feat(socket): implement Unix domain sockets with socketpair()

kernel/Cargo.toml

@@ -31,7 +31,7 @@ test_userspace = []
 test_all_exceptions = []
 external_test_bins = []
 vmnet = []  # Use vmnet network config (192.168.64.x) instead of SLIRP (10.0.2.x)
-interactive = []  # Boot into init_shell instead of running automated tests
+interactive = ["testing"]  # Boot into init_shell instead of running automated tests
 
 [dependencies]
 bootloader_api = { git = "https://github.com/rust-osdev/bootloader.git", branch = "main" }

kernel/build.rs

@@ -103,6 +103,7 @@ fn main() {
             println!("cargo:rerun-if-changed={}/fork_test.rs", userspace_tests);
             println!("cargo:rerun-if-changed={}/clock_gettime_test.rs", userspace_tests);
             println!("cargo:rerun-if-changed={}/udp_socket_test.rs", userspace_tests);
+            println!("cargo:rerun-if-changed={}/unix_socket_test.rs", userspace_tests);
             println!("cargo:rerun-if-changed={}/tty_test.rs", userspace_tests);
             println!("cargo:rerun-if-changed={}/job_control_test.rs", userspace_tests);
             println!("cargo:rerun-if-changed={}/session_test.rs", userspace_tests);
@@ -111,6 +112,7 @@ fn main() {
             println!("cargo:rerun-if-changed={}/pipeline_test.rs", userspace_tests);
             println!("cargo:rerun-if-changed={}/sigchld_job_test.rs", userspace_tests);
             println!("cargo:rerun-if-changed={}/cwd_test.rs", userspace_tests);
+            println!("cargo:rerun-if-changed={}/demo.rs", userspace_tests);
             println!("cargo:rerun-if-changed={}/lib.rs", libbreenix_dir.to_str().unwrap());
         }
     } else {

kernel/src/ipc/fd.rs

@@ -114,6 +114,8 @@ pub enum FdKind {
     /// Allow unused - constructed when opening /dev/pts/N in Phase 2
     #[allow(dead_code)]
     PtySlave(u32),
+    /// Unix stream socket (AF_UNIX, SOCK_STREAM) - for socketpair IPC
+    UnixStream(alloc::sync::Arc<spin::Mutex<crate::socket::unix::UnixStreamSocket>>),
 }
 
 impl core::fmt::Debug for FdKind {
@@ -133,6 +135,10 @@ impl core::fmt::Debug for FdKind {
             FdKind::DevptsDirectory { position } => write!(f, "DevptsDirectory(pos={})", position),
             FdKind::PtyMaster(n) => write!(f, "PtyMaster({})", n),
             FdKind::PtySlave(n) => write!(f, "PtySlave({})", n),
+            FdKind::UnixStream(s) => {
+                let sock = s.lock();
+                write!(f, "UnixStream({:?})", sock.endpoint)
+            }
         }
     }
 }
@@ -497,6 +503,11 @@ impl Drop for FdTable {
                         // PTY slave doesn't own the pair, just decrement reference
                         log::debug!("FdTable::drop() - released PTY slave fd {}", i);
                     }
+                    FdKind::UnixStream(socket) => {
+                        // Close the Unix socket endpoint
+                        socket.lock().close();
+                        log::debug!("FdTable::drop() - closed Unix stream socket fd {}", i);
+                    }
                 }
             }
         }

kernel/src/ipc/poll.rs

@@ -232,6 +232,25 @@ pub fn poll_fd(fd_entry: &FileDescriptor, events: i16) -> i16 {
                 revents |= events::POLLERR;
             }
         }
+        FdKind::UnixStream(socket_ref) => {
+            let socket = socket_ref.lock();
+            // Check for readable data
+            if (events & events::POLLIN) != 0 {
+                if socket.has_data() {
+                    revents |= events::POLLIN;
+                }
+            }
+            // Check for writable
+            if (events & events::POLLOUT) != 0 {
+                if !socket.peer_closed() {
+                    revents |= events::POLLOUT;
+                }
+            }
+            // Check for peer closed
+            if socket.peer_closed() && !socket.has_data() {
+                revents |= events::POLLHUP;
+            }
+        }
     }
 
     revents

kernel/src/main.rs

@@ -1048,6 +1048,10 @@ fn kernel_main_continue() -> ! {
         log::info!("=== IPC TEST: Pipe syscall functionality ===");
         test_exec::test_pipe();
 
+        // Test Unix domain socket (AF_UNIX) socketpair syscall
+        log::info!("=== IPC TEST: Unix domain socket (socketpair) functionality ===");
+        test_exec::test_unix_socket();
+
         // NOTE: Pipe + fork and concurrent pipe tests removed to reduce test load.
         // The core pipe functionality is validated by test_pipe() above.
         // These complex multi-process tests cause timing-related timeouts.

kernel/src/process/process.rs

@@ -290,6 +290,11 @@ impl Process {
                         // PTY slave doesn't own the pair, just decrement reference
                         log::debug!("Process::close_all_fds() - released PTY slave fd {}", fd);
                     }
+                    FdKind::UnixStream(socket) => {
+                        // Close Unix socket endpoint
+                        socket.lock().close();
+                        log::debug!("Process::close_all_fds() - closed Unix stream socket fd {}", fd);
+                    }
                 }
             }
         }

kernel/src/socket/mod.rs

@@ -4,6 +4,7 @@
 
 pub mod types;
 pub mod udp;
+pub mod unix;
 
 use spin::Mutex;
 

kernel/src/socket/types.rs

@@ -2,6 +2,13 @@
 //!
 //! POSIX-compatible socket address structures.
 
+/// Address family: Unix (local)
+pub const AF_UNIX: u16 = 1;
+
+/// Address family: Unix (alias for AF_UNIX)
+#[allow(dead_code)]
+pub const AF_LOCAL: u16 = 1;
+
 /// Address family: IPv4
 pub const AF_INET: u16 = 2;
 
@@ -11,6 +18,12 @@ pub const SOCK_STREAM: u16 = 1;
 /// Socket type: Datagram (UDP)
 pub const SOCK_DGRAM: u16 = 2;
 
+/// Socket flag: Non-blocking mode
+pub const SOCK_NONBLOCK: u32 = 0x800;
+
+/// Socket flag: Close-on-exec
+pub const SOCK_CLOEXEC: u32 = 0x80000;
+
 /// IPv4 socket address structure (matches Linux sockaddr_in)
 #[repr(C)]
 #[derive(Debug, Clone, Copy)]