text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * 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.
   */
  
  #define pr_fmt(fmt) "UDP: " fmt
  
  #include <linux/uaccess.h>
  #include <asm/ioctls.h>
  #include <linux/memblock.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/inetdevice.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/inet_hashtables.h>
  #include <net/ip_tunnels.h>
  #include <net/route.h>
  #include <net/checksum.h>
  #include <net/xfrm.h>
  #include <trace/events/udp.h>
  #include <linux/static_key.h>
  #include <trace/events/skb.h>
  #include <net/busy_poll.h>
  #include "udp_impl.h"
  #include <net/sock_reuseport.h>
  #include <net/addrconf.h>
  #include <net/udp_tunnel.h>
  
  struct udp_table udp_table __read_mostly;
  EXPORT_SYMBOL(udp_table);
  
  long sysctl_udp_mem[3] __read_mostly;
  EXPORT_SYMBOL(sysctl_udp_mem);
  
  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, unsigned int log)
  {
  	struct sock *sk2;
  	kuid_t uid = sock_i_uid(sk);
  
  	sk_for_each(sk2, &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) &&
  		    inet_rcv_saddr_equal(sk, sk2, true)) {
  			if (sk2->sk_reuseport && sk->sk_reuseport &&
  			    !rcu_access_pointer(sk->sk_reuseport_cb) &&
  			    uid_eq(uid, sock_i_uid(sk2))) {
  				if (!bitmap)
  					return 0;
  			} else {
  				if (!bitmap)
  					return 1;
  				__set_bit(udp_sk(sk2)->udp_port_hash >> log,
  					  bitmap);
  			}
  		}
  	}
  	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)
  {
  	struct sock *sk2;
  	kuid_t uid = sock_i_uid(sk);
  	int res = 0;
  
  	spin_lock(&hslot2->lock);
  	udp_portaddr_for_each_entry(sk2, &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) &&
  		    inet_rcv_saddr_equal(sk, sk2, true)) {
  			if (sk2->sk_reuseport && sk->sk_reuseport &&
  			    !rcu_access_pointer(sk->sk_reuseport_cb) &&
  			    uid_eq(uid, sock_i_uid(sk2))) {
  				res = 0;
  			} else {
  				res = 1;
  			}
  			break;
  		}
  	}
  	spin_unlock(&hslot2->lock);
  	return res;
  }
  
  static int udp_reuseport_add_sock(struct sock *sk, struct udp_hslot *hslot)
  {
  	struct net *net = sock_net(sk);
  	kuid_t uid = sock_i_uid(sk);
  	struct sock *sk2;
  
  	sk_for_each(sk2, &hslot->head) {
  		if (net_eq(sock_net(sk2), net) &&
  		    sk2 != sk &&
  		    sk2->sk_family == sk->sk_family &&
  		    ipv6_only_sock(sk2) == ipv6_only_sock(sk) &&
  		    (udp_sk(sk2)->udp_port_hash == udp_sk(sk)->udp_port_hash) &&
  		    (sk2->sk_bound_dev_if == sk->sk_bound_dev_if) &&
  		    sk2->sk_reuseport && uid_eq(uid, sock_i_uid(sk2)) &&
  		    inet_rcv_saddr_equal(sk, sk2, false)) {
  			return reuseport_add_sock(sk, sk2,
  						  inet_rcv_saddr_any(sk));
  		}
  	}
  
  	return reuseport_alloc(sk, inet_rcv_saddr_any(sk));
  }
  
  /**
   *  udp_lib_get_port  -  UDP/-Lite port lookup for IPv4 and IPv6
   *
   *  @sk:          socket struct in question
   *  @snum:        port number to look up
   *  @hash2_nulladdr: AF-dependent hash value in secondary hash chains,
   *                   with NULL address
   */
  int udp_lib_get_port(struct sock *sk, unsigned short snum,
  		     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 int rand;
  		unsigned short first, last;
  		DECLARE_BITMAP(bitmap, PORTS_PER_CHAIN);
  
  		inet_get_local_port_range(net, &low, &high);
  		remaining = (high - low) + 1;
  
  		rand = prandom_u32();
  		first = reciprocal_scale(rand, remaining) + 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,
  					    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_local_reserved_port(net, snum))
  					goto found;
  				snum += rand;
  			} while (snum != first);
  			spin_unlock_bh(&hslot->lock);
  			cond_resched();
  		} 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);
  			if (!exist && (hash2_nulladdr != slot2)) {
  				hslot2 = udp_hashslot2(udptable, hash2_nulladdr);
  				exist = udp_lib_lport_inuse2(net, snum, hslot2,
  							     sk);
  			}
  			if (exist)
  				goto fail_unlock;
  			else
  				goto found;
  		}
  scan_primary_hash:
  		if (udp_lib_lport_inuse(net, snum, hslot, NULL, sk, 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)) {
  		if (sk->sk_reuseport &&
  		    udp_reuseport_add_sock(sk, hslot)) {
  			inet_sk(sk)->inet_num = 0;
  			udp_sk(sk)->udp_port_hash = 0;
  			udp_sk(sk)->udp_portaddr_hash ^= snum;
  			goto fail_unlock;
  		}
  
  		sk_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);
  		if (IS_ENABLED(CONFIG_IPV6) && sk->sk_reuseport &&
  		    sk->sk_family == AF_INET6)
  			hlist_add_tail_rcu(&udp_sk(sk)->udp_portaddr_node,
  					   &hslot2->head);
  		else
  			hlist_add_head_rcu(&udp_sk(sk)->udp_portaddr_node,
  					   &hslot2->head);
  		hslot2->count++;
  		spin_unlock(&hslot2->lock);
  	}
  	sock_set_flag(sk, SOCK_RCU_FREE);
  	error = 0;
  fail_unlock:
  	spin_unlock_bh(&hslot->lock);
  fail:
  	return error;
  }
  EXPORT_SYMBOL(udp_lib_get_port);
  
  int udp_v4_get_port(struct sock *sk, unsigned short snum)
  {
  	unsigned int hash2_nulladdr =
  		ipv4_portaddr_hash(sock_net(sk), htonl(INADDR_ANY), snum);
  	unsigned int hash2_partial =
  		ipv4_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, hash2_nulladdr);
  }
  
  static int compute_score(struct sock *sk, struct net *net,
  			 __be32 saddr, __be16 sport,
  			 __be32 daddr, unsigned short hnum,
  			 int dif, int sdif)
  {
  	int score;
  	struct inet_sock *inet;
  	bool dev_match;
  
  	if (!net_eq(sock_net(sk), net) ||
  	    udp_sk(sk)->udp_port_hash != hnum ||
  	    ipv6_only_sock(sk))
  		return -1;
  
  	if (sk->sk_rcv_saddr != daddr)
  		return -1;
  
  	score = (sk->sk_family == PF_INET) ? 2 : 1;
  
  	inet = inet_sk(sk);
  	if (inet->inet_daddr) {
  		if (inet->inet_daddr != saddr)
  			return -1;
  		score += 4;
  	}
  
  	if (inet->inet_dport) {
  		if (inet->inet_dport != sport)
  			return -1;
  		score += 4;
  	}
  
  	dev_match = udp_sk_bound_dev_eq(net, sk->sk_bound_dev_if,
  					dif, sdif);
  	if (!dev_match)
  		return -1;
  	score += 4;
  
  	if (READ_ONCE(sk->sk_incoming_cpu) == raw_smp_processor_id())
  		score++;
  	return score;
  }
  
  static u32 udp_ehashfn(const struct net *net, const __be32 laddr,
  		       const __u16 lport, const __be32 faddr,
  		       const __be16 fport)
  {
  	static u32 udp_ehash_secret __read_mostly;
  
  	net_get_random_once(&udp_ehash_secret, sizeof(udp_ehash_secret));
  
  	return __inet_ehashfn(laddr, lport, faddr, fport,
  			      udp_ehash_secret + net_hash_mix(net));
  }
  
  /* called with rcu_read_lock() */
  static struct sock *udp4_lib_lookup2(struct net *net,
  				     __be32 saddr, __be16 sport,
  				     __be32 daddr, unsigned int hnum,
  				     int dif, int sdif,
  				     struct udp_hslot *hslot2,
  				     struct sk_buff *skb)
  {
  	struct sock *sk, *result;
  	int score, badness;
  	u32 hash = 0;
  
  	result = NULL;
  	badness = 0;
  	udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
  		score = compute_score(sk, net, saddr, sport,
  				      daddr, hnum, dif, sdif);
  		if (score > badness) {
  			if (sk->sk_reuseport &&
  			    sk->sk_state != TCP_ESTABLISHED) {
  				hash = udp_ehashfn(net, daddr, hnum,
  						   saddr, sport);
  				result = reuseport_select_sock(sk, hash, skb,
  							sizeof(struct udphdr));
  				if (result && !reuseport_has_conns(sk, false))
  					return result;
  			}
  			badness = score;
  			result = sk;
  		}
  	}
  	return result;
  }
  
  /* UDP is nearly always wildcards out the wazoo, it makes no sense to try
   * harder than this. -DaveM
   */
  struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
  		__be16 sport, __be32 daddr, __be16 dport, int dif,
  		int sdif, struct udp_table *udptable, struct sk_buff *skb)
  {
  	struct sock *result;
  	unsigned short hnum = ntohs(dport);
  	unsigned int hash2, slot2;
  	struct udp_hslot *hslot2;
  
  	hash2 = ipv4_portaddr_hash(net, daddr, hnum);
  	slot2 = hash2 & udptable->mask;
  	hslot2 = &udptable->hash2[slot2];
  
  	result = udp4_lib_lookup2(net, saddr, sport,
  				  daddr, hnum, dif, sdif,
  				  hslot2, skb);
  	if (!result) {
  		hash2 = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
  		slot2 = hash2 & udptable->mask;
  		hslot2 = &udptable->hash2[slot2];
  
  		result = udp4_lib_lookup2(net, saddr, sport,
  					  htonl(INADDR_ANY), hnum, dif, sdif,
  					  hslot2, skb);
  	}
  	if (IS_ERR(result))
  		return NULL;
  	return result;
  }
  EXPORT_SYMBOL_GPL(__udp4_lib_lookup);
  
  static inline struct sock *__udp4_lib_lookup_skb(struct sk_buff *skb,
  						 __be16 sport, __be16 dport,
  						 struct udp_table *udptable)
  {
  	const struct iphdr *iph = ip_hdr(skb);
  
  	return __udp4_lib_lookup(dev_net(skb->dev), iph->saddr, sport,
  				 iph->daddr, dport, inet_iif(skb),
  				 inet_sdif(skb), udptable, skb);
  }
  
  struct sock *udp4_lib_lookup_skb(struct sk_buff *skb,
  				 __be16 sport, __be16 dport)
  {
  	const struct iphdr *iph = ip_hdr(skb);
  
  	return __udp4_lib_lookup(dev_net(skb->dev), iph->saddr, sport,
  				 iph->daddr, dport, inet_iif(skb),
  				 inet_sdif(skb), &udp_table, NULL);
  }
  EXPORT_SYMBOL_GPL(udp4_lib_lookup_skb);
  
  /* Must be called under rcu_read_lock().
   * Does increment socket refcount.
   */
  #if IS_ENABLED(CONFIG_NF_TPROXY_IPV4) || IS_ENABLED(CONFIG_NF_SOCKET_IPV4)
  struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
  			     __be32 daddr, __be16 dport, int dif)
  {
  	struct sock *sk;
  
  	sk = __udp4_lib_lookup(net, saddr, sport, daddr, dport,
  			       dif, 0, &udp_table, NULL);
  	if (sk && !refcount_inc_not_zero(&sk->sk_refcnt))
  		sk = NULL;
  	return sk;
  }
  EXPORT_SYMBOL_GPL(udp4_lib_lookup);
  #endif
  
  static inline bool __udp_is_mcast_sock(struct net *net, struct sock *sk,
  				       __be16 loc_port, __be32 loc_addr,
  				       __be16 rmt_port, __be32 rmt_addr,
  				       int dif, int sdif, unsigned short hnum)
  {
  	struct inet_sock *inet = inet_sk(sk);
  
  	if (!net_eq(sock_net(sk), net) ||
  	    udp_sk(sk)->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(sk) ||
  	    !udp_sk_bound_dev_eq(net, sk->sk_bound_dev_if, dif, sdif))
  		return false;
  	if (!ip_mc_sf_allow(sk, loc_addr, rmt_addr, dif, sdif))
  		return false;
  	return true;
  }
  
  DEFINE_STATIC_KEY_FALSE(udp_encap_needed_key);
  void udp_encap_enable(void)
  {
  	static_branch_inc(&udp_encap_needed_key);
  }
  EXPORT_SYMBOL(udp_encap_enable);
  
  /* Handler for tunnels with arbitrary destination ports: no socket lookup, go
   * through error handlers in encapsulations looking for a match.
   */
  static int __udp4_lib_err_encap_no_sk(struct sk_buff *skb, u32 info)
  {
  	int i;
  
  	for (i = 0; i < MAX_IPTUN_ENCAP_OPS; i++) {
  		int (*handler)(struct sk_buff *skb, u32 info);
  		const struct ip_tunnel_encap_ops *encap;
  
  		encap = rcu_dereference(iptun_encaps[i]);
  		if (!encap)
  			continue;
  		handler = encap->err_handler;
  		if (handler && !handler(skb, info))
  			return 0;
  	}
  
  	return -ENOENT;
  }
  
  /* Try to match ICMP errors to UDP tunnels by looking up a socket without
   * reversing source and destination port: this will match tunnels that force the
   * same destination port on both endpoints (e.g. VXLAN, GENEVE). Note that
   * lwtunnels might actually break this assumption by being configured with
   * different destination ports on endpoints, in this case we won't be able to
   * trace ICMP messages back to them.
   *
   * If this doesn't match any socket, probe tunnels with arbitrary destination
   * ports (e.g. FoU, GUE): there, the receiving socket is useless, as the port
   * we've sent packets to won't necessarily match the local destination port.
   *
   * Then ask the tunnel implementation to match the error against a valid
   * association.
   *
   * Return an error if we can't find a match, the socket if we need further
   * processing, zero otherwise.
   */
  static struct sock *__udp4_lib_err_encap(struct net *net,
  					 const struct iphdr *iph,
  					 struct udphdr *uh,
  					 struct udp_table *udptable,
  					 struct sk_buff *skb, u32 info)
  {
  	int network_offset, transport_offset;
  	struct sock *sk;
  
  	network_offset = skb_network_offset(skb);
  	transport_offset = skb_transport_offset(skb);
  
  	/* Network header needs to point to the outer IPv4 header inside ICMP */
  	skb_reset_network_header(skb);
  
  	/* Transport header needs to point to the UDP header */
  	skb_set_transport_header(skb, iph->ihl << 2);
  
  	sk = __udp4_lib_lookup(net, iph->daddr, uh->source,
  			       iph->saddr, uh->dest, skb->dev->ifindex, 0,
  			       udptable, NULL);
  	if (sk) {
  		int (*lookup)(struct sock *sk, struct sk_buff *skb);
  		struct udp_sock *up = udp_sk(sk);
  
  		lookup = READ_ONCE(up->encap_err_lookup);
  		if (!lookup || lookup(sk, skb))
  			sk = NULL;
  	}
  
  	if (!sk)
  		sk = ERR_PTR(__udp4_lib_err_encap_no_sk(skb, info));
  
  	skb_set_transport_header(skb, transport_offset);
  	skb_set_network_header(skb, network_offset);
  
  	return sk;
  }
  
  /*
   * 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.
   */
  
  int __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;
  	bool tunnel = false;
  	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,
  			       inet_sdif(skb), udptable, NULL);
  	if (!sk) {
  		/* No socket for error: try tunnels before discarding */
  		sk = ERR_PTR(-ENOENT);
  		if (static_branch_unlikely(&udp_encap_needed_key)) {
  			sk = __udp4_lib_err_encap(net, iph, uh, udptable, skb,
  						  info);
  			if (!sk)
  				return 0;
  		}
  
  		if (IS_ERR(sk)) {
  			__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
  			return PTR_ERR(sk);
  		}
  
  		tunnel = true;
  	}
  
  	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 */
  			ipv4_sk_update_pmtu(skb, sk, info);
  			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;
  	case ICMP_REDIRECT:
  		ipv4_sk_redirect(skb, sk);
  		goto out;
  	}
  
  	/*
  	 *      RFC1122: OK.  Passes ICMP errors back to application, as per
  	 *	4.1.3.3.
  	 */
  	if (tunnel) {
  		/* ...not for tunnels though: we don't have a sending socket */
  		goto out;
  	}
  	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:
  	return 0;
  }
  
  int udp_err(struct sk_buff *skb, u32 info)
  {
  	return __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
   */
  void udp4_hwcsum(struct sk_buff *skb, __be32 src, __be32 dst)
  {
  	struct udphdr *uh = udp_hdr(skb);
  	int offset = skb_transport_offset(skb);
  	int len = skb->len - offset;
  	int hlen = len;
  	__wsum csum = 0;
  
  	if (!skb_has_frag_list(skb)) {
  		/*
  		 * 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 {
  		struct sk_buff *frags;
  
  		/*
  		 * 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
  		 */
  		skb_walk_frags(skb, frags) {
  			csum = csum_add(csum, frags->csum);
  			hlen -= frags->len;
  		}
  
  		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;
  	}
  }
  EXPORT_SYMBOL_GPL(udp4_hwcsum);
  
  /* Function to set UDP checksum for an IPv4 UDP packet. This is intended
   * for the simple case like when setting the checksum for a UDP tunnel.
   */
  void udp_set_csum(bool nocheck, struct sk_buff *skb,
  		  __be32 saddr, __be32 daddr, int len)
  {
  	struct udphdr *uh = udp_hdr(skb);
  
  	if (nocheck) {
  		uh->check = 0;
  	} else if (skb_is_gso(skb)) {
  		uh->check = ~udp_v4_check(len, saddr, daddr, 0);
  	} else if (skb->ip_summed == CHECKSUM_PARTIAL) {
  		uh->check = 0;
  		uh->check = udp_v4_check(len, saddr, daddr, lco_csum(skb));
  		if (uh->check == 0)
  			uh->check = CSUM_MANGLED_0;
  	} else {
  		skb->ip_summed = CHECKSUM_PARTIAL;
  		skb->csum_start = skb_transport_header(skb) - skb->head;
  		skb->csum_offset = offsetof(struct udphdr, check);
  		uh->check = ~udp_v4_check(len, saddr, daddr, 0);
  	}
  }
  EXPORT_SYMBOL(udp_set_csum);
  
  static int udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4,
  			struct inet_cork *cork)
  {
  	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;
  	int datalen = len - sizeof(*uh);
  	__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 (cork->gso_size) {
  		const int hlen = skb_network_header_len(skb) +
  				 sizeof(struct udphdr);
  
  		if (hlen + cork->gso_size > cork->fragsize) {
  			kfree_skb(skb);
  			return -EINVAL;
  		}
  		if (skb->len > cork->gso_size * UDP_MAX_SEGMENTS) {
  			kfree_skb(skb);
  			return -EINVAL;
  		}
  		if (sk->sk_no_check_tx) {
  			kfree_skb(skb);
  			return -EINVAL;
  		}
  		if (skb->ip_summed != CHECKSUM_PARTIAL || is_udplite ||
  		    dst_xfrm(skb_dst(skb))) {
  			kfree_skb(skb);
  			return -EIO;
  		}
  
  		if (datalen > cork->gso_size) {
  			skb_shinfo(skb)->gso_size = cork->gso_size;
  			skb_shinfo(skb)->gso_type = SKB_GSO_UDP_L4;
  			skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(datalen,
  								 cork->gso_size);
  		}
  		goto csum_partial;
  	}
  
  	if (is_udplite)  				 /*     UDP-Lite      */
  		csum = udplite_csum(skb);
  
  	else if (sk->sk_no_check_tx) {			 /* UDP csum off */
  
  		skb->ip_summed = CHECKSUM_NONE;
  		goto send;
  
  	} else if (skb->ip_summed == CHECKSUM_PARTIAL) { /* UDP hardware csum */
  csum_partial:
  
  		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(sock_net(sk), skb);
  	if (err) {
  		if (err == -ENOBUFS && !inet->recverr) {
  			UDP_INC_STATS(sock_net(sk),
  				      UDP_MIB_SNDBUFERRORS, is_udplite);
  			err = 0;
  		}
  	} else
  		UDP_INC_STATS(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, &inet->cork.base);
  
  out:
  	up->len = 0;
  	up->pending = 0;
  	return err;
  }
  EXPORT_SYMBOL(udp_push_pending_frames);
  
  static int __udp_cmsg_send(struct cmsghdr *cmsg, u16 *gso_size)
  {
  	switch (cmsg->cmsg_type) {
  	case UDP_SEGMENT:
  		if (cmsg->cmsg_len != CMSG_LEN(sizeof(__u16)))
  			return -EINVAL;
  		*gso_size = *(__u16 *)CMSG_DATA(cmsg);
  		return 0;
  	default:
  		return -EINVAL;
  	}
  }
  
  int udp_cmsg_send(struct sock *sk, struct msghdr *msg, u16 *gso_size)
  {
  	struct cmsghdr *cmsg;
  	bool need_ip = false;
  	int err;
  
  	for_each_cmsghdr(cmsg, msg) {
  		if (!CMSG_OK(msg, cmsg))
  			return -EINVAL;
  
  		if (cmsg->cmsg_level != SOL_UDP) {
  			need_ip = true;
  			continue;
  		}
  
  		err = __udp_cmsg_send(cmsg, gso_size);
  		if (err)
  			return err;
  	}
  
  	return need_ip;
  }
  EXPORT_SYMBOL_GPL(udp_cmsg_send);
  
  int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
  {
  	struct inet_sock *inet = inet_sk(sk);
  	struct udp_sock *up = udp_sk(sk);
  	DECLARE_SOCKADDR(struct sockaddr_in *, usin, msg->msg_name);
  	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;
  
  	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 (usin) {
  		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;
  	}
  
  	ipcm_init_sk(&ipc, inet);
  	ipc.gso_size = up->gso_size;
  
  	if (msg->msg_controllen) {
  		err = udp_cmsg_send(sk, msg, &ipc.gso_size);
  		if (err > 0)
  			err = ip_cmsg_send(sk, msg, &ipc,
  					   sk->sk_family == AF_INET6);
  		if (unlikely(err < 0)) {
  			kfree(ipc.opt);
  			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();
  	}
  
  	if (cgroup_bpf_enabled && !connected) {
  		err = BPF_CGROUP_RUN_PROG_UDP4_SENDMSG_LOCK(sk,
  					    (struct sockaddr *)usin, &ipc.addr);
  		if (err)
  			goto out_free;
  		if (usin) {
  			if (usin->sin_port == 0) {
  				/* BPF program set invalid port. Reject it. */
  				err = -EINVAL;
  				goto out_free;
  			}
  			daddr = usin->sin_addr.s_addr;
  			dport = usin->sin_port;
  		}
  	}
  
  	saddr = ipc.addr;
  	ipc.addr = faddr = daddr;
  
  	if (ipc.opt && ipc.opt->opt.srr) {
  		if (!daddr) {
  			err = -EINVAL;
  			goto out_free;
  		}
  		faddr = ipc.opt->opt.faddr;
  		connected = 0;
  	}
  	tos = get_rttos(&ipc, inet);
  	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 || netif_index_is_l3_master(sock_net(sk), ipc.oif))
  			ipc.oif = inet->mc_index;
  		if (!saddr)
  			saddr = inet->mc_addr;
  		connected = 0;
  	} else if (!ipc.oif) {
  		ipc.oif = inet->uc_index;
  	} else if (ipv4_is_lbcast(daddr) && inet->uc_index) {
  		/* oif is set, packet is to local broadcast and
  		 * and uc_index is set. oif is most likely set
  		 * by sk_bound_dev_if. If uc_index != oif check if the
  		 * oif is an L3 master and uc_index is an L3 slave.
  		 * If so, we want to allow the send using the uc_index.
  		 */
  		if (ipc.oif != inet->uc_index &&
  		    ipc.oif == l3mdev_master_ifindex_by_index(sock_net(sk),
  							      inet->uc_index)) {
  			ipc.oif = inet->uc_index;
  		}
  	}
  
  	if (connected)
  		rt = (struct rtable *)sk_dst_check(sk, 0);
  
  	if (!rt) {
  		struct net *net = sock_net(sk);
  		__u8 flow_flags = inet_sk_flowi_flags(sk);
  
  		fl4 = &fl4_stack;
  
  		flowi4_init_output(fl4, ipc.oif, ipc.sockc.mark, tos,
  				   RT_SCOPE_UNIVERSE, sk->sk_protocol,
  				   flow_flags,
  				   faddr, saddr, dport, inet->inet_sport,
  				   sk->sk_uid);
  
  		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(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) {
  		struct inet_cork cork;
  
  		skb = ip_make_skb(sk, fl4, getfrag, msg, ulen,
  				  sizeof(struct udphdr), &ipc, &rt,
  				  &cork, msg->msg_flags);
  		err = PTR_ERR(skb);
  		if (!IS_ERR_OR_NULL(skb))
  			err = udp_send_skb(skb, fl4, &cork);
  		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);
  
  		net_dbg_ratelimited("socket already corked\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, 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);
  out_free:
  	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(sock_net(sk),
  			      UDP_MIB_SNDBUFERRORS, is_udplite);
  	}
  	return err;
  
  do_confirm:
  	if (msg->msg_flags & MSG_PROBE)
  		dst_confirm_neigh(&rt->dst, &fl4->daddr);
  	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 (flags & MSG_SENDPAGE_NOTLAST)
  		flags |= MSG_MORE;
  
  	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(sk, &msg, 0);
  		if (ret < 0)
  			return ret;
  	}
  
  	lock_sock(sk);
  
  	if (unlikely(!up->pending)) {
  		release_sock(sk);
  
  		net_dbg_ratelimited("cork failed\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;
  }
  
  #define UDP_SKB_IS_STATELESS 0x80000000
  
  /* all head states (dst, sk, nf conntrack) except skb extensions are
   * cleared by udp_rcv().
   *
   * We need to preserve secpath, if present, to eventually process
   * IP_CMSG_PASSSEC at recvmsg() time.
   *
   * Other extensions can be cleared.
   */
  static bool udp_try_make_stateless(struct sk_buff *skb)
  {
  	if (!skb_has_extensions(skb))
  		return true;
  
  	if (!secpath_exists(skb)) {
  		skb_ext_reset(skb);
  		return true;
  	}
  
  	return false;
  }
  
  static void udp_set_dev_scratch(struct sk_buff *skb)
  {
  	struct udp_dev_scratch *scratch = udp_skb_scratch(skb);
  
  	BUILD_BUG_ON(sizeof(struct udp_dev_scratch) > sizeof(long));
  	scratch->_tsize_state = skb->truesize;
  #if BITS_PER_LONG == 64
  	scratch->len = skb->len;
  	scratch->csum_unnecessary = !!skb_csum_unnecessary(skb);
  	scratch->is_linear = !skb_is_nonlinear(skb);
  #endif
  	if (udp_try_make_stateless(skb))
  		scratch->_tsize_state |= UDP_SKB_IS_STATELESS;
  }
  
  static void udp_skb_csum_unnecessary_set(struct sk_buff *skb)
  {
  	/* We come here after udp_lib_checksum_complete() returned 0.
  	 * This means that __skb_checksum_complete() might have
  	 * set skb->csum_valid to 1.
  	 * On 64bit platforms, we can set csum_unnecessary
  	 * to true, but only if the skb is not shared.
  	 */
  #if BITS_PER_LONG == 64
  	if (!skb_shared(skb))
  		udp_skb_scratch(skb)->csum_unnecessary = true;
  #endif
  }
  
  static int udp_skb_truesize(struct sk_buff *skb)
  {
  	return udp_skb_scratch(skb)->_tsize_state & ~UDP_SKB_IS_STATELESS;
  }
  
  static bool udp_skb_has_head_state(struct sk_buff *skb)
  {
  	return !(udp_skb_scratch(skb)->_tsize_state & UDP_SKB_IS_STATELESS);
  }
  
  /* fully reclaim rmem/fwd memory allocated for skb */
  static void udp_rmem_release(struct sock *sk, int size, int partial,
  			     bool rx_queue_lock_held)
  {
  	struct udp_sock *up = udp_sk(sk);
  	struct sk_buff_head *sk_queue;
  	int amt;
  
  	if (likely(partial)) {
  		up->forward_deficit += size;
  		size = up->forward_deficit;
  		if (size < (sk->sk_rcvbuf >> 2))
  			return;
  	} else {
  		size += up->forward_deficit;
  	}
  	up->forward_deficit = 0;
  
  	/* acquire the sk_receive_queue for fwd allocated memory scheduling,
  	 * if the called don't held it already
  	 */
  	sk_queue = &sk->sk_receive_queue;
  	if (!rx_queue_lock_held)
  		spin_lock(&sk_queue->lock);
  
  
  	sk->sk_forward_alloc += size;
  	amt = (sk->sk_forward_alloc - partial) & ~(SK_MEM_QUANTUM - 1);
  	sk->sk_forward_alloc -= amt;
  
  	if (amt)
  		__sk_mem_reduce_allocated(sk, amt >> SK_MEM_QUANTUM_SHIFT);
  
  	atomic_sub(size, &sk->sk_rmem_alloc);
  
  	/* this can save us from acquiring the rx queue lock on next receive */
  	skb_queue_splice_tail_init(sk_queue, &up->reader_queue);
  
  	if (!rx_queue_lock_held)
  		spin_unlock(&sk_queue->lock);
  }
  
  /* Note: called with reader_queue.lock held.
   * Instead of using skb->truesize here, find a copy of it in skb->dev_scratch
   * This avoids a cache line miss while receive_queue lock is held.
   * Look at __udp_enqueue_schedule_skb() to find where this copy is done.
   */
  void udp_skb_destructor(struct sock *sk, struct sk_buff *skb)
  {
  	prefetch(&skb->data);
  	udp_rmem_release(sk, udp_skb_truesize(skb), 1, false);
  }
  EXPORT_SYMBOL(udp_skb_destructor);
  
  /* as above, but the caller held the rx queue lock, too */
  static void udp_skb_dtor_locked(struct sock *sk, struct sk_buff *skb)
  {
  	prefetch(&skb->data);
  	udp_rmem_release(sk, udp_skb_truesize(skb), 1, true);
  }
  
  /* Idea of busylocks is to let producers grab an extra spinlock
   * to relieve pressure on the receive_queue spinlock shared by consumer.
   * Under flood, this means that only one producer can be in line
   * trying to acquire the receive_queue spinlock.
   * These busylock can be allocated on a per cpu manner, instead of a
   * per socket one (that would consume a cache line per socket)
   */
  static int udp_busylocks_log __read_mostly;
  static spinlock_t *udp_busylocks __read_mostly;
  
  static spinlock_t *busylock_acquire(void *ptr)
  {
  	spinlock_t *busy;
  
  	busy = udp_busylocks + hash_ptr(ptr, udp_busylocks_log);
  	spin_lock(busy);
  	return busy;
  }
  
  static void busylock_release(spinlock_t *busy)
  {
  	if (busy)
  		spin_unlock(busy);
  }
  
  int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
  {
  	struct sk_buff_head *list = &sk->sk_receive_queue;
  	int rmem, delta, amt, err = -ENOMEM;
  	spinlock_t *busy = NULL;
  	int size;
  
  	/* try to avoid the costly atomic add/sub pair when the receive
  	 * queue is full; always allow at least a packet
  	 */
  	rmem = atomic_read(&sk->sk_rmem_alloc);
  	if (rmem > sk->sk_rcvbuf)
  		goto drop;
  
  	/* Under mem pressure, it might be helpful to help udp_recvmsg()
  	 * having linear skbs :
  	 * - Reduce memory overhead and thus increase receive queue capacity
  	 * - Less cache line misses at copyout() time
  	 * - Less work at consume_skb() (less alien page frag freeing)
  	 */
  	if (rmem > (sk->sk_rcvbuf >> 1)) {
  		skb_condense(skb);
  
  		busy = busylock_acquire(sk);
  	}
  	size = skb->truesize;
  	udp_set_dev_scratch(skb);
  
  	/* we drop only if the receive buf is full and the receive
  	 * queue contains some other skb
  	 */
  	rmem = atomic_add_return(size, &sk->sk_rmem_alloc);
  	if (rmem > (size + sk->sk_rcvbuf))
  		goto uncharge_drop;
  
  	spin_lock(&list->lock);
  	if (size >= sk->sk_forward_alloc) {
  		amt = sk_mem_pages(size);
  		delta = amt << SK_MEM_QUANTUM_SHIFT;
  		if (!__sk_mem_raise_allocated(sk, delta, amt, SK_MEM_RECV)) {
  			err = -ENOBUFS;
  			spin_unlock(&list->lock);
  			goto uncharge_drop;
  		}
  
  		sk->sk_forward_alloc += delta;
  	}
  
  	sk->sk_forward_alloc -= size;
  
  	/* no need to setup a destructor, we will explicitly release the
  	 * forward allocated memory on dequeue
  	 */
  	sock_skb_set_dropcount(sk, skb);
  
  	__skb_queue_tail(list, skb);
  	spin_unlock(&list->lock);
  
  	if (!sock_flag(sk, SOCK_DEAD))
  		sk->sk_data_ready(sk);
  
  	busylock_release(busy);
  	return 0;
  
  uncharge_drop:
  	atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
  
  drop:
  	atomic_inc(&sk->sk_drops);
  	busylock_release(busy);
  	return err;
  }
  EXPORT_SYMBOL_GPL(__udp_enqueue_schedule_skb);
  
  void udp_destruct_sock(struct sock *sk)
  {
  	/* reclaim completely the forward allocated memory */
  	struct udp_sock *up = udp_sk(sk);
  	unsigned int total = 0;
  	struct sk_buff *skb;
  
  	skb_queue_splice_tail_init(&sk->sk_receive_queue, &up->reader_queue);
  	while ((skb = __skb_dequeue(&up->reader_queue)) != NULL) {
  		total += skb->truesize;
  		kfree_skb(skb);
  	}
  	udp_rmem_release(sk, total, 0, true);
  
  	inet_sock_destruct(sk);
  }
  EXPORT_SYMBOL_GPL(udp_destruct_sock);
  
  int udp_init_sock(struct sock *sk)
  {
  	skb_queue_head_init(&udp_sk(sk)->reader_queue);
  	sk->sk_destruct = udp_destruct_sock;
  	return 0;
  }
  EXPORT_SYMBOL_GPL(udp_init_sock);
  
  void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len)
  {
  	if (unlikely(READ_ONCE(sk->sk_peek_off) >= 0)) {
  		bool slow = lock_sock_fast(sk);
  
  		sk_peek_offset_bwd(sk, len);
  		unlock_sock_fast(sk, slow);
  	}
  
  	if (!skb_unref(skb))
  		return;
  
  	/* In the more common cases we cleared the head states previously,
  	 * see __udp_queue_rcv_skb().
  	 */
  	if (unlikely(udp_skb_has_head_state(skb)))
  		skb_release_head_state(skb);
  	__consume_stateless_skb(skb);
  }
  EXPORT_SYMBOL_GPL(skb_consume_udp);
  
  static struct sk_buff *__first_packet_length(struct sock *sk,
  					     struct sk_buff_head *rcvq,
  					     int *total)
  {
  	struct sk_buff *skb;
  
  	while ((skb = skb_peek(rcvq)) != NULL) {
  		if (udp_lib_checksum_complete(skb)) {
  			__UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS,
  					IS_UDPLITE(sk));
  			__UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS,
  					IS_UDPLITE(sk));
  			atomic_inc(&sk->sk_drops);
  			__skb_unlink(skb, rcvq);
  			*total += skb->truesize;
  			kfree_skb(skb);
  		} else {
  			udp_skb_csum_unnecessary_set(skb);
  			break;
  		}
  	}
  	return skb;
  }
  
  /**
   *	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 -1 if none is found.
   */
  static int first_packet_length(struct sock *sk)
  {
  	struct sk_buff_head *rcvq = &udp_sk(sk)->reader_queue;
  	struct sk_buff_head *sk_queue = &sk->sk_receive_queue;
  	struct sk_buff *skb;
  	int total = 0;
  	int res;
  
  	spin_lock_bh(&rcvq->lock);
  	skb = __first_packet_length(sk, rcvq, &total);
  	if (!skb && !skb_queue_empty_lockless(sk_queue)) {
  		spin_lock(&sk_queue->lock);
  		skb_queue_splice_tail_init(sk_queue, rcvq);
  		spin_unlock(&sk_queue->lock);
  
  		skb = __first_packet_length(sk, rcvq, &total);
  	}
  	res = skb ? skb->len : -1;
  	if (total)
  		udp_rmem_release(sk, total, 1, false);
  	spin_unlock_bh(&rcvq->lock);
  	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:
  	{
  		int amount = max_t(int, 0, first_packet_length(sk));
  
  		return put_user(amount, (int __user *)arg);
  	}
  
  	default:
  		return -ENOIOCTLCMD;
  	}
  
  	return 0;
  }
  EXPORT_SYMBOL(udp_ioctl);
  
  struct sk_buff *__skb_recv_udp(struct sock *sk, unsigned int flags,
  			       int noblock, int *off, int *err)
  {
  	struct sk_buff_head *sk_queue = &sk->sk_receive_queue;
  	struct sk_buff_head *queue;
  	struct sk_buff *last;
  	long timeo;
  	int error;
  
  	queue = &udp_sk(sk)->reader_queue;
  	flags |= noblock ? MSG_DONTWAIT : 0;
  	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
  	do {
  		struct sk_buff *skb;
  
  		error = sock_error(sk);
  		if (error)
  			break;
  
  		error = -EAGAIN;
  		do {
  			spin_lock_bh(&queue->lock);
  			skb = __skb_try_recv_from_queue(sk, queue, flags,
  							udp_skb_destructor,
  							off, err, &last);
  			if (skb) {
  				spin_unlock_bh(&queue->lock);
  				return skb;
  			}
  
  			if (skb_queue_empty_lockless(sk_queue)) {
  				spin_unlock_bh(&queue->lock);
  				goto busy_check;
  			}
  
  			/* refill the reader queue and walk it again
  			 * keep both queues locked to avoid re-acquiring
  			 * the sk_receive_queue lock if fwd memory scheduling
  			 * is needed.
  			 */
  			spin_lock(&sk_queue->lock);
  			skb_queue_splice_tail_init(sk_queue, queue);
  
  			skb = __skb_try_recv_from_queue(sk, queue, flags,
  							udp_skb_dtor_locked,
  							off, err, &last);
  			spin_unlock(&sk_queue->lock);
  			spin_unlock_bh(&queue->lock);
  			if (skb)
  				return skb;
  
  busy_check:
  			if (!sk_can_busy_loop(sk))
  				break;
  
  			sk_busy_loop(sk, flags & MSG_DONTWAIT);
  		} while (!skb_queue_empty_lockless(sk_queue));
  
  		/* sk_queue is empty, reader_queue may contain peeked packets */
  	} while (timeo &&
  		 !__skb_wait_for_more_packets(sk, &error, &timeo,
  					      (struct sk_buff *)sk_queue));
  
  	*err = error;
  	return NULL;
  }
  EXPORT_SYMBOL(__skb_recv_udp);
  
  /*
   * 	This should be easy, if there is something there we
   * 	return it, otherwise we block.
   */
  
  int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
  		int flags, int *addr_len)
  {
  	struct inet_sock *inet = inet_sk(sk);
  	DECLARE_SOCKADDR(struct sockaddr_in *, sin, msg->msg_name);
  	struct sk_buff *skb;
  	unsigned int ulen, copied;
  	int off, err, peeking = flags & MSG_PEEK;
  	int is_udplite = IS_UDPLITE(sk);
  	bool checksum_valid = false;
  
  	if (flags & MSG_ERRQUEUE)
  		return ip_recv_error(sk, msg, len, addr_len);
  
  try_again:
  	off = sk_peek_offset(sk, flags);
  	skb = __skb_recv_udp(sk, flags, noblock, &off, &err);
  	if (!skb)
  		return err;
  
  	ulen = udp_skb_len(skb);
  	copied = len;
  	if (copied > ulen - off)
  		copied = ulen - off;
  	else if (copied < ulen)
  		msg->msg_flags |= MSG_TRUNC;
  
  	/*
  	 * If checksum is needed at all, try to do it while copying the
  	 * data.  If the data is truncated, or if we only want a partial
  	 * coverage checksum (UDP-Lite), do it before the copy.
  	 */
  
  	if (copied < ulen || peeking ||
  	    (is_udplite && UDP_SKB_CB(skb)->partial_cov)) {
  		checksum_valid = udp_skb_csum_unnecessary(skb) ||
  				!__udp_lib_checksum_complete(skb);
  		if (!checksum_valid)
  			goto csum_copy_err;
  	}
  
  	if (checksum_valid || udp_skb_csum_unnecessary(skb)) {
  		if (udp_skb_is_linear(skb))
  			err = copy_linear_skb(skb, copied, off, &msg->msg_iter);
  		else
  			err = skb_copy_datagram_msg(skb, off, msg, copied);
  	} else {
  		err = skb_copy_and_csum_datagram_msg(skb, off, msg);
  
  		if (err == -EINVAL)
  			goto csum_copy_err;
  	}
  
  	if (unlikely(err)) {
  		if (!peeking) {
  			atomic_inc(&sk->sk_drops);
  			UDP_INC_STATS(sock_net(sk),
  				      UDP_MIB_INERRORS, is_udplite);
  		}
  		kfree_skb(skb);
  		return err;
  	}
  
  	if (!peeking)
  		UDP_INC_STATS(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));
  		*addr_len = sizeof(*sin);
  
  		if (cgroup_bpf_enabled)
  			BPF_CGROUP_RUN_PROG_UDP4_RECVMSG_LOCK(sk,
  							(struct sockaddr *)sin);
  	}
  
  	if (udp_sk(sk)->gro_enabled)
  		udp_cmsg_recv(msg, sk, skb);
  
  	if (inet->cmsg_flags)
  		ip_cmsg_recv_offset(msg, sk, skb, sizeof(struct udphdr), off);
  
  	err = copied;
  	if (flags & MSG_TRUNC)
  		err = ulen;
  
  	skb_consume_udp(sk, skb, peeking ? -err : err);
  	return err;
  
  csum_copy_err:
  	if (!__sk_queue_drop_skb(sk, &udp_sk(sk)->reader_queue, skb, flags,
  				 udp_skb_destructor)) {
  		UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
  		UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
  	}
  	kfree_skb(skb);
  
  	/* starting over for a new packet, but check if we need to yield */
  	cond_resched();
  	msg->msg_flags &= ~MSG_TRUNC;
  	goto try_again;
  }
  
  int udp_pre_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
  {
  	/* This check is replicated from __ip4_datagram_connect() and
  	 * intended to prevent BPF program called below from accessing bytes
  	 * that are out of the bound specified by user in addr_len.
  	 */
  	if (addr_len < sizeof(struct sockaddr_in))
  		return -EINVAL;
  
  	return BPF_CGROUP_RUN_PROG_INET4_CONNECT_LOCK(sk, uaddr);
  }
  EXPORT_SYMBOL(udp_pre_connect);
  
  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_reset_rxhash(sk);
  	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);
  
  int udp_disconnect(struct sock *sk, int flags)
  {
  	lock_sock(sk);
  	__udp_disconnect(sk, flags);
  	release_sock(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 (rcu_access_pointer(sk->sk_reuseport_cb))
  			reuseport_detach_sock(sk);
  		if (sk_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_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 ||
  		    rcu_access_pointer(sk->sk_reuseport_cb)) {
  			hslot = udp_hashslot(udptable, sock_net(sk),
  					     udp_sk(sk)->udp_port_hash);
  			/* we must lock primary chain too */
  			spin_lock_bh(&hslot->lock);
  			if (rcu_access_pointer(sk->sk_reuseport_cb))
  				reuseport_detach_sock(sk);
  
  			if (hslot2 != nhslot2) {
  				spin_lock(&hslot2->lock);
  				hlist_del_init_rcu(&udp_sk(sk)->udp_portaddr_node);
  				hslot2->count--;
  				spin_unlock(&hslot2->lock);
  
  				spin_lock(&nhslot2->lock);
  				hlist_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);
  
  void udp_v4_rehash(struct sock *sk)
  {
  	u16 new_hash = ipv4_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);
  		sk_mark_napi_id(sk, skb);
  		sk_incoming_cpu_update(sk);
  	} else {
  		sk_mark_napi_id_once(sk, skb);
  	}
  
  	rc = __udp_enqueue_schedule_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(sock_net(sk), UDP_MIB_RCVBUFERRORS,
  					is_udplite);
  		UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
  		kfree_skb(skb);
  		trace_udp_fail_queue_rcv_skb(rc, sk);
  		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.
   */
  static int udp_queue_rcv_one_skb(struct sock *sk, struct sk_buff *skb)
  {
  	struct udp_sock *up = udp_sk(sk);
  	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_ct(skb);
  
  	if (static_branch_unlikely(&udp_encap_needed_key) && up->encap_type) {
  		int (*encap_rcv)(struct sock *sk, struct sk_buff *skb);
  
  		/*
  		 * 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 */
  		encap_rcv = READ_ONCE(up->encap_rcv);
  		if (encap_rcv) {
  			int ret;
  
  			/* Verify checksum before giving to encap */
  			if (udp_lib_checksum_complete(skb))
  				goto csum_error;
  
  			ret = encap_rcv(sk, skb);
  			if (ret <= 0) {
  				__UDP_INC_STATS(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  */
  			net_dbg_ratelimited("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) {
  			net_dbg_ratelimited("UDPLite: coverage %d too small, need min %d\n",
  					    UDP_SKB_CB(skb)->cscov, up->pcrlen);
  			goto drop;
  		}
  	}
  
  	prefetch(&sk->sk_rmem_alloc);
  	if (rcu_access_pointer(sk->sk_filter) &&
  	    udp_lib_checksum_complete(skb))
  			goto csum_error;
  
  	if (sk_filter_trim_cap(sk, skb, sizeof(struct udphdr)))
  		goto drop;
  
  	udp_csum_pull_header(skb);
  
  	ipv4_pktinfo_prepare(sk, skb);
  	return __udp_queue_rcv_skb(sk, skb);
  
  csum_error:
  	__UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
  drop:
  	__UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
  	atomic_inc(&sk->sk_drops);
  	kfree_skb(skb);
  	return -1;
  }
  
  static int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
  {
  	struct sk_buff *next, *segs;
  	int ret;
  
  	if (likely(!udp_unexpected_gso(sk, skb)))
  		return udp_queue_rcv_one_skb(sk, skb);
  
  	BUILD_BUG_ON(sizeof(struct udp_skb_cb) > SKB_SGO_CB_OFFSET);
  	__skb_push(skb, -skb_mac_offset(skb));
  	segs = udp_rcv_segment(sk, skb, true);
  	for (skb = segs; skb; skb = next) {
  		next = skb->next;
  		__skb_pull(skb, skb_transport_offset(skb));
  		ret = udp_queue_rcv_one_skb(sk, skb);
  		if (ret > 0)
  			ip_protocol_deliver_rcu(dev_net(skb->dev), skb, -ret);
  	}
  	return 0;
  }
  
  /* For TCP sockets, sk_rx_dst is protected by socket lock
   * For UDP, we use xchg() to guard against concurrent changes.
   */
  bool udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst)
  {
  	struct dst_entry *old;
  
  	if (dst_hold_safe(dst)) {
  		old = xchg(&sk->sk_rx_dst, dst);
  		dst_release(old);
  		return old != dst;
  	}
  	return false;
  }
  EXPORT_SYMBOL(udp_sk_rx_dst_set);
  
  /*
   *	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,
  				    int proto)
  {
  	struct sock *sk, *first = NULL;
  	unsigned short hnum = ntohs(uh->dest);
  	struct udp_hslot *hslot = udp_hashslot(udptable, net, hnum);
  	unsigned int hash2 = 0, hash2_any = 0, use_hash2 = (hslot->count > 10);
  	unsigned int offset = offsetof(typeof(*sk), sk_node);
  	int dif = skb->dev->ifindex;
  	int sdif = inet_sdif(skb);
  	struct hlist_node *node;
  	struct sk_buff *nskb;
  
  	if (use_hash2) {
  		hash2_any = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum) &
  			    udptable->mask;
  		hash2 = ipv4_portaddr_hash(net, daddr, hnum) & udptable->mask;
  start_lookup:
  		hslot = &udptable->hash2[hash2];
  		offset = offsetof(typeof(*sk), __sk_common.skc_portaddr_node);
  	}
  
  	sk_for_each_entry_offset_rcu(sk, node, &hslot->head, offset) {
  		if (!__udp_is_mcast_sock(net, sk, uh->dest, daddr,
  					 uh->source, saddr, dif, sdif, hnum))
  			continue;
  
  		if (!first) {
  			first = sk;
  			continue;
  		}
  		nskb = skb_clone(skb, GFP_ATOMIC);
  
  		if (unlikely(!nskb)) {
  			atomic_inc(&sk->sk_drops);
  			__UDP_INC_STATS(net, UDP_MIB_RCVBUFERRORS,
  					IS_UDPLITE(sk));
  			__UDP_INC_STATS(net, UDP_MIB_INERRORS,
  					IS_UDPLITE(sk));
  			continue;
  		}
  		if (udp_queue_rcv_skb(sk, nskb) > 0)
  			consume_skb(nskb);
  	}
  
  	/* Also lookup *:port if we are using hash2 and haven't done so yet. */
  	if (use_hash2 && hash2 != hash2_any) {
  		hash2 = hash2_any;
  		goto start_lookup;
  	}
  
  	if (first) {
  		if (udp_queue_rcv_skb(first, skb) > 0)
  			consume_skb(skb);
  	} else {
  		kfree_skb(skb);
  		__UDP_INC_STATS(net, UDP_MIB_IGNOREDMULTI,
  				proto == IPPROTO_UDPLITE);
  	}
  	return 0;
  }
  
  /* Initialize UDP checksum. If exited with zero value (success),
   * CHECKSUM_UNNECESSARY means, that no more checks are required.
   * Otherwise, csum completion requires checksumming 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)
  {
  	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;
  
  		if (UDP_SKB_CB(skb)->partial_cov) {
  			skb->csum = inet_compute_pseudo(skb, proto);
  			return 0;
  		}
  	}
  
  	/* Note, we are only interested in != 0 or == 0, thus the
  	 * force to int.
  	 */
  	err = (__force int)skb_checksum_init_zero_check(skb, proto, uh->check,
  							inet_compute_pseudo);
  	if (err)
  		return err;
  
  	if (skb->ip_summed == CHECKSUM_COMPLETE && !skb->csum_valid) {
  		/* If SW calculated the value, we know it's bad */
  		if (skb->csum_complete_sw)
  			return 1;
  
  		/* HW says the value is bad. Let's validate that.
  		 * skb->csum is no longer the full packet checksum,
  		 * so don't treat it as such.
  		 */
  		skb_checksum_complete_unset(skb);
  	}
  
  	return 0;
  }
  
  /* wrapper for udp_queue_rcv_skb tacking care of csum conversion and
   * return code conversion for ip layer consumption
   */
  static int udp_unicast_rcv_skb(struct sock *sk, struct sk_buff *skb,
  			       struct udphdr *uh)
  {
  	int ret;
  
  	if (inet_get_convert_csum(sk) && uh->check && !IS_UDPLITE(sk))
  		skb_checksum_try_convert(skb, IPPROTO_UDP, inet_compute_pseudo);
  
  	ret = udp_queue_rcv_skb(sk, skb);
  
  	/* 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;
  }
  
  /*
   *	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;
  
  	sk = skb_steal_sock(skb);
  	if (sk) {
  		struct dst_entry *dst = skb_dst(skb);
  		int ret;
  
  		if (unlikely(sk->sk_rx_dst != dst))
  			udp_sk_rx_dst_set(sk, dst);
  
  		ret = udp_unicast_rcv_skb(sk, skb, uh);
  		sock_put(sk);
  		return ret;
  	}
  
  	if (rt->rt_flags & (RTCF_BROADCAST|RTCF_MULTICAST))
  		return __udp4_lib_mcast_deliver(net, skb, uh,
  						saddr, daddr, udptable, proto);
  
  	sk = __udp4_lib_lookup_skb(skb, uh->source, uh->dest, udptable);
  	if (sk)
  		return udp_unicast_rcv_skb(sk, skb, uh);
  
  	if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
  		goto drop;
  	nf_reset_ct(skb);
  
  	/* No socket. Drop packet silently, if checksum is wrong */
  	if (udp_lib_checksum_complete(skb))
  		goto csum_error;
  
  	__UDP_INC_STATS(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:
  	net_dbg_ratelimited("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).
  	 */
  	net_dbg_ratelimited("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);
  	__UDP_INC_STATS(net, UDP_MIB_CSUMERRORS, proto == IPPROTO_UDPLITE);
  drop:
  	__UDP_INC_STATS(net, UDP_MIB_INERRORS, proto == IPPROTO_UDPLITE);
  	kfree_skb(skb);
  	return 0;
  }
  
  /* We can only early demux multicast if there is a single matching socket.
   * If more than one socket found returns NULL
   */
  static struct sock *__udp4_lib_mcast_demux_lookup(struct net *net,
  						  __be16 loc_port, __be32 loc_addr,
  						  __be16 rmt_port, __be32 rmt_addr,
  						  int dif, int sdif)
  {
  	struct sock *sk, *result;
  	unsigned short hnum = ntohs(loc_port);
  	unsigned int slot = udp_hashfn(net, hnum, udp_table.mask);
  	struct udp_hslot *hslot = &udp_table.hash[slot];
  
  	/* Do not bother scanning a too big list */
  	if (hslot->count > 10)
  		return NULL;
  
  	result = NULL;
  	sk_for_each_rcu(sk, &hslot->head) {
  		if (__udp_is_mcast_sock(net, sk, loc_port, loc_addr,
  					rmt_port, rmt_addr, dif, sdif, hnum)) {
  			if (result)
  				return NULL;
  			result = sk;
  		}
  	}
  
  	return result;
  }
  
  /* For unicast we should only early demux connected sockets or we can
   * break forwarding setups.  The chains here can be long so only check
   * if the first socket is an exact match and if not move on.
   */
  static struct sock *__udp4_lib_demux_lookup(struct net *net,
  					    __be16 loc_port, __be32 loc_addr,
  					    __be16 rmt_port, __be32 rmt_addr,
  					    int dif, int sdif)
  {
  	unsigned short hnum = ntohs(loc_port);
  	unsigned int hash2 = ipv4_portaddr_hash(net, loc_addr, hnum);
  	unsigned int slot2 = hash2 & udp_table.mask;
  	struct udp_hslot *hslot2 = &udp_table.hash2[slot2];
  	INET_ADDR_COOKIE(acookie, rmt_addr, loc_addr);
  	const __portpair ports = INET_COMBINED_PORTS(rmt_port, hnum);
  	struct sock *sk;
  
  	udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
  		if (INET_MATCH(sk, net, acookie, rmt_addr,
  			       loc_addr, ports, dif, sdif))
  			return sk;
  		/* Only check first socket in chain */
  		break;
  	}
  	return NULL;
  }
  
  int udp_v4_early_demux(struct sk_buff *skb)
  {
  	struct net *net = dev_net(skb->dev);
  	struct in_device *in_dev = NULL;
  	const struct iphdr *iph;
  	const struct udphdr *uh;
  	struct sock *sk = NULL;
  	struct dst_entry *dst;
  	int dif = skb->dev->ifindex;
  	int sdif = inet_sdif(skb);
  	int ours;
  
  	/* validate the packet */
  	if (!pskb_may_pull(skb, skb_transport_offset(skb) + sizeof(struct udphdr)))
  		return 0;
  
  	iph = ip_hdr(skb);
  	uh = udp_hdr(skb);
  
  	if (skb->pkt_type == PACKET_MULTICAST) {
  		in_dev = __in_dev_get_rcu(skb->dev);
  
  		if (!in_dev)
  			return 0;
  
  		ours = ip_check_mc_rcu(in_dev, iph->daddr, iph->saddr,
  				       iph->protocol);
  		if (!ours)
  			return 0;
  
  		sk = __udp4_lib_mcast_demux_lookup(net, uh->dest, iph->daddr,
  						   uh->source, iph->saddr,
  						   dif, sdif);
  	} else if (skb->pkt_type == PACKET_HOST) {
  		sk = __udp4_lib_demux_lookup(net, uh->dest, iph->daddr,
  					     uh->source, iph->saddr, dif, sdif);
  	}
  
  	if (!sk || !refcount_inc_not_zero(&sk->sk_refcnt))
  		return 0;
  
  	skb->sk = sk;
  	skb->destructor = sock_efree;
  	dst = READ_ONCE(sk->sk_rx_dst);
  
  	if (dst)
  		dst = dst_check(dst, 0);
  	if (dst) {
  		u32 itag = 0;
  
  		/* set noref for now.
  		 * any place which wants to hold dst has to call
  		 * dst_hold_safe()
  		 */
  		skb_dst_set_noref(skb, dst);
  
  		/* for unconnected multicast sockets we need to validate
  		 * the source on each packet
  		 */
  		if (!inet_sk(sk)->inet_daddr && in_dev)
  			return ip_mc_validate_source(skb, iph->daddr,
  						     iph->saddr, iph->tos,
  						     skb->dev, in_dev, &itag);
  	}
  	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)
  {
  	struct udp_sock *up = udp_sk(sk);
  	bool slow = lock_sock_fast(sk);
  	udp_flush_pending_frames(sk);
  	unlock_sock_fast(sk, slow);
  	if (static_branch_unlikely(&udp_encap_needed_key)) {
  		if (up->encap_type) {
  			void (*encap_destroy)(struct sock *sk);
  			encap_destroy = READ_ONCE(up->encap_destroy);
  			if (encap_destroy)
  				encap_destroy(sk);
  		}
  		if (up->encap_enabled)
  			static_branch_dec(&udp_encap_needed_key);
  	}
  }
  
  /*
   *	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, valbool;
  	int err = 0;
  	int is_udplite = IS_UDPLITE(sk);
  
  	if (optlen < sizeof(int))
  		return -EINVAL;
  
  	if (get_user(val, (int __user *)optval))
  		return -EFAULT;
  
  	valbool = val ? 1 : 0;
  
  	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;
  			lock_sock(sk);
  			udp_tunnel_encap_enable(sk->sk_socket);
  			release_sock(sk);
  			break;
  		default:
  			err = -ENOPROTOOPT;
  			break;
  		}
  		break;
  
  	case UDP_NO_CHECK6_TX:
  		up->no_check6_tx = valbool;
  		break;
  
  	case UDP_NO_CHECK6_RX:
  		up->no_check6_rx = valbool;
  		break;
  
  	case UDP_SEGMENT:
  		if (val < 0 || val > USHRT_MAX)
  			return -EINVAL;
  		up->gso_size = val;
  		break;
  
  	case UDP_GRO:
  		lock_sock(sk);
  		if (valbool)
  			udp_tunnel_encap_enable(sk->sk_socket);
  		up->gro_enabled = valbool;
  		release_sock(sk);
  		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;
  
  	case UDP_NO_CHECK6_TX:
  		val = up->no_check6_tx;
  		break;
  
  	case UDP_NO_CHECK6_RX:
  		val = up->no_check6_rx;
  		break;
  
  	case UDP_SEGMENT:
  		val = up->gso_size;
  		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.
   */
  __poll_t udp_poll(struct file *file, struct socket *sock, poll_table *wait)
  {
  	__poll_t mask = datagram_poll(file, sock, wait);
  	struct sock *sk = sock->sk;
  
  	if (!skb_queue_empty_lockless(&udp_sk(sk)->reader_queue))
  		mask |= EPOLLIN | EPOLLRDNORM;
  
  	/* Check for false positives due to checksum errors */
  	if ((mask & EPOLLRDNORM) && !(file->f_flags & O_NONBLOCK) &&
  	    !(sk->sk_shutdown & RCV_SHUTDOWN) && first_packet_length(sk) == -1)
  		mask &= ~(EPOLLIN | EPOLLRDNORM);
  
  	return mask;
  
  }
  EXPORT_SYMBOL(udp_poll);
  
  int udp_abort(struct sock *sk, int err)
  {
  	lock_sock(sk);
  
  	sk->sk_err = err;
  	sk->sk_error_report(sk);
  	__udp_disconnect(sk, 0);
  
  	release_sock(sk);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(udp_abort);
  
  struct proto udp_prot = {
  	.name			= "UDP",
  	.owner			= THIS_MODULE,
  	.close			= udp_lib_close,
  	.pre_connect		= udp_pre_connect,
  	.connect		= ip4_datagram_connect,
  	.disconnect		= udp_disconnect,
  	.ioctl			= udp_ioctl,
  	.init			= udp_init_sock,
  	.destroy		= udp_destroy_sock,
  	.setsockopt		= udp_setsockopt,
  	.getsockopt		= udp_getsockopt,
  	.sendmsg		= udp_sendmsg,
  	.recvmsg		= udp_recvmsg,
  	.sendpage		= udp_sendpage,
  	.release_cb		= ip4_datagram_release_cb,
  	.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_offset	= offsetof(struct net, ipv4.sysctl_udp_wmem_min),
  	.sysctl_rmem_offset	= offsetof(struct net, ipv4.sysctl_udp_rmem_min),
  	.obj_size		= sizeof(struct udp_sock),
  	.h.udp_table		= &udp_table,
  #ifdef CONFIG_COMPAT
  	.compat_setsockopt	= compat_udp_setsockopt,
  	.compat_getsockopt	= compat_udp_getsockopt,
  #endif
  	.diag_destroy		= udp_abort,
  };
  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_seq_afinfo *afinfo = PDE_DATA(file_inode(seq->file));
  	struct udp_iter_state *state = seq->private;
  	struct net *net = seq_file_net(seq);
  
  	for (state->bucket = start; state->bucket <= afinfo->udp_table->mask;
  	     ++state->bucket) {
  		struct udp_hslot *hslot = &afinfo->udp_table->hash[state->bucket];
  
  		if (hlist_empty(&hslot->head))
  			continue;
  
  		spin_lock_bh(&hslot->lock);
  		sk_for_each(sk, &hslot->head) {
  			if (!net_eq(sock_net(sk), net))
  				continue;
  			if (sk->sk_family == afinfo->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_seq_afinfo *afinfo = PDE_DATA(file_inode(seq->file));
  	struct udp_iter_state *state = seq->private;
  	struct net *net = seq_file_net(seq);
  
  	do {
  		sk = sk_next(sk);
  	} while (sk && (!net_eq(sock_net(sk), net) || sk->sk_family != afinfo->family));
  
  	if (!sk) {
  		if (state->bucket <= afinfo->udp_table->mask)
  			spin_unlock_bh(&afinfo->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;
  }
  
  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;
  }
  EXPORT_SYMBOL(udp_seq_start);
  
  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;
  }
  EXPORT_SYMBOL(udp_seq_next);
  
  void udp_seq_stop(struct seq_file *seq, void *v)
  {
  	struct udp_seq_afinfo *afinfo = PDE_DATA(file_inode(seq->file));
  	struct udp_iter_state *state = seq->private;
  
  	if (state->bucket <= afinfo->udp_table->mask)
  		spin_unlock_bh(&afinfo->udp_table->hash[state->bucket].lock);
  }
  EXPORT_SYMBOL(udp_seq_stop);
  
  /* ------------------------------------------------------------------------ */
  static void udp4_format_sock(struct sock *sp, struct seq_file *f,
  		int bucket)
  {
  	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 %5u %8d %lu %d %pK %u",
  		bucket, src, srcp, dest, destp, sp->sk_state,
  		sk_wmem_alloc_get(sp),
  		udp_rqueue_get(sp),
  		0, 0L, 0,
  		from_kuid_munged(seq_user_ns(f), sock_i_uid(sp)),
  		0, sock_i_ino(sp),
  		refcount_read(&sp->sk_refcnt), sp,
  		atomic_read(&sp->sk_drops));
  }
  
  int udp4_seq_show(struct seq_file *seq, void *v)
  {
  	seq_setwidth(seq, 127);
  	if (v == SEQ_START_TOKEN)
  		seq_puts(seq, "  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;
  
  		udp4_format_sock(v, seq, state->bucket);
  	}
  	seq_pad(seq, '\n');
  	return 0;
  }
  
  const struct seq_operations udp_seq_ops = {
  	.start		= udp_seq_start,
  	.next		= udp_seq_next,
  	.stop		= udp_seq_stop,
  	.show		= udp4_seq_show,
  };
  EXPORT_SYMBOL(udp_seq_ops);
  
  static struct udp_seq_afinfo udp4_seq_afinfo = {
  	.family		= AF_INET,
  	.udp_table	= &udp_table,
  };
  
  static int __net_init udp4_proc_init_net(struct net *net)
  {
  	if (!proc_create_net_data("udp", 0444, net->proc_net, &udp_seq_ops,
  			sizeof(struct udp_iter_state), &udp4_seq_afinfo))
  		return -ENOMEM;
  	return 0;
  }
  
  static void __net_exit udp4_proc_exit_net(struct net *net)
  {
  	remove_proc_entry("udp", net->proc_net);
  }
  
  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)
  {
  	ssize_t ret;
  
  	if (!str)
  		return 0;
  
  	ret = kstrtoul(str, 0, &uhash_entries);
  	if (ret)
  		return 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;
  
  	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,
  					      UDP_HTABLE_SIZE_MIN,
  					      64 * 1024);
  
  	table->hash2 = table->hash + (table->mask + 1);
  	for (i = 0; i <= table->mask; i++) {
  		INIT_HLIST_HEAD(&table->hash[i].head);
  		table->hash[i].count = 0;
  		spin_lock_init(&table->hash[i].lock);
  	}
  	for (i = 0; i <= table->mask; i++) {
  		INIT_HLIST_HEAD(&table->hash2[i].head);
  		table->hash2[i].count = 0;
  		spin_lock_init(&table->hash2[i].lock);
  	}
  }
  
  u32 udp_flow_hashrnd(void)
  {
  	static u32 hashrnd __read_mostly;
  
  	net_get_random_once(&hashrnd, sizeof(hashrnd));
  
  	return hashrnd;
  }
  EXPORT_SYMBOL(udp_flow_hashrnd);
  
  static void __udp_sysctl_init(struct net *net)
  {
  	net->ipv4.sysctl_udp_rmem_min = SK_MEM_QUANTUM;
  	net->ipv4.sysctl_udp_wmem_min = SK_MEM_QUANTUM;
  
  #ifdef CONFIG_NET_L3_MASTER_DEV
  	net->ipv4.sysctl_udp_l3mdev_accept = 0;
  #endif
  }
  
  static int __net_init udp_sysctl_init(struct net *net)
  {
  	__udp_sysctl_init(net);
  	return 0;
  }
  
  static struct pernet_operations __net_initdata udp_sysctl_ops = {
  	.init	= udp_sysctl_init,
  };
  
  void __init udp_init(void)
  {
  	unsigned long limit;
  	unsigned int i;
  
  	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;
  
  	__udp_sysctl_init(&init_net);
  
  	/* 16 spinlocks per cpu */
  	udp_busylocks_log = ilog2(nr_cpu_ids) + 4;
  	udp_busylocks = kmalloc(sizeof(spinlock_t) << udp_busylocks_log,
  				GFP_KERNEL);
  	if (!udp_busylocks)
  		panic("UDP: failed to alloc udp_busylocks\n");
  	for (i = 0; i < (1U << udp_busylocks_log); i++)
  		spin_lock_init(udp_busylocks + i);
  
  	if (register_pernet_subsys(&udp_sysctl_ops))
  		panic("UDP: failed to init sysctl parameters.\n");
  }
  