BlueMSX bug on ObsoNET emulation?

Por konamiman

Paragon (1159)

Imagen del konamiman

31-03-2010, 10:23

For the development of InterNestor Lite 2.0, which will be compatible with the new TCP/IP UNAPI specification, I am using BlueMSX and taking advantage of his ObsoNET emulation. I must say that it has saved my life since currently it is a lot easier for me to use an emulator than to use my real MSX (which is very sad, but I can't choose).

I have however found which I think is a bug on the ObsoNET emulation or the network handling. Take a look at this screenshoot:

www.konamiman.com/images/BlueMSXObsonetBug.png

You can see that for the first PING request, I receive multiple responses. I have verified with a packet sniffer that, indeed, the PING request is actually sent multiple times, so the responses are legitimate. The request whould be sent only once.

Further PING requests work fine, being sent only once. Further investigation has shown me that the problem shows only when the MAC address of the destination (the router in this case, since it is an external address) is unknown and must be obtained via ARP. InterNestor caches the IP datagram to be sent in this case and sends an ARP request; as soon as the reply is received, the cached datagram is sent.

I have debugged to death and I am completely sure that InterNestor sends the datagram only once. Also, I have verified that this does not happen with a real MSX, neither with ObsoNET nor with DenyoNet. By the way the same problem appears with InterNestor 1.

So, to the best of my knowledge, I think that it is a bug on BlueMSX.

It is not a big issue since receiving duplicate PING replies is not a critical problem, TCP uses sequence numbers to deal with duplicate data, and any protocol based on UDP has duplicate detection mechanism as well. But I think it is worth to take a look in case that BlueMSX developers are somewhat bored. :)

Login sesión o register para postear comentarios

Por Sd-Snatcher

Hero (582)

Imagen del Sd-Snatcher

31-03-2010, 19:28

Por konamiman

Paragon (1159)

Imagen del konamiman

01-04-2010, 19:42

LOL, the invasion of the zombie MSXes! Tongue

Por Manuel

Ascended (18384)

Imagen del Manuel

02-04-2010, 12:27

That url gives me a 403 error....

Por Sd-Snatcher

Hero (582)

Imagen del Sd-Snatcher

02-04-2010, 16:01

it happens the first time, reload (f5)

Por Manuel

Ascended (18384)

Imagen del Manuel

02-04-2010, 23:15

That doesn't help.


Forbidden

You don't have permission to access /msx/bluemsxestrestest.png on this server.

Por spl

Paragon (1470)

Imagen del spl

03-04-2010, 01:28

Same error also

Por Sd-Snatcher

Hero (582)

Imagen del Sd-Snatcher

03-04-2010, 17:00

Very strange...

Again:

img263.imageshack.us/img263/6761/bluemsxestrestest.th.png

Por gargamel

Expert (101)

Imagen del gargamel

01-05-2010, 20:57

Thanks, for the extensive report. Smile

This sounds like an exciting investigation, also of the packet driver. Until then, we should call it feature. Wink