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 EXPORT_SYMBOL(sysctl_max_syn_backlog); 36 37 int 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 57 write_lock_bh(&queue->syn_wait_lock); 58 queue->listen_opt = lopt; 59 write_unlock_bh(&queue->syn_wait_lock); 60 61 return 0; 62 } 63 64 EXPORT_SYMBOL(reqsk_queue_alloc); 65