Add mac-telnet - a layer 2 Telnet/SSH server useful to access bricked devices

This package adds the mac-telnet server, client, ping and discovery utilities.
See https://github.com/aouyar/MAC-Telnet for details.

This package uses the fork from https://github.com/jow-/MAC-Telnet as source,
the code there has a number of bugfixes and results in smaller binaries since
most core functionality has been ported to libubox facilities provided by
OpenWrt.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

net/mac-telnet/files/mactelnet.config

@@ -0,0 +1,9 @@
+# Global settings for MAC-Telnet daemon
+config mactelnetd
+	option sshmode '0'
+	list interface 'lan'
+
+# Define a MAC-Telnet login, multiple login sections allowed
+config login
+	option username 'root'
+	option password 'secret'

net/mac-telnet/files/mactelnet.init

@@ -0,0 +1,80 @@
+#!/bin/sh /etc/rc.common
+# Copyright (C) 2014 OpenWrt.org
+
+START=60
+
+USE_PROCD=1
+
+PROG=/usr/sbin/mactelnetd
+USERS=/var/etc/mactelnetd.users
+SSHMODE=0
+
+add_account() {
+	local cfg="$1"
+	local user pass
+
+	[ $SSHMODE -eq 0 ] || {
+		[ -n "$already_warned" ] || {
+			echo "mactelnet.$cfg: login sections ignored in SSH mode" >&1
+			already_warned=1
+		}
+		return
+	}
+
+	config_get username "$cfg" username
+	config_get password "$cfg" password
+
+	[ -n "$username" ] || {
+		echo "mactelnet.$cfg: username missing" >&2
+		return
+	}
+
+	[ -n "$password" ] || {
+		echo "mactelnet.$cfg: password missing" >&2
+		return
+	}
+
+	echo "$username:$password" >> $USERS
+}
+
+add_interface() {
+	local iface="$1"
+	local device
+
+	[ -n "$iface" ] || return
+
+	if network_get_physdev device "$iface"; then
+		procd_append_param command -i "$device"
+	fi
+
+	procd_add_reload_interface_trigger "$iface"
+}
+
+add_globals() {
+	local cfg="$1"
+
+	config_get_bool SSHMODE "$cfg" sshmode 0
+	[ $SSHMODE -eq 0 ] || procd_append_param command -S
+
+	config_list_foreach "$cfg" interface add_interface
+}
+
+start_service() {
+	. /lib/functions/network.sh
+
+	procd_open_instance
+
+	procd_add_reload_trigger mactelnet
+	procd_set_param command "$PROG" -f
+
+	config_load mactelnet
+	config_foreach add_globals mactelnetd
+
+	[ $SSHMODE -eq 1 ] || {
+		rm -f $USERS
+		config_foreach add_account login
+	}
+
+	procd_close_instance
+}
+