Merge #1145

1145: Fix sys::socket::recvfrom for TCP sockets r=asomers a=asomers

recvfrom(2) only returns the sender's address for protocols that provide
it.  Usually, that means it returns the sender's address for datagram
sockets but not for stream sockets.

Fixes #1144

Co-authored-by: Alan Somers <[email protected]>

Author: bors[bot]

CHANGELOG.md

@@ -19,6 +19,10 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   ([#1133](https://github.com/nix-rust/nix/pull/1133))
 
 ### Changed
+- `sys::socket::recvfrom` now returns
+  `Result<(usize, Option<SockAddr>)>` instead of `Result<(usize, SockAddr)>`.
+  ([#1145](https://github.com/nix-rust/nix/pull/1145))
+
 - `Signal::from_c_int` has been replaced by `Signal::try_from`
   ([#1113](https://github.com/nix-rust/nix/pull/1113))
 

src/sys/socket/mod.rs

@@ -1075,10 +1075,13 @@ pub fn recv(sockfd: RawFd, buf: &mut [u8], flags: MsgFlags) -> Result<usize> {
 }
 
 /// Receive data from a connectionless or connection-oriented socket. Returns
-/// the number of bytes read and the socket address of the sender.
+/// the number of bytes read and, for connectionless sockets,  the socket
+/// address of the sender.
 ///
 /// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/recvfrom.html)
-pub fn recvfrom(sockfd: RawFd, buf: &mut [u8]) -> Result<(usize, SockAddr)> {
+pub fn recvfrom(sockfd: RawFd, buf: &mut [u8])
+    -> Result<(usize, Option<SockAddr>)>
+{
     unsafe {
         let mut addr: sockaddr_storage = mem::zeroed();
         let mut len = mem::size_of::<sockaddr_storage>() as socklen_t;
@@ -1089,10 +1092,13 @@ pub fn recvfrom(sockfd: RawFd, buf: &mut [u8]) -> Result<(usize, SockAddr)> {
             buf.len() as size_t,
             0,
             &mut addr as *mut libc::sockaddr_storage as *mut libc::sockaddr,
-            &mut len as *mut socklen_t))?;
+            &mut len as *mut socklen_t))? as usize;
 
-        sockaddr_storage_to_addr(&addr, len as usize)
-            .map(|addr| (ret as usize, addr))
+        match sockaddr_storage_to_addr(&addr, len as usize) {
+            Err(Error::Sys(Errno::ENOTCONN)) => Ok((ret, None)),
+            Ok(addr) => Ok((ret, Some(addr))),
+            Err(e) => Err(e)
+        }
     }
 }
 

test/sys/test_socket.rs

@@ -161,6 +161,73 @@ pub fn test_socketpair() {
     assert_eq!(&buf[..], b"hello");
 }
 
+mod recvfrom {
+    use nix::Result;
+    use nix::sys::socket::*;
+    use std::thread;
+    use super::*;
+
+    const MSG: &'static [u8] = b"Hello, World!";
+
+    fn sendrecv<F>(rsock: RawFd, ssock: RawFd, f: F) -> Option<SockAddr>
+        where F: Fn(RawFd, &[u8], MsgFlags) -> Result<usize> + Send + 'static
+    {
+        let mut buf: [u8; 13] = [0u8; 13];
+        let mut l = 0;
+        let mut from = None;
+
+        let send_thread = thread::spawn(move || {
+            let mut l = 0;
+            while l < std::mem::size_of_val(MSG) {
+                l += f(ssock, &MSG[l..], MsgFlags::empty()).unwrap();
+            }
+        });
+
+        while l < std::mem::size_of_val(MSG) {
+            let (len, from_) = recvfrom(rsock, &mut buf[l..]).unwrap();
+            from = from_;
+            l += len;
+        }
+        assert_eq!(&buf, MSG);
+        send_thread.join().unwrap();
+        from
+    }
+
+    #[test]
+    pub fn stream() {
+        let (fd2, fd1) = socketpair(AddressFamily::Unix, SockType::Stream,
+                                    None, SockFlag::empty()).unwrap();
+        // Ignore from for stream sockets
+        let _ = sendrecv(fd1, fd2, |s, m, flags| {
+            send(s, m, flags)
+        });
+    }
+
+    #[test]
+    pub fn udp() {
+        let std_sa = SocketAddr::from_str("127.0.0.1:6789").unwrap();
+        let inet_addr = InetAddr::from_std(&std_sa);
+        let sock_addr = SockAddr::new_inet(inet_addr);
+        let rsock = socket(AddressFamily::Inet,
+            SockType::Datagram,
+            SockFlag::empty(),
+            None
+        ).unwrap();
+        bind(rsock, &sock_addr).unwrap();
+        let ssock = socket(
+            AddressFamily::Inet,
+            SockType::Datagram,
+            SockFlag::empty(),
+            None,
+        ).expect("send socket failed");
+        let from = sendrecv(rsock, ssock, move |s, m, flags| {
+            sendto(s, m, &sock_addr, flags)
+        });
+        // UDP sockets should set the from address
+        assert_eq!(AddressFamily::Inet, from.unwrap().family());
+    }
+}
+
 // Test error handling of our recvmsg wrapper
 #[test]
 pub fn test_recvmsg_ebadf() {