drivers/net/dummy.c

   1 /* dummy.c: a dummy net driver
   2
   3         The purpose of this driver is to provide a device to point a
   4         route through, but not to actually transmit packets.
   5
   6         Why?  If you have a machine whose only connection is an occasional
   7         PPP/SLIP/PLIP link, you can only connect to your own hostname
   8         when the link is up.  Otherwise you have to use localhost.
   9         This isn't very consistent.
  10
  11         One solution is to set up a dummy link using PPP/SLIP/PLIP,
  12         but this seems (to me) too much overhead for too little gain.
  13         This driver provides a small alternative. Thus you can do
  14
  15         [when not running slip]
  16                 ifconfig dummy slip.addr.ess.here up
  17         [to go to slip]
  18                 ifconfig dummy down
  19                 dip whatever
  20
  21         This was written by looking at Donald Becker's skeleton driver
  22         and the loopback driver.  I then threw away anything that didn't
  23         apply!  Thanks to Alan Cox for the key clue on what to do with
  24         misguided packets.
  25
  26                         Nick Holloway, 27th May 1994
  27         [I tweaked this explanation a little but that's all]
  28                         Alan Cox, 30th May 1994
  29 */
  30
  31 /* To have statistics (just packets sent) define this */
  32
  33 #include <linux/config.h>
  34 #include <linux/kernel.h>
  35 #include <linux/module.h>
  36 #include <linux/sched.h>
  37 #include <linux/types.h>
  38 #include <linux/fcntl.h>
  39 #include <linux/interrupt.h>
  40 #include <linux/ptrace.h>
  41 #include <linux/ioport.h>
  42 #include <linux/in.h>
  43 #include <linux/malloc.h>
  44 #include <linux/string.h>
  45 #include <linux/init.h>
  46 #include <asm/system.h>
  47 #include <asm/bitops.h>
  48 #include <asm/io.h>
  49 #include <asm/dma.h>
  50 #include <linux/errno.h>
  51
  52 #include <linux/netdevice.h>
  53 #include <linux/etherdevice.h>
  54 #include <linux/skbuff.h>
  55
  56 static int dummy_xmit(struct sk_buff *skb, struct device *dev);
  57 static struct net_device_stats *dummy_get_stats(struct device *dev);
  58
  59 static int dummy_open(struct device *dev)
  60 {
  61         MOD_INC_USE_COUNT;
  62         return 0;
  63 }
  64
  65 static int dummy_close(struct device *dev)
  66 {
  67         MOD_DEC_USE_COUNT;
  68         return 0;
  69 }
  70
  71 /* fake multicast ability */
  72 static void set_multicast_list(struct device *dev)
  73 {
  74 }
  75
  76 #ifdef CONFIG_NET_FASTROUTE
  77 static int dummy_accept_fastpath(struct device *dev, struct dst_entry *dst)
  78 {
  79         return -1;
  80 }
  81 #endif
  82
  83 int __init dummy_init(struct device *dev)
  84 {
  85         /* Initialize the device structure. */
  86         dev->hard_start_xmit    = dummy_xmit;
  87
  88         dev->priv = kmalloc(sizeof(struct net_device_stats), GFP_KERNEL);
  89         if (dev->priv == NULL)
  90                 return -ENOMEM;
  91         memset(dev->priv, 0, sizeof(struct net_device_stats));
  92         dev->get_stats  = dummy_get_stats;
  93
  94         dev->open = dummy_open;
  95         dev->stop = dummy_close;
  96         dev->set_multicast_list = set_multicast_list;
  97
  98         /* Fill in the fields of the device structure with ethernet-generic values. */
  99         ether_setup(dev);
 100         dev->tx_queue_len = 0;
 101         dev->flags |= IFF_NOARP;
 102         dev->flags &= ~IFF_MULTICAST;
 103 #ifdef CONFIG_NET_FASTROUTE
 104         dev->accept_fastpath = dummy_accept_fastpath;
 105 #endif
 106
 107         return 0;
 108 }
 109
 110 static int dummy_xmit(struct sk_buff *skb, struct device *dev)
 111 {
 112         struct net_device_stats *stats;
 113         dev_kfree_skb(skb);
 114
 115         stats = (struct net_device_stats *)dev->priv;
 116         stats->tx_packets++;
 117         stats->tx_bytes+=skb->len;
 118
 119         return 0;
 120 }
 121
 122 static struct net_device_stats *dummy_get_stats(struct device *dev)
 123 {
 124         struct net_device_stats *stats = (struct net_device_stats *) dev->priv;
 125         return stats;
 126 }
 127
 128 #ifdef MODULE
 129
 130 static int __init dummy_probe(struct device *dev)
 131 {
 132         dummy_init(dev);
 133         return 0;
 134 }
 135
 136 static char dummy_name[16];
 137
 138 static struct device dev_dummy = {
 139                 dummy_name,     /* Needs to be writeable */
 140                 0, 0, 0, 0,
 141                 0x0, 0,
 142                 0, 0, 0, NULL, dummy_probe };
 143
 144 int init_module(void)
 145 {
 146         /* Find a name for this unit */
 147         int err=dev_alloc_name(&dev_dummy,"dummy%d");
 148         if(err<0)
 149                 return err;
 150         if (register_netdev(&dev_dummy) != 0)
 151                 return -EIO;
 152         return 0;
 153 }
 154
 155 void cleanup_module(void)
 156 {
 157         unregister_netdev(&dev_dummy);
 158         kfree(dev_dummy.priv);
 159         dev_dummy.priv = NULL;
 160 }
 161 #endif /* MODULE */