inet/inet6_rth.c

   1 /* Copyright (C) 2006, 2009 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       if (rthdr0->ip6r0_len * 8 / sizeof (struct in6_addr)
  97           - rthdr0->ip6r0_segleft < 1)
  98         return -1;
  99
 100       memcpy (&rthdr0->ip6r0_addr[rthdr0->ip6r0_segleft++],
 101               addr, sizeof (struct in6_addr));
 102
 103       return 0;
 104     }
 105
 106   return -1;
 107 }
 108
 109
 110 /* RFC 3542, 7.4
 111
 112    This function takes a Routing header extension header (pointed to by
 113    the first argument) and writes a new Routing header that sends
 114    datagrams along the reverse of that route.  The function reverses the
 115    order of the addresses and sets the segleft member in the new Routing
 116    header to the number of segments.  */
 117 int
 118 inet6_rth_reverse (const void *in, void *out)
 119 {
 120   struct ip6_rthdr *in_rthdr = (struct ip6_rthdr *) in;
 121
 122   switch (in_rthdr->ip6r_type)
 123     {
 124       struct ip6_rthdr0 *in_rthdr0;
 125       struct ip6_rthdr0 *out_rthdr0;
 126     case IPV6_RTHDR_TYPE_0:
 127       in_rthdr0 = (struct ip6_rthdr0 *) in;
 128       out_rthdr0 = (struct ip6_rthdr0 *) out;
 129
 130       /* Copy header, not the addresses.  The memory regions can overlap.  */
 131       memmove (out_rthdr0, in_rthdr0, sizeof (struct ip6_rthdr0));
 132
 133       int total = in_rthdr0->ip6r0_len * 8 / sizeof (struct in6_addr);
 134       for (int i = 0; i < total / 2; ++i)
 135         {
 136           /* Remember, IN_RTHDR0 and OUT_RTHDR0 might overlap.  */
 137           struct in6_addr temp = in_rthdr0->ip6r0_addr[i];
 138           out_rthdr0->ip6r0_addr[i] = in_rthdr0->ip6r0_addr[total - 1 - i];
 139           out_rthdr0->ip6r0_addr[total - 1 - i] = temp;
 140         }
 141       if (total % 2 != 0 && in != out)
 142         out_rthdr0->ip6r0_addr[total / 2] = in_rthdr0->ip6r0_addr[total / 2];
 143
 144       out_rthdr0->ip6r0_segleft = total;
 145
 146       return 0;
 147     }
 148
 149   return -1;
 150 }
 151
 152
 153 /* RFC 3542, 7.5
 154
 155    This function returns the number of segments (addresses) contained in
 156    the Routing header described by BP.  */
 157 int
 158 inet6_rth_segments (const void *bp)
 159 {
 160   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
 161
 162   switch (rthdr->ip6r_type)
 163     {
 164     case IPV6_RTHDR_TYPE_0:
 165
 166       return rthdr->ip6r_len * 8 / sizeof (struct in6_addr);
 167     }
 168
 169   return -1;
 170 }
 171
 172
 173 /* RFC 3542, 7.6
 174
 175    This function returns a pointer to the IPv6 address specified by
 176    index (which must have a value between 0 and one less than the
 177    value returned by 'inet6_rth_segments') in the Routing header
 178    described by BP.  */
 179 struct in6_addr *
 180 inet6_rth_getaddr (const void *bp, int index)
 181 {
 182   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
 183
 184   switch (rthdr->ip6r_type)
 185     {
 186        struct ip6_rthdr0 *rthdr0;
 187     case IPV6_RTHDR_TYPE_0:
 188       rthdr0 = (struct ip6_rthdr0 *) rthdr;
 189
 190       if (index >= rthdr0->ip6r0_len * 8 / sizeof (struct in6_addr))
 191         break;
 192
 193       return &rthdr0->ip6r0_addr[index];
 194     }
 195
 196   return NULL;
 197 }