6lowpan: introduce new net/6lowpan directory

This patch moves generic code which is used by bluetooth and ieee802154
6lowpan to a new net/6lowpan directory. This directory contains generic
6LoWPAN code which is shared between bluetooth and ieee802154 MAC-Layer.

This is the IPHC - "IPv6 Header Compression" format at the moment. Which
is described by RFC 6282 [0]. The BLTE 6LoWPAN draft describes that the
IPHC is the same format like IEEE 802.15.4, see [1].

Futuremore we can put more code into this directory which is shared
between BLTE and IEEE 802.15.4 6LoWPAN like RFC 6775 or the routing
protocol RPL RFC 6550.

To avoid naming conflicts I renamed 6lowpan-y to ieee802154_6lowpan-y
in net/ieee802154/Makefile.

[0] http://tools.ietf.org/html/rfc6282
[1] http://tools.ietf.org/html/draft-ietf-6lowpan-btle-12#section-3.2
[2] http://tools.ietf.org/html/rfc6775
[3] http://tools.ietf.org/html/rfc6550

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

3 files changed, 810 insertions, 0 deletions

diff --git a/net/6lowpan/Kconfig b/net/6lowpan/Kconfig
new file mode 100644
index 000000000000..028a5c6d1f61
--- /dev/null
+++ b/net/6lowpan/Kconfig
@@ -0,0 +1,6 @@
+config 6LOWPAN
+        bool "6LoWPAN Support"
+        depends on IPV6
+        ---help---
+          This enables IPv6 over Low power Wireless Personal Area Network -
+          "6LoWPAN" which is supported by IEEE 802.15.4 or Bluetooth stacks.
diff --git a/net/6lowpan/Makefile b/net/6lowpan/Makefile
new file mode 100644
index 000000000000..415886bb456a
--- /dev/null
+++ b/net/6lowpan/Makefile
@@ -0,0 +1,3 @@
+obj-$(CONFIG_6LOWPAN) := 6lowpan.o
+
+6lowpan-y := iphc.o
diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c
new file mode 100644
index 000000000000..211b5686d719
--- /dev/null
+++ b/net/6lowpan/iphc.c
@@ -0,0 +1,801 @@
+/*
+ * Copyright 2011, Siemens AG
+ * written by Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
+ */
+
+/*
+ * Based on patches from Jon Smirl <jonsmirl@gmail.com>
+ * Copyright (c) 2011 Jon Smirl <jonsmirl@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/* Jon's code is based on 6lowpan implementation for Contiki which is:
+ * Copyright (c) 2008, Swedish Institute of Computer Science.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the Institute nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <linux/bitops.h>
+#include <linux/if_arp.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <net/6lowpan.h>
+#include <net/ipv6.h>
+#include <net/af_ieee802154.h>
+
+/*
+ * Uncompress address function for source and
+ * destination address(non-multicast).
+ *
+ * address_mode is sam value or dam value.
+ */
+static int uncompress_addr(struct sk_buff *skb,
+                                struct in6_addr *ipaddr, const u8 address_mode,
+                                const u8 *lladdr, const u8 addr_type,
+                                const u8 addr_len)
+{
+        bool fail;
+
+        switch (address_mode) {
+        case LOWPAN_IPHC_ADDR_00:
+                /* for global link addresses */
+                fail = lowpan_fetch_skb(skb, ipaddr->s6_addr, 16);
+                break;
+        case LOWPAN_IPHC_ADDR_01:
+                /* fe:80::XXXX:XXXX:XXXX:XXXX */
+                ipaddr->s6_addr[0] = 0xFE;
+                ipaddr->s6_addr[1] = 0x80;
+                fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[8], 8);
+                break;
+        case LOWPAN_IPHC_ADDR_02:
+                /* fe:80::ff:fe00:XXXX */
+                ipaddr->s6_addr[0] = 0xFE;
+                ipaddr->s6_addr[1] = 0x80;
+                ipaddr->s6_addr[11] = 0xFF;
+                ipaddr->s6_addr[12] = 0xFE;
+                fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[14], 2);
+                break;
+        case LOWPAN_IPHC_ADDR_03:
+                fail = false;
+                switch (addr_type) {
+                case IEEE802154_ADDR_LONG:
+                        /* fe:80::XXXX:XXXX:XXXX:XXXX
+                         *        \_________________/
+                         *              hwaddr
+                         */
+                        ipaddr->s6_addr[0] = 0xFE;
+                        ipaddr->s6_addr[1] = 0x80;
+                        memcpy(&ipaddr->s6_addr[8], lladdr, addr_len);
+                        /* second bit-flip (Universe/Local)
+                         * is done according RFC2464
+                         */
+                        ipaddr->s6_addr[8] ^= 0x02;
+                        break;
+                case IEEE802154_ADDR_SHORT:
+                        /* fe:80::ff:fe00:XXXX
+                         *                \__/
+                         *             short_addr
+                         *
+                         * Universe/Local bit is zero.
+                         */
+                        ipaddr->s6_addr[0] = 0xFE;
+                        ipaddr->s6_addr[1] = 0x80;
+                        ipaddr->s6_addr[11] = 0xFF;
+                        ipaddr->s6_addr[12] = 0xFE;
+                        ipaddr->s6_addr16[7] = htons(*((u16 *)lladdr));
+                        break;
+                default:
+                        pr_debug("Invalid addr_type set\n");
+                        return -EINVAL;
+                }
+                break;
+        default:
+                pr_debug("Invalid address mode value: 0x%x\n", address_mode);
+                return -EINVAL;
+        }
+
+        if (fail) {
+                pr_debug("Failed to fetch skb data\n");
+                return -EIO;
+        }
+
+        raw_dump_inline(NULL, "Reconstructed ipv6 addr is",
+                        ipaddr->s6_addr, 16);
+
+        return 0;
+}
+
+/*
+ * Uncompress address function for source context
+ * based address(non-multicast).
+ */
+static int uncompress_context_based_src_addr(struct sk_buff *skb,
+                                                struct in6_addr *ipaddr,
+                                                const u8 sam)
+{
+        switch (sam) {
+        case LOWPAN_IPHC_ADDR_00:
+                /* unspec address ::
+                 * Do nothing, address is already ::
+                 */
+                break;
+        case LOWPAN_IPHC_ADDR_01:
+                /* TODO */
+        case LOWPAN_IPHC_ADDR_02:
+                /* TODO */
+        case LOWPAN_IPHC_ADDR_03:
+                /* TODO */
+                netdev_warn(skb->dev, "SAM value 0x%x not supported\n", sam);
+                return -EINVAL;
+        default:
+                pr_debug("Invalid sam value: 0x%x\n", sam);
+                return -EINVAL;
+        }
+
+        raw_dump_inline(NULL,
+                        "Reconstructed context based ipv6 src addr is",
+                        ipaddr->s6_addr, 16);
+
+        return 0;
+}
+
+static int skb_deliver(struct sk_buff *skb, struct ipv6hdr *hdr,
+                struct net_device *dev, skb_delivery_cb deliver_skb)
+{
+        struct sk_buff *new;
+        int stat;
+
+        new = skb_copy_expand(skb, sizeof(struct ipv6hdr), skb_tailroom(skb),
+                                                                GFP_ATOMIC);
+        kfree_skb(skb);
+
+        if (!new)
+                return -ENOMEM;
+
+        skb_push(new, sizeof(struct ipv6hdr));
+        skb_reset_network_header(new);
+        skb_copy_to_linear_data(new, hdr, sizeof(struct ipv6hdr));
+
+        new->protocol = htons(ETH_P_IPV6);
+        new->pkt_type = PACKET_HOST;
+        new->dev = dev;
+
+        raw_dump_table(__func__, "raw skb data dump before receiving",
+                        new->data, new->len);
+
+        stat = deliver_skb(new, dev);
+
+        kfree_skb(new);
+
+        return stat;
+}
+
+/* Uncompress function for multicast destination address,
+ * when M bit is set.
+ */
+static int
+lowpan_uncompress_multicast_daddr(struct sk_buff *skb,
+                struct in6_addr *ipaddr,
+                const u8 dam)
+{
+        bool fail;
+
+        switch (dam) {
+        case LOWPAN_IPHC_DAM_00:
+                /* 00:  128 bits.  The full address
+                 * is carried in-line.
+                 */
+                fail = lowpan_fetch_skb(skb, ipaddr->s6_addr, 16);
+                break;
+        case LOWPAN_IPHC_DAM_01:
+                /* 01:  48 bits.  The address takes
+                 * the form ffXX::00XX:XXXX:XXXX.
+                 */
+                ipaddr->s6_addr[0] = 0xFF;
+                fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[1], 1);
+                fail |= lowpan_fetch_skb(skb, &ipaddr->s6_addr[11], 5);
+                break;
+        case LOWPAN_IPHC_DAM_10:
+                /* 10:  32 bits.  The address takes
+                 * the form ffXX::00XX:XXXX.
+                 */
+                ipaddr->s6_addr[0] = 0xFF;
+                fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[1], 1);
+                fail |= lowpan_fetch_skb(skb, &ipaddr->s6_addr[13], 3);
+                break;
+        case LOWPAN_IPHC_DAM_11:
+                /* 11:  8 bits.  The address takes
+                 * the form ff02::00XX.
+                 */
+                ipaddr->s6_addr[0] = 0xFF;
+                ipaddr->s6_addr[1] = 0x02;
+                fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[15], 1);
+                break;
+        default:
+                pr_debug("DAM value has a wrong value: 0x%x\n", dam);
+                return -EINVAL;
+        }
+
+        if (fail) {
+                pr_debug("Failed to fetch skb data\n");
+                return -EIO;
+        }
+
+        raw_dump_inline(NULL, "Reconstructed ipv6 multicast addr is",
+                                ipaddr->s6_addr, 16);
+
+        return 0;
+}
+
+static int
+uncompress_udp_header(struct sk_buff *skb, struct udphdr *uh)
+{
+        bool fail;
+        u8 tmp = 0, val = 0;
+
+        if (!uh)
+                goto err;
+
+        fail = lowpan_fetch_skb(skb, &tmp, 1);
+
+        if ((tmp & LOWPAN_NHC_UDP_MASK) == LOWPAN_NHC_UDP_ID) {
+                pr_debug("UDP header uncompression\n");
+                switch (tmp & LOWPAN_NHC_UDP_CS_P_11) {
+                case LOWPAN_NHC_UDP_CS_P_00:
+                        fail |= lowpan_fetch_skb(skb, &uh->source, 2);
+                        fail |= lowpan_fetch_skb(skb, &uh->dest, 2);
+                        break;
+                case LOWPAN_NHC_UDP_CS_P_01:
+                        fail |= lowpan_fetch_skb(skb, &uh->source, 2);
+                        fail |= lowpan_fetch_skb(skb, &val, 1);
+                        uh->dest = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
+                        break;
+                case LOWPAN_NHC_UDP_CS_P_10:
+                        fail |= lowpan_fetch_skb(skb, &val, 1);
+                        uh->source = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
+                        fail |= lowpan_fetch_skb(skb, &uh->dest, 2);
+                        break;
+                case LOWPAN_NHC_UDP_CS_P_11:
+                        fail |= lowpan_fetch_skb(skb, &val, 1);
+                        uh->source = htons(LOWPAN_NHC_UDP_4BIT_PORT +
+                                           (val >> 4));
+                        uh->dest = htons(LOWPAN_NHC_UDP_4BIT_PORT +
+                                         (val & 0x0f));
+                        break;
+                default:
+                        pr_debug("ERROR: unknown UDP format\n");
+                        goto err;
+                        break;
+                }
+
+                pr_debug("uncompressed UDP ports: src = %d, dst = %d\n",
+                         ntohs(uh->source), ntohs(uh->dest));
+
+                /* checksum */
+                if (tmp & LOWPAN_NHC_UDP_CS_C) {
+                        pr_debug_ratelimited("checksum elided currently not supported\n");
+                        goto err;
+                } else {
+                        fail |= lowpan_fetch_skb(skb, &uh->check, 2);
+                }
+
+                /*
+                 * UDP lenght needs to be infered from the lower layers
+                 * here, we obtain the hint from the remaining size of the
+                 * frame
+                 */
+                uh->len = htons(skb->len + sizeof(struct udphdr));
+                pr_debug("uncompressed UDP length: src = %d", ntohs(uh->len));
+        } else {
+                pr_debug("ERROR: unsupported NH format\n");
+                goto err;
+        }
+
+        if (fail)
+                goto err;
+
+        return 0;
+err:
+        return -EINVAL;
+}
+
+/* TTL uncompression values */
+static const u8 lowpan_ttl_values[] = { 0, 1, 64, 255 };
+
+int lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
+                const u8 *saddr, const u8 saddr_type, const u8 saddr_len,
+                const u8 *daddr, const u8 daddr_type, const u8 daddr_len,
+                u8 iphc0, u8 iphc1, skb_delivery_cb deliver_skb)
+{
+        struct ipv6hdr hdr = {};
+        u8 tmp, num_context = 0;
+        int err;
+
+        raw_dump_table(__func__, "raw skb data dump uncompressed",
+                                skb->data, skb->len);
+
+        /* another if the CID flag is set */
+        if (iphc1 & LOWPAN_IPHC_CID) {
+                pr_debug("CID flag is set, increase header with one\n");
+                if (lowpan_fetch_skb_u8(skb, &num_context))
+                        goto drop;
+        }
+
+        hdr.version = 6;
+
+        /* Traffic Class and Flow Label */
+        switch ((iphc0 & LOWPAN_IPHC_TF) >> 3) {
+        /*
+         * Traffic Class and FLow Label carried in-line
+         * ECN + DSCP + 4-bit Pad + Flow Label (4 bytes)
+         */
+        case 0: /* 00b */
+                if (lowpan_fetch_skb_u8(skb, &tmp))
+                        goto drop;
+
+                memcpy(&hdr.flow_lbl, &skb->data[0], 3);
+                skb_pull(skb, 3);
+                hdr.priority = ((tmp >> 2) & 0x0f);
+                hdr.flow_lbl[0] = ((tmp >> 2) & 0x30) | (tmp << 6) |
+                                        (hdr.flow_lbl[0] & 0x0f);
+                break;
+        /*
+         * Traffic class carried in-line
+         * ECN + DSCP (1 byte), Flow Label is elided
+         */
+        case 2: /* 10b */
+                if (lowpan_fetch_skb_u8(skb, &tmp))
+                        goto drop;
+
+                hdr.priority = ((tmp >> 2) & 0x0f);
+                hdr.flow_lbl[0] = ((tmp << 6) & 0xC0) | ((tmp >> 2) & 0x30);
+                break;
+        /*
+         * Flow Label carried in-line
+         * ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided
+         */
+        case 1: /* 01b */
+                if (lowpan_fetch_skb_u8(skb, &tmp))
+                        goto drop;
+
+                hdr.flow_lbl[0] = (skb->data[0] & 0x0F) | ((tmp >> 2) & 0x30);
+                memcpy(&hdr.flow_lbl[1], &skb->data[0], 2);
+                skb_pull(skb, 2);
+                break;
+        /* Traffic Class and Flow Label are elided */
+        case 3: /* 11b */
+                break;
+        default:
+                break;
+        }
+
+        /* Next Header */
+        if ((iphc0 & LOWPAN_IPHC_NH_C) == 0) {
+                /* Next header is carried inline */
+                if (lowpan_fetch_skb_u8(skb, &(hdr.nexthdr)))
+                        goto drop;
+
+                pr_debug("NH flag is set, next header carried inline: %02x\n",
+                         hdr.nexthdr);
+        }
+
+        /* Hop Limit */
+        if ((iphc0 & 0x03) != LOWPAN_IPHC_TTL_I)
+                hdr.hop_limit = lowpan_ttl_values[iphc0 & 0x03];
+        else {
+                if (lowpan_fetch_skb_u8(skb, &(hdr.hop_limit)))
+                        goto drop;
+        }
+
+        /* Extract SAM to the tmp variable */
+        tmp = ((iphc1 & LOWPAN_IPHC_SAM) >> LOWPAN_IPHC_SAM_BIT) & 0x03;
+
+        if (iphc1 & LOWPAN_IPHC_SAC) {
+                /* Source address context based uncompression */
+                pr_debug("SAC bit is set. Handle context based source address.\n");
+                err = uncompress_context_based_src_addr(
+                                skb, &hdr.saddr, tmp);
+        } else {
+                /* Source address uncompression */
+                pr_debug("source address stateless compression\n");
+                err = uncompress_addr(skb, &hdr.saddr, tmp, saddr,
+                                        saddr_type, saddr_len);
+        }
+
+        /* Check on error of previous branch */
+        if (err)
+                goto drop;
+
+        /* Extract DAM to the tmp variable */
+        tmp = ((iphc1 & LOWPAN_IPHC_DAM_11) >> LOWPAN_IPHC_DAM_BIT) & 0x03;
+
+        /* check for Multicast Compression */
+        if (iphc1 & LOWPAN_IPHC_M) {
+                if (iphc1 & LOWPAN_IPHC_DAC) {
+                        pr_debug("dest: context-based mcast compression\n");
+                        /* TODO: implement this */
+                } else {
+                        err = lowpan_uncompress_multicast_daddr(
+                                                skb, &hdr.daddr, tmp);
+                        if (err)
+                                goto drop;
+                }
+        } else {
+                err = uncompress_addr(skb, &hdr.daddr, tmp, daddr,
+                                        daddr_type, daddr_len);
+                pr_debug("dest: stateless compression mode %d dest %pI6c\n",
+                        tmp, &hdr.daddr);
+                if (err)
+                        goto drop;
+        }
+
+        /* UDP data uncompression */
+        if (iphc0 & LOWPAN_IPHC_NH_C) {
+                struct udphdr uh;
+                struct sk_buff *new;
+                if (uncompress_udp_header(skb, &uh))
+                        goto drop;
+
+                /*
+                 * replace the compressed UDP head by the uncompressed UDP
+                 * header
+                 */
+                new = skb_copy_expand(skb, sizeof(struct udphdr),
+                                      skb_tailroom(skb), GFP_ATOMIC);
+                kfree_skb(skb);
+
+                if (!new)
+                        return -ENOMEM;
+
+                skb = new;
+
+                skb_push(skb, sizeof(struct udphdr));
+                skb_reset_transport_header(skb);
+                skb_copy_to_linear_data(skb, &uh, sizeof(struct udphdr));
+
+                raw_dump_table(__func__, "raw UDP header dump",
+                                      (u8 *)&uh, sizeof(uh));
+
+                hdr.nexthdr = UIP_PROTO_UDP;
+        }
+
+        hdr.payload_len = htons(skb->len);
+
+        pr_debug("skb headroom size = %d, data length = %d\n",
+                 skb_headroom(skb), skb->len);
+
+        pr_debug("IPv6 header dump:\n\tversion = %d\n\tlength  = %d\n\t"
+                 "nexthdr = 0x%02x\n\thop_lim = %d\n\tdest    = %pI6c\n",
+                hdr.version, ntohs(hdr.payload_len), hdr.nexthdr,
+                hdr.hop_limit, &hdr.daddr);
+
+        raw_dump_table(__func__, "raw header dump", (u8 *)&hdr,
+                                                        sizeof(hdr));
+
+        return skb_deliver(skb, &hdr, dev, deliver_skb);
+
+drop:
+        kfree_skb(skb);
+        return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(lowpan_process_data);
+
+static u8 lowpan_compress_addr_64(u8 **hc06_ptr, u8 shift,
+                                const struct in6_addr *ipaddr,
+                                const unsigned char *lladdr)
+{
+        u8 val = 0;
+
+        if (is_addr_mac_addr_based(ipaddr, lladdr)) {
+                val = 3; /* 0-bits */
+                pr_debug("address compression 0 bits\n");
+        } else if (lowpan_is_iid_16_bit_compressable(ipaddr)) {
+                /* compress IID to 16 bits xxxx::XXXX */
+                memcpy(*hc06_ptr, &ipaddr->s6_addr16[7], 2);
+                *hc06_ptr += 2;
+                val = 2; /* 16-bits */
+                raw_dump_inline(NULL, "Compressed ipv6 addr is (16 bits)",
+                        *hc06_ptr - 2, 2);
+        } else {
+                /* do not compress IID => xxxx::IID */
+                memcpy(*hc06_ptr, &ipaddr->s6_addr16[4], 8);
+                *hc06_ptr += 8;
+                val = 1; /* 64-bits */
+                raw_dump_inline(NULL, "Compressed ipv6 addr is (64 bits)",
+                        *hc06_ptr - 8, 8);
+        }
+
+        return rol8(val, shift);
+}
+
+static void compress_udp_header(u8 **hc06_ptr, struct sk_buff *skb)
+{
+        struct udphdr *uh = udp_hdr(skb);
+        u8 tmp;
+
+        if (((ntohs(uh->source) & LOWPAN_NHC_UDP_4BIT_MASK) ==
+             LOWPAN_NHC_UDP_4BIT_PORT) &&
+            ((ntohs(uh->dest) & LOWPAN_NHC_UDP_4BIT_MASK) ==
+             LOWPAN_NHC_UDP_4BIT_PORT)) {
+                pr_debug("UDP header: both ports compression to 4 bits\n");
+                /* compression value */
+                tmp = LOWPAN_NHC_UDP_CS_P_11;
+                lowpan_push_hc_data(hc06_ptr, &tmp, sizeof(tmp));
+                /* source and destination port */
+                tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_4BIT_PORT +
+                      ((ntohs(uh->source) - LOWPAN_NHC_UDP_4BIT_PORT) << 4);
+                lowpan_push_hc_data(hc06_ptr, &tmp, sizeof(tmp));
+        } else if ((ntohs(uh->dest) & LOWPAN_NHC_UDP_8BIT_MASK) ==
+                        LOWPAN_NHC_UDP_8BIT_PORT) {
+                pr_debug("UDP header: remove 8 bits of dest\n");
+                /* compression value */
+                tmp = LOWPAN_NHC_UDP_CS_P_01;
+                lowpan_push_hc_data(hc06_ptr, &tmp, sizeof(tmp));
+                /* source port */
+                lowpan_push_hc_data(hc06_ptr, &uh->source, sizeof(uh->source));
+                /* destination port */
+                tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_8BIT_PORT;
+                lowpan_push_hc_data(hc06_ptr, &tmp, sizeof(tmp));
+        } else if ((ntohs(uh->source) & LOWPAN_NHC_UDP_8BIT_MASK) ==
+                        LOWPAN_NHC_UDP_8BIT_PORT) {
+                pr_debug("UDP header: remove 8 bits of source\n");
+                /* compression value */
+                tmp = LOWPAN_NHC_UDP_CS_P_10;
+                lowpan_push_hc_data(hc06_ptr, &tmp, sizeof(tmp));
+                /* source port */
+                tmp = ntohs(uh->source) - LOWPAN_NHC_UDP_8BIT_PORT;
+                lowpan_push_hc_data(hc06_ptr, &tmp, sizeof(tmp));
+                /* destination port */
+                lowpan_push_hc_data(hc06_ptr, &uh->dest, sizeof(uh->dest));
+        } else {
+                pr_debug("UDP header: can't compress\n");
+                /* compression value */
+                tmp = LOWPAN_NHC_UDP_CS_P_00;
+                lowpan_push_hc_data(hc06_ptr, &tmp, sizeof(tmp));
+                /* source port */
+                lowpan_push_hc_data(hc06_ptr, &uh->source, sizeof(uh->source));
+                /* destination port */
+                lowpan_push_hc_data(hc06_ptr, &uh->dest, sizeof(uh->dest));
+        }
+
+        /* checksum is always inline */
+        lowpan_push_hc_data(hc06_ptr, &uh->check, sizeof(uh->check));
+
+        /* skip the UDP header */
+        skb_pull(skb, sizeof(struct udphdr));
+}
+
+int lowpan_header_compress(struct sk_buff *skb, struct net_device *dev,
+                        unsigned short type, const void *_daddr,
+                        const void *_saddr, unsigned int len)
+{
+        u8 tmp, iphc0, iphc1, *hc06_ptr;
+        struct ipv6hdr *hdr;
+        u8 head[100] = {};
+
+        if (type != ETH_P_IPV6)
+                return -EINVAL;
+
+        hdr = ipv6_hdr(skb);
+        hc06_ptr = head + 2;
+
+        pr_debug("IPv6 header dump:\n\tversion = %d\n\tlength  = %d\n"
+                 "\tnexthdr = 0x%02x\n\thop_lim = %d\n\tdest    = %pI6c\n",
+                hdr->version, ntohs(hdr->payload_len), hdr->nexthdr,
+                hdr->hop_limit, &hdr->daddr);
+
+        raw_dump_table(__func__, "raw skb network header dump",
+                skb_network_header(skb), sizeof(struct ipv6hdr));
+
+        /*
+         * As we copy some bit-length fields, in the IPHC encoding bytes,
+         * we sometimes use |=
+         * If the field is 0, and the current bit value in memory is 1,
+         * this does not work. We therefore reset the IPHC encoding here
+         */
+        iphc0 = LOWPAN_DISPATCH_IPHC;
+        iphc1 = 0;
+
+        /* TODO: context lookup */
+
+        raw_dump_inline(__func__, "saddr",
+                        (unsigned char *)_saddr, IEEE802154_ADDR_LEN);
+        raw_dump_inline(__func__, "daddr",
+                        (unsigned char *)_daddr, IEEE802154_ADDR_LEN);
+
+        raw_dump_table(__func__,
+                        "sending raw skb network uncompressed packet",
+                        skb->data, skb->len);
+
+        /*
+         * Traffic class, flow label
+         * If flow label is 0, compress it. If traffic class is 0, compress it
+         * We have to process both in the same time as the offset of traffic
+         * class depends on the presence of version and flow label
+         */
+
+        /* hc06 format of TC is ECN | DSCP , original one is DSCP | ECN */
+        tmp = (hdr->priority << 4) | (hdr->flow_lbl[0] >> 4);
+        tmp = ((tmp & 0x03) << 6) | (tmp >> 2);
+
+        if (((hdr->flow_lbl[0] & 0x0F) == 0) &&
+             (hdr->flow_lbl[1] == 0) && (hdr->flow_lbl[2] == 0)) {
+                /* flow label can be compressed */
+                iphc0 |= LOWPAN_IPHC_FL_C;
+                if ((hdr->priority == 0) &&
+                   ((hdr->flow_lbl[0] & 0xF0) == 0)) {
+                        /* compress (elide) all */
+                        iphc0 |= LOWPAN_IPHC_TC_C;
+                } else {
+                        /* compress only the flow label */
+                        *hc06_ptr = tmp;
+                        hc06_ptr += 1;
+                }
+        } else {
+                /* Flow label cannot be compressed */
+                if ((hdr->priority == 0) &&
+                   ((hdr->flow_lbl[0] & 0xF0) == 0)) {
+                        /* compress only traffic class */
+                        iphc0 |= LOWPAN_IPHC_TC_C;
+                        *hc06_ptr = (tmp & 0xc0) | (hdr->flow_lbl[0] & 0x0F);
+                        memcpy(hc06_ptr + 1, &hdr->flow_lbl[1], 2);
+                        hc06_ptr += 3;
+                } else {
+                        /* compress nothing */
+                        memcpy(hc06_ptr, hdr, 4);
+                        /* replace the top byte with new ECN | DSCP format */
+                        *hc06_ptr = tmp;
+                        hc06_ptr += 4;
+                }
+        }
+
+        /* NOTE: payload length is always compressed */
+
+        /* Next Header is compress if UDP */
+        if (hdr->nexthdr == UIP_PROTO_UDP)
+                iphc0 |= LOWPAN_IPHC_NH_C;
+
+        if ((iphc0 & LOWPAN_IPHC_NH_C) == 0) {
+                *hc06_ptr = hdr->nexthdr;
+                hc06_ptr += 1;
+        }
+
+        /*
+         * Hop limit
+         * if 1:   compress, encoding is 01
+         * if 64:  compress, encoding is 10
+         * if 255: compress, encoding is 11
+         * else do not compress
+         */
+        switch (hdr->hop_limit) {
+        case 1:
+                iphc0 |= LOWPAN_IPHC_TTL_1;
+                break;
+        case 64:
+                iphc0 |= LOWPAN_IPHC_TTL_64;
+                break;
+        case 255:
+                iphc0 |= LOWPAN_IPHC_TTL_255;
+                break;
+        default:
+                *hc06_ptr = hdr->hop_limit;
+                hc06_ptr += 1;
+                break;
+        }
+
+        /* source address compression */
+        if (is_addr_unspecified(&hdr->saddr)) {
+                pr_debug("source address is unspecified, setting SAC\n");
+                iphc1 |= LOWPAN_IPHC_SAC;
+        /* TODO: context lookup */
+        } else if (is_addr_link_local(&hdr->saddr)) {
+                iphc1 |= lowpan_compress_addr_64(&hc06_ptr,
+                                LOWPAN_IPHC_SAM_BIT, &hdr->saddr, _saddr);
+                pr_debug("source address unicast link-local %pI6c "
+                        "iphc1 0x%02x\n", &hdr->saddr, iphc1);
+        } else {
+                pr_debug("send the full source address\n");
+                memcpy(hc06_ptr, &hdr->saddr.s6_addr16[0], 16);
+                hc06_ptr += 16;
+        }
+
+        /* destination address compression */
+        if (is_addr_mcast(&hdr->daddr)) {
+                pr_debug("destination address is multicast: ");
+                iphc1 |= LOWPAN_IPHC_M;
+                if (lowpan_is_mcast_addr_compressable8(&hdr->daddr)) {
+                        pr_debug("compressed to 1 octet\n");
+                        iphc1 |= LOWPAN_IPHC_DAM_11;
+                        /* use last byte */
+                        *hc06_ptr = hdr->daddr.s6_addr[15];
+                        hc06_ptr += 1;
+                } else if (lowpan_is_mcast_addr_compressable32(&hdr->daddr)) {
+                        pr_debug("compressed to 4 octets\n");
+                        iphc1 |= LOWPAN_IPHC_DAM_10;
+                        /* second byte + the last three */
+                        *hc06_ptr = hdr->daddr.s6_addr[1];
+                        memcpy(hc06_ptr + 1, &hdr->daddr.s6_addr[13], 3);
+                        hc06_ptr += 4;
+                } else if (lowpan_is_mcast_addr_compressable48(&hdr->daddr)) {
+                        pr_debug("compressed to 6 octets\n");
+                        iphc1 |= LOWPAN_IPHC_DAM_01;
+                        /* second byte + the last five */
+                        *hc06_ptr = hdr->daddr.s6_addr[1];
+                        memcpy(hc06_ptr + 1, &hdr->daddr.s6_addr[11], 5);
+                        hc06_ptr += 6;
+                } else {
+                        pr_debug("using full address\n");
+                        iphc1 |= LOWPAN_IPHC_DAM_00;
+                        memcpy(hc06_ptr, &hdr->daddr.s6_addr[0], 16);
+                        hc06_ptr += 16;
+                }
+        } else {
+                /* TODO: context lookup */
+                if (is_addr_link_local(&hdr->daddr)) {
+                        iphc1 |= lowpan_compress_addr_64(&hc06_ptr,
+                                LOWPAN_IPHC_DAM_BIT, &hdr->daddr, _daddr);
+                        pr_debug("dest address unicast link-local %pI6c "
+                                "iphc1 0x%02x\n", &hdr->daddr, iphc1);
+                } else {
+                        pr_debug("dest address unicast %pI6c\n", &hdr->daddr);
+                        memcpy(hc06_ptr, &hdr->daddr.s6_addr16[0], 16);
+                        hc06_ptr += 16;
+                }
+        }
+
+        /* UDP header compression */
+        if (hdr->nexthdr == UIP_PROTO_UDP)
+                compress_udp_header(&hc06_ptr, skb);
+
+        head[0] = iphc0;
+        head[1] = iphc1;
+
+        skb_pull(skb, sizeof(struct ipv6hdr));
+        skb_reset_transport_header(skb);
+        memcpy(skb_push(skb, hc06_ptr - head), head, hc06_ptr - head);
+        skb_reset_network_header(skb);
+
+        pr_debug("header len %d skb %u\n", (int)(hc06_ptr - head), skb->len);
+
+        raw_dump_table(__func__, "raw skb data dump compressed",
+                                skb->data, skb->len);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(lowpan_header_compress);
+
+MODULE_LICENSE("GPL");