ar-transport.c

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/* RxRPC point-to-point transport session management
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * 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/net.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include "ar-internal.h"

static void rxrpc_transport_reaper(struct work_struct *work);

static LIST_HEAD(rxrpc_transports);
static DEFINE_RWLOCK(rxrpc_transport_lock);
static unsigned long rxrpc_transport_timeout = 3600 * 24;
static DECLARE_DELAYED_WORK(rxrpc_transport_reap, rxrpc_transport_reaper);

/*
 * allocate a new transport session manager
 */
static struct rxrpc_transport *rxrpc_alloc_transport(struct rxrpc_local *local,
                             struct rxrpc_peer *peer,
                             gfp_t gfp)
{
    struct rxrpc_transport *trans;

    _enter("");

    trans = kzalloc(sizeof(struct rxrpc_transport), gfp);
    if (trans) {
        trans->local = local;
        trans->peer = peer;
        INIT_LIST_HEAD(&trans->link);
        trans->bundles = RB_ROOT;
        trans->client_conns = RB_ROOT;
        trans->server_conns = RB_ROOT;
        skb_queue_head_init(&trans->error_queue);
        spin_lock_init(&trans->client_lock);
        rwlock_init(&trans->conn_lock);
        atomic_set(&trans->usage, 1);
        trans->debug_id = atomic_inc_return(&rxrpc_debug_id);

        if (peer->srx.transport.family == AF_INET) {
            switch (peer->srx.transport_type) {
            case SOCK_DGRAM:
                INIT_WORK(&trans->error_handler,
                      rxrpc_UDP_error_handler);
                break;
            default:
                BUG();
                break;
            }
        } else {
            BUG();
        }
    }

    _leave(" = %p", trans);
    return trans;
}

/*
 * obtain a transport session for the nominated endpoints
 */
struct rxrpc_transport *rxrpc_get_transport(struct rxrpc_local *local,
                        struct rxrpc_peer *peer,
                        gfp_t gfp)
{
    struct rxrpc_transport *trans, *candidate;
    const char *new = "old";
    int usage;

    _enter("{%pI4+%hu},{%pI4+%hu},",
           &local->srx.transport.sin.sin_addr,
           ntohs(local->srx.transport.sin.sin_port),
           &peer->srx.transport.sin.sin_addr,
           ntohs(peer->srx.transport.sin.sin_port));

    /* search the transport list first */
    read_lock_bh(&rxrpc_transport_lock);
    list_for_each_entry(trans, &rxrpc_transports, link) {
        if (trans->local == local && trans->peer == peer)
            goto found_extant_transport;
    }
    read_unlock_bh(&rxrpc_transport_lock);

    /* not yet present - create a candidate for a new record and then
     * redo the search */
    candidate = rxrpc_alloc_transport(local, peer, gfp);
    if (!candidate) {
        _leave(" = -ENOMEM");
        return ERR_PTR(-ENOMEM);
    }

    write_lock_bh(&rxrpc_transport_lock);

    list_for_each_entry(trans, &rxrpc_transports, link) {
        if (trans->local == local && trans->peer == peer)
            goto found_extant_second;
    }

    /* we can now add the new candidate to the list */
    trans = candidate;
    candidate = NULL;
    usage = atomic_read(&trans->usage);

    rxrpc_get_local(trans->local);
    atomic_inc(&trans->peer->usage);
    list_add_tail(&trans->link, &rxrpc_transports);
    write_unlock_bh(&rxrpc_transport_lock);
    new = "new";

success:
    _net("TRANSPORT %s %d local %d -> peer %d",
         new,
         trans->debug_id,
         trans->local->debug_id,
         trans->peer->debug_id);

    _leave(" = %p {u=%d}", trans, usage);
    return trans;

    /* we found the transport in the list immediately */
found_extant_transport:
    usage = atomic_inc_return(&trans->usage);
    read_unlock_bh(&rxrpc_transport_lock);
    goto success;

    /* we found the transport on the second time through the list */
found_extant_second:
    usage = atomic_inc_return(&trans->usage);
    write_unlock_bh(&rxrpc_transport_lock);
    kfree(candidate);
    goto success;
}

/*
 * find the transport connecting two endpoints
 */
struct rxrpc_transport *rxrpc_find_transport(struct rxrpc_local *local,
                         struct rxrpc_peer *peer)
{
    struct rxrpc_transport *trans;

    _enter("{%pI4+%hu},{%pI4+%hu},",
           &local->srx.transport.sin.sin_addr,
           ntohs(local->srx.transport.sin.sin_port),
           &peer->srx.transport.sin.sin_addr,
           ntohs(peer->srx.transport.sin.sin_port));

    /* search the transport list */
    read_lock_bh(&rxrpc_transport_lock);

    list_for_each_entry(trans, &rxrpc_transports, link) {
        if (trans->local == local && trans->peer == peer)
            goto found_extant_transport;
    }

    read_unlock_bh(&rxrpc_transport_lock);
    _leave(" = NULL");
    return NULL;

found_extant_transport:
    atomic_inc(&trans->usage);
    read_unlock_bh(&rxrpc_transport_lock);
    _leave(" = %p", trans);
    return trans;
}

/*
 * release a transport session
 */
void rxrpc_put_transport(struct rxrpc_transport *trans)
{
    _enter("%p{u=%d}", trans, atomic_read(&trans->usage));

    ASSERTCMP(atomic_read(&trans->usage), >, 0);

    trans->put_time = get_seconds();
    if (unlikely(atomic_dec_and_test(&trans->usage))) {
        _debug("zombie");
        /* let the reaper determine the timeout to avoid a race with
         * overextending the timeout if the reaper is running at the
         * same time */
        rxrpc_queue_delayed_work(&rxrpc_transport_reap, 0);
    }
    _leave("");
}

/*
 * clean up a transport session
 */
static void rxrpc_cleanup_transport(struct rxrpc_transport *trans)
{
    _net("DESTROY TRANS %d", trans->debug_id);

    rxrpc_purge_queue(&trans->error_queue);

    rxrpc_put_local(trans->local);
    rxrpc_put_peer(trans->peer);
    kfree(trans);
}

/*
 * reap dead transports that have passed their expiry date
 */
static void rxrpc_transport_reaper(struct work_struct *work)
{
    struct rxrpc_transport *trans, *_p;
    unsigned long now, earliest, reap_time;

    LIST_HEAD(graveyard);

    _enter("");

    now = get_seconds();
    earliest = ULONG_MAX;

    /* extract all the transports that have been dead too long */
    write_lock_bh(&rxrpc_transport_lock);
    list_for_each_entry_safe(trans, _p, &rxrpc_transports, link) {
        _debug("reap TRANS %d { u=%d t=%ld }",
               trans->debug_id, atomic_read(&trans->usage),
               (long) now - (long) trans->put_time);

        if (likely(atomic_read(&trans->usage) > 0))
            continue;

        reap_time = trans->put_time + rxrpc_transport_timeout;
        if (reap_time <= now)
            list_move_tail(&trans->link, &graveyard);
        else if (reap_time < earliest)
            earliest = reap_time;
    }
    write_unlock_bh(&rxrpc_transport_lock);

    if (earliest != ULONG_MAX) {
        _debug("reschedule reaper %ld", (long) earliest - now);
        ASSERTCMP(earliest, >, now);
        rxrpc_queue_delayed_work(&rxrpc_transport_reap,
                     (earliest - now) * HZ);
    }

    /* then destroy all those pulled out */
    while (!list_empty(&graveyard)) {
        trans = list_entry(graveyard.next, struct rxrpc_transport,
                   link);
        list_del_init(&trans->link);

        ASSERTCMP(atomic_read(&trans->usage), ==, 0);
        rxrpc_cleanup_transport(trans);
    }

    _leave("");
}

/*
 * preemptively destroy all the transport session records rather than waiting
 * for them to time out
 */
void __exit rxrpc_destroy_all_transports(void)
{
    _enter("");

    rxrpc_transport_timeout = 0;
    cancel_delayed_work(&rxrpc_transport_reap);
    rxrpc_queue_delayed_work(&rxrpc_transport_reap, 0);

    _leave("");
}