/*
   * NET		Generic infrastructure for Network protocols.
   *
   * Authors:	Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   *
   * 		From code originally in include/net/tcp.h
   *
   *		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/random.h>
  #include <linux/slab.h>
  #include <linux/string.h>

  #include <linux/vmalloc.h>

  
  #include <net/request_sock.h>

  /*
   * Maximum number of SYN_RECV sockets in queue per LISTEN socket.
   * One SYN_RECV socket costs about 80bytes on a 32bit machine.
   * It would be better to replace it with a global counter for all sockets
   * but then some measure against one socket starving all other sockets
   * would be needed.
   *

   * The minimum value of it is 128. Experiments with real servers show that

   * it is absolutely not enough even at 100conn/sec. 256 cures most

   * of problems.
   * This value is adjusted to 128 for low memory machines,
   * and it will increase in proportion to the memory of machine.

   * Note : Dont forget somaxconn that may limit backlog too.

   */
  int sysctl_max_syn_backlog = 256;

  EXPORT_SYMBOL(sysctl_max_syn_backlog);

  int reqsk_queue_alloc(struct request_sock_queue *queue,

  		      unsigned int nr_table_entries)

  {

  	size_t lopt_size = sizeof(struct listen_sock);
  	struct listen_sock *lopt;
  
  	nr_table_entries = min_t(u32, nr_table_entries, sysctl_max_syn_backlog);
  	nr_table_entries = max_t(u32, nr_table_entries, 8);
  	nr_table_entries = roundup_pow_of_two(nr_table_entries + 1);
  	lopt_size += nr_table_entries * sizeof(struct request_sock *);
  	if (lopt_size > PAGE_SIZE)

  		lopt = vzalloc(lopt_size);

  	else
  		lopt = kzalloc(lopt_size, GFP_KERNEL);

  	if (lopt == NULL)
  		return -ENOMEM;

  	for (lopt->max_qlen_log = 3;
  	     (1 << lopt->max_qlen_log) < nr_table_entries;

  	     lopt->max_qlen_log++);
  
  	get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd));
  	rwlock_init(&queue->syn_wait_lock);

  	queue->rskq_accept_head = NULL;

  	lopt->nr_table_entries = nr_table_entries;

  
  	write_lock_bh(&queue->syn_wait_lock);
  	queue->listen_opt = lopt;
  	write_unlock_bh(&queue->syn_wait_lock);
  
  	return 0;
  }

  void __reqsk_queue_destroy(struct request_sock_queue *queue)
  {
  	struct listen_sock *lopt;
  	size_t lopt_size;
  
  	/*
  	 * this is an error recovery path only
  	 * no locking needed and the lopt is not NULL
  	 */
  
  	lopt = queue->listen_opt;
  	lopt_size = sizeof(struct listen_sock) +
  		lopt->nr_table_entries * sizeof(struct request_sock *);
  
  	if (lopt_size > PAGE_SIZE)
  		vfree(lopt);
  	else
  		kfree(lopt);
  }

  static inline struct listen_sock *reqsk_queue_yank_listen_sk(
  		struct request_sock_queue *queue)
  {
  	struct listen_sock *lopt;
  
  	write_lock_bh(&queue->syn_wait_lock);
  	lopt = queue->listen_opt;
  	queue->listen_opt = NULL;
  	write_unlock_bh(&queue->syn_wait_lock);
  
  	return lopt;
  }

  void reqsk_queue_destroy(struct request_sock_queue *queue)
  {
  	/* make all the listen_opt local to us */
  	struct listen_sock *lopt = reqsk_queue_yank_listen_sk(queue);

  	size_t lopt_size = sizeof(struct listen_sock) +
  		lopt->nr_table_entries * sizeof(struct request_sock *);

  
  	if (lopt->qlen != 0) {

  		unsigned int i;

  
  		for (i = 0; i < lopt->nr_table_entries; i++) {
  			struct request_sock *req;
  
  			while ((req = lopt->syn_table[i]) != NULL) {
  				lopt->syn_table[i] = req->dl_next;
  				lopt->qlen--;
  				reqsk_free(req);
  			}
  		}
  	}

  	WARN_ON(lopt->qlen != 0);

  	if (lopt_size > PAGE_SIZE)
  		vfree(lopt);
  	else
  		kfree(lopt);

  }