sysdeps/unix/sysv/linux/cmsg_nxthdr.c

   1 /* Return point to next ancillary data entry in message header.
   2    Copyright (C) 1997, 1998, 2001, 2008 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 <stddef.h>
  21 #include <sys/socket.h>
  22
  23
  24 struct cmsghdr *
  25 __cmsg_nxthdr (struct msghdr *mhdr, struct cmsghdr *cmsg)
  26 {
  27   if ((size_t) cmsg->cmsg_len < sizeof (struct cmsghdr))
  28     /* The kernel header does this so there may be a reason.  */
  29     return NULL;
  30
  31   cmsg = (struct cmsghdr *) ((unsigned char *) cmsg
  32                              + CMSG_ALIGN (cmsg->cmsg_len));
  33   if ((unsigned char *) (cmsg + 1) > ((unsigned char *) mhdr->msg_control
  34                                       + mhdr->msg_controllen)
  35       || ((unsigned char *) cmsg + CMSG_ALIGN (cmsg->cmsg_len)
  36           > ((unsigned char *) mhdr->msg_control + mhdr->msg_controllen)))
  37     /* No more entries.  */
  38     return NULL;
  39   return cmsg;
  40 }