~优化新手引导中启用IP转发的提示及实现逻辑

scripts/lang/chs/userguide.lang

@@ -6,7 +6,8 @@ UG_OPTION_1="路由设备配置局域网透明代理"
 UG_OPTION_2="Linux设备仅配置本机代理"
 UG_OPTION_3="还原之前备份的设置"
 UG_RESTORE_OK="脚本设置已还原！请重新启动脚本！"
-UG_IP_FORWARD_WARN="检测到你的设备尚未开启ip转发，局域网设备将无法正常连接网络，是否立即开启？"
+UG_IP_FORWARD_WARN="检测到你的设备尚未开启IP转发，局域网设备将无法正常连接网络，是否立即开启？"
+UG_CONTAINER_WARN="注意：容器/虚拟机环境，需要用户手动在宿主机启用IP转发！"
 UG_ENABLE_LOW_MEM="检测到你的安装目录空间不足10M，是否开启小闪存模式？"
 UG_IMPORT_CONFIG="这是运行前的最后一步"
 UG_CONFIG_TIP="你必须拥有一份配置文件才能运行服务！"

scripts/lang/en/userguide.lang

@@ -7,6 +7,7 @@ UG_OPTION_2="Linux device: local proxy only"
 UG_OPTION_3="Restore previous backup settings"
 UG_RESTORE_OK="Script settings have been restored! Please restart the script!"
 UG_IP_FORWARD_WARN="Your device has not enabled IP forwarding, LAN devices will not connect properly. Enable now?"
+UG_CONTAINER_WARN="Notice: In container, IP forwarding must be enabled manually on the host!"
 UG_ENABLE_LOW_MEM="Your installation directory is less than 10MB, enable low-flash mode?"
 UG_IMPORT_CONFIG="Import configuration file? (Last step before running)"
 UG_CONFIG_TIP="You must have a configuration file to run the service!"

scripts/menus/userguide.sh

@@ -75,10 +75,13 @@ forwhat() {
             if [ "$(cat /proc/sys/net/ipv4/ip_forward)" = "0" ]; then
                 separator_line "-"
                 content_line "\033[33m$UG_IP_FORWARD_WARN\033[0m"
+				[ "$systype" = 'container' ] && content_line "\033[31m$UG_CONTAINER_WARN\033[0m"
                 read -r -p "$COMMON_INPUT_R" res
                 [ "$res" = 1 ] && {
-                    echo 'net.ipv4.ip_forward = 1' >>/etc/sysctl.conf
-                    sysctl -w net.ipv4.ip_forward=1
+                    grep -q '^net\.ipv4\.ip_forward' /etc/sysctl.conf \
+                    && sed -i 's/^net\.ipv4\.ip_forward.*/net.ipv4.ip_forward = 1/' /etc/sysctl.conf \
+                    || echo 'net.ipv4.ip_forward = 1' >> /etc/sysctl.conf
+                    sysctl -p /etc/sysctl.conf
                 }
             fi
             # 禁止docker启用的net.bridge.bridge-nf-call-iptables