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 <asm/types.h>
  31 #include <linux/netlink.h>
  32 #include <linux/rtnetlink.h>
  33
  34 #include <not-cancel.h>
  35 #include <kernel-features.h>
  36
  37
  38 #ifndef IFA_F_TEMPORARY
  39 # define IFA_F_TEMPORARY IFA_F_SECONDARY
  40 #endif
  41 #ifndef IFA_F_HOMEADDRESS
  42 # define IFA_F_HOMEADDRESS 0
  43 #endif
  44
  45
  46 static int
  47 make_request (int fd, pid_t pid, bool *seen_ipv4, bool *seen_ipv6,
  48               struct in6addrinfo **in6ai, size_t *in6ailen)
  49 {
  50   struct req
  51   {
  52     struct nlmsghdr nlh;
  53     struct rtgenmsg g;
  54     /* struct rtgenmsg consists of a single byte.  This means there
  55        are three bytes of padding included in the REQ definition.
  56        We make them explicit here.  */
  57     char pad[3];
  58   } req;
  59   struct sockaddr_nl nladdr;
  60
  61   req.nlh.nlmsg_len = sizeof (req);
  62   req.nlh.nlmsg_type = RTM_GETADDR;
  63   req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
  64   req.nlh.nlmsg_pid = 0;
  65   req.nlh.nlmsg_seq = time (NULL);
  66   req.g.rtgen_family = AF_UNSPEC;
  67
  68   assert (sizeof (req) - offsetof (struct req, pad) == 3);
  69   memset (req.pad, '\0', sizeof (req.pad));
  70
  71   memset (&nladdr, '\0', sizeof (nladdr));
  72   nladdr.nl_family = AF_NETLINK;
  73
  74   if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
  75                                     (struct sockaddr *) &nladdr,
  76                                     sizeof (nladdr))) < 0)
  77     return -1;
  78
  79   *seen_ipv4 = false;
  80   *seen_ipv6 = false;
  81
  82   bool done = false;
  83   char buf[4096];
  84   struct iovec iov = { buf, sizeof (buf) };
  85   struct in6ailist
  86   {
  87     struct in6addrinfo info;
  88     struct in6ailist *next;
  89   } *in6ailist = NULL;
  90   size_t in6ailistlen = 0;
  91
  92   do
  93     {
  94       struct msghdr msg =
  95         {
  96           (void *) &nladdr, sizeof (nladdr),
  97           &iov, 1,
  98           NULL, 0,
  99           0
 100         };
 101
 102       ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
 103       if (read_len < 0)
 104         return -1;
 105
 106       if (msg.msg_flags & MSG_TRUNC)
 107         return -1;
 108
 109       struct nlmsghdr *nlmh;
 110       for (nlmh = (struct nlmsghdr *) buf;
 111            NLMSG_OK (nlmh, (size_t) read_len);
 112            nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
 113         {
 114           if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
 115               || nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
 116             continue;
 117
 118           if (nlmh->nlmsg_type == RTM_NEWADDR)
 119             {
 120               struct ifaddrmsg *ifam = (struct ifaddrmsg *) NLMSG_DATA (nlmh);
 121
 122               switch (ifam->ifa_family)
 123                 {
 124                 case AF_INET:
 125                   *seen_ipv4 = true;
 126                   break;
 127                 case AF_INET6:
 128                   *seen_ipv6 = true;
 129
 130                   if (ifam->ifa_flags & (IFA_F_DEPRECATED
 131                                          | IFA_F_TEMPORARY
 132                                          | IFA_F_HOMEADDRESS))
 133                     {
 134                       struct rtattr *rta = IFA_RTA (ifam);
 135                       size_t len = (nlmh->nlmsg_len
 136                                     - NLMSG_LENGTH (sizeof (*ifam)));
 137                       void *local = NULL;
 138                       void *address = NULL;
 139                       while (RTA_OK (rta, len))
 140                         {
 141                           switch (rta->rta_type)
 142                             {
 143                             case IFA_LOCAL:
 144                               local = RTA_DATA (rta);
 145                               break;
 146
 147                             case IFA_ADDRESS:
 148                               address = RTA_DATA (rta);
 149                               break;
 150                             }
 151
 152                           rta = RTA_NEXT (rta, len);
 153                         }
 154
 155                       struct in6ailist *newp = alloca (sizeof (*newp));
 156                       newp->info.flags = (((ifam->ifa_flags & IFA_F_DEPRECATED)
 157                                            ? in6ai_deprecated : 0)
 158                                           | ((ifam->ifa_flags
 159                                               & IFA_F_TEMPORARY)
 160                                              ? in6ai_temporary : 0)
 161                                           | ((ifam->ifa_flags
 162                                               & IFA_F_HOMEADDRESS)
 163                                              ? in6ai_homeaddress : 0));
 164                       memcpy (newp->info.addr, address ?: local,
 165                               sizeof (newp->info.addr));
 166                       newp->next = in6ailist;
 167                       in6ailist = newp;
 168                       ++in6ailistlen;
 169                     }
 170                   break;
 171                 default:
 172                   /* Ignore.  */
 173                   break;
 174                 }
 175             }
 176           else if (nlmh->nlmsg_type == NLMSG_DONE)
 177             /* We found the end, leave the loop.  */
 178             done = true;
 179         }
 180     }
 181   while (! done);
 182
 183   close_not_cancel_no_status (fd);
 184
 185   if (in6ailist != NULL)
 186     {
 187       *in6ai = malloc (in6ailistlen * sizeof (**in6ai));
 188       if (*in6ai == NULL)
 189         return -1;
 190
 191       *in6ailen = in6ailistlen;
 192
 193       do
 194         {
 195           (*in6ai)[--in6ailistlen] = in6ailist->info;
 196           in6ailist = in6ailist->next;
 197         }
 198       while (in6ailist != NULL);
 199     }
 200
 201   return 0;
 202 }
 203
 204
 205 /* We don't know if we have NETLINK support compiled in in our
 206    Kernel.  */
 207 #if __ASSUME_NETLINK_SUPPORT == 0
 208 /* Define in ifaddrs.h.  */
 209 extern int __no_netlink_support attribute_hidden;
 210 #else
 211 # define __no_netlink_support 0
 212 #endif
 213
 214
 215 void
 216 attribute_hidden
 217 __check_pf (bool *seen_ipv4, bool *seen_ipv6,
 218             struct in6addrinfo **in6ai, size_t *in6ailen)
 219 {
 220   *in6ai = NULL;
 221   *in6ailen = 0;
 222
 223   if (! __no_netlink_support)
 224     {
 225       int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 226
 227       struct sockaddr_nl nladdr;
 228       memset (&nladdr, '\0', sizeof (nladdr));
 229       nladdr.nl_family = AF_NETLINK;
 230
 231       socklen_t addr_len = sizeof (nladdr);
 232
 233       if (fd >= 0
 234           && __bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) == 0
 235           && __getsockname (fd, (struct sockaddr *) &nladdr, &addr_len) == 0
 236           && make_request (fd, nladdr.nl_pid, seen_ipv4, seen_ipv6,
 237                            in6ai, in6ailen) == 0)
 238         /* It worked.  */
 239         return;
 240
 241       if (fd >= 0)
 242         __close (fd);
 243
 244 #if __ASSUME_NETLINK_SUPPORT == 0
 245       /* Remember that there is no netlink support.  */
 246       __no_netlink_support = 1;
 247 #else
 248       /* We cannot determine what interfaces are available.  Be
 249          pessimistic.  */
 250       *seen_ipv4 = true;
 251       *seen_ipv6 = true;
 252 #endif
 253     }
 254
 255 #if __ASSUME_NETLINK_SUPPORT == 0
 256   /* No netlink.  Get the interface list via getifaddrs.  */
 257   struct ifaddrs *ifa = NULL;
 258   if (getifaddrs (&ifa) != 0)
 259     {
 260       /* We cannot determine what interfaces are available.  Be
 261          pessimistic.  */
 262       *seen_ipv4 = true;
 263       *seen_ipv6 = true;
 264       return;
 265     }
 266
 267   struct ifaddrs *runp;
 268   for (runp = ifa; runp != NULL; runp = runp->ifa_next)
 269     if (runp->ifa_addr->sa_family == PF_INET)
 270       *seen_ipv4 = true;
 271     else if (runp->ifa_addr->sa_family == PF_INET6)
 272       *seen_ipv6 = true;
 273
 274   (void) freeifaddrs (ifa);
 275 #endif
 276 }