Re: ftp & multi-hop?

[Michael Albinus]

"Kai Großjohann" <address@hidden> writes:

>> I would like to connect to an ftp server in two hops.  One over `sshx'
>> to a server behind a firewall, and thence via ftp to a second server
>> inside that firewall.  Now I understand that 'ftp isn't a member of
>> `tramp-multi-connection-function-alist', so this isn't supported
>> out-of-the-box.

[...]

> So whereas multi-hop-with-inline just needs a single shell, doing multi-hop
> with out-of-band methods requires O(n) shells where n is the number of hops.
>
> FTP is similar to an out-of-band method because the protocol has a control
> connection (for sending commands like cd and dir) and then establishes
> additional data connections for actual file transfer.

One could allow out-of-band methods as _last_ hop only. This would
reduce the logic to 2 connections. And for methods like ftp and smb it
wouldn't make sense otherwise.

> But maybe the good news is that Ange-FTP itself supports a so-called
> "gateway" feature.  I never really grokked what that does, but it seems you 
> can tell
> it to rsh to another host to invoke ftp from there.  I think Ange-FTP can
> then use rcp to transfer the files between the local system and the gateway
> host.  Ange-FTP stems from the before-SSH times, but I guess that whatever its
> methods are for rsh/rcp, they can be adapted to use ssh/scp instead.

It's a nice idea to map 
/multi:ssh:address@hidden:ftp:address@hidden:/path/to.file
on Ange-FTP gateways. Worth a try.

> Kai

Best regards, Michael.