Remove FFI types from the public API

src/sys/unix.rs

@@ -7,11 +7,6 @@
 // except according to those terms.
 
 use std::cmp::min;
-#[cfg(all(
-    feature = "all",
-    any(target_os = "android", target_os = "fuchsia", target_os = "linux")
-))]
-use std::ffi::{CStr, CString};
 #[cfg(not(target_os = "redox"))]
 use std::io::IoSlice;
 use std::marker::PhantomData;
@@ -942,10 +937,10 @@ impl crate::Socket {
         feature = "all",
         any(target_os = "android", target_os = "fuchsia", target_os = "linux")
     ))]
-    pub fn device(&self) -> io::Result<Option<CString>> {
+    pub fn device(&self) -> io::Result<Option<Vec<u8>>> {
         // TODO: replace with `MaybeUninit::uninit_array` once stable.
         let mut buf: [MaybeUninit<u8>; libc::IFNAMSIZ] =
-            unsafe { MaybeUninit::<[MaybeUninit<u8>; libc::IFNAMSIZ]>::uninit().assume_init() };
+            unsafe { MaybeUninit::uninit().assume_init() };
         let mut len = buf.len() as libc::socklen_t;
         unsafe {
             syscall!(getsockopt(
@@ -959,21 +954,9 @@ impl crate::Socket {
         if len == 0 {
             Ok(None)
         } else {
-            // Allocate a buffer for `CString` with the length including the
-            // null terminator.
-            let len = len as usize;
-            let mut name = Vec::with_capacity(len);
-
+            let buf = &buf[..len as usize - 1];
             // TODO: use `MaybeUninit::slice_assume_init_ref` once stable.
-            // Safety: `len` bytes are writen by the OS, this includes a null
-            // terminator. However we don't copy the null terminator because
-            // `CString::from_vec_unchecked` adds its own null terminator.
-            let buf = unsafe { slice::from_raw_parts(buf.as_ptr().cast(), len - 1) };
-            name.extend_from_slice(buf);
-
-            // Safety: the OS initialised the string for us, which shouldn't
-            // include any null bytes.
-            Ok(Some(unsafe { CString::from_vec_unchecked(name) }))
+            Ok(Some(unsafe { &*(buf as *const [_] as *const [u8]) }.into()))
         }
     }
 
@@ -990,9 +973,9 @@ impl crate::Socket {
         feature = "all",
         any(target_os = "android", target_os = "fuchsia", target_os = "linux")
     ))]
-    pub fn bind_device(&self, interface: Option<&CStr>) -> io::Result<()> {
+    pub fn bind_device(&self, interface: Option<&[u8]>) -> io::Result<()> {
         let (value, len) = if let Some(interface) = interface {
-            (interface.as_ptr(), interface.to_bytes_with_nul().len())
+            (interface.as_ptr(), interface.len())
         } else {
             (ptr::null(), 0)
         };

tests/socket.rs

@@ -1,5 +1,3 @@
-#[cfg(all(feature = "all", any(target_os = "fuchsia", target_os = "linux")))]
-use std::ffi::CStr;
 #[cfg(any(windows, target_vendor = "apple"))]
 use std::io;
 #[cfg(not(target_os = "redox"))]
@@ -631,30 +629,40 @@ fn tcp_keepalive() {
 
 #[cfg(all(feature = "all", any(target_os = "fuchsia", target_os = "linux")))]
 #[test]
+#[ignore = "setting `SO_BINDTODEVICE` requires the `CAP_NET_RAW` capability (works when running as root)"]
 fn device() {
     // Some common network interface on Linux.
-    const INTERFACES: &[&str] = &["lo\0", "lo0\0", "eth0\0", "wlan0\0"];
+    const INTERFACES: &[&str] = &["lo", "lo0", "eth0", "wlan0"];
 
     let socket = Socket::new(Domain::IPV4, Type::STREAM, None).unwrap();
     assert_eq!(socket.device().unwrap(), None);
 
     for interface in INTERFACES.iter() {
-        let interface = CStr::from_bytes_with_nul(interface.as_bytes()).unwrap();
-        if let Err(err) = socket.bind_device(Some(interface)) {
+        if let Err(err) = socket.bind_device(Some(interface.as_bytes())) {
             // Network interface is not available try another.
             if matches!(err.raw_os_error(), Some(libc::ENODEV) | Some(libc::EPERM)) {
+                eprintln!("error binding to device (`{}`): {}", interface, err);
                 continue;
             } else {
                 panic!("unexpected error binding device: {}", err);
             }
         }
-        assert_eq!(socket.device().unwrap().as_deref(), Some(interface));
+        assert_eq!(
+            socket.device().unwrap().as_deref(),
+            Some(interface.as_bytes())
+        );
 
         socket.bind_device(None).unwrap();
         assert_eq!(socket.device().unwrap(), None);
         // Just need to do it with one interface.
-        break;
+        return;
     }
+
+    panic!(
+        "failing to bind to any device. \
+        Note that on Linux this requires the `CAP_NET_RAW` permission. \
+        This can be given using `sudo setcap cap_net_raw=ep $test_bin`."
+    );
 }
 
 fn any_ipv4() -> SockAddr {