iptables - 如何使用iptables进行本地端口转发

Question

我有一个应用程序(服务器)正在监听端口 8080。我希望能够将端口 80 转发给它，以便点击 http://localhost 解析我的应用程序(在 本地主机:8080)。

这应该适用于任何端口映射(例如 80:8080 => P_src:P_target)，并使用现代 *nix 机器(例如 Ubuntu)的最佳实践.

注意这一切都是在本地完成的，因此不需要接受除本地主机之外的任何人的连接。

Answer 1

经过大量搜索后，我发现答案是使用 iptables、设置 NAT 并使用内置的 PREROUTING 和 OUTPUT。

首先，您必须启用端口转发:

echo "1">/proc/sys/net/ipv4/ip_forward

然后，您必须使用您自己的 ${P_src} 和 ${P_target} 值将以下规则添加到 iptables NAT 表中:

iptables -t nat -A PREROUTING -s 127.0.0.1 -p tcp --dport ${P_src} -j REDIRECT --to ${P_target}`
iptables -t nat -A OUTPUT -s 127.0.0.1 -p tcp --dport ${P_src} -j REDIRECT --to ${P_target}`

如果您想删除规则，只需对每个规则使用 -D 开关而不是 -A 即可。

我为此构建了一个很好的小脚本，用于添加和删除映射。

#!/bin/bash
#
#   API: ./forwardPorts.sh add|rm p1:p1' p2:p2' ...
#
#   Results in the appending (-A) or deleting (-D) of iptable rule pairs that
#   would otherwise facilitate port forwarding.
#
#   E.g
#   sudo iptables -t nat -A PREROUTING -s 127.0.0.1 -p tcp --dport 80 -j REDIRECT --to 8080
#   sudo iptables -t nat -A OUTPUT -s 127.0.0.1 -p tcp --dport 80 -j REDIRECT --to 8080
#

if [[ $# -lt 2 ]]; then
    echo "forwardPorts takes a state (i.e. add or rm) and any number port mappings (e.g. 80:8080)";
    exit 1;
fi

case $1 in
    add )
        append_or_delete=A;;
    rm )
        append_or_delete=D;;
    * )
        echo "forwardPorts requires a state (i.e. add or rm) as it's first argument";
        exit 1; ;;
esac

shift 1;

# Do a quick check to make sure all mappings are integers
# Many thanks to S.O. for clever string splitting:
# http://stackoverflow.com/questions/918886/how-do-i-split-a-string-on-a-delimiter-in-bash
for map in "$@"
do
    IFS=: read -a from_to_array <<< "$map"
    if  [[ ! ${from_to_array[0]} =~ ^-?[0-9]+$ ]] || [[ ! ${from_to_array[1]} =~ ^-?[0-9]+$ ]]; then
        echo "forwardPorts port maps must go from an integer, to an integer (e.g. 443:4443)";
        exit 1;
    fi
    mappings[${#mappings[@]}]=${map}
done

# We're shooting for transactional consistency. Only manipulate iptables if all 
# the rules have a chance to succeed.
for map in "${mappings[@]}"
do
    IFS=: read -a from_to_array <<< "$map" 
    from=${from_to_array[0]}
    to=${from_to_array[1]}

    sudo iptables -t nat -$append_or_delete PREROUTING -s 127.0.0.1 -p tcp --dport $from -j REDIRECT --to $to
    sudo iptables -t nat -$append_or_delete OUTPUT -s 127.0.0.1 -p tcp --dport $from -j REDIRECT --to $to
done

exit 0;