Factor common RAW AF_PACKET socket pattern

Move recurring raw socket recieve and send
pattern in a common place.

Signed-off-by: Ashwani Kumar Kamal <ashwanikamal.im421@gmail.com>

Author: sneaky-potato

examples/lldpd.lua

@@ -4,7 +4,7 @@
 --
 
 -- Daemon to send LLDP frames on given interface
-local socket = require("socket")
+local raw    = require("socket.raw")
 local linux  = require("linux")
 local thread = require("thread")
 
@@ -36,8 +36,7 @@ local config = {
 local ethertype = string.pack(">H", ETH_P_LLDP)
 
 local function get_src_mac(ifindex)
-	local rx <close> = socket.new(socket.af.PACKET, socket.sock.RAW, ETH_P_ALL)
-	rx:bind(string.pack(">H", ETH_P_ALL), ifindex)
+	local rx <close> = raw.bind(ETH_P_ALL, ifindex)
 	local frame = rx:receive(2048)
 	return frame:sub(7, 12)
 end
@@ -77,11 +76,11 @@ end
 local ifindex = linux.ifindex(config.interface)
 
 local src_mac = get_src_mac(ifindex)
+print(string.format("lldpd got src mac = %s", src_mac))
 local lldp_frame = build_lldp_frame(src_mac)
 
 local function worker()
-	local tx <close> = socket.new(socket.af.PACKET, socket.sock.RAW, ETH_P_LLDP)
-	tx:bind(ifindex)
+	local tx <close> = raw.bind(ETH_P_LLDP, ifindex)
 
 	while (not shouldstop()) do
 		tx:send(lldp_frame)

examples/tap.lua

@@ -4,19 +4,15 @@
 --
 
 local device = require("device")
-local socket = require("socket")
+local raw    = require("socket.raw")
 local linux  = require("linux")
 
-local PACKET    = socket.af.PACKET
-local RAW       = socket.sock.RAW
-local ETH_P_ALL = 0x0003
 local MTU       = 1500
 
 local s = linux.stat
 local tap = {name = "tap", mode = s.IRUGO}
 
-local socket = socket.new(PACKET, RAW, ETH_P_ALL)
-socket:bind(string.pack(">I2", ETH_P_ALL))
+local socket = raw.bind()
 
 function tap:read()
 	local frame = socket:receive(MTU)

lib/socket/raw.lua

@@ -0,0 +1,43 @@
+--
+-- SPDX-FileCopyrightText: (c) 2025 Ashwani Kumar Kamal <ashwanikamal.im421@gmail.com>
+-- SPDX-License-Identifier: MIT OR GPL-2.0-only
+--
+
+---
+-- RAW AF_PACKET socket operations.
+-- This module provides a higher-level abstraction over the `socket` module.
+--
+-- @module socket.raw
+-- @see socket
+--
+local socket = require("socket")
+
+local af   = socket.af
+local sock = socket.sock
+
+local ETH_P_ALL  = 0x0003
+
+local raw = {}
+
+local function new(method)
+	raw[method] = function (proto, ifindex)
+		local proto = proto or ETH_P_ALL
+		local ifindex = ifindex or 0
+		local s = socket.new(af.PACKET, sock.RAW, proto)
+		s:bind(string.pack(">H", proto), ifindex)
+		return s
+	end
+end
+
+---
+-- Creates and binds a raw packet socket for receiving and sending frames.
+-- @param proto (number) EtherType (defaults to ETH_P_ALL).
+-- @param ifindex (number) Interface index.
+-- @return A new raw packet socket bound for RX.
+-- @raise Error if socket.new() or socket.bind() fail.
+-- @see socket.new
+-- @see socket.bind
+new("bind")
+
+return raw
+