net/6lowpan/nhc.c

   1 /*
   2  *      6LoWPAN next header compression
   3  *
   4  *
   5  *      Authors:
   6  *      Alexander Aring         <aar@pengutronix.de>
   7  *
   8  *      This program is free software; you can redistribute it and/or
   9  *      modify it under the terms of the GNU General Public License
  10  *      as published by the Free Software Foundation; either version
  11  *      2 of the License, or (at your option) any later version.
  12  */
  13
  14 #include <linux/netdevice.h>
  15
  16 #include <net/ipv6.h>
  17
  18 #include "nhc.h"
  19
  20 static struct rb_root rb_root = RB_ROOT;
  21 static struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX];
  22 static DEFINE_SPINLOCK(lowpan_nhc_lock);
  23
  24 static int lowpan_nhc_insert(struct lowpan_nhc *nhc)
  25 {
  26         struct rb_node **new = &rb_root.rb_node, *parent = NULL;
  27
  28         /* Figure out where to put new node */
  29         while (*new) {
  30                 struct lowpan_nhc *this = rb_entry(*new, struct lowpan_nhc,
  31                                                    node);
  32                 int result, len_dif, len;
  33
  34                 len_dif = nhc->idlen - this->idlen;
  35
  36                 if (nhc->idlen < this->idlen)
  37                         len = nhc->idlen;
  38                 else
  39                         len = this->idlen;
  40
  41                 result = memcmp(nhc->id, this->id, len);
  42                 if (!result)
  43                         result = len_dif;
  44
  45                 parent = *new;
  46                 if (result < 0)
  47                         new = &((*new)->rb_left);
  48                 else if (result > 0)
  49                         new = &((*new)->rb_right);
  50                 else
  51                         return -EEXIST;
  52         }
  53
  54         /* Add new node and rebalance tree. */
  55         rb_link_node(&nhc->node, parent, new);
  56         rb_insert_color(&nhc->node, &rb_root);
  57
  58         return 0;
  59 }
  60
  61 static void lowpan_nhc_remove(struct lowpan_nhc *nhc)
  62 {
  63         rb_erase(&nhc->node, &rb_root);
  64 }
  65
  66 static struct lowpan_nhc *lowpan_nhc_by_nhcid(const struct sk_buff *skb)
  67 {
  68         struct rb_node *node = rb_root.rb_node;
  69         const u8 *nhcid_skb_ptr = skb->data;
  70
  71         while (node) {
  72                 struct lowpan_nhc *nhc = rb_entry(node, struct lowpan_nhc,
  73                                                   node);
  74                 u8 nhcid_skb_ptr_masked[LOWPAN_NHC_MAX_ID_LEN];
  75                 int result, i;
  76
  77                 if (nhcid_skb_ptr + nhc->idlen > skb->data + skb->len)
  78                         return NULL;
  79
  80                 /* copy and mask afterwards the nhid value from skb */
  81                 memcpy(nhcid_skb_ptr_masked, nhcid_skb_ptr, nhc->idlen);
  82                 for (i = 0; i < nhc->idlen; i++)
  83                         nhcid_skb_ptr_masked[i] &= nhc->idmask[i];
  84
  85                 result = memcmp(nhcid_skb_ptr_masked, nhc->id, nhc->idlen);
  86                 if (result < 0)
  87                         node = node->rb_left;
  88                 else if (result > 0)
  89                         node = node->rb_right;
  90                 else
  91                         return nhc;
  92         }
  93
  94         return NULL;
  95 }
  96
  97 int lowpan_nhc_check_compression(struct sk_buff *skb,
  98                                  const struct ipv6hdr *hdr, u8 **hc_ptr)
  99 {
 100         struct lowpan_nhc *nhc;
 101         int ret = 0;
 102
 103         spin_lock_bh(&lowpan_nhc_lock);
 104
 105         nhc = lowpan_nexthdr_nhcs[hdr->nexthdr];
 106         if (!(nhc && nhc->compress))
 107                 ret = -ENOENT;
 108
 109         spin_unlock_bh(&lowpan_nhc_lock);
 110
 111         return ret;
 112 }
 113
 114 int lowpan_nhc_do_compression(struct sk_buff *skb, const struct ipv6hdr *hdr,
 115                               u8 **hc_ptr)
 116 {
 117         int ret;
 118         struct lowpan_nhc *nhc;
 119
 120         spin_lock_bh(&lowpan_nhc_lock);
 121
 122         nhc = lowpan_nexthdr_nhcs[hdr->nexthdr];
 123         /* check if the nhc module was removed in unlocked part.
 124          * TODO: this is a workaround we should prevent unloading
 125          * of nhc modules while unlocked part, this will always drop
 126          * the lowpan packet but it's very unlikely.
 127          *
 128          * Solution isn't easy because we need to decide at
 129          * lowpan_nhc_check_compression if we do a compression or not.
 130          * Because the inline data which is added to skb, we can't move this
 131          * handling.
 132          */
 133         if (unlikely(!nhc || !nhc->compress)) {
 134                 ret = -EINVAL;
 135                 goto out;
 136         }
 137
 138         /* In the case of RAW sockets the transport header is not set by
 139          * the ip6 stack so we must set it ourselves
 140          */
 141         if (skb->transport_header == skb->network_header)
 142                 skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 143
 144         ret = nhc->compress(skb, hc_ptr);
 145         if (ret < 0)
 146                 goto out;
 147
 148         /* skip the transport header */
 149         skb_pull(skb, nhc->nexthdrlen);
 150
 151 out:
 152         spin_unlock_bh(&lowpan_nhc_lock);
 153
 154         return ret;
 155 }
 156
 157 int lowpan_nhc_do_uncompression(struct sk_buff *skb,
 158                                 const struct net_device *dev,
 159                                 struct ipv6hdr *hdr)
 160 {
 161         struct lowpan_nhc *nhc;
 162         int ret;
 163
 164         spin_lock_bh(&lowpan_nhc_lock);
 165
 166         nhc = lowpan_nhc_by_nhcid(skb);
 167         if (nhc) {
 168                 if (nhc->uncompress) {
 169                         ret = nhc->uncompress(skb, sizeof(struct ipv6hdr) +
 170                                               nhc->nexthdrlen);
 171                         if (ret < 0) {
 172                                 spin_unlock_bh(&lowpan_nhc_lock);
 173                                 return ret;
 174                         }
 175                 } else {
 176                         spin_unlock_bh(&lowpan_nhc_lock);
 177                         netdev_warn(dev, "received nhc id for %s which is not implemented.\n",
 178                                     nhc->name);
 179                         return -ENOTSUPP;
 180                 }
 181         } else {
 182                 spin_unlock_bh(&lowpan_nhc_lock);
 183                 netdev_warn(dev, "received unknown nhc id which was not found.\n");
 184                 return -ENOENT;
 185         }
 186
 187         hdr->nexthdr = nhc->nexthdr;
 188         skb_reset_transport_header(skb);
 189         raw_dump_table(__func__, "raw transport header dump",
 190                        skb_transport_header(skb), nhc->nexthdrlen);
 191
 192         spin_unlock_bh(&lowpan_nhc_lock);
 193
 194         return 0;
 195 }
 196
 197 int lowpan_nhc_add(struct lowpan_nhc *nhc)
 198 {
 199         int ret;
 200
 201         if (!nhc->idlen || !nhc->idsetup)
 202                 return -EINVAL;
 203
 204         WARN_ONCE(nhc->idlen > LOWPAN_NHC_MAX_ID_LEN,
 205                   "LOWPAN_NHC_MAX_ID_LEN should be updated to %zd.\n",
 206                   nhc->idlen);
 207
 208         nhc->idsetup(nhc);
 209
 210         spin_lock_bh(&lowpan_nhc_lock);
 211
 212         if (lowpan_nexthdr_nhcs[nhc->nexthdr]) {
 213                 ret = -EEXIST;
 214                 goto out;
 215         }
 216
 217         ret = lowpan_nhc_insert(nhc);
 218         if (ret < 0)
 219                 goto out;
 220
 221         lowpan_nexthdr_nhcs[nhc->nexthdr] = nhc;
 222 out:
 223         spin_unlock_bh(&lowpan_nhc_lock);
 224         return ret;
 225 }
 226 EXPORT_SYMBOL(lowpan_nhc_add);
 227
 228 void lowpan_nhc_del(struct lowpan_nhc *nhc)
 229 {
 230         spin_lock_bh(&lowpan_nhc_lock);
 231
 232         lowpan_nhc_remove(nhc);
 233         lowpan_nexthdr_nhcs[nhc->nexthdr] = NULL;
 234
 235         spin_unlock_bh(&lowpan_nhc_lock);
 236
 237         synchronize_net();
 238 }
 239 EXPORT_SYMBOL(lowpan_nhc_del);