FileZilla Client (Windows) uses IPv6 in preference to IPv4

[Chris Jenkins]

I have several Windows clients running Windows XP Pro SP3 and Windows Vista SP1. I have FileZilla client 3.2.0 installed. All these machines have a dual IPv4 and IPv6 configuration as I am currently testing IPv6. My DNS server (Windows 2003 Server SP2) returns both IPv4 and IPv6 addresses for my servers when queried.

My FileZilla sever (0.9.30) is running on a Windows XP SP3 machine, also with a valid IPv6 configuration.

When I use the FileZilla client to try and connect to a server for which my DNS server can return both an IPv6 address and an IPv4 address, the FileZilla client always tries to use the IPv6 address in preference to the IPv4 address. This might not be an issue except that the FileZilla server does not seem to listen to/accept connections on its host's IPv6 address. As a result the client is not able to connect. I have tried changing the binding order on the client machines to make IPv4 come before IPv6 but it does not help.

This seems like a bug to me. Surely use of IPv6 should at a minimum only be by explicit request? Ideally one could specify which to use as a default at the client level and maybe also with a host specific override. I imagine mixed environments are becoming quite common and this could become a big problem.

[Tim Kosse]

FileZilla uses the addresses in the same order as returned by the system's TCP stack.

If your ISP does not support IPv6 but you nontheless get IPv6 addresses, your ISP's DNS server (should you use it) or your computer are badly configured.

IPv6 support is mission critical.

[Tim Kosse]

FileZilla server does not seem to listen to/accept connections on its host's IPv6 address

That's be a bug (actually missing feature) in the server, need to be filed separately (if there isn't already a ticket for it)