Enum Layer 

#[non_exhaustive]
pub enum Layer {
    L2,
    L3,
}

Available on Windows, or Linux and non-target_env=ohos, or macOS, or FreeBSD, or OpenBSD, or NetBSD only.

Represents the OSI layer at which the TUN/TAP interface operates.

This enum determines whether the interface works at the Data Link Layer (L2/TAP) or the Network Layer (L3/TUN).

Layer 2 (TAP) - Data Link Layer

TAP interfaces operate at the Ethernet frame level (Layer 2), handling complete Ethernet frames including MAC addresses. This is useful for:

• Bridging networks
• Emulating full Ethernet connectivity
• Applications requiring MAC-level control
• Creating virtual switches

TAP mode requires setting a MAC address and can work with protocols like ARP.

Platform availability: Windows, Linux, FreeBSD, macOS, OpenBSD, NetBSD

Layer 3 (TUN) - Network Layer

TUN interfaces operate at the IP packet level (Layer 3), handling IP packets directly without Ethernet framing. This is the default and most common mode for:

• VPN implementations
• IP tunneling
• Point-to-point connections
• Routing between networks

TUN mode is simpler and more efficient than TAP when Ethernet-level features are not needed.

Platform availability: All platforms

Examples

Creating a TAP (L2) interface:

use tun_rs::{DeviceBuilder, Layer};

let tap = DeviceBuilder::new()
    .name("tap0")
    .layer(Layer::L2)
    .mac_addr([0x00, 0x11, 0x22, 0x33, 0x44, 0x55])
    .build_sync()?;

Creating a TUN (L3) interface (default):

use tun_rs::{DeviceBuilder, Layer};

// L3 is the default, explicit specification is optional
let tun = DeviceBuilder::new()
    .name("tun0")
    .layer(Layer::L3)
    .ipv4("10.0.0.1", 24, None)
    .build_sync()?;

Platform-Specific Notes

• On macOS, TAP mode uses a pair of feth (fake ethernet) interfaces
• On Windows, TAP mode requires the tap-windows driver
• On Linux, both modes use the kernel TUN/TAP driver
• Android and iOS only support TUN (L3) mode

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

L2

Available on Windows or Linux or FreeBSD or macOS or OpenBSD or NetBSD only.

Data Link Layer (Ethernet frames with MAC addresses).

TAP mode operates at Layer 2, handling complete Ethernet frames. Requires a MAC address to be configured.

Available on: Windows, Linux, FreeBSD, macOS, OpenBSD, NetBSD

L3

Network Layer (IP packets).

TUN mode operates at Layer 3, handling IP packets directly. This is the default and most common mode for VPN and tunneling applications.

Available on: All platforms

Trait Implementations

impl Clone for Layer

fn clone(&self) -> Layer

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Layer

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Layer

fn default() -> Layer

Returns the “default value” for a type.

impl From<Layer> for c_short

Available on Linux and non-target_env=ohos only.

fn from(layer: Layer) -> Self

Converts to this type from the input type.

impl PartialEq for Layer

fn eq(&self, other: &Layer) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Layer

impl Eq for Layer

impl StructuralPartialEq for Layer