diff --git a/src/call.rs b/src/call.rs
index e6dfb95ea7..53ec5a530b 100644
--- a/src/call.rs
+++ b/src/call.rs
@@ -8,6 +8,11 @@ use super::{
 
 use core::mem;
 
+/// Close a file descriptor
+pub fn close(fd: usize) -> Result<usize> {
+    unsafe { syscall1(SYS_CLOSE, fd) }
+}
+
 /// Get the current system time
 pub fn clock_gettime(clock: usize, tp: &mut TimeSpec) -> Result<usize> {
     unsafe { syscall2(SYS_CLOCK_GETTIME, clock, tp as *mut TimeSpec as usize) }
@@ -18,6 +23,11 @@ pub fn dup_into(fd: usize, out: usize, buf: &[u8]) -> Result<usize> {
     unsafe { syscall4(SYS_DUP_INTO, fd, buf.as_ptr() as usize, buf.len(), out) }
 }
 
+/// Copy and transform a file descriptor, letting the kernel allocate the new fd
+pub fn dup(fd: usize, buf: &[u8]) -> Result<usize> {
+    unsafe { syscall3(SYS_DUP, fd, buf.as_ptr() as usize, buf.len()) }
+}
+
 /// Copy and transform a file descriptor
 pub fn dup2(fd: usize, newfd: usize, buf: &[u8]) -> Result<usize> {
     unsafe { syscall4(SYS_DUP2, fd, newfd, buf.as_ptr() as usize, buf.len()) }
@@ -191,6 +201,40 @@ pub fn openat_into<T: AsRef<str>>(
     }
 }
 
+/// Open a file at a specific path, letting the kernel allocate the new fd
+pub fn openat<T: AsRef<str>>(fd: usize, path: T, flags: usize, fcntl_flags: usize) -> Result<usize> {
+    let path = path.as_ref();
+    unsafe {
+        syscall5(
+            SYS_OPENAT,
+            fd,
+            path.as_ptr() as usize,
+            path.len(),
+            flags,
+            fcntl_flags,
+        )
+    }
+}
+
+/// Send a file descriptor to another process via a socket
+pub fn sendfd(receiver_socket: usize, fd: usize, flags: usize, arg: u64) -> Result<usize> {
+    #[cfg(target_pointer_width = "32")]
+    unsafe {
+        syscall5(
+            SYS_SENDFD,
+            receiver_socket,
+            fd,
+            flags,
+            arg as u32 as usize,
+            (arg >> 32) as usize,
+        )
+    }
+    #[cfg(target_pointer_width = "64")]
+    unsafe {
+        syscall4(SYS_SENDFD, receiver_socket, fd, flags, arg as usize)
+    }
+}
+
 /// Remove a file at at specific path
 pub fn unlinkat<T: AsRef<str>>(fd: usize, path: T, flags: usize) -> Result<usize> {
     let path = path.as_ref();
diff --git a/src/number.rs b/src/number.rs
index faf0b67421..9992b7189d 100644
--- a/src/number.rs
+++ b/src/number.rs
@@ -10,9 +10,10 @@ pub const SYS_ARG_PATH: usize = 0x0300_0000;
 pub const SYS_RET: usize = 0x00F0_0000;
 pub const SYS_RET_FILE: usize = 0x0010_0000;
 
+/// Upstream 0.9.0 `openat_into` (caller supplies target fd number).
 pub const SYS_OPENAT_INTO: usize = SYS_CLASS_PATH | SYS_RET_FILE | 987;
-/// Red Bear alias for the legacy SYS_OPENAT name (upstream 0.9.0 renamed to SYS_OPENAT_INTO).
-pub const SYS_OPENAT: usize = SYS_OPENAT_INTO;
+/// Legacy Red Bear `openat` (kernel allocates a new fd).
+pub const SYS_OPENAT: usize = SYS_CLASS_PATH | SYS_RET_FILE | 7;
 /// Red Bear: preserve legacy SYS_OPENAT_WITH_FILTER (upstream 0.9.0 removed it; retained for kernel/userspace ABI).
 pub const SYS_OPENAT_WITH_FILTER: usize = SYS_CLASS_PATH | SYS_RET_FILE | 985;
 pub const SYS_UNLINKAT: usize = SYS_CLASS_PATH | 263;
@@ -20,9 +21,10 @@ pub const SYS_UNLINKAT: usize = SYS_CLASS_PATH | 263;
 pub const SYS_UNLINKAT_WITH_FILTER: usize = SYS_CLASS_PATH | 986;
 
 pub const SYS_CLOSE: usize = SYS_CLASS_FILE | 6;
+/// Upstream 0.9.0 `dup_into` (caller supplies target fd number).
 pub const SYS_DUP_INTO: usize = SYS_CLASS_FILE | SYS_RET_FILE | 988;
-/// Red Bear alias for the legacy SYS_DUP name (upstream 0.9.0 renamed to SYS_DUP_INTO).
-pub const SYS_DUP: usize = SYS_DUP_INTO;
+/// Legacy Red Bear `dup` (kernel allocates a new fd).
+pub const SYS_DUP: usize = SYS_CLASS_FILE | SYS_RET_FILE | 41;
 pub const SYS_DUP2: usize = SYS_CLASS_FILE | SYS_RET_FILE | 63;
 /// Red Bear: preserve legacy SYS_SENDFD (upstream 0.9.0 removed it; retained for kernel/userspace ABI).
 pub const SYS_SENDFD: usize = SYS_CLASS_FILE | 34;