netmap-min-sys

This crate provides low-level FFI (Foreign Function Interface) bindings to the Netmap C library. Netmap is a framework for very fast packet I/O from userspace.

netmap-min-sys is a "sys" crate, meaning it primarily handles the C library linking and exposes raw, unsafe bindings. Higher-level, safe abstractions are provided by the netmap-rs crate, which depends on this one.

Prerequisites

To compile and use this crate (and by extension, netmap-rs with its sys feature), you must have the Netmap C library and its development headers installed on your system.

This typically involves:

1. Installing Netmap: Follow the instructions from the official Netmap project or its GitHub repository (netmap/netmap) to compile and install the Netmap kernel module, libraries, and headers for your operating system.
2. Installing Clang: The bindgen tool, used by this crate's build script to generate Rust bindings from C headers, requires clang to be installed. (e.g., sudo apt install clang libclang-dev on Debian/Ubuntu).

Build Configuration

The build script (build.rs) for netmap-min-sys attempts to locate your Netmap installation.

Standard Installation

If Netmap is installed in a standard system location (e.g., headers in /usr/include or /usr/local/include, and libraries in /usr/lib or /usr/local/lib), the build script should generally find it automatically. It defaults to checking /usr/local if no other hints are provided. The build.rs script was updated to explicitly pass the include path ${NETMAP_LOCATION}/include (or the default /usr/local/include) to bindgen.

Custom Netmap Installation Path (NETMAP_LOCATION)

If you have installed Netmap in a non-standard directory, you must inform the build script by setting the NETMAP_LOCATION environment variable before building your project. Set this variable to the root directory of your Netmap installation (i.e., the directory that contains the include and lib subdirectories for Netmap).

Example:

If Netmap is installed in /opt/netmap (so headers are in /opt/netmap/include and libraries in /opt/netmap/lib), you would build your project like this:

NETMAP_LOCATION=/opt/netmap cargo build

The build script will then:

• Instruct bindgen to look for headers in $NETMAP_LOCATION/include (e.g., /opt/netmap/include).
• Instruct the linker to look for libraries in $NETMAP_LOCATION/lib (e.g., /opt/netmap/lib).

Disabling Netmap Kernel Integration (DISABLE_NETMAP_KERNEL)

For compilation on platforms where Netmap is not supported or available (e.g., macOS, Windows), or if you wish to compile netmap-rs without actual Netmap functionality (perhaps for using only its fallback mechanisms if any are fully independent), you can set the DISABLE_NETMAP_KERNEL environment variable.

DISABLE_NETMAP_KERNEL=1 cargo build

If this variable is set, the build script will:

• Skip the bindgen process.
• Generate an empty binding.rs file.
• Not attempt to link against the Netmap library.

This allows the crate (and netmap-rs) to compile, but any attempt to use Netmap-specific functions will likely fail or be unavailable.

Usage

This crate is not typically used directly. Instead, the netmap-rs crate provides safe Rust abstractions over the raw bindings exposed here. If you are using netmap-rs, ensure its sys feature is enabled, which will correctly pull in and configure this -sys crate.

License

• Apache License, Version 2.0, (LICENSE-APACHE).
• MIT license (LICENSE-MIT).