rCore/kernel/src/syscall/net.rs

//! Syscalls for networking

use super::*;
use crate::drivers::{NET_DRIVERS, SOCKET_ACTIVITY};
use core::mem::size_of;
use smoltcp::socket::*;
use smoltcp::wire::*;

const AF_UNIX: usize = 1;
const AF_INET: usize = 2;

const SOCK_STREAM: usize = 1;
const SOCK_DGRAM: usize = 2;
const SOCK_RAW: usize = 3;
const SOCK_TYPE_MASK: usize = 0xf;

const IPPROTO_IP: usize = 0;
const IPPROTO_ICMP: usize = 1;

fn get_ephemeral_port() -> u16 {
    // TODO selects non-conflict high port
    static mut EPHEMERAL_PORT: u16 = 49152;
    unsafe {
        if EPHEMERAL_PORT == 65535 {
            EPHEMERAL_PORT = 49152;
        } else {
            EPHEMERAL_PORT = EPHEMERAL_PORT + 1;
        }
        EPHEMERAL_PORT
    }
}

pub fn sys_socket(domain: usize, socket_type: usize, protocol: usize) -> SysResult {
    info!(
        "socket: domain: {}, socket_type: {}, protocol: {}",
        domain, socket_type, protocol
    );
    let mut proc = process();
    let iface = &*(NET_DRIVERS.read()[0]);
    match domain {
        AF_INET | AF_UNIX => match socket_type & SOCK_TYPE_MASK {
            SOCK_STREAM => {
                let fd = proc.get_free_fd();

                let tcp_rx_buffer = TcpSocketBuffer::new(vec![0; 2048]);
                let tcp_tx_buffer = TcpSocketBuffer::new(vec![0; 2048]);
                let tcp_socket = TcpSocket::new(tcp_rx_buffer, tcp_tx_buffer);

                let tcp_handle = iface.sockets().add(tcp_socket);
                proc.files.insert(
                    fd,
                    FileLike::Socket(SocketWrapper {
                        handle: tcp_handle,
                        socket_type: SocketType::Tcp(None),
                    }),
                );

                Ok(fd)
            }
            SOCK_DGRAM => {
                let fd = proc.get_free_fd();

                let udp_rx_buffer =
                    UdpSocketBuffer::new(vec![UdpPacketMetadata::EMPTY], vec![0; 2048]);
                let udp_tx_buffer =
                    UdpSocketBuffer::new(vec![UdpPacketMetadata::EMPTY], vec![0; 2048]);
                let udp_socket = UdpSocket::new(udp_rx_buffer, udp_tx_buffer);

                let udp_handle = iface.sockets().add(udp_socket);
                proc.files.insert(
                    fd,
                    FileLike::Socket(SocketWrapper {
                        handle: udp_handle,
                        socket_type: SocketType::Udp,
                    }),
                );

                Ok(fd)
            }
            SOCK_RAW => {
                let fd = proc.get_free_fd();

                let raw_rx_buffer =
                    RawSocketBuffer::new(vec![RawPacketMetadata::EMPTY; 2], vec![0; 2048]);
                let raw_tx_buffer =
                    RawSocketBuffer::new(vec![RawPacketMetadata::EMPTY; 2], vec![0; 2048]);
                let raw_socket = RawSocket::new(
                    IpVersion::Ipv4,
                    IpProtocol::from(protocol as u8),
                    raw_rx_buffer,
                    raw_tx_buffer,
                );

                let raw_handle = iface.sockets().add(raw_socket);
                proc.files.insert(
                    fd,
                    FileLike::Socket(SocketWrapper {
                        handle: raw_handle,
                        socket_type: SocketType::Raw,
                    }),
                );
                Ok(fd)
            }
            _ => Err(SysError::EINVAL),
        },
        _ => Err(SysError::EAFNOSUPPORT),
    }
}

pub fn sys_setsockopt(
    fd: usize,
    level: usize,
    optname: usize,
    optval: *const u8,
    optlen: usize,
) -> SysResult {
    info!(
        "setsockopt: fd: {}, level: {}, optname: {}",
        fd, level, optname
    );
    warn!("sys_setsockopt is unimplemented");
    Ok(0)
}

pub fn sys_getsockopt(
    fd: usize,
    level: usize,
    optname: usize,
    optval: *mut u8,
    optlen: *mut u32,
) -> SysResult {
    info!(
        "getsockopt: fd: {}, level: {}, optname: {} optval: {:?} optlen: {:?}",
        fd, level, optname, optval, optlen
    );
    warn!("sys_getsockopt is unimplemented");
    Err(SysError::ENOPROTOOPT)
}

impl Process {
    fn get_socket(&mut self, fd: usize) -> Result<SocketWrapper, SysError> {
        let file = self.files.get_mut(&fd).ok_or(SysError::EBADF)?;
        match file {
            FileLike::Socket(wrapper) => Ok(wrapper.clone()),
            _ => Err(SysError::ENOTSOCK),
        }
    }

    fn get_socket_mut(&mut self, fd: usize) -> Result<&mut SocketWrapper, SysError> {
        let file = self.files.get_mut(&fd).ok_or(SysError::EBADF)?;
        match file {
            FileLike::Socket(ref mut wrapper) => Ok(wrapper),
            _ => Err(SysError::ENOTSOCK),
        }
    }
}

pub fn sys_connect(fd: usize, addr: *const SockaddrIn, addrlen: usize) -> SysResult {
    info!(
        "sys_connect: fd: {}, addr: {:?}, addrlen: {}",
        fd, addr, addrlen
    );

    let mut proc = process();
    proc.memory_set.check_ptr(addr)?;

    // FIXME: check size as per sin_family
    let sockaddr_in = unsafe { &*(addr) };
    let endpoint = sockaddr_in.to_endpoint()?;

    let wrapper = proc.get_socket(fd)?;
    if let SocketType::Tcp(_) = wrapper.socket_type {
        let iface = &*(NET_DRIVERS.read()[0]);
        let mut sockets = iface.sockets();
        let mut socket = sockets.get::<TcpSocket>(wrapper.handle);

        let temp_port = get_ephemeral_port();

        match socket.connect(endpoint, temp_port) {
            Ok(()) => {
                // avoid deadlock
                drop(socket);
                drop(sockets);

                // wait for connection result
                loop {
                    let iface = &*(NET_DRIVERS.read()[0]);
                    iface.poll();

                    let mut sockets = iface.sockets();
                    let mut socket = sockets.get::<TcpSocket>(wrapper.handle);
                    if socket.state() == TcpState::SynSent {
                        // still connecting
                        drop(socket);
                        drop(sockets);
                        debug!("poll for connection wait");
                        SOCKET_ACTIVITY._wait();
                    } else if socket.state() == TcpState::Established {
                        break Ok(0);
                    } else {
                        break Err(SysError::ECONNREFUSED);
                    }
                }
            }
            Err(_) => Err(SysError::ENOBUFS),
        }
    } else if let SocketType::Udp = wrapper.socket_type {
        // do nothing when only sendto() is used
        Ok(0)
    } else {
        unimplemented!("socket type")
    }
}

pub fn sys_write_socket(proc: &mut Process, fd: usize, base: *const u8, len: usize) -> SysResult {
    let iface = &*(NET_DRIVERS.read()[0]);
    let wrapper = proc.get_socket(fd)?;
    if let SocketType::Tcp(_) = wrapper.socket_type {
        let mut sockets = iface.sockets();
        let mut socket = sockets.get::<TcpSocket>(wrapper.handle);

        let slice = unsafe { slice::from_raw_parts(base, len) };
        if socket.is_open() {
            if socket.can_send() {
                match socket.send_slice(&slice) {
                    Ok(size) => {
                        // avoid deadlock
                        drop(socket);
                        drop(sockets);

                        iface.poll();
                        Ok(size)
                    }
                    Err(err) => Err(SysError::ENOBUFS),
                }
            } else {
                Err(SysError::ENOBUFS)
            }
        } else {
            Err(SysError::ENOTCONN)
        }
    } else {
        unimplemented!("socket type")
    }
}

pub fn sys_read_socket(proc: &mut Process, fd: usize, base: *mut u8, len: usize) -> SysResult {
    let iface = &*(NET_DRIVERS.read()[0]);
    let wrapper = proc.get_socket(fd)?;
    if let SocketType::Tcp(_) = wrapper.socket_type {
        loop {
            let mut sockets = iface.sockets();
            let mut socket = sockets.get::<TcpSocket>(wrapper.handle);

            if socket.is_open() {
                let mut slice = unsafe { slice::from_raw_parts_mut(base, len) };
                if let Ok(size) = socket.recv_slice(&mut slice) {
                    // avoid deadlock
                    drop(socket);
                    drop(sockets);

                    iface.poll();
                    return Ok(size);
                }
            } else {
                return Err(SysError::ENOTCONN);
            }

            // avoid deadlock
            drop(socket);
            drop(sockets);
            SOCKET_ACTIVITY._wait()
        }
    } else if let SocketType::Udp = wrapper.socket_type {
        loop {
            let mut sockets = iface.sockets();
            let mut socket = sockets.get::<UdpSocket>(wrapper.handle);

            if socket.is_open() {
                let mut slice = unsafe { slice::from_raw_parts_mut(base, len) };
                if let Ok((size, _)) = socket.recv_slice(&mut slice) {
                    // avoid deadlock
                    drop(socket);
                    drop(sockets);

                    iface.poll();
                    return Ok(size);
                }
            } else {
                return Err(SysError::ENOTCONN);
            }

            // avoid deadlock
            drop(socket);
            SOCKET_ACTIVITY._wait()
        }
    } else {
        unimplemented!("socket type")
    }
}

pub fn sys_sendto(
    fd: usize,
    buffer: *const u8,
    len: usize,
    flags: usize,
    addr: *const SockaddrIn,
    addr_len: usize,
) -> SysResult {
    info!(
        "sys_sendto: fd: {} buffer: {:?} len: {} addr: {:?} addr_len: {}",
        fd, buffer, len, addr, addr_len
    );

    let mut proc = process();
    proc.memory_set.check_ptr(addr)?;
    proc.memory_set.check_array(buffer, len)?;

    let sockaddr_in = unsafe { &*(addr) };
    let endpoint = sockaddr_in.to_endpoint()?;

    let iface = &*(NET_DRIVERS.read()[0]);

    let wrapper = proc.get_socket(fd)?;
    if let SocketType::Raw = wrapper.socket_type {
        let v4_src = iface.ipv4_address().unwrap();
        let mut sockets = iface.sockets();
        let mut socket = sockets.get::<RawSocket>(wrapper.handle);

        if let IpAddress::Ipv4(v4_dst) = endpoint.addr {
            let slice = unsafe { slice::from_raw_parts(buffer, len) };
            // using 20-byte IPv4 header
            let mut buffer = vec![0u8; len + 20];
            let mut packet = Ipv4Packet::new_unchecked(&mut buffer);
            packet.set_version(4);
            packet.set_header_len(20);
            packet.set_total_len((20 + len) as u16);
            packet.set_protocol(socket.ip_protocol().into());
            packet.set_src_addr(v4_src);
            packet.set_dst_addr(v4_dst);
            let payload = packet.payload_mut();
            payload.copy_from_slice(slice);
            packet.fill_checksum();

            socket.send_slice(&buffer).unwrap();

            // avoid deadlock
            drop(socket);
            drop(sockets);
            iface.poll();

            Ok(len)
        } else {
            unimplemented!("ip type")
        }
    } else if let SocketType::Udp = wrapper.socket_type {
        let v4_src = iface.ipv4_address().unwrap();
        let mut sockets = iface.sockets();
        let mut socket = sockets.get::<UdpSocket>(wrapper.handle);

        if !socket.endpoint().is_specified() {
            let temp_port = get_ephemeral_port();
            socket
                .bind(IpEndpoint::new(IpAddress::Ipv4(v4_src), temp_port))
                .unwrap();
        }

        let slice = unsafe { slice::from_raw_parts(buffer, len) };

        socket
            .send_slice(&slice, endpoint)
            .unwrap();

        // avoid deadlock
        drop(socket);
        drop(sockets);
        iface.poll();

        Ok(len)
    } else {
        unimplemented!("socket type")
    }
}

pub fn sys_recvfrom(
    fd: usize,
    buffer: *mut u8,
    len: usize,
    flags: usize,
    addr: *mut SockaddrIn,
    addr_len: *mut u32,
) -> SysResult {
    info!(
        "sys_recvfrom: fd: {} buffer: {:?} len: {} flags: {} addr: {:?} addr_len: {:?}",
        fd, buffer, len, flags, addr, addr_len
    );

    let mut proc = process();
    proc.memory_set.check_mut_array(buffer, len)?;

    if !addr.is_null() {
        proc.memory_set.check_mut_ptr(addr_len)?;

        let max_addr_len = unsafe { *addr_len } as usize;
        if max_addr_len < size_of::<SockaddrIn>() {
            return Err(SysError::EINVAL);
        }

        proc.memory_set.check_mut_array(addr, max_addr_len)?;
    }

    let iface = &*(NET_DRIVERS.read()[0]);

    let wrapper = proc.get_socket(fd)?;
    // TODO: move some part of these into one generic function
    if let SocketType::Raw = wrapper.socket_type {
        loop {
            let mut sockets = iface.sockets();
            let mut socket = sockets.get::<RawSocket>(wrapper.handle);

            let mut slice = unsafe { slice::from_raw_parts_mut(buffer, len) };
            if let Ok(size) = socket.recv_slice(&mut slice) {
                let mut packet = Ipv4Packet::new_unchecked(&slice);

                if !addr.is_null() {
                    // FIXME: check size as per sin_family
                    let sockaddr_in = SockaddrIn::from(IpEndpoint {
                        addr: IpAddress::Ipv4(packet.src_addr()),
                        port: 0,
                    });
                    unsafe { sockaddr_in.write_to(addr, addr_len); }
                }

                return Ok(size);
            }

            // avoid deadlock
            drop(socket);
            drop(sockets);
            SOCKET_ACTIVITY._wait()
        }
    } else if let SocketType::Udp = wrapper.socket_type {
        loop {
            let mut sockets = iface.sockets();
            let mut socket = sockets.get::<UdpSocket>(wrapper.handle);

            let mut slice = unsafe { slice::from_raw_parts_mut(buffer, len) };
            if let Ok((size, endpoint)) = socket.recv_slice(&mut slice) {
                if !addr.is_null() {
                    let sockaddr_in = SockaddrIn::from(endpoint);
                    unsafe { sockaddr_in.write_to(addr, addr_len); }
                }

                return Ok(size);
            }

            // avoid deadlock
            drop(socket);
            drop(sockets);
            SOCKET_ACTIVITY._wait()
        }
    } else if let SocketType::Tcp(_) = wrapper.socket_type {
        loop {
            let mut sockets = iface.sockets();
            let mut socket = sockets.get::<TcpSocket>(wrapper.handle);

            let mut slice = unsafe { slice::from_raw_parts_mut(buffer, len) };
            if let Ok(size) = socket.recv_slice(&mut slice) {
                if !addr.is_null() {
                    let sockaddr_in = SockaddrIn::from(socket.remote_endpoint());
                    unsafe { sockaddr_in.write_to(addr, addr_len); }
                }

                return Ok(size);
            }

            // avoid deadlock
            drop(socket);
            drop(sockets);
            SOCKET_ACTIVITY._wait()
        }
    } else {
        unimplemented!("socket type")
    }
}

impl Drop for SocketWrapper {
    fn drop(&mut self) {
        let iface = &*(NET_DRIVERS.read()[0]);
        let mut sockets = iface.sockets();
        sockets.release(self.handle);
        sockets.prune();

        // send FIN immediately when applicable
        drop(sockets);
        iface.poll();
    }
}

pub fn sys_bind(fd: usize, addr: *const SockaddrIn, len: usize) -> SysResult {
    info!("sys_bind: fd: {} addr: {:?} len: {}", fd, addr, len);
    let mut proc = process();

    if len < size_of::<SockaddrIn>() {
        return Err(SysError::EINVAL);
    }

    let sockaddr_in = unsafe { &*(addr) };
    let mut endpoint = sockaddr_in.to_endpoint()?;
    if endpoint.port == 0 {
        endpoint.port = get_ephemeral_port();
    }

    let iface = &*(NET_DRIVERS.read()[0]);
    let wrapper = &mut proc.get_socket_mut(fd)?;
    if let SocketType::Tcp(_) = wrapper.socket_type {
        wrapper.socket_type = SocketType::Tcp(Some(endpoint));
        Ok(0)
    } else {
        Err(SysError::EINVAL)
    }
}

pub fn sys_listen(fd: usize, backlog: usize) -> SysResult {
    info!("sys_listen: fd: {} backlog: {}", fd, backlog);
    // smoltcp tcp sockets do not support backlog
    // open multiple sockets for each connection
    let mut proc = process();

    let iface = &*(NET_DRIVERS.read()[0]);
    let wrapper = proc.get_socket_mut(fd)?;
    if let SocketType::Tcp(Some(endpoint)) = wrapper.socket_type {
        let mut sockets = iface.sockets();
        let mut socket = sockets.get::<TcpSocket>(wrapper.handle);

        info!("socket {} listening on {:?}", fd, endpoint);
        if !socket.is_listening() {
            match socket.listen(endpoint) {
                Ok(()) => Ok(0),
                Err(err) => {
                    Err(SysError::EINVAL)
                },
            }
        } else {
            Ok(0)
        }
    } else {
        Err(SysError::EINVAL)
    }
}

pub fn sys_shutdown(fd: usize, how: usize) -> SysResult {
    info!("sys_shutdown: fd: {} how: {}", fd, how);
    let mut proc = process();

    let iface = &*(NET_DRIVERS.read()[0]);
    let wrapper = proc.get_socket_mut(fd)?;
    if let SocketType::Tcp(Some(endpoint)) = wrapper.socket_type {
        let mut sockets = iface.sockets();
        let mut socket = sockets.get::<TcpSocket>(wrapper.handle);
        socket.close();
        Ok(0)
    } else {
        Err(SysError::EINVAL)
    }
}

pub fn sys_accept(fd: usize, addr: *mut SockaddrIn, addr_len: *mut u32) -> SysResult {
    info!(
        "sys_accept: fd: {} addr: {:?} addr_len: {:?}",
        fd, addr, addr_len
    );
    // smoltcp tcp sockets do not support backlog
    // open multiple sockets for each connection
    let mut proc = process();

    if !addr.is_null() {
        proc.memory_set.check_mut_ptr(addr_len)?;

        let max_addr_len = unsafe { *addr_len } as usize;
        if max_addr_len < size_of::<SockaddrIn>() {
            debug!("length too short {}", max_addr_len);
            return Err(SysError::EINVAL);
        }

        proc.memory_set.check_mut_ptr(addr)?;
    }

    let wrapper = proc.get_socket_mut(fd)?;
    if let SocketType::Tcp(Some(endpoint)) = wrapper.socket_type {
        loop {
            let iface = &*(NET_DRIVERS.read()[0]);
            let mut sockets = iface.sockets();
            let mut socket = sockets.get::<TcpSocket>(wrapper.handle);

            if socket.is_active() {
                let remote_endpoint = socket.remote_endpoint();
                drop(socket);

                // move the current one to new_fd
                // create a new one in fd
                let new_fd = proc.get_free_fd();

                let tcp_rx_buffer = TcpSocketBuffer::new(vec![0; 2048]);
                let tcp_tx_buffer = TcpSocketBuffer::new(vec![0; 2048]);
                let mut tcp_socket = TcpSocket::new(tcp_rx_buffer, tcp_tx_buffer);
                tcp_socket.listen(endpoint).unwrap();

                let tcp_handle = sockets.add(tcp_socket);
                let orig_handle = proc
                    .files
                    .insert(
                        fd,
                        FileLike::Socket(SocketWrapper {
                            handle: tcp_handle,
                            socket_type: SocketType::Tcp(Some(endpoint)),
                        }),
                    )
                    .unwrap();
                proc.files.insert(new_fd, orig_handle);

                if !addr.is_null() {
                    let sockaddr_in = SockaddrIn::from(remote_endpoint);
                    unsafe { sockaddr_in.write_to(addr, addr_len); }
                }
                return Ok(new_fd);
            }

            // avoid deadlock
            drop(socket);
            drop(sockets);
            SOCKET_ACTIVITY._wait()
        }
    } else {
        debug!("bad socket type {:?}", wrapper);
        Err(SysError::EINVAL)
    }
}

pub fn sys_getsockname(fd: usize, addr: *mut SockaddrIn, addr_len: *mut u32) -> SysResult {
    info!(
        "sys_getsockname: fd: {} addr: {:?} addr_len: {:?}",
        fd, addr, addr_len
    );

    // smoltcp tcp sockets do not support backlog
    // open multiple sockets for each connection
    let mut proc = process();

    if addr.is_null() {
        return Err(SysError::EINVAL);
    }

    proc.memory_set.check_mut_ptr(addr_len)?;

    let max_addr_len = unsafe { *addr_len } as usize;
    if max_addr_len < size_of::<SockaddrIn>() {
        return Err(SysError::EINVAL);
    }

    proc.memory_set.check_mut_array(addr, max_addr_len)?;

    let iface = &*(NET_DRIVERS.read()[0]);
    let wrapper = proc.get_socket_mut(fd)?;
    if let SocketType::Tcp(Some(endpoint)) = wrapper.socket_type {
        let sockaddr_in = SockaddrIn::from(endpoint);
        unsafe { sockaddr_in.write_to(addr, addr_len); }
        return Ok(0);
    } else {
        Err(SysError::EINVAL)
    }
}

pub fn sys_getpeername(fd: usize, addr: *mut SockaddrIn, addr_len: *mut u32) -> SysResult {
    info!(
        "sys_getpeername: fd: {} addr: {:?} addr_len: {:?}",
        fd, addr, addr_len
    );

    // smoltcp tcp sockets do not support backlog
    // open multiple sockets for each connection
    let mut proc = process();

    if addr as usize == 0 {
        return Err(SysError::EINVAL);
    }

    proc.memory_set.check_mut_ptr(addr_len)?;

    let max_addr_len = unsafe { *addr_len } as usize;
    if max_addr_len < size_of::<SockaddrIn>() {
        return Err(SysError::EINVAL);
    }

    proc.memory_set.check_mut_array(addr, max_addr_len)?;

    let iface = &*(NET_DRIVERS.read()[0]);
    let wrapper = proc.get_socket_mut(fd)?;
    if let SocketType::Tcp(Some(endpoint)) = wrapper.socket_type {
        let mut sockets = iface.sockets();
        let socket = sockets.get::<TcpSocket>(wrapper.handle);

        if socket.is_open() {
            let remote_endpoint = socket.remote_endpoint();
            let sockaddr_in = SockaddrIn::from(remote_endpoint);
            unsafe { sockaddr_in.write_to(addr, addr_len); }
            Ok(0)
        } else {
            Err(SysError::EINVAL)
        }
    } else {
        Err(SysError::EINVAL)
    }
}

/// Check socket state
/// return (in, out, err)
pub fn poll_socket(wrapper: &SocketWrapper) -> (bool, bool, bool) {
    let mut input = false;
    let mut output = false;
    let mut err = false;
    if let SocketType::Tcp(_) = wrapper.socket_type {
        let iface = &*(NET_DRIVERS.read()[0]);
        let mut sockets = iface.sockets();
        let mut socket = sockets.get::<TcpSocket>(wrapper.handle);

        if !socket.is_open() {
            err = true;
        } else {
            if socket.can_recv() {
                input = true;
            }

            if socket.can_send() {
                output = true;
            }
        }
    } else {
        unimplemented!()
    }

    (input, output, err)
}

pub fn sys_dup2_socket(proc: &mut Process, wrapper: SocketWrapper, fd: usize) -> SysResult {
    let iface = &*(NET_DRIVERS.read()[0]);
    let mut sockets = iface.sockets();
    sockets.retain(wrapper.handle);
    proc.files.insert(
        fd,
        FileLike::Socket(wrapper),
    );
    Ok(fd)
}

#[repr(C)]
pub struct SockaddrIn {
    sin_family: u16,
    sin_port: u16,
    sin_addr: u32,
    sin_zero: [u8; 8],
}

impl From<IpEndpoint> for SockaddrIn {
    fn from(endpoint: IpEndpoint) -> Self {
        match endpoint.addr {
            IpAddress::Ipv4(ipv4) => {
                SockaddrIn {
                    sin_family: AF_INET as u16,
                    sin_port: u16::to_be(endpoint.port),
                    sin_addr: u32::to_be(u32::from_be_bytes(ipv4.0)),
                    sin_zero: [0; 8],
                }
            }
            _ => unimplemented!("ipv6")
        }
    }
}

impl SockaddrIn {
    fn to_endpoint(&self) -> Result<IpEndpoint, SysError> {
        // FIXME: check size as per sin_family
        if self.sin_family == AF_INET as u16 {
            let port = u16::from_be(self.sin_port);
            let addr = IpAddress::from(Ipv4Address::from_bytes(
                &u32::from_be(self.sin_addr).to_be_bytes()[..]
            ));
            Ok((addr, port).into())
        } else if self.sin_family == AF_UNIX as u16 {
            debug!("unix socket path {}", unsafe {util::from_cstr((self as *const SockaddrIn as *const u8).add(2)) });
            Err(SysError::EINVAL)
        } else {
            Err(SysError::EINVAL)
        }
    }
    unsafe fn write_to(self, addr: *mut SockaddrIn, addr_len: *mut u32) {
        addr.write(self);
        addr_len.write(size_of::<SockaddrIn>() as u32);
    }
}