OpenWrt – Rev 4

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/*
 * trelay.c: Trivial Ethernet Relay
 *
 * Copyright (C) 2012 Felix Fietkau <nbd@nbd.name>
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */
#include <linux/module.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/netdevice.h>
#include <linux/rtnetlink.h>
#include <linux/debugfs.h>

static LIST_HEAD(trelay_devs);
static struct dentry *debugfs_dir;

struct trelay {
        struct list_head list;
        struct net_device *dev1, *dev2;
        struct dentry *debugfs;
        char name[];
};

rx_handler_result_t trelay_handle_frame(struct sk_buff **pskb)
{
        struct net_device *dev;
        struct sk_buff *skb = *pskb;

        dev = rcu_dereference(skb->dev->rx_handler_data);
        if (!dev)
                return RX_HANDLER_PASS;

        if (skb->protocol == htons(ETH_P_PAE))
                return RX_HANDLER_PASS;

        skb_push(skb, ETH_HLEN);
        skb->dev = dev;
        skb_forward_csum(skb);
        dev_queue_xmit(skb);

        return RX_HANDLER_CONSUMED;
}

static int trelay_open(struct inode *inode, struct file *file)
{
        file->private_data = inode->i_private;
        return 0;
}

static int trelay_do_remove(struct trelay *tr)
{
        list_del(&tr->list);

        dev_put(tr->dev1);
        dev_put(tr->dev2);

        netdev_rx_handler_unregister(tr->dev1);
        netdev_rx_handler_unregister(tr->dev2);

        debugfs_remove_recursive(tr->debugfs);
        kfree(tr);

        return 0;
}

static struct trelay *trelay_find(struct net_device *dev)
{
        struct trelay *tr;

        list_for_each_entry(tr, &trelay_devs, list) {
                if (tr->dev1 == dev || tr->dev2 == dev)
                        return tr;
        }
        return NULL;
}

static int tr_device_event(struct notifier_block *unused, unsigned long event,
                           void *ptr)
{
        struct net_device *dev = ptr;
        struct trelay *tr;

        if (event != NETDEV_UNREGISTER)
                goto out;

        tr = trelay_find(dev);
        if (!tr)
                goto out;

        trelay_do_remove(tr);

out:
        return NOTIFY_DONE;
}

static ssize_t trelay_remove_write(struct file *file, const char __user *ubuf,
                                   size_t count, loff_t *ppos)
{
        struct trelay *tr = file->private_data;
        int ret;

        rtnl_lock();
        ret = trelay_do_remove(tr);
        rtnl_unlock();

        if (ret < 0)
                 return ret;

        return count;
}

static const struct file_operations fops_remove = {
        .owner = THIS_MODULE,
        .open = trelay_open,
        .write = trelay_remove_write,
        .llseek = default_llseek,
};


static int trelay_do_add(char *name, char *devn1, char *devn2)
{
        struct net_device *dev1, *dev2;
        struct trelay *tr, *tr1;
        int ret;

        tr = kzalloc(sizeof(*tr) + strlen(name) + 1, GFP_KERNEL);
        if (!tr)
                return -ENOMEM;

        rtnl_lock();
        rcu_read_lock();

        ret = -EEXIST;
        list_for_each_entry(tr1, &trelay_devs, list) {
                if (!strcmp(tr1->name, name))
                        goto out;
        }

        ret = -ENOENT;
        dev1 = dev_get_by_name_rcu(&init_net, devn1);
        dev2 = dev_get_by_name_rcu(&init_net, devn2);
        if (!dev1 || !dev2)
                goto out;

        ret = netdev_rx_handler_register(dev1, trelay_handle_frame, dev2);
        if (ret < 0)
                goto out;

        ret = netdev_rx_handler_register(dev2, trelay_handle_frame, dev1);
        if (ret < 0) {
                netdev_rx_handler_unregister(dev1);
                goto out;
        }

        dev_hold(dev1);
        dev_hold(dev2);

        strcpy(tr->name, name);
        tr->dev1 = dev1;
        tr->dev2 = dev2;
        list_add_tail(&tr->list, &trelay_devs);

        tr->debugfs = debugfs_create_dir(name, debugfs_dir);
        debugfs_create_file("remove", S_IWUSR, tr->debugfs, tr, &fops_remove);
        ret = 0;

out:
        rcu_read_unlock();
        rtnl_unlock();
        if (ret < 0)
                kfree(tr);

        return ret;
}

static ssize_t trelay_add_write(struct file *file, const char __user *ubuf,
                                size_t count, loff_t *ppos)
{
        char buf[256];
        char *dev1, *dev2, *tmp;
        ssize_t len, ret;

        len = min(count, sizeof(buf) - 1);
        if (copy_from_user(buf, ubuf, len))
                return -EFAULT;

        buf[len] = 0;

        if ((tmp = strchr(buf, '\n')))
                *tmp = 0;

        dev1 = strchr(buf, ',');
        if (!dev1)
                return -EINVAL;

        *(dev1++) = 0;

        dev2 = strchr(dev1, ',');
        if (!dev2)
                return -EINVAL;

        *(dev2++) = 0;
        if (strchr(dev2, ','))
                return -EINVAL;

        if (!strlen(buf) || !strlen(dev1) || !strlen(dev2))
                return -EINVAL;

        ret = trelay_do_add(buf, dev1, dev2);
        if (ret < 0)
                return ret;

        return count;
}

static const struct file_operations fops_add = {
        .owner = THIS_MODULE,
        .write = trelay_add_write,
        .llseek = default_llseek,
};

static struct notifier_block tr_dev_notifier = {
        .notifier_call = tr_device_event
};

static int __init trelay_init(void)
{
        int ret;

        debugfs_dir = debugfs_create_dir("trelay", NULL);
        if (!debugfs_dir)
                return -ENOMEM;

        debugfs_create_file("add", S_IWUSR, debugfs_dir, NULL, &fops_add);

        ret = register_netdevice_notifier(&tr_dev_notifier);
        if (ret < 0)
                goto error;

        return 0;

error:
        debugfs_remove_recursive(debugfs_dir);
        return ret;
}

static void __exit trelay_exit(void)
{
        struct trelay *tr, *tmp;

        unregister_netdevice_notifier(&tr_dev_notifier);

        rtnl_lock();
        list_for_each_entry_safe(tr, tmp, &trelay_devs, list)
                trelay_do_remove(tr);
        rtnl_unlock();

        debugfs_remove_recursive(debugfs_dir);
}

module_init(trelay_init);
module_exit(trelay_exit);
MODULE_LICENSE("GPL");