/*
   * 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.
   *
   *		Support for INET connection oriented protocols.
   *
   * Authors:	See the TCP sources
   *
   *		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 <linux/module.h>
  #include <linux/jhash.h>
  
  #include <net/inet_connection_sock.h>
  #include <net/inet_hashtables.h>
  #include <net/inet_timewait_sock.h>
  #include <net/ip.h>
  #include <net/route.h>
  #include <net/tcp_states.h>

  #include <net/xfrm.h>

  #include <net/tcp.h>

  #include <net/sock_reuseport.h>

  #include <net/addrconf.h>

  
  #ifdef INET_CSK_DEBUG
  const char inet_csk_timer_bug_msg[] = "inet_csk BUG: unknown timer value
  ";
  EXPORT_SYMBOL(inet_csk_timer_bug_msg);
  #endif

  #if IS_ENABLED(CONFIG_IPV6)
  /* match_wildcard == true:  IPV6_ADDR_ANY equals to any IPv6 addresses if IPv6
   *                          only, and any IPv4 addresses if not IPv6 only
   * match_wildcard == false: addresses must be exactly the same, i.e.
   *                          IPV6_ADDR_ANY only equals to IPV6_ADDR_ANY,
   *                          and 0.0.0.0 equals to 0.0.0.0 only
   */

  static int ipv6_rcv_saddr_equal(const struct in6_addr *sk1_rcv_saddr6,
  				const struct in6_addr *sk2_rcv_saddr6,
  				__be32 sk1_rcv_saddr, __be32 sk2_rcv_saddr,
  				bool sk1_ipv6only, bool sk2_ipv6only,

  				bool match_wildcard)
  {

  	int addr_type = ipv6_addr_type(sk1_rcv_saddr6);

  	int addr_type2 = sk2_rcv_saddr6 ? ipv6_addr_type(sk2_rcv_saddr6) : IPV6_ADDR_MAPPED;
  
  	/* if both are mapped, treat as IPv4 */
  	if (addr_type == IPV6_ADDR_MAPPED && addr_type2 == IPV6_ADDR_MAPPED) {
  		if (!sk2_ipv6only) {

  			if (sk1_rcv_saddr == sk2_rcv_saddr)

  				return 1;

  			if (!sk1_rcv_saddr || !sk2_rcv_saddr)

  				return match_wildcard;
  		}
  		return 0;
  	}
  
  	if (addr_type == IPV6_ADDR_ANY && addr_type2 == IPV6_ADDR_ANY)
  		return 1;
  
  	if (addr_type2 == IPV6_ADDR_ANY && match_wildcard &&
  	    !(sk2_ipv6only && addr_type == IPV6_ADDR_MAPPED))
  		return 1;
  
  	if (addr_type == IPV6_ADDR_ANY && match_wildcard &&

  	    !(sk1_ipv6only && addr_type2 == IPV6_ADDR_MAPPED))

  		return 1;
  
  	if (sk2_rcv_saddr6 &&

  	    ipv6_addr_equal(sk1_rcv_saddr6, sk2_rcv_saddr6))

  		return 1;
  
  	return 0;
  }
  #endif
  
  /* match_wildcard == true:  0.0.0.0 equals to any IPv4 addresses
   * match_wildcard == false: addresses must be exactly the same, i.e.
   *                          0.0.0.0 only equals to 0.0.0.0
   */

  static int ipv4_rcv_saddr_equal(__be32 sk1_rcv_saddr, __be32 sk2_rcv_saddr,
  				bool sk2_ipv6only, bool match_wildcard)

  {

  	if (!sk2_ipv6only) {
  		if (sk1_rcv_saddr == sk2_rcv_saddr)

  			return 1;

  		if (!sk1_rcv_saddr || !sk2_rcv_saddr)

  			return match_wildcard;
  	}
  	return 0;
  }
  
  int inet_rcv_saddr_equal(const struct sock *sk, const struct sock *sk2,
  			 bool match_wildcard)
  {
  #if IS_ENABLED(CONFIG_IPV6)
  	if (sk->sk_family == AF_INET6)

  		return ipv6_rcv_saddr_equal(&sk->sk_v6_rcv_saddr,

  					    inet6_rcv_saddr(sk2),

  					    sk->sk_rcv_saddr,
  					    sk2->sk_rcv_saddr,
  					    ipv6_only_sock(sk),
  					    ipv6_only_sock(sk2),
  					    match_wildcard);

  #endif

  	return ipv4_rcv_saddr_equal(sk->sk_rcv_saddr, sk2->sk_rcv_saddr,
  				    ipv6_only_sock(sk2), match_wildcard);

  }
  EXPORT_SYMBOL(inet_rcv_saddr_equal);

  void inet_get_local_port_range(struct net *net, int *low, int *high)

  {

  	unsigned int seq;

  	do {

  		seq = read_seqbegin(&net->ipv4.ip_local_ports.lock);

  		*low = net->ipv4.ip_local_ports.range[0];
  		*high = net->ipv4.ip_local_ports.range[1];
  	} while (read_seqretry(&net->ipv4.ip_local_ports.lock, seq));

  }
  EXPORT_SYMBOL(inet_get_local_port_range);

  static int inet_csk_bind_conflict(const struct sock *sk,
  				  const struct inet_bind_bucket *tb,
  				  bool relax, bool reuseport_ok)

  {

  	struct sock *sk2;

  	bool reuse = sk->sk_reuse;
  	bool reuseport = !!sk->sk_reuseport && reuseport_ok;

  	kuid_t uid = sock_i_uid((struct sock *)sk);

  	/*
  	 * Unlike other sk lookup places we do not check
  	 * for sk_net here, since _all_ the socks listed
  	 * in tb->owners list belong to the same net - the
  	 * one this bucket belongs to.
  	 */

  	sk_for_each_bound(sk2, &tb->owners) {

  		if (sk != sk2 &&

  		    (!sk->sk_bound_dev_if ||
  		     !sk2->sk_bound_dev_if ||
  		     sk->sk_bound_dev_if == sk2->sk_bound_dev_if)) {

  			if ((!reuse || !sk2->sk_reuse ||
  			    sk2->sk_state == TCP_LISTEN) &&
  			    (!reuseport || !sk2->sk_reuseport ||

  			     rcu_access_pointer(sk->sk_reuseport_cb) ||
  			     (sk2->sk_state != TCP_TIME_WAIT &&

  			     !uid_eq(uid, sock_i_uid(sk2))))) {

  				if (inet_rcv_saddr_equal(sk, sk2, true))

  					break;

  			}

  			if (!relax && reuse && sk2->sk_reuse &&
  			    sk2->sk_state != TCP_LISTEN) {

  				if (inet_rcv_saddr_equal(sk, sk2, true))

  					break;
  			}

  		}
  	}

  	return sk2 != NULL;

  }

  /*
   * Find an open port number for the socket.  Returns with the
   * inet_bind_hashbucket lock held.

   */

  static struct inet_bind_hashbucket *
  inet_csk_find_open_port(struct sock *sk, struct inet_bind_bucket **tb_ret, int *port_ret)

  {

  	struct inet_hashinfo *hinfo = sk->sk_prot->h.hashinfo;

  	int port = 0;

  	struct inet_bind_hashbucket *head;

  	struct net *net = sock_net(sk);

  	int i, low, high, attempt_half;
  	struct inet_bind_bucket *tb;

  	u32 remaining, offset;

  	attempt_half = (sk->sk_reuse == SK_CAN_REUSE) ? 1 : 0;
  other_half_scan:
  	inet_get_local_port_range(net, &low, &high);
  	high++; /* [32768, 60999] -> [32768, 61000[ */
  	if (high - low < 4)
  		attempt_half = 0;
  	if (attempt_half) {
  		int half = low + (((high - low) >> 2) << 1);
  
  		if (attempt_half == 1)
  			high = half;
  		else
  			low = half;
  	}
  	remaining = high - low;
  	if (likely(remaining > 1))
  		remaining &= ~1U;

  	offset = prandom_u32() % remaining;
  	/* __inet_hash_connect() favors ports having @low parity
  	 * We do the opposite to not pollute connect() users.
  	 */
  	offset |= 1U;

  
  other_parity_scan:
  	port = low + offset;
  	for (i = 0; i < remaining; i += 2, port += 2) {
  		if (unlikely(port >= high))
  			port -= remaining;
  		if (inet_is_local_reserved_port(net, port))
  			continue;
  		head = &hinfo->bhash[inet_bhashfn(net, port,
  						  hinfo->bhash_size)];
  		spin_lock_bh(&head->lock);
  		inet_bind_bucket_for_each(tb, &head->chain)
  			if (net_eq(ib_net(tb), net) && tb->port == port) {

  				if (!inet_csk_bind_conflict(sk, tb, false, false))

  					goto success;

  				goto next_port;

  			}

  		tb = NULL;
  		goto success;

  next_port:
  		spin_unlock_bh(&head->lock);
  		cond_resched();
  	}

  	offset--;
  	if (!(offset & 1))
  		goto other_parity_scan;
  
  	if (attempt_half == 1) {
  		/* OK we now try the upper half of the range */
  		attempt_half = 2;
  		goto other_half_scan;
  	}

  	return NULL;
  success:
  	*port_ret = port;
  	*tb_ret = tb;
  	return head;
  }

  static inline int sk_reuseport_match(struct inet_bind_bucket *tb,
  				     struct sock *sk)
  {
  	kuid_t uid = sock_i_uid(sk);
  
  	if (tb->fastreuseport <= 0)
  		return 0;
  	if (!sk->sk_reuseport)
  		return 0;
  	if (rcu_access_pointer(sk->sk_reuseport_cb))
  		return 0;
  	if (!uid_eq(tb->fastuid, uid))
  		return 0;
  	/* We only need to check the rcv_saddr if this tb was once marked
  	 * without fastreuseport and then was reset, as we can only know that
  	 * the fast_*rcv_saddr doesn't have any conflicts with the socks on the
  	 * owners list.
  	 */
  	if (tb->fastreuseport == FASTREUSEPORT_ANY)
  		return 1;
  #if IS_ENABLED(CONFIG_IPV6)
  	if (tb->fast_sk_family == AF_INET6)
  		return ipv6_rcv_saddr_equal(&tb->fast_v6_rcv_saddr,

  					    inet6_rcv_saddr(sk),

  					    tb->fast_rcv_saddr,
  					    sk->sk_rcv_saddr,
  					    tb->fast_ipv6_only,
  					    ipv6_only_sock(sk), true);
  #endif
  	return ipv4_rcv_saddr_equal(tb->fast_rcv_saddr, sk->sk_rcv_saddr,
  				    ipv6_only_sock(sk), true);
  }

  /* Obtain a reference to a local port for the given sock,
   * if snum is zero it means select any available local port.
   * We try to allocate an odd port (and leave even ports for connect())
   */
  int inet_csk_get_port(struct sock *sk, unsigned short snum)
  {
  	bool reuse = sk->sk_reuse && sk->sk_state != TCP_LISTEN;
  	struct inet_hashinfo *hinfo = sk->sk_prot->h.hashinfo;
  	int ret = 1, port = snum;
  	struct inet_bind_hashbucket *head;
  	struct net *net = sock_net(sk);
  	struct inet_bind_bucket *tb = NULL;
  	kuid_t uid = sock_i_uid(sk);
  
  	if (!port) {
  		head = inet_csk_find_open_port(sk, &tb, &port);
  		if (!head)
  			return ret;
  		if (!tb)
  			goto tb_not_found;
  		goto success;
  	}
  	head = &hinfo->bhash[inet_bhashfn(net, port,
  					  hinfo->bhash_size)];
  	spin_lock_bh(&head->lock);
  	inet_bind_bucket_for_each(tb, &head->chain)
  		if (net_eq(ib_net(tb), net) && tb->port == port)
  			goto tb_found;

  tb_not_found:
  	tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep,
  				     net, head, port);
  	if (!tb)
  		goto fail_unlock;

  tb_found:
  	if (!hlist_empty(&tb->owners)) {

  		if (sk->sk_reuse == SK_FORCE_REUSE)
  			goto success;

  		if ((tb->fastreuse > 0 && reuse) ||

  		    sk_reuseport_match(tb, sk))

  			goto success;

  		if (inet_csk_bind_conflict(sk, tb, true, true))

  			goto fail_unlock;

  	}
  success:

  	if (hlist_empty(&tb->owners)) {

  		tb->fastreuse = reuse;

  		if (sk->sk_reuseport) {

  			tb->fastreuseport = FASTREUSEPORT_ANY;

  			tb->fastuid = uid;

  			tb->fast_rcv_saddr = sk->sk_rcv_saddr;
  			tb->fast_ipv6_only = ipv6_only_sock(sk);

  			tb->fast_sk_family = sk->sk_family;

  #if IS_ENABLED(CONFIG_IPV6)
  			tb->fast_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
  #endif

  		} else {

  			tb->fastreuseport = 0;

  		}

  	} else {
  		if (!reuse)
  			tb->fastreuse = 0;

  		if (sk->sk_reuseport) {
  			/* We didn't match or we don't have fastreuseport set on
  			 * the tb, but we have sk_reuseport set on this socket
  			 * and we know that there are no bind conflicts with
  			 * this socket in this tb, so reset our tb's reuseport
  			 * settings so that any subsequent sockets that match
  			 * our current socket will be put on the fast path.
  			 *
  			 * If we reset we need to set FASTREUSEPORT_STRICT so we
  			 * do extra checking for all subsequent sk_reuseport
  			 * socks.
  			 */
  			if (!sk_reuseport_match(tb, sk)) {
  				tb->fastreuseport = FASTREUSEPORT_STRICT;
  				tb->fastuid = uid;
  				tb->fast_rcv_saddr = sk->sk_rcv_saddr;
  				tb->fast_ipv6_only = ipv6_only_sock(sk);

  				tb->fast_sk_family = sk->sk_family;

  #if IS_ENABLED(CONFIG_IPV6)
  				tb->fast_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
  #endif
  			}
  		} else {

  			tb->fastreuseport = 0;

  		}

  	}

  	if (!inet_csk(sk)->icsk_bind_hash)

  		inet_bind_hash(sk, tb, port);

  	WARN_ON(inet_csk(sk)->icsk_bind_hash != tb);

  	ret = 0;

  
  fail_unlock:

  	spin_unlock_bh(&head->lock);

  	return ret;
  }

  EXPORT_SYMBOL_GPL(inet_csk_get_port);
  
  /*
   * Wait for an incoming connection, avoid race conditions. This must be called
   * with the socket locked.
   */
  static int inet_csk_wait_for_connect(struct sock *sk, long timeo)
  {
  	struct inet_connection_sock *icsk = inet_csk(sk);
  	DEFINE_WAIT(wait);
  	int err;
  
  	/*
  	 * True wake-one mechanism for incoming connections: only
  	 * one process gets woken up, not the 'whole herd'.
  	 * Since we do not 'race & poll' for established sockets
  	 * anymore, the common case will execute the loop only once.
  	 *
  	 * Subtle issue: "add_wait_queue_exclusive()" will be added
  	 * after any current non-exclusive waiters, and we know that
  	 * it will always _stay_ after any new non-exclusive waiters
  	 * because all non-exclusive waiters are added at the
  	 * beginning of the wait-queue. As such, it's ok to "drop"
  	 * our exclusiveness temporarily when we get woken up without
  	 * having to remove and re-insert us on the wait queue.
  	 */
  	for (;;) {

  		prepare_to_wait_exclusive(sk_sleep(sk), &wait,

  					  TASK_INTERRUPTIBLE);
  		release_sock(sk);
  		if (reqsk_queue_empty(&icsk->icsk_accept_queue))
  			timeo = schedule_timeout(timeo);

  		sched_annotate_sleep();

  		lock_sock(sk);
  		err = 0;
  		if (!reqsk_queue_empty(&icsk->icsk_accept_queue))
  			break;
  		err = -EINVAL;
  		if (sk->sk_state != TCP_LISTEN)
  			break;
  		err = sock_intr_errno(timeo);
  		if (signal_pending(current))
  			break;
  		err = -EAGAIN;
  		if (!timeo)
  			break;
  	}

  	finish_wait(sk_sleep(sk), &wait);

  	return err;
  }
  
  /*
   * This will accept the next outstanding connection.
   */

  struct sock *inet_csk_accept(struct sock *sk, int flags, int *err, bool kern)

  {
  	struct inet_connection_sock *icsk = inet_csk(sk);

  	struct request_sock_queue *queue = &icsk->icsk_accept_queue;

  	struct request_sock *req;

  	struct sock *newsk;

  	int error;
  
  	lock_sock(sk);
  
  	/* We need to make sure that this socket is listening,
  	 * and that it has something pending.
  	 */
  	error = -EINVAL;
  	if (sk->sk_state != TCP_LISTEN)
  		goto out_err;
  
  	/* Find already established connection */

  	if (reqsk_queue_empty(queue)) {

  		long timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK);
  
  		/* If this is a non blocking socket don't sleep */
  		error = -EAGAIN;
  		if (!timeo)
  			goto out_err;
  
  		error = inet_csk_wait_for_connect(sk, timeo);
  		if (error)
  			goto out_err;
  	}

  	req = reqsk_queue_remove(queue, sk);

  	newsk = req->sk;

  	if (sk->sk_protocol == IPPROTO_TCP &&

  	    tcp_rsk(req)->tfo_listener) {
  		spin_lock_bh(&queue->fastopenq.lock);

  		if (tcp_rsk(req)->tfo_listener) {

  			/* We are still waiting for the final ACK from 3WHS
  			 * so can't free req now. Instead, we set req->sk to
  			 * NULL to signify that the child socket is taken
  			 * so reqsk_fastopen_remove() will free the req
  			 * when 3WHS finishes (or is aborted).
  			 */
  			req->sk = NULL;
  			req = NULL;
  		}

  		spin_unlock_bh(&queue->fastopenq.lock);

  	}

  out:
  	release_sock(sk);

  	if (req)

  		reqsk_put(req);

  	return newsk;
  out_err:
  	newsk = NULL;

  	req = NULL;

  	*err = error;
  	goto out;
  }

  EXPORT_SYMBOL(inet_csk_accept);
  
  /*
   * Using different timers for retransmit, delayed acks and probes

   * We may wish use just one timer maintaining a list of expire jiffies

   * to optimize.
   */
  void inet_csk_init_xmit_timers(struct sock *sk,
  			       void (*retransmit_handler)(unsigned long),
  			       void (*delack_handler)(unsigned long),
  			       void (*keepalive_handler)(unsigned long))
  {
  	struct inet_connection_sock *icsk = inet_csk(sk);

  	setup_timer(&icsk->icsk_retransmit_timer, retransmit_handler,
  			(unsigned long)sk);
  	setup_timer(&icsk->icsk_delack_timer, delack_handler,
  			(unsigned long)sk);
  	setup_timer(&sk->sk_timer, keepalive_handler, (unsigned long)sk);

  	icsk->icsk_pending = icsk->icsk_ack.pending = 0;
  }

  EXPORT_SYMBOL(inet_csk_init_xmit_timers);
  
  void inet_csk_clear_xmit_timers(struct sock *sk)
  {
  	struct inet_connection_sock *icsk = inet_csk(sk);
  
  	icsk->icsk_pending = icsk->icsk_ack.pending = icsk->icsk_ack.blocked = 0;
  
  	sk_stop_timer(sk, &icsk->icsk_retransmit_timer);
  	sk_stop_timer(sk, &icsk->icsk_delack_timer);
  	sk_stop_timer(sk, &sk->sk_timer);
  }

  EXPORT_SYMBOL(inet_csk_clear_xmit_timers);
  
  void inet_csk_delete_keepalive_timer(struct sock *sk)
  {
  	sk_stop_timer(sk, &sk->sk_timer);
  }

  EXPORT_SYMBOL(inet_csk_delete_keepalive_timer);
  
  void inet_csk_reset_keepalive_timer(struct sock *sk, unsigned long len)
  {
  	sk_reset_timer(sk, &sk->sk_timer, jiffies + len);
  }

  EXPORT_SYMBOL(inet_csk_reset_keepalive_timer);

  struct dst_entry *inet_csk_route_req(const struct sock *sk,

  				     struct flowi4 *fl4,

  				     const struct request_sock *req)

  {

  	const struct inet_request_sock *ireq = inet_rsk(req);

  	struct net *net = read_pnet(&ireq->ireq_net);

  	struct ip_options_rcu *opt;

  	struct rtable *rt;

  	rcu_read_lock();
  	opt = rcu_dereference(ireq->ireq_opt);

  	flowi4_init_output(fl4, ireq->ir_iif, ireq->ir_mark,

  			   RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE,

  			   sk->sk_protocol, inet_sk_flowi_flags(sk),

  			   (opt && opt->opt.srr) ? opt->opt.faddr : ireq->ir_rmt_addr,

  			   ireq->ir_loc_addr, ireq->ir_rmt_port,

  			   htons(ireq->ir_num), sk->sk_uid);

  	security_req_classify_flow(req, flowi4_to_flowi(fl4));
  	rt = ip_route_output_flow(net, fl4, sk);

  	if (IS_ERR(rt))

  		goto no_route;

  	if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway)

  		goto route_err;

  	rcu_read_unlock();

  	return &rt->dst;

  
  route_err:
  	ip_rt_put(rt);
  no_route:

  	rcu_read_unlock();

  	__IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);

  	return NULL;

  }

  EXPORT_SYMBOL_GPL(inet_csk_route_req);

  struct dst_entry *inet_csk_route_child_sock(const struct sock *sk,

  					    struct sock *newsk,
  					    const struct request_sock *req)
  {
  	const struct inet_request_sock *ireq = inet_rsk(req);

  	struct net *net = read_pnet(&ireq->ireq_net);

  	struct inet_sock *newinet = inet_sk(newsk);

  	struct ip_options_rcu *opt;

  	struct flowi4 *fl4;
  	struct rtable *rt;

  	opt = rcu_dereference(ireq->ireq_opt);

  	fl4 = &newinet->cork.fl.u.ip4;

  	flowi4_init_output(fl4, ireq->ir_iif, ireq->ir_mark,

  			   RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE,
  			   sk->sk_protocol, inet_sk_flowi_flags(sk),

  			   (opt && opt->opt.srr) ? opt->opt.faddr : ireq->ir_rmt_addr,

  			   ireq->ir_loc_addr, ireq->ir_rmt_port,

  			   htons(ireq->ir_num), sk->sk_uid);

  	security_req_classify_flow(req, flowi4_to_flowi(fl4));
  	rt = ip_route_output_flow(net, fl4, sk);
  	if (IS_ERR(rt))
  		goto no_route;

  	if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway)

  		goto route_err;
  	return &rt->dst;
  
  route_err:
  	ip_rt_put(rt);
  no_route:

  	__IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);

  	return NULL;
  }
  EXPORT_SYMBOL_GPL(inet_csk_route_child_sock);

  #if IS_ENABLED(CONFIG_IPV6)

  #define AF_INET_FAMILY(fam) ((fam) == AF_INET)
  #else

  #define AF_INET_FAMILY(fam) true

  #endif

  /* Decide when to expire the request and when to resend SYN-ACK */
  static inline void syn_ack_recalc(struct request_sock *req, const int thresh,
  				  const int max_retries,
  				  const u8 rskq_defer_accept,
  				  int *expire, int *resend)
  {
  	if (!rskq_defer_accept) {

  		*expire = req->num_timeout >= thresh;

  		*resend = 1;
  		return;
  	}

  	*expire = req->num_timeout >= thresh &&
  		  (!inet_rsk(req)->acked || req->num_timeout >= max_retries);

  	/*
  	 * Do not resend while waiting for data after ACK,
  	 * start to resend on end of deferring period to give
  	 * last chance for data or ACK to create established socket.
  	 */
  	*resend = !inet_rsk(req)->acked ||

  		  req->num_timeout >= rskq_defer_accept - 1;

  }

  int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req)

  {

  	int err = req->rsk_ops->rtx_syn_ack(parent, req);

  
  	if (!err)
  		req->num_retrans++;
  	return err;
  }
  EXPORT_SYMBOL(inet_rtx_syn_ack);

  /* return true if req was found in the ehash table */

  static bool reqsk_queue_unlink(struct request_sock_queue *queue,
  			       struct request_sock *req)
  {

  	struct inet_hashinfo *hashinfo = req_to_sk(req)->sk_prot->h.hashinfo;

  	bool found = false;

  	if (sk_hashed(req_to_sk(req))) {
  		spinlock_t *lock = inet_ehash_lockp(hashinfo, req->rsk_hash);

  		spin_lock(lock);
  		found = __sk_nulls_del_node_init_rcu(req_to_sk(req));
  		spin_unlock(lock);
  	}

  	if (timer_pending(&req->rsk_timer) && del_timer_sync(&req->rsk_timer))

  		reqsk_put(req);
  	return found;
  }
  
  void inet_csk_reqsk_queue_drop(struct sock *sk, struct request_sock *req)
  {
  	if (reqsk_queue_unlink(&inet_csk(sk)->icsk_accept_queue, req)) {
  		reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req);
  		reqsk_put(req);
  	}
  }
  EXPORT_SYMBOL(inet_csk_reqsk_queue_drop);

  void inet_csk_reqsk_queue_drop_and_put(struct sock *sk, struct request_sock *req)
  {
  	inet_csk_reqsk_queue_drop(sk, req);
  	reqsk_put(req);
  }
  EXPORT_SYMBOL(inet_csk_reqsk_queue_drop_and_put);

  static void reqsk_timer_handler(unsigned long data)

  {

  	struct request_sock *req = (struct request_sock *)data;
  	struct sock *sk_listener = req->rsk_listener;

  	struct net *net = sock_net(sk_listener);

  	struct inet_connection_sock *icsk = inet_csk(sk_listener);

  	struct request_sock_queue *queue = &icsk->icsk_accept_queue;

  	int qlen, expire = 0, resend = 0;

  	int max_retries, thresh;

  	u8 defer_accept;

  	if (sk_state_load(sk_listener) != TCP_LISTEN)

  		goto drop;

  	max_retries = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_synack_retries;

  	thresh = max_retries;

  	/* Normally all the openreqs are young and become mature
  	 * (i.e. converted to established socket) for first timeout.

  	 * If synack was not acknowledged for 1 second, it means

  	 * one of the following things: synack was lost, ack was lost,
  	 * rtt is high or nobody planned to ack (i.e. synflood).
  	 * When server is a bit loaded, queue is populated with old
  	 * open requests, reducing effective size of queue.
  	 * When server is well loaded, queue size reduces to zero
  	 * after several minutes of work. It is not synflood,
  	 * it is normal operation. The solution is pruning
  	 * too old entries overriding normal timeout, when
  	 * situation becomes dangerous.
  	 *
  	 * Essentially, we reserve half of room for young
  	 * embrions; and abort old ones without pity, if old
  	 * ones are about to clog our table.
  	 */

  	qlen = reqsk_queue_len(queue);

  	if ((qlen << 1) > max(8U, sk_listener->sk_max_ack_backlog)) {

  		int young = reqsk_queue_len_young(queue) << 1;

  
  		while (thresh > 2) {

  			if (qlen < young)

  				break;
  			thresh--;
  			young <<= 1;
  		}
  	}

  	defer_accept = READ_ONCE(queue->rskq_defer_accept);
  	if (defer_accept)
  		max_retries = defer_accept;
  	syn_ack_recalc(req, thresh, max_retries, defer_accept,

  		       &expire, &resend);

  	req->rsk_ops->syn_ack_timeout(req);

  	if (!expire &&
  	    (!resend ||
  	     !inet_rtx_syn_ack(sk_listener, req) ||
  	     inet_rsk(req)->acked)) {
  		unsigned long timeo;
  
  		if (req->num_timeout++ == 0)

  			atomic_dec(&queue->young);

  		timeo = min(TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);

  		mod_timer(&req->rsk_timer, jiffies + timeo);

  		return;
  	}

  drop:

  	inet_csk_reqsk_queue_drop_and_put(sk_listener, req);

  }

  static void reqsk_queue_hash_req(struct request_sock *req,
  				 unsigned long timeout)

  {

  	req->num_retrans = 0;
  	req->num_timeout = 0;
  	req->sk = NULL;

  	setup_pinned_timer(&req->rsk_timer, reqsk_timer_handler,
  			    (unsigned long)req);
  	mod_timer(&req->rsk_timer, jiffies + timeout);

  	inet_ehash_insert(req_to_sk(req), NULL);

  	/* before letting lookups find us, make sure all req fields
  	 * are committed to memory and refcnt initialized.
  	 */
  	smp_wmb();

  	refcount_set(&req->rsk_refcnt, 2 + 1);

  }

  void inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req,
  				   unsigned long timeout)
  {
  	reqsk_queue_hash_req(req, timeout);
  	inet_csk_reqsk_queue_added(sk);

  }

  EXPORT_SYMBOL_GPL(inet_csk_reqsk_queue_hash_add);

  /**
   *	inet_csk_clone_lock - clone an inet socket, and lock its clone
   *	@sk: the socket to clone
   *	@req: request_sock
   *	@priority: for allocation (%GFP_KERNEL, %GFP_ATOMIC, etc)
   *
   *	Caller must unlock socket even in error path (bh_unlock_sock(newsk))
   */
  struct sock *inet_csk_clone_lock(const struct sock *sk,
  				 const struct request_sock *req,
  				 const gfp_t priority)

  {

  	struct sock *newsk = sk_clone_lock(sk, priority);

  	if (newsk) {

  		struct inet_connection_sock *newicsk = inet_csk(newsk);
  
  		newsk->sk_state = TCP_SYN_RECV;
  		newicsk->icsk_bind_hash = NULL;

  		inet_sk(newsk)->inet_dport = inet_rsk(req)->ir_rmt_port;

  		inet_sk(newsk)->inet_num = inet_rsk(req)->ir_num;
  		inet_sk(newsk)->inet_sport = htons(inet_rsk(req)->ir_num);

  		/* listeners have SOCK_RCU_FREE, not the children */
  		sock_reset_flag(newsk, SOCK_RCU_FREE);

  		inet_sk(newsk)->mc_list = NULL;

  		newsk->sk_mark = inet_rsk(req)->ir_mark;

  		atomic64_set(&newsk->sk_cookie,
  			     atomic64_read(&inet_rsk(req)->ir_cookie));

  		newicsk->icsk_retransmits = 0;

  		newicsk->icsk_backoff	  = 0;
  		newicsk->icsk_probes_out  = 0;

  
  		/* Deinitialize accept_queue to trap illegal accesses. */
  		memset(&newicsk->icsk_accept_queue, 0, sizeof(newicsk->icsk_accept_queue));

  
  		security_inet_csk_clone(newsk, req);

  	}
  	return newsk;
  }

  EXPORT_SYMBOL_GPL(inet_csk_clone_lock);

  
  /*
   * At this point, there should be no process reference to this
   * socket, and thus no user references at all.  Therefore we
   * can assume the socket waitqueue is inactive and nobody will
   * try to jump onto it.
   */
  void inet_csk_destroy_sock(struct sock *sk)
  {

  	WARN_ON(sk->sk_state != TCP_CLOSE);
  	WARN_ON(!sock_flag(sk, SOCK_DEAD));

  
  	/* It cannot be in hash table! */

  	WARN_ON(!sk_unhashed(sk));

  	/* If it has not 0 inet_sk(sk)->inet_num, it must be bound */
  	WARN_ON(inet_sk(sk)->inet_num && !inet_csk(sk)->icsk_bind_hash);

  
  	sk->sk_prot->destroy(sk);
  
  	sk_stream_kill_queues(sk);
  
  	xfrm_sk_free_policy(sk);
  
  	sk_refcnt_debug_release(sk);

  	percpu_counter_dec(sk->sk_prot->orphan_count);

  	sock_put(sk);
  }

  EXPORT_SYMBOL(inet_csk_destroy_sock);

  /* This function allows to force a closure of a socket after the call to
   * tcp/dccp_create_openreq_child().
   */
  void inet_csk_prepare_forced_close(struct sock *sk)

  	__releases(&sk->sk_lock.slock)

  {
  	/* sk_clone_lock locked the socket and set refcnt to 2 */
  	bh_unlock_sock(sk);
  	sock_put(sk);
  
  	/* The below has to be done to allow calling inet_csk_destroy_sock */
  	sock_set_flag(sk, SOCK_DEAD);
  	percpu_counter_inc(sk->sk_prot->orphan_count);
  	inet_sk(sk)->inet_num = 0;
  }
  EXPORT_SYMBOL(inet_csk_prepare_forced_close);

  int inet_csk_listen_start(struct sock *sk, int backlog)

  {

  	struct inet_connection_sock *icsk = inet_csk(sk);

  	struct inet_sock *inet = inet_sk(sk);

  	int err = -EADDRINUSE;

  	reqsk_queue_alloc(&icsk->icsk_accept_queue);

  	sk->sk_max_ack_backlog = backlog;

  	sk->sk_ack_backlog = 0;
  	inet_csk_delack_init(sk);
  
  	/* There is race window here: we announce ourselves listening,
  	 * but this transition is still not validated by get_port().
  	 * It is OK, because this socket enters to hash table only
  	 * after validation is complete.
  	 */

  	sk_state_store(sk, TCP_LISTEN);

  	if (!sk->sk_prot->get_port(sk, inet->inet_num)) {
  		inet->inet_sport = htons(inet->inet_num);

  
  		sk_dst_reset(sk);

  		err = sk->sk_prot->hash(sk);

  		if (likely(!err))
  			return 0;

  	}
  
  	sk->sk_state = TCP_CLOSE;

  	return err;

  }

  EXPORT_SYMBOL_GPL(inet_csk_listen_start);

  static void inet_child_forget(struct sock *sk, struct request_sock *req,
  			      struct sock *child)
  {
  	sk->sk_prot->disconnect(child, O_NONBLOCK);
  
  	sock_orphan(child);
  
  	percpu_counter_inc(sk->sk_prot->orphan_count);
  
  	if (sk->sk_protocol == IPPROTO_TCP && tcp_rsk(req)->tfo_listener) {
  		BUG_ON(tcp_sk(child)->fastopen_rsk != req);
  		BUG_ON(sk != req->rsk_listener);
  
  		/* Paranoid, to prevent race condition if
  		 * an inbound pkt destined for child is
  		 * blocked by sock lock in tcp_v4_rcv().
  		 * Also to satisfy an assertion in
  		 * tcp_v4_destroy_sock().
  		 */
  		tcp_sk(child)->fastopen_rsk = NULL;
  	}
  	inet_csk_destroy_sock(child);

  }

  struct sock *inet_csk_reqsk_queue_add(struct sock *sk,
  				      struct request_sock *req,
  				      struct sock *child)

  {
  	struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
  
  	spin_lock(&queue->rskq_lock);
  	if (unlikely(sk->sk_state != TCP_LISTEN)) {
  		inet_child_forget(sk, req, child);

  		child = NULL;

  	} else {
  		req->sk = child;
  		req->dl_next = NULL;
  		if (queue->rskq_accept_head == NULL)
  			queue->rskq_accept_head = req;
  		else
  			queue->rskq_accept_tail->dl_next = req;
  		queue->rskq_accept_tail = req;
  		sk_acceptq_added(sk);
  	}
  	spin_unlock(&queue->rskq_lock);

  	return child;

  }
  EXPORT_SYMBOL(inet_csk_reqsk_queue_add);

  struct sock *inet_csk_complete_hashdance(struct sock *sk, struct sock *child,
  					 struct request_sock *req, bool own_req)
  {
  	if (own_req) {
  		inet_csk_reqsk_queue_drop(sk, req);
  		reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req);

  		if (inet_csk_reqsk_queue_add(sk, req, child))
  			return child;

  	}
  	/* Too bad, another child took ownership of the request, undo. */
  	bh_unlock_sock(child);
  	sock_put(child);
  	return NULL;
  }
  EXPORT_SYMBOL(inet_csk_complete_hashdance);

  /*
   *	This routine closes sockets which have been at least partially
   *	opened, but not yet accepted.
   */
  void inet_csk_listen_stop(struct sock *sk)
  {
  	struct inet_connection_sock *icsk = inet_csk(sk);

  	struct request_sock_queue *queue = &icsk->icsk_accept_queue;

  	struct request_sock *next, *req;

  
  	/* Following specs, it would be better either to send FIN
  	 * (and enter FIN-WAIT-1, it is normal close)
  	 * or to send active reset (abort).
  	 * Certainly, it is pretty dangerous while synflood, but it is
  	 * bad justification for our negligence 8)
  	 * To be honest, we are not able to make either
  	 * of the variants now.			--ANK
  	 */

  	while ((req = reqsk_queue_remove(queue, sk)) != NULL) {

  		struct sock *child = req->sk;

  		local_bh_disable();
  		bh_lock_sock(child);

  		WARN_ON(sock_owned_by_user(child));

  		sock_hold(child);

  		inet_child_forget(sk, req, child);

  		reqsk_put(req);

  		bh_unlock_sock(child);
  		local_bh_enable();
  		sock_put(child);

  		cond_resched();

  	}

  	if (queue->fastopenq.rskq_rst_head) {

  		/* Free all the reqs queued in rskq_rst_head. */

  		spin_lock_bh(&queue->fastopenq.lock);

  		req = queue->fastopenq.rskq_rst_head;

  		queue->fastopenq.rskq_rst_head = NULL;
  		spin_unlock_bh(&queue->fastopenq.lock);

  		while (req != NULL) {
  			next = req->dl_next;

  			reqsk_put(req);

  			req = next;

  		}
  	}

  	WARN_ON_ONCE(sk->sk_ack_backlog);

  }

  EXPORT_SYMBOL_GPL(inet_csk_listen_stop);

  
  void inet_csk_addr2sockaddr(struct sock *sk, struct sockaddr *uaddr)
  {
  	struct sockaddr_in *sin = (struct sockaddr_in *)uaddr;
  	const struct inet_sock *inet = inet_sk(sk);
  
  	sin->sin_family		= AF_INET;

  	sin->sin_addr.s_addr	= inet->inet_daddr;
  	sin->sin_port		= inet->inet_dport;

  }

  EXPORT_SYMBOL_GPL(inet_csk_addr2sockaddr);

  #ifdef CONFIG_COMPAT
  int inet_csk_compat_getsockopt(struct sock *sk, int level, int optname,
  			       char __user *optval, int __user *optlen)
  {

  	const struct inet_connection_sock *icsk = inet_csk(sk);

  	if (icsk->icsk_af_ops->compat_getsockopt)

  		return icsk->icsk_af_ops->compat_getsockopt(sk, level, optname,
  							    optval, optlen);
  	return icsk->icsk_af_ops->getsockopt(sk, level, optname,
  					     optval, optlen);
  }

  EXPORT_SYMBOL_GPL(inet_csk_compat_getsockopt);
  
  int inet_csk_compat_setsockopt(struct sock *sk, int level, int optname,

  			       char __user *optval, unsigned int optlen)

  {

  	const struct inet_connection_sock *icsk = inet_csk(sk);

  	if (icsk->icsk_af_ops->compat_setsockopt)

  		return icsk->icsk_af_ops->compat_setsockopt(sk, level, optname,
  							    optval, optlen);
  	return icsk->icsk_af_ops->setsockopt(sk, level, optname,
  					     optval, optlen);
  }

  EXPORT_SYMBOL_GPL(inet_csk_compat_setsockopt);
  #endif

  
  static struct dst_entry *inet_csk_rebuild_route(struct sock *sk, struct flowi *fl)
  {

  	const struct inet_sock *inet = inet_sk(sk);
  	const struct ip_options_rcu *inet_opt;

  	__be32 daddr = inet->inet_daddr;
  	struct flowi4 *fl4;
  	struct rtable *rt;
  
  	rcu_read_lock();
  	inet_opt = rcu_dereference(inet->inet_opt);
  	if (inet_opt && inet_opt->opt.srr)
  		daddr = inet_opt->opt.faddr;
  	fl4 = &fl->u.ip4;
  	rt = ip_route_output_ports(sock_net(sk), fl4, sk, daddr,
  				   inet->inet_saddr, inet->inet_dport,
  				   inet->inet_sport, sk->sk_protocol,
  				   RT_CONN_FLAGS(sk), sk->sk_bound_dev_if);
  	if (IS_ERR(rt))
  		rt = NULL;
  	if (rt)
  		sk_setup_caps(sk, &rt->dst);
  	rcu_read_unlock();
  
  	return &rt->dst;
  }
  
  struct dst_entry *inet_csk_update_pmtu(struct sock *sk, u32 mtu)
  {
  	struct dst_entry *dst = __sk_dst_check(sk, 0);
  	struct inet_sock *inet = inet_sk(sk);
  
  	if (!dst) {
  		dst = inet_csk_rebuild_route(sk, &inet->cork.fl);
  		if (!dst)
  			goto out;
  	}

  	dst->ops->update_pmtu(dst, sk, NULL, mtu);

  
  	dst = __sk_dst_check(sk, 0);
  	if (!dst)
  		dst = inet_csk_rebuild_route(sk, &inet->cork.fl);
  out:
  	return dst;
  }
  EXPORT_SYMBOL_GPL(inet_csk_update_pmtu);