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 37 int 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 72 EXPORT_SYMBOL(reqsk_queue_alloc); 73 74 void __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 94 EXPORT_SYMBOL(__reqsk_queue_destroy); 95 96 static 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 } 108 109 void 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 } 136 137 EXPORT_SYMBOL(reqsk_queue_destroy); 138