net/core/request_sock.c

   1 /*
   2  * NET          Generic infrastructure for Network protocols.
   3  *
   4  * Authors:     Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   5  *
   6  *              From code originally in include/net/tcp.h
   7  *
   8  *              This program is free software; you can redistribute it and/or
   9  *              modify it under the terms of the GNU General Public License
  10  *              as published by the Free Software Foundation; either version
  11  *              2 of the License, or (at your option) any later version.
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/random.h>
  16 #include <linux/slab.h>
  17 #include <linux/string.h>
  18
  19 #include <net/request_sock.h>
  20
  21 /*
  22  * Maximum number of SYN_RECV sockets in queue per LISTEN socket.
  23  * One SYN_RECV socket costs about 80bytes on a 32bit machine.
  24  * It would be better to replace it with a global counter for all sockets
  25  * but then some measure against one socket starving all other sockets
  26  * would be needed.
  27  *
  28  * It was 128 by default. Experiments with real servers show, that
  29  * it is absolutely not enough even at 100conn/sec. 256 cures most
  30  * of problems. This value is adjusted to 128 for very small machines
  31  * (<=32Mb of memory) and to 1024 on normal or better ones (>=256Mb).
  32  * Further increasing requires to change hash table size.
  33  */
  34 int sysctl_max_syn_backlog = 256;
  35
  36 int reqsk_queue_alloc(struct request_sock_queue *queue,
  37                       const int nr_table_entries)
  38 {
  39         const int lopt_size = sizeof(struct listen_sock) +
  40                               nr_table_entries * sizeof(struct request_sock *);
  41         struct listen_sock *lopt = kmalloc(lopt_size, GFP_KERNEL);
  42
  43         if (lopt == NULL)
  44                 return -ENOMEM;
  45
  46         memset(lopt, 0, lopt_size);
  47
  48         for (lopt->max_qlen_log = 6;
  49              (1 << lopt->max_qlen_log) < sysctl_max_syn_backlog;
  50              lopt->max_qlen_log++);
  51
  52         get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd));
  53         rwlock_init(&queue->syn_wait_lock);
  54         queue->rskq_accept_head = queue->rskq_accept_head = NULL;
  55         queue->rskq_defer_accept = 0;
  56         lopt->nr_table_entries = nr_table_entries;
  57
  58         write_lock_bh(&queue->syn_wait_lock);
  59         queue->listen_opt = lopt;
  60         write_unlock_bh(&queue->syn_wait_lock);
  61
  62         return 0;
  63 }
  64
  65 EXPORT_SYMBOL(reqsk_queue_alloc);
  66
  67 void reqsk_queue_destroy(struct request_sock_queue *queue)
  68 {
  69         /* make all the listen_opt local to us */
  70         struct listen_sock *lopt = reqsk_queue_yank_listen_sk(queue);
  71
  72         if (lopt->qlen != 0) {
  73                 int i;
  74
  75                 for (i = 0; i < lopt->nr_table_entries; i++) {
  76                         struct request_sock *req;
  77
  78                         while ((req = lopt->syn_table[i]) != NULL) {
  79                                 lopt->syn_table[i] = req->dl_next;
  80                                 lopt->qlen--;
  81                                 reqsk_free(req);
  82                         }
  83                 }
  84         }
  85
  86         BUG_TRAP(lopt->qlen == 0);
  87         kfree(lopt);
  88 }
  89
  90 EXPORT_SYMBOL(reqsk_queue_destroy);