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*/
1 /*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * The Internet Protocol (IP) module.
7 *
8 * Version: @(#)ip.c 1.0.16b 9/1/93
9 *
10 * Authors: Ross Biro, <bir7@leland.Stanford.Edu>
11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Donald Becker, <becker@super.org>
13 * Alan Cox, <gw4pts@gw4pts.ampr.org>
14 *
15 * Fixes:
16 * Alan Cox : Commented a couple of minor bits of surplus code
17 * Alan Cox : Undefining IP_FORWARD doesn't include the code
18 * (just stops a compiler warning).
19 * Alan Cox : Frames with >=MAX_ROUTE record routes, strict routes or loose routes
20 * are junked rather than corrupting things.
21 * Alan Cox : Frames to bad broadcast subnets are dumped
22 * We used to process them non broadcast and
23 * boy could that cause havoc.
24 * Alan Cox : ip_forward sets the free flag on the
25 * new frame it queues. Still crap because
26 * it copies the frame but at least it
27 * doesn't eat memory too.
28 * Alan Cox : Generic queue code and memory fixes.
29 * Fred Van Kempen : IP fragment support (borrowed from NET2E)
30 * Gerhard Koerting: Forward fragmented frames correctly.
31 * Gerhard Koerting: Fixes to my fix of the above 8-).
32 * Gerhard Koerting: IP interface addressing fix.
33 * Linus Torvalds : More robustness checks
34 * Alan Cox : Even more checks: Still not as robust as it ought to be
35 * Alan Cox : Save IP header pointer for later
36 * Alan Cox : ip option setting
37 * Alan Cox : Use ip_tos/ip_ttl settings
38 * Alan Cox : Fragmentation bogosity removed
39 * (Thanks to Mark.Bush@prg.ox.ac.uk)
40 * Dmitry Gorodchanin : Send of a raw packet crash fix.
41 * Alan Cox : Silly ip bug when an overlength
42 * fragment turns up. Now frees the
43 * queue.
44 * Linus Torvalds/ : Memory leakage on fragmentation
45 * Alan Cox : handling.
46 * Gerhard Koerting: Forwarding uses IP priority hints
47 * Teemu Rantanen : Fragment problems.
48 * Alan Cox : General cleanup, comments and reformat
49 * Alan Cox : SNMP statistics
50 * Alan Cox : BSD address rule semantics. Also see
51 * UDP as there is a nasty checksum issue
52 * if you do things the wrong way.
53 * Alan Cox : Always defrag, moved IP_FORWARD to the config.in file
54 * Alan Cox : IP options adjust sk->priority.
55 * Pedro Roque : Fix mtu/length error in ip_forward.
56 * Alan Cox : Avoid ip_chk_addr when possible.
57 *
58 * To Fix:
59 * IP option processing is mostly not needed. ip_forward needs to know about routing rules
60 * and time stamp but that's about all. Use the route mtu field here too
61 *
62 * This program is free software; you can redistribute it and/or
63 * modify it under the terms of the GNU General Public License
64 * as published by the Free Software Foundation; either version
65 * 2 of the License, or (at your option) any later version.
66 */
67 #include <asm/segment.h>
68 #include <asm/system.h>
69 #include <linux/types.h>
70 #include <linux/kernel.h>
71 #include <linux/sched.h>
72 #include <linux/string.h>
73 #include <linux/errno.h>
74 #include <linux/socket.h>
75 #include <linux/sockios.h>
76 #include <linux/in.h>
77 #include <linux/inet.h>
78 #include <linux/netdevice.h>
79 #include <linux/etherdevice.h>
80 #include "snmp.h"
81 #include "ip.h"
82 #include "protocol.h"
83 #include "route.h"
84 #include "tcp.h"
85 #include <linux/skbuff.h>
86 #include "sock.h"
87 #include "arp.h"
88 #include "icmp.h"
89
90 #define CONFIG_IP_DEFRAG
91
92 extern int last_retran;
93 extern void sort_send(struct sock *sk);
94
95 #define min(a,b) ((a)<(b)?(a):(b))
96 #define LOOPBACK(x) (((x) & htonl(0xff000000)) == htonl(0x7f000000))
97
98 /*
99 * SNMP management statistics
100 */
101
102 struct ip_mib ip_statistics={1,64,}; /* Forwarding=Yes, Default TTL=64 */
103
104 /*
105 * Handle the issuing of an ioctl() request
106 * for the ip device. This is scheduled to
107 * disappear
108 */
109
110 int ip_ioctl(struct sock *sk, int cmd, unsigned long arg)
/* ![[next]](../icons/right.png)
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*/
111 {
112 switch(cmd)
113 {
114 default:
115 return(-EINVAL);
116 }
117 }
118
119
120 /* these two routines will do routing. */
121
122 static void
123 strict_route(struct iphdr *iph, struct options *opt)
/* ![[previous]](../icons/left.png)
*/
124 {
125 }
126
127
128 static void
129 loose_route(struct iphdr *iph, struct options *opt)
/* */
130 {
131 }
132
133
134
135
136 /* This routine will check to see if we have lost a gateway. */
137 void
138 ip_route_check(unsigned long daddr)
/* */
139 {
140 }
141
142
143 #if 0
144 /* this routine puts the options at the end of an ip header. */
145 static int
146 build_options(struct iphdr *iph, struct options *opt)
/* */
147 {
148 unsigned char *ptr;
149 /* currently we don't support any options. */
150 ptr = (unsigned char *)(iph+1);
151 *ptr = 0;
152 return (4);
153 }
154 #endif
155
156
157 /*
158 * Take an skb, and fill in the MAC header.
159 */
160
161 static int ip_send(struct sk_buff *skb, unsigned long daddr, int len, struct device *dev, unsigned long saddr)
/* */
162 {
163 int mac = 0;
164
165 skb->dev = dev;
166 skb->arp = 1;
167 if (dev->hard_header)
168 {
169 /*
170 * Build a hardware header. Source address is our mac, destination unknown
171 * (rebuild header will sort this out)
172 */
173 mac = dev->hard_header(skb->data, dev, ETH_P_IP, NULL, NULL, len, skb);
174 if (mac < 0)
175 {
176 mac = -mac;
177 skb->arp = 0;
178 skb->raddr = daddr; /* next routing address */
179 }
180 }
181 return mac;
182 }
183
184 int ip_id_count = 0;
185
186 /*
187 * This routine builds the appropriate hardware/IP headers for
188 * the routine. It assumes that if *dev != NULL then the
189 * protocol knows what it's doing, otherwise it uses the
190 * routing/ARP tables to select a device struct.
191 */
192 int ip_build_header(struct sk_buff *skb, unsigned long saddr, unsigned long daddr,
/* */
193 struct device **dev, int type, struct options *opt, int len, int tos, int ttl)
194 {
195 static struct options optmem;
196 struct iphdr *iph;
197 struct rtable *rt;
198 unsigned char *buff;
199 unsigned long raddr;
200 int tmp;
201 unsigned long src;
202
203 /*
204 * If there is no 'from' address as yet, then make it our loopback
205 */
206
207 if (saddr == 0)
208 saddr = ip_my_addr();
209
210 buff = skb->data;
211
212 /*
213 * See if we need to look up the device.
214 */
215
216 if (*dev == NULL)
217 {
218 if(skb->localroute)
219 rt = ip_rt_local(daddr, &optmem, &src);
220 else
221 rt = ip_rt_route(daddr, &optmem, &src);
222 if (rt == NULL)
223 {
224 ip_statistics.IpOutNoRoutes++;
225 return(-ENETUNREACH);
226 }
227
228 *dev = rt->rt_dev;
229 /*
230 * If the frame is from us and going off machine it MUST MUST MUST
231 * have the output device ip address and never the loopback
232 */
233 if (LOOPBACK(saddr) && !LOOPBACK(daddr))
234 saddr = src;/*rt->rt_dev->pa_addr;*/
235 raddr = rt->rt_gateway;
236
237 opt = &optmem;
238 }
239 else
240 {
241 /*
242 * We still need the address of the first hop.
243 */
244 if(skb->localroute)
245 rt = ip_rt_local(daddr, &optmem, &src);
246 else
247 rt = ip_rt_route(daddr, &optmem, &src);
248 /*
249 * If the frame is from us and going off machine it MUST MUST MUST
250 * have the output device ip address and never the loopback
251 */
252 if (LOOPBACK(saddr) && !LOOPBACK(daddr))
253 saddr = src;/*rt->rt_dev->pa_addr;*/
254
255 raddr = (rt == NULL) ? 0 : rt->rt_gateway;
256 }
257
258 /*
259 * No gateway so aim at the real destination
260 */
261 if (raddr == 0)
262 raddr = daddr;
263
264 /*
265 * Now build the MAC header.
266 */
267
268 tmp = ip_send(skb, raddr, len, *dev, saddr);
269 buff += tmp;
270 len -= tmp;
271
272 /*
273 * Book keeping
274 */
275
276 skb->dev = *dev;
277 skb->saddr = saddr;
278 if (skb->sk)
279 skb->sk->saddr = saddr;
280
281 /*
282 * Now build the IP header.
283 */
284
285 /*
286 * If we are using IPPROTO_RAW, then we don't need an IP header, since
287 * one is being supplied to us by the user
288 */
289
290 if(type == IPPROTO_RAW)
291 return (tmp);
292
293 iph = (struct iphdr *)buff;
294 iph->version = 4;
295 iph->tos = tos;
296 iph->frag_off = 0;
297 iph->ttl = ttl;
298 iph->daddr = daddr;
299 iph->saddr = saddr;
300 iph->protocol = type;
301 iph->ihl = 5;
302
303 /* Setup the IP options. */
304 #ifdef Not_Yet_Avail
305 build_options(iph, opt);
306 #endif
307
308 return(20 + tmp); /* IP header plus MAC header size */
309 }
310
311
312 static int
313 do_options(struct iphdr *iph, struct options *opt)
/* */
314 {
315 unsigned char *buff;
316 int done = 0;
317 int i, len = sizeof(struct iphdr);
318
319 /* Zero out the options. */
320 opt->record_route.route_size = 0;
321 opt->loose_route.route_size = 0;
322 opt->strict_route.route_size = 0;
323 opt->tstamp.ptr = 0;
324 opt->security = 0;
325 opt->compartment = 0;
326 opt->handling = 0;
327 opt->stream = 0;
328 opt->tcc = 0;
329 return(0);
330
331 /* Advance the pointer to start at the options. */
332 buff = (unsigned char *)(iph + 1);
333
334 /* Now start the processing. */
335 while (!done && len < iph->ihl*4) switch(*buff) {
336 case IPOPT_END:
337 done = 1;
338 break;
339 case IPOPT_NOOP:
340 buff++;
341 len++;
342 break;
343 case IPOPT_SEC:
344 buff++;
345 if (*buff != 11) return(1);
346 buff++;
347 opt->security = ntohs(*(unsigned short *)buff);
348 buff += 2;
349 opt->compartment = ntohs(*(unsigned short *)buff);
350 buff += 2;
351 opt->handling = ntohs(*(unsigned short *)buff);
352 buff += 2;
353 opt->tcc = ((*buff) << 16) + ntohs(*(unsigned short *)(buff+1));
354 buff += 3;
355 len += 11;
356 break;
357 case IPOPT_LSRR:
358 buff++;
359 if ((*buff - 3)% 4 != 0) return(1);
360 len += *buff;
361 opt->loose_route.route_size = (*buff -3)/4;
362 buff++;
363 if (*buff % 4 != 0) return(1);
364 opt->loose_route.pointer = *buff/4 - 1;
365 buff++;
366 buff++;
367 for (i = 0; i < opt->loose_route.route_size; i++) {
368 if(i>=MAX_ROUTE)
369 return(1);
370 opt->loose_route.route[i] = *(unsigned long *)buff;
371 buff += 4;
372 }
373 break;
374 case IPOPT_SSRR:
375 buff++;
376 if ((*buff - 3)% 4 != 0) return(1);
377 len += *buff;
378 opt->strict_route.route_size = (*buff -3)/4;
379 buff++;
380 if (*buff % 4 != 0) return(1);
381 opt->strict_route.pointer = *buff/4 - 1;
382 buff++;
383 buff++;
384 for (i = 0; i < opt->strict_route.route_size; i++) {
385 if(i>=MAX_ROUTE)
386 return(1);
387 opt->strict_route.route[i] = *(unsigned long *)buff;
388 buff += 4;
389 }
390 break;
391 case IPOPT_RR:
392 buff++;
393 if ((*buff - 3)% 4 != 0) return(1);
394 len += *buff;
395 opt->record_route.route_size = (*buff -3)/4;
396 buff++;
397 if (*buff % 4 != 0) return(1);
398 opt->record_route.pointer = *buff/4 - 1;
399 buff++;
400 buff++;
401 for (i = 0; i < opt->record_route.route_size; i++) {
402 if(i>=MAX_ROUTE)
403 return 1;
404 opt->record_route.route[i] = *(unsigned long *)buff;
405 buff += 4;
406 }
407 break;
408 case IPOPT_SID:
409 len += 4;
410 buff +=2;
411 opt->stream = *(unsigned short *)buff;
412 buff += 2;
413 break;
414 case IPOPT_TIMESTAMP:
415 buff++;
416 len += *buff;
417 if (*buff % 4 != 0) return(1);
418 opt->tstamp.len = *buff / 4 - 1;
419 buff++;
420 if ((*buff - 1) % 4 != 0) return(1);
421 opt->tstamp.ptr = (*buff-1)/4;
422 buff++;
423 opt->tstamp.x.full_char = *buff;
424 buff++;
425 for (i = 0; i < opt->tstamp.len; i++) {
426 opt->tstamp.data[i] = *(unsigned long *)buff;
427 buff += 4;
428 }
429 break;
430 default:
431 return(1);
432 }
433
434 if (opt->record_route.route_size == 0) {
435 if (opt->strict_route.route_size != 0) {
436 memcpy(&(opt->record_route), &(opt->strict_route),
437 sizeof(opt->record_route));
438 } else if (opt->loose_route.route_size != 0) {
439 memcpy(&(opt->record_route), &(opt->loose_route),
440 sizeof(opt->record_route));
441 }
442 }
443
444 if (opt->strict_route.route_size != 0 &&
445 opt->strict_route.route_size != opt->strict_route.pointer) {
446 strict_route(iph, opt);
447 return(0);
448 }
449
450 if (opt->loose_route.route_size != 0 &&
451 opt->loose_route.route_size != opt->loose_route.pointer) {
452 loose_route(iph, opt);
453 return(0);
454 }
455
456 return(0);
457 }
458
459 /*
460 * This is a version of ip_compute_csum() optimized for IP headers, which
461 * always checksum on 4 octet boundaries.
462 */
463
464 static inline unsigned short ip_fast_csum(unsigned char * buff, int wlen)
/* */
465 {
466 unsigned long sum = 0;
467
468 if (wlen)
469 {
470 unsigned long bogus;
471 __asm__("clc\n"
472 "1:\t"
473 "lodsl\n\t"
474 "adcl %3, %0\n\t"
475 "decl %2\n\t"
476 "jne 1b\n\t"
477 "adcl $0, %0\n\t"
478 "movl %0, %3\n\t"
479 "shrl $16, %3\n\t"
480 "addw %w3, %w0\n\t"
481 "adcw $0, %w0"
482 : "=r" (sum), "=S" (buff), "=r" (wlen), "=a" (bogus)
483 : "0" (sum), "1" (buff), "2" (wlen));
484 }
485 return (~sum) & 0xffff;
486 }
487
488 /*
489 * This routine does all the checksum computations that don't
490 * require anything special (like copying or special headers).
491 */
492
493 unsigned short ip_compute_csum(unsigned char * buff, int len)
/* */
494 {
495 unsigned long sum = 0;
496
497 /* Do the first multiple of 4 bytes and convert to 16 bits. */
498 if (len > 3)
499 {
500 __asm__("clc\n"
501 "1:\t"
502 "lodsl\n\t"
503 "adcl %%eax, %%ebx\n\t"
504 "loop 1b\n\t"
505 "adcl $0, %%ebx\n\t"
506 "movl %%ebx, %%eax\n\t"
507 "shrl $16, %%eax\n\t"
508 "addw %%ax, %%bx\n\t"
509 "adcw $0, %%bx"
510 : "=b" (sum) , "=S" (buff)
511 : "0" (sum), "c" (len >> 2) ,"1" (buff)
512 : "ax", "cx", "si", "bx" );
513 }
514 if (len & 2)
515 {
516 __asm__("lodsw\n\t"
517 "addw %%ax, %%bx\n\t"
518 "adcw $0, %%bx"
519 : "=b" (sum), "=S" (buff)
520 : "0" (sum), "1" (buff)
521 : "bx", "ax", "si");
522 }
523 if (len & 1)
524 {
525 __asm__("lodsb\n\t"
526 "movb $0, %%ah\n\t"
527 "addw %%ax, %%bx\n\t"
528 "adcw $0, %%bx"
529 : "=b" (sum), "=S" (buff)
530 : "0" (sum), "1" (buff)
531 : "bx", "ax", "si");
532 }
533 sum =~sum;
534 return(sum & 0xffff);
535 }
536
537 /*
538 * Check the header of an incoming IP datagram. This version is still used in slhc.c.
539 */
540
541 int ip_csum(struct iphdr *iph)
/* */
542 {
543 return ip_fast_csum((unsigned char *)iph, iph->ihl);
544 }
545
546 /*
547 * Generate a checksum for an outgoing IP datagram.
548 */
549
550 static void ip_send_check(struct iphdr *iph)
/* */
551 {
552 iph->check = 0;
553 iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
554 }
555
556 /************************ Fragment Handlers From NET2E not yet with tweaks to beat 4K **********************************/
557
558
559 /*
560 * This fragment handler is a bit of a heap. On the other hand it works quite
561 * happily and handles things quite well.
562 */
563
564 static struct ipq *ipqueue = NULL; /* IP fragment queue */
565
566 /*
567 * Create a new fragment entry.
568 */
569
570 static struct ipfrag *ip_frag_create(int offset, int end, struct sk_buff *skb, unsigned char *ptr)
/* */
571 {
572 struct ipfrag *fp;
573
574 fp = (struct ipfrag *) kmalloc(sizeof(struct ipfrag), GFP_ATOMIC);
575 if (fp == NULL)
576 {
577 printk("IP: frag_create: no memory left !\n");
578 return(NULL);
579 }
580 memset(fp, 0, sizeof(struct ipfrag));
581
582 /* Fill in the structure. */
583 fp->offset = offset;
584 fp->end = end;
585 fp->len = end - offset;
586 fp->skb = skb;
587 fp->ptr = ptr;
588
589 return(fp);
590 }
591
592
593 /*
594 * Find the correct entry in the "incomplete datagrams" queue for
595 * this IP datagram, and return the queue entry address if found.
596 */
597
598 static struct ipq *ip_find(struct iphdr *iph)
/* */
599 {
600 struct ipq *qp;
601 struct ipq *qplast;
602
603 cli();
604 qplast = NULL;
605 for(qp = ipqueue; qp != NULL; qplast = qp, qp = qp->next)
606 {
607 if (iph->id== qp->iph->id && iph->saddr == qp->iph->saddr &&
608 iph->daddr == qp->iph->daddr && iph->protocol == qp->iph->protocol)
609 {
610 del_timer(&qp->timer); /* So it doesn't vanish on us. The timer will be reset anyway */
611 sti();
612 return(qp);
613 }
614 }
615 sti();
616 return(NULL);
617 }
618
619
620 /*
621 * Remove an entry from the "incomplete datagrams" queue, either
622 * because we completed, reassembled and processed it, or because
623 * it timed out.
624 */
625
626 static void ip_free(struct ipq *qp)
/* */
627 {
628 struct ipfrag *fp;
629 struct ipfrag *xp;
630
631 /*
632 * Stop the timer for this entry.
633 */
634
635 del_timer(&qp->timer);
636
637 /* Remove this entry from the "incomplete datagrams" queue. */
638 cli();
639 if (qp->prev == NULL)
640 {
641 ipqueue = qp->next;
642 if (ipqueue != NULL)
643 ipqueue->prev = NULL;
644 }
645 else
646 {
647 qp->prev->next = qp->next;
648 if (qp->next != NULL)
649 qp->next->prev = qp->prev;
650 }
651
652 /* Release all fragment data. */
653
654 fp = qp->fragments;
655 while (fp != NULL)
656 {
657 xp = fp->next;
658 IS_SKB(fp->skb);
659 kfree_skb(fp->skb,FREE_READ);
660 kfree_s(fp, sizeof(struct ipfrag));
661 fp = xp;
662 }
663
664 /* Release the MAC header. */
665 kfree_s(qp->mac, qp->maclen);
666
667 /* Release the IP header. */
668 kfree_s(qp->iph, qp->ihlen + 8);
669
670 /* Finally, release the queue descriptor itself. */
671 kfree_s(qp, sizeof(struct ipq));
672 sti();
673 }
674
675
676 /*
677 * Oops- a fragment queue timed out. Kill it and send an ICMP reply.
678 */
679
680 static void ip_expire(unsigned long arg)
/* */
681 {
682 struct ipq *qp;
683
684 qp = (struct ipq *)arg;
685
686 /*
687 * Send an ICMP "Fragment Reassembly Timeout" message.
688 */
689
690 ip_statistics.IpReasmTimeout++;
691 ip_statistics.IpReasmFails++;
692 /* This if is always true... shrug */
693 if(qp->fragments!=NULL)
694 icmp_send(qp->fragments->skb,ICMP_TIME_EXCEEDED,
695 ICMP_EXC_FRAGTIME, qp->dev);
696
697 /*
698 * Nuke the fragment queue.
699 */
700 ip_free(qp);
701 }
702
703
704 /*
705 * Add an entry to the 'ipq' queue for a newly received IP datagram.
706 * We will (hopefully :-) receive all other fragments of this datagram
707 * in time, so we just create a queue for this datagram, in which we
708 * will insert the received fragments at their respective positions.
709 */
710
711 static struct ipq *ip_create(struct sk_buff *skb, struct iphdr *iph, struct device *dev)
/* */
712 {
713 struct ipq *qp;
714 int maclen;
715 int ihlen;
716
717 qp = (struct ipq *) kmalloc(sizeof(struct ipq), GFP_ATOMIC);
718 if (qp == NULL)
719 {
720 printk("IP: create: no memory left !\n");
721 return(NULL);
722 skb->dev = qp->dev;
723 }
724 memset(qp, 0, sizeof(struct ipq));
725
726 /*
727 * Allocate memory for the MAC header.
728 *
729 * FIXME: We have a maximum MAC address size limit and define
730 * elsewhere. We should use it here and avoid the 3 kmalloc() calls
731 */
732
733 maclen = ((unsigned long) iph) - ((unsigned long) skb->data);
734 qp->mac = (unsigned char *) kmalloc(maclen, GFP_ATOMIC);
735 if (qp->mac == NULL)
736 {
737 printk("IP: create: no memory left !\n");
738 kfree_s(qp, sizeof(struct ipq));
739 return(NULL);
740 }
741
742 /*
743 * Allocate memory for the IP header (plus 8 octets for ICMP).
744 */
745
746 ihlen = (iph->ihl * sizeof(unsigned long));
747 qp->iph = (struct iphdr *) kmalloc(ihlen + 8, GFP_ATOMIC);
748 if (qp->iph == NULL)
749 {
750 printk("IP: create: no memory left !\n");
751 kfree_s(qp->mac, maclen);
752 kfree_s(qp, sizeof(struct ipq));
753 return(NULL);
754 }
755
756 /* Fill in the structure. */
757 memcpy(qp->mac, skb->data, maclen);
758 memcpy(qp->iph, iph, ihlen + 8);
759 qp->len = 0;
760 qp->ihlen = ihlen;
761 qp->maclen = maclen;
762 qp->fragments = NULL;
763 qp->dev = dev;
764
765 /* Start a timer for this entry. */
766 qp->timer.expires = IP_FRAG_TIME; /* about 30 seconds */
767 qp->timer.data = (unsigned long) qp; /* pointer to queue */
768 qp->timer.function = ip_expire; /* expire function */
769 add_timer(&qp->timer);
770
771 /* Add this entry to the queue. */
772 qp->prev = NULL;
773 cli();
774 qp->next = ipqueue;
775 if (qp->next != NULL)
776 qp->next->prev = qp;
777 ipqueue = qp;
778 sti();
779 return(qp);
780 }
781
782
783 /*
784 * See if a fragment queue is complete.
785 */
786
787 static int ip_done(struct ipq *qp)
/* */
788 {
789 struct ipfrag *fp;
790 int offset;
791
792 /* Only possible if we received the final fragment. */
793 if (qp->len == 0)
794 return(0);
795
796 /* Check all fragment offsets to see if they connect. */
797 fp = qp->fragments;
798 offset = 0;
799 while (fp != NULL)
800 {
801 if (fp->offset > offset)
802 return(0); /* fragment(s) missing */
803 offset = fp->end;
804 fp = fp->next;
805 }
806
807 /* All fragments are present. */
808 return(1);
809 }
810
811
812 /*
813 * Build a new IP datagram from all its fragments.
814 *
815 * FIXME: We copy here because we lack an effective way of handling lists
816 * of bits on input. Until the new skb data handling is in I'm not going
817 * to touch this with a bargepole. This also causes a 4Kish limit on
818 * packet sizes.
819 */
820
821 static struct sk_buff *ip_glue(struct ipq *qp)
/* */
822 {
823 struct sk_buff *skb;
824 struct iphdr *iph;
825 struct ipfrag *fp;
826 unsigned char *ptr;
827 int count, len;
828
829 /*
830 * Allocate a new buffer for the datagram.
831 */
832
833 len = qp->maclen + qp->ihlen + qp->len;
834
835 if ((skb = alloc_skb(len,GFP_ATOMIC)) == NULL)
836 {
837 ip_statistics.IpReasmFails++;
838 printk("IP: queue_glue: no memory for gluing queue 0x%X\n", (int) qp);
839 ip_free(qp);
840 return(NULL);
841 }
842
843 /* Fill in the basic details. */
844 skb->len = (len - qp->maclen);
845 skb->h.raw = skb->data;
846 skb->free = 1;
847
848 /* Copy the original MAC and IP headers into the new buffer. */
849 ptr = (unsigned char *) skb->h.raw;
850 memcpy(ptr, ((unsigned char *) qp->mac), qp->maclen);
851 ptr += qp->maclen;
852 memcpy(ptr, ((unsigned char *) qp->iph), qp->ihlen);
853 ptr += qp->ihlen;
854 skb->h.raw += qp->maclen;
855
856 count = 0;
857
858 /* Copy the data portions of all fragments into the new buffer. */
859 fp = qp->fragments;
860 while(fp != NULL)
861 {
862 if(count+fp->len>skb->len)
863 {
864 printk("Invalid fragment list: Fragment over size.\n");
865 ip_free(qp);
866 kfree_skb(skb,FREE_WRITE);
867 ip_statistics.IpReasmFails++;
868 return NULL;
869 }
870 memcpy((ptr + fp->offset), fp->ptr, fp->len);
871 count += fp->len;
872 fp = fp->next;
873 }
874
875 /* We glued together all fragments, so remove the queue entry. */
876 ip_free(qp);
877
878 /* Done with all fragments. Fixup the new IP header. */
879 iph = skb->h.iph;
880 iph->frag_off = 0;
881 iph->tot_len = htons((iph->ihl * sizeof(unsigned long)) + count);
882 skb->ip_hdr = iph;
883
884 ip_statistics.IpReasmOKs++;
885 return(skb);
886 }
887
888
889 /*
890 * Process an incoming IP datagram fragment.
891 */
892
893 static struct sk_buff *ip_defrag(struct iphdr *iph, struct sk_buff *skb, struct device *dev)
/* */
894 {
895 struct ipfrag *prev, *next;
896 struct ipfrag *tfp;
897 struct ipq *qp;
898 struct sk_buff *skb2;
899 unsigned char *ptr;
900 int flags, offset;
901 int i, ihl, end;
902
903 ip_statistics.IpReasmReqds++;
904
905 /* Find the entry of this IP datagram in the "incomplete datagrams" queue. */
906 qp = ip_find(iph);
907
908 /* Is this a non-fragmented datagram? */
909 offset = ntohs(iph->frag_off);
910 flags = offset & ~IP_OFFSET;
911 offset &= IP_OFFSET;
912 if (((flags & IP_MF) == 0) && (offset == 0))
913 {
914 if (qp != NULL)
915 ip_free(qp); /* Huh? How could this exist?? */
916 return(skb);
917 }
918
919 offset <<= 3; /* offset is in 8-byte chunks */
920
921 /*
922 * If the queue already existed, keep restarting its timer as long
923 * as we still are receiving fragments. Otherwise, create a fresh
924 * queue entry.
925 */
926
927 if (qp != NULL)
928 {
929 del_timer(&qp->timer);
930 qp->timer.expires = IP_FRAG_TIME; /* about 30 seconds */
931 qp->timer.data = (unsigned long) qp; /* pointer to queue */
932 qp->timer.function = ip_expire; /* expire function */
933 add_timer(&qp->timer);
934 }
935 else
936 {
937 /*
938 * If we failed to create it, then discard the frame
939 */
940 if ((qp = ip_create(skb, iph, dev)) == NULL)
941 {
942 skb->sk = NULL;
943 kfree_skb(skb, FREE_READ);
944 ip_statistics.IpReasmFails++;
945 return NULL;
946 }
947 }
948
949 /*
950 * Determine the position of this fragment.
951 */
952
953 ihl = (iph->ihl * sizeof(unsigned long));
954 end = offset + ntohs(iph->tot_len) - ihl;
955
956 /*
957 * Point into the IP datagram 'data' part.
958 */
959
960 ptr = skb->data + dev->hard_header_len + ihl;
961
962 /*
963 * Is this the final fragment?
964 */
965
966 if ((flags & IP_MF) == 0)
967 qp->len = end;
968
969 /*
970 * Find out which fragments are in front and at the back of us
971 * in the chain of fragments so far. We must know where to put
972 * this fragment, right?
973 */
974
975 prev = NULL;
976 for(next = qp->fragments; next != NULL; next = next->next)
977 {
978 if (next->offset > offset)
979 break; /* bingo! */
980 prev = next;
981 }
982
983 /*
984 * We found where to put this one.
985 * Check for overlap with preceding fragment, and, if needed,
986 * align things so that any overlaps are eliminated.
987 */
988 if (prev != NULL && offset < prev->end)
989 {
990 i = prev->end - offset;
991 offset += i; /* ptr into datagram */
992 ptr += i; /* ptr into fragment data */
993 }
994
995 /*
996 * Look for overlap with succeeding segments.
997 * If we can merge fragments, do it.
998 */
999
1000 for(; next != NULL; next = tfp)
1001 {
1002 tfp = next->next;
1003 if (next->offset >= end)
1004 break; /* no overlaps at all */
1005
1006 i = end - next->offset; /* overlap is 'i' bytes */
1007 next->len -= i; /* so reduce size of */
1008 next->offset += i; /* next fragment */
1009 next->ptr += i;
1010
1011 /*
1012 * If we get a frag size of <= 0, remove it and the packet
1013 * that it goes with.
1014 */
1015 if (next->len <= 0)
1016 {
1017 if (next->prev != NULL)
1018 next->prev->next = next->next;
1019 else
1020 qp->fragments = next->next;
1021
1022 if (tfp->next != NULL)
1023 next->next->prev = next->prev;
1024
1025 kfree_skb(next->skb,FREE_READ);
1026 kfree_s(next, sizeof(struct ipfrag));
1027 }
1028 }
1029
1030 /*
1031 * Insert this fragment in the chain of fragments.
1032 */
1033
1034 tfp = NULL;
1035 tfp = ip_frag_create(offset, end, skb, ptr);
1036
1037 /*
1038 * No memory to save the fragment - so throw the lot
1039 */
1040
1041 if (!tfp)
1042 {
1043 skb->sk = NULL;
1044 kfree_skb(skb, FREE_READ);
1045 return NULL;
1046 }
1047 tfp->prev = prev;
1048 tfp->next = next;
1049 if (prev != NULL)
1050 prev->next = tfp;
1051 else
1052 qp->fragments = tfp;
1053
1054 if (next != NULL)
1055 next->prev = tfp;
1056
1057 /*
1058 * OK, so we inserted this new fragment into the chain.
1059 * Check if we now have a full IP datagram which we can
1060 * bump up to the IP layer...
1061 */
1062
1063 if (ip_done(qp))
1064 {
1065 skb2 = ip_glue(qp); /* glue together the fragments */
1066 return(skb2);
1067 }
1068 return(NULL);
1069 }
1070
1071
1072 /*
1073 * This IP datagram is too large to be sent in one piece. Break it up into
1074 * smaller pieces (each of size equal to the MAC header plus IP header plus
1075 * a block of the data of the original IP data part) that will yet fit in a
1076 * single device frame, and queue such a frame for sending by calling the
1077 * ip_queue_xmit(). Note that this is recursion, and bad things will happen
1078 * if this function causes a loop...
1079 *
1080 * Yes this is inefficient, feel free to submit a quicker one.
1081 *
1082 * **Protocol Violation**
1083 * We copy all the options to each fragment. !FIXME!
1084 */
1085 void ip_fragment(struct sock *sk, struct sk_buff *skb, struct device *dev, int is_frag)
/* */
1086 {
1087 struct iphdr *iph;
1088 unsigned char *raw;
1089 unsigned char *ptr;
1090 struct sk_buff *skb2;
1091 int left, mtu, hlen, len;
1092 int offset;
1093 unsigned long flags;
1094
1095 /*
1096 * Point into the IP datagram header.
1097 */
1098
1099 raw = skb->data;
1100 iph = (struct iphdr *) (raw + dev->hard_header_len);
1101
1102 skb->ip_hdr = iph;
1103
1104 /*
1105 * Setup starting values.
1106 */
1107
1108 hlen = (iph->ihl * sizeof(unsigned long));
1109 left = ntohs(iph->tot_len) - hlen; /* Space per frame */
1110 hlen += dev->hard_header_len; /* Total header size */
1111 mtu = (dev->mtu - hlen); /* Size of data space */
1112 ptr = (raw + hlen); /* Where to start from */
1113
1114 /*
1115 * Check for any "DF" flag. [DF means do not fragment]
1116 */
1117
1118 if (ntohs(iph->frag_off) & IP_DF)
1119 {
1120 ip_statistics.IpFragFails++;
1121 icmp_send(skb,ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, dev);
1122 return;
1123 }
1124
1125 /*
1126 * The protocol doesn't seem to say what to do in the case that the
1127 * frame + options doesn't fit the mtu. As it used to fall down dead
1128 * in this case we were fortunate it didn't happen
1129 */
1130
1131 if(mtu<8)
1132 {
1133 /* It's wrong but its better than nothing */
1134 icmp_send(skb,ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED,dev);
1135 ip_statistics.IpFragFails++;
1136 return;
1137 }
1138
1139 /*
1140 * Fragment the datagram.
1141 */
1142
1143 /*
1144 * The initial offset is 0 for a complete frame. When
1145 * fragmenting fragments its wherever this one starts.
1146 */
1147
1148 if (is_frag & 2)
1149 offset = (ntohs(iph->frag_off) & 0x1fff) << 3;
1150 else
1151 offset = 0;
1152
1153
1154 /*
1155 * Keep copying data until we run out.
1156 */
1157
1158 while(left > 0)
1159 {
1160 len = left;
1161 /* IF: it doesn't fit, use 'mtu' - the data space left */
1162 if (len > mtu)
1163 len = mtu;
1164 /* IF: we are not sending upto and including the packet end
1165 then align the next start on an eight byte boundary */
1166 if (len < left)
1167 {
1168 len/=8;
1169 len*=8;
1170 }
1171 /*
1172 * Allocate buffer.
1173 */
1174
1175 if ((skb2 = alloc_skb(len + hlen,GFP_ATOMIC)) == NULL)
1176 {
1177 printk("IP: frag: no memory for new fragment!\n");
1178 ip_statistics.IpFragFails++;
1179 return;
1180 }
1181
1182 /*
1183 * Set up data on packet
1184 */
1185
1186 skb2->arp = skb->arp;
1187 if(skb->free==0)
1188 printk("IP fragmenter: BUG free!=1 in fragmenter\n");
1189 skb2->free = 1;
1190 skb2->len = len + hlen;
1191 skb2->h.raw=(char *) skb2->data;
1192 /*
1193 * Charge the memory for the fragment to any owner
1194 * it might possess
1195 */
1196
1197 save_flags(flags);
1198 if (sk)
1199 {
1200 cli();
1201 sk->wmem_alloc += skb2->mem_len;
1202 skb2->sk=sk;
1203 }
1204 restore_flags(flags);
1205 skb2->raddr = skb->raddr; /* For rebuild_header - must be here */
1206
1207 /*
1208 * Copy the packet header into the new buffer.
1209 */
1210
1211 memcpy(skb2->h.raw, raw, hlen);
1212
1213 /*
1214 * Copy a block of the IP datagram.
1215 */
1216 memcpy(skb2->h.raw + hlen, ptr, len);
1217 left -= len;
1218
1219 skb2->h.raw+=dev->hard_header_len;
1220
1221 /*
1222 * Fill in the new header fields.
1223 */
1224 iph = (struct iphdr *)(skb2->h.raw/*+dev->hard_header_len*/);
1225 iph->frag_off = htons((offset >> 3));
1226 /*
1227 * Added AC : If we are fragmenting a fragment thats not the
1228 * last fragment then keep MF on each bit
1229 */
1230 if (left > 0 || (is_frag & 1))
1231 iph->frag_off |= htons(IP_MF);
1232 ptr += len;
1233 offset += len;
1234
1235 /*
1236 * Put this fragment into the sending queue.
1237 */
1238
1239 ip_statistics.IpFragCreates++;
1240
1241 ip_queue_xmit(sk, dev, skb2, 2);
1242 }
1243 ip_statistics.IpFragOKs++;
1244 }
1245
1246
1247
1248 #ifdef CONFIG_IP_FORWARD
1249
1250 /*
1251 * Forward an IP datagram to its next destination.
1252 */
1253
1254 static void ip_forward(struct sk_buff *skb, struct device *dev, int is_frag)
/* */
1255 {
1256 struct device *dev2; /* Output device */
1257 struct iphdr *iph; /* Our header */
1258 struct sk_buff *skb2; /* Output packet */
1259 struct rtable *rt; /* Route we use */
1260 unsigned char *ptr; /* Data pointer */
1261 unsigned long raddr; /* Router IP address */
1262
1263 /*
1264 * According to the RFC, we must first decrease the TTL field. If
1265 * that reaches zero, we must reply an ICMP control message telling
1266 * that the packet's lifetime expired.
1267 *
1268 * Exception:
1269 * We may not generate an ICMP for an ICMP. icmp_send does the
1270 * enforcement of this so we can forget it here. It is however
1271 * sometimes VERY important.
1272 */
1273
1274 iph = skb->h.iph;
1275 iph->ttl--;
1276 if (iph->ttl <= 0)
1277 {
1278 /* Tell the sender its packet died... */
1279 icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, dev);
1280 return;
1281 }
1282
1283 /*
1284 * Re-compute the IP header checksum.
1285 * This is inefficient. We know what has happened to the header
1286 * and could thus adjust the checksum as Phil Karn does in KA9Q
1287 */
1288
1289 ip_send_check(iph);
1290
1291 /*
1292 * OK, the packet is still valid. Fetch its destination address,
1293 * and give it to the IP sender for further processing.
1294 */
1295
1296 rt = ip_rt_route(iph->daddr, NULL, NULL);
1297 if (rt == NULL)
1298 {
1299 /*
1300 * Tell the sender its packet cannot be delivered. Again
1301 * ICMP is screened later.
1302 */
1303 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_NET_UNREACH, dev);
1304 return;
1305 }
1306
1307
1308 /*
1309 * Gosh. Not only is the packet valid; we even know how to
1310 * forward it onto its final destination. Can we say this
1311 * is being plain lucky?
1312 * If the router told us that there is no GW, use the dest.
1313 * IP address itself- we seem to be connected directly...
1314 */
1315
1316 raddr = rt->rt_gateway;
1317
1318 if (raddr != 0)
1319 {
1320 /*
1321 * There is a gateway so find the correct route for it.
1322 * Gateways cannot in turn be gatewayed.
1323 */
1324 rt = ip_rt_route(raddr, NULL, NULL);
1325 if (rt == NULL)
1326 {
1327 /*
1328 * Tell the sender its packet cannot be delivered...
1329 */
1330 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, dev);
1331 return;
1332 }
1333 if (rt->rt_gateway != 0)
1334 raddr = rt->rt_gateway;
1335 }
1336 else
1337 raddr = iph->daddr;
1338
1339 /*
1340 * Having picked a route we can now send the frame out.
1341 */
1342
1343 dev2 = rt->rt_dev;
1344
1345 /*
1346 * In IP you never forward a frame on the interface that it arrived
1347 * upon. We should generate an ICMP HOST REDIRECT giving the route
1348 * we calculated.
1349 * For now just dropping the packet is an acceptable compromise.
1350 */
1351
1352 if (dev == dev2)
1353 return;
1354
1355 /*
1356 * We now allocate a new buffer, and copy the datagram into it.
1357 * If the indicated interface is up and running, kick it.
1358 */
1359
1360 if (dev2->flags & IFF_UP)
1361 {
1362
1363 /*
1364 * Current design decrees we copy the packet. For identical header
1365 * lengths we could avoid it. The new skb code will let us push
1366 * data so the problem goes away then.
1367 */
1368
1369 skb2 = alloc_skb(dev2->hard_header_len + skb->len, GFP_ATOMIC);
1370 /*
1371 * This is rare and since IP is tolerant of network failures
1372 * quite harmless.
1373 */
1374 if (skb2 == NULL)
1375 {
1376 printk("\nIP: No memory available for IP forward\n");
1377 return;
1378 }
1379 ptr = skb2->data;
1380 skb2->free = 1;
1381 skb2->len = skb->len + dev2->hard_header_len;
1382 skb2->h.raw = ptr;
1383
1384 /*
1385 * Copy the packet data into the new buffer.
1386 */
1387 memcpy(ptr + dev2->hard_header_len, skb->h.raw, skb->len);
1388
1389 /* Now build the MAC header. */
1390 (void) ip_send(skb2, raddr, skb->len, dev2, dev2->pa_addr);
1391
1392 ip_statistics.IpForwDatagrams++;
1393
1394 /*
1395 * See if it needs fragmenting. Note in ip_rcv we tagged
1396 * the fragment type. This must be right so that
1397 * the fragmenter does the right thing.
1398 */
1399
1400 if(skb2->len > dev2->mtu + dev2->hard_header_len)
1401 {
1402 ip_fragment(NULL,skb2,dev2, is_frag);
1403 kfree_skb(skb2,FREE_WRITE);
1404 }
1405 else
1406 {
1407 /*
1408 * Map service types to priority. We lie about
1409 * throughput being low priority, but its a good
1410 * choice to help improve general usage.
1411 */
1412 if(iph->tos & IPTOS_LOWDELAY)
1413 dev_queue_xmit(skb2, dev2, SOPRI_INTERACTIVE);
1414 else if(iph->tos & IPTOS_THROUGHPUT)
1415 dev_queue_xmit(skb2, dev2, SOPRI_BACKGROUND);
1416 else
1417 dev_queue_xmit(skb2, dev2, SOPRI_NORMAL);
1418 }
1419 }
1420 }
1421
1422
1423 #endif
1424
1425 /*
1426 * This function receives all incoming IP datagrams.
1427 */
1428
1429 int ip_rcv(struct sk_buff *skb, struct device *dev, struct packet_type *pt)
/* */
1430 {
1431 struct iphdr *iph = skb->h.iph;
1432 unsigned char hash;
1433 unsigned char flag = 0;
1434 unsigned char opts_p = 0; /* Set iff the packet has options. */
1435 struct inet_protocol *ipprot;
1436 static struct options opt; /* since we don't use these yet, and they
1437 take up stack space. */
1438 int brd=IS_MYADDR;
1439 int is_frag=0;
1440
1441
1442 ip_statistics.IpInReceives++;
1443
1444 /*
1445 * Tag the ip header of this packet so we can find it
1446 */
1447
1448 skb->ip_hdr = iph;
1449
1450 /*
1451 * Is the datagram acceptable?
1452 *
1453 * 1. Length at least the size of an ip header
1454 * 2. Version of 4
1455 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums]
1456 * (4. We ought to check for IP multicast addresses and undefined types.. does this matter ?)
1457 */
1458
1459 if (skb->len<sizeof(struct iphdr) || iph->ihl<5 || iph->version != 4 || ip_fast_csum((unsigned char *)iph, iph->ihl) !=0)
1460 {
1461 ip_statistics.IpInHdrErrors++;
1462 kfree_skb(skb, FREE_WRITE);
1463 return(0);
1464 }
1465
1466 /*
1467 * Our transport medium may have padded the buffer out. Now we know it
1468 * is IP we can trim to the true length of the frame.
1469 */
1470
1471 skb->len=ntohs(iph->tot_len);
1472
1473 /*
1474 * Next analyse the packet for options. Studies show under one packet in
1475 * a thousand have options....
1476 */
1477
1478 if (iph->ihl != 5)
1479 { /* Fast path for the typical optionless IP packet. */
1480 memset((char *) &opt, 0, sizeof(opt));
1481 if (do_options(iph, &opt) != 0)
1482 return 0;
1483 opts_p = 1;
1484 }
1485
1486 /*
1487 * Remember if the frame is fragmented.
1488 */
1489
1490 if (iph->frag_off & 0x0020)
1491 is_frag|=1;
1492
1493 /*
1494 * Last fragment ?
1495 */
1496
1497 if (ntohs(iph->frag_off) & 0x1fff)
1498 is_frag|=2;
1499
1500 /*
1501 * Do any IP forwarding required. chk_addr() is expensive -- avoid it someday.
1502 *
1503 * This is inefficient. While finding out if it is for us we could also compute
1504 * the routing table entry. This is where the great unified cache theory comes
1505 * in as and when someone implements it
1506 *
1507 * For most hosts over 99% of packets match the first conditional
1508 * and don't go via ip_chk_addr. Note: brd is set to IS_MYADDR at
1509 * function entry.
1510 */
1511
1512 if ( iph->daddr != skb->dev->pa_addr && (brd = ip_chk_addr(iph->daddr)) == 0)
1513 {
1514 /*
1515 * Don't forward multicast or broadcast frames.
1516 */
1517
1518 if(skb->pkt_type!=PACKET_HOST)
1519 {
1520 kfree_skb(skb,FREE_WRITE);
1521 return 0;
1522 }
1523
1524 /*
1525 * The packet is for another target. Forward the frame
1526 */
1527
1528 #ifdef CONFIG_IP_FORWARD
1529 ip_forward(skb, dev, is_frag);
1530 #else
1531 /* printk("Machine %lx tried to use us as a forwarder to %lx but we have forwarding disabled!\n",
1532 iph->saddr,iph->daddr);*/
1533 ip_statistics.IpInAddrErrors++;
1534 #endif
1535 /*
1536 * The forwarder is inefficient and copies the packet. We
1537 * free the original now.
1538 */
1539
1540 kfree_skb(skb, FREE_WRITE);
1541 return(0);
1542 }
1543
1544 /*
1545 * Reassemble IP fragments.
1546 */
1547
1548 if(is_frag)
1549 {
1550 /* Defragment. Obtain the complete packet if there is one */
1551 skb=ip_defrag(iph,skb,dev);
1552 if(skb==NULL)
1553 return 0;
1554 iph=skb->h.iph;
1555 }
1556
1557 /*
1558 * Point into the IP datagram, just past the header.
1559 */
1560
1561 skb->ip_hdr = iph;
1562 skb->h.raw += iph->ihl*4;
1563
1564 /*
1565 * skb->h.raw now points at the protocol beyond the IP header.
1566 */
1567
1568 hash = iph->protocol & (MAX_INET_PROTOS -1);
1569 for (ipprot = (struct inet_protocol *)inet_protos[hash];ipprot != NULL;ipprot=(struct inet_protocol *)ipprot->next)
1570 {
1571 struct sk_buff *skb2;
1572
1573 if (ipprot->protocol != iph->protocol)
1574 continue;
1575 /*
1576 * See if we need to make a copy of it. This will
1577 * only be set if more than one protocol wants it.
1578 * and then not for the last one.
1579 *
1580 * This is an artifact of poor upper protocol design.
1581 * Because the upper protocols damage the actual packet
1582 * we must do copying. In actual fact it's even worse
1583 * than this as TCP may hold on to the buffer.
1584 */
1585 if (ipprot->copy)
1586 {
1587 skb2 = skb_clone(skb, GFP_ATOMIC);
1588 if(skb2==NULL)
1589 continue;
1590 }
1591 else
1592 {
1593 skb2 = skb;
1594 }
1595 flag = 1;
1596
1597 /*
1598 * Pass on the datagram to each protocol that wants it,
1599 * based on the datagram protocol. We should really
1600 * check the protocol handler's return values here...
1601 */
1602 ipprot->handler(skb2, dev, opts_p ? &opt : 0, iph->daddr,
1603 (ntohs(iph->tot_len) - (iph->ihl * 4)),
1604 iph->saddr, 0, ipprot);
1605
1606 }
1607
1608 /*
1609 * All protocols checked.
1610 * If this packet was a broadcast, we may *not* reply to it, since that
1611 * causes (proven, grin) ARP storms and a leakage of memory (i.e. all
1612 * ICMP reply messages get queued up for transmission...)
1613 */
1614
1615 if (!flag)
1616 {
1617 if (brd != IS_BROADCAST)
1618 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PROT_UNREACH, dev);
1619 kfree_skb(skb, FREE_WRITE);
1620 }
1621
1622 return(0);
1623 }
1624
1625
1626 /*
1627 * Queues a packet to be sent, and starts the transmitter
1628 * if necessary. if free = 1 then we free the block after
1629 * transmit, otherwise we don't. If free==2 we not only
1630 * free the block but also don't assign a new ip seq number.
1631 * This routine also needs to put in the total length,
1632 * and compute the checksum
1633 */
1634
1635 void ip_queue_xmit(struct sock *sk, struct device *dev,
/* */
1636 struct sk_buff *skb, int free)
1637 {
1638 struct iphdr *iph;
1639 unsigned char *ptr;
1640
1641 /* Sanity check */
1642 if (dev == NULL)
1643 {
1644 printk("IP: ip_queue_xmit dev = NULL\n");
1645 return;
1646 }
1647
1648 IS_SKB(skb);
1649
1650 /*
1651 * Do some book-keeping in the packet for later
1652 */
1653
1654
1655 skb->dev = dev;
1656 skb->when = jiffies;
1657
1658 /*
1659 * Find the IP header and set the length. This is bad
1660 * but once we get the skb data handling code in the
1661 * hardware will push its header sensibly and we will
1662 * set skb->ip_hdr to avoid this mess and the fixed
1663 * header length problem
1664 */
1665
1666 ptr = skb->data;
1667 ptr += dev->hard_header_len;
1668 iph = (struct iphdr *)ptr;
1669 skb->ip_hdr = iph;
1670 iph->tot_len = ntohs(skb->len-dev->hard_header_len);
1671
1672 /*
1673 * No reassigning numbers to fragments...
1674 */
1675
1676 if(free!=2)
1677 iph->id = htons(ip_id_count++);
1678 else
1679 free=1;
1680
1681 /* All buffers without an owner socket get freed */
1682 if (sk == NULL)
1683 free = 1;
1684
1685 skb->free = free;
1686
1687 /*
1688 * Do we need to fragment. Again this is inefficient.
1689 * We need to somehow lock the original buffer and use
1690 * bits of it.
1691 */
1692
1693 if(skb->len > dev->mtu + dev->hard_header_len)
1694 {
1695 ip_fragment(sk,skb,dev,0);
1696 IS_SKB(skb);
1697 kfree_skb(skb,FREE_WRITE);
1698 return;
1699 }
1700
1701 /*
1702 * Add an IP checksum
1703 */
1704
1705 ip_send_check(iph);
1706
1707 /*
1708 * Print the frame when debugging
1709 */
1710
1711 /*
1712 * More debugging. You cannot queue a packet already on a list
1713 * Spot this and moan loudly.
1714 */
1715 if (skb->next != NULL)
1716 {
1717 printk("ip_queue_xmit: next != NULL\n");
1718 skb_unlink(skb);
1719 }
1720
1721 /*
1722 * If a sender wishes the packet to remain unfreed
1723 * we add it to his send queue. This arguably belongs
1724 * in the TCP level since nobody else uses it. BUT
1725 * remember IPng might change all the rules.
1726 */
1727
1728 if (!free)
1729 {
1730 unsigned long flags;
1731 /* The socket now has more outstanding blocks */
1732
1733 sk->packets_out++;
1734
1735 /* Protect the list for a moment */
1736 save_flags(flags);
1737 cli();
1738
1739 if (skb->link3 != NULL)
1740 {
1741 printk("ip.c: link3 != NULL\n");
1742 skb->link3 = NULL;
1743 }
1744 if (sk->send_head == NULL)
1745 {
1746 sk->send_tail = skb;
1747 sk->send_head = skb;
1748 }
1749 else
1750 {
1751 sk->send_tail->link3 = skb;
1752 sk->send_tail = skb;
1753 }
1754 /* skb->link3 is NULL */
1755
1756 /* Interrupt restore */
1757 restore_flags(flags);
1758 /* Set the IP write timeout to the round trip time for the packet.
1759 If an acknowledge has not arrived by then we may wish to act */
1760 reset_timer(sk, TIME_WRITE, sk->rto);
1761 }
1762 else
1763 /* Remember who owns the buffer */
1764 skb->sk = sk;
1765
1766 /*
1767 * If the indicated interface is up and running, send the packet.
1768 */
1769 ip_statistics.IpOutRequests++;
1770
1771 if (dev->flags & IFF_UP)
1772 {
1773 /*
1774 * If we have an owner use its priority setting,
1775 * otherwise use NORMAL
1776 */
1777
1778 if (sk != NULL)
1779 {
1780 dev_queue_xmit(skb, dev, sk->priority);
1781 }
1782 else
1783 {
1784 dev_queue_xmit(skb, dev, SOPRI_NORMAL);
1785 }
1786 }
1787 else
1788 {
1789 ip_statistics.IpOutDiscards++;
1790 if (free)
1791 kfree_skb(skb, FREE_WRITE);
1792 }
1793 }
1794
1795
1796 /*
1797 * A socket has timed out on its send queue and wants to do a
1798 * little retransmitting. Currently this means TCP.
1799 */
1800
1801 void ip_do_retransmit(struct sock *sk, int all)
/* */
1802 {
1803 struct sk_buff * skb;
1804 struct proto *prot;
1805 struct device *dev;
1806 int retransmits;
1807
1808 prot = sk->prot;
1809 skb = sk->send_head;
1810 retransmits = sk->retransmits;
1811
1812 while (skb != NULL)
1813 {
1814 dev = skb->dev;
1815 IS_SKB(skb);
1816 skb->when = jiffies;
1817
1818 /*
1819 * In general it's OK just to use the old packet. However we
1820 * need to use the current ack and window fields. Urg and
1821 * urg_ptr could possibly stand to be updated as well, but we
1822 * don't keep the necessary data. That shouldn't be a problem,
1823 * if the other end is doing the right thing. Since we're
1824 * changing the packet, we have to issue a new IP identifier.
1825 */
1826
1827 /* this check may be unnecessary - retransmit only for TCP */
1828 if (sk->protocol == IPPROTO_TCP) {
1829 struct tcphdr *th;
1830 struct iphdr *iph;
1831 int size;
1832
1833 iph = (struct iphdr *)(skb->data + dev->hard_header_len);
1834 th = (struct tcphdr *)(((char *)iph) + (iph->ihl << 2));
1835 size = skb->len - (((unsigned char *) th) - skb->data);
1836
1837 iph->id = htons(ip_id_count++);
1838 ip_send_check(iph);
1839
1840 th->ack_seq = ntohl(sk->acked_seq);
1841 th->window = ntohs(tcp_select_window(sk));
1842 tcp_send_check(th, sk->saddr, sk->daddr, size, sk);
1843 }
1844
1845 /*
1846 * If the interface is (still) up and running, kick it.
1847 */
1848
1849 if (dev->flags & IFF_UP)
1850 {
1851 /*
1852 * If the packet is still being sent by the device/protocol
1853 * below then don't retransmit. This is both needed, and good -
1854 * especially with connected mode AX.25 where it stops resends
1855 * occuring of an as yet unsent anyway frame!
1856 * We still add up the counts as the round trip time wants
1857 * adjusting.
1858 */
1859 if (sk && !skb_device_locked(skb))
1860 {
1861 /* Remove it from any existing driver queue first! */
1862 skb_unlink(skb);
1863 /* Now queue it */
1864 ip_statistics.IpOutRequests++;
1865 dev_queue_xmit(skb, dev, sk->priority);
1866 }
1867 }
1868
1869 /*
1870 * Count retransmissions
1871 */
1872 retransmits++;
1873 sk->prot->retransmits ++;
1874
1875 /*
1876 * Only one retransmit requested.
1877 */
1878 if (!all)
1879 break;
1880
1881 /*
1882 * This should cut it off before we send too many packets.
1883 */
1884 if (sk->retransmits > sk->cong_window)
1885 break;
1886 skb = skb->link3;
1887 }
1888 }
1889
1890 /*
1891 * This is the normal code called for timeouts. It does the retransmission
1892 * and then does backoff. ip_do_retransmit is separated out because
1893 * tcp_ack needs to send stuff from the retransmit queue without
1894 * initiating a backoff.
1895 */
1896
1897 void ip_retransmit(struct sock *sk, int all)
/* */
1898 {
1899 ip_do_retransmit(sk, all);
1900
1901 /*
1902 * Increase the timeout each time we retransmit. Note that
1903 * we do not increase the rtt estimate. rto is initialized
1904 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
1905 * that doubling rto each time is the least we can get away with.
1906 * In KA9Q, Karn uses this for the first few times, and then
1907 * goes to quadratic. netBSD doubles, but only goes up to *64,
1908 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is
1909 * defined in the protocol as the maximum possible RTT. I guess
1910 * we'll have to use something other than TCP to talk to the
1911 * University of Mars.
1912 */
1913
1914 sk->retransmits++;
1915 sk->backoff++;
1916 sk->rto = min(sk->rto << 1, 120*HZ);
1917 reset_timer(sk, TIME_WRITE, sk->rto);
1918 }
1919
1920 /*
1921 * Socket option code for IP. This is the end of the line after any TCP,UDP etc options on
1922 * an IP socket.
1923 *
1924 * We implement IP_TOS (type of service), IP_TTL (time to live).
1925 *
1926 * Next release we will sort out IP_OPTIONS since for some people are kind of important.
1927 */
1928
1929 int ip_setsockopt(struct sock *sk, int level, int optname, char *optval, int optlen)
/* */
1930 {
1931 int val,err;
1932
1933 if (optval == NULL)
1934 return(-EINVAL);
1935
1936 err=verify_area(VERIFY_READ, optval, sizeof(int));
1937 if(err)
1938 return err;
1939
1940 val = get_fs_long((unsigned long *)optval);
1941
1942 if(level!=SOL_IP)
1943 return -EOPNOTSUPP;
1944
1945 switch(optname)
1946 {
1947 case IP_TOS:
1948 if(val<0||val>255)
1949 return -EINVAL;
1950 sk->ip_tos=val;
1951 if(val==IPTOS_LOWDELAY)
1952 sk->priority=SOPRI_INTERACTIVE;
1953 if(val==IPTOS_THROUGHPUT)
1954 sk->priority=SOPRI_BACKGROUND;
1955 return 0;
1956 case IP_TTL:
1957 if(val<1||val>255)
1958 return -EINVAL;
1959 sk->ip_ttl=val;
1960 return 0;
1961 /* IP_OPTIONS and friends go here eventually */
1962 default:
1963 return(-ENOPROTOOPT);
1964 }
1965 }
1966
1967 /*
1968 * Get the options. Note for future reference. The GET of IP options gets the
1969 * _received_ ones. The set sets the _sent_ ones.
1970 */
1971
1972 int ip_getsockopt(struct sock *sk, int level, int optname, char *optval, int *optlen)
/* */
1973 {
1974 int val,err;
1975
1976 if(level!=SOL_IP)
1977 return -EOPNOTSUPP;
1978
1979 switch(optname)
1980 {
1981 case IP_TOS:
1982 val=sk->ip_tos;
1983 break;
1984 case IP_TTL:
1985 val=sk->ip_ttl;
1986 break;
1987 default:
1988 return(-ENOPROTOOPT);
1989 }
1990 err=verify_area(VERIFY_WRITE, optlen, sizeof(int));
1991 if(err)
1992 return err;
1993 put_fs_long(sizeof(int),(unsigned long *) optlen);
1994
1995 err=verify_area(VERIFY_WRITE, optval, sizeof(int));
1996 if(err)
1997 return err;
1998 put_fs_long(val,(unsigned long *)optval);
1999
2000 return(0);
2001 }
2002
2003 /*
2004 * IP protocol layer initialiser
2005 */
2006
2007 static struct packet_type ip_packet_type =
2008 {
2009 0, /* MUTTER ntohs(ETH_P_IP),*/
2010 0, /* copy */
2011 ip_rcv,
2012 NULL,
2013 NULL,
2014 };
2015
2016
2017 /*
2018 * IP registers the packet type and then calls the subprotocol initialisers
2019 */
2020
2021 void ip_init(void)
/* ![[last]](../icons/n_last.png)
*/
2022 {
2023 ip_packet_type.type=htons(ETH_P_IP);
2024 dev_add_pack(&ip_packet_type);
2025 /* ip_raw_init();
2026 ip_packet_init();
2027 ip_tcp_init();
2028 ip_udp_init();*/
2029 }
![[bottom]](../icons/n_bottom.png){kind=icon}
*/