#!/bin/sh

. /usr/share/libubox/jshn.sh

PIDFILE="/var/run/packet_capture.pid"
WORKDIR="/var/run/packet_capture"
FILTERFILE="$WORKDIR/tcpdump_filter"
PCAPFILE="$WORKDIR/capture.pcap"

if [ -f "$PIDFILE" ]; then
    echo "error: Packet capture is running"
    exit 1
fi

mkdir -p "$WORKDIR"
chmod 0700 "$WORKDIR"

json_load "$1"
json_get_var interface interface
json_get_var filter filter
json_get_var duration duration
json_get_var packets packets
json_get_var verbose verbose
json_get_var domains domains
json_get_var file file

args="-n"

if [ "$domains" = "1" ];then
	args=""
fi

if  [ -n "$interface" ];then
	case "$interface" in
		*[!A-Za-z0-9_.:-]*)
			echo "error: Incorrect format of an interface"
			exit 1
		;;
	esac
	ip a show "$interface" > /dev/null 2>&1
	if [ "$?" -ne 0 ]; then
        echo "error: Incorrect format of an interface"
        exit 1
    fi

	args="$args -i $interface"
fi

if [ -n "$packets" ];then
    echo "$packets" | egrep '^[0-9]+$' >/dev/null
    if [ "$?" -eq 0 ];then
        args="$args -c $packets"
    else
        echo "error: Incorrect packets argument"
        exit 1
    fi
fi

if [ -n "$duration" ];then
	echo "$duration" | egrep '^[0-9]+$' >/dev/null
	if [ "$?" -ne 0 ];then
		echo "error: Incorrect duration argument"
		exit 1
	fi
fi

if [ "$verbose" = "1"  ];then
	args="$args  -e"
fi

if [ "$file" = "1" ];then
	mem=$(awk '/MemTotal/ {print $2}' /proc/meminfo)
	args="$args -W 2 -C $((mem/(1024 * 10))) -w $PCAPFILE -z /usr/libexec/packet_capture_stop"
fi

if [ -n "$filter" ];then
    tcpdump -i lo -d "$filter" >/dev/null 2>/dev/null
	if [ $? -eq 1 ];then
		echo "error: Incorrect filter argument"
		exit 1
	fi
	( umask 077; printf '%s\n' "$filter" > "$FILTERFILE" )
fi

(/usr/libexec/packet_capture "$args" "$duration")&

echo $! > /var/run/packet_capture.pid

exit 0