Passive URL Resolution

[OneYellowLemon]

Hello! I am trying to have an FTP server work over both local IP and public IP, and I am trying to get the passive URL to work this way. As per the README, this code is provided.

const {Netmask} = require('netmask');
const networks = {
 '$GATEWAY_IP/32': `${public_ip}`, 
 '10.0.0.0/8'    : `${lan_ip}`
} 

const resolverFunction = (address) => {
   for (const network in networks) {
       try {
           const mask = new Netmask(network);
           if (mask.contains(address)) return networks[network];
       }
       catch (err) {
           logger.error('Error checking source network', err);
       }
   }
   return '127.0.0.1';
}

new FtpSrv({pasv_url: resolverFunction});

However, I can't figure out how I would make this work without assuming what gateway IP and netmask people will have on their LANs. Is anyone able to help me?

[antonilol]

Get the gateway ip address with either a node js library or a system command

[OneYellowLemon]

How would I get the network submask? I believe I would have to parse command line utils, is there any other way to do it?

[antonilol]

with the command (replace wlp1s0 with your network interface name) ifconfig wlp1s0 | grep netmask | awk '{ printf $4 }'

[antonilol]

oh and also possible with command parsing: https://net-raft.com/Questions/1376/how-to-get-client-netmask-using-nodejs-/1376
i tested it and it works for me

[matt-forster]

Thanks for the answer @antonilol!