glibc/manual/examples/mkfsock.c

/* Example of Local-Namespace Sockets
   Copyright (C) 1991-2021 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation; either version 2
   of the License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, see <https://www.gnu.org/licenses/>.
*/

#include <stddef.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/un.h>

int
make_named_socket (const char *filename)
{
  struct sockaddr_un name;
  int sock;
  size_t size;

  /* Create the socket.  */
  sock = socket (PF_LOCAL, SOCK_DGRAM, 0);
  if (sock < 0)
    {
      perror ("socket");
      exit (EXIT_FAILURE);
    }

  /* Bind a name to the socket.  */
  name.sun_family = AF_LOCAL;
  strncpy (name.sun_path, filename, sizeof (name.sun_path));
  name.sun_path[sizeof (name.sun_path) - 1] = '\0';

  /* The size of the address is
     the offset of the start of the filename,
     plus its length (not including the terminating null byte).
     Alternatively you can just do:
     size = SUN_LEN (&name);
  */
  size = (offsetof (struct sockaddr_un, sun_path)
	  + strlen (name.sun_path));

  if (bind (sock, (struct sockaddr *) &name, size) < 0)
    {
      perror ("bind");
      exit (EXIT_FAILURE);
    }

  return sock;
}