tools/netconsole: new script for working with netconsole over UDP

While the doc/README.NetConsole does have a snippet for people to
create their own netcat script, it's a lot easier to make a simple
dedicated script and tell people to use it.

Also spruce it up a bit to make it user friendly.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

doc/README.NetConsole

@@ -22,21 +22,11 @@ For example, if your server IP is 192.168.1.1, you could use:
 
 On the host side, please use this script to access the console:
 
-+++++++++++++++++++++++++++++++++++++++++++
-#! /bin/bash
-
-[ $# = 1 ] || { echo "Usage: $0 target_ip" >&2 ; exit 1 ; }
-TARGET_IP=$1
+	tools/netconsole <ip> [port]
 
-stty -icanon -echo intr ^T
-nc -u -l -p 6666 < /dev/null &
-nc -u ${TARGET_IP} 6666
-stty icanon echo intr ^C
-+++++++++++++++++++++++++++++++++++++++++++
-
-The script expects exactly one argument, which is interpreted as  the
-target IP address (or host name, assuming DNS is working). The script
-can be interrupted by pressing ^T (CTRL-T).
+The script uses netcat to talk to the board over UDP.  It requires you to
+specify the target IP address (or host name, assuming DNS is working). The
+script can be interrupted by pressing ^T (CTRL-T).
 
 Be aware that in some distributives (Fedora Core 5 at least)
 usage of nc has been changed and -l and -p options are considered

tools/netconsole

+#!/bin/sh
+
+usage() {
+	(
+	echo "Usage: $0 <board IP> [board port]"
+	echo ""
+	echo "If port is not specified, '6666' will be used"
+	[ -z "$*" ] && exit 0
+	echo ""
+	echo "ERROR: $*"
+	exit 1
+	) 1>&2
+	exit $?
+}
+
+while [ -n "$1" ] ; do
+	case $1 in
+		-h|--help) usage;;
+		--)        break;;
+		-*)        usage "Invalid option $1";;
+		*)         break;;
+	esac
+	shift
+done
+
+ip=$1
+port=${2:-6666}
+
+if [ -z "${ip}" ] || [ -n "$3" ] ; then
+	usage "Invalid number of arguments"
+fi
+
+for nc in netcat nc ; do
+	type ${nc} >/dev/null && break
+done
+
+trap "stty icanon echo intr ^C" 0 2 3 5 10 13 15
+echo "NOTE: the interrupt signal (normally ^C) has been remapped to ^T"
+
+stty -icanon -echo intr ^T
+${nc} -u -l -p ${port} < /dev/null &
+exec ${nc} -u ${ip} ${port}