xref: /openbmc/linux/net/6lowpan/iphc.c (revision 976fa9a3)
1 /*
2  * Copyright 2011, Siemens AG
3  * written by Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
4  */
5 
6 /* Based on patches from Jon Smirl <jonsmirl@gmail.com>
7  * Copyright (c) 2011 Jon Smirl <jonsmirl@gmail.com>
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License version 2
11  * as published by the Free Software Foundation.
12  *
13  * This program is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16  * GNU General Public License for more details.
17  *
18  */
19 
20 /* Jon's code is based on 6lowpan implementation for Contiki which is:
21  * Copyright (c) 2008, Swedish Institute of Computer Science.
22  * All rights reserved.
23  *
24  * Redistribution and use in source and binary forms, with or without
25  * modification, are permitted provided that the following conditions
26  * are met:
27  * 1. Redistributions of source code must retain the above copyright
28  *    notice, this list of conditions and the following disclaimer.
29  * 2. Redistributions in binary form must reproduce the above copyright
30  *    notice, this list of conditions and the following disclaimer in the
31  *    documentation and/or other materials provided with the distribution.
32  * 3. Neither the name of the Institute nor the names of its contributors
33  *    may be used to endorse or promote products derived from this software
34  *    without specific prior written permission.
35  *
36  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
37  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
38  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
39  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
40  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
41  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
42  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
43  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
44  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
45  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
46  * SUCH DAMAGE.
47  */
48 
49 #include <linux/bitops.h>
50 #include <linux/if_arp.h>
51 #include <linux/module.h>
52 #include <linux/netdevice.h>
53 #include <net/6lowpan.h>
54 #include <net/ipv6.h>
55 #include <net/af_ieee802154.h>
56 
57 #include "nhc.h"
58 
59 /* Uncompress address function for source and
60  * destination address(non-multicast).
61  *
62  * address_mode is sam value or dam value.
63  */
64 static int uncompress_addr(struct sk_buff *skb,
65 			   struct in6_addr *ipaddr, const u8 address_mode,
66 			   const u8 *lladdr, const u8 addr_type,
67 			   const u8 addr_len)
68 {
69 	bool fail;
70 
71 	switch (address_mode) {
72 	case LOWPAN_IPHC_ADDR_00:
73 		/* for global link addresses */
74 		fail = lowpan_fetch_skb(skb, ipaddr->s6_addr, 16);
75 		break;
76 	case LOWPAN_IPHC_ADDR_01:
77 		/* fe:80::XXXX:XXXX:XXXX:XXXX */
78 		ipaddr->s6_addr[0] = 0xFE;
79 		ipaddr->s6_addr[1] = 0x80;
80 		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[8], 8);
81 		break;
82 	case LOWPAN_IPHC_ADDR_02:
83 		/* fe:80::ff:fe00:XXXX */
84 		ipaddr->s6_addr[0] = 0xFE;
85 		ipaddr->s6_addr[1] = 0x80;
86 		ipaddr->s6_addr[11] = 0xFF;
87 		ipaddr->s6_addr[12] = 0xFE;
88 		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[14], 2);
89 		break;
90 	case LOWPAN_IPHC_ADDR_03:
91 		fail = false;
92 		switch (addr_type) {
93 		case IEEE802154_ADDR_LONG:
94 			/* fe:80::XXXX:XXXX:XXXX:XXXX
95 			 *        \_________________/
96 			 *              hwaddr
97 			 */
98 			ipaddr->s6_addr[0] = 0xFE;
99 			ipaddr->s6_addr[1] = 0x80;
100 			memcpy(&ipaddr->s6_addr[8], lladdr, addr_len);
101 			/* second bit-flip (Universe/Local)
102 			 * is done according RFC2464
103 			 */
104 			ipaddr->s6_addr[8] ^= 0x02;
105 			break;
106 		case IEEE802154_ADDR_SHORT:
107 			/* fe:80::ff:fe00:XXXX
108 			 *		  \__/
109 			 *	       short_addr
110 			 *
111 			 * Universe/Local bit is zero.
112 			 */
113 			ipaddr->s6_addr[0] = 0xFE;
114 			ipaddr->s6_addr[1] = 0x80;
115 			ipaddr->s6_addr[11] = 0xFF;
116 			ipaddr->s6_addr[12] = 0xFE;
117 			ipaddr->s6_addr16[7] = htons(*((u16 *)lladdr));
118 			break;
119 		default:
120 			pr_debug("Invalid addr_type set\n");
121 			return -EINVAL;
122 		}
123 		break;
124 	default:
125 		pr_debug("Invalid address mode value: 0x%x\n", address_mode);
126 		return -EINVAL;
127 	}
128 
129 	if (fail) {
130 		pr_debug("Failed to fetch skb data\n");
131 		return -EIO;
132 	}
133 
134 	raw_dump_inline(NULL, "Reconstructed ipv6 addr is",
135 			ipaddr->s6_addr, 16);
136 
137 	return 0;
138 }
139 
140 /* Uncompress address function for source context
141  * based address(non-multicast).
142  */
143 static int uncompress_context_based_src_addr(struct sk_buff *skb,
144 					     struct in6_addr *ipaddr,
145 					     const u8 sam)
146 {
147 	switch (sam) {
148 	case LOWPAN_IPHC_ADDR_00:
149 		/* unspec address ::
150 		 * Do nothing, address is already ::
151 		 */
152 		break;
153 	case LOWPAN_IPHC_ADDR_01:
154 		/* TODO */
155 	case LOWPAN_IPHC_ADDR_02:
156 		/* TODO */
157 	case LOWPAN_IPHC_ADDR_03:
158 		/* TODO */
159 		netdev_warn(skb->dev, "SAM value 0x%x not supported\n", sam);
160 		return -EINVAL;
161 	default:
162 		pr_debug("Invalid sam value: 0x%x\n", sam);
163 		return -EINVAL;
164 	}
165 
166 	raw_dump_inline(NULL,
167 			"Reconstructed context based ipv6 src addr is",
168 			ipaddr->s6_addr, 16);
169 
170 	return 0;
171 }
172 
173 /* Uncompress function for multicast destination address,
174  * when M bit is set.
175  */
176 static int lowpan_uncompress_multicast_daddr(struct sk_buff *skb,
177 					     struct in6_addr *ipaddr,
178 					     const u8 dam)
179 {
180 	bool fail;
181 
182 	switch (dam) {
183 	case LOWPAN_IPHC_DAM_00:
184 		/* 00:  128 bits.  The full address
185 		 * is carried in-line.
186 		 */
187 		fail = lowpan_fetch_skb(skb, ipaddr->s6_addr, 16);
188 		break;
189 	case LOWPAN_IPHC_DAM_01:
190 		/* 01:  48 bits.  The address takes
191 		 * the form ffXX::00XX:XXXX:XXXX.
192 		 */
193 		ipaddr->s6_addr[0] = 0xFF;
194 		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[1], 1);
195 		fail |= lowpan_fetch_skb(skb, &ipaddr->s6_addr[11], 5);
196 		break;
197 	case LOWPAN_IPHC_DAM_10:
198 		/* 10:  32 bits.  The address takes
199 		 * the form ffXX::00XX:XXXX.
200 		 */
201 		ipaddr->s6_addr[0] = 0xFF;
202 		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[1], 1);
203 		fail |= lowpan_fetch_skb(skb, &ipaddr->s6_addr[13], 3);
204 		break;
205 	case LOWPAN_IPHC_DAM_11:
206 		/* 11:  8 bits.  The address takes
207 		 * the form ff02::00XX.
208 		 */
209 		ipaddr->s6_addr[0] = 0xFF;
210 		ipaddr->s6_addr[1] = 0x02;
211 		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[15], 1);
212 		break;
213 	default:
214 		pr_debug("DAM value has a wrong value: 0x%x\n", dam);
215 		return -EINVAL;
216 	}
217 
218 	if (fail) {
219 		pr_debug("Failed to fetch skb data\n");
220 		return -EIO;
221 	}
222 
223 	raw_dump_inline(NULL, "Reconstructed ipv6 multicast addr is",
224 			ipaddr->s6_addr, 16);
225 
226 	return 0;
227 }
228 
229 /* TTL uncompression values */
230 static const u8 lowpan_ttl_values[] = { 0, 1, 64, 255 };
231 
232 int
233 lowpan_header_decompress(struct sk_buff *skb, struct net_device *dev,
234 			 const u8 *saddr, const u8 saddr_type,
235 			 const u8 saddr_len, const u8 *daddr,
236 			 const u8 daddr_type, const u8 daddr_len,
237 			 u8 iphc0, u8 iphc1)
238 {
239 	struct ipv6hdr hdr = {};
240 	u8 tmp, num_context = 0;
241 	int err;
242 
243 	raw_dump_table(__func__, "raw skb data dump uncompressed",
244 		       skb->data, skb->len);
245 
246 	/* another if the CID flag is set */
247 	if (iphc1 & LOWPAN_IPHC_CID) {
248 		pr_debug("CID flag is set, increase header with one\n");
249 		if (lowpan_fetch_skb(skb, &num_context, sizeof(num_context)))
250 			return -EINVAL;
251 	}
252 
253 	hdr.version = 6;
254 
255 	/* Traffic Class and Flow Label */
256 	switch ((iphc0 & LOWPAN_IPHC_TF) >> 3) {
257 	/* Traffic Class and FLow Label carried in-line
258 	 * ECN + DSCP + 4-bit Pad + Flow Label (4 bytes)
259 	 */
260 	case 0: /* 00b */
261 		if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
262 			return -EINVAL;
263 
264 		memcpy(&hdr.flow_lbl, &skb->data[0], 3);
265 		skb_pull(skb, 3);
266 		hdr.priority = ((tmp >> 2) & 0x0f);
267 		hdr.flow_lbl[0] = ((tmp >> 2) & 0x30) | (tmp << 6) |
268 					(hdr.flow_lbl[0] & 0x0f);
269 		break;
270 	/* Traffic class carried in-line
271 	 * ECN + DSCP (1 byte), Flow Label is elided
272 	 */
273 	case 2: /* 10b */
274 		if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
275 			return -EINVAL;
276 
277 		hdr.priority = ((tmp >> 2) & 0x0f);
278 		hdr.flow_lbl[0] = ((tmp << 6) & 0xC0) | ((tmp >> 2) & 0x30);
279 		break;
280 	/* Flow Label carried in-line
281 	 * ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided
282 	 */
283 	case 1: /* 01b */
284 		if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
285 			return -EINVAL;
286 
287 		hdr.flow_lbl[0] = (skb->data[0] & 0x0F) | ((tmp >> 2) & 0x30);
288 		memcpy(&hdr.flow_lbl[1], &skb->data[0], 2);
289 		skb_pull(skb, 2);
290 		break;
291 	/* Traffic Class and Flow Label are elided */
292 	case 3: /* 11b */
293 		break;
294 	default:
295 		break;
296 	}
297 
298 	/* Next Header */
299 	if ((iphc0 & LOWPAN_IPHC_NH_C) == 0) {
300 		/* Next header is carried inline */
301 		if (lowpan_fetch_skb(skb, &hdr.nexthdr, sizeof(hdr.nexthdr)))
302 			return -EINVAL;
303 
304 		pr_debug("NH flag is set, next header carried inline: %02x\n",
305 			 hdr.nexthdr);
306 	}
307 
308 	/* Hop Limit */
309 	if ((iphc0 & 0x03) != LOWPAN_IPHC_TTL_I) {
310 		hdr.hop_limit = lowpan_ttl_values[iphc0 & 0x03];
311 	} else {
312 		if (lowpan_fetch_skb(skb, &hdr.hop_limit,
313 				     sizeof(hdr.hop_limit)))
314 			return -EINVAL;
315 	}
316 
317 	/* Extract SAM to the tmp variable */
318 	tmp = ((iphc1 & LOWPAN_IPHC_SAM) >> LOWPAN_IPHC_SAM_BIT) & 0x03;
319 
320 	if (iphc1 & LOWPAN_IPHC_SAC) {
321 		/* Source address context based uncompression */
322 		pr_debug("SAC bit is set. Handle context based source address.\n");
323 		err = uncompress_context_based_src_addr(skb, &hdr.saddr, tmp);
324 	} else {
325 		/* Source address uncompression */
326 		pr_debug("source address stateless compression\n");
327 		err = uncompress_addr(skb, &hdr.saddr, tmp, saddr,
328 				      saddr_type, saddr_len);
329 	}
330 
331 	/* Check on error of previous branch */
332 	if (err)
333 		return -EINVAL;
334 
335 	/* Extract DAM to the tmp variable */
336 	tmp = ((iphc1 & LOWPAN_IPHC_DAM_11) >> LOWPAN_IPHC_DAM_BIT) & 0x03;
337 
338 	/* check for Multicast Compression */
339 	if (iphc1 & LOWPAN_IPHC_M) {
340 		if (iphc1 & LOWPAN_IPHC_DAC) {
341 			pr_debug("dest: context-based mcast compression\n");
342 			/* TODO: implement this */
343 		} else {
344 			err = lowpan_uncompress_multicast_daddr(skb, &hdr.daddr,
345 								tmp);
346 
347 			if (err)
348 				return -EINVAL;
349 		}
350 	} else {
351 		err = uncompress_addr(skb, &hdr.daddr, tmp, daddr,
352 				      daddr_type, daddr_len);
353 		pr_debug("dest: stateless compression mode %d dest %pI6c\n",
354 			 tmp, &hdr.daddr);
355 		if (err)
356 			return -EINVAL;
357 	}
358 
359 	/* Next header data uncompression */
360 	if (iphc0 & LOWPAN_IPHC_NH_C) {
361 		err = lowpan_nhc_do_uncompression(skb, dev, &hdr);
362 		if (err < 0)
363 			return err;
364 	} else {
365 		err = skb_cow(skb, sizeof(hdr));
366 		if (unlikely(err))
367 			return err;
368 	}
369 
370 	hdr.payload_len = htons(skb->len);
371 
372 	pr_debug("skb headroom size = %d, data length = %d\n",
373 		 skb_headroom(skb), skb->len);
374 
375 	pr_debug("IPv6 header dump:\n\tversion = %d\n\tlength  = %d\n\t"
376 		 "nexthdr = 0x%02x\n\thop_lim = %d\n\tdest    = %pI6c\n",
377 		hdr.version, ntohs(hdr.payload_len), hdr.nexthdr,
378 		hdr.hop_limit, &hdr.daddr);
379 
380 	skb_push(skb, sizeof(hdr));
381 	skb_reset_network_header(skb);
382 	skb_copy_to_linear_data(skb, &hdr, sizeof(hdr));
383 
384 	raw_dump_table(__func__, "raw header dump", (u8 *)&hdr, sizeof(hdr));
385 
386 	return 0;
387 }
388 EXPORT_SYMBOL_GPL(lowpan_header_decompress);
389 
390 static u8 lowpan_compress_addr_64(u8 **hc_ptr, u8 shift,
391 				  const struct in6_addr *ipaddr,
392 				  const unsigned char *lladdr)
393 {
394 	u8 val = 0;
395 
396 	if (is_addr_mac_addr_based(ipaddr, lladdr)) {
397 		val = 3; /* 0-bits */
398 		pr_debug("address compression 0 bits\n");
399 	} else if (lowpan_is_iid_16_bit_compressable(ipaddr)) {
400 		/* compress IID to 16 bits xxxx::XXXX */
401 		lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr16[7], 2);
402 		val = 2; /* 16-bits */
403 		raw_dump_inline(NULL, "Compressed ipv6 addr is (16 bits)",
404 				*hc_ptr - 2, 2);
405 	} else {
406 		/* do not compress IID => xxxx::IID */
407 		lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr16[4], 8);
408 		val = 1; /* 64-bits */
409 		raw_dump_inline(NULL, "Compressed ipv6 addr is (64 bits)",
410 				*hc_ptr - 8, 8);
411 	}
412 
413 	return rol8(val, shift);
414 }
415 
416 int lowpan_header_compress(struct sk_buff *skb, struct net_device *dev,
417 			   unsigned short type, const void *_daddr,
418 			   const void *_saddr, unsigned int len)
419 {
420 	u8 tmp, iphc0, iphc1, *hc_ptr;
421 	struct ipv6hdr *hdr;
422 	u8 head[100] = {};
423 	int ret, addr_type;
424 
425 	if (type != ETH_P_IPV6)
426 		return -EINVAL;
427 
428 	hdr = ipv6_hdr(skb);
429 	hc_ptr = head + 2;
430 
431 	pr_debug("IPv6 header dump:\n\tversion = %d\n\tlength  = %d\n"
432 		 "\tnexthdr = 0x%02x\n\thop_lim = %d\n\tdest    = %pI6c\n",
433 		 hdr->version, ntohs(hdr->payload_len), hdr->nexthdr,
434 		 hdr->hop_limit, &hdr->daddr);
435 
436 	raw_dump_table(__func__, "raw skb network header dump",
437 		       skb_network_header(skb), sizeof(struct ipv6hdr));
438 
439 	/* As we copy some bit-length fields, in the IPHC encoding bytes,
440 	 * we sometimes use |=
441 	 * If the field is 0, and the current bit value in memory is 1,
442 	 * this does not work. We therefore reset the IPHC encoding here
443 	 */
444 	iphc0 = LOWPAN_DISPATCH_IPHC;
445 	iphc1 = 0;
446 
447 	/* TODO: context lookup */
448 
449 	raw_dump_inline(__func__, "saddr",
450 			(unsigned char *)_saddr, IEEE802154_ADDR_LEN);
451 	raw_dump_inline(__func__, "daddr",
452 			(unsigned char *)_daddr, IEEE802154_ADDR_LEN);
453 
454 	raw_dump_table(__func__, "sending raw skb network uncompressed packet",
455 		       skb->data, skb->len);
456 
457 	/* Traffic class, flow label
458 	 * If flow label is 0, compress it. If traffic class is 0, compress it
459 	 * We have to process both in the same time as the offset of traffic
460 	 * class depends on the presence of version and flow label
461 	 */
462 
463 	/* hc format of TC is ECN | DSCP , original one is DSCP | ECN */
464 	tmp = (hdr->priority << 4) | (hdr->flow_lbl[0] >> 4);
465 	tmp = ((tmp & 0x03) << 6) | (tmp >> 2);
466 
467 	if (((hdr->flow_lbl[0] & 0x0F) == 0) &&
468 	    (hdr->flow_lbl[1] == 0) && (hdr->flow_lbl[2] == 0)) {
469 		/* flow label can be compressed */
470 		iphc0 |= LOWPAN_IPHC_FL_C;
471 		if ((hdr->priority == 0) &&
472 		    ((hdr->flow_lbl[0] & 0xF0) == 0)) {
473 			/* compress (elide) all */
474 			iphc0 |= LOWPAN_IPHC_TC_C;
475 		} else {
476 			/* compress only the flow label */
477 			*hc_ptr = tmp;
478 			hc_ptr += 1;
479 		}
480 	} else {
481 		/* Flow label cannot be compressed */
482 		if ((hdr->priority == 0) &&
483 		    ((hdr->flow_lbl[0] & 0xF0) == 0)) {
484 			/* compress only traffic class */
485 			iphc0 |= LOWPAN_IPHC_TC_C;
486 			*hc_ptr = (tmp & 0xc0) | (hdr->flow_lbl[0] & 0x0F);
487 			memcpy(hc_ptr + 1, &hdr->flow_lbl[1], 2);
488 			hc_ptr += 3;
489 		} else {
490 			/* compress nothing */
491 			memcpy(hc_ptr, hdr, 4);
492 			/* replace the top byte with new ECN | DSCP format */
493 			*hc_ptr = tmp;
494 			hc_ptr += 4;
495 		}
496 	}
497 
498 	/* NOTE: payload length is always compressed */
499 
500 	/* Check if we provide the nhc format for nexthdr and compression
501 	 * functionality. If not nexthdr is handled inline and not compressed.
502 	 */
503 	ret = lowpan_nhc_check_compression(skb, hdr, &hc_ptr, &iphc0);
504 	if (ret < 0)
505 		return ret;
506 
507 	/* Hop limit
508 	 * if 1:   compress, encoding is 01
509 	 * if 64:  compress, encoding is 10
510 	 * if 255: compress, encoding is 11
511 	 * else do not compress
512 	 */
513 	switch (hdr->hop_limit) {
514 	case 1:
515 		iphc0 |= LOWPAN_IPHC_TTL_1;
516 		break;
517 	case 64:
518 		iphc0 |= LOWPAN_IPHC_TTL_64;
519 		break;
520 	case 255:
521 		iphc0 |= LOWPAN_IPHC_TTL_255;
522 		break;
523 	default:
524 		lowpan_push_hc_data(&hc_ptr, &hdr->hop_limit,
525 				    sizeof(hdr->hop_limit));
526 	}
527 
528 	addr_type = ipv6_addr_type(&hdr->saddr);
529 	/* source address compression */
530 	if (addr_type == IPV6_ADDR_ANY) {
531 		pr_debug("source address is unspecified, setting SAC\n");
532 		iphc1 |= LOWPAN_IPHC_SAC;
533 	} else {
534 		if (addr_type & IPV6_ADDR_LINKLOCAL) {
535 			iphc1 |= lowpan_compress_addr_64(&hc_ptr,
536 							 LOWPAN_IPHC_SAM_BIT,
537 							 &hdr->saddr, _saddr);
538 			pr_debug("source address unicast link-local %pI6c iphc1 0x%02x\n",
539 				 &hdr->saddr, iphc1);
540 		} else {
541 			pr_debug("send the full source address\n");
542 			lowpan_push_hc_data(&hc_ptr, hdr->saddr.s6_addr, 16);
543 		}
544 	}
545 
546 	addr_type = ipv6_addr_type(&hdr->daddr);
547 	/* destination address compression */
548 	if (addr_type & IPV6_ADDR_MULTICAST) {
549 		pr_debug("destination address is multicast: ");
550 		iphc1 |= LOWPAN_IPHC_M;
551 		if (lowpan_is_mcast_addr_compressable8(&hdr->daddr)) {
552 			pr_debug("compressed to 1 octet\n");
553 			iphc1 |= LOWPAN_IPHC_DAM_11;
554 			/* use last byte */
555 			lowpan_push_hc_data(&hc_ptr,
556 					    &hdr->daddr.s6_addr[15], 1);
557 		} else if (lowpan_is_mcast_addr_compressable32(&hdr->daddr)) {
558 			pr_debug("compressed to 4 octets\n");
559 			iphc1 |= LOWPAN_IPHC_DAM_10;
560 			/* second byte + the last three */
561 			lowpan_push_hc_data(&hc_ptr,
562 					    &hdr->daddr.s6_addr[1], 1);
563 			lowpan_push_hc_data(&hc_ptr,
564 					    &hdr->daddr.s6_addr[13], 3);
565 		} else if (lowpan_is_mcast_addr_compressable48(&hdr->daddr)) {
566 			pr_debug("compressed to 6 octets\n");
567 			iphc1 |= LOWPAN_IPHC_DAM_01;
568 			/* second byte + the last five */
569 			lowpan_push_hc_data(&hc_ptr,
570 					    &hdr->daddr.s6_addr[1], 1);
571 			lowpan_push_hc_data(&hc_ptr,
572 					    &hdr->daddr.s6_addr[11], 5);
573 		} else {
574 			pr_debug("using full address\n");
575 			iphc1 |= LOWPAN_IPHC_DAM_00;
576 			lowpan_push_hc_data(&hc_ptr, hdr->daddr.s6_addr, 16);
577 		}
578 	} else {
579 		if (addr_type & IPV6_ADDR_LINKLOCAL) {
580 			/* TODO: context lookup */
581 			iphc1 |= lowpan_compress_addr_64(&hc_ptr,
582 				LOWPAN_IPHC_DAM_BIT, &hdr->daddr, _daddr);
583 			pr_debug("dest address unicast link-local %pI6c "
584 				 "iphc1 0x%02x\n", &hdr->daddr, iphc1);
585 		} else {
586 			pr_debug("dest address unicast %pI6c\n", &hdr->daddr);
587 			lowpan_push_hc_data(&hc_ptr, hdr->daddr.s6_addr, 16);
588 		}
589 	}
590 
591 	/* next header compression */
592 	if (iphc0 & LOWPAN_IPHC_NH_C) {
593 		ret = lowpan_nhc_do_compression(skb, hdr, &hc_ptr);
594 		if (ret < 0)
595 			return ret;
596 	}
597 
598 	head[0] = iphc0;
599 	head[1] = iphc1;
600 
601 	skb_pull(skb, sizeof(struct ipv6hdr));
602 	skb_reset_transport_header(skb);
603 	memcpy(skb_push(skb, hc_ptr - head), head, hc_ptr - head);
604 	skb_reset_network_header(skb);
605 
606 	pr_debug("header len %d skb %u\n", (int)(hc_ptr - head), skb->len);
607 
608 	raw_dump_table(__func__, "raw skb data dump compressed",
609 		       skb->data, skb->len);
610 	return 0;
611 }
612 EXPORT_SYMBOL_GPL(lowpan_header_compress);
613 
614 static int __init lowpan_module_init(void)
615 {
616 	request_module_nowait("nhc_dest");
617 	request_module_nowait("nhc_fragment");
618 	request_module_nowait("nhc_hop");
619 	request_module_nowait("nhc_ipv6");
620 	request_module_nowait("nhc_mobility");
621 	request_module_nowait("nhc_routing");
622 	request_module_nowait("nhc_udp");
623 
624 	return 0;
625 }
626 module_init(lowpan_module_init);
627 
628 MODULE_LICENSE("GPL");
629