inet/inet6_rth.c

   1 /* Copyright (C) 2006 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <string.h>
  21 #include <netinet/in.h>
  22 #include <netinet/ip6.h>
  23
  24
  25 /* RFC 3542, 7.1
  26
  27    This function returns the number of bytes required to hold a
  28    Routing header of the specified type containing the specified
  29    number of segments (addresses).  For an IPv6 Type 0 Routing header,
  30    the number of segments must be between 0 and 127, inclusive.  */
  31 socklen_t
  32 inet6_rth_space (int type, int segments)
  33 {
  34   switch (type)
  35     {
  36     case IPV6_RTHDR_TYPE_0:
  37       if (segments < 0 || segments > 127)
  38         return 0;
  39
  40       return sizeof (struct ip6_rthdr0) + segments * sizeof (struct in6_addr);
  41     }
  42
  43   return 0;
  44 }
  45
  46
  47 /* RFC 3542, 7.2
  48
  49    This function initializes the buffer pointed to by BP to contain a
  50    Routing header of the specified type and sets ip6r_len based on the
  51    segments parameter.  */
  52 void *
  53 inet6_rth_init (void *bp, socklen_t bp_len, int type, int segments)
  54 {
  55   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
  56
  57   switch (type)
  58     {
  59     case IPV6_RTHDR_TYPE_0:
  60       /* Make sure the parameters are valid and the buffer is large enough.  */
  61       if (segments < 0 || segments > 127)
  62         break;
  63
  64       socklen_t len = (sizeof (struct ip6_rthdr0)
  65                        + segments * sizeof (struct in6_addr));
  66       if (len > bp_len)
  67         break;
  68
  69       /* Some implementations seem to initialize the whole memory area.  */
  70       memset (bp, '\0', len);
  71
  72       /* Length in units of 8 octets.  */
  73       rthdr->ip6r_len = segments * sizeof (struct in6_addr) / 8;
  74       rthdr->ip6r_type = IPV6_RTHDR_TYPE_0;
  75       return bp;
  76     }
  77
  78   return NULL;
  79 }
  80
  81
  82 /* RFC 3542, 7.3
  83
  84    This function adds the IPv6 address pointed to by addr to the end of
  85    the Routing header being constructed.  */
  86 int
  87 inet6_rth_add (void *bp, const struct in6_addr *addr)
  88 {
  89   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
  90
  91   switch (rthdr->ip6r_type)
  92     {
  93       struct ip6_rthdr0 *rthdr0;
  94     case IPV6_RTHDR_TYPE_0:
  95       rthdr0 = (struct ip6_rthdr0 *) rthdr;
  96
  97       memcpy (&rthdr0->ip6r0_addr[rthdr0->ip6r0_segleft++],
  98               addr, sizeof (struct in6_addr));
  99
 100       return 0;
 101     }
 102
 103   return -1;
 104 }
 105
 106
 107 /* RFC 3542, 7.4
 108
 109    This function takes a Routing header extension header (pointed to by
 110    the first argument) and writes a new Routing header that sends
 111    datagrams along the reverse of that route.  The function reverses the
 112    order of the addresses and sets the segleft member in the new Routing
 113    header to the number of segments.  */
 114 int
 115 inet6_rth_reverse (const void *in, void *out)
 116 {
 117   struct ip6_rthdr *in_rthdr = (struct ip6_rthdr *) in;
 118
 119   switch (in_rthdr->ip6r_type)
 120     {
 121       struct ip6_rthdr0 *in_rthdr0;
 122       struct ip6_rthdr0 *out_rthdr0;
 123     case IPV6_RTHDR_TYPE_0:
 124       in_rthdr0 = (struct ip6_rthdr0 *) in;
 125       out_rthdr0 = (struct ip6_rthdr0 *) out;
 126
 127       /* Copy header, not the addresses.  The memory regions can overlap.  */
 128       memmove (out_rthdr0, in_rthdr0, sizeof (struct ip6_rthdr0));
 129
 130       int total = in_rthdr0->ip6r0_segleft * 8 / sizeof (struct in6_addr);
 131       for (int i = 0; i < total / 2; ++i)
 132         {
 133           /* Remember, IN_RTHDR0 and OUT_RTHDR0 might overlap.  */
 134           struct in6_addr temp = in_rthdr0->ip6r0_addr[i];
 135           out_rthdr0->ip6r0_addr[i] = in_rthdr0->ip6r0_addr[total - 1 - i];
 136           out_rthdr0->ip6r0_addr[total - 1 - i] = temp;
 137         }
 138       if (total % 2 != 0 && in != out)
 139         out_rthdr0->ip6r0_addr[total / 2] = in_rthdr0->ip6r0_addr[total / 2];
 140
 141       return 0;
 142     }
 143
 144   return -1;
 145 }
 146
 147
 148 /* RFC 3542, 7.5
 149
 150    This function returns the number of segments (addresses) contained in
 151    the Routing header described by BP.  */
 152 int
 153 inet6_rth_segments (const void *bp)
 154 {
 155   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
 156
 157   switch (rthdr->ip6r_type)
 158     {
 159     case IPV6_RTHDR_TYPE_0:
 160
 161       return rthdr->ip6r_len * 8 / sizeof (struct in6_addr);
 162     }
 163
 164   return -1;
 165 }
 166
 167
 168 /* RFC 3542, 7.6
 169
 170    This function returns a pointer to the IPv6 address specified by
 171    index (which must have a value between 0 and one less than the
 172    value returned by 'inet6_rth_segments') in the Routing header
 173    described by BP.  */
 174 struct in6_addr *
 175 inet6_rth_getaddr (const void *bp, int index)
 176 {
 177   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
 178
 179   switch (rthdr->ip6r_type)
 180     {
 181        struct ip6_rthdr0 *rthdr0;
 182     case IPV6_RTHDR_TYPE_0:
 183       rthdr0 = (struct ip6_rthdr0 *) rthdr;
 184
 185       if (index >= rthdr0->ip6r0_len * 8 / sizeof (struct in6_addr))
 186         break;
 187
 188       return &rthdr0->ip6r0_addr[index];
 189     }
 190
 191   return NULL;
 192 }