request_sock.c revision 83e3609eba3818f6e18b8bf9442195169ac306b7 
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 */
34int sysctl_max_syn_backlog = 256;
35EXPORT_SYMBOL(sysctl_max_syn_backlog);
36
37int reqsk_queue_alloc(struct request_sock_queue *queue,
38		      const int nr_table_entries)
39{
40	const int lopt_size = sizeof(struct listen_sock) +
41			      nr_table_entries * sizeof(struct request_sock *);
42	struct listen_sock *lopt = kmalloc(lopt_size, GFP_KERNEL);
43
44	if (lopt == NULL)
45		return -ENOMEM;
46
47	memset(lopt, 0, lopt_size);
48
49	for (lopt->max_qlen_log = 6;
50	     (1 << lopt->max_qlen_log) < sysctl_max_syn_backlog;
51	     lopt->max_qlen_log++);
52
53	get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd));
54	rwlock_init(&queue->syn_wait_lock);
55	queue->rskq_accept_head = queue->rskq_accept_head = NULL;
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
65EXPORT_SYMBOL(reqsk_queue_alloc);
66
67void 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
90EXPORT_SYMBOL(reqsk_queue_destroy);
91