drivers/net/ethertap.c

   1 /*
   2  *      Ethertap: A network device for bouncing packets via user space
   3  *
   4  *      This is a very simple ethernet driver. It bounces ethernet frames
   5  *      to user space on /dev/tap0->/dev/tap15 and expects ethernet frames
   6  *      to be written back to it. By default it does not ARP. If you turn ARP
   7  *      on it will attempt to ARP the user space and reply to ARPS from the
   8  *      user space.
   9  *
  10  *      As this is an ethernet device you can use it for appletalk, IPX etc
  11  *      even for building bridging tunnels.
  12  */
  13
  14 #include <linux/config.h>
  15 #include <linux/module.h>
  16
  17 #include <linux/kernel.h>
  18 #include <linux/jiffies.h>
  19 #include <linux/slab.h>
  20 #include <linux/string.h>
  21 #include <linux/errno.h>
  22
  23 #include <linux/netdevice.h>
  24 #include <linux/inetdevice.h>
  25 #include <linux/etherdevice.h>
  26 #include <linux/skbuff.h>
  27 #include <linux/init.h>
  28
  29 #include <net/sock.h>
  30 #include <linux/netlink.h>
  31
  32 /*
  33  *      Index to functions.
  34  */
  35
  36 int         ethertap_probe(struct net_device *dev);
  37 static int  ethertap_open(struct net_device *dev);
  38 static int  ethertap_start_xmit(struct sk_buff *skb, struct net_device *dev);
  39 static int  ethertap_close(struct net_device *dev);
  40 static struct net_device_stats *ethertap_get_stats(struct net_device *dev);
  41 static void ethertap_rx(struct sock *sk, int len);
  42 #ifdef CONFIG_ETHERTAP_MC
  43 static void set_multicast_list(struct net_device *dev);
  44 #endif
  45
  46 static int ethertap_debug;
  47
  48 static struct net_device *tap_map[32];  /* Returns the tap device for a given netlink */
  49
  50 /*
  51  *      Board-specific info in dev->priv.
  52  */
  53
  54 struct net_local
  55 {
  56         struct sock     *nl;
  57 #ifdef CONFIG_ETHERTAP_MC
  58         __u32           groups;
  59 #endif
  60         struct net_device_stats stats;
  61 };
  62
  63 /*
  64  *      To call this a probe is a bit misleading, however for real
  65  *      hardware it would have to check what was present.
  66  */
  67
  68 int __init ethertap_probe(struct net_device *dev)
  69 {
  70         SET_MODULE_OWNER(dev);
  71
  72         memcpy(dev->dev_addr, "\xFE\xFD\x00\x00\x00\x00", 6);
  73         if (dev->mem_start & 0xf)
  74                 ethertap_debug = dev->mem_start & 0x7;
  75
  76         /*
  77          *      Initialize the device structure.
  78          */
  79
  80         dev->priv = kmalloc(sizeof(struct net_local), GFP_KERNEL);
  81         if (dev->priv == NULL)
  82                 return -ENOMEM;
  83         memset(dev->priv, 0, sizeof(struct net_local));
  84
  85         /*
  86          *      The tap specific entries in the device structure.
  87          */
  88
  89         dev->open = ethertap_open;
  90         dev->hard_start_xmit = ethertap_start_xmit;
  91         dev->stop = ethertap_close;
  92         dev->get_stats = ethertap_get_stats;
  93 #ifdef CONFIG_ETHERTAP_MC
  94         dev->set_multicast_list = set_multicast_list;
  95 #endif
  96
  97         /*
  98          *      Setup the generic properties
  99          */
 100
 101         ether_setup(dev);
 102
 103         dev->tx_queue_len = 0;
 104         dev->flags|=IFF_NOARP;
 105         tap_map[dev->base_addr]=dev;
 106
 107         return 0;
 108 }
 109
 110 /*
 111  *      Open/initialize the board.
 112  */
 113
 114 static int ethertap_open(struct net_device *dev)
 115 {
 116         struct net_local *lp = (struct net_local*)dev->priv;
 117
 118         if (ethertap_debug > 2)
 119                 printk("%s: Doing ethertap_open()...", dev->name);
 120
 121         lp->nl = netlink_kernel_create(dev->base_addr, ethertap_rx);
 122         if (lp->nl == NULL)
 123                 return -ENOBUFS;
 124         netif_start_queue(dev);
 125         return 0;
 126 }
 127
 128 #ifdef CONFIG_ETHERTAP_MC
 129 static unsigned ethertap_mc_hash(__u8 *dest)
 130 {
 131         unsigned idx = 0;
 132         idx ^= dest[0];
 133         idx ^= dest[1];
 134         idx ^= dest[2];
 135         idx ^= dest[3];
 136         idx ^= dest[4];
 137         idx ^= dest[5];
 138         return 1U << (idx&0x1F);
 139 }
 140
 141 static void set_multicast_list(struct net_device *dev)
 142 {
 143         unsigned groups = ~0;
 144         struct net_local *lp = (struct net_local *)dev->priv;
 145
 146         if (!(dev->flags&(IFF_NOARP|IFF_PROMISC|IFF_ALLMULTI))) {
 147                 struct dev_mc_list *dmi;
 148
 149                 groups = ethertap_mc_hash(dev->broadcast);
 150
 151                 for (dmi=dev->mc_list; dmi; dmi=dmi->next) {
 152                         if (dmi->dmi_addrlen != 6)
 153                                 continue;
 154                         groups |= ethertap_mc_hash(dmi->dmi_addr);
 155                 }
 156         }
 157         lp->groups = groups;
 158         if (lp->nl)
 159                 lp->nl->protinfo.af_netlink.groups = groups;
 160 }
 161 #endif
 162
 163 /*
 164  *      We transmit by throwing the packet at netlink. We have to clone
 165  *      it for 2.0 so that we dev_kfree_skb() the locked original.
 166  */
 167
 168 static int ethertap_start_xmit(struct sk_buff *skb, struct net_device *dev)
 169 {
 170         struct net_local *lp = (struct net_local *)dev->priv;
 171 #ifdef CONFIG_ETHERTAP_MC
 172         struct ethhdr *eth = (struct ethhdr*)skb->data;
 173 #endif
 174
 175         if (skb_headroom(skb) < 2) {
 176                 static int once;
 177                 struct sk_buff *skb2;
 178
 179                 if (!once) {
 180                         once = 1;
 181                         printk(KERN_DEBUG "%s: not aligned xmit by protocol %04x\n", dev->name, skb->protocol);
 182                 }
 183
 184                 skb2 = skb_realloc_headroom(skb, 2);
 185                 dev_kfree_skb(skb);
 186                 if (skb2 == NULL)
 187                         return 0;
 188                 skb = skb2;
 189         }
 190         __skb_push(skb, 2);
 191
 192         /* Make the same thing, which loopback does. */
 193         if (skb_shared(skb)) {
 194                 struct sk_buff *skb2 = skb;
 195                 skb = skb_clone(skb, GFP_ATOMIC);       /* Clone the buffer */
 196                 if (skb==NULL) {
 197                         dev_kfree_skb(skb2);
 198                         return 0;
 199                 }
 200                 dev_kfree_skb(skb2);
 201         }
 202         /* ... but do not orphan it here, netlink does it in any case. */
 203
 204         lp->stats.tx_bytes+=skb->len;
 205         lp->stats.tx_packets++;
 206
 207 #ifndef CONFIG_ETHERTAP_MC
 208         netlink_broadcast(lp->nl, skb, 0, ~0, GFP_ATOMIC);
 209 #else
 210         if (dev->flags&IFF_NOARP) {
 211                 netlink_broadcast(lp->nl, skb, 0, ~0, GFP_ATOMIC);
 212                 return 0;
 213         }
 214
 215         if (!(eth->h_dest[0]&1)) {
 216                 /* Unicast packet */
 217                 __u32 pid;
 218                 memcpy(&pid, eth->h_dest+2, 4);
 219                 netlink_unicast(lp->nl, skb, ntohl(pid), MSG_DONTWAIT);
 220         } else
 221                 netlink_broadcast(lp->nl, skb, 0, ethertap_mc_hash(eth->h_dest), GFP_ATOMIC);
 222 #endif
 223         return 0;
 224 }
 225
 226 static __inline__ int ethertap_rx_skb(struct sk_buff *skb, struct net_device *dev)
 227 {
 228         struct net_local *lp = (struct net_local *)dev->priv;
 229 #ifdef CONFIG_ETHERTAP_MC
 230         struct ethhdr *eth = (struct ethhdr*)(skb->data + 2);
 231 #endif
 232         int len = skb->len;
 233
 234         if (len < 16) {
 235                 printk(KERN_DEBUG "%s : rx len = %d\n", dev->name, len);
 236                 kfree_skb(skb);
 237                 return -EINVAL;
 238         }
 239         if (NETLINK_CREDS(skb)->uid) {
 240                 printk(KERN_INFO "%s : user %d\n", dev->name, NETLINK_CREDS(skb)->uid);
 241                 kfree_skb(skb);
 242                 return -EPERM;
 243         }
 244
 245 #ifdef CONFIG_ETHERTAP_MC
 246         if (!(dev->flags&(IFF_NOARP|IFF_PROMISC))) {
 247                 int drop = 0;
 248
 249                 if (eth->h_dest[0]&1) {
 250                         if (!(ethertap_mc_hash(eth->h_dest)&lp->groups))
 251                                 drop = 1;
 252                 } else if (memcmp(eth->h_dest, dev->dev_addr, 6) != 0)
 253                         drop = 1;
 254
 255                 if (drop) {
 256                         if (ethertap_debug > 3)
 257                                 printk(KERN_DEBUG "%s : not for us\n", dev->name);
 258                         kfree_skb(skb);
 259                         return -EINVAL;
 260                 }
 261         }
 262 #endif
 263
 264         if (skb_shared(skb)) {
 265                 struct sk_buff *skb2 = skb;
 266                 skb = skb_clone(skb, GFP_KERNEL);       /* Clone the buffer */
 267                 if (skb==NULL) {
 268                         kfree_skb(skb2);
 269                         return -ENOBUFS;
 270                 }
 271                 kfree_skb(skb2);
 272         } else
 273                 skb_orphan(skb);
 274
 275         skb_pull(skb, 2);
 276         skb->dev = dev;
 277         skb->protocol=eth_type_trans(skb,dev);
 278         memset(skb->cb, 0, sizeof(skb->cb));
 279         lp->stats.rx_packets++;
 280         lp->stats.rx_bytes+=len;
 281         netif_rx(skb);
 282         dev->last_rx = jiffies;
 283         return len;
 284 }
 285
 286 /*
 287  *      The typical workload of the driver:
 288  *      Handle the ether interface interrupts.
 289  *
 290  *      (In this case handle the packets posted from user space..)
 291  */
 292
 293 static void ethertap_rx(struct sock *sk, int len)
 294 {
 295         struct net_device *dev = tap_map[sk->sk_protocol];
 296         struct sk_buff *skb;
 297
 298         if (dev==NULL) {
 299                 printk(KERN_CRIT "ethertap: bad unit!\n");
 300                 skb_queue_purge(&sk->sk_receive_queue);
 301                 return;
 302         }
 303
 304         if (ethertap_debug > 3)
 305                 printk("%s: ethertap_rx()\n", dev->name);
 306
 307         while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL)
 308                 ethertap_rx_skb(skb, dev);
 309 }
 310
 311 static int ethertap_close(struct net_device *dev)
 312 {
 313         struct net_local *lp = (struct net_local *)dev->priv;
 314         struct sock *sk = lp->nl;
 315
 316         if (ethertap_debug > 2)
 317                 printk("%s: Shutting down.\n", dev->name);
 318
 319         netif_stop_queue(dev);
 320
 321         if (sk) {
 322                 lp->nl = NULL;
 323                 sock_release(sk->sk_socket);
 324         }
 325
 326         return 0;
 327 }
 328
 329 static struct net_device_stats *ethertap_get_stats(struct net_device *dev)
 330 {
 331         struct net_local *lp = (struct net_local *)dev->priv;
 332         return &lp->stats;
 333 }
 334
 335 #ifdef MODULE
 336
 337 static int unit;
 338 MODULE_PARM(unit,"i");
 339 MODULE_PARM_DESC(unit,"Ethertap device number");
 340
 341 static struct net_device dev_ethertap =
 342 {
 343         .name           =       " ",
 344         .init           =        ethertap_probe
 345 };
 346
 347 int init_module(void)
 348 {
 349         dev_ethertap.base_addr=unit+NETLINK_TAPBASE;
 350         sprintf(dev_ethertap.name,"tap%d",unit);
 351         if (dev_get(dev_ethertap.name))
 352         {
 353                 printk(KERN_INFO "%s already loaded.\n", dev_ethertap.name);
 354                 return -EBUSY;
 355         }
 356         if (register_netdev(&dev_ethertap) != 0)
 357                 return -EIO;
 358         return 0;
 359 }
 360
 361 void cleanup_module(void)
 362 {
 363         tap_map[dev_ethertap.base_addr]=NULL;
 364         unregister_netdev(&dev_ethertap);
 365
 366         /*
 367          *      Free up the private structure.
 368          */
 369
 370         kfree(dev_ethertap.priv);
 371         dev_ethertap.priv = NULL;       /* gets re-allocated by ethertap_probe */
 372 }
 373
 374 #endif /* MODULE */
 375 MODULE_LICENSE("GPL");
 376