// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

library fuchsia.posix.socket;

using fuchsia.io;
using fuchsia.net;
using zx;

/// Chosen to match `sizeof(struct sockaddr_storage)`.
using sockaddr = bytes:128;

/// Chosen to be large enough to hold whatever we might want to cram in it. So long as we support
/// socket options, we don't have a good sense of what we might want to send as payload.
// TODO(https://fxbug.dev/44347): replace C structures on the wire with FIDL types.
using sockopt = bytes:900;

/// The maximum length of an interface name.
// `sizeof((struct ifreq).ifr_name) == 16`; the last byte is reserved for the null terminator.
const uint8 INTERFACE_NAME_LENGTH = 15;

/// An interface name as a sequence of bytes.
using interface_name = string:INTERFACE_NAME_LENGTH;

/// A network socket.
///
/// Once a socket has been retrieved from a `Provider`, this interface is then used to further
/// configure and use the socket. This interface is essentially POSIX. Its implementation must
/// support Linux-specific arguments to {Get,Set}SockOpt.
///
/// All methods on this type are nonblocking; their exact behaviors match their Linux counterparts.
///
/// *Warning:* This protocol is not yet ready for direct use by clients. Instead, clients should
/// use the BSD sockets API to interact with sockets. We plan to change this protocol substantially
/// and clients that couple directly to this protocol will make those changes more difficult.
protocol BaseSocket {
    compose fuchsia.io.Node;

    /// Sets the local address used for the socket.
    Bind(sockaddr addr) -> () error int32;
    /// Initiates a connection to a remote address.
    Connect(sockaddr addr) -> () error int32;
    /// Retrieves the local socket address.
    GetSockName() -> (sockaddr addr) error int32;
    /// Retrieves the remote socket address.
    GetPeerName() -> (sockaddr addr) error int32;
    /// Sets the value of a socket option.
    SetSockOpt(int16 level, int16 optname, sockopt optval) -> () error int32;
    /// Retrieves the value of a socket option.
    GetSockOpt(int16 level, int16 optname) -> (sockopt optval) error int32;
};

/// A datagram socket.
///
/// This type's [`fuchsia.io.Node/Describe`] method returns an eventpair which is used to signal
/// additional information about the state of the socket such as readiness or shutdown-ness.
///
/// All methods on this type are nonblocking; their exact behaviors match their Linux counterparts.
protocol DatagramSocket {
    compose BaseSocket;

    /// Shuts down part of the socket.
    Shutdown(int16 how) -> () error int32;
    /// Receives a message from the socket.
    RecvMsg(uint32 addr_len, uint32 data_len, uint32 control_len, int16 flags) -> (sockaddr addr, bytes data, bytes control, uint32 truncated) error int32;
    /// Sends a message on the socket.
    SendMsg(sockaddr addr, vector<bytes>:MAX data, bytes control, int16 flags) -> (int64 len) error int32;
    /// Sends a message on the socket.
    SendMsg2(sockaddr addr, bytes:MAX data, bytes control, int16 flags) -> (int64 len) error int32;
};

/// A stream socket.
///
/// This type's [`fuchsia.io.Node/Describe`] method returns a socket which is used to transfer data
/// to and from the caller. Signals are used to communicate additional information about the state
/// of the socket such as connectedness and the presence of incoming connections in the case of a
/// listening socket.
///
/// All methods on this type are nonblocking; their exact behaviors match their Linux counterparts.
protocol StreamSocket {
    compose BaseSocket;

    /// Begins listening for new incoming connections. At most `backlog` connections will be
    /// buffered.
    Listen(int16 backlog) -> () error int32;
    /// Accepts a buffered incoming connection.
    Accept(int16 flags) -> (StreamSocket s) error int32;
};

/// Holds information about an interface and its addresses.
table InterfaceAddresses {
    /// ID of the interface.
    1: uint64 id;
    /// Name of the interface.
    2: interface_name name;
    /// Contains the interface flags, as returned by the SIOCGIFFLAGS ioctl
    /// operation.
    3: uint32 flags;
    /// All addresses currently assigned to the interface.
    4: vector<fuchsia.net.Subnet>:MAX addresses;
};

/// Provider implements the POSIX sockets API.
[Discoverable]
protocol Provider {
    /// Requests a socket with the specified parameters. Error values are defined in errno.h.
    Socket2(int16 domain, int16 type, int16 protocol) -> (BaseSocket s) error int32;

    /// Looks up an interface by its index and returns its name. Returns `ZX_ERR_NOT_FOUND` if the
    /// specified index doesn't exist.
    InterfaceIndexToName(uint64 index) -> (interface_name name) error zx.status;
    /// Looks up an interface by its name and returns its index. Returns `ZX_ERR_NOT_FOUND` if the
    /// specified name doesn't exist.
    InterfaceNameToIndex(interface_name name) -> (uint64 index) error zx.status;

    /// Requests a list of [`fuchsia.posix.socket.InterfaceAddresses`]
    /// describing the network interfaces on the system.
    GetInterfaceAddresses() -> (vector<InterfaceAddresses>:MAX interfaces);
};