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

[Tolunay Orkun]

Wolfgang Denk wrote:
> In message <E89EC5FBB92CAB4C9BB301E636B0D858075C14 at 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.