Added bind_device_by_index_{v4,v6} for linux and android (#569)

Author: boris-n

src/sys/unix.rs

@@ -24,6 +24,8 @@ use std::net::{Ipv4Addr, Ipv6Addr};
         target_os = "watchos",
         target_os = "illumos",
         target_os = "solaris",
+        target_os = "linux",
+        target_os = "android",
     )
 ))]
 use std::num::NonZeroU32;
@@ -1847,6 +1849,28 @@ impl crate::Socket {
         unsafe { setsockopt(self.as_raw(), IPPROTO_IP, libc::IP_BOUND_IF, index) }
     }
 
+    /// Sets the value for `SO_BINDTOIFINDEX` option on this socket.
+    ///
+    /// If a socket is bound to an interface, only packets received from that
+    /// particular interface are processed by the socket.
+    ///
+    /// If `interface` is `None`, the binding is removed. If the `interface`
+    /// index is not valid, an error is returned.
+    ///
+    /// One can use [`libc::if_nametoindex`] to convert an interface alias to an
+    /// index.
+    #[cfg(all(
+        feature = "all",
+        any(
+            target_os = "linux",
+            target_os = "android",
+        )
+    ))]
+    pub fn bind_device_by_index_v4(&self, interface: Option<NonZeroU32>) -> io::Result<()> {
+        let index = interface.map_or(0, NonZeroU32::get);
+        unsafe { setsockopt(self.as_raw(), libc::SOL_SOCKET, libc::SO_BINDTOIFINDEX, index) }
+    }
+
     /// Sets the value for `IPV6_BOUND_IF` option on this socket.
     ///
     /// If a socket is bound to an interface, only packets received from that
@@ -1874,6 +1898,27 @@ impl crate::Socket {
         unsafe { setsockopt(self.as_raw(), IPPROTO_IPV6, libc::IPV6_BOUND_IF, index) }
     }
 
+    /// Sets the value for `SO_BINDTOIFINDEX` option on this socket.
+    ///
+    /// If a socket is bound to an interface, only packets received from that
+    /// particular interface are processed by the socket.
+    ///
+    /// If `interface` is `None`, the binding is removed. If the `interface`
+    /// index is not valid, an error is returned.
+    ///
+    /// One can use [`libc::if_nametoindex`] to convert an interface alias to an
+    /// index.
+    #[cfg(all(
+        feature = "all",
+        any(
+            target_os = "linux",
+            target_os = "android",
+        )
+    ))]
+    pub fn bind_device_by_index_v6(&self, interface: Option<NonZeroU32>) -> io::Result<()> {
+        self.bind_device_by_index_v4(interface) // socket layer option, no IP version dependency
+    }
+
     /// Gets the value for `IP_BOUND_IF` option on this socket, i.e. the index
     /// for the interface to which the socket is bound.
     ///