root@ACU:~# tree /etc/config/root/
/etc/config/root/
├── etc
│?? ├── config
│?? │?? └── rtty
│?? └── init.d
│??     └── rtty
└── usr
    ├── lib
    │?? ├── libev.so -> libev.so.4.0.0
    │?? ├── libev.so.4 -> libev.so.4.0.0
    │?? └── libev.so.4.0.0
    └── sbin
        ├── rtty
        └── tree

6 directories, 7 files
root@ACU:~# 
root@ACU:~# ls -alh /etc/rc.local 
-rwxr-xr-x    1 root     root         291 Jul 17 11:14 /etc/rc.local
root@ACU:~# 
root@ACU:~# cat /etc/rc.local 
# Put your custom commands here that should be executed once
# the system init finished. By default this file does nothing.

[ -d "/etc/config/root" ] && cp -af /etc/config/root/* / && echo "copy file ..."
[ -f "/etc/init.d/rtty" ] && /etc/init.d/rtty start && echo "rtty start ..."

exit 0
root@ACU:~# 
root@ACU:~# route 
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         10.179.128.1    0.0.0.0         UG    0      0        0 br-lan3074
10.179.128.0    *               255.255.128.0   U     0      0        0 br-lan3074
192.168.0.0     *               255.255.255.0   U     0      0        0 br-lan3074
192.192.192.0   *               255.255.255.0   U     0      0        0 br-lan0
192.192.192.0   *               255.255.255.0   U     0      0        0 eth0
root@ACU:~# 
root@ACU:~# route -n | grep "0.0.0.0.*0.0.0.0" | awk '{print $8}'
br-lan3074
root@ACU:~# 
root@ACU:~# uci set rtty.@rtty[0].ifname="$(route -n | grep "0.0.0.0.*0.0.0.0" | awk '{print $8}')"
root@ACU:~# 
root@ACU:~# uci commit rtty
root@ACU:~# 
root@ACU:~# cat /etc/config/rtty

config rtty
	option ifname      'br-lan3074'
#	option id          'My-Device'
#	option description 'Description of my device'
	option host        '10.0.8.151'        # Server host
	option port        '5912'              # Server Port
#	option ssl         '1'                  # Whether to use ssl
#	option insecure    '1'                  # Allow insecure server connections when using SSL
#	option token       'your-token'         # generated by rttys
#	option username    'root'               # Skip a second login authentication. See man login(1) about the details
#	option verbose     '1'                  # verbose log

root@ACU:~# 
root@ACU:~#