sysdeps/unix/sysv/linux/netlink_assert_response.c

   1 /* Check recvmsg results for netlink sockets.
   2    Copyright (C) 2015-2024 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, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <stdio.h>
  22 #include <stdbool.h>
  23 #include <sys/socket.h>
  24
  25 #include "netlinkaccess.h"
  26
  27 static int
  28 get_address_family (int fd)
  29 {
  30   struct sockaddr_storage sa;
  31   socklen_t sa_len = sizeof (sa);
  32   if (__getsockname (fd, (struct sockaddr *) &sa, &sa_len) < 0)
  33     return -1;
  34   /* Check that the socket family number is preserved despite in-band
  35      signaling.  */
  36   _Static_assert (sizeof (sa.ss_family) < sizeof (int), "address family size");
  37   _Static_assert (0 < (__typeof__ (sa.ss_family)) -1,
  38                   "address family unsigned");
  39   return sa.ss_family;
  40 }
  41
  42 void
  43 __netlink_assert_response (int fd, ssize_t result)
  44 {
  45   if (result < 0)
  46     {
  47       /* Check if the error is unexpected.  */
  48       bool terminate = false;
  49       int error_code = errno;
  50       int family = get_address_family (fd);
  51       if (family != AF_NETLINK)
  52         /* If the address family does not match (or getsockname
  53            failed), report the original error.  */
  54         terminate = true;
  55       else if (error_code == EBADF
  56           || error_code == ENOTCONN
  57           || error_code == ENOTSOCK
  58           || error_code == ECONNREFUSED)
  59         /* These errors indicate that the descriptor is not a
  60            connected socket.  */
  61         terminate = true;
  62       else if (error_code == EAGAIN || error_code == EWOULDBLOCK)
  63         {
  64           /* The kernel might return EAGAIN for other reasons than a
  65              non-blocking socket.  But if the socket is not blocking,
  66              it is not ours, so report the error.  */
  67           int mode = __fcntl (fd, F_GETFL, 0);
  68           if (mode < 0 || (mode & O_NONBLOCK) != 0)
  69             terminate = true;
  70         }
  71       if (terminate)
  72         {
  73           char message[200];
  74           if (family < 0)
  75             __snprintf (message, sizeof (message),
  76                         "Unexpected error %d on netlink descriptor %d.\n",
  77                         error_code, fd);
  78           else
  79             __snprintf (message, sizeof (message),
  80                         "Unexpected error %d on netlink descriptor %d"
  81                         " (address family %d).\n",
  82                         error_code, fd, family);
  83           __libc_fatal (message);
  84         }
  85       else
  86         /* Restore original errno value.  */
  87         __set_errno (error_code);
  88     }
  89   else if (result < sizeof (struct nlmsghdr))
  90     {
  91       char message[200];
  92       int family = get_address_family (fd);
  93       if (family < 0)
  94           __snprintf (message, sizeof (message),
  95                       "Unexpected netlink response of size %zd"
  96                       " on descriptor %d\n",
  97                       result, fd);
  98       else
  99           __snprintf (message, sizeof (message),
 100                       "Unexpected netlink response of size %zd"
 101                       " on descriptor %d (address family %d)\n",
 102                       result, fd, family);
 103       __libc_fatal (message);
 104     }
 105 }
 106 libc_hidden_def (__netlink_assert_response)