![[first]](../icons/first.png){kind=icon}
![[previous]](../icons/n_left.png){kind=icon}
![[next]](../icons/n_right.png){kind=icon}
![[last]](../icons/last.png){kind=icon}
![[top]](../icons/n_top.png){kind=icon}
![[bottom]](../icons/bottom.png){kind=icon}
![[index]](../icons/index.png){kind=icon}
![[help]](../icons/help.png){kind=icon}
*/
1 /* linux/net/inet/arp.c
2 *
3 * Copyright (C) 1994 by Florian La Roche
4 *
5 * This module implements the Address Resolution Protocol ARP (RFC 826),
6 * which is used to convert IP addresses (or in the future maybe other
7 * high-level addresses into a low-level hardware address (like an Ethernet
8 * address).
9 *
10 * FIXME:
11 * Experiment with better retransmit timers
12 * Clean up the timer deletions
13 * If you create a proxy entry set your interface address to the address
14 * and then delete it, proxies may get out of sync with reality - check this
15 *
16 * This program is free software; you can redistribute it and/or
17 * modify it under the terms of the GNU General Public License
18 * as published by the Free Software Foundation; either version
19 * 2 of the License, or (at your option) any later version.
20 *
21 *
22 * Fixes:
23 * Alan Cox : Removed the ethernet assumptions in Florian's code
24 * Alan Cox : Fixed some small errors in the ARP logic
25 * Alan Cox : Allow >4K in /proc
26 * Alan Cox : Make ARP add its own protocol entry
27 *
28 * Ross Martin : Rewrote arp_rcv() and arp_get_info()
29 * Stephen Henson : Add AX25 support to arp_get_info()
30 * Alan Cox : Drop data when a device is downed.
31 * Alan Cox : Use init_timer().
32 * Alan Cox : Double lock fixes.
33 * Martin Seine : Move the arphdr structure
34 * to if_arp.h for compatibility.
35 * with BSD based programs.
36 * Andrew Tridgell : Added ARP netmask code and
37 * re-arranged proxy handling.
38 * Alan Cox : Changed to use notifiers.
39 * Niibe Yutaka : Reply for this device or proxies only.
40 * Alan Cox : Don't proxy across hardware types!
41 * Jonathan Naylor : Added support for NET/ROM.
42 */
43
44 #include <linux/types.h>
45 #include <linux/string.h>
46 #include <linux/kernel.h>
47 #include <linux/sched.h>
48 #include <linux/config.h>
49 #include <linux/socket.h>
50 #include <linux/sockios.h>
51 #include <linux/errno.h>
52 #include <linux/if_arp.h>
53 #include <linux/in.h>
54 #include <linux/mm.h>
55 #include <asm/system.h>
56 #include <asm/segment.h>
57 #include <stdarg.h>
58 #include <linux/inet.h>
59 #include <linux/netdevice.h>
60 #include <linux/etherdevice.h>
61 #include <linux/trdevice.h>
62 #include <net/ip.h>
63 #include <net/route.h>
64 #include <net/protocol.h>
65 #include <net/tcp.h>
66 #include <linux/skbuff.h>
67 #include <net/sock.h>
68 #include <net/arp.h>
69 #ifdef CONFIG_AX25
70 #include <net/ax25.h>
71 #ifdef CONFIG_NETROM
72 #include <net/netrom.h>
73 #endif
74 #endif
75
76
77 /*
78 * This structure defines the ARP mapping cache. As long as we make changes
79 * in this structure, we keep interrupts of. But normally we can copy the
80 * hardware address and the device pointer in a local variable and then make
81 * any "long calls" to send a packet out.
82 */
83
84 struct arp_table
85 {
86 struct arp_table *next; /* Linked entry list */
87 unsigned long last_used; /* For expiry */
88 unsigned int flags; /* Control status */
89 unsigned long ip; /* ip address of entry */
90 unsigned long mask; /* netmask - used for generalised proxy arps (tridge) */
91 unsigned char ha[MAX_ADDR_LEN]; /* Hardware address */
92 unsigned char hlen; /* Length of hardware address */
93 unsigned short htype; /* Type of hardware in use */
94 struct device *dev; /* Device the entry is tied to */
95
96 /*
97 * The following entries are only used for unresolved hw addresses.
98 */
99
100 struct timer_list timer; /* expire timer */
101 int retries; /* remaining retries */
102 struct sk_buff_head skb; /* list of queued packets */
103 };
104
105
106 /*
107 * Configurable Parameters (don't touch unless you know what you are doing
108 */
109
110 /*
111 * If an arp request is send, ARP_RES_TIME is the timeout value until the
112 * next request is send.
113 */
114
115 #define ARP_RES_TIME (250*(HZ/10))
116
117 /*
118 * The number of times an arp request is send, until the host is
119 * considered unreachable.
120 */
121
122 #define ARP_MAX_TRIES 3
123
124 /*
125 * After that time, an unused entry is deleted from the arp table.
126 */
127
128 #define ARP_TIMEOUT (600*HZ)
129
130 /*
131 * How often is the function 'arp_check_retries' called.
132 * An entry is invalidated in the time between ARP_TIMEOUT and
133 * (ARP_TIMEOUT+ARP_CHECK_INTERVAL).
134 */
135
136 #define ARP_CHECK_INTERVAL (60 * HZ)
137
138 enum proxy {
139 PROXY_EXACT=0,
140 PROXY_ANY,
141 PROXY_NONE,
142 };
143
144 /* Forward declarations. */
145 static void arp_check_expire (unsigned long);
146 static struct arp_table *arp_lookup(unsigned long paddr, enum proxy proxy);
147
148
149 static struct timer_list arp_timer =
150 { NULL, NULL, ARP_CHECK_INTERVAL, 0L, &arp_check_expire };
151
152 /*
153 * The default arp netmask is just 255.255.255.255 which means it's
154 * a single machine entry. Only proxy entries can have other netmasks
155 *
156 */
157
158 #define DEF_ARP_NETMASK (~0)
159
160
161 /*
162 * The size of the hash table. Must be a power of two.
163 * Maybe we should remove hashing in the future for arp and concentrate
164 * on Patrick Schaaf's Host-Cache-Lookup...
165 */
166
167
168 #define ARP_TABLE_SIZE 16
169
170 /* The ugly +1 here is to cater for proxy entries. They are put in their
171 own list for efficiency of lookup. If you don't want to find a proxy
172 entry then don't look in the last entry, otherwise do
173 */
174
175 #define FULL_ARP_TABLE_SIZE (ARP_TABLE_SIZE+1)
176
177 struct arp_table *arp_tables[FULL_ARP_TABLE_SIZE] =
178 {
179 NULL,
180 };
181
182 unsigned long arp_cache_stamp;
183
184
185 /*
186 * The last bits in the IP address are used for the cache lookup.
187 * A special entry is used for proxy arp entries
188 */
189
190 #define HASH(paddr) (htonl(paddr) & (ARP_TABLE_SIZE - 1))
191 #define PROXY_HASH ARP_TABLE_SIZE
192
193 /*
194 * Check if there are too old entries and remove them. If the ATF_PERM
195 * flag is set, they are always left in the arp cache (permanent entry).
196 * Note: Only fully resolved entries, which don't have any packets in
197 * the queue, can be deleted, since ARP_TIMEOUT is much greater than
198 * ARP_MAX_TRIES*ARP_RES_TIME.
199 */
200
201 static void arp_check_expire(unsigned long dummy)
/* ![[next]](../icons/right.png)
![[first]](../icons/n_first.png)
![[top]](../icons/top.png)
*/
202 {
203 int i;
204 unsigned long now = jiffies;
205 unsigned long flags;
206 save_flags(flags);
207 cli();
208
209 for (i = 0; i < FULL_ARP_TABLE_SIZE; i++)
210 {
211 struct arp_table *entry;
212 struct arp_table **pentry = &arp_tables[i];
213
214 while ((entry = *pentry) != NULL)
215 {
216 if ((now - entry->last_used) > ARP_TIMEOUT
217 && !(entry->flags & ATF_PERM))
218 {
219 *pentry = entry->next; /* remove from list */
220 arp_cache_stamp++;
221 del_timer(&entry->timer); /* Paranoia */
222 kfree_s(entry, sizeof(struct arp_table));
223 }
224 else
225 pentry = &entry->next; /* go to next entry */
226 }
227 }
228 restore_flags(flags);
229
230 /*
231 * Set the timer again.
232 */
233
234 del_timer(&arp_timer);
235 arp_timer.expires = ARP_CHECK_INTERVAL;
236 add_timer(&arp_timer);
237 }
238
239
240 /*
241 * Release all linked skb's and the memory for this entry.
242 */
243
244 static void arp_release_entry(struct arp_table *entry)
/* ![[previous]](../icons/left.png)
*/
245 {
246 struct sk_buff *skb;
247 unsigned long flags;
248
249 save_flags(flags);
250 cli();
251 /* Release the list of `skb' pointers. */
252 while ((skb = skb_dequeue(&entry->skb)) != NULL)
253 {
254 skb_device_lock(skb);
255 restore_flags(flags);
256 dev_kfree_skb(skb, FREE_WRITE);
257 }
258 restore_flags(flags);
259 del_timer(&entry->timer);
260 kfree_s(entry, sizeof(struct arp_table));
261 return;
262 }
263
264 /*
265 * Purge a device from the ARP queue
266 */
267
268 int arp_device_event(unsigned long event, void *ptr)
/* */
269 {
270 struct device *dev=ptr;
271 int i;
272 unsigned long flags;
273
274 if(event!=NETDEV_DOWN)
275 return NOTIFY_DONE;
276 /*
277 * This is a bit OTT - maybe we need some arp semaphores instead.
278 */
279
280 save_flags(flags);
281 cli();
282 for (i = 0; i < FULL_ARP_TABLE_SIZE; i++)
283 {
284 struct arp_table *entry;
285 struct arp_table **pentry = &arp_tables[i];
286
287 while ((entry = *pentry) != NULL)
288 {
289 if(entry->dev==dev)
290 {
291 *pentry = entry->next; /* remove from list */
292 del_timer(&entry->timer); /* Paranoia */
293 kfree_s(entry, sizeof(struct arp_table));
294 }
295 else
296 pentry = &entry->next; /* go to next entry */
297 }
298 }
299 arp_cache_stamp++;
300 restore_flags(flags);
301 return NOTIFY_DONE;
302 }
303
304
305 /*
306 * Create and send an arp packet. If (dest_hw == NULL), we create a broadcast
307 * message.
308 */
309
310 void arp_send(int type, int ptype, unsigned long dest_ip,
/* */
311 struct device *dev, unsigned long src_ip,
312 unsigned char *dest_hw, unsigned char *src_hw)
313 {
314 struct sk_buff *skb;
315 struct arphdr *arp;
316 unsigned char *arp_ptr;
317
318 /*
319 * No arp on this interface.
320 */
321
322 if(dev->flags&IFF_NOARP)
323 return;
324
325 /*
326 * Allocate a buffer
327 */
328
329 skb = alloc_skb(sizeof(struct arphdr)+ 2*(dev->addr_len+4)
330 + dev->hard_header_len, GFP_ATOMIC);
331 if (skb == NULL)
332 {
333 printk("ARP: no memory to send an arp packet\n");
334 return;
335 }
336 skb->len = sizeof(struct arphdr) + dev->hard_header_len + 2*(dev->addr_len+4);
337 skb->arp = 1;
338 skb->dev = dev;
339 skb->free = 1;
340
341 /*
342 * Fill the device header for the ARP frame
343 */
344
345 dev->hard_header(skb->data,dev,ptype,dest_hw?dest_hw:dev->broadcast,src_hw?src_hw:NULL,skb->len,skb);
346
347 /* Fill out the arp protocol part. */
348 arp = (struct arphdr *) (skb->data + dev->hard_header_len);
349 arp->ar_hrd = htons(dev->type);
350 #ifdef CONFIG_AX25
351 #ifdef CONFIG_NETROM
352 arp->ar_pro = (dev->type == ARPHRD_AX25 || dev->type == ARPHRD_NETROM) ? htons(AX25_P_IP) : htons(ETH_P_IP);
353 #else
354 arp->ar_pro = (dev->type != ARPHRD_AX25)? htons(ETH_P_IP) : htons(AX25_P_IP);
355 #endif
356 #else
357 arp->ar_pro = htons(ETH_P_IP);
358 #endif
359 arp->ar_hln = dev->addr_len;
360 arp->ar_pln = 4;
361 arp->ar_op = htons(type);
362
363 arp_ptr=(unsigned char *)(arp+1);
364
365 memcpy(arp_ptr, src_hw, dev->addr_len);
366 arp_ptr+=dev->addr_len;
367 memcpy(arp_ptr, &src_ip,4);
368 arp_ptr+=4;
369 if (dest_hw != NULL)
370 memcpy(arp_ptr, dest_hw, dev->addr_len);
371 else
372 memset(arp_ptr, 0, dev->addr_len);
373 arp_ptr+=dev->addr_len;
374 memcpy(arp_ptr, &dest_ip, 4);
375
376 dev_queue_xmit(skb, dev, 0);
377 }
378
379
380 /*
381 * This function is called, if an entry is not resolved in ARP_RES_TIME.
382 * Either resend a request, or give it up and free the entry.
383 */
384
385 static void arp_expire_request (unsigned long arg)
/* */
386 {
387 struct arp_table *entry = (struct arp_table *) arg;
388 struct arp_table **pentry;
389 unsigned long hash;
390 unsigned long flags;
391
392 save_flags(flags);
393 cli();
394
395 /*
396 * Since all timeouts are handled with interrupts enabled, there is a
397 * small chance, that this entry has just been resolved by an incoming
398 * packet. This is the only race condition, but it is handled...
399 */
400
401 if (entry->flags & ATF_COM)
402 {
403 restore_flags(flags);
404 return;
405 }
406
407 if (--entry->retries > 0)
408 {
409 unsigned long ip = entry->ip;
410 struct device *dev = entry->dev;
411
412 /* Set new timer. */
413 del_timer(&entry->timer);
414 entry->timer.expires = ARP_RES_TIME;
415 add_timer(&entry->timer);
416 restore_flags(flags);
417 arp_send(ARPOP_REQUEST, ETH_P_ARP, ip, dev, dev->pa_addr,
418 NULL, dev->dev_addr);
419 return;
420 }
421
422 /*
423 * Arp request timed out. Delete entry and all waiting packets.
424 * If we give each entry a pointer to itself, we don't have to
425 * loop through everything again. Maybe hash is good enough, but
426 * I will look at it later.
427 */
428
429 hash = HASH(entry->ip);
430
431 /* proxy entries shouldn't really time out so this is really
432 only here for completeness
433 */
434 if (entry->flags & ATF_PUBL)
435 pentry = &arp_tables[PROXY_HASH];
436 else
437 pentry = &arp_tables[hash];
438 while (*pentry != NULL)
439 {
440 if (*pentry == entry)
441 {
442 *pentry = entry->next; /* delete from linked list */
443 del_timer(&entry->timer);
444 restore_flags(flags);
445 arp_release_entry(entry);
446 arp_cache_stamp++;
447 return;
448 }
449 pentry = &(*pentry)->next;
450 }
451 restore_flags(flags);
452 printk("Possible ARP queue corruption.\n");
453 /*
454 * We should never arrive here.
455 */
456 }
457
458
459 /*
460 * This will try to retransmit everything on the queue.
461 */
462
463 static void arp_send_q(struct arp_table *entry, unsigned char *hw_dest)
/* */
464 {
465 struct sk_buff *skb;
466
467 unsigned long flags;
468
469 /*
470 * Empty the entire queue, building its data up ready to send
471 */
472
473 if(!(entry->flags&ATF_COM))
474 {
475 printk("arp_send_q: incomplete entry for %s\n",
476 in_ntoa(entry->ip));
477 return;
478 }
479
480 save_flags(flags);
481
482 cli();
483 while((skb = skb_dequeue(&entry->skb)) != NULL)
484 {
485 IS_SKB(skb);
486 skb_device_lock(skb);
487 restore_flags(flags);
488 if(!skb->dev->rebuild_header(skb->data,skb->dev,skb->raddr,skb))
489 {
490 skb->arp = 1;
491 if(skb->sk==NULL)
492 dev_queue_xmit(skb, skb->dev, 0);
493 else
494 dev_queue_xmit(skb,skb->dev,skb->sk->priority);
495 }
496 else
497 {
498 /* This routine is only ever called when 'entry' is
499 complete. Thus this can't fail. */
500 printk("arp_send_q: The impossible occurred. Please notify Alan.\n");
501 printk("arp_send_q: active entity %s\n",in_ntoa(entry->ip));
502 printk("arp_send_q: failed to find %s\n",in_ntoa(skb->raddr));
503 }
504 }
505 restore_flags(flags);
506 }
507
508
509 /*
510 * Delete an ARP mapping entry in the cache.
511 */
512
513 void arp_destroy(unsigned long ip_addr, int force)
/* */
514 {
515 int checked_proxies = 0;
516 struct arp_table *entry;
517 struct arp_table **pentry;
518 unsigned long hash = HASH(ip_addr);
519
520 ugly:
521 cli();
522 pentry = &arp_tables[hash];
523 if (! *pentry) /* also check proxy entries */
524 pentry = &arp_tables[PROXY_HASH];
525
526 while ((entry = *pentry) != NULL)
527 {
528 if (entry->ip == ip_addr)
529 {
530 if ((entry->flags & ATF_PERM) && !force)
531 return;
532 *pentry = entry->next;
533 del_timer(&entry->timer);
534 sti();
535 arp_release_entry(entry);
536 /* this would have to be cleaned up */
537 goto ugly;
538 /* perhaps like this ?
539 cli();
540 entry = *pentry;
541 */
542 }
543 pentry = &entry->next;
544 if (!checked_proxies && ! *pentry)
545 { /* ugly. we have to make sure we check proxy
546 entries as well */
547 checked_proxies = 1;
548 pentry = &arp_tables[PROXY_HASH];
549 }
550 }
551 sti();
552 }
553
554
555 /*
556 * Receive an arp request by the device layer. Maybe I rewrite it, to
557 * use the incoming packet for the reply. The time for the current
558 * "overhead" isn't that high...
559 */
560
561 int arp_rcv(struct sk_buff *skb, struct device *dev, struct packet_type *pt)
/* */
562 {
563 /*
564 * We shouldn't use this type conversion. Check later.
565 */
566
567 struct arphdr *arp = (struct arphdr *)skb->h.raw;
568 unsigned char *arp_ptr= (unsigned char *)(arp+1);
569 struct arp_table *entry;
570 struct arp_table *proxy_entry;
571 int addr_hint,hlen,htype;
572 unsigned long hash;
573 unsigned char ha[MAX_ADDR_LEN]; /* So we can enable ints again. */
574 long sip,tip;
575 unsigned char *sha,*tha;
576
577 /*
578 * The hardware length of the packet should match the hardware length
579 * of the device. Similarly, the hardware types should match. The
580 * device should be ARP-able. Also, if pln is not 4, then the lookup
581 * is not from an IP number. We can't currently handle this, so toss
582 * it.
583 */
584 if (arp->ar_hln != dev->addr_len ||
585 dev->type != ntohs(arp->ar_hrd) ||
586 dev->flags & IFF_NOARP ||
587 arp->ar_pln != 4)
588 {
589 kfree_skb(skb, FREE_READ);
590 return 0;
591 }
592
593 /*
594 * Another test.
595 * The logic here is that the protocol being looked up by arp should
596 * match the protocol the device speaks. If it doesn't, there is a
597 * problem, so toss the packet.
598 */
599 switch(dev->type)
600 {
601 #ifdef CONFIG_AX25
602 case ARPHRD_AX25:
603 if(arp->ar_pro != htons(AX25_P_IP))
604 {
605 kfree_skb(skb, FREE_READ);
606 return 0;
607 }
608 break;
609 #endif
610 #ifdef CONFIG_NETROM
611 case ARPHRD_NETROM:
612 if(arp->ar_pro != htons(AX25_P_IP))
613 {
614 kfree_skb(skb, FREE_READ);
615 return 0;
616 }
617 break;
618 #endif
619 case ARPHRD_ETHER:
620 case ARPHRD_ARCNET:
621 if(arp->ar_pro != htons(ETH_P_IP))
622 {
623 kfree_skb(skb, FREE_READ);
624 return 0;
625 }
626 break;
627
628 case ARPHRD_IEEE802:
629 if(arp->ar_pro != htons(ETH_P_IP))
630 {
631 kfree_skb(skb, FREE_READ);
632 return 0;
633 }
634 break;
635
636 default:
637 printk("ARP: dev->type mangled!\n");
638 kfree_skb(skb, FREE_READ);
639 return 0;
640 }
641
642 /*
643 * Extract fields
644 */
645
646 hlen = dev->addr_len;
647 htype = dev->type;
648
649 sha=arp_ptr;
650 arp_ptr+=hlen;
651 memcpy(&sip,arp_ptr,4);
652 arp_ptr+=4;
653 tha=arp_ptr;
654 arp_ptr+=hlen;
655 memcpy(&tip,arp_ptr,4);
656
657 /*
658 * Check for bad requests for 127.0.0.1. If this is one such, delete it.
659 */
660 if(tip == INADDR_LOOPBACK)
661 {
662 kfree_skb(skb, FREE_READ);
663 return 0;
664 }
665
666 /*
667 * Process entry. The idea here is we want to send a reply if it is a
668 * request for us or if it is a request for someone else that we hold
669 * a proxy for. We want to add an entry to our cache if it is a reply
670 * to us or if it is a request for our address.
671 * (The assumption for this last is that if someone is requesting our
672 * address, they are probably intending to talk to us, so it saves time
673 * if we cache their address. Their address is also probably not in
674 * our cache, since ours is not in their cache.)
675 *
676 * Putting this another way, we only care about replies if they are to
677 * us, in which case we add them to the cache. For requests, we care
678 * about those for us and those for our proxies. We reply to both,
679 * and in the case of requests for us we add the requester to the arp
680 * cache.
681 */
682
683 addr_hint = ip_chk_addr(tip);
684
685 if(arp->ar_op == htons(ARPOP_REPLY))
686 {
687 if(addr_hint!=IS_MYADDR)
688 {
689 /*
690 * Replies to other machines get tossed.
691 */
692 kfree_skb(skb, FREE_READ);
693 return 0;
694 }
695 /*
696 * Fall through to code below that adds sender to cache.
697 */
698 }
699 else
700 {
701 /*
702 * It is now an arp request
703 */
704 /*
705 * Only reply for the real device address or when it's in our proxy tables
706 */
707 if(tip!=dev->pa_addr)
708 {
709 /*
710 * To get in here, it is a request for someone else. We need to
711 * check if that someone else is one of our proxies. If it isn't,
712 * we can toss it.
713 */
714 cli();
715 for(proxy_entry=arp_tables[PROXY_HASH];
716 proxy_entry;
717 proxy_entry = proxy_entry->next)
718 {
719 /* we will respond to a proxy arp request
720 if the masked arp table ip matches the masked
721 tip. This allows a single proxy arp table
722 entry to be used on a gateway machine to handle
723 all requests for a whole network, rather than
724 having to use a huge number of proxy arp entries
725 and having to keep them uptodate.
726 */
727 if (proxy_entry->dev != dev && proxy_entry->htype == htype &&
728 !((proxy_entry->ip^tip)&proxy_entry->mask))
729 break;
730
731 }
732 if (proxy_entry)
733 {
734 memcpy(ha, proxy_entry->ha, hlen);
735 sti();
736 arp_send(ARPOP_REPLY,ETH_P_ARP,sip,dev,tip,sha,ha);
737 kfree_skb(skb, FREE_READ);
738 return 0;
739 }
740 else
741 {
742 sti();
743 kfree_skb(skb, FREE_READ);
744 return 0;
745 }
746 }
747 else
748 {
749 /*
750 * To get here, it must be an arp request for us. We need to reply.
751 */
752 arp_send(ARPOP_REPLY,ETH_P_ARP,sip,dev,tip,sha,dev->dev_addr);
753 }
754 }
755
756
757 /*
758 * Now all replies are handled. Next, anything that falls through to here
759 * needs to be added to the arp cache, or have its entry updated if it is
760 * there.
761 */
762
763 hash = HASH(sip);
764 cli();
765 for(entry=arp_tables[hash];entry;entry=entry->next)
766 if(entry->ip==sip && entry->htype==htype)
767 break;
768
769 if(entry)
770 {
771 /*
772 * Entry found; update it.
773 */
774 memcpy(entry->ha, sha, hlen);
775 entry->hlen = hlen;
776 entry->last_used = jiffies;
777 if (!(entry->flags & ATF_COM))
778 {
779 /*
780 * This entry was incomplete. Delete the retransmit timer
781 * and switch to complete status.
782 */
783 del_timer(&entry->timer);
784 entry->flags |= ATF_COM;
785 sti();
786 /*
787 * Send out waiting packets. We might have problems, if someone is
788 * manually removing entries right now -- entry might become invalid
789 * underneath us.
790 */
791 arp_send_q(entry, sha);
792 }
793 else
794 {
795 sti();
796 }
797 }
798 else
799 {
800 /*
801 * No entry found. Need to add a new entry to the arp table.
802 */
803 entry = (struct arp_table *)kmalloc(sizeof(struct arp_table),GFP_ATOMIC);
804 if(entry == NULL)
805 {
806 sti();
807 printk("ARP: no memory for new arp entry\n");
808
809 kfree_skb(skb, FREE_READ);
810 return 0;
811 }
812
813 entry->mask = DEF_ARP_NETMASK;
814 entry->ip = sip;
815 entry->hlen = hlen;
816 entry->htype = htype;
817 entry->flags = ATF_COM;
818 init_timer(&entry->timer);
819 memcpy(entry->ha, sha, hlen);
820 entry->last_used = jiffies;
821 entry->dev = skb->dev;
822 skb_queue_head_init(&entry->skb);
823 entry->next = arp_tables[hash];
824 arp_tables[hash] = entry;
825 sti();
826 }
827
828 /*
829 * Replies have been sent, and entries have been added. All done.
830 */
831 kfree_skb(skb, FREE_READ);
832 return 0;
833 }
834
835
836 /*
837 * Find an arp mapping in the cache. If not found, post a request.
838 */
839
840 int arp_find(unsigned char *haddr, unsigned long paddr, struct device *dev,
/* */
841 unsigned long saddr, struct sk_buff *skb)
842 {
843 struct arp_table *entry;
844 unsigned long hash;
845 #ifdef CONFIG_IP_MULTICAST
846 unsigned long taddr;
847 #endif
848
849 switch (ip_chk_addr(paddr))
850 {
851 case IS_MYADDR:
852 printk("ARP: arp called for own IP address\n");
853 memcpy(haddr, dev->dev_addr, dev->addr_len);
854 skb->arp = 1;
855 return 0;
856 #ifdef CONFIG_IP_MULTICAST
857 case IS_MULTICAST:
858 if(dev->type==ARPHRD_ETHER || dev->type==ARPHRD_IEEE802)
859 {
860 haddr[0]=0x01;
861 haddr[1]=0x00;
862 haddr[2]=0x5e;
863 taddr=ntohl(paddr);
864 haddr[5]=taddr&0xff;
865 taddr=taddr>>8;
866 haddr[4]=taddr&0xff;
867 taddr=taddr>>8;
868 haddr[3]=taddr&0x7f;
869 return 0;
870 }
871 /*
872 * If a device does not support multicast broadcast the stuff (eg AX.25 for now)
873 */
874 #endif
875
876 case IS_BROADCAST:
877 memcpy(haddr, dev->broadcast, dev->addr_len);
878 skb->arp = 1;
879 return 0;
880 }
881
882 hash = HASH(paddr);
883 cli();
884
885 /*
886 * Find an entry
887 */
888 entry = arp_lookup(paddr, PROXY_NONE);
889
890 if (entry != NULL) /* It exists */
891 {
892 if (!(entry->flags & ATF_COM))
893 {
894 /*
895 * A request was already send, but no reply yet. Thus
896 * queue the packet with the previous attempt
897 */
898
899 if (skb != NULL)
900 {
901 skb_queue_tail(&entry->skb, skb);
902 skb_device_unlock(skb);
903 }
904 sti();
905 return 1;
906 }
907
908 /*
909 * Update the record
910 */
911
912 entry->last_used = jiffies;
913 memcpy(haddr, entry->ha, dev->addr_len);
914 if (skb)
915 skb->arp = 1;
916 sti();
917 return 0;
918 }
919
920 /*
921 * Create a new unresolved entry.
922 */
923
924 entry = (struct arp_table *) kmalloc(sizeof(struct arp_table),
925 GFP_ATOMIC);
926 if (entry != NULL)
927 {
928 entry->next = arp_tables[hash];
929 entry->last_used = jiffies;
930 entry->flags = 0;
931 entry->ip = paddr;
932 entry->mask = DEF_ARP_NETMASK;
933 memset(entry->ha, 0, dev->addr_len);
934 entry->hlen = dev->addr_len;
935 entry->htype = dev->type;
936 entry->dev = dev;
937 init_timer(&entry->timer);
938 entry->timer.function = arp_expire_request;
939 entry->timer.data = (unsigned long)entry;
940 entry->timer.expires = ARP_RES_TIME;
941 arp_tables[hash] = entry;
942 add_timer(&entry->timer);
943 entry->retries = ARP_MAX_TRIES;
944 skb_queue_head_init(&entry->skb);
945 if (skb != NULL)
946 {
947 skb_queue_tail(&entry->skb, skb);
948 skb_device_unlock(skb);
949 }
950 }
951 else
952 {
953 if (skb != NULL && skb->free)
954 kfree_skb(skb, FREE_WRITE);
955 }
956 sti();
957
958 /*
959 * If we didn't find an entry, we will try to send an ARP packet.
960 */
961
962 arp_send(ARPOP_REQUEST, ETH_P_ARP, paddr, dev, saddr, NULL,
963 dev->dev_addr);
964
965 return 1;
966 }
967
968
969 /*
970 * Write the contents of the ARP cache to a PROCfs file.
971 */
972
973 #define HBUFFERLEN 30
974
975 int arp_get_info(char *buffer, char **start, off_t offset, int length)
/* */
976 {
977 int len=0;
978 off_t begin=0;
979 off_t pos=0;
980 int size;
981 struct arp_table *entry;
982 char hbuffer[HBUFFERLEN];
983 int i,j,k;
984 const char hexbuf[] = "0123456789ABCDEF";
985
986 size = sprintf(buffer,"IP address HW type Flags HW address Mask\n");
987
988 pos+=size;
989 len+=size;
990
991 cli();
992 for(i=0; i<FULL_ARP_TABLE_SIZE; i++)
993 {
994 for(entry=arp_tables[i]; entry!=NULL; entry=entry->next)
995 {
996 /*
997 * Convert hardware address to XX:XX:XX:XX ... form.
998 */
999 #ifdef CONFIG_AX25
1000 #ifdef CONFIG_NETROM
1001 if (entry->htype == ARPHRD_AX25 || entry->htype == ARPHRD_NETROM)
1002 strcpy(hbuffer,ax2asc((ax25_address *)entry->ha));
1003 else {
1004 #else
1005 if(entry->htype==ARPHRD_AX25)
1006 strcpy(hbuffer,ax2asc((ax25_address *)entry->ha));
1007 else {
1008 #endif
1009 #endif
1010
1011 for(k=0,j=0;k<HBUFFERLEN-3 && j<entry->hlen;j++)
1012 {
1013 hbuffer[k++]=hexbuf[ (entry->ha[j]>>4)&15 ];
1014 hbuffer[k++]=hexbuf[ entry->ha[j]&15 ];
1015 hbuffer[k++]=':';
1016 }
1017 hbuffer[--k]=0;
1018
1019 #ifdef CONFIG_AX25
1020 }
1021 #endif
1022 size = sprintf(buffer+len,
1023 "%-17s0x%-10x0x%-10x%s",
1024 in_ntoa(entry->ip),
1025 (unsigned int)entry->htype,
1026 entry->flags,
1027 hbuffer);
1028 size += sprintf(buffer+len+size,
1029 " %-17s\n",
1030 entry->mask==DEF_ARP_NETMASK?
1031 "*":in_ntoa(entry->mask));
1032
1033 len+=size;
1034 pos=begin+len;
1035
1036 if(pos<offset)
1037 {
1038 len=0;
1039 begin=pos;
1040 }
1041 if(pos>offset+length)
1042 break;
1043 }
1044 }
1045 sti();
1046
1047 *start=buffer+(offset-begin); /* Start of wanted data */
1048 len-=(offset-begin); /* Start slop */
1049 if(len>length)
1050 len=length; /* Ending slop */
1051 return len;
1052 }
1053
1054
1055 /*
1056 * This will find an entry in the ARP table by looking at the IP address.
1057 * If proxy is PROXY_EXACT then only exact IP matches will be allowed
1058 * for proxy entries, otherwise the netmask will be used
1059 */
1060
1061 static struct arp_table *arp_lookup(unsigned long paddr, enum proxy proxy)
/* */
1062 {
1063 struct arp_table *entry;
1064 unsigned long hash = HASH(paddr);
1065
1066 for (entry = arp_tables[hash]; entry != NULL; entry = entry->next)
1067 if (entry->ip == paddr) break;
1068
1069 /* it's possibly a proxy entry (with a netmask) */
1070 if (!entry && proxy != PROXY_NONE)
1071 for (entry=arp_tables[PROXY_HASH]; entry != NULL; entry = entry->next)
1072 if ((proxy==PROXY_EXACT) ? (entry->ip==paddr)
1073 : !((entry->ip^paddr)&entry->mask))
1074 break;
1075
1076 return entry;
1077 }
1078
1079
1080 int arp_find_cache(unsigned char *dp, unsigned long daddr, struct device *dev)
/* */
1081 {
1082 /*
1083 * We need the broadcast/multicast awareness here and the find routine split up.
1084 */
1085 struct arp_table *entry;
1086 #ifdef CONFIG_IP_MULTICAST
1087 unsigned long taddr;
1088 #endif
1089
1090 switch (ip_chk_addr(daddr))
1091 {
1092 case IS_MYADDR:
1093 printk("ARP: arp called for own IP address\n");
1094 memcpy(dp, dev->dev_addr, dev->addr_len);
1095 return 1;
1096 #ifdef CONFIG_IP_MULTICAST
1097 case IS_MULTICAST:
1098 if(dev->type==ARPHRD_ETHER || dev->type==ARPHRD_IEEE802)
1099 {
1100 dp[0]=0x01;
1101 dp[1]=0x00;
1102 dp[2]=0x5e;
1103 taddr=ntohl(daddr);
1104 dp[5]=taddr&0xff;
1105 taddr=taddr>>8;
1106 dp[4]=taddr&0xff;
1107 taddr=taddr>>8;
1108 dp[3]=taddr&0x7f;
1109 return 1;
1110 }
1111 /*
1112 * If a device does not support multicast broadcast the stuff (eg AX.25 for now)
1113 */
1114 #endif
1115
1116 case IS_BROADCAST:
1117 memcpy(dp, dev->broadcast, dev->addr_len);
1118 return 1;
1119
1120 default:
1121 entry=arp_lookup(daddr, PROXY_NONE);
1122 if(entry)
1123 {
1124 memcpy(dp,entry->ha, ETH_ALEN);
1125 return 1;
1126 }
1127 }
1128 return 0;
1129 }
1130
1131 /*
1132 * Set (create) an ARP cache entry.
1133 */
1134
1135 static int arp_req_set(struct arpreq *req)
/* */
1136 {
1137 struct arpreq r;
1138 struct arp_table *entry;
1139 struct sockaddr_in *si;
1140 int htype, hlen;
1141 unsigned long ip;
1142 struct rtable *rt;
1143
1144 memcpy_fromfs(&r, req, sizeof(r));
1145
1146 /* We only understand about IP addresses... */
1147 if (r.arp_pa.sa_family != AF_INET)
1148 return -EPFNOSUPPORT;
1149
1150 /*
1151 * Find out about the hardware type.
1152 * We have to be compatible with BSD UNIX, so we have to
1153 * assume that a "not set" value (i.e. 0) means Ethernet.
1154 */
1155
1156 switch (r.arp_ha.sa_family) {
1157 case ARPHRD_ETHER:
1158 htype = ARPHRD_ETHER;
1159 hlen = ETH_ALEN;
1160 break;
1161
1162 case ARPHRD_ARCNET:
1163 htype = ARPHRD_ARCNET;
1164 hlen = 1; /* length of arcnet addresses */
1165 break;
1166
1167 #ifdef CONFIG_AX25
1168 case ARPHRD_AX25:
1169 htype = ARPHRD_AX25;
1170 hlen = 7;
1171 break;
1172 #endif
1173 #ifdef CONFIG_NETROM
1174 case ARPHRD_NETROM:
1175 htype = ARPHRD_NETROM;
1176 hlen = 7;
1177 break;
1178 #endif
1179 case ARPHRD_IEEE802:
1180 htype = ARPHRD_IEEE802;
1181 hlen = TR_ALEN;
1182 break;
1183 default:
1184 return -EPFNOSUPPORT;
1185 }
1186
1187 si = (struct sockaddr_in *) &r.arp_pa;
1188 ip = si->sin_addr.s_addr;
1189 if (ip == 0)
1190 {
1191 printk("ARP: SETARP: requested PA is 0.0.0.0 !\n");
1192 return -EINVAL;
1193 }
1194
1195 /*
1196 * Is it reachable directly ?
1197 */
1198
1199 rt = ip_rt_route(ip, NULL, NULL);
1200 if (rt == NULL)
1201 return -ENETUNREACH;
1202
1203 /*
1204 * Is there an existing entry for this address?
1205 */
1206
1207 cli();
1208
1209 /*
1210 * Find the entry
1211 */
1212 entry = arp_lookup(ip, PROXY_EXACT);
1213 if (entry && (entry->flags & ATF_PUBL) != (r.arp_flags & ATF_PUBL))
1214 {
1215 sti();
1216 arp_destroy(ip,1);
1217 cli();
1218 entry = NULL;
1219 }
1220
1221 /*
1222 * Do we need to create a new entry
1223 */
1224
1225 if (entry == NULL)
1226 {
1227 unsigned long hash = HASH(ip);
1228 if (r.arp_flags & ATF_PUBL)
1229 hash = PROXY_HASH;
1230
1231 entry = (struct arp_table *) kmalloc(sizeof(struct arp_table),
1232 GFP_ATOMIC);
1233 if (entry == NULL)
1234 {
1235 sti();
1236 return -ENOMEM;
1237 }
1238 entry->ip = ip;
1239 entry->hlen = hlen;
1240 entry->htype = htype;
1241 init_timer(&entry->timer);
1242 entry->next = arp_tables[hash];
1243 arp_tables[hash] = entry;
1244 skb_queue_head_init(&entry->skb);
1245 }
1246 /*
1247 * We now have a pointer to an ARP entry. Update it!
1248 */
1249
1250 memcpy(&entry->ha, &r.arp_ha.sa_data, hlen);
1251 entry->last_used = jiffies;
1252 entry->flags = r.arp_flags | ATF_COM;
1253 if ((entry->flags & ATF_PUBL) && (entry->flags & ATF_NETMASK))
1254 {
1255 si = (struct sockaddr_in *) &r.arp_netmask;
1256 entry->mask = si->sin_addr.s_addr;
1257 }
1258 else
1259 entry->mask = DEF_ARP_NETMASK;
1260 entry->dev = rt->rt_dev;
1261 arp_cache_stamp++;
1262 sti();
1263
1264 return 0;
1265 }
1266
1267
1268 /*
1269 * Get an ARP cache entry.
1270 */
1271
1272 static int arp_req_get(struct arpreq *req)
/* */
1273 {
1274 struct arpreq r;
1275 struct arp_table *entry;
1276 struct sockaddr_in *si;
1277
1278 /*
1279 * We only understand about IP addresses...
1280 */
1281
1282 memcpy_fromfs(&r, req, sizeof(r));
1283
1284 if (r.arp_pa.sa_family != AF_INET)
1285 return -EPFNOSUPPORT;
1286
1287 /*
1288 * Is there an existing entry for this address?
1289 */
1290
1291 si = (struct sockaddr_in *) &r.arp_pa;
1292 cli();
1293 entry = arp_lookup(si->sin_addr.s_addr,PROXY_ANY);
1294
1295 if (entry == NULL)
1296 {
1297 sti();
1298 return -ENXIO;
1299 }
1300
1301 /*
1302 * We found it; copy into structure.
1303 */
1304
1305 memcpy(r.arp_ha.sa_data, &entry->ha, entry->hlen);
1306 r.arp_ha.sa_family = entry->htype;
1307 r.arp_flags = entry->flags;
1308 sti();
1309
1310 /*
1311 * Copy the information back
1312 */
1313
1314 memcpy_tofs(req, &r, sizeof(r));
1315 return 0;
1316 }
1317
1318
1319 /*
1320 * Handle an ARP layer I/O control request.
1321 */
1322
1323 int arp_ioctl(unsigned int cmd, void *arg)
/* */
1324 {
1325 struct arpreq r;
1326 struct sockaddr_in *si;
1327 int err;
1328
1329 switch(cmd)
1330 {
1331 case SIOCDARP:
1332 if (!suser())
1333 return -EPERM;
1334 err = verify_area(VERIFY_READ, arg, sizeof(struct arpreq));
1335 if(err)
1336 return err;
1337 memcpy_fromfs(&r, arg, sizeof(r));
1338 if (r.arp_pa.sa_family != AF_INET)
1339 return -EPFNOSUPPORT;
1340 si = (struct sockaddr_in *) &r.arp_pa;
1341 arp_destroy(si->sin_addr.s_addr, 1);
1342 return 0;
1343 case SIOCGARP:
1344 err = verify_area(VERIFY_WRITE, arg, sizeof(struct arpreq));
1345 if(err)
1346 return err;
1347 return arp_req_get((struct arpreq *)arg);
1348 case SIOCSARP:
1349 if (!suser())
1350 return -EPERM;
1351 err = verify_area(VERIFY_READ, arg, sizeof(struct arpreq));
1352 if(err)
1353 return err;
1354 return arp_req_set((struct arpreq *)arg);
1355 default:
1356 return -EINVAL;
1357 }
1358 /*NOTREACHED*/
1359 return 0;
1360 }
1361
1362
1363 /*
1364 * Called once on startup.
1365 */
1366
1367 static struct packet_type arp_packet_type =
1368 {
1369 0, /* Should be: __constant_htons(ETH_P_ARP) - but this _doesn't_ come out constant! */
1370 NULL, /* All devices */
1371 arp_rcv,
1372 NULL,
1373 NULL
1374 };
1375
1376 static struct notifier_block arp_dev_notifier={
1377 arp_device_event,
1378 NULL,
1379 0
1380 };
1381
1382 void arp_init (void)
/* ![[last]](../icons/n_last.png)
*/
1383 {
1384 /* Register the packet type */
1385 arp_packet_type.type=htons(ETH_P_ARP);
1386 dev_add_pack(&arp_packet_type);
1387 /* Start with the regular checks for expired arp entries. */
1388 add_timer(&arp_timer);
1389 /* Register for device down reports */
1390 register_netdevice_notifier(&arp_dev_notifier);
1391 }
1392
![[bottom]](../icons/n_bottom.png){kind=icon}
*/