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 } 131 132