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| // Copyright (C) 2022, Cloudflare, Inc. | ||
| // All rights reserved. | ||
| // | ||
| // Redistribution and use in source and binary forms, with or without | ||
| // modification, are permitted provided that the following conditions are | ||
| // met: | ||
| // | ||
| // * Redistributions of source code must retain the above copyright notice, | ||
| // this list of conditions and the following disclaimer. | ||
| // | ||
| // * Redistributions in binary form must reproduce the above copyright | ||
| // notice, this list of conditions and the following disclaimer in the | ||
| // documentation and/or other materials provided with the distribution. | ||
| // | ||
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS | ||
| // IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, | ||
| // THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR | ||
| // PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR | ||
| // CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, | ||
| // EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, | ||
| // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR | ||
| // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | ||
| // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING | ||
| // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS | ||
| // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | ||
| // | ||
| // Taken from https://github.com/mxinden/udp-socket/blob/master/src/cmsg.rs, | ||
| // which is itself inspired from | ||
| // https://github.com/quinn-rs/quinn/blob/main/quinn-udp/src/cmsg.rs. | ||
|
|
||
| use std::mem; | ||
| use std::ptr; | ||
|
|
||
| #[derive(Copy, Clone)] | ||
| #[repr(align(8))] // Conservative bound for align_of<cmsghdr> | ||
| pub struct Aligned<T>(pub T); | ||
|
|
||
| /// Helper to encode a series of control messages ("cmsgs") to a buffer for use | ||
| /// in `sendmsg`. | ||
| /// | ||
| /// The operation must be "finished" for the msghdr to be usable, either by | ||
| /// calling `finish` explicitly or by dropping the `Encoder`. | ||
| pub struct Encoder<'a> { | ||
| hdr: &'a mut libc::msghdr, | ||
| cmsg: Option<&'a mut libc::cmsghdr>, | ||
| len: usize, | ||
| } | ||
|
|
||
| impl<'a> Encoder<'a> { | ||
| /// # Safety | ||
| /// - `hdr.msg_control` must be a suitably aligned pointer to | ||
| /// `hdr.msg_controllen` bytes that can be safely written | ||
| /// - The `Encoder` must be dropped before `hdr` is passed to a system call, | ||
| /// and must not be leaked. | ||
| pub unsafe fn new(hdr: &'a mut libc::msghdr) -> Self { | ||
| Self { | ||
| cmsg: libc::CMSG_FIRSTHDR(hdr).as_mut(), | ||
| hdr, | ||
| len: 0, | ||
| } | ||
| } | ||
|
|
||
| /// Append a control message to the buffer. | ||
| /// | ||
| /// # Panics | ||
| /// - If insufficient buffer space remains. | ||
| /// - If `T` has stricter alignment requirements than `cmsghdr` | ||
| pub fn push<T: Copy + ?Sized>( | ||
| &mut self, level: libc::c_int, ty: libc::c_int, value: T, | ||
| ) { | ||
| assert!(mem::align_of::<T>() <= mem::align_of::<libc::cmsghdr>()); | ||
| let space = | ||
| unsafe { libc::CMSG_SPACE(mem::size_of_val(&value) as _) as usize }; | ||
| assert!( | ||
| self.hdr.msg_controllen as usize >= self.len + space, | ||
| "control message buffer too small" | ||
| ); | ||
| let cmsg = self.cmsg.take().expect("no control buffer space remaining"); | ||
| cmsg.cmsg_level = level; | ||
| cmsg.cmsg_type = ty; | ||
| cmsg.cmsg_len = | ||
| unsafe { libc::CMSG_LEN(mem::size_of_val(&value) as _) } as _; | ||
| unsafe { | ||
| ptr::write(libc::CMSG_DATA(cmsg) as *const T as *mut T, value); | ||
| } | ||
| self.len += space; | ||
| self.cmsg = unsafe { libc::CMSG_NXTHDR(self.hdr, cmsg).as_mut() }; | ||
| } | ||
|
|
||
| /// Finishes appending control messages to the buffer | ||
| pub fn finish(self) { | ||
| // Delegates to the `Drop` impl | ||
| } | ||
| } | ||
|
|
||
| // Statically guarantees that the encoding operation is "finished" before the | ||
| // control buffer is read by `sendmsg`. | ||
| impl<'a> Drop for Encoder<'a> { | ||
| fn drop(&mut self) { | ||
| self.hdr.msg_controllen = self.len as _; | ||
| } | ||
| } | ||
|
|
||
| /// # Safety | ||
| /// | ||
| /// `cmsg` must refer to a cmsg containing a payload of type `T` | ||
| pub unsafe fn decode<T: Copy>(cmsg: &libc::cmsghdr) -> T { | ||
| assert!(mem::align_of::<T>() <= mem::align_of::<libc::cmsghdr>()); | ||
| debug_assert_eq!( | ||
| cmsg.cmsg_len as usize, | ||
| libc::CMSG_LEN(mem::size_of::<T>() as _) as usize | ||
| ); | ||
| ptr::read(libc::CMSG_DATA(cmsg) as *const T) | ||
| } | ||
|
|
||
| pub struct Iter<'a> { | ||
| hdr: &'a libc::msghdr, | ||
| cmsg: Option<&'a libc::cmsghdr>, | ||
| } | ||
|
|
||
| impl<'a> Iter<'a> { | ||
| /// # Safety | ||
| /// | ||
| /// `hdr.msg_control` must point to memory outliving `'a` which can be | ||
| /// soundly read for the lifetime of the constructed `Iter` and contains | ||
| /// a buffer of cmsgs, i.e. is aligned for `cmsghdr`, is fully | ||
| /// initialized, and has correct internal links. | ||
| pub unsafe fn new(hdr: &'a libc::msghdr) -> Self { | ||
| Self { | ||
| hdr, | ||
| cmsg: libc::CMSG_FIRSTHDR(hdr).as_ref(), | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl<'a> Iterator for Iter<'a> { | ||
| type Item = &'a libc::cmsghdr; | ||
|
|
||
| fn next(&mut self) -> Option<&'a libc::cmsghdr> { | ||
| let current = self.cmsg.take()?; | ||
| self.cmsg = unsafe { libc::CMSG_NXTHDR(self.hdr, current).as_ref() }; | ||
| Some(current) | ||
| } | ||
| } |
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