sysdeps/unix/sysv/linux/check_pf.c

   1 /* Determine protocol families for which interfaces exist.  Linux version.
   2    Copyright (C) 2003, 2006 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   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 <assert.h>
  21 #include <errno.h>
  22 #include <ifaddrs.h>
  23 #include <netdb.h>
  24 #include <stddef.h>
  25 #include <string.h>
  26 #include <time.h>
  27 #include <unistd.h>
  28 #include <sys/socket.h>
  29
  30 #include <not-cancel.h>
  31 #include <kernel-features.h>
  32
  33 #include "netlinkaccess.h"
  34
  35 #ifndef IFA_F_TEMPORARY
  36 # define IFA_F_TEMPORARY IFA_F_SECONDARY
  37 #endif
  38 #ifndef IFA_F_HOMEADDRESS
  39 # define IFA_F_HOMEADDRESS 0
  40 #endif
  41
  42
  43 static int
  44 make_request (int fd, pid_t pid, bool *seen_ipv4, bool *seen_ipv6,
  45               struct in6addrinfo **in6ai, size_t *in6ailen)
  46 {
  47   struct req
  48   {
  49     struct nlmsghdr nlh;
  50     struct rtgenmsg g;
  51     /* struct rtgenmsg consists of a single byte.  This means there
  52        are three bytes of padding included in the REQ definition.
  53        We make them explicit here.  */
  54     char pad[3];
  55   } req;
  56   struct sockaddr_nl nladdr;
  57
  58   req.nlh.nlmsg_len = sizeof (req);
  59   req.nlh.nlmsg_type = RTM_GETADDR;
  60   req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
  61   req.nlh.nlmsg_pid = 0;
  62   req.nlh.nlmsg_seq = time (NULL);
  63   req.g.rtgen_family = AF_UNSPEC;
  64
  65   assert (sizeof (req) - offsetof (struct req, pad) == 3);
  66   memset (req.pad, '\0', sizeof (req.pad));
  67
  68   memset (&nladdr, '\0', sizeof (nladdr));
  69   nladdr.nl_family = AF_NETLINK;
  70
  71   if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
  72                                     (struct sockaddr *) &nladdr,
  73                                     sizeof (nladdr))) < 0)
  74     return -1;
  75
  76   *seen_ipv4 = false;
  77   *seen_ipv6 = false;
  78
  79   bool done = false;
  80   char buf[4096];
  81   struct iovec iov = { buf, sizeof (buf) };
  82   struct in6ailist
  83   {
  84     struct in6addrinfo info;
  85     struct in6ailist *next;
  86   } *in6ailist = NULL;
  87   size_t in6ailistlen = 0;
  88
  89   do
  90     {
  91       struct msghdr msg =
  92         {
  93           (void *) &nladdr, sizeof (nladdr),
  94           &iov, 1,
  95           NULL, 0,
  96           0
  97         };
  98
  99       ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
 100       if (read_len < 0)
 101         return -1;
 102
 103       if (msg.msg_flags & MSG_TRUNC)
 104         return -1;
 105
 106       struct nlmsghdr *nlmh;
 107       for (nlmh = (struct nlmsghdr *) buf;
 108            NLMSG_OK (nlmh, (size_t) read_len);
 109            nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
 110         {
 111           if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
 112               || nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
 113             continue;
 114
 115           if (nlmh->nlmsg_type == RTM_NEWADDR)
 116             {
 117               struct ifaddrmsg *ifam = (struct ifaddrmsg *) NLMSG_DATA (nlmh);
 118
 119               switch (ifam->ifa_family)
 120                 {
 121                 case AF_INET:
 122                   *seen_ipv4 = true;
 123                   break;
 124                 case AF_INET6:
 125                   *seen_ipv6 = true;
 126
 127                   if (ifam->ifa_flags & (IFA_F_DEPRECATED
 128                                          | IFA_F_TEMPORARY
 129                                          | IFA_F_HOMEADDRESS))
 130                     {
 131                       struct rtattr *rta = IFA_RTA (ifam);
 132                       size_t len = (nlmh->nlmsg_len
 133                                     - NLMSG_LENGTH (sizeof (*ifam)));
 134                       void *local = NULL;
 135                       void *address = NULL;
 136                       while (RTA_OK (rta, len))
 137                         {
 138                           switch (rta->rta_type)
 139                             {
 140                             case IFA_LOCAL:
 141                               local = RTA_DATA (rta);
 142                               break;
 143
 144                             case IFA_ADDRESS:
 145                               address = RTA_DATA (rta);
 146                               break;
 147                             }
 148
 149                           rta = RTA_NEXT (rta, len);
 150                         }
 151
 152                       struct in6ailist *newp = alloca (sizeof (*newp));
 153                       newp->info.flags = (((ifam->ifa_flags & IFA_F_DEPRECATED)
 154                                            ? in6ai_deprecated : 0)
 155                                           | ((ifam->ifa_flags
 156                                               & IFA_F_TEMPORARY)
 157                                              ? in6ai_temporary : 0)
 158                                           | ((ifam->ifa_flags
 159                                               & IFA_F_HOMEADDRESS)
 160                                              ? in6ai_homeaddress : 0));
 161                       memcpy (newp->info.addr, address ?: local,
 162                               sizeof (newp->info.addr));
 163                       newp->next = in6ailist;
 164                       in6ailist = newp;
 165                       ++in6ailistlen;
 166                     }
 167                   break;
 168                 default:
 169                   /* Ignore.  */
 170                   break;
 171                 }
 172             }
 173           else if (nlmh->nlmsg_type == NLMSG_DONE)
 174             /* We found the end, leave the loop.  */
 175             done = true;
 176         }
 177     }
 178   while (! done);
 179
 180   close_not_cancel_no_status (fd);
 181
 182   if (in6ailist != NULL)
 183     {
 184       *in6ai = malloc (in6ailistlen * sizeof (**in6ai));
 185       if (*in6ai == NULL)
 186         return -1;
 187
 188       *in6ailen = in6ailistlen;
 189
 190       do
 191         {
 192           (*in6ai)[--in6ailistlen] = in6ailist->info;
 193           in6ailist = in6ailist->next;
 194         }
 195       while (in6ailist != NULL);
 196     }
 197
 198   return 0;
 199 }
 200
 201
 202 /* We don't know if we have NETLINK support compiled in in our
 203    Kernel.  */
 204 #if __ASSUME_NETLINK_SUPPORT == 0
 205 /* Define in ifaddrs.h.  */
 206 extern int __no_netlink_support attribute_hidden;
 207 #else
 208 # define __no_netlink_support 0
 209 #endif
 210
 211
 212 void
 213 attribute_hidden
 214 __check_pf (bool *seen_ipv4, bool *seen_ipv6,
 215             struct in6addrinfo **in6ai, size_t *in6ailen)
 216 {
 217   *in6ai = NULL;
 218   *in6ailen = 0;
 219
 220   if (! __no_netlink_support)
 221     {
 222       int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 223
 224       struct sockaddr_nl nladdr;
 225       memset (&nladdr, '\0', sizeof (nladdr));
 226       nladdr.nl_family = AF_NETLINK;
 227
 228       socklen_t addr_len = sizeof (nladdr);
 229
 230       if (fd >= 0
 231           && __bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) == 0
 232           && __getsockname (fd, (struct sockaddr *) &nladdr, &addr_len) == 0
 233           && make_request (fd, nladdr.nl_pid, seen_ipv4, seen_ipv6,
 234                            in6ai, in6ailen) == 0)
 235         /* It worked.  */
 236         return;
 237
 238       if (fd >= 0)
 239         __close (fd);
 240
 241 #if __ASSUME_NETLINK_SUPPORT == 0
 242       /* Remember that there is no netlink support.  */
 243       __no_netlink_support = 1;
 244 #else
 245       /* We cannot determine what interfaces are available.  Be
 246          pessimistic.  */
 247       *seen_ipv4 = true;
 248       *seen_ipv6 = true;
 249 #endif
 250     }
 251
 252 #if __ASSUME_NETLINK_SUPPORT == 0
 253   /* No netlink.  Get the interface list via getifaddrs.  */
 254   struct ifaddrs *ifa = NULL;
 255   if (getifaddrs (&ifa) != 0)
 256     {
 257       /* We cannot determine what interfaces are available.  Be
 258          pessimistic.  */
 259       *seen_ipv4 = true;
 260       *seen_ipv6 = true;
 261       return;
 262     }
 263
 264   struct ifaddrs *runp;
 265   for (runp = ifa; runp != NULL; runp = runp->ifa_next)
 266     if (runp->ifa_addr->sa_family == PF_INET)
 267       *seen_ipv4 = true;
 268     else if (runp->ifa_addr->sa_family == PF_INET6)
 269       *seen_ipv6 = true;
 270
 271   (void) freeifaddrs (ifa);
 272 #endif
 273 }