/etc/init.d/iptables-persistent rc.4

#!/bin/sh
#   Written by Simon Richter <sjr@debian.org>
#   Modified by Jonathan Wiltshire <jmw@debian.org>
#       with help from Christoph Anton Mitterer
#   Modified by Konstantin Demin <rockdrilla@gmail.com>
#       with God willing

### BEGIN INIT INFO
# Provides:          iptables-persistent
# Required-Start:    mountkernfs $local_fs
# Required-Stop:     $local_fs
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# X-Start-Before:    $network
# X-Stop-After:      $network
# Short-Description: Set up iptables rules
# Description:       Loads/saves current iptables rules from/to /etc/iptables
#                    to provide a persistent rule set during boot time
### END INIT INFO

NAME=iptables-persistent
RULES=/etc/iptables/rules
RULES_set=${RULES}.ipset
RULES_v4=${RULES}.ipv4
RULES_v6=${RULES}.ipv6


export PATH=/sbin:/bin
. /lib/lsb/init-functions

# partial /bin/which realization
# only checks if binary exists
binary_exist() {
    IFS_BAK=${IFS} IFS=':' notfound=1

    # if PATH ends with ':' then search in current directory too (IFS hack)
    case "${PATH}" in
    *[!:]:) PATH="${PATH}:" ;;
    esac

    case "$1" in
    */*)
        binary_exist_h "$1" && notfound=0
    ;;
    *)
        for location in ${PATH}; do
            test -z "${location}" && location=.
            binary_exist_h "${location}/$1" && notfound=0 && break
        done
    ;;
    esac
    IFS=${IFS_BAK}
    return ${notfound}
}
binary_exist_h() { test -f "$1" && test -x "$1"; }

load_module() {
    module=
    case "$1" in
    ipset)  module=ip_set          ;;
    ipv4)   module=iptable_filter  ;;
    ipv6)   module=ip6table_filter ;;
    *)      return 2 ;;
    esac

    modprobe -q ${module}
    return 0
}

# keep in sync with test_avail()
init_avail() {
    for subsys in ipset ipv4 ipv6; do
        case "${subsys}" in
        ipset)
            dirs='/sys/module/ip_set '
            files=
            binaries='ipset '
        ;;
        ipv4)
            dirs=
            files='/proc/net/ip_tables_names '
            binaries='iptables iptables-restore iptables-save '
        ;;
        ipv6)
            dirs=
            files='/proc/net/ip6_tables_names '
            binaries='ip6tables ip6tables-restore ip6tables-save '
        ;;
        *) continue ;; # this may not happen at all.
        esac

        load_module ${subsys}

        for flavour in K U; do
            err=0
            case "${flavour}" in
            K)  for i in ${dirs}; do test -d $i || err=1; done
                for i in ${files}; do test -e $i || err=1; done
            ;;
            U)  for i in ${binaries}; do binary_exist $i || err=1; done
            ;;
            *)  continue ;; # this may not happen at all.
            esac

            eval "avail_${subsys}_${flavour}() { return ${err};}"
        done
    done

    return 0
}

test_avail() {
    subsys=$1 flavour=
    case "$2" in
    kernel)  flavour=K ;; # kernel-space
    *)       flavour=U ;; # user-space
    esac

    case "${subsys}" in
    ipset|ipv4|ipv6) ;;
    *) return 2 ;;
    esac

    eval "avail_${subsys}_${flavour}"
}

m_ok='[ok]'
m_err='{ERROR}'
m_skip='[skip]'
m_skip_kernel='[skip: no kernel modules]'
m_skip_user='[skip: no userspace bin]'
m_skip_rules='[skip: no rules]'

load_rules() {
    log_begin_msg "${NAME} loading rules:"

    subsystems='ipset ipv4 ipv6'
    test $# -ne 0 && subsystems=$@

    c_total=0 c_success=0
    for i in ${subsystems}; do
        c_total=$((c_total+1))

        title= cmd= file=
        case "$i" in
        ipset)  title=IPset  cmd=load_rules_ipset  file=${RULES_set} ;;
        ipv4)   title=IPv4   cmd=load_rules_ipv4   file=${RULES_v4}  ;;
        ipv6)   title=IPv6   cmd=load_rules_ipv6   file=${RULES_v6}  ;;
        *)
            log_progress_msg " $i[unrecognized]"
            continue
        ;;
        esac

        log_progress_msg "${title}"

        if ! test_avail $i kernel; then
            log_progress_msg "${m_skip_kernel}"
            continue
        fi

        if ! test_avail $i user; then
            log_progress_msg "${m_skip_user}"
            continue
        fi

        if ! test -f ${file}; then
            log_progress_msg "${m_skip_rules}"
            continue
        fi

        ${cmd} < ${file}

        if test $? -ne 0; then
            log_progress_msg "${m_err}"
        else
#           log_progress_msg "${m_ok}"
            c_success=$((c_success+1))
        fi
    done; unset subsystems i title cmd file

    rc=0 # success
    test ${c_success} -lt ${c_total} && rc=255 # warning
    test ${c_success} -eq 0          && rc=1 # failure
    unset c_total c_success

    log_end_msg ${rc}; unset rc
    return 0
}
load_rules_ipset() { ipset restore; }
load_rules_ipv4()  { iptables-restore; }
load_rules_ipv6()  { ip6tables-restore; }

save_rules() {
    log_begin_msg "${NAME} saving rules:"

    subsystems='ipset ipv4 ipv6'
    test $# -ne 0 && subsystems=$@

    c_total=0 c_success=0
    for i in ${subsystems}; do
        c_total=$((c_total+1))

        title= cmd= file=
        case "$i" in
        ipset)  title=IPset  cmd=save_rules_ipset  file=${RULES_set} ;;
        ipv4)   title=IPv4   cmd=save_rules_ipv4   file=${RULES_v4}  ;;
        ipv6)   title=IPv6   cmd=save_rules_ipv6   file=${RULES_v6}  ;;
        *)
            log_progress_msg " $i[unrecognized]"
            continue
        ;;
        esac

        log_progress_msg "${title}"

        if ! test_avail $i kernel; then
            log_progress_msg "${m_skip_kernel}"
            continue
        fi

        if ! test_avail $i user; then
            log_progress_msg "${m_skip_user}"
            continue
        fi

        if ! test -f ${file}; then
            log_progress_msg "${m_skip_rules}"
            continue
        fi

        ${cmd} > ${file}

        if test $? -ne 0; then
            log_progress_msg "${m_err}"
        else
#           log_progress_msg "${m_ok}"
            c_success=$((c_success+1))
        fi
    done; unset subsystems i title cmd file

    rc=0 # success
    test ${c_success} -lt ${c_total} && rc=255 # warning
    test ${c_success} -eq 0          && rc=1 # failure
    unset c_total c_success

    log_end_msg ${rc}; unset rc
    return 0
}
save_rules_ipset() { ipset save; }
save_rules_ipv4()  { iptables-save; }
save_rules_ipv6()  { ip6tables-save; }

flush_rules() {
    log_begin_msg "${NAME} flushing rules:"

    # reversed order IS correct
    subsystems='ipv6 ipv4 ipset'
    test $# -ne 0 && subsystems=$@

    c_total=0 c_success=0
    for i in ${subsystems}; do
        c_total=$((c_total+1))

        case "$i" in
        ipset)  title=IPSet  cmd=flush_rules_ipset ;;
        ipv4)   title=IPv4   cmd=flush_rules_ipv4  ;;
        ipv6)   title=IPv6   cmd=flush_rules_ipv6  ;;
        *)
            log_progress_msg " $i[unrecognized]"
            continue
        ;;
        esac

        log_progress_msg "${title}"

        if ! test_avail $i kernel; then
            log_progress_msg "${m_skip_kernel}"
            continue
        fi

        if ! test_avail $i user; then
            log_progress_msg "${m_skip_user}"
            continue
        fi

        ${cmd}

        if test $? -ne 0; then
            log_progress_msg "${m_err}"
        else
#           log_progress_msg "${m_ok}"
            c_success=$((c_success+1))
        fi
    done; unset subsystems i title cmd

    rc=0 # success
    test ${c_success} -lt ${c_total} && rc=255 # warning
    test ${c_success} -eq 0          && rc=1 # failure
    unset c_total c_success

    log_end_msg ${rc}; unset rc
    return 0
}
flush_rules_ipset() {
    ipset flush
    ipset destroy
}
flush_rules_ipv4() {
    for chain in INPUT FORWARD OUTPUT; do
        iptables -P ${chain} ACCEPT
    done; unset chain
    for table in $(cat /proc/net/ip_tables_names); do
        iptables -t ${table} -F
        iptables -t ${table} -X
        iptables -t ${table} -Z
    done; unset table
}
flush_rules_ipv6() {
    for chain in INPUT FORWARD OUTPUT; do
        ip6tables -P ${chain} ACCEPT
    done; unset chain
    for table in $(cat /proc/net/ip6_tables_names); do
        ip6tables -t ${table} -F
        ip6tables -t ${table} -X
        ip6tables -t ${table} -Z
    done; unset table
}

work_init() {
    init_avail

    # stderr redirection to /tmp/tmp.XXXXXXXXXX
    U=$(umask); umask 0077 # more restrictive umask
    T=$(mktemp)
    umask $U; unset U # restore origin umask
    exec 2>>$T
}
work_done() {
    exec 2>/dev/null

    if test -s $T; then
        N=10 i=0 S=

        log_begin_msg "${NAME} log contains some info; here is first $N (or less) lines of them:"
        log_end_msg 255

        exec 3< $T
        while test $i -lt $N; do
            read -r S <&3 || break
            printf '%s\n' "$S"
            i=$((i+1))
        done; unset i N
        exec 3<&-
    fi

    rm -f $T; unset T
}

R=0

act=$1; test $# -gt 0 && shift
case "${act}" in
start|reload)
    work_init
    load_rules "$@"
    work_done
;;
save)
    work_init
    save_rules "$@"
    work_done
;;
flush)
    work_init
    flush_rules "$@"
    work_done
;;
restart|force-reload)
    work_init
    flush_rules "$@"
    load_rules "$@"
    work_done
;;
stop)
    # Why? because if stop is used, the firewall gets flushed for a variable
    # amount of time during package upgrades, leaving the machine vulnerable
    # It's also not always desirable to flush during purge
    echo 'Automatic flushing disabled, use "flush" instead of "stop"' >&2
;;
*)
    echo "Usage: $0 {start|restart|reload|force-reload|save|flush} [ipset|ipv4|ipv6]" >&2
    R=1
;;
esac

exit $R