ar-peer.c

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/* RxRPC remote transport endpoint 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/udp.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/icmp.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include <net/ip.h>
#include <net/route.h>
#include "ar-internal.h"

static LIST_HEAD(rxrpc_peers);
static DEFINE_RWLOCK(rxrpc_peer_lock);
static DECLARE_WAIT_QUEUE_HEAD(rxrpc_peer_wq);

static void rxrpc_destroy_peer(struct work_struct *work);

/*
 * assess the MTU size for the network interface through which this peer is
 * reached
 */
static void rxrpc_assess_MTU_size(struct rxrpc_peer *peer)
{
    struct rtable *rt;
    struct flowi4 fl4;

    peer->if_mtu = 1500;

    rt = ip_route_output_ports(&init_net, &fl4, NULL,
                   peer->srx.transport.sin.sin_addr.s_addr, 0,
                   htons(7000), htons(7001),
                   IPPROTO_UDP, 0, 0);
    if (IS_ERR(rt)) {
        _leave(" [route err %ld]", PTR_ERR(rt));
        return;
    }

    peer->if_mtu = dst_mtu(&rt->dst);
    dst_release(&rt->dst);

    _leave(" [if_mtu %u]", peer->if_mtu);
}

/*
 * allocate a new peer
 */
static struct rxrpc_peer *rxrpc_alloc_peer(struct sockaddr_rxrpc *srx,
                       gfp_t gfp)
{
    struct rxrpc_peer *peer;

    _enter("");

    peer = kzalloc(sizeof(struct rxrpc_peer), gfp);
    if (peer) {
        INIT_WORK(&peer->destroyer, &rxrpc_destroy_peer);
        INIT_LIST_HEAD(&peer->link);
        INIT_LIST_HEAD(&peer->error_targets);
        spin_lock_init(&peer->lock);
        atomic_set(&peer->usage, 1);
        peer->debug_id = atomic_inc_return(&rxrpc_debug_id);
        memcpy(&peer->srx, srx, sizeof(*srx));

        rxrpc_assess_MTU_size(peer);
        peer->mtu = peer->if_mtu;

        if (srx->transport.family == AF_INET) {
            peer->hdrsize = sizeof(struct iphdr);
            switch (srx->transport_type) {
            case SOCK_DGRAM:
                peer->hdrsize += sizeof(struct udphdr);
                break;
            default:
                BUG();
                break;
            }
        } else {
            BUG();
        }

        peer->hdrsize += sizeof(struct rxrpc_header);
        peer->maxdata = peer->mtu - peer->hdrsize;
    }

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

/*
 * obtain a remote transport endpoint for the specified address
 */
struct rxrpc_peer *rxrpc_get_peer(struct sockaddr_rxrpc *srx, gfp_t gfp)
{
    struct rxrpc_peer *peer, *candidate;
    const char *new = "old";
    int usage;

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

    /* search the peer list first */
    read_lock_bh(&rxrpc_peer_lock);
    list_for_each_entry(peer, &rxrpc_peers, link) {
        _debug("check PEER %d { u=%d t=%d l=%d }",
               peer->debug_id,
               atomic_read(&peer->usage),
               peer->srx.transport_type,
               peer->srx.transport_len);

        if (atomic_read(&peer->usage) > 0 &&
            peer->srx.transport_type == srx->transport_type &&
            peer->srx.transport_len == srx->transport_len &&
            memcmp(&peer->srx.transport,
               &srx->transport,
               srx->transport_len) == 0)
            goto found_extant_peer;
    }
    read_unlock_bh(&rxrpc_peer_lock);

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

    write_lock_bh(&rxrpc_peer_lock);

    list_for_each_entry(peer, &rxrpc_peers, link) {
        if (atomic_read(&peer->usage) > 0 &&
            peer->srx.transport_type == srx->transport_type &&
            peer->srx.transport_len == srx->transport_len &&
            memcmp(&peer->srx.transport,
               &srx->transport,
               srx->transport_len) == 0)
            goto found_extant_second;
    }

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

    list_add_tail(&peer->link, &rxrpc_peers);
    write_unlock_bh(&rxrpc_peer_lock);
    new = "new";

success:
    _net("PEER %s %d {%d,%u,%pI4+%hu}",
         new,
         peer->debug_id,
         peer->srx.transport_type,
         peer->srx.transport.family,
         &peer->srx.transport.sin.sin_addr,
         ntohs(peer->srx.transport.sin.sin_port));

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

    /* we found the peer in the list immediately */
found_extant_peer:
    usage = atomic_inc_return(&peer->usage);
    read_unlock_bh(&rxrpc_peer_lock);
    goto success;

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

/*
 * find the peer associated with a packet
 */
struct rxrpc_peer *rxrpc_find_peer(struct rxrpc_local *local,
                   __be32 addr, __be16 port)
{
    struct rxrpc_peer *peer;

    _enter("");

    /* search the peer list */
    read_lock_bh(&rxrpc_peer_lock);

    if (local->srx.transport.family == AF_INET &&
        local->srx.transport_type == SOCK_DGRAM
        ) {
        list_for_each_entry(peer, &rxrpc_peers, link) {
            if (atomic_read(&peer->usage) > 0 &&
                peer->srx.transport_type == SOCK_DGRAM &&
                peer->srx.transport.family == AF_INET &&
                peer->srx.transport.sin.sin_port == port &&
                peer->srx.transport.sin.sin_addr.s_addr == addr)
                goto found_UDP_peer;
        }

        goto new_UDP_peer;
    }

    read_unlock_bh(&rxrpc_peer_lock);
    _leave(" = -EAFNOSUPPORT");
    return ERR_PTR(-EAFNOSUPPORT);

found_UDP_peer:
    _net("Rx UDP DGRAM from peer %d", peer->debug_id);
    atomic_inc(&peer->usage);
    read_unlock_bh(&rxrpc_peer_lock);
    _leave(" = %p", peer);
    return peer;

new_UDP_peer:
    _net("Rx UDP DGRAM from NEW peer");
    read_unlock_bh(&rxrpc_peer_lock);
    _leave(" = -EBUSY [new]");
    return ERR_PTR(-EBUSY);
}

/*
 * release a remote transport endpoint
 */
void rxrpc_put_peer(struct rxrpc_peer *peer)
{
    _enter("%p{u=%d}", peer, atomic_read(&peer->usage));

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

    if (likely(!atomic_dec_and_test(&peer->usage))) {
        _leave(" [in use]");
        return;
    }

    rxrpc_queue_work(&peer->destroyer);
    _leave("");
}

/*
 * destroy a remote transport endpoint
 */
static void rxrpc_destroy_peer(struct work_struct *work)
{
    struct rxrpc_peer *peer =
        container_of(work, struct rxrpc_peer, destroyer);

    _enter("%p{%d}", peer, atomic_read(&peer->usage));

    write_lock_bh(&rxrpc_peer_lock);
    list_del(&peer->link);
    write_unlock_bh(&rxrpc_peer_lock);

    _net("DESTROY PEER %d", peer->debug_id);
    kfree(peer);

    if (list_empty(&rxrpc_peers))
        wake_up_all(&rxrpc_peer_wq);
    _leave("");
}

/*
 * preemptively destroy all the peer records from a transport endpoint rather
 * than waiting for them to time out
 */
void __exit rxrpc_destroy_all_peers(void)
{
    DECLARE_WAITQUEUE(myself,current);

    _enter("");

    /* we simply have to wait for them to go away */
    if (!list_empty(&rxrpc_peers)) {
        set_current_state(TASK_UNINTERRUPTIBLE);
        add_wait_queue(&rxrpc_peer_wq, &myself);

        while (!list_empty(&rxrpc_peers)) {
            schedule();
            set_current_state(TASK_UNINTERRUPTIBLE);
        }

        remove_wait_queue(&rxrpc_peer_wq, &myself);
        set_current_state(TASK_RUNNING);
    }

    _leave("");
}