request_sock.c revision dab6ba36888a12f3e3edff71eeef968fc159178a 
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 */
35int sysctl_max_syn_backlog = 256;
36
37int 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
72EXPORT_SYMBOL(reqsk_queue_alloc);
73
74void __reqsk_queue_destroy(struct request_sock_queue *queue)
75{
76	struct listen_sock *lopt;
77	size_t lopt_size;
78
79	/*
80	 * this is an error recovery path only
81	 * no locking needed and the lopt is not NULL
82	 */
83
84	lopt = queue->listen_opt;
85	lopt_size = sizeof(struct listen_sock) +
86		lopt->nr_table_entries * sizeof(struct request_sock *);
87
88	if (lopt_size > PAGE_SIZE)
89		vfree(lopt);
90	else
91		kfree(lopt);
92}
93
94EXPORT_SYMBOL(__reqsk_queue_destroy);
95
96static inline struct listen_sock *reqsk_queue_yank_listen_sk(
97		struct request_sock_queue *queue)
98{
99	struct listen_sock *lopt;
100
101	write_lock_bh(&queue->syn_wait_lock);
102	lopt = queue->listen_opt;
103	queue->listen_opt = NULL;
104	write_unlock_bh(&queue->syn_wait_lock);
105
106	return lopt;
107}
108
109void reqsk_queue_destroy(struct request_sock_queue *queue)
110{
111	/* make all the listen_opt local to us */
112	struct listen_sock *lopt = reqsk_queue_yank_listen_sk(queue);
113	size_t lopt_size = sizeof(struct listen_sock) +
114		lopt->nr_table_entries * sizeof(struct request_sock *);
115
116	if (lopt->qlen != 0) {
117		unsigned int i;
118
119		for (i = 0; i < lopt->nr_table_entries; i++) {
120			struct request_sock *req;
121
122			while ((req = lopt->syn_table[i]) != NULL) {
123				lopt->syn_table[i] = req->dl_next;
124				lopt->qlen--;
125				reqsk_free(req);
126			}
127		}
128	}
129
130	BUG_TRAP(lopt->qlen == 0);
131	if (lopt_size > PAGE_SIZE)
132		vfree(lopt);
133	else
134		kfree(lopt);
135}
136
137EXPORT_SYMBOL(reqsk_queue_destroy);
138