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/* Return point to next ancillary data entry in message header.
Copyright (C) 1997-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <stddef.h>
#include <sys/socket.h>
struct cmsghdr *
__cmsg_nxthdr (struct msghdr *mhdr, struct cmsghdr *cmsg)
{
/* We may safely assume that cmsg lies between mhdr->msg_control and
mhdr->msg_controllen because the user is required to obtain the first
cmsg via CMSG_FIRSTHDR, set its length, then obtain subsequent cmsgs
via CMSG_NXTHDR, setting lengths along the way. However, we don't yet
trust the value of cmsg->cmsg_len and therefore do not use it in any
pointer arithmetic until we check its value. */
unsigned char * msg_control_ptr = (unsigned char *) mhdr->msg_control;
unsigned char * cmsg_ptr = (unsigned char *) cmsg;
size_t size_needed = sizeof (struct cmsghdr)
+ __CMSG_PADDING (cmsg->cmsg_len);
/* The current header is malformed, too small to be a full header. */
if ((size_t) cmsg->cmsg_len < sizeof (struct cmsghdr))
return (struct cmsghdr *) 0;
/* There isn't enough space between cmsg and the end of the buffer to
hold the current cmsg *and* the next one. */
if (((size_t)
(msg_control_ptr + mhdr->msg_controllen - cmsg_ptr)
< size_needed)
|| ((size_t)
(msg_control_ptr + mhdr->msg_controllen - cmsg_ptr
- size_needed)
< cmsg->cmsg_len))
return (struct cmsghdr *) 0;
/* Now, we trust cmsg_len and can use it to find the next header. */
cmsg = (struct cmsghdr *) ((unsigned char *) cmsg
+ CMSG_ALIGN (cmsg->cmsg_len));
return cmsg;
}
libc_hidden_def (__cmsg_nxthdr)
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