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//! Utilities for dealing with message headers.
//!
//! These take closures rather than returning a `c::msghdr` directly because
//! the message headers may reference stack-local data.
use crate::backend::c;
use crate::backend::conv::{msg_control_len, msg_iov_len};
#[cfg(target_os = "linux")]
use crate::backend::net::write_sockaddr::encode_sockaddr_xdp;
use crate::backend::net::write_sockaddr::{encode_sockaddr_v4, encode_sockaddr_v6};
use crate::io::{self, IoSlice, IoSliceMut};
#[cfg(target_os = "linux")]
use crate::net::xdp::SocketAddrXdp;
use crate::net::{RecvAncillaryBuffer, SendAncillaryBuffer, SocketAddrV4, SocketAddrV6};
use crate::utils::as_ptr;
use core::mem::{size_of, zeroed, MaybeUninit};
/// Create a message header intended to receive a datagram.
pub(crate) fn with_recv_msghdr<R>(
name: &mut MaybeUninit<c::sockaddr_storage>,
iov: &mut [IoSliceMut<'_>],
control: &mut RecvAncillaryBuffer<'_>,
f: impl FnOnce(&mut c::msghdr) -> io::Result<R>,
) -> io::Result<R> {
control.clear();
let namelen = size_of::<c::sockaddr_storage>() as c::socklen_t;
let mut msghdr = {
let mut h = zero_msghdr();
h.msg_name = name.as_mut_ptr().cast();
h.msg_namelen = namelen;
h.msg_iov = iov.as_mut_ptr().cast();
h.msg_iovlen = msg_iov_len(iov.len());
h.msg_control = control.as_control_ptr().cast();
h.msg_controllen = msg_control_len(control.control_len());
h
};
let res = f(&mut msghdr);
// Reset the control length.
if res.is_ok() {
unsafe {
control.set_control_len(msghdr.msg_controllen.try_into().unwrap_or(usize::MAX));
}
}
res
}
/// Create a message header intended to send without an address.
pub(crate) fn with_noaddr_msghdr<R>(
iov: &[IoSlice<'_>],
control: &mut SendAncillaryBuffer<'_, '_, '_>,
f: impl FnOnce(c::msghdr) -> R,
) -> R {
f({
let mut h = zero_msghdr();
h.msg_iov = iov.as_ptr() as _;
h.msg_iovlen = msg_iov_len(iov.len());
h.msg_control = control.as_control_ptr().cast();
h.msg_controllen = msg_control_len(control.control_len());
h
})
}
/// Create a message header intended to send with an IPv4 address.
pub(crate) fn with_v4_msghdr<R>(
addr: &SocketAddrV4,
iov: &[IoSlice<'_>],
control: &mut SendAncillaryBuffer<'_, '_, '_>,
f: impl FnOnce(c::msghdr) -> R,
) -> R {
let encoded = encode_sockaddr_v4(addr);
f({
let mut h = zero_msghdr();
h.msg_name = as_ptr(&encoded) as _;
h.msg_namelen = size_of::<SocketAddrV4>() as _;
h.msg_iov = iov.as_ptr() as _;
h.msg_iovlen = msg_iov_len(iov.len());
h.msg_control = control.as_control_ptr().cast();
h.msg_controllen = msg_control_len(control.control_len());
h
})
}
/// Create a message header intended to send with an IPv6 address.
pub(crate) fn with_v6_msghdr<R>(
addr: &SocketAddrV6,
iov: &[IoSlice<'_>],
control: &mut SendAncillaryBuffer<'_, '_, '_>,
f: impl FnOnce(c::msghdr) -> R,
) -> R {
let encoded = encode_sockaddr_v6(addr);
f({
let mut h = zero_msghdr();
h.msg_name = as_ptr(&encoded) as _;
h.msg_namelen = size_of::<SocketAddrV6>() as _;
h.msg_iov = iov.as_ptr() as _;
h.msg_iovlen = msg_iov_len(iov.len());
h.msg_control = control.as_control_ptr().cast();
h.msg_controllen = msg_control_len(control.control_len());
h
})
}
/// Create a message header intended to send with a Unix address.
#[cfg(all(unix, not(target_os = "redox")))]
pub(crate) fn with_unix_msghdr<R>(
addr: &crate::net::SocketAddrUnix,
iov: &[IoSlice<'_>],
control: &mut SendAncillaryBuffer<'_, '_, '_>,
f: impl FnOnce(c::msghdr) -> R,
) -> R {
f({
let mut h = zero_msghdr();
h.msg_name = as_ptr(&addr.unix) as _;
h.msg_namelen = addr.addr_len();
h.msg_iov = iov.as_ptr() as _;
h.msg_iovlen = msg_iov_len(iov.len());
h.msg_control = control.as_control_ptr().cast();
h.msg_controllen = msg_control_len(control.control_len());
h
})
}
/// Create a message header intended to send with an IPv6 address.
#[cfg(target_os = "linux")]
pub(crate) fn with_xdp_msghdr<R>(
addr: &SocketAddrXdp,
iov: &[IoSlice<'_>],
control: &mut SendAncillaryBuffer<'_, '_, '_>,
f: impl FnOnce(c::msghdr) -> R,
) -> R {
let encoded = encode_sockaddr_xdp(addr);
f({
let mut h = zero_msghdr();
h.msg_name = as_ptr(&encoded) as _;
h.msg_namelen = size_of::<SocketAddrXdp>() as _;
h.msg_iov = iov.as_ptr() as _;
h.msg_iovlen = msg_iov_len(iov.len());
h.msg_control = control.as_control_ptr().cast();
h.msg_controllen = msg_control_len(control.control_len());
h
})
}
/// Create a zero-initialized message header struct value.
#[cfg(all(unix, not(target_os = "redox")))]
pub(crate) fn zero_msghdr() -> c::msghdr {
// SAFETY: We can't initialize all the fields by value because on some
// platforms the `msghdr` struct in the libc crate contains private padding
// fields. But it is still a C type that's meant to be zero-initializable.
unsafe { zeroed() }
}