root/net/core/request_sock.c

DEFINITIONS

1. reqsk_queue_alloc
2. __reqsk_queue_destroy
3. reqsk_queue_yank_listen_sk
4. reqsk_queue_destroy

/*
 * 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;
}

void __reqsk_queue_destroy(struct request_sock_queue *queue)
{
        struct listen_sock *lopt;
        size_t lopt_size;

        /*
         * this is an error recovery path only
         * no locking needed and the lopt is not NULL
         */

        lopt = queue->listen_opt;
        lopt_size = sizeof(struct listen_sock) +
                lopt->nr_table_entries * sizeof(struct request_sock *);

        if (lopt_size > PAGE_SIZE)
                vfree(lopt);
        else
                kfree(lopt);
}

static inline struct listen_sock *reqsk_queue_yank_listen_sk(
                struct request_sock_queue *queue)
{
        struct listen_sock *lopt;

        write_lock_bh(&queue->syn_wait_lock);
        lopt = queue->listen_opt;
        queue->listen_opt = NULL;
        write_unlock_bh(&queue->syn_wait_lock);

        return lopt;
}

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);
                        }
                }
        }

        WARN_ON(lopt->qlen != 0);
        if (lopt_size > PAGE_SIZE)
                vfree(lopt);
        else
                kfree(lopt);
}