#!/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 along with some information about the
# system. A tarball containing all these files is finally created.

#set -x
set -e

# Displays the message in argument and exits
error()
{
	echo "$1"
	exit 1
}

# Switches the capture interface on the channel in argument
set_channel()
{
	echo -n "Setting interface $IFACE on channel $1... "
	case $OS in
		Linux)
			[ -x /sbin/iwconfig ] \
				|| error "iwconfig is required to run this program on Linux!"
			iwconfig $IFACE channel $1
			;;
		NetBSD)
			ifconfig $IFACE chan $1
			;;
		*)
			error "Your OS is not supported."
			;;
	esac \
		&& echo "OK." \
		|| error "Cannot set the channel!"
}

# Invokes tcpdump and returns the number of packets captured
invoke_tcpdump()
{
	return $(tcpdump -i $IFACE -c $NB_PKT -w "$FILE" 2>&1 \
		| sed -n 's/ packets captured$//p')
}

# Waits for a number of seconds, then kills any tcpdump process
wait_tcpdump()
{
	sleep $1
	pkill tcpdump
}

[ $# -eq 1 ] \
	|| error "Usage: $0 <wifi_interface>"

which tcpdump >/dev/null \
	|| error "tcpdump is required to run this program!"

## Parameters (tune them if you want) ##
# Number of packet to capture:
NB_PKT=10
# Maximal time of a capture on a given channel:
TIMEOUT=15
# Temporary directory:
TMP=/tmp
# Name of the capture file:
FILE=capture.pcap
# First channel to scan:
CHANNEL=1

## Generated parameters ##
# Interface to capture from:
IFACE=$1
# Machine information:
OS=`uname`
OS_RELEASE=`uname -r`
HOSTNAME=`uname -n`
# Current date:
DATE=`date +%FT%H%M%S`

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 $OS in
	Linux)
		[ -x /sbin/iwconfig ] \
			|| error "iwconfig is required to run this program on Linux!"
		iwconfig $IFACE mode monitor
		;;
	NetBSD)
		ifconfig $IFACE media autoselect mediaopt monitor
		;;
	*)
		error "Your OS is not supported."
		;;
esac \
	&& echo "OK." \
	|| error "Cannot configure the interface!"

echo -n "Turning up interface $IFACE... "
ifconfig $IFACE up && echo "OK." \
	|| error "Cannot turn the interface up!"

echo "Trying to capture $NB_PKT packets..."
DIR=$(mktemp -d \
	"$TMP"/capture_${OS}-${OS_RELEASE}_${IFACE}_${HOSTNAME}_${DATE}_XX)
FILE="$DIR/$FILE"
CAPTURED=0
while [ $CAPTURED -eq 0 -a $CHANNEL -le 14 ] ; do
	set_channel $CHANNEL
	wait_tcpdump $TIMEOUT &
	invoke_tcpdump
	CAPTURED=$?
	[ $CAPTURED -eq 0 ] \
		&& echo "No packet captured on channel $CHANNEL."
	CHANNEL=`expr $CHANNEL + 1`
done

[ $CAPTURED -gt 0 ] \
	&& echo "Capture file \"$FILE\" created with $CAPTURED packets." \
	|| error "Failed to capture any packet!"

echo -n "Gathering system information... "
# Kernel & other information:
uname -a >"$DIR"/uname-a
# Wi-Fi interface information:
ifconfig $IFACE >"$DIR"/ifconfig_$IFACE
# PCI devices:
which lspci >/dev/null \
	&& lspci >"$DIR"/lspci \
	|| echo "lspci not available! Please install pciutils. "
# Loaded kernel modules & USB devices:
case $OS in
	Linux)
		lsmod >"$DIR"/lsmod
		which lsusb >/dev/null \
			&& lsusb >"$DIR"/lsusb \
			|| echo "lsusb not available! Please install usbutils. "
		;;
	NetBSD)
		modstat >"$DIR"/modstat
		which usbstats >/dev/null \
			&& usbstats >"$DIR"/usbstats \
			|| echo "usbstats not available! Please install usbutil. "
		;;
	DragonFly)
		kldstat >"$DIR"/kldstat
		which usbstats >/dev/null \
			&& usbstats >"$DIR"/usbstats \
			|| echo "usbstats not available! Please install usbutil. "
		;;
esac
echo "OK."

FILE="${DIR}.tar.gz"
DIR=`basename "$DIR"`
tar -C "$TMP" -czf "$FILE" "$DIR"
echo "Archive \"$FILE\" created."
rm -fr "$TMP/$DIR"

echo
echo "You can now shut down the interface $IFACE if you want:"
echo "	ifconfig $IFACE down"