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为了安全将物联网设备单独使用一个网段和本地网络隔离，这样基于mdns协议的发现应用就不能使用了，如电视投屏、打印机等，可以使用mDNS Reflector来中继两个网段的mdns。
编译方法参考：k2p交叉编译smartdns/openssl

/usr/local/bin/mdns-reflector -n br-lan br-robot br-guest

路由配置iptables防火墙允许udp 5353入，并允许本地网络访问电视所在的网络：

iptables -A INPUT -i br-robot -p udp --dport 5353 -j ACCEPT
iptables -A FORWARD -i br-lan -j ACCEPT
iptables -A FORWARD -i robot -o br-lan -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

k2p主路由地址：192.168.1.1
n1盒子地址：192.168.1.2
k2p添加低优先级默认路由走n1，此路由只有pppoe断开后才有效：

ip rou add default via 192.168.1.2 dev br-lan metric 1000

n1盒子用netplan配置无线网络默认路由和无线热点的路由优先级，默认情况下走k2p主路由，当路由器pppoe不能连接时打开手机无线热点则自动走手机4g网络连接。

network:
    version: 2
    renderer: networkd
    ethernets:
        eth0:
            addresses:
            - 192.168.1.2/24
            dhcp4: false
            dhcp6: true
            accept-ra: true
            #gateway4: 192.168.1.1
            routes:
                - to: 0.0.0.0/0
                  via: 192.168.1.1
                  metric: 1000
            nameservers:
                addresses:
                - 192.168.1.1
                search: []

    wifis:
      wlan0:
        #防止开机时wlan0未连接导致systemd-networkd-wait-online阻塞系统启动
        optional: true
        dhcp4: yes
        dhcp6: no
        dhcp4-overrides:
            route-metric: 600
        access-points:
            "Phone-ssid":
                password: "www.haiyun.me"

n1盒子开启snat及网络转发：

iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE
sysctl -w net.ipv4.ip_forward=1

基于ubuntu 18.04，安装依赖：

apt install build-essential libncurses5-dev zlib1g-dev gawk git  libssl-dev wget unzip python ocaml-nox help2man texinfo yui-compressor

下载最新版本18.10的ImageBuilder：

https://downloads.pangubox.com/pandorabox/18.10/targets/ralink/mt7621/PandoraBox-ImageBuilder-ralink-mt7621.Linux-x86_64.tar.xz
tar Jxf PandoraBox-ImageBuilder-ralink-mt7621.Linux-x86_64.tar.xz
cd PandoraBox-ImageBuilder-ralink-mt7621.Linux-x86_64

查看可编译的固件型号及其包含的软件包：

make info

制作固件：

#info显示的所有机型固件
make image
#仅制作k2p固件
make image PROFILE="k2p"
#安装额外的软件包，自编译软件先把软件放到packages/目录下
make image PROFILE="k2p" PACKAGES="wget"
#添加files目录内文件到固件内，如files/etc/config/network网络配置文件
make image PROFILE="k2p" FILES="files"
#查看更多选项
make help

默认的软件包在以下两个文件内：

include/target.mk
.profiles.mk 

开始使用默认配置制作k2p固件：

make image PROFILE="k2p"

遇到以下错误：

 regexp could be something like 'pkgname*' '*file*' or similar
 e.g. opkg info 'libstd*' or opkg search '*libop*' or opkg remove 'libncur*'
Makefile:140: recipe for target 'package_install' failed
make[2]: *** [package_install] Error 1
make[2]: Leaving directory '/tmp/PandoraBox-ImageBuilder-ralink-mt7621.Linux-x86_64'
Makefile:110: recipe for target '_call_image' failed
make[1]: *** [_call_image] Error 2
make[1]: Leaving directory '/tmp/PandoraBox-ImageBuilder-ralink-mt7621.Linux-x86_64'
Makefile:196: recipe for target 'image' failed
make: *** [image] Error 2

因为在Makerfile 144行要预先安装kernel文件，而package没kernel软件包，下载kernel：

wget https://downloads.pangubox.com/pandorabox/18.10/targets/ralink/mt7621/packages/kernel_3.14.79-1_mipsel_1004kc_dsp.ipk -P packages/

再次执行又出现错误：

Collected errors:
 * opkg_install_cmd: Cannot install package dosfsck.
 * opkg_install_cmd: Cannot install package fkmod-leds-gpio.
 * opkg_install_cmd: Cannot install package kmod-ipt-nathelper.
 * opkg_install_cmd: Cannot install package mkdosfs.
 * satisfy_dependencies_for: Cannot satisfy the following dependencies for ralink-utils:
 *      kmod-ipt-nathelper-extra * 
Makefile:140: recipe for target 'package_install' failed
make[2]: *** [package_install] Error 255
make[2]: Leaving directory '/tmp/PandoraBox-ImageBuilder-ralink-mt7621.Linux-x86_64'
Makefile:110: recipe for target '_call_image' failed
make[1]: *** [_call_image] Error 2
make[1]: Leaving directory '/tmp/PandoraBox-ImageBuilder-ralink-mt7621.Linux-x86_64'
Makefile:196: recipe for target 'image' failed
make: *** [image] Error 2

因为新版的openwrt将kmod-ipt-nathelper-extra 更改为kmod-nf-nathelper-extra，而潘多拉的源package没修改依赖，使用以下脚本在制作时更新源后修改软件依赖项kmod-ipt-nathelper-extra为kmod-nf-nathelper-extra：

#!/bin/bash
for file in `ls dl/18.10*`;do 
        echo $file;
        mv $file $file.gz
        gunzip $file.gz
        sed -i 's/kmod-ipt-nathelper-extra/kmod-nf-nathelper-extra/g' $file
        gzip -9 $file
        mv $file.gz $file
done
sed -i 's/kmod-ipt-nathelper/kmod-nf-nathelper/g' include/target.mk 

将以上保存为fix.sh到image build目录加可执行权限，并修改Makefile文件在122行$(MAKE) package_install前插入：

$(TOPDIR)/fix.sh

再次执行又遇到以下错误：

Collected errors:
 * opkg_install_cmd: Cannot install package dosfsck.
 * opkg_install_cmd: Cannot install package fkmod-leds-gpio.
 * opkg_install_cmd: Cannot install package mkdosfs.

因为上面这3个软件有的改名，有的名字写错，修复下：

sed -i 's/fkmod-leds-gpio/kmod-leds-gpio/g' .profiles.mk
sed -i 's/mkdosfs dosfsck/dosfstools/g' .profiles.mk
````
再次执行终于制作完成k2p固件，将制作的固件scp到路由/tmp/目录开始刷机：

scp bin/targets/ralink/mt7621/PandoraBox-ralink-mt7621-k2p-2018-10-26-git-85c67caa2-squashfs-sysupgrade.bin 192.168.168.1:/tmp/

k2p路由内使用[sysupgrade命令刷机][1]：

sysupgrade -n -v /tmp/PandoraBox-ralink-mt7621-k2p-2018-10-26-git-85c67caa2-squashfs-sysupgrade.bin