Amazon dash button plugin available

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@michbeck100 Ah, ok. I thought the library gets installed automatically via pre-install. Maybe, this is something worthwhile to consider.

@mwittig it definitely is. I don’t have any experience in using the node pre-install feature. If you have some good resources send me a pm.
But I think it’s not possible to install these dependencies since they are installed using apt-get (or any other package manager depending on the OS)

Thanks for the plugin. I’ve just ordered 2 buttons Since i’m running Pimatic and Kodi on the same Raspi 3, i’m wondering how much CPU load the ARP request sniffing will cause. Especially during streaming of movies over the LAN port from a NAS. There will be a lot of packets, which have to be processed by pcap. If the load is too high, there is still the possibility to activate the onboard WLAN and use it only for pcap sniffing.

@GooglyEyz CPU load seems to be fine but the memory consumption seems to have increased since using the plugin. I’ll have to test if it’s better when the plugin is deactivated, though.

@michbeck100 said in Amazon dash button plugin available:

Sorry, can’t reproduce this error. Anyone else having problems? @mwittig maybe?

Getting back to this, I can reproduce this problem, now. It occurs if the device had been added a to view page. When you do this you will see another error at first: Client error: Cannot read property '__ko__1473100260719' of null. After this the front-end will no longer properly render and you’ll get the other error. I think the reason is that you’re using a “templete” which is unkown in the frontend, i.e. “dashbutton”. It should be needed that the devices gets added to view though, so the error won’t disappear after restart. It can be resolved by opening the Configuration Editor to manually remove the device from the view.

EDIT: Ihave created a ticket for this issue on github.

I think the mobile frontend should be more robust against such errors. For the time being, users shall not add the DashButtonDevice to view pages.

@michbeck100 said in Amazon dash button plugin available:

but the memory consumption seems to have increased since using the plugin

Presumably, most of the memory is used for libpcap’s ringbuffer, which stores the already received packages. It is possible to tweak the allocated size which should be a multiple of the maximum packets size plus some slack needed to maintain packets as part of the ringbuffer. See pcap_set_buffer_size()

@mwittig
The pcap man page says:

buffer size
Packets that arrive for a capture are stored in a buffer, so that they do not have to be read by the application as soon as they arrive. On some platforms, the buffer’s size can be set; a size that’s too small could mean that, if too many packets are being captured and the snapshot length doesn’t limit the amount of data that’s buffered, packets could be dropped if the buffer fills up before the application can read packets from it, while a size that’s too large could use more non-pageable operating system memory than is necessary to prevent packets from being dropped.
The buffer size is set with pcap_set_buffer_size().

The default size used in node_pcap is 10 MB for the buffer. As i think that there shouldn’t be so many ARP request per time in a standard home, so i guess 2 MB should be enough. What do you think? Remember ARP requests are issued once a device connects to a network.

@GooglyEyz I have analyzed the difference in memory usage since activating the plugin. It did increase by about 10 MB, so i guess @mwittig is right about the buffer size. For the time being an increase of 10 MB is still not that much of a problem.

@michbeck100 said in Amazon dash button plugin available:

The default size used in node_pcap is 10 MB for the buffer. As i think that there shouldn’t be so many ARP request per time in a standard home, so i guess 2 MB should be enough. What do you think? Remember ARP requests are issued once a device connects to a network.

Yes, 2 MB should be more than enough. I have tested this with 600k which works flawlessly on a Pi 3. As it is possible to let libpcap (pre-)filter the incoming packet stream for ARP packets the memory required should be really low as the size of an ARP packet on the wire normally normally is less than 64 bytes.

@mwittig The plugin already filters just for ARP packages. I just didn’t change the default buffer size. The next update will bring a decrease to 1 MB. Just to be sure.

@michbeck100 said in Amazon dash button plugin available:

The plugin already filters just for ARP packages.

That’s great! It would also be possible to filter ARP packets for the MAC vendor ids, but I don’t think it will improve performance / memory usage as the number of ARP requests on a home network normally is relatively low.

https://ask.wireshark.org/questions/35546/filter-mac-address-of-a-particular-manufacturer

I just didn’t change the default buffer size. The next update will bring a decrease to 1 MB. Just to be sure.

This make sense to me.

@mwittig My plugin already does this, too. I’m filtering just for addresses registered for Amazon Technologies Inc. These addresses can be found here: https://regauth.standards.ieee.org/standards-ra-web/pub/view.html#registries

@michbeck100 said in Amazon dash button plugin available:

My plugin already does this, too.

Yes, I know, but I was referring to letting libpcap do the (pre-)filtering for you so that the “pcap session” will only retrun ARP requests from Amazon devices. ,As libpacap filtering is performed in kernel mode the advantage would be, that lesser context switches are required as lesser ARP packages will be passed to the application (pimatic) running in the user space.

@michbeck100 Wow, good to have someone who’s experienced with libpcap . I’ll have a look into this.
EDIT: reminder to myself created: https://github.com/michbeck100/pimatic-dash-button/issues/4

@mwittig Do you have any clue how the filter string should look like?
I guess it should be something like

arp ether[6:2] == 0x0011 and ether[8:1] == 0x22

for addresses starting with 00:11:22. I got this filter value from http://stackoverflow.com/questions/13086766/how-to-filter-mac-addresses-using-tcpdump

@michbeck100 said in Amazon dash button plugin available:

Wow, good to have someone who’s experienced with libpcap

Great. I have posted an example to the issue ticket you’ve created.

Just released version 0.1.0 of pimatic-dash-button. This version fixes all the issues reported since now (see README.md for a change log).
Additionally i’ve changed the dash button device to act like a ButtonsDevice with one fixed button, that can be pressed. This way you can also “press” the dash button from the UI.

Looks like they’re on sale today!!
Look here!

@Stokstaart that’s just in the US right? I think they don’t deliver to Europe

@michbeck100 unfortunately looks like it, too bad i live in Europe (altough i hear living in America isn’t what is was… )