Strange TCP problem with awge0

[Martin Husemann <martin%duskware.de@localhost>]

A strange network problem, reproducable on netbsd-current when using an
ARM device with awge network interface (basically all Allwinner boards)
has been reported to me:

Simply trying to get anything from one of the KDE mirror sites fails
like this:

> ftp ftp://ftp.solnet.ch/mirror/KDE/stable/
Connected to ftp.solnet.ch.
220-  __ _                    _            _         _     
..
331 Please specify the password.
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.

421 Service not available, remote server timed out. Connection closed.


When running Raspbian on affected hardware and using tnftp, the transfer
"works":

...
331 Please specify the password.
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
200 Switching to Binary mode.
250 Directory successfully changed.
550 Failed to change directory.
221 Goodbye.


This is very reliably 100% reproducable, for me and others (with a totally
different network connection, so it is neither my ISP nor my router).

I have created some packet captures and stared at them, but I can't see
what is wrong - looks like the ftp server is not seeing/acking our last
packet, but *why* is that so, and why reproducably?

Also it works fine with other machines running netbsd-current on the same
network connection, so first bet would be a driver bug.

The traces are taken from the outside interface of my NAT/router:

http:://www.netbsd.org/~martin/ftp_from_raspbian.pcap
	this is the working (Linux) one

http:://www.netbsd.org/~martin/ftp_from_netbsd.pcap
http:://www.netbsd.org/~martin/ftp_from_netbsd_2.pcap
http:://www.netbsd.org/~martin/ftp_from_netbsd_3.pcap
	various tries from a netbsd system (did I mention reproducable?)

http:://www.netbsd.org/~martin/ftp_from_netbsd_internal.pcap
	another try from netbsd, but this time captured on the internal
	interface of the NAT.


Any hints?

Martin