WIP #68617: add UdpSocket::send_to_vectored()

library/std/Cargo.toml

@@ -56,6 +56,7 @@ backtrace = [
   'miniz_oxide/rustc-dep-of-std',
 ]
 gimli-symbolize = []
+udp_sendmsg = []
 
 panic-unwind = ["panic_unwind"]
 profiler = ["profiler_builtins"]

library/std/src/net/udp.rs

@@ -2,12 +2,13 @@
 mod tests;
 
 use crate::fmt;
-use crate::io::{self, ErrorKind};
+use crate::io::{self, ErrorKind, IoSliceMut};
 use crate::net::{Ipv4Addr, Ipv6Addr, SocketAddr, ToSocketAddrs};
 use crate::sys_common::net as net_imp;
 use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::time::Duration;
 
+
 /// A UDP socket.
 ///
 /// After creating a `UdpSocket` by [`bind`]ing it to a socket address, data can be
@@ -181,6 +182,20 @@ impl UdpSocket {
         }
     }
 
+    /// Sends data on the socket to the given address. On success, returns the
+    /// number of bytes written.
+    ///
+    ///
+    #[stable(feature = "udp_sendmsg", since = "1.70.0")]
+    pub fn send_to_vectored<A: ToSocketAddrs>(&self, bufs: &mut [IoSliceMut<'_>], addr: A) -> io::Result<usize> {
+        match addr.to_socket_addrs()?.next() {
+            Some(addr) => self.0.send_to_vectored(bufs, &addr),
+            None => {
+                Err(io::const_io_error!(ErrorKind::InvalidInput, "no addresses to send data to"))
+            }
+        }
+    }
+
     /// Returns the socket address of the remote peer this socket was connected to.
     ///
     /// # Examples
@@ -667,6 +682,9 @@ impl UdpSocket {
         self.0.send(buf)
     }
 
+    ///
+    ///
+
     /// Receives a single datagram message on the socket from the remote address to
     /// which it is connected. On success, returns the number of bytes read.
     ///

library/std/src/sys/unix/l4re.rs

@@ -399,6 +399,10 @@ pub mod net {
             unimpl!();
         }
 
+        // pub fn send_to_vectored(&self, _:  &mut [IoSliceMut<'_>], _: &SocketAddr) -> io::Result<usize> {
+        //     unimpl!();
+        // }
+
         pub fn duplicate(&self) -> io::Result<UdpSocket> {
             unimpl!();
         }

library/std/src/sys_common/net.rs

@@ -14,6 +14,10 @@ use crate::sys::net::{cvt, cvt_gai, cvt_r, init, wrlen_t, Socket};
 use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::time::Duration;
 
+use libc;
+
+type IovLen = usize;
+
 use crate::ffi::{c_int, c_void};
 
 cfg_if::cfg_if! {
@@ -553,6 +557,22 @@ impl UdpSocket {
         Ok(ret as usize)
     }
 
+    pub fn send_to_vectored(&self, bufs: &mut [IoSliceMut<'_>], dst: &SocketAddr) -> io::Result<usize> {
+        let (dst, dstlen) = dst.into_inner();
+        let mut msg: libc::msghdr = unsafe { mem::zeroed() };
+        // Safety: we're creating a `*mut` pointer from a reference, which is UB
+        // once actually used. However the OS should not write to it in the
+        // `sendmsg` system call.
+        msg.msg_name = dst.as_ptr() as *mut _;
+        msg.msg_namelen = dstlen;
+        // Safety: Same as above about `*const` -> `*mut`.
+        msg.msg_iov = bufs.as_ptr() as *mut _;
+        msg.msg_iovlen = cmp::min(bufs.len(), IovLen::MAX as usize) as IovLen;
+        // TODO(fr) set flags
+        let ret = self.inner.send_msg(&mut msg)?;
+        Ok(ret as usize)
+    }
+
     pub fn duplicate(&self) -> io::Result<UdpSocket> {
         self.inner.duplicate().map(|s| UdpSocket { inner: s })
     }