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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

安装交叉编译环境见：ubuntu下交叉编译arm64/armbian内核模块。
下载5.3内核及wireguard最新源码，并打补丁到内核。

#git clone -b 5.3 --depth 1 https://github.com/150balbes/Amlogic_s905-kernel.git
git clone -b 5.3 --depth 1 https://github.com/w22gb8/Amlogic_s905-kernel.git
cd Amlogic_s905-kernel/
#git clone https://git.zx2c4.com/wireguard-linux-compat
git clone -b v1.0.20211208 --depth=1 https://github.com/WireGuard/wireguard-linux-compat.git
bash ./wireguard-linux-compat/kernel-tree-scripts/jury-rig.sh .

编译wireguard模块，版本后缀-aml-g12和内核后缀保持一致。

cp ../config-5.3.0-aml-g12 .config
make LOCALVERSION="-aml-g12" modules_prepare
make M=net/wireguard CONFIG_WIREGUARD=m modules
modinfo net/wireguard/wireguard.ko

替换升级wireguard内核模块：

systemctl stop wg-quick@wg0.service 
cp wireguard.ko /lib/modules/5.3.0-aml-g12/kernel/net/wireguard/
modprobe -r wireguard
systemctl start wg-quick@wg0.service 

安装编译环境及下载交叉编译工具：

apt update
apt -y install gcc make pkg-config git bison flex libelf-dev libssl-dev libncurses5-dev bc
wget https://releases.linaro.org/components/toolchain/binaries/latest-7/aarch64-linux-gnu/gcc-linaro-7.5.0-2019.12-x86_64_aarch64-linux-gnu.tar.xz
tar -Jxf gcc-linaro-7.5.0-2019.12-x86_64_aarch64-linux-gnu.tar.xz 
export ARCH=arm64 
export CROSS_COMPILE=`pwd`/gcc-linaro-7.5.0-2019.12-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-

查看内核版本：

uname -r
4.18.7-aml-s9xxx

下载内核源码：

#git clone https://github.com/150balbes/Amlogic_s905-kernel.git
#使用4.18.7内核
#git checkout 20181012
git clone -b 20181012 --depth 1 https://github.com/w22gb8/Amlogic_s905-kernel.git
cd Amlogic_s905-kernel

初始化配置，不做这步直接编译模块会提示错误： fatal error: include/generated/autoconf.h: No such file or directory。

cp config_5.60 .config
make prepare
make scripts

编译指定模块：

make M=net/ipv4/ CONFIG_TCP_CONG_BBR=m modules
make M=drivers/usb/class CONFIG_USB_PRINTER=m modules

编译所有模块：

make modules 
make modules_install INSTALL_MOD_PATH=/

复制模块到目标机器对应目录并加载：

cp tcp_bbr.ko /lib/modules/`uname -r`/kernel/net/ipv4
#echo 'kernel/net/ipv4/tcp_bbr.ko:' >> /lib/modules/`uname -r`/modules.dep
depmod 
modprobe tcp_bbr

加载模块时出现invalid module format的错误，是version magic版本不一致或crc校验不通过，可通过modinfo查看本机模块和新编译模块version magic版本信息，通过dmesg查看log出现以下错误：

sch_fq: version magic '4.18.7 SMP preempt mod_unload aarch64' should be '4.18.7-aml-s9xxx SMP preempt mod_unload aarch64'

可见内核版本后缀不一样，在编译时添加版本后缀：

make LOCALVERSION="-aml-s9xxx"

编译模块时添加版本后缀无效？那就在初始时添加，后续编译时不要再次添加。

make LOCALVERSION="-aml-s9xxx" modules_prepare

参考：
https://serverfault.com/questions/568395/what-is-creating-the-generated-autoconf-h
https://wiki.archlinux.org/index.php/Compile_kernel_module