk != NULL) {
                udp_queue_rcv_skb(sk, skb);
                sock_put(sk);
                return 0;
        }

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

        UDP_INC_STATS_BH(UdpNoPorts);
        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);

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

static void get_udp_sock(struct sock *sp, char *tmpbuf, int i)
{
        unsigned int dest, src;
        __u16 destp, srcp;

        dest  = sp->daddr;
        src   = sp->rcv_saddr;
        destp = ntohs(sp->dport);
        srcp  = ntohs(sp->sport);
        sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
                " %02X %08X:%08X %02X:%08lX %08X %5d %8d %ld %d %p",
                i, src, srcp, dest, destp, sp->state, 
                atomic_read(&sp->wmem_alloc), atomic_read(&sp->rmem_alloc),
                0, 0L, 0,
                sock_i_uid(sp), 0,
                sock_i_ino(sp),
                atomic_read(&sp->refcnt), sp);
}

int udp_get_info(char *buffer, char **start, off_t offset, int length)
{
        int len = 0, num = 0, i;
        off_t pos = 0;
        off_t begin;
        char tmpbuf[129];

        if (offset < 128) 
                len += sprintf(buffer, "%-127s\n",
                               "  sl  local_address rem_address   st tx_queue "
                               "rx_queue tr tm->when retrnsmt   uid  timeout inode");
        pos = 128;
        read_lock(&udp_hash_lock);
        for (i = 0; i < UDP_HTABLE_SIZE; i++) {
                struct sock *sk;

                for (sk = udp_hash[i]; sk; sk = sk->next, num++) {
                        if (sk->family != PF_INET)
                                continue;
                        pos += 128;
                        if (pos <= offset)
                                continue;
                        get_udp_sock(sk, tmpbuf, i);
                        len += sprintf(buffer+len, "%-127s\n", tmpbuf);
                        if(len >= length)
                                goto out;
                }
        }
out:
        read_unlock(&udp_hash_lock);
        begin = len - (pos - offset);
        *start = buffer + begin;
        len -= begin;
        if(len > length)
                len = length;
        if (len < 0)
                len = 0; 
        return len;
}

struct proto udp_prot = {
        name:           "UDP",
        close:          udp_close,
        connect:        udp_connect,
        disconnect:     udp_disconnect,
        ioctl:          udp_ioctl,
        setsockopt:     ip_setsockopt,
        getsockopt:     ip_getsockopt,
        sendmsg:        udp_sendmsg,
        recvmsg:        udp_recvmsg,
        backlog_rcv:    udp_queue_rcv_skb,
        hash:           udp_v4_hash,
        unhash:         udp_v4_unhash,
        get_port:       udp_v4_get_port,
};