fix the inet_pton test of the os-test test suite

src/header/arpa_inet/mod.rs

@@ -222,7 +222,7 @@ pub unsafe extern "C" fn inet_pton(af: c_int, src: *const c_char, dst: *mut c_vo
         for part in s_addr.iter_mut().take(4) {
             if let Some(n) = octets
                 .next()
-                .filter(|x| !x.len() > 3)
+                .filter(|x| x.len() <= 3)
                 .and_then(|x| u8::from_str(x).ok())
             {
                 *part = n;

src/header/sys_socket/constants.rs

@@ -168,6 +168,7 @@ pub const MCAST_LEAVE_SOURCE_GROUP: c_int = 47;
 /// Internet domain sockets for use with IPv4 sockets.
 pub const AF_INET: c_int = 2;
 /// Internet domain sockets for use with IPv6 sockets.
+#[cfg(feature = "ip6")]
 pub const AF_INET6: c_int = 10;
 /// Non-POSIX, see <https://www.man7.org/linux/man-pages/man7/unix.7.html>.
 ///