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 #include <linux/vmalloc.h>
  19
  20 #include <net/request_sock.h>
  21
  22 /*
  23  * Maximum number of SYN_RECV sockets in queue per LISTEN socket.
  24  * One SYN_RECV socket costs about 80bytes on a 32bit machine.
  25  * It would be better to replace it with a global counter for all sockets
  26  * but then some measure against one socket starving all other sockets
  27  * would be needed.
  28  *
  29  * It was 128 by default. Experiments with real servers show, that
  30  * it is absolutely not enough even at 100conn/sec. 256 cures most
  31  * of problems. This value is adjusted to 128 for very small machines
  32  * (<=32Mb of memory) and to 1024 on normal or better ones (>=256Mb).
  33  * Note : Dont forget somaxconn that may limit backlog too.
  34  */
  35 int sysctl_max_syn_backlog = 256;
  36
  37 int reqsk_queue_alloc(struct request_sock_queue *queue,
  38                       unsigned int nr_table_entries)
  39 {
  40         size_t lopt_size = sizeof(struct listen_sock);
  41         struct listen_sock *lopt;
  42
  43         nr_table_entries = min_t(u32, nr_table_entries, sysctl_max_syn_backlog);
  44         nr_table_entries = max_t(u32, nr_table_entries, 8);
  45         nr_table_entries = roundup_pow_of_two(nr_table_entries + 1);
  46         lopt_size += nr_table_entries * sizeof(struct request_sock *);
  47         if (lopt_size > PAGE_SIZE)
  48                 lopt = __vmalloc(lopt_size,
  49                         GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
  50                         PAGE_KERNEL);
  51         else
  52                 lopt = kzalloc(lopt_size, GFP_KERNEL);
  53         if (lopt == NULL)
  54                 return -ENOMEM;
  55
  56         for (lopt->max_qlen_log = 3;
  57              (1 << lopt->max_qlen_log) < nr_table_entries;
  58              lopt->max_qlen_log++);
  59
  60         get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd));
  61         rwlock_init(&queue->syn_wait_lock);
  62         queue->rskq_accept_head = NULL;
  63         lopt->nr_table_entries = nr_table_entries;
  64
  65         write_lock_bh(&queue->syn_wait_lock);
  66         queue->listen_opt = lopt;
  67         write_unlock_bh(&queue->syn_wait_lock);
  68
  69         return 0;
  70 }
  71
  72 void __reqsk_queue_destroy(struct request_sock_queue *queue)
  73 {
  74         struct listen_sock *lopt;
  75         size_t lopt_size;
  76
  77         /*
  78          * this is an error recovery path only
  79          * no locking needed and the lopt is not NULL
  80          */
  81
  82         lopt = queue->listen_opt;
  83         lopt_size = sizeof(struct listen_sock) +
  84                 lopt->nr_table_entries * sizeof(struct request_sock *);
  85
  86         if (lopt_size > PAGE_SIZE)
  87                 vfree(lopt);
  88         else
  89                 kfree(lopt);
  90 }
  91
  92 static inline struct listen_sock *reqsk_queue_yank_listen_sk(
  93                 struct request_sock_queue *queue)
  94 {
  95         struct listen_sock *lopt;
  96
  97         write_lock_bh(&queue->syn_wait_lock);
  98         lopt = queue->listen_opt;
  99         queue->listen_opt = NULL;
 100         write_unlock_bh(&queue->syn_wait_lock);
 101
 102         return lopt;
 103 }
 104
 105 void reqsk_queue_destroy(struct request_sock_queue *queue)
 106 {
 107         /* make all the listen_opt local to us */
 108         struct listen_sock *lopt = reqsk_queue_yank_listen_sk(queue);
 109         size_t lopt_size = sizeof(struct listen_sock) +
 110                 lopt->nr_table_entries * sizeof(struct request_sock *);
 111
 112         if (lopt->qlen != 0) {
 113                 unsigned int i;
 114
 115                 for (i = 0; i < lopt->nr_table_entries; i++) {
 116                         struct request_sock *req;
 117
 118                         while ((req = lopt->syn_table[i]) != NULL) {
 119                                 lopt->syn_table[i] = req->dl_next;
 120                                 lopt->qlen--;
 121                                 reqsk_free(req);
 122                         }
 123                 }
 124         }
 125
 126         BUG_TRAP(lopt->qlen == 0);
 127         if (lopt_size > PAGE_SIZE)
 128                 vfree(lopt);
 129         else
 130                 kfree(lopt);
 131 }
 132