cf124db566
Network devices can allocate reasources and private memory using netdev_ops->ndo_init(). However, the release of these resources can occur in one of two different places. Either netdev_ops->ndo_uninit() or netdev->destructor(). The decision of which operation frees the resources depends upon whether it is necessary for all netdev refs to be released before it is safe to perform the freeing. netdev_ops->ndo_uninit() presumably can occur right after the NETDEV_UNREGISTER notifier completes and the unicast and multicast address lists are flushed. netdev->destructor(), on the other hand, does not run until the netdev references all go away. Further complicating the situation is that netdev->destructor() almost universally does also a free_netdev(). This creates a problem for the logic in register_netdevice(). Because all callers of register_netdevice() manage the freeing of the netdev, and invoke free_netdev(dev) if register_netdevice() fails. If netdev_ops->ndo_init() succeeds, but something else fails inside of register_netdevice(), it does call ndo_ops->ndo_uninit(). But it is not able to invoke netdev->destructor(). This is because netdev->destructor() will do a free_netdev() and then the caller of register_netdevice() will do the same. However, this means that the resources that would normally be released by netdev->destructor() will not be. Over the years drivers have added local hacks to deal with this, by invoking their destructor parts by hand when register_netdevice() fails. Many drivers do not try to deal with this, and instead we have leaks. Let's close this hole by formalizing the distinction between what private things need to be freed up by netdev->destructor() and whether the driver needs unregister_netdevice() to perform the free_netdev(). netdev->priv_destructor() performs all actions to free up the private resources that used to be freed by netdev->destructor(), except for free_netdev(). netdev->needs_free_netdev is a boolean that indicates whether free_netdev() should be done at the end of unregister_netdevice(). Now, register_netdevice() can sanely release all resources after ndo_ops->ndo_init() succeeds, by invoking both ndo_ops->ndo_uninit() and netdev->priv_destructor(). And at the end of unregister_netdevice(), we invoke netdev->priv_destructor() and optionally call free_netdev(). Signed-off-by: David S. Miller <davem@davemloft.net>
191 lines
5.3 KiB
C
191 lines
5.3 KiB
C
/*
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* vcan.c - Virtual CAN interface
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*
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* Copyright (c) 2002-2017 Volkswagen Group Electronic Research
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of Volkswagen nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* Alternatively, provided that this notice is retained in full, this
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* software may be distributed under the terms of the GNU General
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* Public License ("GPL") version 2, in which case the provisions of the
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* GPL apply INSTEAD OF those given above.
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*
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* The provided data structures and external interfaces from this code
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* are not restricted to be used by modules with a GPL compatible license.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/netdevice.h>
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#include <linux/if_arp.h>
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#include <linux/if_ether.h>
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#include <linux/can.h>
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#include <linux/can/dev.h>
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#include <linux/can/skb.h>
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#include <linux/slab.h>
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#include <net/rtnetlink.h>
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#define DRV_NAME "vcan"
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MODULE_DESCRIPTION("virtual CAN interface");
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MODULE_LICENSE("Dual BSD/GPL");
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MODULE_AUTHOR("Urs Thuermann <urs.thuermann@volkswagen.de>");
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MODULE_ALIAS_RTNL_LINK(DRV_NAME);
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/*
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* CAN test feature:
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* Enable the echo on driver level for testing the CAN core echo modes.
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* See Documentation/networking/can.txt for details.
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*/
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static bool echo; /* echo testing. Default: 0 (Off) */
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module_param(echo, bool, S_IRUGO);
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MODULE_PARM_DESC(echo, "Echo sent frames (for testing). Default: 0 (Off)");
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static void vcan_rx(struct sk_buff *skb, struct net_device *dev)
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{
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struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
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struct net_device_stats *stats = &dev->stats;
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stats->rx_packets++;
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stats->rx_bytes += cfd->len;
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skb->pkt_type = PACKET_BROADCAST;
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skb->dev = dev;
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skb->ip_summed = CHECKSUM_UNNECESSARY;
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netif_rx_ni(skb);
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}
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static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
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{
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struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
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struct net_device_stats *stats = &dev->stats;
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int loop;
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if (can_dropped_invalid_skb(dev, skb))
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return NETDEV_TX_OK;
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stats->tx_packets++;
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stats->tx_bytes += cfd->len;
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/* set flag whether this packet has to be looped back */
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loop = skb->pkt_type == PACKET_LOOPBACK;
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if (!echo) {
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/* no echo handling available inside this driver */
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if (loop) {
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/*
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* only count the packets here, because the
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* CAN core already did the echo for us
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*/
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stats->rx_packets++;
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stats->rx_bytes += cfd->len;
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}
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consume_skb(skb);
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return NETDEV_TX_OK;
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}
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/* perform standard echo handling for CAN network interfaces */
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if (loop) {
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skb = can_create_echo_skb(skb);
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if (!skb)
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return NETDEV_TX_OK;
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/* receive with packet counting */
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vcan_rx(skb, dev);
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} else {
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/* no looped packets => no counting */
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consume_skb(skb);
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}
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return NETDEV_TX_OK;
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}
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static int vcan_change_mtu(struct net_device *dev, int new_mtu)
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{
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/* Do not allow changing the MTU while running */
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if (dev->flags & IFF_UP)
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return -EBUSY;
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if (new_mtu != CAN_MTU && new_mtu != CANFD_MTU)
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return -EINVAL;
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dev->mtu = new_mtu;
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return 0;
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}
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static const struct net_device_ops vcan_netdev_ops = {
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.ndo_start_xmit = vcan_tx,
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.ndo_change_mtu = vcan_change_mtu,
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};
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static void vcan_setup(struct net_device *dev)
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{
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dev->type = ARPHRD_CAN;
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dev->mtu = CAN_MTU;
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dev->hard_header_len = 0;
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dev->addr_len = 0;
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dev->tx_queue_len = 0;
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dev->flags = IFF_NOARP;
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/* set flags according to driver capabilities */
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if (echo)
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dev->flags |= IFF_ECHO;
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dev->netdev_ops = &vcan_netdev_ops;
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dev->needs_free_netdev = true;
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}
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static struct rtnl_link_ops vcan_link_ops __read_mostly = {
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.kind = DRV_NAME,
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.setup = vcan_setup,
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};
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static __init int vcan_init_module(void)
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{
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pr_info("vcan: Virtual CAN interface driver\n");
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if (echo)
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printk(KERN_INFO "vcan: enabled echo on driver level.\n");
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return rtnl_link_register(&vcan_link_ops);
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}
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static __exit void vcan_cleanup_module(void)
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{
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rtnl_link_unregister(&vcan_link_ops);
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}
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module_init(vcan_init_module);
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module_exit(vcan_cleanup_module);
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