diff options
Diffstat (limited to 'vendor/rustix/src/net/send_recv/msg.rs')
| -rw-r--r-- | vendor/rustix/src/net/send_recv/msg.rs | 751 |
1 files changed, 751 insertions, 0 deletions
diff --git a/vendor/rustix/src/net/send_recv/msg.rs b/vendor/rustix/src/net/send_recv/msg.rs new file mode 100644 index 000000000..916f2a3db --- /dev/null +++ b/vendor/rustix/src/net/send_recv/msg.rs @@ -0,0 +1,751 @@ +//! [`recvmsg`], [`sendmsg`], and related functions. + +#![allow(unsafe_code)] + +use crate::backend::{self, c}; +use crate::fd::{AsFd, BorrowedFd, OwnedFd}; +use crate::io::{self, IoSlice, IoSliceMut}; + +use core::iter::FusedIterator; +use core::marker::PhantomData; +use core::mem::{size_of, size_of_val, take}; +use core::{ptr, slice}; + +use super::{RecvFlags, SendFlags, SocketAddrAny, SocketAddrV4, SocketAddrV6}; + +/// Macro for defining the amount of space used by CMSGs. +#[macro_export] +macro_rules! cmsg_space { + // Base Rules + (ScmRights($len:expr)) => { + $crate::net::__cmsg_space( + $len * ::core::mem::size_of::<$crate::fd::BorrowedFd<'static>>(), + ) + }; + + // Combo Rules + (($($($x:tt)*),+)) => { + $( + cmsg_space!($($x)*) + + )+ + 0 + }; +} + +#[doc(hidden)] +pub fn __cmsg_space(len: usize) -> usize { + unsafe { c::CMSG_SPACE(len.try_into().expect("CMSG_SPACE size overflow")) as usize } +} + +/// Ancillary message for [`sendmsg`], [`sendmsg_v4`], [`sendmsg_v6`], +/// [`sendmsg_unix`], and [`sendmsg_any`]. +#[non_exhaustive] +pub enum SendAncillaryMessage<'slice, 'fd> { + /// Send file descriptors. + ScmRights(&'slice [BorrowedFd<'fd>]), +} + +impl SendAncillaryMessage<'_, '_> { + /// Get the maximum size of an ancillary message. + /// + /// This can be helpful in determining the size of the buffer you allocate. + pub fn size(&self) -> usize { + let total_bytes = match self { + Self::ScmRights(slice) => size_of_val(*slice), + }; + + unsafe { + c::CMSG_SPACE( + total_bytes + .try_into() + .expect("size too large for CMSG_SPACE"), + ) as usize + } + } +} + +/// Ancillary message for [`recvmsg`]. +#[non_exhaustive] +pub enum RecvAncillaryMessage<'a> { + /// Received file descriptors. + ScmRights(AncillaryIter<'a, OwnedFd>), +} + +/// Buffer for sending ancillary messages. +pub struct SendAncillaryBuffer<'buf, 'slice, 'fd> { + /// Raw byte buffer for messages. + buffer: &'buf mut [u8], + + /// The amount of the buffer that is used. + length: usize, + + /// Phantom data for lifetime of `&'slice [BorrowedFd<'fd>]`. + _phantom: PhantomData<&'slice [BorrowedFd<'fd>]>, +} + +impl<'buf> From<&'buf mut [u8]> for SendAncillaryBuffer<'buf, '_, '_> { + fn from(buffer: &'buf mut [u8]) -> Self { + Self::new(buffer) + } +} + +impl Default for SendAncillaryBuffer<'_, '_, '_> { + fn default() -> Self { + Self::new(&mut []) + } +} + +impl<'buf, 'slice, 'fd> SendAncillaryBuffer<'buf, 'slice, 'fd> { + /// Create a new, empty `SendAncillaryBuffer` from a raw byte buffer. + pub fn new(buffer: &'buf mut [u8]) -> Self { + Self { + buffer, + length: 0, + _phantom: PhantomData, + } + } + + /// Returns a pointer to the message data. + pub(crate) fn as_control_ptr(&mut self) -> *mut u8 { + if self.length > 0 { + self.buffer.as_mut_ptr() + } else { + ptr::null_mut() + } + } + + /// Returns the length of the message data. + pub(crate) fn control_len(&self) -> usize { + self.length + } + + /// Delete all messages from the buffer. + pub fn clear(&mut self) { + self.length = 0; + } + + /// Add an ancillary message to the buffer. + /// + /// Returns `true` if the message was added successfully. + pub fn push(&mut self, msg: SendAncillaryMessage<'slice, 'fd>) -> bool { + match msg { + SendAncillaryMessage::ScmRights(fds) => { + let fds_bytes = + unsafe { slice::from_raw_parts(fds.as_ptr().cast::<u8>(), size_of_val(fds)) }; + self.push_ancillary(fds_bytes, c::SOL_SOCKET as _, c::SCM_RIGHTS as _) + } + } + } + + /// Pushes an ancillary message to the buffer. + fn push_ancillary(&mut self, source: &[u8], cmsg_level: c::c_int, cmsg_type: c::c_int) -> bool { + macro_rules! leap { + ($e:expr) => {{ + match ($e) { + Some(x) => x, + None => return false, + } + }}; + } + + // Calculate the length of the message. + let source_len = leap!(u32::try_from(source.len()).ok()); + + // Calculate the new length of the buffer. + let additional_space = unsafe { c::CMSG_SPACE(source_len) }; + let new_length = leap!(self.length.checked_add(additional_space as usize)); + let buffer = leap!(self.buffer.get_mut(..new_length)); + + // Fill the new part of the buffer with zeroes. + buffer[self.length..new_length].fill(0); + self.length = new_length; + + // Get the last header in the buffer. + let last_header = leap!(messages::Messages::new(buffer).last()); + + // Set the header fields. + last_header.cmsg_len = unsafe { c::CMSG_LEN(source_len) } as _; + last_header.cmsg_level = cmsg_level; + last_header.cmsg_type = cmsg_type; + + // Get the pointer to the payload and copy the data. + unsafe { + let payload = c::CMSG_DATA(last_header); + ptr::copy_nonoverlapping(source.as_ptr(), payload, source_len as _); + } + + true + } +} + +impl<'slice, 'fd> Extend<SendAncillaryMessage<'slice, 'fd>> + for SendAncillaryBuffer<'_, 'slice, 'fd> +{ + fn extend<T: IntoIterator<Item = SendAncillaryMessage<'slice, 'fd>>>(&mut self, iter: T) { + // TODO: This could be optimized to add every message in one go. + iter.into_iter().all(|msg| self.push(msg)); + } +} + +/// Buffer for receiving ancillary messages. +pub struct RecvAncillaryBuffer<'buf> { + /// Raw byte buffer for messages. + buffer: &'buf mut [u8], + + /// The portion of the buffer we've read from already. + read: usize, + + /// The amount of the buffer that is used. + length: usize, +} + +impl<'buf> From<&'buf mut [u8]> for RecvAncillaryBuffer<'buf> { + fn from(buffer: &'buf mut [u8]) -> Self { + Self::new(buffer) + } +} + +impl Default for RecvAncillaryBuffer<'_> { + fn default() -> Self { + Self::new(&mut []) + } +} + +impl<'buf> RecvAncillaryBuffer<'buf> { + /// Create a new, empty `RecvAncillaryBuffer` from a raw byte buffer. + pub fn new(buffer: &'buf mut [u8]) -> Self { + Self { + buffer, + read: 0, + length: 0, + } + } + + /// Returns a pointer to the message data. + pub(crate) fn as_control_ptr(&mut self) -> *mut u8 { + self.buffer.as_mut_ptr() + } + + /// Returns the length of the message data. + pub(crate) fn control_len(&self) -> usize { + self.buffer.len() + } + + /// Set the length of the message data. + /// + /// # Safety + /// + /// The buffer must be filled with valid message data. + pub(crate) unsafe fn set_control_len(&mut self, len: usize) { + self.length = len; + self.read = 0; + } + + /// Delete all messages from the buffer. + pub(crate) fn clear(&mut self) { + self.drain().for_each(drop); + } + + /// Drain all messages from the buffer. + pub fn drain(&mut self) -> AncillaryDrain<'_> { + AncillaryDrain { + messages: messages::Messages::new(&mut self.buffer[self.read..][..self.length]), + read: &mut self.read, + length: &mut self.length, + } + } +} + +impl Drop for RecvAncillaryBuffer<'_> { + fn drop(&mut self) { + self.clear(); + } +} + +/// An iterator that drains messages from a `RecvAncillaryBuffer`. +pub struct AncillaryDrain<'buf> { + /// Inner iterator over messages. + messages: messages::Messages<'buf>, + + /// Increment the number of messages we've read. + read: &'buf mut usize, + + /// Decrement the total length. + length: &'buf mut usize, +} + +impl<'buf> AncillaryDrain<'buf> { + /// A closure that converts a message into a `RecvAncillaryMessage`. + fn cvt_msg( + read: &mut usize, + length: &mut usize, + msg: &c::cmsghdr, + ) -> Option<RecvAncillaryMessage<'buf>> { + unsafe { + // Advance the "read" pointer. + let msg_len = msg.cmsg_len as usize; + *read += msg_len; + *length -= msg_len; + + // Get a pointer to the payload. + let payload = c::CMSG_DATA(msg); + let payload_len = msg.cmsg_len as usize - c::CMSG_LEN(0) as usize; + + // Get a mutable slice of the payload. + let payload: &'buf mut [u8] = slice::from_raw_parts_mut(payload, payload_len); + + // Determine what type it is. + let (level, msg_type) = (msg.cmsg_level, msg.cmsg_type); + match (level as _, msg_type as _) { + (c::SOL_SOCKET, c::SCM_RIGHTS) => { + // Create an iterator that reads out the file descriptors. + let fds = AncillaryIter::new(payload); + + Some(RecvAncillaryMessage::ScmRights(fds)) + } + _ => None, + } + } + } +} + +impl<'buf> Iterator for AncillaryDrain<'buf> { + type Item = RecvAncillaryMessage<'buf>; + + fn next(&mut self) -> Option<Self::Item> { + let read = &mut self.read; + let length = &mut self.length; + self.messages.find_map(|ev| Self::cvt_msg(read, length, ev)) + } + + fn size_hint(&self) -> (usize, Option<usize>) { + let (_, max) = self.messages.size_hint(); + (0, max) + } + + fn fold<B, F>(self, init: B, f: F) -> B + where + Self: Sized, + F: FnMut(B, Self::Item) -> B, + { + let read = self.read; + let length = self.length; + self.messages + .filter_map(|ev| Self::cvt_msg(read, length, ev)) + .fold(init, f) + } + + fn count(self) -> usize { + let read = self.read; + let length = self.length; + self.messages + .filter_map(|ev| Self::cvt_msg(read, length, ev)) + .count() + } + + fn last(self) -> Option<Self::Item> + where + Self: Sized, + { + let read = self.read; + let length = self.length; + self.messages + .filter_map(|ev| Self::cvt_msg(read, length, ev)) + .last() + } + + fn collect<B: FromIterator<Self::Item>>(self) -> B + where + Self: Sized, + { + let read = self.read; + let length = self.length; + self.messages + .filter_map(|ev| Self::cvt_msg(read, length, ev)) + .collect() + } +} + +impl FusedIterator for AncillaryDrain<'_> {} + +/// `sendmsg(msghdr)`—Sends a message on a socket. +/// +/// # References +/// - [POSIX] +/// - [Linux] +/// - [Apple] +/// - [FreeBSD] +/// - [NetBSD] +/// - [OpenBSD] +/// - [DragonFly BSD] +/// - [illumos] +/// +/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/sendmsg.html +/// [Linux]: https://man7.org/linux/man-pages/man2/sendmsg.2.html +/// [Apple]: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/sendmsg.2.html +/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=sendmsg&sektion=2 +/// [NetBSD]: https://man.netbsd.org/sendmsg.2 +/// [OpenBSD]: https://man.openbsd.org/sendmsg.2 +/// [DragonFly BSD]: https://man.dragonflybsd.org/?command=sendmsg§ion=2 +/// [illumos]: https://illumos.org/man/3SOCKET/sendmsg +#[inline] +pub fn sendmsg( + socket: impl AsFd, + iov: &[IoSlice<'_>], + control: &mut SendAncillaryBuffer<'_, '_, '_>, + flags: SendFlags, +) -> io::Result<usize> { + backend::net::syscalls::sendmsg(socket.as_fd(), iov, control, flags) +} + +/// `sendmsg(msghdr)`—Sends a message on a socket to a specific IPv4 address. +/// +/// # References +/// - [POSIX] +/// - [Linux] +/// - [Apple] +/// - [FreeBSD] +/// - [NetBSD] +/// - [OpenBSD] +/// - [DragonFly BSD] +/// - [illumos] +/// +/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/sendmsg.html +/// [Linux]: https://man7.org/linux/man-pages/man2/sendmsg.2.html +/// [Apple]: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/sendmsg.2.html +/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=sendmsg&sektion=2 +/// [NetBSD]: https://man.netbsd.org/sendmsg.2 +/// [OpenBSD]: https://man.openbsd.org/sendmsg.2 +/// [DragonFly BSD]: https://man.dragonflybsd.org/?command=sendmsg§ion=2 +/// [illumos]: https://illumos.org/man/3SOCKET/sendmsg +#[inline] +pub fn sendmsg_v4( + socket: impl AsFd, + addr: &SocketAddrV4, + iov: &[IoSlice<'_>], + control: &mut SendAncillaryBuffer<'_, '_, '_>, + flags: SendFlags, +) -> io::Result<usize> { + backend::net::syscalls::sendmsg_v4(socket.as_fd(), addr, iov, control, flags) +} + +/// `sendmsg(msghdr)`—Sends a message on a socket to a specific IPv6 address. +/// +/// # References +/// - [POSIX] +/// - [Linux] +/// - [Apple] +/// - [FreeBSD] +/// - [NetBSD] +/// - [OpenBSD] +/// - [DragonFly BSD] +/// - [illumos] +/// +/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/sendmsg.html +/// [Linux]: https://man7.org/linux/man-pages/man2/sendmsg.2.html +/// [Apple]: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/sendmsg.2.html +/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=sendmsg&sektion=2 +/// [NetBSD]: https://man.netbsd.org/sendmsg.2 +/// [OpenBSD]: https://man.openbsd.org/sendmsg.2 +/// [DragonFly BSD]: https://man.dragonflybsd.org/?command=sendmsg§ion=2 +/// [illumos]: https://illumos.org/man/3SOCKET/sendmsg +#[inline] +pub fn sendmsg_v6( + socket: impl AsFd, + addr: &SocketAddrV6, + iov: &[IoSlice<'_>], + control: &mut SendAncillaryBuffer<'_, '_, '_>, + flags: SendFlags, +) -> io::Result<usize> { + backend::net::syscalls::sendmsg_v6(socket.as_fd(), addr, iov, control, flags) +} + +/// `sendmsg(msghdr)`—Sends a message on a socket to a specific Unix-domain +/// address. +/// +/// # References +/// - [POSIX] +/// - [Linux] +/// - [Apple] +/// - [FreeBSD] +/// - [NetBSD] +/// - [OpenBSD] +/// - [DragonFly BSD] +/// - [illumos] +/// +/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/sendmsg.html +/// [Linux]: https://man7.org/linux/man-pages/man2/sendmsg.2.html +/// [Apple]: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/sendmsg.2.html +/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=sendmsg&sektion=2 +/// [NetBSD]: https://man.netbsd.org/sendmsg.2 +/// [OpenBSD]: https://man.openbsd.org/sendmsg.2 +/// [DragonFly BSD]: https://man.dragonflybsd.org/?command=sendmsg§ion=2 +/// [illumos]: https://illumos.org/man/3SOCKET/sendmsg +#[inline] +#[cfg(unix)] +pub fn sendmsg_unix( + socket: impl AsFd, + addr: &super::SocketAddrUnix, + iov: &[IoSlice<'_>], + control: &mut SendAncillaryBuffer<'_, '_, '_>, + flags: SendFlags, +) -> io::Result<usize> { + backend::net::syscalls::sendmsg_unix(socket.as_fd(), addr, iov, control, flags) +} + +/// `sendmsg(msghdr)`—Sends a message on a socket to a specific address. +/// +/// # References +/// - [POSIX] +/// - [Linux] +/// - [Apple] +/// - [FreeBSD] +/// - [NetBSD] +/// - [OpenBSD] +/// - [DragonFly BSD] +/// - [illumos] +/// +/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/sendmsg.html +/// [Linux]: https://man7.org/linux/man-pages/man2/sendmsg.2.html +/// [Apple]: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/sendmsg.2.html +/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=sendmsg&sektion=2 +/// [NetBSD]: https://man.netbsd.org/sendmsg.2 +/// [OpenBSD]: https://man.openbsd.org/sendmsg.2 +/// [DragonFly BSD]: https://man.dragonflybsd.org/?command=sendmsg§ion=2 +/// [illumos]: https://illumos.org/man/3SOCKET/sendmsg +#[inline] +pub fn sendmsg_any( + socket: impl AsFd, + addr: Option<&SocketAddrAny>, + iov: &[IoSlice<'_>], + control: &mut SendAncillaryBuffer<'_, '_, '_>, + flags: SendFlags, +) -> io::Result<usize> { + match addr { + None => backend::net::syscalls::sendmsg(socket.as_fd(), iov, control, flags), + Some(SocketAddrAny::V4(addr)) => { + backend::net::syscalls::sendmsg_v4(socket.as_fd(), addr, iov, control, flags) + } + Some(SocketAddrAny::V6(addr)) => { + backend::net::syscalls::sendmsg_v6(socket.as_fd(), addr, iov, control, flags) + } + #[cfg(unix)] + Some(SocketAddrAny::Unix(addr)) => { + backend::net::syscalls::sendmsg_unix(socket.as_fd(), addr, iov, control, flags) + } + } +} + +/// `recvmsg(msghdr)`—Receives a message from a socket. +/// +/// # References +/// - [POSIX] +/// - [Linux] +/// - [Apple] +/// - [FreeBSD] +/// - [NetBSD] +/// - [OpenBSD] +/// - [DragonFly BSD] +/// - [illumos] +/// +/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/recvmsg.html +/// [Linux]: https://man7.org/linux/man-pages/man2/recvmsg.2.html +/// [Apple]: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/recvmsg.2.html +/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=recvmsg&sektion=2 +/// [NetBSD]: https://man.netbsd.org/recvmsg.2 +/// [OpenBSD]: https://man.openbsd.org/recvmsg.2 +/// [DragonFly BSD]: https://man.dragonflybsd.org/?command=recvmsg§ion=2 +/// [illumos]: https://illumos.org/man/3SOCKET/recvmsg +#[inline] +pub fn recvmsg( + socket: impl AsFd, + iov: &mut [IoSliceMut<'_>], + control: &mut RecvAncillaryBuffer<'_>, + flags: RecvFlags, +) -> io::Result<RecvMsgReturn> { + backend::net::syscalls::recvmsg(socket.as_fd(), iov, control, flags) +} + +/// The result of a successful [`recvmsg`] call. +pub struct RecvMsgReturn { + /// The number of bytes received. + pub bytes: usize, + + /// The flags received. + pub flags: RecvFlags, + + /// The address of the socket we received from, if any. + pub address: Option<SocketAddrAny>, +} + +/// An iterator over data in an ancillary buffer. +pub struct AncillaryIter<'data, T> { + /// The data we're iterating over. + data: &'data mut [u8], + + /// The raw data we're removing. + _marker: PhantomData<T>, +} + +impl<'data, T> AncillaryIter<'data, T> { + /// Create a new iterator over data in an ancillary buffer. + /// + /// # Safety + /// + /// The buffer must contain valid ancillary data. + unsafe fn new(data: &'data mut [u8]) -> Self { + assert_eq!(data.len() % size_of::<T>(), 0); + + Self { + data, + _marker: PhantomData, + } + } +} + +impl<'data, T> Drop for AncillaryIter<'data, T> { + fn drop(&mut self) { + self.for_each(drop); + } +} + +impl<T> Iterator for AncillaryIter<'_, T> { + type Item = T; + + fn next(&mut self) -> Option<Self::Item> { + // See if there is a next item. + if self.data.len() < size_of::<T>() { + return None; + } + + // Get the next item. + let item = unsafe { self.data.as_ptr().cast::<T>().read_unaligned() }; + + // Move forward. + let data = take(&mut self.data); + self.data = &mut data[size_of::<T>()..]; + + Some(item) + } + + fn size_hint(&self) -> (usize, Option<usize>) { + let len = self.len(); + (len, Some(len)) + } + + fn count(self) -> usize { + self.len() + } + + fn last(mut self) -> Option<Self::Item> { + self.next_back() + } +} + +impl<T> FusedIterator for AncillaryIter<'_, T> {} + +impl<T> ExactSizeIterator for AncillaryIter<'_, T> { + fn len(&self) -> usize { + self.data.len() / size_of::<T>() + } +} + +impl<T> DoubleEndedIterator for AncillaryIter<'_, T> { + fn next_back(&mut self) -> Option<Self::Item> { + // See if there is a next item. + if self.data.len() < size_of::<T>() { + return None; + } + + // Get the next item. + let item = unsafe { + let ptr = self.data.as_ptr().add(self.data.len() - size_of::<T>()); + ptr.cast::<T>().read_unaligned() + }; + + // Move forward. + let len = self.data.len(); + let data = take(&mut self.data); + self.data = &mut data[..len - size_of::<T>()]; + + Some(item) + } +} + +mod messages { + use crate::backend::c; + use core::iter::FusedIterator; + use core::marker::PhantomData; + use core::mem::zeroed; + use core::ptr::NonNull; + + /// An iterator over the messages in an ancillary buffer. + pub(super) struct Messages<'buf> { + /// The message header we're using to iterator over the messages. + msghdr: c::msghdr, + + /// The current pointer to the next message header to return. + /// + /// This has a lifetime of `'buf`. + header: Option<NonNull<c::cmsghdr>>, + + /// Capture the original lifetime of the buffer. + _buffer: PhantomData<&'buf mut [u8]>, + } + + impl<'buf> Messages<'buf> { + /// Create a new iterator over messages from a byte buffer. + pub(super) fn new(buf: &'buf mut [u8]) -> Self { + let msghdr = { + let mut h: c::msghdr = unsafe { zeroed() }; + h.msg_control = buf.as_mut_ptr().cast(); + h.msg_controllen = buf.len().try_into().expect("buffer too large for msghdr"); + h + }; + + // Get the first header. + let header = NonNull::new(unsafe { c::CMSG_FIRSTHDR(&msghdr) }); + + Self { + msghdr, + header, + _buffer: PhantomData, + } + } + } + + impl<'a> Iterator for Messages<'a> { + type Item = &'a mut c::cmsghdr; + + #[inline] + fn next(&mut self) -> Option<Self::Item> { + // Get the current header. + let header = self.header?; + + // Get the next header. + self.header = NonNull::new(unsafe { c::CMSG_NXTHDR(&self.msghdr, header.as_ptr()) }); + + // If the headers are equal, we're done. + if Some(header) == self.header { + self.header = None; + } + + // SAFETY: The lifetime of `header` is tied to this. + Some(unsafe { &mut *header.as_ptr() }) + } + + fn size_hint(&self) -> (usize, Option<usize>) { + if self.header.is_some() { + // The remaining buffer *could* be filled with zero-length + // messages. + let max_size = unsafe { c::CMSG_LEN(0) } as usize; + let remaining_count = self.msghdr.msg_controllen as usize / max_size; + (1, Some(remaining_count)) + } else { + (0, Some(0)) + } + } + } + + impl FusedIterator for Messages<'_> {} +} |