sysdeps/unix/sysv/linux/check_pf.c

   1 /* Determine protocol families for which interfaces exist.  Linux version.
   2    Copyright (C) 2003 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 <errno.h>
  21 #include <ifaddrs.h>
  22 #include <netdb.h>
  23 #include <string.h>
  24 #include <time.h>
  25 #include <unistd.h>
  26 #include <sys/socket.h>
  27
  28 #include <asm/types.h>
  29 #include <linux/netlink.h>
  30 #include <linux/rtnetlink.h>
  31
  32 #include "kernel-features.h"
  33
  34
  35 static int
  36 make_request (int fd, pid_t pid, bool *seen_ipv4, bool *seen_ipv6)
  37 {
  38   struct
  39   {
  40     struct nlmsghdr nlh;
  41     struct rtgenmsg g;
  42   } req;
  43   struct sockaddr_nl nladdr;
  44
  45   req.nlh.nlmsg_len = sizeof (req);
  46   req.nlh.nlmsg_type = RTM_GETADDR;
  47   req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
  48   req.nlh.nlmsg_pid = 0;
  49   req.nlh.nlmsg_seq = time (NULL);
  50   req.g.rtgen_family = AF_UNSPEC;
  51
  52   memset (&nladdr, '\0', sizeof (nladdr));
  53   nladdr.nl_family = AF_NETLINK;
  54
  55   if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
  56                                     (struct sockaddr *) &nladdr,
  57                                     sizeof (nladdr))) < 0)
  58     return -1;
  59
  60   *seen_ipv4 = false;
  61   *seen_ipv6 = false;
  62
  63   bool done = false;
  64   char buf[4096];
  65   struct iovec iov = { buf, sizeof (buf) };
  66
  67   do
  68     {
  69       struct msghdr msg =
  70         {
  71           (void *) &nladdr, sizeof (nladdr),
  72           &iov, 1,
  73           NULL, 0,
  74           0
  75         };
  76
  77       ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
  78       if (read_len < 0)
  79         return -1;
  80
  81       if (msg.msg_flags & MSG_TRUNC)
  82         return -1;
  83
  84       struct nlmsghdr *nlmh;
  85       for (nlmh = (struct nlmsghdr *) buf;
  86            NLMSG_OK (nlmh, (size_t) read_len);
  87            nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
  88         {
  89           if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
  90               || nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
  91             continue;
  92
  93           if (nlmh->nlmsg_type == RTM_NEWADDR)
  94             {
  95               struct ifaddrmsg *ifam = (struct ifaddrmsg *) NLMSG_DATA (nlmh);
  96
  97               switch (ifam->ifa_family)
  98                 {
  99                 case AF_INET:
 100                   *seen_ipv4 = true;
 101                   break;
 102                 case AF_INET6:
 103                   *seen_ipv6 = true;
 104                   break;
 105                 default:
 106                   /* Ignore.  */
 107                   break;
 108                 }
 109             }
 110           else if (nlmh->nlmsg_type == NLMSG_DONE)
 111             /* We found the end, leave the loop.  */
 112             done = true;
 113           else ;
 114         }
 115     }
 116   while (! done);
 117
 118   __close (fd);
 119
 120   return 0;
 121 }
 122
 123
 124 /* We don't know if we have NETLINK support compiled in in our
 125    Kernel.  */
 126 #if __ASSUME_NETLINK_SUPPORT == 0
 127 /* Define in ifaddrs.h.  */
 128 extern int __no_netlink_support attribute_hidden;
 129 #else
 130 # define __no_netlink_support 0
 131 #endif
 132
 133
 134 void
 135 attribute_hidden
 136 __check_pf (bool *seen_ipv4, bool *seen_ipv6)
 137 {
 138   if (! __no_netlink_support)
 139     {
 140       int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 141
 142       struct sockaddr_nl nladdr;
 143       memset (&nladdr, '\0', sizeof (nladdr));
 144       nladdr.nl_family = AF_NETLINK;
 145
 146       socklen_t addr_len = sizeof (nladdr);
 147
 148       if (fd >= 0
 149           && __bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) == 0
 150           && __getsockname (fd, (struct sockaddr *) &nladdr, &addr_len) == 0
 151           && make_request (fd, nladdr.nl_pid, seen_ipv4, seen_ipv6) == 0)
 152         /* It worked.  */
 153         return;
 154
 155       if (fd >= 0)
 156         __close (fd);
 157
 158 #if __ASSUME_NETLINK_SUPPORT == 0
 159       /* Remember that there is no netlink support.  */
 160       __no_netlink_support = 1;
 161 #else
 162       /* We cannot determine what interfaces are available.  Be
 163          pessimistic.  */
 164       *seen_ipv4 = true;
 165       *seen_ipv6 = true;
 166 #endif
 167     }
 168
 169 #if __ASSUME_NETLINK_SUPPORT == 0
 170   /* No netlink.  Get the interface list via getifaddrs.  */
 171   struct ifaddrs *ifa = NULL;
 172   if (getifaddrs (&ifa) != 0)
 173     {
 174       /* We cannot determine what interfaces are available.  Be
 175          pessimistic.  */
 176       *seen_ipv4 = true;
 177       *seen_ipv6 = true;
 178       return;
 179     }
 180
 181   *seen_ipv4 = false;
 182   *seen_ipv6 = false;
 183
 184   struct ifaddrs *runp;
 185   for (runp = ifa; runp != NULL; runp = runp->ifa_next)
 186     if (runp->ifa_addr->sa_family == PF_INET)
 187       *seen_ipv4 = true;
 188     else if (runp->ifa_addr->sa_family == PF_INET6)
 189       *seen_ipv6 = true;
 190
 191   (void) freeifaddrs (ifa);
 192 #endif
 193 }