交叉编译环境配置，使用PandoraBox提供的SDK：
apt install build-essential -y
wget https://downloads.pangubox.com/pandorabox/18.10/targets/ralink/mt7621/PandoraBox-SDK-ralink-mt7621_gcc-5.5.0_uClibc-1.0.x.Linux-x86_64.tar.xz
tar xf PandoraBox-SDK-ralink-mt7621_gcc-5.5.0_uClibc-1.0.x.Linux-x86_64.tar.xz
mv PandoraBox-SDK-ralink-mt7621_gcc-5.5.0_uClibc-1.0.x.Linux-x86_64 PandoraBox
export STAGING_DIR=/root/PandoraBox/staging_dir/
export PKG_CONFIG_PATH=/root/PandoraBox/staging_dir/target-mipsel_1004kc+dsp_uClibc-1.0.x/usr/lib/pkgconfig/
export PATH=$PATH:/root/PandoraBox/staging_dir/toolchain-mipsel_1004kc+dsp_gcc-5.5.0_uClibc-1.0.x/bin/
export CC=mipsel-openwrt-linux-gcc
export RANLIB=mipsel-openwrt-linux-ranlib
export AR=mipsel-openwrt-linux-ar
export LD=mipsel-openwrt-linux-ld潘多拉SDK自带openssl版本为1.1.0，为使用tls1.3编译安装最新版openssl1.1.1：
wget https://www.openssl.org/source/openssl-1.1.1d.tar.gz
tar zxvf openssl-1.1.1d.tar.gz
./config no-asm shared --prefix=/usr/local/openssl-mipsel
sed -i 's/-m64//g' Makefile
make && make install编译smartdns：
git clone https://github.com/pymumu/smartdns.git
cd smartdns/src/
CFLAGS=-I/usr/local/openssl-mipsel/include/ LDFLAGS=-L/usr/local/openssl-mipsel/lib/ make
#不额外安装openssl，使用sdk自带的openssl
#CFLAGS=-I/root/PandoraBox/staging_dir/target-mipsel_1004kc+dsp_uClibc-1.0.x/usr/include/ LDFLAGS=-L/root/PandoraBox/staging_dir/target-mipsel_1004kc+dsp_uClibc-1.0.x/usr/lib/ make静态编译包含openssl，修改Makefile：
ifeq ($(STATIC), yes)
LDFLAGS += -Wl,-dn -lssl -lcrypto -Wl,-dy -lpthread -ldl -lc -lgcc_eh
#LDFLAGS += -Wl,-dn -lssl -lcrypto -Wl,-dy,--whole-archive -lpthread -Wl,--no-whole-archive -ldl -lc -lgcc_eh静态编译：
STATIC=yes CFLAGS=-I/usr/local/openssl-mipsel/include/ LDFLAGS=-L/usr/local/openssl-mipsel/lib/ make 如果以非root运行smartdns且使用ping测速，需设置cap_net_raw，不然不能发送icmp ping：
#setcap cap_net_raw+eip /usr/local/bin/smartdns
#cap_net_bind_service允许非root监听53端口，ipset需要cap_net_admin权限
setcap cap_net_bind_service,cap_net_raw,cap_net_admin=+eip /usr/local/bin/smartdns或直接使用systemd:
AmbientCapabilities=CAP_NET_ADMIN CAP_NET_BIND_SERVICE CAP_NET_RAW
CapabilityBoundingSet=CAP_NET_ADMIN CAP_NET_BIND_SERVICE CAP_NET_RAW由于使用静态编译openssl1.1文件较大，不使用tls1.3可使用自带的openssl1.0动态编译：
CFLAGS=-I/root/PandoraBox/staging_dir/target-mipsel_1004kc+dsp_uClibc-1.0.x/usr/include/ LDFLAGS=-L/root/PandoraBox/staging_dir/target-mipsel_1004kc+dsp_uClibc-1.0.x/usr/lib/ make参考：
https://www.boris1993.com/linux/allow-non-root-process-to-bind-low-numbered-ports.html