[U-Boot] How to download image to U-Boot

[Grant Edwards]

I've read through the U-Boot manual and FAQ, but I still
haven't figured out how one downloads via the network an image
to a board running U-Boot.  Previous projects have used
RedBoot, and it provided a couple different mechanisms: 

 1) Telnet to the board and download an image (binary or
    S-Record) using the x/y-modem protocol over the telnet
    connection.

 2) Download a binary image directly using a TCP connection
    to a dedicated port.

Both of these methods would work through firewalls and WAN
connections (even through satellite links), and could easily be
automated in an "updater" utility that is then provided to
customers to update images in flash.

I can't seem to find out how one accomplishes the same task
using U-Boot.  The only method I can figure out involve setting
up a TFTP server (which is not going to be acceptible to
customers), and then typing a series of commands while plugging
into a serial console (also not going to be acceptible to
customers).  The requirement is to update the image using just
the network and a user-space application that doesn't require
any system privledges to run.

I found mention of netconsole, but I don't see how it's useful
since you have to know a-priori the address of the machine from
which you want to use it.  It would seem that you have to force
the customer to change the IP address of their machine (not
acceptible).

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