Unix Domain Sockets

and datagram sockets have fundamentally different behavior (connection-oriented. Why it matters: These enums drive all state-machine transitions. Stream. Focus on `UnixSocketType` and `UnixSocketState` in `kernel/src/net/unix.rs` while you trace the snippet.

// A.1 — UnixSocketType and UnixSocketState enums
// ===========================================================================

/// Unix socket type: stream (connection-oriented) or datagram (connectionless).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum UnixSocketType {
    Stream,
    Datagram,
}

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poll() based on the FdBackend variant. A new variant is needed so the syscall. Why it matters: The FD table dispatches read(), write(), close(), and. Focus on `FdBackend::UnixSocket` and `read` in `kernel/src/process/mod.rs` while you trace the snippet.

/// Backing store for an open file descriptor.
#[derive(Clone)]
pub enum FdBackend {
    /// FD 1/2 stdout/stderr — writes go to serial output.
    Stdout,
    /// FD 0 stdin — reads block until data is available from the kernel stdin buffer.
    Stdin,
    /// Read-only static ramdisk file (pointer + length into kernel .rodata).
    Ramdisk {
        content_addr: usize,
        content_len: usize,
    },
    /// Writable tmpfs file, identified by its path (e.g. "foo/bar.txt"
    /// relative to tmpfs root — no leading `/tmp/`).
    Tmpfs { path: String },
    /// FAT32 on-disk file (Phase 24). Stores the relative path within /data,
    /// the start cluster, file size, and parent directory cluster.
    Fat32Disk {
        path: String,
        start_cluster: u32,
        file_size: u32,
        dir_cluster: u32,
    },
    /// ext2 on-disk file (Phase 28). Stores the root-relative path

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writes via standard read(fd, buf, len) and write(fd, buf, len). These must. Why it matters: Once a Unix stream socket is connected, userspace reads and. Focus on `read` and `write` in `kernel/src/arch/x86_64/syscall.rs` while you trace the snippet.

#[allow(dead_code)]
const NEG_EAGAIN: u64 = (-11_i64) as u64;

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