#!/bin/sh
#
# Marta Carbone, Luigi Rizzo
# Copyright (C) 2009 Universita` di Pisa
# $Id$
#
# This script the vsys backend used to configure emulation.
# In detail it:
# - reads the user's input from the vsys input pipe
# - validates the input
# - configures the firewall
# - writes results on the output vsys pipe
#
# Configurable variables are at the beginning

# If HOOK is set the program is called before configuring a rule.
# A sample hook can be found in the ipfwroot.rpm package,
# it can be used to collect statistical information on dummynet usage.
# To configure an hook, set the HOOK variable as follow:
# HOOK=/tmp/sample_hook

# You should not touch anything below.

# We assume three type of connections
#  SERVER we know the local port P, and do the
#	bind/listen/accept on the local socket.
#		pipe_in in dst-port P
#		pipe_out out src-port P
#
#  CLIENT we know the remote port P, and do a connect to it
#	(src and dst are swapped wrt the previous case)
#		pipe_in in src-port P
#		pipe_out out dst-port P
#
#  SERVICE we run a server on local port P, and also connect
#	from local clients to remote servers on port P.
#		pipe_in in { dst-port P or src-port P }
#		pipe_out out { src-port P or dst-port P }
# 
#  On a given port a user can have one CLIENT and/or one SERVER
#  configuration or one SERVICE configuration.
#  When a SERVICE configuration is installed any existing CLIENT
#  and SERVER configuration on the same port are removed.
#  When a CLIENT or SERVER configuration is installed any existing
#  SERVICE configuration on the same port is removed.
#
#  The following is a case that is implemented as SERVER
#  D	we run a server on local port P, and also connect
#	to remote servers but doing a bind(P) before connect().
#	In terms of rules, this is not distinguishable from
#	the SERVER case, however it would be different if we
#	had a way to tell SERVER from CLIENT sockets
#		pipe_in in dst-port P
#		pipe_out out src-port P
#
# The database of current ipfw and dummynet configuration is in a
# file which is regenerated on errors. The format is
#
#	slice_id type arg rule_base pipe_base timeout
#
# (lines starting with '#' are comments and are ignored)
# For each configuration we allocate one rule number in ipfw,
# and two sequential pipe numbers.

# globals, do not touch below
VERBOSE=0	# set to !0 to enable debug messages
TEST=0		# set to 1 for test mode

DBFILE=/tmp/ff
lockfile=/var/lock/ipfw.lock

# These values are the keys used in the database for blocks,
# rules and pipes
# The index rule numbers allocated to a slice can be computed
# with the following formula:
#	index_min_rule = $(($RULE_BASE + $(($M*$block_n))))
# where block_n is the block number associated with the slice
# and M is the block size.
BLOCK_MIN=1
BLOCK_MAX=1000
M=50		# block size
RULE_BASE=10001 # the hightest rule is RULE_BASE + (M*BLOCK_MAX)
PIPE_MIN=1
PIPE_MAX=25000
# These are the actual rule numbers used in ipfw
IPFW_RULE_MIN=10000
IPFW_RULE_MAX=59999
IPFW_PIPE_MIN=10000
IPFW_PIPE_MAX=59999
# The mapping between keys and ipfw configuration number follow:
# rule_nr 10001..20000 are mapped to ipfw_rules 50000..59999 (n+39999)
# pipe_nr 1..25000 are mapped to ipfw_pipes 10000-59999 (n*2+9998)
# Rule index can be mapped to ipfw rules with the following formula:
#	ipfw_rule = $(($index_rule + 39999))
# Pipes index can be mapped to ipfw pipes with:
#	ipfw_pipein = $(($index_pipe + $index_pipe + 9998))
#	ipfw_pipeout = $(($ipfw_pipein + $1))
#
# the skipto and the generic default rule
# these values are used to initialize the firewall
SLICE_TABLE=1		# table number used for slice ids lookup
S=1000			# firewall rule number for the skipto rule
D=2000			# default rule for reserved section

# set slicename and slice_id
# these are the credential of the user invoking the backend
SLICENAME=$1
if [ $SLICENAME = 0 ]; then
	SLICE_ID=0
else
	SLICE_ID=`id -u $SLICENAME`
fi

# programs
# XXX check consistency for variables {}
SED=/bin/sed
SEDOPT=-r
[ -x ${SED} ] || { SED=`which sed` ; SEDOPT=-E ; }
IPFW=/sbin/ipfw
IPFW_CHECK="/sbin/ipfw -n"

debug() { # $1 message to be displayed
	[ x"${VERBOSE}" != x"0" ] && echo "ipfw-be: $1"
}

# if the first argument is -v, enable verbose mode
set_verbose() {
    [ x"$1" = x"-v" -o x"$2" = x"-v" ] && VERBOSE=1
}

set_test() {
    [ x"$1" = x"-q" -o x"$2" = x"-q" ] || return
    TEST=1
    IPFW="/bin/echo ipfw:"
    IPFW_CHECK="/bin/echo ipfw -n:"
}

abort() { # $1 message to be displayed in case of error
	release_lock
	echo "ipfw-be aborting (netconfig help): $1"
	exit 1
}

# remove dangerous characters from user input
# if present, the leading '-v/-t' will be removed
filter() { # $* variables to be filtered
	[ x${1} = x"-v" -o x${1} = x"-q" ] && shift
	[ x${1} = x"-v" -o x${1} = x"-q" ] && shift
	# allowed chars are: numbers, uppercase and lowercase letters,
	# spaces, and the following symbols: .,_-/
	echo "$*" | ${SED} ${SEDOPT} 's/[^\t0-9a-zA-Z., _\/\{}-]*//g'
}

# remove all entries from the ipfw config, and create an empty db
clean_db() {
	rm -f ${DBFILE}
	touch ${DBFILE}
	# we would like to delete ranges of rules and pipes but this
	# is not supported so for the time being we kill them all
	${IPFW} -q flush
	${IPFW} -q pipe flush
	# ${IPFW} delete ${IPFW_RULE_MIN}-${IPFW_RULE_MAX}
	# ${IPFW} pipe delete ${IPFW_PIPE_MIN}-${IPFW_PIPE_MAX}
	# since all rules are now deleted, we should initialize the firewall 
	ipfw_init
}

# Add the ipfw rule/pipe and update the database.
# The pipe-in and pipe_out config are through global variables
# CONFIG_IN CONFIG_OUT because they may be long.
# Other arguments are on the command line
add_rule() { # new_rule type arg rule pipe_base timeout
    local new_rule=$1 type=$2 arg=$3
    local rule_base=$4 pipe_base=$5 timeout=$6
    local pipe_in pipe_out rule_in rule_out check_timeout

    # If we use a profile file, locate the user directory
    # move in the slice root dir XXX todo
    [ "$TEST" != "1" ] && cd /vservers/${SLICENAME}/root
    #echo ${CONFIG_STRING} | ${SED} -e "s/ profile \(.[^ ]\)/ profile \/vservers\/${SLICENAME}\/\1/g"

    # first, call ipfw -n to check syntax, if ok move on and do the action
    pipe_in=$(($pipe_base + $pipe_base + 9998))
    pipe_out=$(($pipe_in + 1))
    local del	# anything to delete ?
    local rule_nr=$(($rule_base + 39999))  # formula for individual rules
    if [ x"$new_rule" != x"0" ] ; then
	case $type in
	server)
	    rule_in="dst-port $arg"
	    rule_out="src-port $arg"
	    del=service
	    ;;
	client)
	    rule_in="src-port $arg"
	    rule_out="dst-port $arg"
	    del=service
	    ;;
	service)
	    rule_in="{ src-port $arg or dst-port $arg }"
	    rule_out="{ src-port $arg or dst-port $arg }"
	    del="cli_ser"
	    ;;
	*)
	    abort "invalid service type $type"
	    ;;
	esac

	rule_in="pipe ${pipe_in} in jail $SLICE_ID ${rule_in} // $type $arg"
	rule_out="pipe ${pipe_out} out jail $SLICE_ID ${rule_out} // $type $arg"
	${IPFW_CHECK} add ${rule_nr} $rule_in > /dev/null || \
		abort "ipfw syntax error $rule_in"
	${IPFW_CHECK} add ${rule_nr} $rule_out > /dev/null || \
		abort "ipfw syntax error $rule_out"
    fi

    # check error reporting
    ${IPFW_CHECK} pipe ${pipe_in} config ${CONFIG_PIPE_IN} > /dev/null || \
		abort "ipfw syntax error pipe_in"
    ${IPFW_CHECK} pipe ${pipe_out} config ${CONFIG_PIPE_OUT} > /dev/null || \
		abort "ipfw syntax error pipe_out"

    # all good, delete and add rules if necessary
    [ "$del" = "service" ] && do_delete $SLICE_ID service $arg
    [ "$del" = "cli_ser" ] && do_delete $SLICE_ID client $arg
    [ "$del" = "cli_ser" ] && do_delete $SLICE_ID server $arg
    [ "$new_rule" != "0" ] && ${IPFW} add ${rule_nr} $rule_in > /dev/null
    [ "$new_rule" != "0" ] && ${IPFW} add ${rule_nr} $rule_out > /dev/null
    # config pipes
    ${IPFW} pipe ${pipe_in} config ${CONFIG_PIPE_IN}
    ${IPFW} pipe ${pipe_out} config ${CONFIG_PIPE_OUT}

    # send output to the user
    ${IPFW} show ${rule_nr}
    ${IPFW} pipe ${pipe_in} show
    ${IPFW} pipe ${pipe_out} show

    [ "$TEST" = "1" ] && return
    # add to the database
    ( grep -v -- "^${SLICE_ID} ${type} ${arg} " $DBFILE;  \
	echo "${SLICE_ID} ${type} ${arg} ${rule_base} ${pipe_base} ${timeout}" ) > ${DBFILE}.tmp
    mv ${DBFILE}.tmp ${DBFILE}
}

# Delete a given configuration
do_delete() { # type arg
    local pipe_in pipe_out pipe_base rule_base rule_nr
    local type=$1 arg=$2

    [ "${type}" = "BLOCK" ] && abort "A Block can not be deleted"
    [ "${arg}" = "" ] && abort "Missing args on 'delete', expected on of {SERVICE|SERVER|CLIENT} port_number"
    set `find_rule $SLICE_ID $type $arg`
    rule_base=$1; pipe_base=$2
    [ "$rule_base" = "0" ] && return		# no rules found

    rule_nr=$(($rule_base + 39999))		# XXX only individual rules
    pipe_in=$(($pipe_base + $pipe_base + 9998))
    pipe_out=$(($pipe_in + 1))

    $IPFW delete ${rule_nr}
    $IPFW pipe delete ${pipe_in}
    $IPFW pipe delete ${pipe_out}
    echo "removed configuration ${SLICE_ID} ${type} ${arg}"
    [ "$TEST" = "1" ] && return
    # remove from the database
    grep -v -- "^${SLICE_ID} ${type} ${arg} " $DBFILE > ${DBFILE}.tmp
    mv ${DBFILE}.tmp ${DBFILE}

    # XXX if the use block is empty
    # remove the table entry from ipfw and from the db
    # not yet implemented
}

# compare the argument with the first two field of
# the database.
# On match returns the block number, otherwise returns 0.
find_block() { # $1 slice_id
    local ret
    ret=`grep -- "^$1 BLOCK " $DBFILE`

    [ x"$ret" = x ] && echo "0" && return	# nothing found
    # ignore multiple matches. If the db is corrupt we are
    # screwed anyways
    set $ret
    echo "$3"
}

# called with the database file as input
# compare the tuple <slice_id type arg> with
# the current firewall configuration. The database contains
# 	slice_id type arg rule_base pipe_base timeout
# On match returns <rule_base pipe_base timeout>
# On non match returns 0 0 0
find_rule() { # $1 slice_id $2 type $3 arg
    local ret
    ret=`grep -- "^$1 $2 $3 " $DBFILE`

    [ x"$ret" = x ] && echo "0 0 0 " && return	# nothing found
    # ignore multiple matches. If the db is corrupt we are
    # screwed anyways
    set $ret
    echo "$4 $5 $6"
}


# Find a hole in a list of numbers within a range (boundaries included)
# The input is passed as a sorted list of numbers on stdin.
# Return a "0" rule if there is no rule free
find_hole() {  # min max
    local min=$1 cand=$1 max=$2 line
    while read line ; do
	[ $line -lt $min ] && continue
        [ $line -ne $cand ] && break		# found
	[ $cand -ge $max ] && cand=0 && break	# no space
        cand=$(($cand + 1))
    done
    echo $cand
}

# returns a free rule and pipe base for client|server|service
# within a block
# Returns r=0 if there are no resources available
allocate_resources() {
    local p r
    # remove comments, extract field, sort
    p=`grep -v '^#' $DBFILE | grep -v BLOCK | awk '{print $5}' | sort -n | \
	find_hole $PIPE_MIN $PIPE_MAX`
    r=`grep -v '^#' $DBFILE | grep -v BLOCK | awk '{print $4}' | sort -n | \
	find_hole $1 $2`
    [ $r = 0 -o $p = 0 ] && r=0 		# no resources available
    echo $r $p
}

#
# execute functions from root context
# can be used from root context as follow:
# echo "super $command $args" | /vsys/ipfw-be 0
do_super() { # $arguments...
	case $1 in
	init)
	    ipfw_init; return 0
	    ;;
	dbcleanup)
	    clean_db; return 0
	    ;;
	*)
	    abort "Invalid super command"
	    ;;
	esac
}

#
# show ipfw rules and pipes filtering on slice_id
# If the first argument is 0 filter rules,
# otherwise filter pipes
do_show() { #$1 show rules or pipes
    local list ipfw_list

    if [ $1 == "0" ]; then
	list=`grep "^$SLICE_ID " $DBFILE | grep -v BLOCK | cut -d " " -f 4`
	for i in $list; do ipfw_list="$ipfw_list $(($i + 39999))"; done
	[ -n "${ipfw_list}" ] && ${IPFW} show $ipfw_list
    else
	# ipfw pipe show does not selectively filter pipes
	# XXX so leave this code commented and show all pipes
	#list=`grep "^$SLICE_ID " $DBFILE | grep -v BLOCK | cut -d " " -f 5`
	# the pipe list is build adding two ipfw pipes for each pipe index
	#for i in $list; do ipfw_list="$ipfw_list $(($i + $i + 9998)) $(($i + $i + 9998 +1)) "; done
	#[ -n "${ipfw_list}" ] && ${IPFW} pipe show $ipfw_list
	${IPFW} pipe show
    fi
}

#
# refresh the rule timeout
do_refresh() { # type arg timeout
    local pipe_in pipe_out pipe_base rule_base rule_nr
    local type=$1 arg=$2 timeout=$3

    debug "do_refresh type: <$type> arg: <$arg> timeout: <$timeout>"
    [ "${type}" = "BLOCK" ] && abort "BLOCK rule not valid"
    [ "${timeout}" = "" ] && abort "Missing args on 'refresh', expected on of {SERVICE|SERVER|CLIENT} port_number"
    set `find_rule $SLICE_ID $type $arg`
    rule_base=$1; pipe_base=$2
    [ "${rule_base}" = "0" ] && debug "no rules found" && return 0		# no rules found

    rule_nr=$(($rule_base + 39999))		# XXX only individual rules
    pipe_in=$(($pipe_base + $pipe_base + 9998))
    pipe_out=$(($pipe_in + 1))
    debug "ipfw rule and pipes value: rule: <$rule_nr> pipe in: <$pipe_in> pipe_out: <$pipe_out>"

    [ "$TEST" = "1" ] && return
    # update the database with the new timeout value
    ( grep -v -- "^${SLICE_ID} ${type} ${arg} " $DBFILE;  \
	echo "${SLICE_ID} ${type} ${arg} ${rule_base} ${pipe_base} ${timeout}" ) > ${DBFILE}.tmp
    mv ${DBFILE}.tmp ${DBFILE}
    echo "refreshed timeout for rule ${type} ${arg}"
}

# process a request.
# A request is made by a set of arguments formatted as follow:
#
# config {server|client|service} arg [-t timeout] PIPE_IN <pipe_conf> PIPE_OUT <pipe_conf>
# show {rules|pipes} [args]
# delete type arg
#
# The timeout value is expressed as:
# week, day, month or anything else accepted by the date command.
# The id of the slice issuing the request is in the $SLICE_ID variable,
# set at the beginning of this script.
process() {
    local new_pipe=0
    local timeout TMP i rule_base pipe_base
    local slicename=${SLICENAME}
    local cmd=$1 ; shift
    local debug_args="$*";
    local type=$1 ; shift
    local args="$*"
    debug "Received command: <$cmd> arguments: <$debug_args>"

    # set the timeout value
    # if present, extract the '-t timeout' substring from the command line
    timeout=`echo ${args} | ${SED} ${SEDOPT} 's/(.+)( -t [a-zA-Z0-9]+ )(.*)/\2/'`
    # if the '-t timeout' is specified, use the user define timeout value
    if [ "${timeout}" != "${args}" ] ; then 	# match
	# remove the '-t ' option
	timeout=`echo ${timeout} | ${SED} ${SEDOPT} 's/-t //'`
	check_timeout ${timeout}	# abort on error
	# clean the arguments
	args=`echo ${args} | ${SED} ${SEDOPT} 's/(.+)( -t [a-zA-Z0-9]+ )(.*)/\1 \3/'`
    else
	# use the default value, no need to check for correctness, no need to clean arguments
	timeout=`date --date="1day" +%s`		# default to 1 day
    fi

    debug "Timeout $timeout"
    # Handle special requests: show and delete
    case x"$cmd" in 
    x"config") 
	[ "$type" = "server" ] && do_config $timeout $type $args && return 0
	[ "$type" = "client" ] && do_config $timeout $type $args && return 0
	[ "$type" = "service" ] && do_config $timeout $type $args && return 0
	abort "'config' should be followed by {server|client|service}"
	;;
    x"delete") 
	do_delete ${SLICE_ID} $type $args
	;;
    x"refresh") 
	do_refresh $type $args $timeout && return 0
	;;
    x"show")
	[ "$type" = "rules" ] && do_show 0 && return 0
	[ "$type" = "pipes" ] && do_show 1 && return 0
	abort "'show' should be followed by {rules|pipes}"
	;;
    x"super")
	[ $SLICE_ID = 0 ] && do_super $type $args && return 0
	abort "no permission for ipfw-be super execution"
	;;
    x"help")
	do_help && return 0
	;;
    *)
	# help XXX to be done
	abort "'command' should be one of {show|config|delete|refresh|release}"
	;;
    esac
}

# validate the timeout
check_timeout() { # timeout
    local tt=`date --date="${1}" +%s`
    [ "$?" != "0" ] && abort "Date format $1 not valid"
}

do_config() { # timeout type arg PIPE_IN pipe_conf PIPE_OUT pipe_conf
    local timeout=$1; shift
    local type=$1; shift
    local arg=$1; shift	# XXX addr not yet implemented

    [ "$1" != "PIPE_IN" ] && abort "Missing addr:port, or PIPE_IN requested"
    shift

    # read pipe in configuration
    i=""
    while [ "$1" != "" -a "$1" != "PIPE_OUT" ] ; do
	i="$i $1"
	shift
    done
    CONFIG_PIPE_IN="$i"		# XXX local ?
    [ "$CONFIG_PIPE_IN" = "" ] && abort "Missing pipe in configuration"

    [ "$1" != "PIPE_OUT" ] && abort "Missing pipe in configuration, or missing PIPE_OUT"
    shift

    # read pipe out configuration
    i=""
    while [ "$1" != "" ] ; do
	i="$i $1"
	shift
    done
    CONFIG_PIPE_OUT="$i"	# XXX local ?
    [ "$CONFIG_PIPE_OUT" = "" ] && abort "Missing pipe out configuration"

    debug "Configuration Required:"
    debug "slice_id: $SLICE_ID"
    debug "type: $type"
    debug "arg: $arg"
    debug "timeout: $timeout"
    debug "PIPE_IN: $CONFIG_PIPE_IN"
    debug "PIPE_OUT: $CONFIG_PIPE_OUT"
    debug "-----------------------"

    # check if the link is already configured
    debug "Search for ${SLICE_ID} ${type} ${arg}"

    set `find_rule ${SLICE_ID} ${type} ${arg}`
    local rule_base=$1
    local pipe_base=$2
    local new_pipe=0

    if [ ! ${rule_base} = "0" ] ; then
	debug "Rule found, just changing the pipe configuration"
	add_rule $new_pipe $type $arg $rule_base $pipe_base $timeout
	hook_call $type $port $rule_base $pipe_base $timeout
	return 0; # link configured, exit
    fi

    debug "link not found, search for a block already allocated to the user"

    # Search if there is a block already allocated to the slice_id
    set `find_block ${SLICE_ID}`
    local block_n=$1
    if [ ${block_n} = "0" ] ; then
	debug "Block not found, allocate a new block"
	# blocks are allocated in sequence, get the first free
	block_n=`grep BLOCK $DBFILE | tail -1 | cut -d " " -f 3`
	if [ -z $block_n ]; then
		block_n=$(($BLOCK_MIN - 1))
	fi
	RULE_IN_MIN=$(($RULE_BASE + $(($M*$block_n))))
	block_n=$(($block_n +1))
	debug "Allocated new block $block_nr to user $SLICE_ID"
	[ $block_n -gt $BLOCK_MAX ] && abort "no block resources available"

	# add the rule into the firewall table.
	# note that the rule number into the table are not database number,
	# so we need to compute the firewall number before the table insertion
	local ipfw_rule_nr=$(($RULE_IN_MIN + 39999))  # XXX formula for individual rules
	debug "Configuring table: <${IPFW_CHECK} table $SLICE_TABLE add ${SLICE_ID} ${ipfw_rule_nr}>"
	${IPFW_CHECK} table $SLICE_TABLE add ${SLICE_ID} ${rule_nr} > /dev/null || \
		abort "ipfw syntax error $rule_out"
	${IPFW} table $SLICE_TABLE add ${SLICE_ID} ${ipfw_rule_nr} > /dev/null

	[ "$TEST" = "1" ] && return
	# add the block declaration to the database
	( grep -v -- "^${SLICE_ID} BLOCK " $DBFILE;  \
		echo "${SLICE_ID} BLOCK ${block_n}" ) > ${DBFILE}.tmp
	mv ${DBFILE}.tmp ${DBFILE}
    else
	debug "Block $block_n found for user $SLICE_ID"
    fi

    RULE_IN_MAX=$(($RULE_BASE + $(($M * $block_n))))
    RULE_IN_MIN=$(($RULE_IN_MAX - $M))
    debug  "Block $block_n, with rules <${RULE_IN_MIN}:${RULE_IN_MAX}>" 
    debug  "Corresponding to ipfw rules <$(($RULE_IN_MIN + 39999)):$(($RULE_IN_MAX + 39999))>"
    debug "where the last rule number belongs to the next slice."

    new_pipe=1
    set `allocate_resources $RULE_IN_MIN $RULE_IN_MAX`
    rule_base=$1; pipe_base=$2

    [ $rule_base = 0 ] && abort "no resources available"
    debug "found free resources rule: $rule_base pipe: $pipe_base"

    add_rule $new_pipe $type $arg $rule_base $pipe_base $timeout
    hook_call $type $port $rule_base $pipe_base $timeout
}

#
# acquire the lock XXX check lockfile
acquire_lock() {
    [ "$TEST" = 1 ] && return
    lockfile -s 0 -r 0 $lockfile 2> /dev/null
    if [ $? -ne 0 ] ; then
	echo "lock acquisition failed"
	exit -1
    fi
}

#
# release the lock
release_lock() {
    rm -f $lockfile
}

#
# initialize the firewall with PlanetLab default rules
ipfw_init() {
	${IPFW} add $S skipto tablearg lookup jail $SLICE_TABLE
	${IPFW} add $D allow all from any to any
}

#
# if present, call a hook function
# Arguments are:
# slice_id type port rule_base pipe_base timeout
hook_call() {
	if [ -n "${HOOK}" -a -x "${HOOK}" ]; then
		${HOOK} ${SLICE_ID} "$*" &
	fi
}

do_help() {
	cat << EOF
Usage:
        ./neconfig [SERVER|CLIENT|SERVICE] port [-t timeout]    \
                PIPE_IN <pipe in configuration> PIPE_OUT <pipe out configuration>
        ./netconfig show [rules|pipes]
        ./netconfig delete [SERVER|CLIENT|SERVICE] port
        ./netconfig refresh [-t timeout] [SERVER|CLIENT|SERVICE] port

We assume three type of connections
  SERVER we know the local port P, and do the
       bind/listen/accept on the local socket.
               pipe_in in dst-port P
               pipe_out out src-port P

  CLIENT we know the remote port P, and do a connect to it
       (src and dst are swapped wrt the previous case)
               pipe_in in src-port P
               pipe_out out dst-port P

  SERVICE we run a server on local port P, and also connect
       from local clients to remote servers on port P.
               pipe_in in { dst-port P or src-port P }
               pipe_out out { src-port P or dst-port P }

  On a given port a user can have one CLIENT and/or one SERVER
  configuration or one SERVICE configuration.
  When a SERVICE configuration is installed any existing CLIENT
  and SERVER configuration on the same port are removed.
  When a CLIENT or SERVER configuration is installed any existing
  SERVICE configuration on the same port is removed.

The pipe configuration, both for the upstream and downstream link,
follow the dummynet syntax. A quick and not exaustive example
of the parameters that can be used to configure the delay,
the bandwidth and the packet loss rate for a link follow:

        PIPE_IN|PIPE_OUT delay 100ms bw 1Mbit/s plr 0.1

The full documentation is on the manpage[1].

The timeout value follow the linux 'date' command format[2]
and can be specified as follow:
        1week
        2hours
        3days

--- References:
[1] http://www.freebsd.org/cgi/man.cgi?query=ipfw
[2] http://linuxmanpages.com/man1/date.1.php
EOF
}

# ALLOCATION OF RULES AND PIPES
# The ruleset is composed by different sections, as follow:
# - a first set of rules is reserved and is configurable by
#   the root context only;
# - the skipto rule (S), used to optimize the slice rule search;
# - a second block of reserved rules;
# - a default (D) rule for the generic configuration;
# - the slice reserved rules, a block of M rules for each slice;
# - the firewall default rule.
#
# To summarize:
#	1...S-1	first block of reserved rules
#	S	skipto tablearg lookup jail 1
#	S+1..D-1 ... second block of reserved rules
#	D	allow ip from any to any
#
#	RULE_BASE <block of M entries for first user>
#	RULE_BASE+M <block of M entry for second user ...>
#	...
#
# Out of 64k rules, we allocate a block of M=50 consecutive
# rules to each slice using emulation. Within this block,
# each configuration uses one rule number and two pipes.
#
# Pipes are allocated starting from PIPE_BASE, a couple
# of pipes for each configuration.
#
# DATABASE FORMAT
# The database is stored on a file, and contains
# one line per record with this general structure
#	XID	TYPE	arg1	arg2	...
# whitespace separates the fields. arg1, arg2, ...
# have different meaning depending on the type.
#
# In the database we have the following records:
# - one entry for each slice that has active emulation entries.
#   For each of these slices we reserve a block of M ipfw rules
#   starting at some RULE_BASE rule number.
#   The database entry for this info has the form
#	XID	BLOCK	block_number
#   where blocks are numbered sequentially from 1.
#   The actual rule number is RULE_BASE + M*(block_number)
#   (we don't care if we waste some rules)
#
# - one entry for each predefined config (CLIENT, SERVER, SERVICE).
#   The database entry for this info has the form
#	XID	{CLIENT|SERVER|SERVICE}	arg	rule_nr pipe_index
#   rule_nr is the absolute rule number for this configuration
#   (it must be within the block of M rules allocated to the slice)
#   pipe_index is the index of the couple of pipes used for the
#   configuration. pipe_index starts from 1.
#

#-- main starts here
debug "--- $0 START for $SLICENAME ---"

# If the db does not exist, create it and we clean rules and pipes
[ ! -e ${DBFILE} ] && clean_db

# A request to the vsys backend is composed by a single line of input
read REQ			# read one line, ignore the rest
set_verbose ${REQ}		# use inital -v if present
set_test ${REQ}		# use inital -t if present
REQ="`filter ${REQ}`"	# remove -v and -t and invalid chars
debug "--- processing <${REQ}>"
acquire_lock			# critical section
process ${REQ}
release_lock
debug "--- $0 END ---"
exit 0