// Copyright (c) 2014-2016 Robert Clipsham <robert@octarineparrot.com>
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! Support for sending and receiving data link layer packets

extern crate libc;
extern crate ipnetwork;
extern crate pnet_base;
extern crate pnet_sys;

use std::io;
use std::option::Option;
use std::time::Duration;

use ipnetwork::IpNetwork;

pub use pnet_base::{MacAddr, ParseMacAddrErr};

mod bindings;


#[cfg(windows)]
#[path = "winpcap.rs"]
mod backend;

#[cfg(windows)]
pub mod winpcap;

#[cfg(all(not(feature = "netmap"),
          target_os = "linux"
          )
      )]
#[path = "linux.rs"]
mod backend;

#[cfg(target_os = "linux")]
pub mod linux;

#[cfg(all(not(feature = "netmap"),
          any(target_os = "freebsd",
              target_os = "macos")
             )
     )]
#[path = "bpf.rs"]
mod backend;

#[cfg(any(target_os = "freebsd", target_os = "macos"))]
pub mod bpf;

#[cfg(feature = "netmap")]
#[path = "netmap.rs"]
mod backend;

#[cfg(feature = "netmap")]
pub mod netmap;

#[cfg(feature = "pcap")]
pub mod pcap;

pub mod dummy;

/// Type alias for an EtherType.
pub type EtherType = u16;

/// Type of data link channel to present (Linux only)
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub enum ChannelType {
    /// Send and receive layer 2 packets directly, including headers
    Layer2,
    /// Send and receive "cooked" packets - send and receive network layer packets
    Layer3(EtherType),
}

/// A channel for sending and receiving at the data link layer
///
/// NOTE: It is important to always include a catch-all variant in match statements using this
/// enum, since new variants may be added. For example:
///
/// ```ignore
/// match some_channel {
///     Ethernet(tx, rx) => { /* Handle Ethernet packets */ },
///     _ => panic!("Unhandled channel type")
/// }
/// ```
pub enum Channel {
    /// A datalink channel which sends and receives Ethernet packets
    Ethernet(Box<DataLinkSender>, Box<DataLinkReceiver>),

    /// This variant should never be used
    ///
    /// Including it allows new variants to be added to `Channel` without breaking existing code.
    PleaseIncludeACatchAllVariantWhenMatchingOnThisEnum,
}

/// A generic configuration type, encapsulating all options supported by each backend
///
/// Each option should be treated as a hint - each backend is free to ignore any and all
/// options which don't apply to it.
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub struct Config {
    /// The size of buffer to use when writing packets. Defaults to 4096
    pub write_buffer_size: usize,

    /// The size of buffer to use when reading packets. Defaults to 4096
    pub read_buffer_size: usize,

    /// Linux/BPF/Netmap only: The read timeout. Defaults to None.
    pub read_timeout: Option<Duration>,

    /// Linux/BPF/Netmap only: The write timeout. Defaults to None.
    pub write_timeout: Option<Duration>,

    /// Linux only: Specifies whether to read packets at the datalink layer or network layer.
    /// Defaults to Layer2
    pub channel_type: ChannelType,

    /// BPF/OS X only: The number of /dev/bpf* file descriptors to attempt before failing. Defaults
    /// to: 1000
    pub bpf_fd_attempts: usize,
}

impl Default for Config {
    fn default() -> Config {
        Config {
            write_buffer_size: 4096,
            read_buffer_size: 4096,
            channel_type: ChannelType::Layer2,
            bpf_fd_attempts: 1000,
            read_timeout: None,
            write_timeout: None,
        }
    }
}

/// Create a new datalink channel for sending and receiving data
///
/// This allows for sending and receiving packets at the data link layer.
///
/// A list of network interfaces can be retrieved using datalink::interfaces().
///
/// The configuration serves as a hint to the backend - some or all of it may be used or ignored,
/// depending on which backend is used.
///
/// When matching on the returned channel, make sure to include a catch-all so that code doesn't
/// break when new channel types are added.
#[inline]
pub fn channel(network_interface: &NetworkInterface, configuration: Config) -> io::Result<Channel> {
    backend::channel(network_interface, (&configuration).into())
}


/// Trait to enable sending $packet packets
pub trait DataLinkSender: Send {
    /// Create and send a number of packets
    ///
    /// This will call `func` `num_packets` times. The function will be provided with a
    /// mutable packet to manipulate, which will then be sent. This allows packets to be
    /// built in-place, avoiding the copy required for `send`. If there is not sufficient
    /// capacity in the buffer, None will be returned.
    #[inline]
    fn build_and_send(&mut self,
                      num_packets: usize,
                      packet_size: usize,
                      func: &mut FnMut(&mut [u8]))
    -> Option<io::Result<()>>;

    /// Send a packet
    ///
    /// This may require an additional copy compared to `build_and_send`, depending on the
    /// operating system being used. The second parameter is currently ignored, however
    /// `None` should be passed.
    #[inline]
    fn send_to(&mut self,
                packet: &[u8],
                dst: Option<NetworkInterface>)
        -> Option<io::Result<()>>;
}


/// Structure for receiving packets at the data link layer. Should be constructed using
/// datalink_channel().
pub trait DataLinkReceiver: Send {
    #[inline]
    /// Get the next Ethernet frame in the channel
    fn next(&mut self) -> io::Result<&[u8]>;
}


/// Represents a network interface and its associated addresses
#[derive(Clone, PartialEq, Eq, Debug, Hash)]
pub struct NetworkInterface {
    /// The name of the interface
    pub name: String,
    /// The interface index (operating system specific)
    pub index: u32,
    /// A MAC address for the interface
    pub mac: Option<MacAddr>,
    /// IP addresses and netmasks for the interface
    pub ips: Vec<IpNetwork>,
    /// Operating system specific flags for the interface
    pub flags: u32,
}

impl NetworkInterface {
    /// Retrieve the MAC address associated with the interface
    pub fn mac_address(&self) -> MacAddr {
        self.mac.unwrap()
    }

    /// Is the interface a loopback interface?
    pub fn is_loopback(&self) -> bool {
        self.flags & (pnet_sys::IFF_LOOPBACK as u32) != 0
    }
}

/// Get a list of available network interfaces for the current machine.
pub fn interfaces() -> Vec<NetworkInterface> {
    backend::interfaces()
}