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