Michael's musings

Sat, 26 Dec 2009

IPv6 with mcast UserModeLinux backends

I am doing some work with IPv6. (see http://bluerose.sandelman.ca/projects/show/unstrung )

I have a test network shown at: http://bluerose.sandelman.ca/repositories/changes/unstrung/doc/network-1.png

In automated testing I would normally use the daemon mode, with uml_netjig. In casual use, I was using the mcast backend, because it has fewer moving parts.... but my network interfaces kept remaining in state "tentative" and I could not send packets.

What was the problem, I debugging for awhile through the IPv6 code, and finally thought that it had something to do with the UserModeLinux network interface never providing low-level LINK "UP" signal, and so it never did Duplicate Address Discovery, and remove the tentative mark.

5: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
    inet6 fe80::1000:ff:fedc:bcff/64 scope link tentative
       valid_lft forever preferred_lft forever
6: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
    inet6 fe80::1000:ff:fe64:6423/64 scope link tentative
       valid_lft forever preferred_lft forever

Note that it says "tentative".

NO! DAD was occuring just fine, but it FAILS. Why? Because it thinks it has a duplicate... finally I noticed

eth0: duplicate address detected!
eth1: duplicate address detected!

Why is this? It's because the mcast interface gets a copy of the packets that are output. I.e. it hears itself. DAD should work even when that happens, I think.

I need to look at whether the mcast interface should be fixed (remember it's own packets and ignore them? Drop packets that originate from it's own MAC address?), or should DAD be fixed?

Wed, 02 Dec 2009

Profit on Farmville

I'm level 14 on Facebook's Farmville. Why do I play? Because my 4yr old likes it. Of course, I want to maximize my profit.

I only run it about once a day, so crops that wither before I can harvest them are out, but what next? It costs 15 coins to plow the field each time.

It turns out that longer growing crops aren't worth much more. I did a spreadsheet to work things out.

cost sell harvest profit profit/day wheat 35 115 3.0 65 21.7 eggplant 25 88 2.0 48 24.0 artichokes 70 204 4.0 119 29.8 daffodils 60 135 2.0 60 30.0 squash 40 121 2.0 66 33.0 soybeans 15 63 1.0 33 33.0 cotton 75 207 3.0 117 39.0 bell-peppers 75 198 2.0 108 54.0 aloe vera 56 85 0.2 14 56.0 strawberries 10 35 0.2 10 60.0 cranberries 55 98 0.4 28 67.2 pumpkin 30 68 0.3 23 69.0 rice 45 96 0.5 36 72.0 peppers 70 162 1.0 77 77.0 raspberries 20 46 0.1 11 132.0 </pre>

Raspberries take 2 hours. Sometimes worth it, but the profit margin is very low unless you do it all day long.

Ruling out the things that take less than a day, leaves me with peppers, bell-peppers, and cotton as the highest grossing.

Too bad that the market price didn't depend upon other factors, like how many other people were growing it... or if you grew some things properly, you could keep the seed.

Or maybe you have to rotate your crops. Or grow eggplants next to pumpkin will keep away the racoons, or the blight.