61 lines
2.3 KiB
C
61 lines
2.3 KiB
C
/* Return point to next ancillary data entry in message header.
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Copyright (C) 1997-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <stddef.h>
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#include <sys/socket.h>
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struct cmsghdr *
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__cmsg_nxthdr (struct msghdr *mhdr, struct cmsghdr *cmsg)
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{
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/* We may safely assume that cmsg lies between mhdr->msg_control and
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mhdr->msg_controllen because the user is required to obtain the first
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cmsg via CMSG_FIRSTHDR, set its length, then obtain subsequent cmsgs
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via CMSG_NXTHDR, setting lengths along the way. However, we don't yet
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trust the value of cmsg->cmsg_len and therefore do not use it in any
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pointer arithmetic until we check its value. */
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unsigned char * msg_control_ptr = (unsigned char *) mhdr->msg_control;
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unsigned char * cmsg_ptr = (unsigned char *) cmsg;
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size_t size_needed = sizeof (struct cmsghdr)
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+ __CMSG_PADDING (cmsg->cmsg_len);
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/* The current header is malformed, too small to be a full header. */
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if ((size_t) cmsg->cmsg_len < sizeof (struct cmsghdr))
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return (struct cmsghdr *) 0;
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/* There isn't enough space between cmsg and the end of the buffer to
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hold the current cmsg *and* the next one. */
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if (((size_t)
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(msg_control_ptr + mhdr->msg_controllen - cmsg_ptr)
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< size_needed)
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|| ((size_t)
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(msg_control_ptr + mhdr->msg_controllen - cmsg_ptr
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- size_needed)
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< cmsg->cmsg_len))
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return (struct cmsghdr *) 0;
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/* Now, we trust cmsg_len and can use it to find the next header. */
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cmsg = (struct cmsghdr *) ((unsigned char *) cmsg
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+ CMSG_ALIGN (cmsg->cmsg_len));
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return cmsg;
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}
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libc_hidden_def (__cmsg_nxthdr)
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