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 36 int reqsk_queue_alloc(struct request_sock_queue *queue, 37 const int nr_table_entries) 38 { 39 const int lopt_size = sizeof(struct listen_sock) + 40 nr_table_entries * sizeof(struct request_sock *); 41 struct listen_sock *lopt = kzalloc(lopt_size, GFP_KERNEL); 42 43 if (lopt == NULL) 44 return -ENOMEM; 45 46 for (lopt->max_qlen_log = 6; 47 (1 << lopt->max_qlen_log) < sysctl_max_syn_backlog; 48 lopt->max_qlen_log++); 49 50 get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd)); 51 rwlock_init(&queue->syn_wait_lock); 52 queue->rskq_accept_head = NULL; 53 lopt->nr_table_entries = nr_table_entries; 54 55 write_lock_bh(&queue->syn_wait_lock); 56 queue->listen_opt = lopt; 57 write_unlock_bh(&queue->syn_wait_lock); 58 59 return 0; 60 } 61 62 EXPORT_SYMBOL(reqsk_queue_alloc); 63 64 void reqsk_queue_destroy(struct request_sock_queue *queue) 65 { 66 /* make all the listen_opt local to us */ 67 struct listen_sock *lopt = reqsk_queue_yank_listen_sk(queue); 68 69 if (lopt->qlen != 0) { 70 int i; 71 72 for (i = 0; i < lopt->nr_table_entries; i++) { 73 struct request_sock *req; 74 75 while ((req = lopt->syn_table[i]) != NULL) { 76 lopt->syn_table[i] = req->dl_next; 77 lopt->qlen--; 78 reqsk_free(req); 79 } 80 } 81 } 82 83 BUG_TRAP(lopt->qlen == 0); 84 kfree(lopt); 85 } 86 87 EXPORT_SYMBOL(reqsk_queue_destroy); 88