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 net_device *dev);
  57 static struct net_device_stats *dummy_get_stats(struct net_device *dev);
  58
  59 static int dummy_open(struct net_device *dev)
  60 {
  61         MOD_INC_USE_COUNT;
  62         return 0;
  63 }
  64
  65 static int dummy_close(struct net_device *dev)
  66 {
  67         MOD_DEC_USE_COUNT;
  68         return 0;
  69 }
  70
  71 /* fake multicast ability */
  72 static void set_multicast_list(struct net_device *dev)
  73 {
  74 }
  75
  76 #ifdef CONFIG_NET_FASTROUTE
  77 static int dummy_accept_fastpath(struct net_device *dev, struct dst_entry *dst)
  78 {
  79         return -1;
  80 }
  81 #endif
  82
  83 int __init dummy_init(struct net_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 net_device *dev)
 111 {
 112         struct net_device_stats *stats;
 113
 114         stats = (struct net_device_stats *)dev->priv;
 115         stats->tx_packets++;
 116         stats->tx_bytes+=skb->len;
 117
 118         dev_kfree_skb(skb);
 119         return 0;
 120 }
 121
 122 static struct net_device_stats *dummy_get_stats(struct net_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 net_device *dev)
 131 {
 132         dummy_init(dev);
 133         return 0;
 134 }
 135
 136 static struct net_device dev_dummy = {
 137                 "",
 138                 0, 0, 0, 0,
 139                 0x0, 0,
 140                 0, 0, 0, NULL, dummy_probe };
 141
 142 int init_module(void)
 143 {
 144         /* Find a name for this unit */
 145         int err=dev_alloc_name(&dev_dummy,"dummy%d");
 146         if(err<0)
 147                 return err;
 148         if (register_netdev(&dev_dummy) != 0)
 149                 return -EIO;
 150         return 0;
 151 }
 152
 153 void cleanup_module(void)
 154 {
 155         unregister_netdev(&dev_dummy);
 156         kfree(dev_dummy.priv);
 157         dev_dummy.priv = NULL;
 158 }
 159 #endif /* MODULE */