drivers/net/tunnel.c

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 1 /* tunnel.c: an IP tunnel driver
 2
 3  The purpose of this driver is to provide an IP tunnel through
 4  which you can tunnel network traffic transparently across subnets.
 5
 6  This was written by looking at Nick Holloway's dummy driver
 7  Thanks for the great code!
 8
 9  -Sam Lantinga (slouken@cs.ucdavis.edu) 02/01/95
 10
 11  Minor tweaks:
 12  Cleaned up the code a little and added some pre-1.3.0 tweaks.
 13  dev->hard_header/hard_header_len changed to use no headers.
 14  Comments/bracketing tweaked.
 15  Made the tunnels use dev->name not tunnel: when error reporting.
 16  Added tx_dropped stat
 17
 18  -Alan Cox (Alan.Cox@linux.org) 21 March 95
 19
 20  Reworked:
 21  Changed to tunnel to destination gateway in addition to the
 22  tunnel's pointopoint address
 23  Almost completely rewritten
 24  Note: There is currently no firewall or ICMP handling done.
 25
 26  -Sam Lantinga (slouken@cs.ucdavis.edu) 02/13/96
 27
 28 */
 29
 30 /* Things I wish I had known when writing the tunnel driver:
 31
 32  When the tunnel_xmit() function is called, the skb contains the
 33  packet to be sent (plus a great deal of extra info), and dev
 34  contains the tunnel device that _we_ are.
 35
 36  When we are passed a packet, we are expected to fill in the
 37  source address with our source IP address.
 38
 39  What is the proper way to allocate, copy and free a buffer?
 40  After you allocate it, it is a "0 length" chunk of memory
 41  starting at zero. If you want to add headers to the buffer
 42  later, you'll have to call "skb_reserve(skb, amount)" with
 43  the amount of memory you want reserved. Then, you call
 44  "skb_put(skb, amount)" with the amount of space you want in
 45  the buffer. skb_put() returns a pointer to the top (#0) of
 46  that buffer. skb->len is set to the amount of space you have
 47  "allocated" with skb_put(). You can then write up to skb->len
 48  bytes to that buffer. If you need more, you can call skb_put()
 49  again with the additional amount of space you need. You can
 50  find out how much more space you can allocate by calling
 51  "skb_tailroom(skb)".
 52  Now, to add header space, call "skb_push(skb, header_len)".
 53  This creates space at the beginning of the buffer and returns
 54  a pointer to this new space. If later you need to strip a
 55  header from a buffer, call "skb_pull(skb, header_len)".
 56  skb_headroom() will return how much space is left at the top
 57  of the buffer (before the main data). Remember, this headroom
 58  space must be reserved before the skb_put() function is called.
 59 */
 60
 61 #include <linux/module.h>
 62 #include <linux/types.h>
 63 #include <linux/socket.h>
 64 #include <linux/in.h>
 65 #include <net/ip.h>
 66 #include <linux/if_arp.h>
 67
 68 /*#define TUNNEL_DEBUG*/
 69
 70 /*
 71  * Our header is a simple IP packet with no options
 72  */
 73
 74 #define tunnel_hlen sizeof(struct iphdr)
 75
 76 /*
 77  * Okay, this needs to be high enough that we can fit a "standard"
 78  * ethernet header and an IP tunnel header into the outgoing packet.
 79  * [36 bytes]
 80  */
 81
 82 #define TUNL_HLEN (((ETH_HLEN+15)&~15)+tunnel_hlen)
 83
 84
 85 static inttunnel_open(struct device *dev)
 86 {
 87  MOD_INC_USE_COUNT;
 88 return0;
 89 }
 90
 91 static inttunnel_close(struct device *dev)
 92 {
 93  MOD_DEC_USE_COUNT;
 94 return0;
 95 }
 96
 97 #ifdef TUNNEL_DEBUG
 98 voidprint_ip(struct iphdr *ip)
 99 {
 100 unsigned char*ipaddr;
 101
 102 printk("IP packet:\n");
 103 printk("--- header len = %d\n", ip->ihl*4);
 104 printk("--- ip version: %d\n", ip->version);
 105 printk("--- ip protocol: %d\n", ip->protocol);
 106  ipaddr=(unsigned char*)&ip->saddr;
 107 printk("--- source address: %u.%u.%u.%u\n",
 108 *ipaddr, *(ipaddr+1), *(ipaddr+2), *(ipaddr+3));
 109  ipaddr=(unsigned char*)&ip->daddr;
 110 printk("--- destination address: %u.%u.%u.%u\n",
 111 *ipaddr, *(ipaddr+1), *(ipaddr+2), *(ipaddr+3));
 112 printk("--- total packet len: %d\n",ntohs(ip->tot_len));
 113 }
 114 #endif
 115
 116 /*
 117  * This function assumes it is being called from dev_queue_xmit()
 118  * and that skb is filled properly by that function.
 119  */
 120
 121 static inttunnel_xmit(struct sk_buff *skb,struct device *dev)
 122 {
 123 struct enet_statistics *stats;/* This device's statistics */
 124 struct rtable *rt;/* Route to the other host */
 125 struct hh_cache *hh;
 126 struct device *tdev;/* Device to other host */
 127 struct iphdr *iph;/* Our new IP header */
 128 int max_headroom;/* The extra header space needed */
 129
 130  stats = (struct enet_statistics *)dev->priv;
 131
 132 /*
 133  * First things first. Look up the destination address in the
 134  * routing tables
 135  */
 136  iph = skb->nh.iph;
 137
 138 if(ip_route_output(&rt, dev->pa_dstaddr, dev->pa_addr,RT_TOS(iph->tos), NULL)) {
 139 /* No route to host */
 140 printk( KERN_INFO "%s: Can't reach target gateway!\n", dev->name);
 141  stats->tx_errors++;
 142 dev_kfree_skb(skb, FREE_WRITE);
 143 return0;
 144 }
 145  tdev = rt->u.dst.dev;
 146  hh = rt->u.dst.hh;
 147
 148 if(tdev->type == ARPHRD_TUNNEL) {
 149 /* Tunnel to tunnel? -- I don't think so. */
 150 printk( KERN_INFO "%s: Packet targetted at myself!\n", dev->name);
 151 ip_rt_put(rt);
 152  stats->tx_errors++;
 153 dev_kfree_skb(skb, FREE_WRITE);
 154 return0;
 155 }
 156
 157  skb->h.ipiph = skb->nh.iph;
 158
 159 /*
 160  * Okay, now see if we can stuff it in the buffer as-is.
 161  */
 162  max_headroom = (((tdev->hard_header_len+15)&~15)+tunnel_hlen);
 163
 164 if(skb_headroom(skb) < max_headroom || skb->users !=1) {
 165 struct sk_buff *new_skb =skb_realloc_headroom(skb, max_headroom);
 166 if(!new_skb) {
 167 ip_rt_put(rt);
 168  stats->tx_dropped++;
 169 dev_kfree_skb(skb, FREE_WRITE);
 170 return0;
 171 }
 172 dev_kfree_skb(skb, FREE_WRITE);
 173  skb = new_skb;
 174 }
 175
 176  skb->nh.iph = (struct iphdr *)skb_push(skb, tunnel_hlen);
 177 dst_release(skb->dst);
 178 memset(&(IPCB(skb)->opt),0,sizeof(IPCB(skb)->opt));
 179 dst_release(skb->dst);
 180  skb->dst = &rt->u.dst;
 181
 182 /*
 183  * Push down and install the IPIP header.
 184  */
 185
 186  iph = skb->nh.iph;
 187  iph->version =4;
 188  iph->tos = skb->h.ipiph->tos;
 189  iph->ttl = skb->h.ipiph->ttl;
 190  iph->frag_off =0;
 191  iph->daddr = dev->pa_dstaddr;
 192  iph->saddr = dev->pa_addr;
 193  iph->protocol = IPPROTO_IPIP;
 194  iph->ihl =5;
 195  iph->tot_len =htons(skb->len);
 196  iph->id =htons(ip_id_count++);/* Race condition here? */
 197 ip_send_check(iph);
 198
 199 ip_send(skb);
 200
 201 /* Record statistics and return */
 202  stats->tx_packets++;
 203 return0;
 204 }
 205
 206 static struct enet_statistics *tunnel_get_stats(struct device *dev)
 207 {
 208 return((struct enet_statistics*) dev->priv);
 209 }
 210
 211 /*
 212  * Called when a new tunnel device is initialized.
 213  * The new tunnel device structure is passed to us.
 214  */
 215
 216 inttunnel_init(struct device *dev)
 217 {
 218 int i;
 219
 220 /* Oh, just say we're here, in case anyone cares */
 221 static int tun_msg=0;
 222 if(!tun_msg)
 223 {
 224 printk( KERN_INFO "tunnel: version v0.2b2\n");
 225  tun_msg=1;
 226 }
 227
 228 /* Add our tunnel functions to the device */
 229  dev->open = tunnel_open;
 230  dev->stop = tunnel_close;
 231  dev->hard_start_xmit = tunnel_xmit;
 232  dev->get_stats = tunnel_get_stats;
 233  dev->priv =kmalloc(sizeof(struct enet_statistics), GFP_KERNEL);
 234 if(dev->priv == NULL)
 235 return-ENOMEM;
 236 memset(dev->priv,0,sizeof(struct enet_statistics));
 237
 238 /* Initialize the tunnel device structure */
 239 for(i =0; i < DEV_NUMBUFFS; i++)
 240 skb_queue_head_init(&dev->buffs[i]);
 241
 242  dev->hard_header = NULL;
 243  dev->rebuild_header = NULL;
 244  dev->set_mac_address = NULL;
 245  dev->hard_header_cache = NULL;
 246  dev->header_cache_update= NULL;
 247
 248  dev->type = ARPHRD_TUNNEL;
 249  dev->hard_header_len = TUNL_HLEN;
 250  dev->mtu =1500-tunnel_hlen;/* eth_mtu */
 251  dev->addr_len =0;/* Is this only for ARP? */
 252  dev->tx_queue_len =2;/* Small queue */
 253 memset(dev->broadcast,0xFF, ETH_ALEN);
 254
 255 /* New-style flags. */
 256  dev->flags = IFF_NOARP;/* Don't use ARP on this device */
 257 /* No broadcasting through a tunnel */
 258  dev->family = AF_INET;
 259  dev->pa_addr =0;
 260  dev->pa_brdaddr =0;
 261  dev->pa_mask =0;
 262  dev->pa_alen =4;
 263
 264 /* We're done. Have I forgotten anything? */
 265 return0;
 266 }
 267
 268 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 269 /* Module specific interface */
 270 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 271 #ifdef MODULE
 272
 273 static inttunnel_probe(struct device *dev)
 274 {
 275 tunnel_init(dev);
 276 return0;
 277 }
 278
 279 static struct device dev_tunnel =
 280 {
 281 "tunl0\0 ",
 282 0,0,0,0,
 283 0x0,0,
 284 0,0,0, NULL, tunnel_probe
 285 };
 286
 287 intinit_module(void)
 288 {
 289 /* Find a name for this unit */
 290 int ct=1;
 291
 292 while(dev_get(dev_tunnel.name)!=NULL && ct<100)
 293 {
 294 sprintf(dev_tunnel.name,"tunl%d",ct);
 295  ct++;
 296 }
 297
 298 #ifdef TUNNEL_DEBUG
 299 printk("tunnel: registering device %s\n", dev_tunnel.name);
 300 #endif
 301 if(register_netdev(&dev_tunnel) !=0)
 302 return-EIO;
 303 return0;
 304 }
 305
 306 voidcleanup_module(void)
 307 {
 308 unregister_netdev(&dev_tunnel);
 309 kfree_s(dev_tunnel.priv,sizeof(struct enet_statistics));
 310  dev_tunnel.priv=NULL;
 311 }
 312 #endif/* MODULE */
 313