/* * NET		Generic infrastructure for Network protocols. * * Authors:	Arnaldo Carvalho de Melo <acme@conectiva.com.br> * * 		From code originally in include/net/tcp.h * *		This program is free software; you can redistribute it and/or *		modify it under the terms of the GNU General Public License *		as published by the Free Software Foundation; either version *		2 of the License, or (at your option) any later version. */ #include <linux/module.h>#include <linux/random.h>#include <linux/slab.h>#include <linux/string.h>#include <linux/vmalloc.h> #include <net/request_sock.h> /* * Maximum number of SYN_RECV sockets in queue per LISTEN socket. * One SYN_RECV socket costs about 80bytes on a 32bit machine. * It would be better to replace it with a global counter for all sockets * but then some measure against one socket starving all other sockets * would be needed. * * It was 128 by default. Experiments with real servers show, that * it is absolutely not enough even at 100conn/sec. 256 cures most * of problems. This value is adjusted to 128 for very small machines * (<=32Mb of memory) and to 1024 on normal or better ones (>=256Mb). * Note : Dont forget somaxconn that may limit backlog too. */int sysctl_max_syn_backlog = 256; int reqsk_queue_alloc(struct request_sock_queue *queue,		      unsigned int nr_table_entries){	size_t lopt_size = sizeof(struct listen_sock);	struct listen_sock *lopt; 	nr_table_entries = min_t(u32, nr_table_entries, sysctl_max_syn_backlog);	nr_table_entries = max_t(u32, nr_table_entries, 8);	nr_table_entries = roundup_pow_of_two(nr_table_entries + 1);	lopt_size += nr_table_entries * sizeof(struct request_sock *);	if (lopt_size > PAGE_SIZE)		lopt = __vmalloc(lopt_size,			GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,			PAGE_KERNEL);	else		lopt = kzalloc(lopt_size, GFP_KERNEL);	if (lopt == NULL)		return -ENOMEM; 	for (lopt->max_qlen_log = 3;	     (1 << lopt->max_qlen_log) < nr_table_entries;	     lopt->max_qlen_log++); 	get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd));	rwlock_init(&queue->syn_wait_lock);	queue->rskq_accept_head = NULL;	lopt->nr_table_entries = nr_table_entries; 	write_lock_bh(&queue->syn_wait_lock);	queue->listen_opt = lopt;	write_unlock_bh(&queue->syn_wait_lock); 	return 0;} EXPORT_SYMBOL(reqsk_queue_alloc); void reqsk_queue_destroy(struct request_sock_queue *queue){	/* make all the listen_opt local to us */	struct listen_sock *lopt = reqsk_queue_yank_listen_sk(queue);	size_t lopt_size = sizeof(struct listen_sock) +		lopt->nr_table_entries * sizeof(struct request_sock *); 	if (lopt->qlen != 0) {		unsigned int i; 		for (i = 0; i < lopt->nr_table_entries; i++) {			struct request_sock *req; 			while ((req = lopt->syn_table[i]) != NULL) {				lopt->syn_table[i] = req->dl_next;				lopt->qlen--;				reqsk_free(req);			}		}	} 	BUG_TRAP(lopt->qlen == 0);	if (lopt_size > PAGE_SIZE)		vfree(lopt);	else		kfree(lopt);} EXPORT_SYMBOL(reqsk_queue_destroy);