rustflow_export 0.16.0

use anyhow::Result;

#[cfg(target_os = "linux")]
mod af_packet;
#[cfg(any(feature = "pcap", target_os = "macos"))]
mod libpcap;

/// Where the bytes of a frame start.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Link {
    Ethernet,
    /// No link header: the bytes start at the IP header.
    Ip,
}

/// A captured frame, borrowed from the backend until the next read.
pub struct Frame<'a> {
    /// The bytes captured, cut at the snap length.
    pub data: &'a [u8],
    /// The length of the frame on the wire.
    pub length: u32,
}

pub trait Capture {
    /// The link type of every frame this capture yields.
    fn link(&self) -> Link;

    /// Waits up to about a second for a frame, so the caller keeps
    /// servicing its timers on an idle link.
    fn next_frame(&mut self) -> Option<Frame<'_>>;
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, clap::ValueEnum)]
pub enum Backend {
    /// The native backend of this platform
    Auto,
    /// AF_PACKET mmap ring (Linux only)
    AfPacket,
    /// libpcap / Npcap
    Pcap,
}

pub fn open(backend: Backend, interface: &str, promiscuous: bool) -> Result<Box<dyn Capture>> {
    match backend {
        Backend::Auto if cfg!(target_os = "linux") => open_af_packet(interface, promiscuous),
        Backend::Auto | Backend::Pcap => open_pcap(interface, promiscuous),
        Backend::AfPacket => open_af_packet(interface, promiscuous),
    }
}

#[cfg(target_os = "linux")]
fn open_af_packet(interface: &str, promiscuous: bool) -> Result<Box<dyn Capture>> {
    Ok(Box::new(af_packet::AfPacket::new(interface, promiscuous)?))
}

#[cfg(not(target_os = "linux"))]
fn open_af_packet(_: &str, _: bool) -> Result<Box<dyn Capture>> {
    anyhow::bail!("The af-packet capture backend requires Linux; use --capture pcap")
}

#[cfg(any(feature = "pcap", target_os = "macos"))]
fn open_pcap(interface: &str, promiscuous: bool) -> Result<Box<dyn Capture>> {
    Ok(Box::new(libpcap::Libpcap::new(interface, promiscuous)?))
}

#[cfg(not(any(feature = "pcap", target_os = "macos")))]
fn open_pcap(_: &str, _: bool) -> Result<Box<dyn Capture>> {
    anyhow::bail!("This build has no pcap support; rebuild with `--features pcap`")
}