inet/inet6_rth.c

   1 /* Copyright (C) 2006-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2006.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <string.h>
  20 #include <netinet/in.h>
  21 #include <netinet/ip6.h>
  22
  23
  24 /* RFC 3542, 7.1
  25
  26    This function returns the number of bytes required to hold a
  27    Routing header of the specified type containing the specified
  28    number of segments (addresses).  For an IPv6 Type 0 Routing header,
  29    the number of segments must be between 0 and 127, inclusive.  */
  30 socklen_t
  31 inet6_rth_space (int type, int segments)
  32 {
  33   switch (type)
  34     {
  35     case IPV6_RTHDR_TYPE_0:
  36       if (segments < 0 || segments > 127)
  37         return 0;
  38
  39       return sizeof (struct ip6_rthdr0) + segments * sizeof (struct in6_addr);
  40     }
  41
  42   return 0;
  43 }
  44
  45
  46 /* RFC 3542, 7.2
  47
  48    This function initializes the buffer pointed to by BP to contain a
  49    Routing header of the specified type and sets ip6r_len based on the
  50    segments parameter.  */
  51 void *
  52 inet6_rth_init (void *bp, socklen_t bp_len, int type, int segments)
  53 {
  54   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
  55
  56   switch (type)
  57     {
  58     case IPV6_RTHDR_TYPE_0:
  59       /* Make sure the parameters are valid and the buffer is large enough.  */
  60       if (segments < 0 || segments > 127)
  61         break;
  62
  63       socklen_t len = (sizeof (struct ip6_rthdr0)
  64                        + segments * sizeof (struct in6_addr));
  65       if (len > bp_len)
  66         break;
  67
  68       /* Some implementations seem to initialize the whole memory area.  */
  69       memset (bp, '\0', len);
  70
  71       /* Length in units of 8 octets.  */
  72       rthdr->ip6r_len = segments * sizeof (struct in6_addr) / 8;
  73       rthdr->ip6r_type = IPV6_RTHDR_TYPE_0;
  74       return bp;
  75     }
  76
  77   return NULL;
  78 }
  79
  80
  81 /* RFC 3542, 7.3
  82
  83    This function adds the IPv6 address pointed to by addr to the end of
  84    the Routing header being constructed.  */
  85 int
  86 inet6_rth_add (void *bp, const struct in6_addr *addr)
  87 {
  88   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
  89
  90   switch (rthdr->ip6r_type)
  91     {
  92       struct ip6_rthdr0 *rthdr0;
  93     case IPV6_RTHDR_TYPE_0:
  94       rthdr0 = (struct ip6_rthdr0 *) rthdr;
  95       if (rthdr0->ip6r0_len * 8 / sizeof (struct in6_addr)
  96           - rthdr0->ip6r0_segleft < 1)
  97         return -1;
  98
  99       memcpy (&rthdr0->ip6r0_addr[rthdr0->ip6r0_segleft++],
 100               addr, sizeof (struct in6_addr));
 101
 102       return 0;
 103     }
 104
 105   return -1;
 106 }
 107
 108
 109 /* RFC 3542, 7.4
 110
 111    This function takes a Routing header extension header (pointed to by
 112    the first argument) and writes a new Routing header that sends
 113    datagrams along the reverse of that route.  The function reverses the
 114    order of the addresses and sets the segleft member in the new Routing
 115    header to the number of segments.  */
 116 int
 117 inet6_rth_reverse (const void *in, void *out)
 118 {
 119   struct ip6_rthdr *in_rthdr = (struct ip6_rthdr *) in;
 120
 121   switch (in_rthdr->ip6r_type)
 122     {
 123       struct ip6_rthdr0 *in_rthdr0;
 124       struct ip6_rthdr0 *out_rthdr0;
 125     case IPV6_RTHDR_TYPE_0:
 126       in_rthdr0 = (struct ip6_rthdr0 *) in;
 127       out_rthdr0 = (struct ip6_rthdr0 *) out;
 128
 129       /* Copy header, not the addresses.  The memory regions can overlap.  */
 130       memmove (out_rthdr0, in_rthdr0, sizeof (struct ip6_rthdr0));
 131
 132       int total = in_rthdr0->ip6r0_len * 8 / sizeof (struct in6_addr);
 133       for (int i = 0; i < total / 2; ++i)
 134         {
 135           /* Remember, IN_RTHDR0 and OUT_RTHDR0 might overlap.  */
 136           struct in6_addr temp = in_rthdr0->ip6r0_addr[i];
 137           out_rthdr0->ip6r0_addr[i] = in_rthdr0->ip6r0_addr[total - 1 - i];
 138           out_rthdr0->ip6r0_addr[total - 1 - i] = temp;
 139         }
 140       if (total % 2 != 0 && in != out)
 141         out_rthdr0->ip6r0_addr[total / 2] = in_rthdr0->ip6r0_addr[total / 2];
 142
 143       out_rthdr0->ip6r0_segleft = total;
 144
 145       return 0;
 146     }
 147
 148   return -1;
 149 }
 150
 151
 152 /* RFC 3542, 7.5
 153
 154    This function returns the number of segments (addresses) contained in
 155    the Routing header described by BP.  */
 156 int
 157 inet6_rth_segments (const void *bp)
 158 {
 159   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
 160
 161   switch (rthdr->ip6r_type)
 162     {
 163     case IPV6_RTHDR_TYPE_0:
 164
 165       return rthdr->ip6r_len * 8 / sizeof (struct in6_addr);
 166     }
 167
 168   return -1;
 169 }
 170
 171
 172 /* RFC 3542, 7.6
 173
 174    This function returns a pointer to the IPv6 address specified by
 175    index (which must have a value between 0 and one less than the
 176    value returned by 'inet6_rth_segments') in the Routing header
 177    described by BP.  */
 178 struct in6_addr *
 179 inet6_rth_getaddr (const void *bp, int index)
 180 {
 181   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
 182
 183   switch (rthdr->ip6r_type)
 184     {
 185        struct ip6_rthdr0 *rthdr0;
 186     case IPV6_RTHDR_TYPE_0:
 187       rthdr0 = (struct ip6_rthdr0 *) rthdr;
 188
 189       if (index >= rthdr0->ip6r0_len * 8 / sizeof (struct in6_addr))
 190         break;
 191
 192       return &rthdr0->ip6r0_addr[index];
 193     }
 194
 195   return NULL;
 196 }