drivers/net/tun.c



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/*
 *  TUN - Universal TUN/TAP device driver.
 *  Copyright (C) 1999-2002 Maxim Krasnyansky <maxk@qualcomm.com>
 *
 *  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.
 *
 *  $Id: tun.c,v 1.15 2002/03/01 02:44:24 maxk Exp $
 */

/*
 *  Changes:
 *
 *  Mike Kershaw <dragorn@kismetwireless.net> 2005/08/14
 *    Add TUNSETLINK ioctl to set the link encapsulation
 *
 *  Mark Smith <markzzzsmith@yahoo.com.au>
 *   Use random_ether_addr() for tap MAC address.
 *
 *  Harald Roelle <harald.roelle@ifi.lmu.de>  2004/04/20
 *    Fixes in packet dropping, queue length setting and queue wakeup.
 *    Increased default tx queue length.
 *    Added ethtool API.
 *    Minor cleanups
 *
 *  Daniel Podlejski <underley@underley.eu.org>
 *    Modifications for 2.3.99-pre5 kernel.
 */

#define DRV_NAME	"tun"
#define DRV_VERSION	"1.6"
#define DRV_DESCRIPTION	"Universal TUN/TAP device driver"
#define DRV_COPYRIGHT	"(C) 1999-2004 Max Krasnyansky <maxk@qualcomm.com>"

#include <linux/config.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/fcntl.h>
#include <linux/init.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/miscdevice.h>
#include <linux/ethtool.h>
#include <linux/rtnetlink.h>
#include <linux/if.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/if_tun.h>
#include <linux/crc32.h>

#include <asm/system.h>
#include <asm/uaccess.h>

#ifdef TUN_DEBUG
static int debug;
#endif

/* Network device part of the driver */

static LIST_HEAD(tun_dev_list);
static struct ethtool_ops tun_ethtool_ops;

/* Net device open. */
static int tun_net_open(struct net_device *dev)
{
	netif_start_queue(dev);
	return 0;
}

/* Net device close. */
static int tun_net_close(struct net_device *dev)
{
	netif_stop_queue(dev);
	return 0;
}

/* Net device start xmit */
static int tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct tun_struct *tun = netdev_priv(dev);

	DBG(KERN_INFO "%s: tun_net_xmit %d\n", tun->dev->name, skb->len);

	/* Drop packet if interface is not attached */
	if (!tun->attached)
		goto drop;

	/* Packet dropping */
	if (skb_queue_len(&tun->readq) >= dev->tx_queue_len) {
		if (!(tun->flags & TUN_ONE_QUEUE)) {
			/* Normal queueing mode. */
			/* Packet scheduler handles dropping of further packets. */
			netif_stop_queue(dev);

			/* We won't see all dropped packets individually, so overrun
			 * error is more appropriate. */
			tun->stats.tx_fifo_errors++;
		} else {
			/* Single queue mode.
			 * Driver handles dropping of all packets itself. */
			goto drop;
		}
	}

	/* Queue packet */
	skb_queue_tail(&tun->readq, skb);
	dev->trans_start = jiffies;

	/* Notify and wake up reader process */
	if (tun->flags & TUN_FASYNC)
		kill_fasync(&tun->fasync, SIGIO, POLL_IN);
	wake_up_interruptible(&tun->read_wait);
	return 0;

drop:
	tun->stats.tx_dropped++;
	kfree_skb(skb);
	return 0;
}

/** Add the specified Ethernet address to this multicast filter. */
static void
add_multi(u32* filter, const u8* addr)
{
	int bit_nr = ether_crc(ETH_ALEN, addr) >> 26;
	filter[bit_nr >> 5] |= 1 << (bit_nr & 31);
}

/** Remove the specified Ethernet addres from this multicast filter. */
static void
del_multi(u32* filter, const u8* addr)
{
	int bit_nr = ether_crc(ETH_ALEN, addr) >> 26;
	filter[bit_nr >> 5] &= ~(1 << (bit_nr & 31));
}

/** Update the list of multicast groups to which the network device belongs.
 * This list is used to filter packets being sent from the character device to
 * the network device. */
static void
tun_net_mclist(struct net_device *dev)
{
	struct tun_struct *tun = netdev_priv(dev);
	const struct dev_mc_list *mclist;
	int i;
	DBG(KERN_DEBUG "%s: tun_net_mclist: mc_count %d\n",
			dev->name, dev->mc_count);
	memset(tun->chr_filter, 0, sizeof tun->chr_filter);
	for (i = 0, mclist = dev->mc_list; i < dev->mc_count && mclist != NULL;
			i++, mclist = mclist->next) {
		add_multi(tun->net_filter, mclist->dmi_addr);
		DBG(KERN_DEBUG "%s: tun_net_mclist: %x:%x:%x:%x:%x:%x\n",
				dev->name,
				mclist->dmi_addr[0], mclist->dmi_addr[1], mclist->dmi_addr[2],
				mclist->dmi_addr[3], mclist->dmi_addr[4], mclist->dmi_addr[5]);
	}
}

static struct net_device_stats *tun_net_stats(struct net_device *dev)
{
	struct tun_struct *tun = netdev_priv(dev);
	return &tun->stats;
}

/* Initialize net device. */
static void tun_net_init(struct net_device *dev)
{
	struct tun_struct *tun = netdev_priv(dev);
   
	switch (tun->flags & TUN_TYPE_MASK) {
	case TUN_TUN_DEV:
		/* Point-to-Point TUN Device */
		dev->hard_header_len = 0;
		dev->addr_len = 0;
		dev->mtu = 1500;

		/* Zero header length */
		dev->type = ARPHRD_NONE; 
		dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
		dev->tx_queue_len = TUN_READQ_SIZE;  /* We prefer our own queue length */
		break;

	case TUN_TAP_DEV:
		/* Ethernet TAP Device */
		dev->set_multicast_list = tun_net_mclist;

		ether_setup(dev);
		random_ether_addr(dev->dev_addr);
		dev->tx_queue_len = TUN_READQ_SIZE;  /* We prefer our own queue length */
		break;
	}
}

/* Character device part */

/* Poll */
static unsigned int tun_chr_poll(struct file *file, poll_table * wait)
{  
	struct tun_struct *tun = file->private_data;
	unsigned int mask = POLLOUT | POLLWRNORM;

	if (!tun)
		return -EBADFD;

	DBG(KERN_INFO "%s: tun_chr_poll\n", tun->dev->name);

	poll_wait(file, &tun->read_wait, wait);
 
	if (!skb_queue_empty(&tun->readq))
		mask |= POLLIN | POLLRDNORM;

	return mask;
}

/* Get packet from user space buffer */
static __inline__ ssize_t tun_get_user(struct tun_struct *tun, struct iovec *iv, size_t count)
{
	struct tun_pi pi = { 0, __constant_htons(ETH_P_IP) };
	struct sk_buff *skb;
	size_t len = count, align = 0;

	if (!(tun->flags & TUN_NO_PI)) {
		if ((len -= sizeof(pi)) > count)
			return -EINVAL;

		if(memcpy_fromiovec((void *)&pi, iv, sizeof(pi)))
			return -EFAULT;
	}

	if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV)
		align = NET_IP_ALIGN;
 
	if (!(skb = alloc_skb(len + align, GFP_KERNEL))) {
		tun->stats.rx_dropped++;
		return -ENOMEM;
	}

	if (align)
		skb_reserve(skb, align);
	if (memcpy_fromiovec(skb_put(skb, len), iv, len)) {
		tun->stats.rx_dropped++;
		kfree_skb(skb);
		return -EFAULT;
	}

	skb->dev = tun->dev;
	switch (tun->flags & TUN_TYPE_MASK) {
	case TUN_TUN_DEV:
		skb->mac.raw = skb->data;
		skb->protocol = pi.proto;
		break;
	case TUN_TAP_DEV:
		skb->protocol = eth_type_trans(skb, tun->dev);
		break;
	};

	if (tun->flags & TUN_NOCHECKSUM)
		skb->ip_summed = CHECKSUM_UNNECESSARY;
 
	netif_rx_ni(skb);
	tun->dev->last_rx = jiffies;
   
	tun->stats.rx_packets++;
	tun->stats.rx_bytes += len;

	return count;
} 

static inline size_t iov_total(const struct iovec *iv, unsigned long count)
{
	unsigned long i;
	size_t len;

	for (i = 0, len = 0; i < count; i++) 
		len += iv[i].iov_len;

	return len;
}

/* Writev */
static ssize_t tun_chr_writev(struct file * file, const struct iovec *iv, 
			      unsigned long count, loff_t *pos)
{
	struct tun_struct *tun = file->private_data;

	if (!tun)
		return -EBADFD;

	DBG(KERN_INFO "%s: tun_chr_write %ld\n", tun->dev->name, count);

	return tun_get_user(tun, (struct iovec *) iv, iov_total(iv, count));
}

/* Write */
static ssize_t tun_chr_write(struct file * file, const char __user * buf, 
			     size_t count, loff_t *pos)
{
	struct iovec iv = { (void __user *) buf, count };
	return tun_chr_writev(file, &iv, 1, pos);
}

/* Put packet to the user space buffer */
static __inline__ ssize_t tun_put_user(struct tun_struct *tun,
				       struct sk_buff *skb,
				       struct iovec *iv, int len)
{
	struct tun_pi pi = { 0, skb->protocol };
	ssize_t total = 0;

	if (!(tun->flags & TUN_NO_PI)) {
		if ((len -= sizeof(pi)) < 0)
			return -EINVAL;

		if (len < skb->len) {
			/* Packet will be striped */
			pi.flags |= TUN_PKT_STRIP;
		}
 
		if (memcpy_toiovec(iv, (void *) &pi, sizeof(pi)))
			return -EFAULT;
		total += sizeof(pi);
	}