1 /* Return point to next ancillary data entry in message header.
2    Copyright (C) 1997-2022 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 <stddef.h>
20 #include <sys/socket.h>
21 
22 
23 struct cmsghdr *
__cmsg_nxthdr(struct msghdr * mhdr,struct cmsghdr * cmsg)24 __cmsg_nxthdr (struct msghdr *mhdr, struct cmsghdr *cmsg)
25 {
26   if ((size_t) cmsg->cmsg_len < sizeof (struct cmsghdr))
27     /* The kernel header does this so there may be a reason.  */
28     return NULL;
29 
30   cmsg = (struct cmsghdr *) ((unsigned char *) cmsg
31 			     + CMSG_ALIGN (cmsg->cmsg_len));
32   if ((unsigned char *) (cmsg + 1) > ((unsigned char *) mhdr->msg_control
33 				      + mhdr->msg_controllen)
34       || ((unsigned char *) cmsg + CMSG_ALIGN (cmsg->cmsg_len)
35 	  > ((unsigned char *) mhdr->msg_control + mhdr->msg_controllen)))
36     /* No more entries.  */
37     return NULL;
38   return cmsg;
39 }
40 libc_hidden_def (__cmsg_nxthdr)
41