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 EXPORT_SYMBOL(sysctl_max_syn_backlog);
  37
  38 int reqsk_queue_alloc(struct request_sock_queue *queue,
  39                       unsigned int nr_table_entries)
  40 {
  41         size_t lopt_size = sizeof(struct listen_sock);
  42         struct listen_sock *lopt;
  43
  44         nr_table_entries = min_t(u32, nr_table_entries, sysctl_max_syn_backlog);
  45         nr_table_entries = max_t(u32, nr_table_entries, 8);
  46         nr_table_entries = roundup_pow_of_two(nr_table_entries + 1);
  47         lopt_size += nr_table_entries * sizeof(struct request_sock *);
  48         if (lopt_size > PAGE_SIZE)
  49                 lopt = vzalloc(lopt_size);
  50         else
  51                 lopt = kzalloc(lopt_size, GFP_KERNEL);
  52         if (lopt == NULL)
  53                 return -ENOMEM;
  54
  55         for (lopt->max_qlen_log = 3;
  56              (1 << lopt->max_qlen_log) < nr_table_entries;
  57              lopt->max_qlen_log++);
  58
  59         get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd));
  60         rwlock_init(&queue->syn_wait_lock);
  61         queue->rskq_accept_head = NULL;
  62         lopt->nr_table_entries = nr_table_entries;
  63
  64         write_lock_bh(&queue->syn_wait_lock);
  65         queue->listen_opt = lopt;
  66         write_unlock_bh(&queue->syn_wait_lock);
  67
  68         return 0;
  69 }
  70
  71 void __reqsk_queue_destroy(struct request_sock_queue *queue)
  72 {
  73         struct listen_sock *lopt;
  74         size_t lopt_size;
  75
  76         /*
  77          * this is an error recovery path only
  78          * no locking needed and the lopt is not NULL
  79          */
  80
  81         lopt = queue->listen_opt;
  82         lopt_size = sizeof(struct listen_sock) +
  83                 lopt->nr_table_entries * sizeof(struct request_sock *);
  84
  85         if (lopt_size > PAGE_SIZE)
  86                 vfree(lopt);
  87         else
  88                 kfree(lopt);
  89 }
  90
  91 static inline struct listen_sock *reqsk_queue_yank_listen_sk(
  92                 struct request_sock_queue *queue)
  93 {
  94         struct listen_sock *lopt;
  95
  96         write_lock_bh(&queue->syn_wait_lock);
  97         lopt = queue->listen_opt;
  98         queue->listen_opt = NULL;
  99         write_unlock_bh(&queue->syn_wait_lock);
 100
 101         return lopt;
 102 }
 103
 104 void reqsk_queue_destroy(struct request_sock_queue *queue)
 105 {
 106         /* make all the listen_opt local to us */
 107         struct listen_sock *lopt = reqsk_queue_yank_listen_sk(queue);
 108         size_t lopt_size = sizeof(struct listen_sock) +
 109                 lopt->nr_table_entries * sizeof(struct request_sock *);
 110
 111         if (lopt->qlen != 0) {
 112                 unsigned int i;
 113
 114                 for (i = 0; i < lopt->nr_table_entries; i++) {
 115                         struct request_sock *req;
 116
 117                         while ((req = lopt->syn_table[i]) != NULL) {
 118                                 lopt->syn_table[i] = req->dl_next;
 119                                 lopt->qlen--;
 120                                 reqsk_free(req);
 121                         }
 122                 }
 123         }
 124
 125         WARN_ON(lopt->qlen != 0);
 126         if (lopt_size > PAGE_SIZE)
 127                 vfree(lopt);
 128         else
 129                 kfree(lopt);
 130 }
 131