[U-Boot-Users] U-Boot & FTP

Tolunay Orkun
2005-01-05T00:37:29Z

Wolfgang Denk wrote:
> In message <E89EC5FBB92CAB4C9BB301E636B0D858075C14@mailserver4.mail4.local> you wrote:
>
>>Are there any patches/modifications that enable U-boot to boot a kernel
>>via FTP. ?
>
>
> No, and there will be none.
>
> FTP requires TCP/IP, which is too much overhead just for a boot
> loader. If you need FTP, then boot an OS which runs the download.
>
> On the othe rhand, U-Boot offers TFTP and NFS for download, so I
> wonder why you think that FTP would make your life easier.
>
> Best regards,
>
> Wolfgang Denk
>

I can think of one case where FTP would be desirable. If the host is
behind a stateful firewall and TFTP Server is on the other side, the
client might not be able to access the TFTP server properly. Because per
TFTP RFC the server uses a dynamic port as source port for response
packets which is detected as unsolicited by stateful firewalls and
dropped. Unlike FTP this dynamic port number is not negotiated so
stateful firewall cannot implement an ALG (unless ignoring the source
port numbers completely which reduces the effectiveness of the firewall
and is not desirable).

Such a problem did surface while updating firmware of a VOIP phone using
TFTP (not u-boot related but could have been).

Now, typically the TFTP server and the U-Boot host is not seperated by a
firewall but it could be in some situations. I personally do not need it
but I can see it may be needed by some. A very basic lightweight and
tight TCP support could be developped for FTP support. There are some
TCP implementations for really limited resource hosts.