text: /*
   * 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).
   *
   * Authors:	Ross Biro
   *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
   *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
   *		Alan Cox, <alan@lxorguk.ukuu.org.uk>
   *		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/bootmem.h>
  #include <linux/highmem.h>
  #include <linux/swap.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 <linux/slab.h>
  #include <net/tcp_states.h>
  #include <linux/skbuff.h>
  #include <linux/proc_fs.h>
  #include <linux/seq_file.h>
  #include <net/net_namespace.h>
  #include <net/icmp.h>
  #include <net/route.h>
  #include <net/checksum.h>
  #include <net/xfrm.h>
  #include "udp_impl.h"
  
  struct udp_table udp_table __read_mostly;
  EXPORT_SYMBOL(udp_table);
  
  long sysctl_udp_mem[3] __read_mostly;
  EXPORT_SYMBOL(sysctl_udp_mem);
  
  int sysctl_udp_rmem_min __read_mostly;
  EXPORT_SYMBOL(sysctl_udp_rmem_min);
  
  int sysctl_udp_wmem_min __read_mostly;
  EXPORT_SYMBOL(sysctl_udp_wmem_min);
  
  atomic_long_t udp_memory_allocated;
  EXPORT_SYMBOL(udp_memory_allocated);
  
  #define MAX_UDP_PORTS 65536
  #define PORTS_PER_CHAIN (MAX_UDP_PORTS / UDP_HTABLE_SIZE_MIN)
  
  static int udp_lib_lport_inuse(struct net *net, __u16 num,
  			       const struct udp_hslot *hslot,
  			       unsigned long *bitmap,
  			       struct sock *sk,
  			       int (*saddr_comp)(const struct sock *sk1,
  						 const struct sock *sk2),
  			       unsigned int log)
  {
  	struct sock *sk2;
  	struct hlist_nulls_node *node;
  
  	sk_nulls_for_each(sk2, node, &hslot->head)
  		if (net_eq(sock_net(sk2), net) &&
  		    sk2 != sk &&
  		    (bitmap || udp_sk(sk2)->udp_port_hash == num) &&
  		    (!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)) {
  			if (bitmap)
  				__set_bit(udp_sk(sk2)->udp_port_hash >> log,
  					  bitmap);
  			else
  				return 1;
  		}
  	return 0;
  }
  
  /*
   * Note: we still hold spinlock of primary hash chain, so no other writer
   * can insert/delete a socket with local_port == num
   */
  static int udp_lib_lport_inuse2(struct net *net, __u16 num,
  			       struct udp_hslot *hslot2,
  			       struct sock *sk,
  			       int (*saddr_comp)(const struct sock *sk1,
  						 const struct sock *sk2))
  {
  	struct sock *sk2;
  	struct hlist_nulls_node *node;
  	int res = 0;
  
  	spin_lock(&hslot2->lock);
  	udp_portaddr_for_each_entry(sk2, node, &hslot2->head)
  		if (net_eq(sock_net(sk2), net) &&
  		    sk2 != sk &&
  		    (udp_sk(sk2)->udp_port_hash == num) &&
  		    (!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)) {
  			res = 1;
  			break;
  		}
  	spin_unlock(&hslot2->lock);
  	return res;
  }
  
  /**
   *  udp_lib_get_port  -  UDP/-Lite port lookup for IPv4 and IPv6
   *
   *  @sk:          socket struct in question
   *  @snum:        port number to look up
   *  @saddr_comp:  AF-dependent comparison of bound local IP addresses
   *  @hash2_nulladdr: AF-dependent hash value in secondary hash chains,
   *                   with NULL address
   */
  int udp_lib_get_port(struct sock *sk, unsigned short snum,
  		       int (*saddr_comp)(const struct sock *sk1,
  					 const struct sock *sk2),
  		     unsigned int hash2_nulladdr)
  {
  	struct udp_hslot *hslot, *hslot2;
  	struct udp_table *udptable = sk->sk_prot->h.udp_table;
  	int    error = 1;
  	struct net *net = sock_net(sk);
  
  	if (!snum) {
  		int low, high, remaining;
  		unsigned rand;
  		unsigned short first, last;
  		DECLARE_BITMAP(bitmap, PORTS_PER_CHAIN);
  
  		inet_get_local_port_range(&low, &high);
  		remaining = (high - low) + 1;
  
  		rand = net_random();
  		first = (((u64)rand * remaining) >> 32) + low;
  		/*
  		 * force rand to be an odd multiple of UDP_HTABLE_SIZE
  		 */
  		rand = (rand | 1) * (udptable->mask + 1);
  		last = first + udptable->mask + 1;
  		do {
  			hslot = udp_hashslot(udptable, net, first);
  			bitmap_zero(bitmap, PORTS_PER_CHAIN);
  			spin_lock_bh(&hslot->lock);
  			udp_lib_lport_inuse(net, snum, hslot, bitmap, sk,
  					    saddr_comp, udptable->log);
  
  			snum = first;
  			/*
  			 * Iterate on all possible values of snum for this hash.
  			 * Using steps of an odd multiple of UDP_HTABLE_SIZE
  			 * give us randomization and full range coverage.
  			 */
  			do {
  				if (low <= snum && snum <= high &&
  				    !test_bit(snum >> udptable->log, bitmap) &&
  				    !inet_is_reserved_local_port(snum))
  					goto found;
  				snum += rand;
  			} while (snum != first);
  			spin_unlock_bh(&hslot->lock);
  		} while (++first != last);
  		goto fail;
  	} else {
  		hslot = udp_hashslot(udptable, net, snum);
  		spin_lock_bh(&hslot->lock);
  		if (hslot->count > 10) {
  			int exist;
  			unsigned int slot2 = udp_sk(sk)->udp_portaddr_hash ^ snum;
  
  			slot2          &= udptable->mask;
  			hash2_nulladdr &= udptable->mask;
  
  			hslot2 = udp_hashslot2(udptable, slot2);
  			if (hslot->count < hslot2->count)
  				goto scan_primary_hash;
  
  			exist = udp_lib_lport_inuse2(net, snum, hslot2,
  						     sk, saddr_comp);
  			if (!exist && (hash2_nulladdr != slot2)) {
  				hslot2 = udp_hashslot2(udptable, hash2_nulladdr);
  				exist = udp_lib_lport_inuse2(net, snum, hslot2,
  							     sk, saddr_comp);
  			}
  			if (exist)
  				goto fail_unlock;
  			else
  				goto found;
  		}
  scan_primary_hash:
  		if (udp_lib_lport_inuse(net, snum, hslot, NULL, sk,
  					saddr_comp, 0))
  			goto fail_unlock;
  	}
  found:
  	inet_sk(sk)->inet_num = snum;
  	udp_sk(sk)->udp_port_hash = snum;
  	udp_sk(sk)->udp_portaddr_hash ^= snum;
  	if (sk_unhashed(sk)) {
  		sk_nulls_add_node_rcu(sk, &hslot->head);
  		hslot->count++;
  		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
  
  		hslot2 = udp_hashslot2(udptable, udp_sk(sk)->udp_portaddr_hash);
  		spin_lock(&hslot2->lock);
  		hlist_nulls_add_head_rcu(&udp_sk(sk)->udp_portaddr_node,
  					 &hslot2->head);
  		hslot2->count++;
  		spin_unlock(&hslot2->lock);
  	}
  	error = 0;
  fail_unlock:
  	spin_unlock_bh(&hslot->lock);
  fail:
  	return error;
  }
  EXPORT_SYMBOL(udp_lib_get_port);
  
  static 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->inet_rcv_saddr || !inet2->inet_rcv_saddr ||
  		   inet1->inet_rcv_saddr == inet2->inet_rcv_saddr));
  }
  
  static unsigned int udp4_portaddr_hash(struct net *net, __be32 saddr,
  				       unsigned int port)
  {
  	return jhash_1word((__force u32)saddr, net_hash_mix(net)) ^ port;
  }
  
  int udp_v4_get_port(struct sock *sk, unsigned short snum)
  {
  	unsigned int hash2_nulladdr =
  		udp4_portaddr_hash(sock_net(sk), htonl(INADDR_ANY), snum);
  	unsigned int hash2_partial =
  		udp4_portaddr_hash(sock_net(sk), inet_sk(sk)->inet_rcv_saddr, 0);
  
  	/* precompute partial secondary hash */
  	udp_sk(sk)->udp_portaddr_hash = hash2_partial;
  	return udp_lib_get_port(sk, snum, ipv4_rcv_saddr_equal, hash2_nulladdr);
  }
  
  static inline int compute_score(struct sock *sk, struct net *net, __be32 saddr,
  			 unsigned short hnum,
  			 __be16 sport, __be32 daddr, __be16 dport, int dif)
  {
  	int score = -1;
  
  	if (net_eq(sock_net(sk), net) && udp_sk(sk)->udp_port_hash == hnum &&
  			!ipv6_only_sock(sk)) {
  		struct inet_sock *inet = inet_sk(sk);
  
  		score = (sk->sk_family == PF_INET ? 1 : 0);
  		if (inet->inet_rcv_saddr) {
  			if (inet->inet_rcv_saddr != daddr)
  				return -1;
  			score += 2;
  		}
  		if (inet->inet_daddr) {
  			if (inet->inet_daddr != saddr)
  				return -1;
  			score += 2;
  		}
  		if (inet->inet_dport) {
  			if (inet->inet_dport != sport)
  				return -1;
  			score += 2;
  		}
  		if (sk->sk_bound_dev_if) {
  			if (sk->sk_bound_dev_if != dif)
  				return -1;
  			score += 2;
  		}
  	}
  	return score;
  }
  
  /*
   * In this second variant, we check (daddr, dport) matches (inet_rcv_sadd, inet_num)
   */
  #define SCORE2_MAX (1 + 2 + 2 + 2)
  static inline int compute_score2(struct sock *sk, struct net *net,
  				 __be32 saddr, __be16 sport,
  				 __be32 daddr, unsigned int hnum, int dif)
  {
  	int score = -1;
  
  	if (net_eq(sock_net(sk), net) && !ipv6_only_sock(sk)) {
  		struct inet_sock *inet = inet_sk(sk);
  
  		if (inet->inet_rcv_saddr != daddr)
  			return -1;
  		if (inet->inet_num != hnum)
  			return -1;
  
  		score = (sk->sk_family == PF_INET ? 1 : 0);
  		if (inet->inet_daddr) {
  			if (inet->inet_daddr != saddr)
  				return -1;
  			score += 2;
  		}
  		if (inet->inet_dport) {
  			if (inet->inet_dport != sport)
  				return -1;
  			score += 2;
  		}
  		if (sk->sk_bound_dev_if) {
  			if (sk->sk_bound_dev_if != dif)
  				return -1;
  			score += 2;
  		}
  	}
  	return score;
  }
  
  /* called with read_rcu_lock() */
  static struct sock *udp4_lib_lookup2(struct net *net,
  		__be32 saddr, __be16 sport,
  		__be32 daddr, unsigned int hnum, int dif,
  		struct udp_hslot *hslot2, unsigned int slot2)
  {
  	struct sock *sk, *result;
  	struct hlist_nulls_node *node;
  	int score, badness;
  
  begin:
  	result = NULL;
  	badness = -1;
  	udp_portaddr_for_each_entry_rcu(sk, node, &hslot2->head) {
  		score = compute_score2(sk, net, saddr, sport,
  				      daddr, hnum, dif);
  		if (score > badness) {
  			result = sk;
  			badness = score;
  			if (score == SCORE2_MAX)
  				goto exact_match;
  		}
  	}
  	/*
  	 * if the nulls value we got at the end of this lookup is
  	 * not the expected one, we must restart lookup.
  	 * We probably met an item that was moved to another chain.
  	 */
  	if (get_nulls_value(node) != slot2)
  		goto begin;
  
  	if (result) {
  exact_match:
  		if (unlikely(!atomic_inc_not_zero_hint(&result->sk_refcnt, 2)))
  			result = NULL;
  		else if (unlikely(compute_score2(result, net, saddr, sport,
  				  daddr, hnum, dif) < badness)) {
  			sock_put(result);
  			goto begin;
  		}
  	}
  	return result;
  }
  
  /* UDP is nearly always wildcards out the wazoo, it makes no sense to try
   * harder than this. -DaveM
   */
  static struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
  		__be16 sport, __be32 daddr, __be16 dport,
  		int dif, struct udp_table *udptable)
  {
  	struct sock *sk, *result;
  	struct hlist_nulls_node *node;
  	unsigned short hnum = ntohs(dport);
  	unsigned int hash2, slot2, slot = udp_hashfn(net, hnum, udptable->mask);
  	struct udp_hslot *hslot2, *hslot = &udptable->hash[slot];
  	int score, badness;
  
  	rcu_read_lock();
  	if (hslot->count > 10) {
  		hash2 = udp4_portaddr_hash(net, daddr, hnum);
  		slot2 = hash2 & udptable->mask;
  		hslot2 = &udptable->hash2[slot2];
  		if (hslot->count < hslot2->count)
  			goto begin;
  
  		result = udp4_lib_lookup2(net, saddr, sport,
  					  daddr, hnum, dif,
  					  hslot2, slot2);
  		if (!result) {
  			hash2 = udp4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
  			slot2 = hash2 & udptable->mask;
  			hslot2 = &udptable->hash2[slot2];
  			if (hslot->count < hslot2->count)
  				goto begin;
  
  			result = udp4_lib_lookup2(net, saddr, sport,
  						  htonl(INADDR_ANY), hnum, dif,
  						  hslot2, slot2);
  		}
  		rcu_read_unlock();
  		return result;
  	}
  begin:
  	result = NULL;
  	badness = -1;
  	sk_nulls_for_each_rcu(sk, node, &hslot->head) {
  		score = compute_score(sk, net, saddr, hnum, sport,
  				      daddr, dport, dif);
  		if (score > badness) {
  			result = sk;
  			badness = score;
  		}
  	}
  	/*
  	 * if the nulls value we got at the end of this lookup is
  	 * not the expected one, we must restart lookup.
  	 * We probably met an item that was moved to another chain.
  	 */
  	if (get_nulls_value(node) != slot)
  		goto begin;
  
  	if (result) {
  		if (unlikely(!atomic_inc_not_zero_hint(&result->sk_refcnt, 2)))
  			result = NULL;
  		else if (unlikely(compute_score(result, net, saddr, hnum, sport,
  				  daddr, dport, dif) < badness)) {
  			sock_put(result);
  			goto begin;
  		}
  	}
  	rcu_read_unlock();
  	return result;
  }
  
  static inline struct sock *__udp4_lib_lookup_skb(struct sk_buff *skb,
  						 __be16 sport, __be16 dport,
  						 struct udp_table *udptable)
  {
  	struct sock *sk;
  	const struct iphdr *iph = ip_hdr(skb);
  
  	if (unlikely(sk = skb_steal_sock(skb)))
  		return sk;
  	else
  		return __udp4_lib_lookup(dev_net(skb_dst(skb)->dev), iph->saddr, sport,
  					 iph->daddr, dport, inet_iif(skb),
  					 udptable);
  }
  
  struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
  			     __be32 daddr, __be16 dport, int dif)
  {
  	return __udp4_lib_lookup(net, saddr, sport, daddr, dport, dif, &udp_table);
  }
  EXPORT_SYMBOL_GPL(udp4_lib_lookup);
  
  static inline struct sock *udp_v4_mcast_next(struct net *net, struct sock *sk,
  					     __be16 loc_port, __be32 loc_addr,
  					     __be16 rmt_port, __be32 rmt_addr,
  					     int dif)
  {
  	struct hlist_nulls_node *node;
  	struct sock *s = sk;
  	unsigned short hnum = ntohs(loc_port);
  
  	sk_nulls_for_each_from(s, node) {
  		struct inet_sock *inet = inet_sk(s);
  
  		if (!net_eq(sock_net(s), net) ||
  		    udp_sk(s)->udp_port_hash != hnum ||
  		    (inet->inet_daddr && inet->inet_daddr != rmt_addr) ||
  		    (inet->inet_dport != rmt_port && inet->inet_dport) ||
  		    (inet->inet_rcv_saddr &&
  		     inet->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 udp_table *udptable)
  {
  	struct inet_sock *inet;
  	const struct iphdr *iph = (const 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;
  	struct net *net = dev_net(skb->dev);
  
  	sk = __udp4_lib_lookup(net, iph->daddr, uh->dest,
  			iph->saddr, uh->source, skb->dev->ifindex, udptable);
  	if (sk == NULL) {
  		ICMP_INC_STATS_BH(net, 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)
  {
  	__udp4_lib_err(skb, info, &udp_table);
  }
  
  /*
   * Throw away all pending data and cancel the corking. Socket is locked.
   */
  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);
  	}
  }
  EXPORT_SYMBOL(udp_flush_pending_frames);
  
  /**
   * 	udp4_hwcsum  -  handle outgoing HW checksumming
   * 	@skb: 	sk_buff containing the filled-in UDP header
   * 	        (checksum field must be zeroed out)
   *	@src:	source IP address
   *	@dst:	destination IP address
   */
  static void udp4_hwcsum(struct sk_buff *skb, __be32 src, __be32 dst)
  {
  	struct udphdr *uh = udp_hdr(skb);
  	struct sk_buff *frags = skb_shinfo(skb)->frag_list;
  	int offset = skb_transport_offset(skb);
  	int len = skb->len - offset;
  	int hlen = len;
  	__wsum csum = 0;
  
  	if (!frags) {
  		/*
  		 * 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
  		 */
  		do {
  			csum = csum_add(csum, frags->csum);
  			hlen -= frags->len;
  		} while ((frags = frags->next));
  
  		csum = skb_checksum(skb, offset, hlen, csum);
  		skb->ip_summed = CHECKSUM_NONE;
  
  		uh->check = csum_tcpudp_magic(src, dst, len, IPPROTO_UDP, csum);
  		if (uh->check == 0)
  			uh->check = CSUM_MANGLED_0;
  	}
  }
  
  static int udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4)
  {
  	struct sock *sk = skb->sk;
  	struct inet_sock *inet = inet_sk(sk);
  	struct udphdr *uh;
  	int err = 0;
  	int is_udplite = IS_UDPLITE(sk);
  	int offset = skb_transport_offset(skb);
  	int len = skb->len - offset;
  	__wsum csum = 0;
  
  	/*
  	 * Create a UDP header
  	 */
  	uh = udp_hdr(skb);
  	uh->source = inet->inet_sport;
  	uh->dest = fl4->fl4_dport;
  	uh->len = htons(len);
  	uh->check = 0;
  
  	if (is_udplite)  				 /*     UDP-Lite      */
  		csum = udplite_csum(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(skb, fl4->saddr, fl4->daddr);
  		goto send;
  
  	} else
  		csum = udp_csum(skb);
  
  	/* add protocol-dependent pseudo-header */
  	uh->check = csum_tcpudp_magic(fl4->saddr, fl4->daddr, len,
  				      sk->sk_protocol, csum);
  	if (uh->check == 0)
  		uh->check = CSUM_MANGLED_0;
  
  send:
  	err = ip_send_skb(skb);
  	if (err) {
  		if (err == -ENOBUFS && !inet->recverr) {
  			UDP_INC_STATS_USER(sock_net(sk),
  					   UDP_MIB_SNDBUFERRORS, is_udplite);
  			err = 0;
  		}
  	} else
  		UDP_INC_STATS_USER(sock_net(sk),
  				   UDP_MIB_OUTDATAGRAMS, is_udplite);
  	return err;
  }
  
  /*
   * Push out all pending data as one UDP datagram. Socket is locked.
   */
  int udp_push_pending_frames(struct sock *sk)
  {
  	struct udp_sock  *up = udp_sk(sk);
  	struct inet_sock *inet = inet_sk(sk);
  	struct flowi4 *fl4 = &inet->cork.fl.u.ip4;
  	struct sk_buff *skb;
  	int err = 0;
  
  	skb = ip_finish_skb(sk, fl4);
  	if (!skb)
  		goto out;
  
  	err = udp_send_skb(skb, fl4);
  
  out:
  	up->len = 0;
  	up->pending = 0;
  	return err;
  }
  EXPORT_SYMBOL(udp_push_pending_frames);
  
  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);
  	struct flowi4 fl4_stack;
  	struct flowi4 *fl4;
  	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 = IS_UDPLITE(sk);
  	int corkreq = up->corkflag || msg->msg_flags&MSG_MORE;
  	int (*getfrag)(void *, char *, int, int, int, struct sk_buff *);
  	struct sk_buff *skb;
  	struct ip_options_data opt_copy;
  
  	if (len > 0xFFFF)
  		return -EMSGSIZE;
  
  	/*
  	 *	Check the flags.
  	 */
  
  	if (msg->msg_flags & MSG_OOB) /* Mirror BSD error message compatibility */
  		return -EOPNOTSUPP;
  
  	ipc.opt = NULL;
  	ipc.tx_flags = 0;
  
  	getfrag = is_udplite ? udplite_getfrag : ip_generic_getfrag;
  
  	fl4 = &inet->cork.fl.u.ip4;
  	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->inet_daddr;
  		dport = inet->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->inet_saddr;
  
  	ipc.oif = sk->sk_bound_dev_if;
  	err = sock_tx_timestamp(sk, &ipc.tx_flags);
  	if (err)
  		return err;
  	if (msg->msg_controllen) {
  		err = ip_cmsg_send(sock_net(sk), msg, &ipc);
  		if (err)
  			return err;
  		if (ipc.opt)
  			free = 1;
  		connected = 0;
  	}
  	if (!ipc.opt) {
  		struct ip_options_rcu *inet_opt;
  
  		rcu_read_lock();
  		inet_opt = rcu_dereference(inet->inet_opt);
  		if (inet_opt) {
  			memcpy(&opt_copy, inet_opt,
  			       sizeof(*inet_opt) + inet_opt->opt.optlen);
  			ipc.opt = &opt_copy.opt;
  		}
  		rcu_read_unlock();
  	}
  
  	saddr = ipc.addr;
  	ipc.addr = faddr = daddr;
  
  	if (ipc.opt && ipc.opt->opt.srr) {
  		if (!daddr)
  			return -EINVAL;
  		faddr = ipc.opt->opt.faddr;
  		connected = 0;
  	}
  	tos = RT_TOS(inet->tos);
  	if (sock_flag(sk, SOCK_LOCALROUTE) ||
  	    (msg->msg_flags & MSG_DONTROUTE) ||
  	    (ipc.opt && ipc.opt->opt.is_strictroute)) {
  		tos |= RTO_ONLINK;
  		connected = 0;
  	}
  
  	if (ipv4_is_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 net *net = sock_net(sk);
  
  		fl4 = &fl4_stack;
  		flowi4_init_output(fl4, ipc.oif, sk->sk_mark, tos,
  				   RT_SCOPE_UNIVERSE, sk->sk_protocol,
  				   inet_sk_flowi_flags(sk)|FLOWI_FLAG_CAN_SLEEP,
  				   faddr, saddr, dport, inet->inet_sport);
  
  		security_sk_classify_flow(sk, flowi4_to_flowi(fl4));
  		rt = ip_route_output_flow(net, fl4, sk);
  		if (IS_ERR(rt)) {
  			err = PTR_ERR(rt);
  			rt = NULL;
  			if (err == -ENETUNREACH)
  				IP_INC_STATS_BH(net, IPSTATS_MIB_OUTNOROUTES);
  			goto out;
  		}
  
  		err = -EACCES;
  		if ((rt->rt_flags & RTCF_BROADCAST) &&
  		    !sock_flag(sk, SOCK_BROADCAST))
  			goto out;
  		if (connected)
  			sk_dst_set(sk, dst_clone(&rt->dst));
  	}
  
  	if (msg->msg_flags&MSG_CONFIRM)
  		goto do_confirm;
  back_from_confirm:
  
  	saddr = fl4->saddr;
  	if (!ipc.addr)
  		daddr = ipc.addr = fl4->daddr;
  
  	/* Lockless fast path for the non-corking case. */
  	if (!corkreq) {
  		skb = ip_make_skb(sk, fl4, getfrag, msg->msg_iov, ulen,
  				  sizeof(struct udphdr), &ipc, &rt,
  				  msg->msg_flags);
  		err = PTR_ERR(skb);
  		if (skb && !IS_ERR(skb))
  			err = udp_send_skb(skb, fl4);
  		goto out;
  	}
  
  	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.
  	 */
  	fl4 = &inet->cork.fl.u.ip4;
  	fl4->daddr = daddr;
  	fl4->saddr = saddr;
  	fl4->fl4_dport = dport;
  	fl4->fl4_sport = inet->inet_sport;
  	up->pending = AF_INET;
  
  do_append_data:
  	up->len += ulen;
  	err = ip_append_data(sk, fl4, 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)
  		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(sock_net(sk),
  				UDP_MIB_SNDBUFERRORS, is_udplite);
  	}
  	return err;
  
  do_confirm:
  	dst_confirm(&rt->dst);
  	if (!(msg->msg_flags&MSG_PROBE) || len)
  		goto back_from_confirm;
  	err = 0;
  	goto out;
  }
  EXPORT_SYMBOL(udp_sendmsg);
  
  int udp_sendpage(struct sock *sk, struct page *page, int offset,
  		 size_t size, int flags)
  {
  	struct inet_sock *inet = inet_sk(sk);
  	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, &inet->cork.fl.u.ip4,
  			     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;
  }
  
  /**
   *	first_packet_length	- return length of first packet in receive queue
   *	@sk: socket
   *
   *	Drops all bad checksum frames, until a valid one is found.
   *	Returns the length of found skb, or 0 if none is found.
   */
  static unsigned int first_packet_length(struct sock *sk)
  {
  	struct sk_buff_head list_kill, *rcvq = &sk->sk_receive_queue;
  	struct sk_buff *skb;
  	unsigned int res;
  
  	__skb_queue_head_init(&list_kill);
  
  	spin_lock_bh(&rcvq->lock);
  	while ((skb = skb_peek(rcvq)) != NULL &&
  		udp_lib_checksum_complete(skb)) {
  		UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_INERRORS,
  				 IS_UDPLITE(sk));
  		atomic_inc(&sk->sk_drops);
  		__skb_unlink(skb, rcvq);
  		__skb_queue_tail(&list_kill, skb);
  	}
  	res = skb ? skb->len : 0;
  	spin_unlock_bh(&rcvq->lock);
  
  	if (!skb_queue_empty(&list_kill)) {
  		bool slow = lock_sock_fast(sk);
  
  		__skb_queue_purge(&list_kill);
  		sk_mem_reclaim_partial(sk);
  		unlock_sock_fast(sk, slow);
  	}
  	return res;
  }
  
  /*
   *	IOCTL requests applicable to the UDP protocol
   */
  
  int udp_ioctl(struct sock *sk, int cmd, unsigned long arg)
  {
  	switch (cmd) {
  	case SIOCOUTQ:
  	{
  		int amount = sk_wmem_alloc_get(sk);
  
  		return put_user(amount, (int __user *)arg);
  	}
  
  	case SIOCINQ:
  	{
  		unsigned int amount = first_packet_length(sk);
  
  		if (amount)
  			/*
  			 * We will only return the amount
  			 * of this packet since that is all
  			 * that will be read.
  			 */
  			amount -= sizeof(struct udphdr);
  
  		return put_user(amount, (int __user *)arg);
  	}
  
  	default:
  		return -ENOIOCTLCMD;
  	}
  
  	return 0;
  }
  EXPORT_SYMBOL(udp_ioctl);
  
  /*
   * 	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;
  	int peeked;
  	int err;
  	int is_udplite = IS_UDPLITE(sk);
  	bool slow;
  
  	/*
  	 *	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 ? MSG_DONTWAIT : 0),
  				  &peeked, &err);
  	if (!skb)
  		goto out;
  
  	ulen = skb->len - sizeof(struct udphdr);
  	if (len > ulen)
  		len = ulen;
  	else if (len < 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 (len < 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, len);
  	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;
  
  	if (!peeked)
  		UDP_INC_STATS_USER(sock_net(sk),
  				UDP_MIB_INDATAGRAMS, is_udplite);
  
  	sock_recv_ts_and_drops(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 = len;
  	if (flags & MSG_TRUNC)
  		err = ulen;
  
  out_free:
  	skb_free_datagram_locked(sk, skb);
  out:
  	return err;
  
  csum_copy_err:
  	slow = lock_sock_fast(sk);
  	if (!skb_kill_datagram(sk, skb, flags))
  		UDP_INC_STATS_USER(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
  	unlock_sock_fast(sk, slow);
  
  	if (noblock)
  		return -EAGAIN;
  
  	/* starting over for a new packet */
  	msg->msg_flags &= ~MSG_TRUNC;
  	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->inet_daddr = 0;
  	inet->inet_dport = 0;
  	sock_rps_save_rxhash(sk, 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->inet_sport = 0;
  	}
  	sk_dst_reset(sk);
  	return 0;
  }
  EXPORT_SYMBOL(udp_disconnect);
  
  void udp_lib_unhash(struct sock *sk)
  {
  	if (sk_hashed(sk)) {
  		struct udp_table *udptable = sk->sk_prot->h.udp_table;
  		struct udp_hslot *hslot, *hslot2;
  
  		hslot  = udp_hashslot(udptable, sock_net(sk),
  				      udp_sk(sk)->udp_port_hash);
  		hslot2 = udp_hashslot2(udptable, udp_sk(sk)->udp_portaddr_hash);
  
  		spin_lock_bh(&hslot->lock);
  		if (sk_nulls_del_node_init_rcu(sk)) {
  			hslot->count--;
  			inet_sk(sk)->inet_num = 0;
  			sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
  
  			spin_lock(&hslot2->lock);
  			hlist_nulls_del_init_rcu(&udp_sk(sk)->udp_portaddr_node);
  			hslot2->count--;
  			spin_unlock(&hslot2->lock);
  		}
  		spin_unlock_bh(&hslot->lock);
  	}
  }
  EXPORT_SYMBOL(udp_lib_unhash);
  
  /*
   * inet_rcv_saddr was changed, we must rehash secondary hash
   */
  void udp_lib_rehash(struct sock *sk, u16 newhash)
  {
  	if (sk_hashed(sk)) {
  		struct udp_table *udptable = sk->sk_prot->h.udp_table;
  		struct udp_hslot *hslot, *hslot2, *nhslot2;
  
  		hslot2 = udp_hashslot2(udptable, udp_sk(sk)->udp_portaddr_hash);
  		nhslot2 = udp_hashslot2(udptable, newhash);
  		udp_sk(sk)->udp_portaddr_hash = newhash;
  		if (hslot2 != nhslot2) {
  			hslot = udp_hashslot(udptable, sock_net(sk),
  					     udp_sk(sk)->udp_port_hash);
  			/* we must lock primary chain too */
  			spin_lock_bh(&hslot->lock);
  
  			spin_lock(&hslot2->lock);
  			hlist_nulls_del_init_rcu(&udp_sk(sk)->udp_portaddr_node);
  			hslot2->count--;
  			spin_unlock(&hslot2->lock);
  
  			spin_lock(&nhslot2->lock);
  			hlist_nulls_add_head_rcu(&udp_sk(sk)->udp_portaddr_node,
  						 &nhslot2->head);
  			nhslot2->count++;
  			spin_unlock(&nhslot2->lock);
  
  			spin_unlock_bh(&hslot->lock);
  		}
  	}
  }
  EXPORT_SYMBOL(udp_lib_rehash);
  
  static void udp_v4_rehash(struct sock *sk)
  {
  	u16 new_hash = udp4_portaddr_hash(sock_net(sk),
  					  inet_sk(sk)->inet_rcv_saddr,
  					  inet_sk(sk)->inet_num);
  	udp_lib_rehash(sk, new_hash);
  }
  
  static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
  {
  	int rc;
  
  	if (inet_sk(sk)->inet_daddr)
  		sock_rps_save_rxhash(sk, skb->rxhash);
  
  	rc = ip_queue_rcv_skb(sk, skb);
  	if (rc < 0) {
  		int is_udplite = IS_UDPLITE(sk);
  
  		/* Note that an ENOMEM error is charged twice */
  		if (rc == -ENOMEM)
  			UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_RCVBUFERRORS,
  					 is_udplite);
  		UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
  		kfree_skb(skb);
  		return -1;
  	}
  
  	return 0;
  
  }
  
  /* 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;
  	int is_udplite = IS_UDPLITE(sk);
  
  	/*
  	 *	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 pass the skb to
  		 * the socket's udp_encap_rcv() hook. Otherwise, just
  		 * fall through and pass this up the UDP socket.
  		 * up->encap_rcv() returns the following value:
  		 * =0 if skb was successfully passed to the encap
  		 *    handler or was discarded by it.
  		 * >0 if skb should be passed on to UDP.
  		 * <0 if skb should be resubmitted as proto -N
  		 */
  
  		/* if we're overly short, let UDP handle it */
  		if (skb->len > sizeof(struct udphdr) &&
  		    up->encap_rcv != NULL) {
  			int ret;
  
  			ret = (*up->encap_rcv)(sk, skb);
  			if (ret <= 0) {
  				UDP_INC_STATS_BH(sock_net(sk),
  						 UDP_MIB_INDATAGRAMS,
  						 is_udplite);
  				return -ret;
  			}
  		}
  
  		/* FALLTHROUGH -- it's a UDP Packet */
  	}
  
  	/*
  	 * 	UDP-Lite specific tests, ignored on UDP sockets
  	 */
  	if ((is_udplite & 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 (rcu_dereference_raw(sk->sk_filter)) {
  		if (udp_lib_checksum_complete(skb))
  			goto drop;
  	}
  
  	if (sk_rcvqueues_full(sk, skb))
  		goto drop;
  
  	rc = 0;
  
  	bh_lock_sock(sk);
  	if (!sock_owned_by_user(sk))
  		rc = __udp_queue_rcv_skb(sk, skb);
  	else if (sk_add_backlog(sk, skb)) {
  		bh_unlock_sock(sk);
  		goto drop;
  	}
  	bh_unlock_sock(sk);
  
  	return rc;
  
  drop:
  	UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
  	atomic_inc(&sk->sk_drops);
  	kfree_skb(skb);
  	return -1;
  }
  
  static void flush_stack(struct sock **stack, unsigned int count,
  			struct sk_buff *skb, unsigned int final)
  {
  	unsigned int i;
  	struct sk_buff *skb1 = NULL;
  	struct sock *sk;
  
  	for (i = 0; i < count; i++) {
  		sk = stack[i];
  		if (likely(skb1 == NULL))
  			skb1 = (i == final) ? skb : skb_clone(skb, GFP_ATOMIC);
  
  		if (!skb1) {
  			atomic_inc(&sk->sk_drops);
  			UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_RCVBUFERRORS,
  					 IS_UDPLITE(sk));
  			UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_INERRORS,
  					 IS_UDPLITE(sk));
  		}
  
  		if (skb1 && udp_queue_rcv_skb(sk, skb1) <= 0)
  			skb1 = NULL;
  	}
  	if (unlikely(skb1))
  		kfree_skb(skb1);
  }
  
  /*
   *	Multicasts and broadcasts go to each listener.
   *
   *	Note: called only from the BH handler context.
   */
  static int __udp4_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
  				    struct udphdr  *uh,
  				    __be32 saddr, __be32 daddr,
  				    struct udp_table *udptable)
  {
  	struct sock *sk, *stack[256 / sizeof(struct sock *)];
  	struct udp_hslot *hslot = udp_hashslot(udptable, net, ntohs(uh->dest));
  	int dif;
  	unsigned int i, count = 0;
  
  	spin_lock(&hslot->lock);
  	sk = sk_nulls_head(&hslot->head);
  	dif = skb->dev->ifindex;
  	sk = udp_v4_mcast_next(net, sk, uh->dest, daddr, uh->source, saddr, dif);
  	while (sk) {
  		stack[count++] = sk;
  		sk = udp_v4_mcast_next(net, sk_nulls_next(sk), uh->dest,
  				       daddr, uh->source, saddr, dif);
  		if (unlikely(count == ARRAY_SIZE(stack))) {
  			if (!sk)
  				break;
  			flush_stack(stack, count, skb, ~0);
  			count = 0;
  		}
  	}
  	/*
  	 * before releasing chain lock, we must take a reference on sockets
  	 */
  	for (i = 0; i < count; i++)
  		sock_hold(stack[i]);
  
  	spin_unlock(&hslot->lock);
  
  	/*
  	 * do the slow work with no lock held
  	 */
  	if (count) {
  		flush_stack(stack, count, skb, count - 1);
  
  		for (i = 0; i < count; i++)
  			sock_put(stack[i]);
  	} else {
  		kfree_skb(skb);
  	}
  	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 udp_table *udptable,
  		   int proto)
  {
  	struct sock *sk;
  	struct udphdr *uh;
  	unsigned short ulen;
  	struct rtable *rt = skb_rtable(skb);
  	__be32 saddr, daddr;
  	struct net *net = dev_net(skb->dev);
  
  	/*
  	 *  Validate the packet.
  	 */
  	if (!pskb_may_pull(skb, sizeof(struct udphdr)))
  		goto drop;		/* No space for header. */
  
  	uh   = udp_hdr(skb);
  	ulen = ntohs(uh->len);
  	saddr = ip_hdr(skb)->saddr;
  	daddr = ip_hdr(skb)->daddr;
  
  	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(net, skb, uh,
  				saddr, daddr, udptable);
  
  	sk = __udp4_lib_lookup_skb(skb, uh->source, uh->dest, 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(net, 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 %pI4:%u %d/%d to %pI4:%u\n",
  		       proto == IPPROTO_UDPLITE ? "-Lite" : "",
  		       &saddr,
  		       ntohs(uh->source),
  		       ulen,
  		       skb->len,
  		       &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 %pI4:%u to %pI4:%u ulen %d\n",
  		       proto == IPPROTO_UDPLITE ? "-Lite" : "",
  		       &saddr,
  		       ntohs(uh->source),
  		       &daddr,
  		       ntohs(uh->dest),
  		       ulen);
  drop:
  	UDP_INC_STATS_BH(net, UDP_MIB_INERRORS, proto == IPPROTO_UDPLITE);
  	kfree_skb(skb);
  	return 0;
  }
  
  int udp_rcv(struct sk_buff *skb)
  {
  	return __udp4_lib_rcv(skb, &udp_table, IPPROTO_UDP);
  }
  
  void udp_destroy_sock(struct sock *sk)
  {
  	bool slow = lock_sock_fast(sk);
  	udp_flush_pending_frames(sk);
  	unlock_sock_fast(sk, slow);
  }
  
  /*
   *	Socket option code for UDP
   */
  int udp_lib_setsockopt(struct sock *sk, int level, int optname,
  		       char __user *optval, unsigned int optlen,
  		       int (*push_pending_frames)(struct sock *))
  {
  	struct udp_sock *up = udp_sk(sk);
  	int val;
  	int err = 0;
  	int is_udplite = IS_UDPLITE(sk);
  
  	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:
  			up->encap_rcv = xfrm4_udp_encap_rcv;
  			/* FALLTHROUGH */
  		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 (!is_udplite)         /* Disable the option on UDP sockets */
  			return -ENOPROTOOPT;
  		if (val != 0 && val < 8) /* Illegal coverage: use default (8) */
  			val = 8;
  		else if (val > USHRT_MAX)
  			val = USHRT_MAX;
  		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 (!is_udplite)         /* Disable the option on UDP sockets */
  			return -ENOPROTOOPT;
  		if (val != 0 && val < 8) /* Avoid silly minimal values.       */
  			val = 8;
  		else if (val > USHRT_MAX)
  			val = USHRT_MAX;
  		up->pcrlen = val;
  		up->pcflag |= UDPLITE_RECV_CC;
  		break;
  
  	default:
  		err = -ENOPROTOOPT;
  		break;
  	}
  
  	return err;
  }
  EXPORT_SYMBOL(udp_lib_setsockopt);
  
  int udp_setsockopt(struct sock *sk, int level, int optname,
  		   char __user *optval, unsigned 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, unsigned 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;
  }
  EXPORT_SYMBOL(udp_lib_getsockopt);
  
  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;
  
  	/* Check for false positives due to checksum errors */
  	if ((mask & POLLRDNORM) && !(file->f_flags & O_NONBLOCK) &&
  	    !(sk->sk_shutdown & RCV_SHUTDOWN) && !first_packet_length(sk))
  		mask &= ~(POLLIN | POLLRDNORM);
  
  	return mask;
  
  }
  EXPORT_SYMBOL(udp_poll);
  
  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,
  	.rehash		   = udp_v4_rehash,
  	.get_port	   = udp_v4_get_port,
  	.memory_allocated  = &udp_memory_allocated,
  	.sysctl_mem	   = sysctl_udp_mem,
  	.sysctl_wmem	   = &sysctl_udp_wmem_min,
  	.sysctl_rmem	   = &sysctl_udp_rmem_min,
  	.obj_size	   = sizeof(struct udp_sock),
  	.slab_flags	   = SLAB_DESTROY_BY_RCU,
  	.h.udp_table	   = &udp_table,
  #ifdef CONFIG_COMPAT
  	.compat_setsockopt = compat_udp_setsockopt,
  	.compat_getsockopt = compat_udp_getsockopt,
  #endif
  	.clear_sk	   = sk_prot_clear_portaddr_nulls,
  };
  EXPORT_SYMBOL(udp_prot);
  
  /* ------------------------------------------------------------------------ */
  #ifdef CONFIG_PROC_FS
  
  static struct sock *udp_get_first(struct seq_file *seq, int start)
  {
  	struct sock *sk;
  	struct udp_iter_state *state = seq->private;
  	struct net *net = seq_file_net(seq);
  
  	for (state->bucket = start; state->bucket <= state->udp_table->mask;
  	     ++state->bucket) {
  		struct hlist_nulls_node *node;
  		struct udp_hslot *hslot = &state->udp_table->hash[state->bucket];
  
  		if (hlist_nulls_empty(&hslot->head))
  			continue;
  
  		spin_lock_bh(&hslot->lock);
  		sk_nulls_for_each(sk, node, &hslot->head) {
  			if (!net_eq(sock_net(sk), net))
  				continue;
  			if (sk->sk_family == state->family)
  				goto found;
  		}
  		spin_unlock_bh(&hslot->lock);
  	}
  	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;
  	struct net *net = seq_file_net(seq);
  
  	do {
  		sk = sk_nulls_next(sk);
  	} while (sk && (!net_eq(sock_net(sk), net) || sk->sk_family != state->family));
  
  	if (!sk) {
  		if (state->bucket <= state->udp_table->mask)
  			spin_unlock_bh(&state->udp_table->hash[state->bucket].lock);
  		return udp_get_first(seq, state->bucket + 1);
  	}
  	return sk;
  }
  
  static struct sock *udp_get_idx(struct seq_file *seq, loff_t pos)
  {
  	struct sock *sk = udp_get_first(seq, 0);
  
  	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)
  {
  	struct udp_iter_state *state = seq->private;
  	state->bucket = MAX_UDP_PORTS;
  
  	return *pos ? udp_get_idx(seq, *pos-1) : SEQ_START_TOKEN;
  }
  
  static void *udp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  {
  	struct sock *sk;
  
  	if (v == SEQ_START_TOKEN)
  		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)
  {
  	struct udp_iter_state *state = seq->private;
  
  	if (state->bucket <= state->udp_table->mask)
  		spin_unlock_bh(&state->udp_table->hash[state->bucket].lock);
  }
  
  static int udp_seq_open(struct inode *inode, struct file *file)
  {
  	struct udp_seq_afinfo *afinfo = PDE(inode)->data;
  	struct udp_iter_state *s;
  	int err;
  
  	err = seq_open_net(inode, file, &afinfo->seq_ops,
  			   sizeof(struct udp_iter_state));
  	if (err < 0)
  		return err;
  
  	s = ((struct seq_file *)file->private_data)->private;
  	s->family		= afinfo->family;
  	s->udp_table		= afinfo->udp_table;
  	return err;
  }
  
  /* ------------------------------------------------------------------------ */
  int udp_proc_register(struct net *net, struct udp_seq_afinfo *afinfo)
  {
  	struct proc_dir_entry *p;
  	int rc = 0;
  
  	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_net;
  
  	afinfo->seq_ops.start		= udp_seq_start;
  	afinfo->seq_ops.next		= udp_seq_next;
  	afinfo->seq_ops.stop		= udp_seq_stop;
  
  	p = proc_create_data(afinfo->name, S_IRUGO, net->proc_net,
  			     &afinfo->seq_fops, afinfo);
  	if (!p)
  		rc = -ENOMEM;
  	return rc;
  }
  EXPORT_SYMBOL(udp_proc_register);
  
  void udp_proc_unregister(struct net *net, struct udp_seq_afinfo *afinfo)
  {
  	proc_net_remove(net, afinfo->name);
  }
  EXPORT_SYMBOL(udp_proc_unregister);
  
  /* ------------------------------------------------------------------------ */
  static void udp4_format_sock(struct sock *sp, struct seq_file *f,
  		int bucket, int *len)
  {
  	struct inet_sock *inet = inet_sk(sp);
  	__be32 dest = inet->inet_daddr;
  	__be32 src  = inet->inet_rcv_saddr;
  	__u16 destp	  = ntohs(inet->inet_dport);
  	__u16 srcp	  = ntohs(inet->inet_sport);
  
  	seq_printf(f, "%5d: %08X:%04X %08X:%04X"
  		" %02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %pK %d%n",
  		bucket, src, srcp, dest, destp, sp->sk_state,
  		sk_wmem_alloc_get(sp),
  		sk_rmem_alloc_get(sp),
  		0, 0L, 0, sock_i_uid(sp), 0, sock_i_ino(sp),
  		atomic_read(&sp->sk_refcnt), sp,
  		atomic_read(&sp->sk_drops), len);
  }
  
  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 ref pointer drops");
  	else {
  		struct udp_iter_state *state = seq->private;
  		int len;
  
  		udp4_format_sock(v, seq, state->bucket, &len);
  		seq_printf(seq, "%*s\n", 127 - len, "");
  	}
  	return 0;
  }
  
  /* ------------------------------------------------------------------------ */
  static struct udp_seq_afinfo udp4_seq_afinfo = {
  	.name		= "udp",
  	.family		= AF_INET,
  	.udp_table	= &udp_table,
  	.seq_fops	= {
  		.owner	=	THIS_MODULE,
  	},
  	.seq_ops	= {
  		.show		= udp4_seq_show,
  	},
  };
  
  static int __net_init udp4_proc_init_net(struct net *net)
  {
  	return udp_proc_register(net, &udp4_seq_afinfo);
  }
  
  static void __net_exit udp4_proc_exit_net(struct net *net)
  {
  	udp_proc_unregister(net, &udp4_seq_afinfo);
  }
  
  static struct pernet_operations udp4_net_ops = {
  	.init = udp4_proc_init_net,
  	.exit = udp4_proc_exit_net,
  };
  
  int __init udp4_proc_init(void)
  {
  	return register_pernet_subsys(&udp4_net_ops);
  }
  
  void udp4_proc_exit(void)
  {
  	unregister_pernet_subsys(&udp4_net_ops);
  }
  #endif /* CONFIG_PROC_FS */
  
  static __initdata unsigned long uhash_entries;
  static int __init set_uhash_entries(char *str)
  {
  	if (!str)
  		return 0;
  	uhash_entries = simple_strtoul(str, &str, 0);
  	if (uhash_entries && uhash_entries < UDP_HTABLE_SIZE_MIN)
  		uhash_entries = UDP_HTABLE_SIZE_MIN;
  	return 1;
  }
  __setup("uhash_entries=", set_uhash_entries);
  
  void __init udp_table_init(struct udp_table *table, const char *name)
  {
  	unsigned int i;
  
  	if (!CONFIG_BASE_SMALL)
  		table->hash = alloc_large_system_hash(name,
  			2 * sizeof(struct udp_hslot),
  			uhash_entries,
  			21, /* one slot per 2 MB */
  			0,
  			&table->log,
  			&table->mask,
  			64 * 1024);
  	/*
  	 * Make sure hash table has the minimum size
  	 */
  	if (CONFIG_BASE_SMALL || table->mask < UDP_HTABLE_SIZE_MIN - 1) {
  		table->hash = kmalloc(UDP_HTABLE_SIZE_MIN *
  				      2 * sizeof(struct udp_hslot), GFP_KERNEL);
  		if (!table->hash)
  			panic(name);
  		table->log = ilog2(UDP_HTABLE_SIZE_MIN);
  		table->mask = UDP_HTABLE_SIZE_MIN - 1;
  	}
  	table->hash2 = table->hash + (table->mask + 1);
  	for (i = 0; i <= table->mask; i++) {
  		INIT_HLIST_NULLS_HEAD(&table->hash[i].head, i);
  		table->hash[i].count = 0;
  		spin_lock_init(&table->hash[i].lock);
  	}
  	for (i = 0; i <= table->mask; i++) {
  		INIT_HLIST_NULLS_HEAD(&table->hash2[i].head, i);
  		table->hash2[i].count = 0;
  		spin_lock_init(&table->hash2[i].lock);
  	}
  }
  
  void __init udp_init(void)
  {
  	unsigned long limit;
  
  	udp_table_init(&udp_table, "UDP");
  	limit = nr_free_buffer_pages() / 8;
  	limit = max(limit, 128UL);
  	sysctl_udp_mem[0] = limit / 4 * 3;
  	sysctl_udp_mem[1] = limit;
  	sysctl_udp_mem[2] = sysctl_udp_mem[0] * 2;
  
  	sysctl_udp_rmem_min = SK_MEM_QUANTUM;
  	sysctl_udp_wmem_min = SK_MEM_QUANTUM;
  }
  
  int udp4_ufo_send_check(struct sk_buff *skb)
  {
  	const struct iphdr *iph;
  	struct udphdr *uh;
  
  	if (!pskb_may_pull(skb, sizeof(*uh)))
  		return -EINVAL;
  
  	iph = ip_hdr(skb);
  	uh = udp_hdr(skb);
  
  	uh->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, skb->len,
  				       IPPROTO_UDP, 0);
  	skb->csum_start = skb_transport_header(skb) - skb->head;
  	skb->csum_offset = offsetof(struct udphdr, check);
  	skb->ip_summed = CHECKSUM_PARTIAL;
  	return 0;
  }
  
  struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb, u32 features)
  {
  	struct sk_buff *segs = ERR_PTR(-EINVAL);
  	unsigned int mss;
  	int offset;
  	__wsum csum;
  
  	mss = skb_shinfo(skb)->gso_size;
  	if (unlikely(skb->len <= mss))
  		goto out;
  
  	if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
  		/* Packet is from an untrusted source, reset gso_segs. */
  		int type = skb_shinfo(skb)->gso_type;
  
  		if (unlikely(type & ~(SKB_GSO_UDP | SKB_GSO_DODGY) ||
  			     !(type & (SKB_GSO_UDP))))
  			goto out;
  
  		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
  
  		segs = NULL;
  		goto out;
  	}
  
  	/* Do software UFO. Complete and fill in the UDP checksum as HW cannot
  	 * do checksum of UDP packets sent as multiple IP fragments.
  	 */
  	offset = skb_checksum_start_offset(skb);
  	csum = skb_checksum(skb, offset, skb->len - offset, 0);
  	offset += skb->csum_offset;
  	*(__sum16 *)(skb->data + offset) = csum_fold(csum);
  	skb->ip_summed = CHECKSUM_NONE;
  
  	/* Fragment the skb. IP headers of the fragments are updated in
  	 * inet_gso_segment()
  	 */
  	segs = skb_segment(skb, features);
  out:
  	return segs;
  }
  