[wifi] Add capture.sh

capture.sh is a script to automatically capture a few packets on a Wi-Fi
interface and write them to a Pcap file.

wifi/README

@@ -0,0 +1,4 @@
+capture.sh is a script to automatically capture a few packets on a Wi-Fi
+interface and write them to a compressed Pcap file. This file can then
+be analysed (for example with Wireshark) to check what the interface
+supports.

wifi/capture.sh

@@ -0,0 +1,79 @@
+#!/bin/sh
+#
+# capture.sh, Copyright © 2011 Matteo Cypriani <mcy@lm7.fr>
+#
+########################################################################
+# This program is licensed under the terms of the Expat license.
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+# 
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+# 
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+########################################################################
+#
+# Captures a few packets on a Wi-Fi interface, using Tcpdump, and
+# writes them to a Pcap file.
+
+#set -x
+set -e
+
+error()
+{
+	echo "$1"
+	exit 1
+}
+
+[ $# -eq 1 ] \
+	|| error "Usage: $0 <wifi_interface>"
+
+which tcpdump >/dev/null \
+	|| error "tcpdump is required to run this program!"
+
+IFACE=$1
+FILE=/tmp/capture.pcap
+NB_PKT=10
+
+echo -n "Shuting down interface $IFACE... "
+ifconfig $IFACE down && echo "OK." \
+	|| error "Cannot shut down the interface!"
+
+echo -n "Switching interface $IFACE to monitor mode... "
+case `uname` in
+	Linux)
+		[ -x /sbin/iwconfig ] \
+			|| error "iwconfig is required to run this program on Linux!" ;
+		iwconfig $IFACE mode monitor \
+			&& echo "OK." \
+			|| error "Cannot switch the interface to mode monitor!" ;;
+	*)
+		error "Your OS is not supported." ;;
+esac
+
+echo -n "Turning up interface $IFACE... "
+ifconfig $IFACE up && echo "OK." \
+	|| error "Cannot turn the interface up!"
+
+echo "Capturing $NB_PKT packets..."
+tcpdump -i $IFACE -c $NB_PKT -w $FILE
+echo "Capture file $FILE created."
+
+gzip -9 $FILE
+echo "Capture file compressed to $FILE.gz"
+
+echo
+echo "You can now shut down the interface $IFACE if you want:"
+echo "	ifconfig $IFACE down"