# `Linx.Netlink`
[🔗](https://github.com/oshlabs/linx/blob/v0.2.0/lib/linx/netlink.ex#L1)

Netlink for Elixir — a client for the Linux kernel's `AF_NETLINK` interface.

Netlink is how userspace talks to many kernel subsystems: the networking
stack (rtnetlink), and — through generic netlink — WireGuard, nl80211 and
more. `Linx.Netlink` speaks it directly, encoding and decoding messages in
Elixir; a small NIF handles the one thing the BEAM cannot do safely on its
own — entering another network namespace.

The library is layered, lower layers ignorant of higher ones:

  * `Linx.Netlink.Socket` — an `AF_NETLINK` socket in a chosen network
    namespace, for any netlink protocol family.
  * `Linx.Netlink.Message` / `Linx.Netlink.Attr` — the pure wire codec: the
    `nlmsghdr` envelope and the type-length-value attributes inside it.
  * `Linx.Netlink.Request` — sends a request and collects the kernel's
    reply, including multipart dumps.
  * `Linx.Netlink.Constants` — the core netlink constants every family
    shares.
  * `Linx.Netlink.Codec` — a DSL for declaring a message's wire format; the
    per-family codecs are built with it.

Each protocol family then lives in its own namespace. The first is
rtnetlink — the kernel's networking interface — under `Linx.Netlink.Rtnl`.

## Example

    # List the host's network interfaces.
    {:ok, sock} = Linx.Netlink.Rtnl.open()
    {:ok, links} = Linx.Netlink.Rtnl.Link.list(sock)
    :ok = Linx.Netlink.Socket.close(sock)

## Protocol families

Two protocol families are supported: **rtnetlink** (`Linx.Netlink.Rtnl` —
links, addresses, routes, neighbours, rules) and **nfnetlink**
(`Linx.Netlink.Nfnl` — the transport under `Linx.Netfilter`). The
wire layers (`Socket`, `Message`, `Attr`, `Request`, `Codec`) are
family-agnostic and shared across both. A concurrent-request
connection process, a multicast monitor, and generic netlink
(`NETLINK_GENERIC`) are future work.

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*Consult [api-reference.md](api-reference.md) for complete listing*