net/ipv4/rarp.c

/* */
This source file includes following definitions.
rarp_release_entry
rarp_destroy
rarp_destroy_dev
rarp_device_event
rarp_init_pkt
rarp_rcv
rarp_req_set
rarp_req_get
rarp_ioctl
rarp_get_info
rarp_init
init_module
cleanup_module
   1 /* linux/net/inet/rarp.c
   2  *
   3  * Copyright (C) 1994 by Ross Martin
   4  * Based on linux/net/inet/arp.c, Copyright (C) 1994 by Florian La Roche
   5  *
   6  * This module implements the Reverse Address Resolution Protocol 
   7  * (RARP, RFC 903), which is used to convert low level addresses such
   8  * as ethernet addresses into high level addresses such as IP addresses.
   9  * The most common use of RARP is as a means for a diskless workstation 
  10  * to discover its IP address during a network boot.
  11  *
  12  **
  13  ***    WARNING:::::::::::::::::::::::::::::::::WARNING
  14  ****
  15  *****  SUN machines seem determined to boot solely from the person who
  16  ****   answered their RARP query. NEVER add a SUN to your RARP table
  17  ***    unless you have all the rest to boot the box from it. 
  18  **
  19  * 
  20  * Currently, only ethernet address -> IP address is likely to work.
  21  * (Is RARP ever used for anything else?)
  22  *
  23  * This code is free software; you can redistribute it and/or
  24  * modify it under the terms of the GNU General Public License
  25  * as published by the Free Software Foundation; either version
  26  * 2 of the License, or (at your option) any later version.
  27  *
  28  * Fixes
  29  *      Alan Cox        :       Rarp delete on device down needed as
  30  *                              reported by Walter Wolfgang.
  31  *
  32  */
  33 
  34 #include <linux/module.h>
  35 
  36 #include <linux/types.h>
  37 #include <linux/string.h>
  38 #include <linux/kernel.h>
  39 #include <linux/sched.h>
  40 #include <linux/mm.h>
  41 #include <linux/socket.h>
  42 #include <linux/sockios.h>
  43 #include <linux/errno.h>
  44 #include <linux/if_arp.h>
  45 #include <linux/in.h>
  46 #include <linux/config.h>
  47 
  48 #include <asm/system.h>
  49 #include <asm/segment.h>
  50 #include <stdarg.h>
  51 #include <linux/inet.h>
  52 #include <linux/netdevice.h>
  53 #include <linux/etherdevice.h>
  54 #include <net/ip.h>
  55 #include <net/route.h>
  56 #include <net/protocol.h>
  57 #include <net/tcp.h>
  58 #include <linux/skbuff.h>
  59 #include <net/sock.h>
  60 #include <net/arp.h>
  61 #include <net/rarp.h>
  62 #ifdef CONFIG_AX25
  63 #include <net/ax25.h>
  64 #endif
  65 #include <linux/proc_fs.h>
  66 #include <linux/stat.h>
  67 
  68 extern int (*rarp_ioctl_hook)(unsigned int,void*);
  69 
  70 /*
  71  *      This structure defines the RARP mapping cache. As long as we make 
  72  *      changes in this structure, we keep interrupts off.
  73  */
  74 
  75 struct rarp_table
  76 {
  77         struct rarp_table  *next;             /* Linked entry list           */
  78         unsigned long      ip;                /* ip address of entry         */
  79         unsigned char      ha[MAX_ADDR_LEN];  /* Hardware address            */
  80         unsigned char      hlen;              /* Length of hardware address  */
  81         unsigned char      htype;             /* Type of hardware in use     */
  82         struct device      *dev;              /* Device the entry is tied to */
  83 };
  84 
  85 struct rarp_table *rarp_tables = NULL;
  86 
  87 static int rarp_rcv(struct sk_buff *, struct device *, struct packet_type *);
  88 
  89 static struct packet_type rarp_packet_type =
  90 {
  91         0,  /* Should be: __constant_htons(ETH_P_RARP) - but this _doesn't_ come out constant! */
  92         0,                /* copy */
  93         rarp_rcv,
  94         NULL,
  95         NULL
  96 };
  97 
  98 static initflag = 1;
  99 
 100 
 101 /*
 102  *      Release the memory for this entry.
 103  */
 104 
 105 static inline void rarp_release_entry(struct rarp_table *entry)
     /*  */
 106 {
 107         kfree_s(entry, sizeof(struct rarp_table));
 108         return;
 109 }
 110 
 111 /*
 112  *      Delete a RARP mapping entry in the cache.
 113  */
 114 
 115 static void rarp_destroy(unsigned long ip_addr)
     /*  */
 116 {
 117         struct rarp_table *entry;
 118         struct rarp_table **pentry;
 119   
 120         cli();
 121         pentry = &rarp_tables;
 122         while ((entry = *pentry) != NULL)
 123         {
 124                 if (entry->ip == ip_addr)
 125                 {
 126                         *pentry = entry->next;
 127                         sti();
 128                         rarp_release_entry(entry);
 129                         return;
 130                 }
 131                 pentry = &entry->next;
 132         }
 133         sti();
 134 }
 135 
 136 /*
 137  *      Flush a device.
 138  */
 139 
 140 static void rarp_destroy_dev(struct device *dev)
     /*  */
 141 {
 142         struct rarp_table *entry;
 143         struct rarp_table **pentry;
 144   
 145         cli();
 146         pentry = &rarp_tables;
 147         while ((entry = *pentry) != NULL)
 148         {
 149                 if (entry->dev == dev)
 150                 {
 151                         *pentry = entry->next;
 152                         sti();
 153                         rarp_release_entry(entry);
 154                 }
 155                 else
 156                         pentry = &entry->next;
 157         }
 158         sti();
 159 }
 160 
 161 static int rarp_device_event(struct notifier_block *this, unsigned long event, void *ptr)
     /*  */
 162 {
 163         if(event!=NETDEV_DOWN)
 164                 return NOTIFY_DONE;
 165         rarp_destroy_dev((struct device *)ptr);
 166         return NOTIFY_DONE;
 167 }
 168 
 169 /*
 170  *      Called once when data first added to rarp cache with ioctl.
 171  */
 172  
 173 static struct notifier_block rarp_dev_notifier={
 174         rarp_device_event,
 175         NULL,
 176         0
 177 };
 178  
 179 static void rarp_init_pkt (void)
     /*  */
 180 {
 181         /* Register the packet type */
 182         rarp_packet_type.type=htons(ETH_P_RARP);
 183         dev_add_pack(&rarp_packet_type);
 184         register_netdevice_notifier(&rarp_dev_notifier);
 185 }
 186 
 187 /*
 188  *      Receive an arp request by the device layer.  Maybe it should be 
 189  *      rewritten to use the incoming packet for the reply. The current 
 190  *      "overhead" time isn't that high...
 191  */
 192 
 193 static int rarp_rcv(struct sk_buff *skb, struct device *dev, struct packet_type *pt)
     /*  */
 194 {
 195 /*
 196  *      We shouldn't use this type conversion. Check later.
 197  */
 198         struct arphdr *rarp = (struct arphdr *) skb->data;
 199         unsigned char *rarp_ptr = skb_pull(skb,sizeof(struct arphdr));
 200         struct rarp_table *entry;
 201         long sip,tip;
 202         unsigned char *sha,*tha;            /* s for "source", t for "target" */
 203         
 204 /*
 205  *      If this test doesn't pass, it's not IP, or we should ignore it anyway
 206  */
 207 
 208         if (rarp->ar_hln != dev->addr_len || dev->type != ntohs(rarp->ar_hrd) 
 209                 || dev->flags&IFF_NOARP)
 210         {
 211                 kfree_skb(skb, FREE_READ);
 212                 return 0;
 213         }
 214 
 215 /*
 216  *      If it's not a RARP request, delete it.
 217  */
 218         if (rarp->ar_op != htons(ARPOP_RREQUEST))
 219         {
 220                 kfree_skb(skb, FREE_READ);
 221                 return 0;
 222         }
 223 
 224 /*
 225  *      For now we will only deal with IP addresses.
 226  */
 227 
 228         if (
 229 #ifdef CONFIG_AX25
 230                 (rarp->ar_pro != htons(AX25_P_IP) && dev->type == ARPHRD_AX25) ||
 231 #endif
 232                 (rarp->ar_pro != htons(ETH_P_IP) && dev->type != ARPHRD_AX25)
 233                 || rarp->ar_pln != 4)
 234         {
 235                 /*
 236                  *      This packet is not for us. Remove it. 
 237                  */
 238                 kfree_skb(skb, FREE_READ);
 239                 return 0;
 240         }
 241   
 242 /*
 243  *      Extract variable width fields
 244  */
 245 
 246         sha=rarp_ptr;
 247         rarp_ptr+=dev->addr_len;
 248         memcpy(&sip,rarp_ptr,4);
 249         rarp_ptr+=4;
 250         tha=rarp_ptr;
 251         rarp_ptr+=dev->addr_len;
 252         memcpy(&tip,rarp_ptr,4);
 253 
 254 /*
 255  *      Process entry. Use tha for table lookup according to RFC903.
 256  */
 257   
 258         cli();
 259         for (entry = rarp_tables; entry != NULL; entry = entry->next)
 260                 if (!memcmp(entry->ha, tha, rarp->ar_hln))
 261                         break;
 262   
 263         if (entry != NULL)
 264         {
 265                 sip=entry->ip;
 266                 sti();
 267 
 268                 arp_send(ARPOP_RREPLY, ETH_P_RARP, sip, dev, dev->pa_addr, sha, 
 269                         dev->dev_addr);
 270         }
 271         else
 272                 sti();
 273 
 274         kfree_skb(skb, FREE_READ);
 275         return 0;
 276 }
 277 
 278 
 279 /*
 280  *      Set (create) a RARP cache entry.
 281  */
 282 
 283 static int rarp_req_set(struct arpreq *req)
     /*  */
 284 {
 285         struct arpreq r;
 286         struct rarp_table *entry;
 287         struct sockaddr_in *si;
 288         int htype, hlen;
 289         unsigned long ip;
 290         struct rtable *rt;
 291   
 292         memcpy_fromfs(&r, req, sizeof(r));
 293   
 294         /*
 295          *      We only understand about IP addresses... 
 296          */
 297 
 298         if (r.arp_pa.sa_family != AF_INET)
 299                 return -EPFNOSUPPORT;
 300   
 301         switch (r.arp_ha.sa_family) 
 302         {
 303                 case ARPHRD_ETHER:
 304                         htype = ARPHRD_ETHER;
 305                         hlen = ETH_ALEN;
 306                         break;
 307 #ifdef CONFIG_AX25
 308                 case ARPHRD_AX25:
 309                         htype = ARPHRD_AX25;
 310                         hlen = 7;
 311                 break;
 312 #endif
 313                 default:
 314                         return -EPFNOSUPPORT;
 315         }
 316 
 317         si = (struct sockaddr_in *) &r.arp_pa;
 318         ip = si->sin_addr.s_addr;
 319         if (ip == 0)
 320         {
 321                 printk("RARP: SETRARP: requested PA is 0.0.0.0 !\n");
 322                 return -EINVAL;
 323         }
 324   
 325 /*
 326  *      Is it reachable directly ?
 327  */
 328   
 329         rt = ip_rt_route(ip, NULL, NULL);
 330         if (rt == NULL)
 331                 return -ENETUNREACH;
 332 
 333 /*
 334  *      Is there an existing entry for this address?  Find out...
 335  */
 336   
 337         cli();
 338         for (entry = rarp_tables; entry != NULL; entry = entry->next)
 339                 if (entry->ip == ip)
 340                         break;
 341   
 342 /*
 343  *      If no entry was found, create a new one.
 344  */
 345 
 346         if (entry == NULL)
 347         {
 348                 entry = (struct rarp_table *) kmalloc(sizeof(struct rarp_table),
 349                                     GFP_ATOMIC);
 350                 if (entry == NULL)
 351                 {
 352                         sti();
 353                         return -ENOMEM;
 354                 }
 355                 if (initflag)
 356                 {
 357                         rarp_init_pkt();
 358                         initflag=0;
 359                 }
 360 
 361                 entry->next = rarp_tables;
 362                 rarp_tables = entry;
 363         }
 364 
 365         entry->ip = ip;
 366         entry->hlen = hlen;
 367         entry->htype = htype;
 368         memcpy(&entry->ha, &r.arp_ha.sa_data, hlen);
 369         entry->dev = rt->rt_dev;
 370 
 371         sti();  
 372 
 373         return 0;
 374 }
 375 
 376 
 377 /*
 378  *        Get a RARP cache entry.
 379  */
 380 
 381 static int rarp_req_get(struct arpreq *req)
     /*  */
 382 {
 383         struct arpreq r;
 384         struct rarp_table *entry;
 385         struct sockaddr_in *si;
 386         unsigned long ip;
 387 
 388 /*
 389  *      We only understand about IP addresses...
 390  */
 391         
 392         memcpy_fromfs(&r, req, sizeof(r));
 393   
 394         if (r.arp_pa.sa_family != AF_INET)
 395                 return -EPFNOSUPPORT;
 396   
 397 /*
 398  *        Is there an existing entry for this address?
 399  */
 400 
 401         si = (struct sockaddr_in *) &r.arp_pa;
 402         ip = si->sin_addr.s_addr;
 403 
 404         cli();
 405         for (entry = rarp_tables; entry != NULL; entry = entry->next)
 406                 if (entry->ip == ip)
 407                         break;
 408 
 409         if (entry == NULL)
 410         {
 411                 sti();
 412                 return -ENXIO;
 413         }
 414 
 415 /*
 416  *        We found it; copy into structure.
 417  */
 418         
 419         memcpy(r.arp_ha.sa_data, &entry->ha, entry->hlen);
 420         r.arp_ha.sa_family = entry->htype;
 421         sti();
 422   
 423 /*
 424  *        Copy the information back
 425  */
 426   
 427         memcpy_tofs(req, &r, sizeof(r));
 428         return 0;
 429 }
 430 
 431 
 432 /*
 433  *      Handle a RARP layer I/O control request.
 434  */
 435 
 436 int rarp_ioctl(unsigned int cmd, void *arg)
     /*  */
 437 {
 438         struct arpreq r;
 439         struct sockaddr_in *si;
 440         int err;
 441 
 442         switch(cmd)
 443         {
 444                 case SIOCDRARP:
 445                         if (!suser())
 446                                 return -EPERM;
 447                         err = verify_area(VERIFY_READ, arg, sizeof(struct arpreq));
 448                         if(err)
 449                                 return err;
 450                         memcpy_fromfs(&r, arg, sizeof(r));
 451                         if (r.arp_pa.sa_family != AF_INET)
 452                                 return -EPFNOSUPPORT;
 453                         si = (struct sockaddr_in *) &r.arp_pa;
 454                         rarp_destroy(si->sin_addr.s_addr);
 455                         return 0;
 456 
 457                 case SIOCGRARP:
 458                         err = verify_area(VERIFY_WRITE, arg, sizeof(struct arpreq));
 459                         if(err)
 460                                 return err;
 461                         return rarp_req_get((struct arpreq *)arg);
 462                 case SIOCSRARP:
 463                         if (!suser())
 464                                 return -EPERM;
 465                         err = verify_area(VERIFY_READ, arg, sizeof(struct arpreq));
 466                         if(err)
 467                                 return err;
 468                         return rarp_req_set((struct arpreq *)arg);
 469                 default:
 470                         return -EINVAL;
 471         }
 472 
 473         /*NOTREACHED*/
 474         return 0;
 475 }
 476 
 477 int rarp_get_info(char *buffer, char **start, off_t offset, int length, int dummy)
     /*  */
 478 {
 479         int len=0;
 480         off_t begin=0;
 481         off_t pos=0;
 482         int size;
 483         struct rarp_table *entry;
 484         char ipbuffer[20];
 485         unsigned long netip;
 486         if (initflag)
 487         {
 488                 size = sprintf(buffer,"RARP disabled until entries added to cache.\n");
 489                 pos+=size;
 490                 len+=size;
 491         }   
 492         else
 493         {
 494                 size = sprintf(buffer,
 495                         "IP address       HW type             HW address\n");
 496                 pos+=size;
 497                 len+=size;
 498       
 499                 cli();
 500                 for(entry=rarp_tables; entry!=NULL; entry=entry->next)
 501                 {
 502                         netip=htonl(entry->ip);          /* switch to network order */
 503                         sprintf(ipbuffer,"%d.%d.%d.%d",
 504                                 (unsigned int)(netip>>24)&255,
 505                                 (unsigned int)(netip>>16)&255,
 506                                 (unsigned int)(netip>>8)&255,
 507                                 (unsigned int)(netip)&255);
 508 
 509                         size = sprintf(buffer+len,
 510                                 "%-17s%-20s%02x:%02x:%02x:%02x:%02x:%02x\n",
 511                                 ipbuffer,
 512                                 "10Mbps Ethernet",
 513                                 (unsigned int)entry->ha[0],
 514                                 (unsigned int)entry->ha[1],
 515                                 (unsigned int)entry->ha[2],
 516                                 (unsigned int)entry->ha[3],
 517                                 (unsigned int)entry->ha[4],
 518                                 (unsigned int)entry->ha[5]);
 519           
 520                         len+=size;
 521                         pos=begin+len;
 522           
 523                         if(pos<offset)
 524                         {
 525                                 len=0;
 526                                 begin=pos;
 527                         }
 528                         if(pos>offset+length)
 529                                 break;
 530                 }
 531                 sti();
 532         }      
 533 
 534         *start = buffer+(offset-begin); /* Start of wanted data */
 535         len   -= (offset-begin);        /* Start slop */
 536         if (len>length)
 537                 len = length;           /* Ending slop */
 538         return len;
 539 }
 540 
 541 void
 542 rarp_init(void)
     /*  */
 543 {
 544         proc_net_register(&(struct proc_dir_entry) {
 545                 PROC_NET_RARP, 4, "rarp",
 546                 S_IFREG | S_IRUGO, 1, 0, 0,
 547                 0, &proc_net_inode_operations,
 548                 rarp_get_info
 549         });
 550         rarp_ioctl_hook = rarp_ioctl;
 551 }
 552 
 553 #ifdef MODULE
 554 
 555 int init_module(void)
     /*  */
 556 {
 557         rarp_init();
 558         return 0;
 559 }
 560 
 561 void cleanup_module(void)
     /*  */
 562 {
 563         struct rarp_table *rt, *rt_next;
 564         proc_net_unregister(PROC_NET_RARP);
 565         rarp_ioctl_hook = NULL;
 566         cli();
 567         /* Destroy the RARP-table */
 568         rt = rarp_tables;
 569         rarp_tables = NULL;
 570         sti();
 571         /* ... and free it. */
 572         for ( ; rt != NULL; rt = rt_next) {
 573                 rt_next = rt->next;
 574                 rarp_release_entry(rt);
 575         }
 576 }
 577 
 578 #endif
/* */
root/net/ipv4/rarp.c

DEFINITIONS
