net/6lowpan/iphc.c

   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/netdevice.h>
  52 #include <net/6lowpan.h>
  53 #include <net/ipv6.h>
  54 #include <net/af_ieee802154.h>
  55
  56 #include "nhc.h"
  57
  58 /* Uncompress address function for source and
  59  * destination address(non-multicast).
  60  *
  61  * address_mode is sam value or dam value.
  62  */
  63 static int uncompress_addr(struct sk_buff *skb,
  64                            struct in6_addr *ipaddr, const u8 address_mode,
  65                            const u8 *lladdr, const u8 addr_type,
  66                            const u8 addr_len)
  67 {
  68         bool fail;
  69
  70         switch (address_mode) {
  71         case LOWPAN_IPHC_ADDR_00:
  72                 /* for global link addresses */
  73                 fail = lowpan_fetch_skb(skb, ipaddr->s6_addr, 16);
  74                 break;
  75         case LOWPAN_IPHC_ADDR_01:
  76                 /* fe:80::XXXX:XXXX:XXXX:XXXX */
  77                 ipaddr->s6_addr[0] = 0xFE;
  78                 ipaddr->s6_addr[1] = 0x80;
  79                 fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[8], 8);
  80                 break;
  81         case LOWPAN_IPHC_ADDR_02:
  82                 /* fe:80::ff:fe00:XXXX */
  83                 ipaddr->s6_addr[0] = 0xFE;
  84                 ipaddr->s6_addr[1] = 0x80;
  85                 ipaddr->s6_addr[11] = 0xFF;
  86                 ipaddr->s6_addr[12] = 0xFE;
  87                 fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[14], 2);
  88                 break;
  89         case LOWPAN_IPHC_ADDR_03:
  90                 fail = false;
  91                 switch (addr_type) {
  92                 case IEEE802154_ADDR_LONG:
  93                         /* fe:80::XXXX:XXXX:XXXX:XXXX
  94                          *        \_________________/
  95                          *              hwaddr
  96                          */
  97                         ipaddr->s6_addr[0] = 0xFE;
  98                         ipaddr->s6_addr[1] = 0x80;
  99                         memcpy(&ipaddr->s6_addr[8], lladdr, addr_len);
 100                         /* second bit-flip (Universe/Local)
 101                          * is done according RFC2464
 102                          */
 103                         ipaddr->s6_addr[8] ^= 0x02;
 104                         break;
 105                 case IEEE802154_ADDR_SHORT:
 106                         /* fe:80::ff:fe00:XXXX
 107                          *                \__/
 108                          *             short_addr
 109                          *
 110                          * Universe/Local bit is zero.
 111                          */
 112                         ipaddr->s6_addr[0] = 0xFE;
 113                         ipaddr->s6_addr[1] = 0x80;
 114                         ipaddr->s6_addr[11] = 0xFF;
 115                         ipaddr->s6_addr[12] = 0xFE;
 116                         ipaddr->s6_addr16[7] = htons(*((u16 *)lladdr));
 117                         break;
 118                 default:
 119                         pr_debug("Invalid addr_type set\n");
 120                         return -EINVAL;
 121                 }
 122                 break;
 123         default:
 124                 pr_debug("Invalid address mode value: 0x%x\n", address_mode);
 125                 return -EINVAL;
 126         }
 127
 128         if (fail) {
 129                 pr_debug("Failed to fetch skb data\n");
 130                 return -EIO;
 131         }
 132
 133         raw_dump_inline(NULL, "Reconstructed ipv6 addr is",
 134                         ipaddr->s6_addr, 16);
 135
 136         return 0;
 137 }
 138
 139 /* Uncompress address function for source context
 140  * based address(non-multicast).
 141  */
 142 static int uncompress_context_based_src_addr(struct sk_buff *skb,
 143                                              struct in6_addr *ipaddr,
 144                                              const u8 sam)
 145 {
 146         switch (sam) {
 147         case LOWPAN_IPHC_ADDR_00:
 148                 /* unspec address ::
 149                  * Do nothing, address is already ::
 150                  */
 151                 break;
 152         case LOWPAN_IPHC_ADDR_01:
 153                 /* TODO */
 154         case LOWPAN_IPHC_ADDR_02:
 155                 /* TODO */
 156         case LOWPAN_IPHC_ADDR_03:
 157                 /* TODO */
 158                 netdev_warn(skb->dev, "SAM value 0x%x not supported\n", sam);
 159                 return -EINVAL;
 160         default:
 161                 pr_debug("Invalid sam value: 0x%x\n", sam);
 162                 return -EINVAL;
 163         }
 164
 165         raw_dump_inline(NULL,
 166                         "Reconstructed context based ipv6 src addr is",
 167                         ipaddr->s6_addr, 16);
 168
 169         return 0;
 170 }
 171
 172 /* Uncompress function for multicast destination address,
 173  * when M bit is set.
 174  */
 175 static int lowpan_uncompress_multicast_daddr(struct sk_buff *skb,
 176                                              struct in6_addr *ipaddr,
 177                                              const u8 dam)
 178 {
 179         bool fail;
 180
 181         switch (dam) {
 182         case LOWPAN_IPHC_DAM_00:
 183                 /* 00:  128 bits.  The full address
 184                  * is carried in-line.
 185                  */
 186                 fail = lowpan_fetch_skb(skb, ipaddr->s6_addr, 16);
 187                 break;
 188         case LOWPAN_IPHC_DAM_01:
 189                 /* 01:  48 bits.  The address takes
 190                  * the form ffXX::00XX:XXXX:XXXX.
 191                  */
 192                 ipaddr->s6_addr[0] = 0xFF;
 193                 fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[1], 1);
 194                 fail |= lowpan_fetch_skb(skb, &ipaddr->s6_addr[11], 5);
 195                 break;
 196         case LOWPAN_IPHC_DAM_10:
 197                 /* 10:  32 bits.  The address takes
 198                  * the form ffXX::00XX:XXXX.
 199                  */
 200                 ipaddr->s6_addr[0] = 0xFF;
 201                 fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[1], 1);
 202                 fail |= lowpan_fetch_skb(skb, &ipaddr->s6_addr[13], 3);
 203                 break;
 204         case LOWPAN_IPHC_DAM_11:
 205                 /* 11:  8 bits.  The address takes
 206                  * the form ff02::00XX.
 207                  */
 208                 ipaddr->s6_addr[0] = 0xFF;
 209                 ipaddr->s6_addr[1] = 0x02;
 210                 fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[15], 1);
 211                 break;
 212         default:
 213                 pr_debug("DAM value has a wrong value: 0x%x\n", dam);
 214                 return -EINVAL;
 215         }
 216
 217         if (fail) {
 218                 pr_debug("Failed to fetch skb data\n");
 219                 return -EIO;
 220         }
 221
 222         raw_dump_inline(NULL, "Reconstructed ipv6 multicast addr is",
 223                         ipaddr->s6_addr, 16);
 224
 225         return 0;
 226 }
 227
 228 /* TTL uncompression values */
 229 static const u8 lowpan_ttl_values[] = { 0, 1, 64, 255 };
 230
 231 int
 232 lowpan_header_decompress(struct sk_buff *skb, struct net_device *dev,
 233                          const u8 *saddr, const u8 saddr_type,
 234                          const u8 saddr_len, const u8 *daddr,
 235                          const u8 daddr_type, const u8 daddr_len,
 236                          u8 iphc0, u8 iphc1)
 237 {
 238         struct ipv6hdr hdr = {};
 239         u8 tmp, num_context = 0;
 240         int err;
 241
 242         raw_dump_table(__func__, "raw skb data dump uncompressed",
 243                        skb->data, skb->len);
 244
 245         /* another if the CID flag is set */
 246         if (iphc1 & LOWPAN_IPHC_CID) {
 247                 pr_debug("CID flag is set, increase header with one\n");
 248                 if (lowpan_fetch_skb(skb, &num_context, sizeof(num_context)))
 249                         return -EINVAL;
 250         }
 251
 252         hdr.version = 6;
 253
 254         /* Traffic Class and Flow Label */
 255         switch ((iphc0 & LOWPAN_IPHC_TF) >> 3) {
 256         /* Traffic Class and FLow Label carried in-line
 257          * ECN + DSCP + 4-bit Pad + Flow Label (4 bytes)
 258          */
 259         case 0: /* 00b */
 260                 if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
 261                         return -EINVAL;
 262
 263                 memcpy(&hdr.flow_lbl, &skb->data[0], 3);
 264                 skb_pull(skb, 3);
 265                 hdr.priority = ((tmp >> 2) & 0x0f);
 266                 hdr.flow_lbl[0] = ((tmp >> 2) & 0x30) | (tmp << 6) |
 267                                         (hdr.flow_lbl[0] & 0x0f);
 268                 break;
 269         /* Traffic class carried in-line
 270          * ECN + DSCP (1 byte), Flow Label is elided
 271          */
 272         case 2: /* 10b */
 273                 if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
 274                         return -EINVAL;
 275
 276                 hdr.priority = ((tmp >> 2) & 0x0f);
 277                 hdr.flow_lbl[0] = ((tmp << 6) & 0xC0) | ((tmp >> 2) & 0x30);
 278                 break;
 279         /* Flow Label carried in-line
 280          * ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided
 281          */
 282         case 1: /* 01b */
 283                 if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
 284                         return -EINVAL;
 285
 286                 hdr.flow_lbl[0] = (tmp & 0x0F) | ((tmp >> 2) & 0x30);
 287                 memcpy(&hdr.flow_lbl[1], &skb->data[0], 2);
 288                 skb_pull(skb, 2);
 289                 break;
 290         /* Traffic Class and Flow Label are elided */
 291         case 3: /* 11b */
 292                 break;
 293         default:
 294                 break;
 295         }
 296
 297         /* Next Header */
 298         if ((iphc0 & LOWPAN_IPHC_NH_C) == 0) {
 299                 /* Next header is carried inline */
 300                 if (lowpan_fetch_skb(skb, &hdr.nexthdr, sizeof(hdr.nexthdr)))
 301                         return -EINVAL;
 302
 303                 pr_debug("NH flag is set, next header carried inline: %02x\n",
 304                          hdr.nexthdr);
 305         }
 306
 307         /* Hop Limit */
 308         if ((iphc0 & 0x03) != LOWPAN_IPHC_TTL_I) {
 309                 hdr.hop_limit = lowpan_ttl_values[iphc0 & 0x03];
 310         } else {
 311                 if (lowpan_fetch_skb(skb, &hdr.hop_limit,
 312                                      sizeof(hdr.hop_limit)))
 313                         return -EINVAL;
 314         }
 315
 316         /* Extract SAM to the tmp variable */
 317         tmp = ((iphc1 & LOWPAN_IPHC_SAM) >> LOWPAN_IPHC_SAM_BIT) & 0x03;
 318
 319         if (iphc1 & LOWPAN_IPHC_SAC) {
 320                 /* Source address context based uncompression */
 321                 pr_debug("SAC bit is set. Handle context based source address.\n");
 322                 err = uncompress_context_based_src_addr(skb, &hdr.saddr, tmp);
 323         } else {
 324                 /* Source address uncompression */
 325                 pr_debug("source address stateless compression\n");
 326                 err = uncompress_addr(skb, &hdr.saddr, tmp, saddr,
 327                                       saddr_type, saddr_len);
 328         }
 329
 330         /* Check on error of previous branch */
 331         if (err)
 332                 return -EINVAL;
 333
 334         /* Extract DAM to the tmp variable */
 335         tmp = ((iphc1 & LOWPAN_IPHC_DAM_11) >> LOWPAN_IPHC_DAM_BIT) & 0x03;
 336
 337         /* check for Multicast Compression */
 338         if (iphc1 & LOWPAN_IPHC_M) {
 339                 if (iphc1 & LOWPAN_IPHC_DAC) {
 340                         pr_debug("dest: context-based mcast compression\n");
 341                         /* TODO: implement this */
 342                 } else {
 343                         err = lowpan_uncompress_multicast_daddr(skb, &hdr.daddr,
 344                                                                 tmp);
 345
 346                         if (err)
 347                                 return -EINVAL;
 348                 }
 349         } else {
 350                 err = uncompress_addr(skb, &hdr.daddr, tmp, daddr,
 351                                       daddr_type, daddr_len);
 352                 pr_debug("dest: stateless compression mode %d dest %pI6c\n",
 353                          tmp, &hdr.daddr);
 354                 if (err)
 355                         return -EINVAL;
 356         }
 357
 358         /* Next header data uncompression */
 359         if (iphc0 & LOWPAN_IPHC_NH_C) {
 360                 err = lowpan_nhc_do_uncompression(skb, dev, &hdr);
 361                 if (err < 0)
 362                         return err;
 363         } else {
 364                 err = skb_cow(skb, sizeof(hdr));
 365                 if (unlikely(err))
 366                         return err;
 367         }
 368
 369         hdr.payload_len = htons(skb->len);
 370
 371         pr_debug("skb headroom size = %d, data length = %d\n",
 372                  skb_headroom(skb), skb->len);
 373
 374         pr_debug("IPv6 header dump:\n\tversion = %d\n\tlength  = %d\n\t"
 375                  "nexthdr = 0x%02x\n\thop_lim = %d\n\tdest    = %pI6c\n",
 376                 hdr.version, ntohs(hdr.payload_len), hdr.nexthdr,
 377                 hdr.hop_limit, &hdr.daddr);
 378
 379         skb_push(skb, sizeof(hdr));
 380         skb_reset_network_header(skb);
 381         skb_copy_to_linear_data(skb, &hdr, sizeof(hdr));
 382
 383         raw_dump_table(__func__, "raw header dump", (u8 *)&hdr, sizeof(hdr));
 384
 385         return 0;
 386 }
 387 EXPORT_SYMBOL_GPL(lowpan_header_decompress);
 388
 389 static u8 lowpan_compress_addr_64(u8 **hc_ptr, u8 shift,
 390                                   const struct in6_addr *ipaddr,
 391                                   const unsigned char *lladdr)
 392 {
 393         u8 val = 0;
 394
 395         if (is_addr_mac_addr_based(ipaddr, lladdr)) {
 396                 val = 3; /* 0-bits */
 397                 pr_debug("address compression 0 bits\n");
 398         } else if (lowpan_is_iid_16_bit_compressable(ipaddr)) {
 399                 /* compress IID to 16 bits xxxx::XXXX */
 400                 lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr16[7], 2);
 401                 val = 2; /* 16-bits */
 402                 raw_dump_inline(NULL, "Compressed ipv6 addr is (16 bits)",
 403                                 *hc_ptr - 2, 2);
 404         } else {
 405                 /* do not compress IID => xxxx::IID */
 406                 lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr16[4], 8);
 407                 val = 1; /* 64-bits */
 408                 raw_dump_inline(NULL, "Compressed ipv6 addr is (64 bits)",
 409                                 *hc_ptr - 8, 8);
 410         }
 411
 412         return rol8(val, shift);
 413 }
 414
 415 int lowpan_header_compress(struct sk_buff *skb, struct net_device *dev,
 416                            unsigned short type, const void *_daddr,
 417                            const void *_saddr, unsigned int len)
 418 {
 419         u8 tmp, iphc0, iphc1, *hc_ptr;
 420         struct ipv6hdr *hdr;
 421         u8 head[100] = {};
 422         int ret, addr_type;
 423
 424         if (type != ETH_P_IPV6)
 425                 return -EINVAL;
 426
 427         hdr = ipv6_hdr(skb);
 428         hc_ptr = head + 2;
 429
 430         pr_debug("IPv6 header dump:\n\tversion = %d\n\tlength  = %d\n"
 431                  "\tnexthdr = 0x%02x\n\thop_lim = %d\n\tdest    = %pI6c\n",
 432                  hdr->version, ntohs(hdr->payload_len), hdr->nexthdr,
 433                  hdr->hop_limit, &hdr->daddr);
 434
 435         raw_dump_table(__func__, "raw skb network header dump",
 436                        skb_network_header(skb), sizeof(struct ipv6hdr));
 437
 438         /* As we copy some bit-length fields, in the IPHC encoding bytes,
 439          * we sometimes use |=
 440          * If the field is 0, and the current bit value in memory is 1,
 441          * this does not work. We therefore reset the IPHC encoding here
 442          */
 443         iphc0 = LOWPAN_DISPATCH_IPHC;
 444         iphc1 = 0;
 445
 446         /* TODO: context lookup */
 447
 448         raw_dump_inline(__func__, "saddr",
 449                         (unsigned char *)_saddr, IEEE802154_ADDR_LEN);
 450         raw_dump_inline(__func__, "daddr",
 451                         (unsigned char *)_daddr, IEEE802154_ADDR_LEN);
 452
 453         raw_dump_table(__func__, "sending raw skb network uncompressed packet",
 454                        skb->data, skb->len);
 455
 456         /* Traffic class, flow label
 457          * If flow label is 0, compress it. If traffic class is 0, compress it
 458          * We have to process both in the same time as the offset of traffic
 459          * class depends on the presence of version and flow label
 460          */
 461
 462         /* hc format of TC is ECN | DSCP , original one is DSCP | ECN */
 463         tmp = (hdr->priority << 4) | (hdr->flow_lbl[0] >> 4);
 464         tmp = ((tmp & 0x03) << 6) | (tmp >> 2);
 465
 466         if (((hdr->flow_lbl[0] & 0x0F) == 0) &&
 467             (hdr->flow_lbl[1] == 0) && (hdr->flow_lbl[2] == 0)) {
 468                 /* flow label can be compressed */
 469                 iphc0 |= LOWPAN_IPHC_FL_C;
 470                 if ((hdr->priority == 0) &&
 471                     ((hdr->flow_lbl[0] & 0xF0) == 0)) {
 472                         /* compress (elide) all */
 473                         iphc0 |= LOWPAN_IPHC_TC_C;
 474                 } else {
 475                         /* compress only the flow label */
 476                         *hc_ptr = tmp;
 477                         hc_ptr += 1;
 478                 }
 479         } else {
 480                 /* Flow label cannot be compressed */
 481                 if ((hdr->priority == 0) &&
 482                     ((hdr->flow_lbl[0] & 0xF0) == 0)) {
 483                         /* compress only traffic class */
 484                         iphc0 |= LOWPAN_IPHC_TC_C;
 485                         *hc_ptr = (tmp & 0xc0) | (hdr->flow_lbl[0] & 0x0F);
 486                         memcpy(hc_ptr + 1, &hdr->flow_lbl[1], 2);
 487                         hc_ptr += 3;
 488                 } else {
 489                         /* compress nothing */
 490                         memcpy(hc_ptr, hdr, 4);
 491                         /* replace the top byte with new ECN | DSCP format */
 492                         *hc_ptr = tmp;
 493                         hc_ptr += 4;
 494                 }
 495         }
 496
 497         /* NOTE: payload length is always compressed */
 498
 499         /* Check if we provide the nhc format for nexthdr and compression
 500          * functionality. If not nexthdr is handled inline and not compressed.
 501          */
 502         ret = lowpan_nhc_check_compression(skb, hdr, &hc_ptr, &iphc0);
 503         if (ret < 0)
 504                 return ret;
 505
 506         /* Hop limit
 507          * if 1:   compress, encoding is 01
 508          * if 64:  compress, encoding is 10
 509          * if 255: compress, encoding is 11
 510          * else do not compress
 511          */
 512         switch (hdr->hop_limit) {
 513         case 1:
 514                 iphc0 |= LOWPAN_IPHC_TTL_1;
 515                 break;
 516         case 64:
 517                 iphc0 |= LOWPAN_IPHC_TTL_64;
 518                 break;
 519         case 255:
 520                 iphc0 |= LOWPAN_IPHC_TTL_255;
 521                 break;
 522         default:
 523                 lowpan_push_hc_data(&hc_ptr, &hdr->hop_limit,
 524                                     sizeof(hdr->hop_limit));
 525         }
 526
 527         addr_type = ipv6_addr_type(&hdr->saddr);
 528         /* source address compression */
 529         if (addr_type == IPV6_ADDR_ANY) {
 530                 pr_debug("source address is unspecified, setting SAC\n");
 531                 iphc1 |= LOWPAN_IPHC_SAC;
 532         } else {
 533                 if (addr_type & IPV6_ADDR_LINKLOCAL) {
 534                         iphc1 |= lowpan_compress_addr_64(&hc_ptr,
 535                                                          LOWPAN_IPHC_SAM_BIT,
 536                                                          &hdr->saddr, _saddr);
 537                         pr_debug("source address unicast link-local %pI6c iphc1 0x%02x\n",
 538                                  &hdr->saddr, iphc1);
 539                 } else {
 540                         pr_debug("send the full source address\n");
 541                         lowpan_push_hc_data(&hc_ptr, hdr->saddr.s6_addr, 16);
 542                 }
 543         }
 544
 545         addr_type = ipv6_addr_type(&hdr->daddr);
 546         /* destination address compression */
 547         if (addr_type & IPV6_ADDR_MULTICAST) {
 548                 pr_debug("destination address is multicast: ");
 549                 iphc1 |= LOWPAN_IPHC_M;
 550                 if (lowpan_is_mcast_addr_compressable8(&hdr->daddr)) {
 551                         pr_debug("compressed to 1 octet\n");
 552                         iphc1 |= LOWPAN_IPHC_DAM_11;
 553                         /* use last byte */
 554                         lowpan_push_hc_data(&hc_ptr,
 555                                             &hdr->daddr.s6_addr[15], 1);
 556                 } else if (lowpan_is_mcast_addr_compressable32(&hdr->daddr)) {
 557                         pr_debug("compressed to 4 octets\n");
 558                         iphc1 |= LOWPAN_IPHC_DAM_10;
 559                         /* second byte + the last three */
 560                         lowpan_push_hc_data(&hc_ptr,
 561                                             &hdr->daddr.s6_addr[1], 1);
 562                         lowpan_push_hc_data(&hc_ptr,
 563                                             &hdr->daddr.s6_addr[13], 3);
 564                 } else if (lowpan_is_mcast_addr_compressable48(&hdr->daddr)) {
 565                         pr_debug("compressed to 6 octets\n");
 566                         iphc1 |= LOWPAN_IPHC_DAM_01;
 567                         /* second byte + the last five */
 568                         lowpan_push_hc_data(&hc_ptr,
 569                                             &hdr->daddr.s6_addr[1], 1);
 570                         lowpan_push_hc_data(&hc_ptr,
 571                                             &hdr->daddr.s6_addr[11], 5);
 572                 } else {
 573                         pr_debug("using full address\n");
 574                         iphc1 |= LOWPAN_IPHC_DAM_00;
 575                         lowpan_push_hc_data(&hc_ptr, hdr->daddr.s6_addr, 16);
 576                 }
 577         } else {
 578                 if (addr_type & IPV6_ADDR_LINKLOCAL) {
 579                         /* TODO: context lookup */
 580                         iphc1 |= lowpan_compress_addr_64(&hc_ptr,
 581                                 LOWPAN_IPHC_DAM_BIT, &hdr->daddr, _daddr);
 582                         pr_debug("dest address unicast link-local %pI6c "
 583                                  "iphc1 0x%02x\n", &hdr->daddr, iphc1);
 584                 } else {
 585                         pr_debug("dest address unicast %pI6c\n", &hdr->daddr);
 586                         lowpan_push_hc_data(&hc_ptr, hdr->daddr.s6_addr, 16);
 587                 }
 588         }
 589
 590         /* next header compression */
 591         if (iphc0 & LOWPAN_IPHC_NH_C) {
 592                 ret = lowpan_nhc_do_compression(skb, hdr, &hc_ptr);
 593                 if (ret < 0)
 594                         return ret;
 595         }
 596
 597         head[0] = iphc0;
 598         head[1] = iphc1;
 599
 600         skb_pull(skb, sizeof(struct ipv6hdr));
 601         skb_reset_transport_header(skb);
 602         memcpy(skb_push(skb, hc_ptr - head), head, hc_ptr - head);
 603         skb_reset_network_header(skb);
 604
 605         pr_debug("header len %d skb %u\n", (int)(hc_ptr - head), skb->len);
 606
 607         raw_dump_table(__func__, "raw skb data dump compressed",
 608                        skb->data, skb->len);
 609         return 0;
 610 }
 611 EXPORT_SYMBOL_GPL(lowpan_header_compress);