iptables启动脚本分析

#!/bin/sh
#
# iptables      Start iptables firewall
#
# chkconfig: 2345 08 92
# description:  Starts, stops and saves iptables firewall
#
# config: /etc/sysconfig/iptables
# config: /etc/sysconfig/iptables-config
#
### BEGIN INIT INFO
# Provides: iptables
# Required-Start:
# Required-Stop:
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: start and stop iptables firewall
# Description: Start, stop and save iptables firewall
### END INIT INFO   

# Source function library.
. /etc/init.d/functions   

IPTABLES=iptables                                       #变量IPTABLES
IPTABLES_DATA=/etc/sysconfig/$IPTABLES                  #变量IPTABLES_DATA=/etc/sysconfig/iptables
IPTABLES_CONFIG=/etc/sysconfig/${IPTABLES}-config       #变量IPTABLES+CONFIG=/etc/sysoncifg/iptables-config
IPV=${IPTABLES%tables} # ip for ipv4 | ip6 for ipv6     #变量IPV,${IPTABLES%tables},将上一个变量IPTABLES的tables字符串删除
[ "$IPV" = "ip" ] && _IPV="ipv4" || _IPV="ipv6"         #如IPV=ip就运行_IPV=ipv4否则就运行_IPV=ipv6
PROC_IPTABLES_NAMES=/proc/net/${IPV}_tables_names       #变量PROC_IPTABLES_NAMES=/proc/net/${IPV}_tables_names 查看 /proc/net/有例如以下文件
#ls /proc/net/ip*
#/proc/net/ip6_flowlabel  /proc/net/ip6_mr_vif   /proc/net/ip_mr_vif          /proc/net/ip_tables_names    /proc/net/ipv6_route /proc/net/ip6_mr_cache   /proc/net/ip_mr_cache  /proc/net/ip_tables_matches  /proc/net/ip_tables_targets   

VAR_SUBSYS_IPTABLES=/var/lock/subsys/$IPTABLES          #变量VAR_SUBSYS_IPTABLES设置状态锁文件   

# only usable for root
[ $EUID = 0 ] || exit 4                                 #推断是否是root用户，否则退出状态为4   

if [ ! -x /sbin/$IPTABLES ]; then                       #推断/sbin/iptables不存在。就显示以下的警告信息
    echo -n $"${IPTABLES}: /sbin/$IPTABLES does not exist."; warning; echo
    exit 5                                              #退出状态为5
fi   

# Old or new modutils
/sbin/modprobe --version 2>&1 | grep -q module-init-tools
    && NEW_MODUTILS=1
    || NEW_MODUTILS=0   

# Default firewall configuration:
IPTABLES_MODULES=""
IPTABLES_MODULES_UNLOAD="yes"
IPTABLES_SAVE_ON_STOP="no"
IPTABLES_SAVE_ON_RESTART="no"
IPTABLES_SAVE_COUNTER="no"
IPTABLES_STATUS_NUMERIC="yes"
IPTABLES_STATUS_VERBOSE="no"
IPTABLES_STATUS_LINENUMBERS="yes"

# Load firewall configuration.
[ -f "$IPTABLES_CONFIG" ] && . "$IPTABLES_CONFIG"  #推断是否存在/etc/sysoncifg/iptables-config   

# Netfilter modules
NF_MODULES=($(lsmod | awk "/^${IPV}table_/ {print $1}") ${IPV}_tables)
# 查看启动iptables载入的模块，当iptables用此脚本停止时。模块是没有载入的
#----#lsmod|awk "/^iptable_/ {print $1}" $ip_tables----
#---iptable_filter-------------------------------------
#---iptable_nat----------------------------------------   

NF_MODULES_COMMON=(x_tables nf_nat nf_conntrack) # Used by netfilter v4 and v6   

# Get active tables
NF_TABLES=$(cat "$PROC_IPTABLES_NAMES" 2>/dev/null)
#查看系统载入的iptables模块
#--------- #cat /proc/net/ip_tables_names---------
#---------filter----------------------------------
#---------nat-------------------------------------   

rmmod_r() {
    # Unload module with all referring modules.
    # At first all referring modules will be unloaded, then the module itself.
    local mod=$1  #定义一个局部变量mod=$1
    local ret=0   #定义一个局部变量ret=0
    local ref=    #定义一个局部变量ref

    # Get referring modules.
    # New modutils have another output format.
    [ $NEW_MODUTILS = 1 ]
        && ref=$(lsmod | awk "/^${mod}/ { print $4; }" | tr ',' ' ')
        || ref=$(lsmod | grep ^${mod} | cut -d "[" -s -f 2 | cut -d "]" -s -f 1)
#假设NEW_MODUTILSd的值1。即推断modprobe --version|grep -q module-init-tools成功，
#lsmod打印第4列，显示出模块的内容,并将显示出的。所有删除
#假设NEW_MODUTILSd的值0，就运行后面   

# recursive call for all referring modules
    for i in $ref; do
        rmmod_r $i
        let ret+=$?

;
    done
#删除已经载入的iptables模块   

    # Unload module.
    # The extra test is for 2.6: The module might have autocleaned,
    # after all referring modules are unloaded.
    if grep -q "^${mod}" /proc/modules ; then #查看iptables的模块
        modprobe -r $mod > /dev/null 2>&1     #modprobe -r删除存在的iptables模块
        res=$?

#查看状态
        [ $res -eq 0 ] || echo -n " $mod"     #运行成功。显示内容
        let ret+=$res;
    fi   

    return $ret
    #===========================================#
cat /proc/modules |grep ip
iptable_filter 2759 0 - Live 0xffffffffa02e1000
iptable_nat 6124 1 - Live 0xffffffffa029b000
nf_nat 22788 1 iptable_nat, Live 0xffffffffa02d1000
nf_conntrack_ipv4 9440 3 iptable_nat,nf_nat, Live 0xffffffffa0286000
nf_conntrack 79643 3 iptable_nat,nf_nat,nf_conntrack_ipv4, Live 0xffffffffa02b0000
nf_defrag_ipv4 1449 1 nf_conntrack_ipv4, Live 0xffffffffa0257000
ip_tables 17765 2 iptable_filter,iptable_nat, Live 0xffffffffa02a9000
ipv6 322899 74 - Live 0xffffffffa01ab000
#====================================================#   

}   

flush_n_delete() {
    #情况默认策略
    # Flush firewall rules and delete chains.
    [ ! -e "$PROC_IPTABLES_NAMES" ] && return 0
#假设不存在/proc/net/ip_tables_names。则返回为0   

    # Check if firewall is configured (has tables)
    [ -z "$NF_TABLES" ] && return 1
#假设存在 cat /proc/net/ip_tables_names显示出来的内容，返回为1   

    echo -n $"${IPTABLES}: Flushing firewall rules: "
#显示
    ret=0
    # For all tables
    for i in $NF_TABLES; do
        # Flush firewall rules.
        $IPTABLES -t $i -F;
        let ret+=$?

;   

        # Delete firewall chains.
        $IPTABLES -t $i -X;
        let ret+=$?

;   

        # Set counter to zero.
        $IPTABLES -t $i -Z;
        let ret+=$?;
    done
#将所有iptables表运行-F -X -Z的操作   

    [ $ret -eq 0 ] && success || failure
    echo
    return $ret
}   

set_policy() {
    # Set policy for configured tables.
    policy=$1   

    # Check if iptable module is loaded
    [ ! -e "$PROC_IPTABLES_NAMES" ] && return 0
#假设不存在/proc/net/ip_tables_names，则返回为0   

    # Check if firewall is configured (has tables)
    tables=$(cat "$PROC_IPTABLES_NAMES" 2>/dev/null)
    #假设存在 cat /proc/net/ip_tables_names显示出来的内容，赋值给tables变量
    [ -z "$tables" ] && return 1
    #tables变量是否有值。无值返回1   

    echo -n $"${IPTABLES}: Setting chains to policy $policy: "
    ret=0
    for i in $tables; do
        echo -n "$i "
        case "$i" in
            raw)
                $IPTABLES -t raw -P PREROUTING $policy
                    && $IPTABLES -t raw -P OUTPUT $policy
                    || let ret+=1
                ;;
            filter)
                $IPTABLES -t filter -P INPUT $policy
                    && $IPTABLES -t filter -P OUTPUT $policy
                    && $IPTABLES -t filter -P FORWARD $policy
                    || let ret+=1
                ;;
            nat)
                $IPTABLES -t nat -P PREROUTING $policy
                    && $IPTABLES -t nat -P POSTROUTING $policy
                    && $IPTABLES -t nat -P OUTPUT $policy
                    || let ret+=1
                ;;
            mangle)
                $IPTABLES -t mangle -P PREROUTING $policy
                    && $IPTABLES -t mangle -P POSTROUTING $policy
                    && $IPTABLES -t mangle -P INPUT $policy
                    && $IPTABLES -t mangle -P OUTPUT $policy
                    && $IPTABLES -t mangle -P FORWARD $policy
                    || let ret+=1
                ;;
            *)
                let ret+=1
                ;;
        esac
    done   

    [ $ret -eq 0 ] && success || failure
    echo
    return $ret
    #以上命令为运行各表的策略设置
}   

start() {
    # Do not start if there is no config file.
    [ ! -f "$IPTABLES_DATA" ] && return 6
#假设/etc/sysconfig/iptables不存在。返回值为6   

    # check if ipv6 module load is deactivated
    if [ "${_IPV}" = "ipv6" ]
        && grep -qIsE "^install[[:space:]]+${_IPV}[[:space:]]+/bin/(true|false)" /etc/modprobe.conf /etc/modprobe.d/* ; then
        echo $"${IPTABLES}: ${_IPV} is disabled."
        return 150
    fi
#检查ipv6模块是否载入
    echo -n $"${IPTABLES}: Applying firewall rules: "

    OPT=
    [ "x$IPTABLES_SAVE_COUNTER" = "xyes" ] && OPT="-c"

    $IPTABLES-restore $OPT $IPTABLES_DATA
    #运行iptables-restore /etc/sysconfig/iptables恢复iptables设置的策略
    if [ $? -eq 0 ]; then
        success; echo
    else
        failure; echo; return 1
    fi
    #推断是否运行成功，并显示状态   

    # Load additional modules (helpers)
    if [ -n "$IPTABLES_MODULES" ]; then
        echo -n $"${IPTABLES}: Loading additional modules: "
        ret=0
        for mod in $IPTABLES_MODULES; do
            echo -n "$mod "
            modprobe $mod > /dev/null 2>&1
            let ret+=$?

;
        done
    #载入iptables模块
        [ $ret -eq 0 ] && success || failure
        echo
    fi   

    touch $VAR_SUBSYS_IPTABLES
    #建立状态文件锁=/var/lock/subsys/iptables
    return $ret
}   

stop() {
    # Do not stop if iptables module is not loaded.
    [ ! -e "$PROC_IPTABLES_NAMES" ] && return 0
#不存在/proc/net/ip_tables_names
    flush_n_delete
    set_policy ACCEPT   

    if [ "x$IPTABLES_MODULES_UNLOAD" = "xyes" ]; then
        echo -n $"${IPTABLES}: Unloading modules: "
        ret=0
        for mod in ${NF_MODULES[*]}; do
            rmmod_r $mod
            let ret+=$?;
        done
    #卸载iptables模块
        # try to unload remaining netfilter modules used by ipv4 and ipv6
        # netfilter
        for mod in ${NF_MODULES_COMMON[*]}; do
            rmmod_r $mod >/dev/null
        done
        [ $ret -eq 0 ] && success || failure
        echo
    fi   

    rm -f $VAR_SUBSYS_IPTABLES
    return $ret
}   

save() {
    # Check if iptable module is loaded
    [ ! -e "$PROC_IPTABLES_NAMES" ] && return 0
#不存在在/proc/net/ip_tables_names，返回0
    # Check if firewall is configured (has tables)
    [ -z "$NF_TABLES" ] && return 6
#是否存在
    echo -n $"${IPTABLES}: Saving firewall rules to $IPTABLES_DATA: "

    OPT=
    [ "x$IPTABLES_SAVE_COUNTER" = "xyes" ] && OPT="-c"

    ret=0
    TMP_FILE=$(/bin/mktemp -q $IPTABLES_DATA.XXXXXX)
        && chmod 600 "$TMP_FILE"
        && $IPTABLES-save $OPT > $TMP_FILE 2>/dev/null
    #iptables-save -c > 保存到文件
        && size=$(stat -c '%s' $TMP_FILE) && [ $size -gt 0 ]
        || ret=1#推断文件是否为空
    if [ $ret -eq 0 ]; then
        if [ -e $IPTABLES_DATA ]; then
            cp -f $IPTABLES_DATA $IPTABLES_DATA.save  #将/etc/sysconfig/iptables备份为iptables.save
                && chmod 600 $IPTABLES_DATA.save    #更改/etc/sysconfig/iptables权限为600
                && restorecon $IPTABLES_DATA.save   #更改/etc/sysconfig/iptables的selinux
                || ret=1
        fi
        if [ $ret -eq 0 ]; then
            mv -f $TMP_FILE $IPTABLES_DATA
                && chmod 600 $IPTABLES_DATA
                && restorecon $IPTABLES_DATA
                || ret=1
        fi
    fi
    rm -f $TMP_FILE
    [ $ret -eq 0 ] && success || failure
    echo
    return $ret
}   

status() {
    if [ ! -f "$VAR_SUBSYS_IPTABLES" -a -z "$NF_TABLES" ]; then
        echo $"${IPTABLES}: Firewall is not running."
        return 3
    fi
    #查看文件状态锁是否存在   

    # Do not print status if lockfile is missing and iptables modules are not
    # loaded.
    # Check if iptable modules are loaded
    if [ ! -e "$PROC_IPTABLES_NAMES" ]; then
        echo $"${IPTABLES}: Firewall modules are not loaded."
        return 3
    fi
#
    # Check if firewall is configured (has tables)
    if [ -z "$NF_TABLES" ]; then
        echo $"${IPTABLES}: Firewall is not configured. "
        return 3
    fi   

    NUM=
    [ "x$IPTABLES_STATUS_NUMERIC" = "xyes" ] && NUM="-n"
    VERBOSE=
    [ "x$IPTABLES_STATUS_VERBOSE" = "xyes" ] && VERBOSE="--verbose"
    COUNT=
    [ "x$IPTABLES_STATUS_LINENUMBERS" = "xyes" ] && COUNT="--line-numbers"

    for table in $NF_TABLES; do
        echo $"Table: $table"
        $IPTABLES -t $table --list $NUM $VERBOSE $COUNT && echo
    done   

    return 0
}   

restart() {
    [ "x$IPTABLES_SAVE_ON_RESTART" = "xyes" ] && save
    stop
    start
}   

case "$1" in
    start)
        [ -f "$VAR_SUBSYS_IPTABLES" ] && exit 0
        start
        RETVAL=$?

;;
    stop)
        [ "x$IPTABLES_SAVE_ON_STOP" = "xyes" ] && save
        stop
        RETVAL=$?
        ;;
    restart|force-reload)
        restart
        RETVAL=$?

;;
    reload)
        # unimplemented
        RETVAL=3
        ;;
    condrestart|try-restart)
        [ ! -e "$VAR_SUBSYS_IPTABLES" ] && exit 0
        restart
        RETVAL=$?
        ;;
    status)
        status
        RETVAL=$?

;;
    panic)
        flush_n_delete
        set_policy DROP
        RETVAL=$?

;;
    save)
        save
        RETVAL=$?
        ;;
    *)
        echo $"Usage: ${IPTABLES} {start|stop|restart|condrestart|status|panic|save}"
        RETVAL=2
        ;;
esac   

exit $RETVAL   

附录
lsmod命令
第1列：表示模块的名称。
第2列：表示模块的大小。
第3列：表示依赖模块的个数。
第4列：表示依赖模块的内容。

转载请注明文章转自：良玉的博客 [http://blog.uouo123.com]