inet/inet6_rth.c

   1 /* Copyright (C) 2006-2024 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <string.h>
  19 #include <netinet/in.h>
  20 #include <netinet/ip6.h>
  21
  22
  23 /* RFC 3542, 7.1
  24
  25    This function returns the number of bytes required to hold a
  26    Routing header of the specified type containing the specified
  27    number of segments (addresses).  For an IPv6 Type 0 Routing header,
  28    the number of segments must be between 0 and 127, inclusive.  */
  29 socklen_t
  30 inet6_rth_space (int type, int segments)
  31 {
  32   switch (type)
  33     {
  34     case IPV6_RTHDR_TYPE_0:
  35       if (segments < 0 || segments > 127)
  36         return 0;
  37
  38       return sizeof (struct ip6_rthdr0) + segments * sizeof (struct in6_addr);
  39     }
  40
  41   return 0;
  42 }
  43
  44
  45 /* RFC 3542, 7.2
  46
  47    This function initializes the buffer pointed to by BP to contain a
  48    Routing header of the specified type and sets ip6r_len based on the
  49    segments parameter.  */
  50 void *
  51 inet6_rth_init (void *bp, socklen_t bp_len, int type, int segments)
  52 {
  53   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
  54
  55   switch (type)
  56     {
  57     case IPV6_RTHDR_TYPE_0:
  58       /* Make sure the parameters are valid and the buffer is large enough.  */
  59       if (segments < 0 || segments > 127)
  60         break;
  61
  62       socklen_t len = (sizeof (struct ip6_rthdr0)
  63                        + segments * sizeof (struct in6_addr));
  64       if (len > bp_len)
  65         break;
  66
  67       /* Some implementations seem to initialize the whole memory area.  */
  68       memset (bp, '\0', len);
  69
  70       /* Length in units of 8 octets.  */
  71       rthdr->ip6r_len = segments * sizeof (struct in6_addr) / 8;
  72       rthdr->ip6r_type = IPV6_RTHDR_TYPE_0;
  73       return bp;
  74     }
  75
  76   return NULL;
  77 }
  78
  79
  80 /* RFC 3542, 7.3
  81
  82    This function adds the IPv6 address pointed to by addr to the end of
  83    the Routing header being constructed.  */
  84 int
  85 inet6_rth_add (void *bp, const struct in6_addr *addr)
  86 {
  87   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
  88
  89   switch (rthdr->ip6r_type)
  90     {
  91       struct ip6_rthdr0 *rthdr0;
  92     case IPV6_RTHDR_TYPE_0:
  93       rthdr0 = (struct ip6_rthdr0 *) rthdr;
  94       if (rthdr0->ip6r0_len * 8 / sizeof (struct in6_addr)
  95           - rthdr0->ip6r0_segleft < 1)
  96         return -1;
  97
  98       memcpy (&rthdr0->ip6r0_addr[rthdr0->ip6r0_segleft++],
  99               addr, sizeof (struct in6_addr));
 100
 101       return 0;
 102     }
 103
 104   return -1;
 105 }
 106
 107
 108 /* RFC 3542, 7.4
 109
 110    This function takes a Routing header extension header (pointed to by
 111    the first argument) and writes a new Routing header that sends
 112    datagrams along the reverse of that route.  The function reverses the
 113    order of the addresses and sets the segleft member in the new Routing
 114    header to the number of segments.  */
 115 int
 116 inet6_rth_reverse (const void *in, void *out)
 117 {
 118   struct ip6_rthdr *in_rthdr = (struct ip6_rthdr *) in;
 119
 120   switch (in_rthdr->ip6r_type)
 121     {
 122       struct ip6_rthdr0 *in_rthdr0;
 123       struct ip6_rthdr0 *out_rthdr0;
 124     case IPV6_RTHDR_TYPE_0:
 125       in_rthdr0 = (struct ip6_rthdr0 *) in;
 126       out_rthdr0 = (struct ip6_rthdr0 *) out;
 127
 128       /* Copy header, not the addresses.  The memory regions can overlap.  */
 129       memmove (out_rthdr0, in_rthdr0, sizeof (struct ip6_rthdr0));
 130
 131       int total = in_rthdr0->ip6r0_len * 8 / sizeof (struct in6_addr);
 132       for (int i = 0; i < total / 2; ++i)
 133         {
 134           /* Remember, IN_RTHDR0 and OUT_RTHDR0 might overlap.  */
 135           struct in6_addr temp = in_rthdr0->ip6r0_addr[i];
 136           out_rthdr0->ip6r0_addr[i] = in_rthdr0->ip6r0_addr[total - 1 - i];
 137           out_rthdr0->ip6r0_addr[total - 1 - i] = temp;
 138         }
 139       if (total % 2 != 0 && in != out)
 140         out_rthdr0->ip6r0_addr[total / 2] = in_rthdr0->ip6r0_addr[total / 2];
 141
 142       out_rthdr0->ip6r0_segleft = total;
 143
 144       return 0;
 145     }
 146
 147   return -1;
 148 }
 149
 150
 151 /* RFC 3542, 7.5
 152
 153    This function returns the number of segments (addresses) contained in
 154    the Routing header described by BP.  */
 155 int
 156 inet6_rth_segments (const void *bp)
 157 {
 158   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
 159
 160   switch (rthdr->ip6r_type)
 161     {
 162     case IPV6_RTHDR_TYPE_0:
 163
 164       return rthdr->ip6r_len * 8 / sizeof (struct in6_addr);
 165     }
 166
 167   return -1;
 168 }
 169
 170
 171 /* RFC 3542, 7.6
 172
 173    This function returns a pointer to the IPv6 address specified by
 174    index (which must have a value between 0 and one less than the
 175    value returned by 'inet6_rth_segments') in the Routing header
 176    described by BP.  */
 177 struct in6_addr *
 178 inet6_rth_getaddr (const void *bp, int index)
 179 {
 180   struct ip6_rthdr *rthdr = (struct ip6_rthdr *) bp;
 181
 182   switch (rthdr->ip6r_type)
 183     {
 184        struct ip6_rthdr0 *rthdr0;
 185     case IPV6_RTHDR_TYPE_0:
 186       rthdr0 = (struct ip6_rthdr0 *) rthdr;
 187
 188       if (index >= rthdr0->ip6r0_len * 8 / sizeof (struct in6_addr))
 189         break;
 190
 191       return &rthdr0->ip6r0_addr[index];
 192     }
 193
 194   return NULL;
 195 }