[HN Gopher] Let the network tell you where you are
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Let the network tell you where you are
Author : zdw
Score : 69 points
Date : 2024-10-02 03:45 UTC (4 days ago)
(HTM) web link (rachelbythebay.com)
(TXT) w3m dump (rachelbythebay.com)
| jackweirdy wrote:
| This couldn't have been better timed for me.
|
| I sit with a pile of raspberry Pis I throw into different rooms
| about the house and want to stick assorted tasks on them. My open
| question was how can I just image them, plug them in and
| centrally configure what runs on them with no more sd card or Mac
| detection shenanigans when I change their job.
|
| I'll be giving this a try!
| ajb wrote:
| If lldp proves inconvenient, pi's also have a unique cpu-id,
| which can be found in /proc/cpuinfo
|
| I think something similar exists on most processors
| jagged-chisel wrote:
| How does cpu-id map to physical location? If I move it from a
| closet on the first floor, to a rack in the basement, how
| does knowing the cpu-id help?
| ajb wrote:
| You would use CPU id by having the vanilla image display
| its ID (or perhaps some more humanly readable derived name)
| until assigned something to display. It won't know that
| it's moved, that's an advantage of the port method.
|
| I mentioned it because the OP was going to use Mac
| addresses in a similar way, and only didn't because the Mac
| addresses of her machines were unstable.
| bagels wrote:
| How fun, I solved a similar problem in a similar way. 90
| identical devices, each with their own Ethernet cable and 128
| Ethernet ports. The solution was to configure the switch to make
| DHCP assignments based on port number, then the device could just
| query its own IP address. Port 1 -> 192.168.1.101, 99 ->
| 192...199
| jeffrallen wrote:
| LLDP: this is the way
|
| But also, I was wondering if she was going to say, "these devices
| have cameras on them which are not used because they are pointed
| in random directions depending on how they are mounted". And then
| I was hoping to see an interesting image recognition task, "given
| this blurry, dim, random image, choose which location it probably
| came from".
|
| I got nerd sniped to the power of 2.
| Rygian wrote:
| Same could work with microphones. Every spot of the space would
| have a different resonant characteristic.
|
| Or microphone+speakers, where every device can self-assign an
| ID, echo it over speakers, and then everyone triangulates
| everyone else and themselves.
| jtchang wrote:
| What switches enterprise or consumer tend to support this LLDP?
| My guess is maybe almost none on the consumer side. I.e. Netgear,
| to link. Cisco probably does. How about ubiquti?
| tcrenshaw wrote:
| I know mikrotik supports this. On the higher end, most of the
| Dells switches I interacted with as well as Aruba had LLDP.
| Different manufacturers tend to report their interfaces
| slightly differently though
| hackmiester wrote:
| Almost any managed switch will support it. Netgear does.
| Ubiquiti definitely does, even their APs do.
| client4 wrote:
| Used Arista 7124 and 7150s are pretty cheap on Ebay.
| Palomides wrote:
| anything that can run openwrt
| eqvinox wrote:
| Nope, you need switch silicon with a driver that punts
| 01:80:c2:0:0:0e to cpu. A lot can do this but not all
| (generally a driver issue, not HW limitation.)
| eqvinox wrote:
| Anything with a management interface (even web) could do it
| from the HW side, just a question of SW support. Netgear does
| support it on managed switches.
|
| The protocol is old enough and very well established by now,
| even modern Windows boxes run it by default.
| mft_ wrote:
| Very interesting!
|
| Somewhat related, years ago I worked in an office that switched
| to hot-desking, and I spent a while trying to figure out whether
| was there was a way to automatically generate a map of who was in
| the office, and whereabouts. Identifying an individual laptop is
| okay, but figuring out which docking station the laptop was
| plugged into was a lot trickier without admin access to network
| hardware (which I def didn't have). This approach may have
| allowed an individual laptop to figure out where it was, and then
| update a central location database.
| pimlottc wrote:
| I suspect this referring to a recent post on jwz's blog about his
| digital signage solution for his nightclub, which spawned a lot
| of discussion on the comment (click through to the blog post
| itself):
|
| https://mastodon.social/@jwz/113209773692118053
|
| (intentionally linked via Mastadon because he doesn't appreciate
| direct links from HN)
| theideaofcoffee wrote:
| You don't even need to go so far as to sniff traffic on any
| interface. Most linux distros have either lldpd or lldapad built
| in which gives a bit higher-level interface to the raw LLDP data
| on the wire. The BSDs also have it. Bi-directional so info can be
| updated switch-side too. I've used it in combination with other
| tools, DHCP and whatnot to do something similar to what she wrote
| about, have individual machines 'know' where they are in a
| cabinet or facility and change functionality based on that. Works
| great!
| gruturo wrote:
| This assumes your paranoid network admins don't disable CDP/LLDP
| one day because of nebulous "security reasons" and sabotage your
| scripts, but this is the wrong time and place to rant about that
| :)
|
| Cool hack!
| 9x39 wrote:
| I think that's a real risk for anyone not doing their own DIY
| network and/or able to require the network to offer (or least
| not block) it.
|
| Depending on protocols nobody expects you to be depending on
| can be risky, particularly with all the pathologies of working
| with multi-team corp operations...
|
| To some degree, beyond a tiny scale, building on CDP/LLDP is
| probably fighting uphill. From my perspective working with
| audio/visual (AV) teams and corporate IT, it's maybe safer to
| do your location and stream management out of band in some kind
| of overlay (app or network protocol), and just have the network
| serve you multicast streams that you request.
|
| That is, a receiving device is programmed out of band (manually
| or by some management scripting) to subscribe to a particular
| IP multicast stream and the network's job is just delivery
| through IGMP+PIM. This is the rough model most AV technologies
| seem to be following, even to the point of collapsing
| receiver/decoder boxes into the TV itself.
|
| But, sometimes there's nothing like scratching your own itch,
| though.
| eqvinox wrote:
| LLDP-MED actually has fields for location information, though
| they were designed for E911 on VoIP (so the switch can tell the
| phone where it is) and might not be detailed enough.
| g1sm wrote:
| She mentioned she can't rely on DHCP for deterministic address
| assignment, but if one _can_ rely on DHCP and has a sufficiently
| smart switch, one can use DHCP option 82 to identify the end
| device based on which switch and switchport it is connected to.
| This then allows for all kinds of customizations without any
| "cooperation" from the end device.
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