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glibc  2.9
cmsg_nxthdr.c
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00001 /* Return point to next ancillary data entry in message header.
00002    Copyright (C) 1997, 1998, 2001, 2008 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <stddef.h>
00021 #include <sys/socket.h>
00022 
00023 
00024 struct cmsghdr *
00025 __cmsg_nxthdr (struct msghdr *mhdr, struct cmsghdr *cmsg)
00026 {
00027   if ((size_t) cmsg->cmsg_len < sizeof (struct cmsghdr))
00028     /* The kernel header does this so there may be a reason.  */
00029     return NULL;
00030 
00031   cmsg = (struct cmsghdr *) ((unsigned char *) cmsg
00032                           + CMSG_ALIGN (cmsg->cmsg_len));
00033   if ((unsigned char *) (cmsg + 1) > ((unsigned char *) mhdr->msg_control
00034                                   + mhdr->msg_controllen)
00035       || ((unsigned char *) cmsg + CMSG_ALIGN (cmsg->cmsg_len)
00036          > ((unsigned char *) mhdr->msg_control + mhdr->msg_controllen)))
00037     /* No more entries.  */
00038     return NULL;
00039   return cmsg;
00040 }