LXR linux/net/6lowpan/nhc

   1/*
   2 *      6LoWPAN IPv6 UDP compression according to RFC6282
   3 *
   4 *
   5 *      Authors:
   6 *      Alexander Aring <aar@pengutronix.de>
   7 *
   8 *      Orignal written by:
   9 *      Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
  10 *      Jon Smirl <jonsmirl@gmail.com>
  11 *
  12 *      This program is free software; you can redistribute it and/or
  13 *      modify it under the terms of the GNU General Public License
  14 *      as published by the Free Software Foundation; either version
  15 *      2 of the License, or (at your option) any later version.
  16 */
  17
  18#include "nhc.h"
  19
  20#define LOWPAN_NHC_UDP_MASK             0xF8
  21#define LOWPAN_NHC_UDP_ID               0xF0
  22#define LOWPAN_NHC_UDP_IDLEN            1
  23
  24#define LOWPAN_NHC_UDP_4BIT_PORT        0xF0B0
  25#define LOWPAN_NHC_UDP_4BIT_MASK        0xFFF0
  26#define LOWPAN_NHC_UDP_8BIT_PORT        0xF000
  27#define LOWPAN_NHC_UDP_8BIT_MASK        0xFF00
  28
  29/* values for port compression, _with checksum_ ie bit 5 set to 0 */
  30
  31/* all inline */
  32#define LOWPAN_NHC_UDP_CS_P_00  0xF0
  33/* source 16bit inline, dest = 0xF0 + 8 bit inline */
  34#define LOWPAN_NHC_UDP_CS_P_01  0xF1
  35/* source = 0xF0 + 8bit inline, dest = 16 bit inline */
  36#define LOWPAN_NHC_UDP_CS_P_10  0xF2
  37/* source & dest = 0xF0B + 4bit inline */
  38#define LOWPAN_NHC_UDP_CS_P_11  0xF3
  39/* checksum elided */
  40#define LOWPAN_NHC_UDP_CS_C     0x04
  41
  42static int udp_uncompress(struct sk_buff *skb, size_t needed)
  43{
  44        u8 tmp = 0, val = 0;
  45        struct udphdr uh;
  46        bool fail;
  47        int err;
  48
  49        fail = lowpan_fetch_skb(skb, &tmp, sizeof(tmp));
  50
  51        pr_debug("UDP header uncompression\n");
  52        switch (tmp & LOWPAN_NHC_UDP_CS_P_11) {
  53        case LOWPAN_NHC_UDP_CS_P_00:
  54                fail |= lowpan_fetch_skb(skb, &uh.source, sizeof(uh.source));
  55                fail |= lowpan_fetch_skb(skb, &uh.dest, sizeof(uh.dest));
  56                break;
  57        case LOWPAN_NHC_UDP_CS_P_01:
  58                fail |= lowpan_fetch_skb(skb, &uh.source, sizeof(uh.source));
  59                fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
  60                uh.dest = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
  61                break;
  62        case LOWPAN_NHC_UDP_CS_P_10:
  63                fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
  64                uh.source = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
  65                fail |= lowpan_fetch_skb(skb, &uh.dest, sizeof(uh.dest));
  66                break;
  67        case LOWPAN_NHC_UDP_CS_P_11:
  68                fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
  69                uh.source = htons(LOWPAN_NHC_UDP_4BIT_PORT + (val >> 4));
  70                uh.dest = htons(LOWPAN_NHC_UDP_4BIT_PORT + (val & 0x0f));
  71                break;
  72        default:
  73                BUG();
  74        }
  75
  76        pr_debug("uncompressed UDP ports: src = %d, dst = %d\n",
  77                 ntohs(uh.source), ntohs(uh.dest));
  78
  79        /* checksum */
  80        if (tmp & LOWPAN_NHC_UDP_CS_C) {
  81                pr_debug_ratelimited("checksum elided currently not supported\n");
  82                fail = true;
  83        } else {
  84                fail |= lowpan_fetch_skb(skb, &uh.check, sizeof(uh.check));
  85        }
  86
  87        if (fail)
  88                return -EINVAL;
  89
  90        /* UDP length needs to be infered from the lower layers
  91         * here, we obtain the hint from the remaining size of the
  92         * frame
  93         */
  94        switch (lowpan_dev(skb->dev)->lltype) {
  95        case LOWPAN_LLTYPE_IEEE802154:
  96                if (lowpan_802154_cb(skb)->d_size)
  97                        uh.len = htons(lowpan_802154_cb(skb)->d_size -
  98                                       sizeof(struct ipv6hdr));
  99                else
 100                        uh.len = htons(skb->len + sizeof(struct udphdr));
 101                break;
 102        default:
 103                uh.len = htons(skb->len + sizeof(struct udphdr));
 104                break;
 105        }
 106        pr_debug("uncompressed UDP length: src = %d", ntohs(uh.len));
 107
 108        /* replace the compressed UDP head by the uncompressed UDP
 109         * header
 110         */
 111        err = skb_cow(skb, needed);
 112        if (unlikely(err))
 113                return err;
 114
 115        skb_push(skb, sizeof(struct udphdr));
 116        skb_copy_to_linear_data(skb, &uh, sizeof(struct udphdr));
 117
 118        return 0;
 119}
 120
 121static int udp_compress(struct sk_buff *skb, u8 **hc_ptr)
 122{
 123        const struct udphdr *uh = udp_hdr(skb);
 124        u8 tmp;
 125
 126        if (((ntohs(uh->source) & LOWPAN_NHC_UDP_4BIT_MASK) ==
 127             LOWPAN_NHC_UDP_4BIT_PORT) &&
 128            ((ntohs(uh->dest) & LOWPAN_NHC_UDP_4BIT_MASK) ==
 129             LOWPAN_NHC_UDP_4BIT_PORT)) {
 130                pr_debug("UDP header: both ports compression to 4 bits\n");
 131                /* compression value */
 132                tmp = LOWPAN_NHC_UDP_CS_P_11;
 133                lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
 134                /* source and destination port */
 135                tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_4BIT_PORT +
 136                      ((ntohs(uh->source) - LOWPAN_NHC_UDP_4BIT_PORT) << 4);
 137                lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
 138        } else if ((ntohs(uh->dest) & LOWPAN_NHC_UDP_8BIT_MASK) ==
 139                        LOWPAN_NHC_UDP_8BIT_PORT) {
 140                pr_debug("UDP header: remove 8 bits of dest\n");
 141                /* compression value */
 142                tmp = LOWPAN_NHC_UDP_CS_P_01;
 143                lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
 144                /* source port */
 145                lowpan_push_hc_data(hc_ptr, &uh->source, sizeof(uh->source));
 146                /* destination port */
 147                tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_8BIT_PORT;
 148                lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
 149        } else if ((ntohs(uh->source) & LOWPAN_NHC_UDP_8BIT_MASK) ==
 150                        LOWPAN_NHC_UDP_8BIT_PORT) {
 151                pr_debug("UDP header: remove 8 bits of source\n");
 152                /* compression value */
 153                tmp = LOWPAN_NHC_UDP_CS_P_10;
 154                lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
 155                /* source port */
 156                tmp = ntohs(uh->source) - LOWPAN_NHC_UDP_8BIT_PORT;
 157                lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
 158                /* destination port */
 159                lowpan_push_hc_data(hc_ptr, &uh->dest, sizeof(uh->dest));
 160        } else {
 161                pr_debug("UDP header: can't compress\n");
 162                /* compression value */
 163                tmp = LOWPAN_NHC_UDP_CS_P_00;
 164                lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
 165                /* source port */
 166                lowpan_push_hc_data(hc_ptr, &uh->source, sizeof(uh->source));
 167                /* destination port */
 168                lowpan_push_hc_data(hc_ptr, &uh->dest, sizeof(uh->dest));
 169        }
 170
 171        /* checksum is always inline */
 172        lowpan_push_hc_data(hc_ptr, &uh->check, sizeof(uh->check));
 173
 174        return 0;
 175}
 176
 177static void udp_nhid_setup(struct lowpan_nhc *nhc)
 178{
 179        nhc->id[0] = LOWPAN_NHC_UDP_ID;
 180        nhc->idmask[0] = LOWPAN_NHC_UDP_MASK;
 181}
 182
 183LOWPAN_NHC(nhc_udp, "RFC6282 UDP", NEXTHDR_UDP, sizeof(struct udphdr),
 184           udp_nhid_setup, LOWPAN_NHC_UDP_IDLEN, udp_uncompress, udp_compress);
 185
 186module_lowpan_nhc(nhc_udp);
 187MODULE_DESCRIPTION("6LoWPAN next header RFC6282 UDP compression");
 188MODULE_LICENSE("GPL");
 189