Re: [Proftpd-user] Problem binding to second IP with mod _sftp on 1.3.7a on Ubuntu 21.04

> I decided to try and use Ubuntu 21.04 as the base image, but I'm
> starting to suspect I should drop back to 20.04 LTS instead...
> anyway, when I configure two IPs onto the same interface, I can't seem
> to make the mod_sftp module bind to only one of them.
> 
> Yes, I have openssh only listening on IP addr x.y.z.201, which proftpd
> should only be trying to bind to x.y.z.202, but I keep getting errors
> like this:
>
> You can see if the error I posted above, it's trying to bind to
> 0.0.0.0 for some reason.  All kinds of tweaks and hacks hasn't fixed
> this.  I've also tried downgrading to v1.3.6e as well, but it still
> doesn't work, giving the same error.
> 
> Any hints on how I can debug this and get it working?

First, there is the "default" server config in any ProFTPD configuration; this is what is probably binding to 0.0.0.0.  To disable this, outside of your mod_sftp configuration section, add:

  # Disable the default server config section
  Port 0

  # To reduce surprise, tell the default server config to bind only to localhost
  DefaultAddress 127.0.0.1

In addition, to get ProFTPD to not bind to the wildcard address, and instead to bind only to the specified addresses, you can use:

  SocketBindTight on

See:
  http://www.proftpd.org/docs/modules/mod_core.html#SocketBindTight

Hope this helps,
TJ


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