Why don't al DHCP hosts show up under 'DHCP Clients'

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Fried Chicken
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PostPosted: Sat May 14, 2022 7:39    Post subject: Why don't al DHCP hosts show up under 'DHCP Clients' Reply with quote
In the status page, I have a computer connected, working, pingable, etc. It has an assigned IP address, everything is working fine, but it doesn't show up under "DHCP Clients".

Also many hostnames are left blank. I've chalked this up to some inherent way DHCP works, but it doesn't make sense to me. Shouldn't by necessity every active client have its IP address and hostname listed?

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ho1Aetoo
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PostPosted: Sat May 14, 2022 8:03    Post subject: Reply with quote
Only devices that have received DHCP data since the last reboot are displayed under DHCP Clients.

Clients that may not have received any data:

* manually configured clients that do not use DHCP
* clients using DHCP reservation (without lease expiration)
blkt
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Joined: 20 Jan 2019
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PostPosted: Sat May 14, 2022 9:10    Post subject: Reply with quote
Computer has previous lease information, router forgot after reboot.

Reconnect or reboot your computer and it should show up in the list.

The nature of embedded devices at least until lease expires, renews.
the-joker
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PostPosted: Sat May 14, 2022 9:12    Post subject: Reply with quote
Not my experience, see https://forum.dd-wrt.com/phpBB2/viewtopic.php?p=1262405#1262405

I then set static leases with an expiry of 15 minutes for these missing devices, rebooted the devices (NAS boxes), this should have triggered a DHCP request from devices and it did, and even after this, not all devices reliably show, I still had missing devices that didn't show up even after accessing them and sending data/receiving data.

These are all wired devices.

Rebooting dd-wrt and devices (power cycle) still same, not all show up, its a random bag of fun.

The only one that reliably shows up is the first static IP assignment and non expiring lease, which is my main dev machine. Also all wifi devices will show up (non expireing leases), but wired YMMV no matter if lease expires.

Dnsmasq afaik is a test version daemon.info dnsmasq[22957]: started, version 2.87test8 cachesize 1500 so this could have some influence on the reliability.

Im running latest 48865, I remember much older builds that always showed all devices without fail, so clearly bugs were introduced upstream, on the project (which is not developed by dd-wrt.

In the meanwhile, tumbleweeds.

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Last edited by the-joker on Sat May 14, 2022 9:29; edited 1 time in total
ho1Aetoo
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PostPosted: Sat May 14, 2022 9:28    Post subject: Reply with quote
So that clients with DHCP reservation are not shown under "DHCP clients" is already quite a few years (I can't remember that it was ever different!).

and with me it works exactly as I have described it above.

I just have to log in to such a client and restart the network and suddenly the client is displayed again.

Code:
/etc/init.d/networking restart
Running /etc/init.d/networking restart is deprecated because it may not enable again some interfaces
Reconfiguring network interfaces...
udhcpc started
No resolv.conf for interface eth0.udhcpc
Sending discover...
Sending select for 192.168.1.109...
Lease of 192.168.1.109 obtained, lease time 268435455
/etc/udhcpc.d/50default: Adding DNS 192.168.1.1


no problems here!



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the-joker
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PostPosted: Sat May 14, 2022 9:34    Post subject: Reply with quote
It use to work fine, I remember this was not an issue, but since at least this year, it started going flaky, perhaps even the last builds from 2021.

Its not a stable release of the dnsmasq anyway... This is the culprit, need to check upstream for bug reports

https://www.mail-archive.com/dnsmasq-discuss@lists.thekelleys.org.uk/ pff, whos got time for that?

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kernel-panic69
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PostPosted: Sat May 14, 2022 10:47    Post subject: Reply with quote
Haven't bothered to see if any post test8 upstream commits have been applied, but.

https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=summary

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the-joker
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PostPosted: Thu May 19, 2022 8:14    Post subject: Reply with quote
The current dnsmasq git master includes interesting commits that may address some of the issues.

https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=shortlog

But since there is no test9 release yet, I dont think it will be merged into DD-WRT until such time.

From experience and generally speaking, bleeding edge (i.e. running test/master code) is a mixed bag between fixed bugs and possibly introduced issues/stability in general since the code is not mature enough and not widely tested by a large enough pool of users.

Problem is 3rd party projects like DD-WRT, most users who encounter issues with anything DD-WRT uses, dont report it to the projects upstream responsible for their development, intead report it in the 3rd party project.

These developers dont go around chasing reports here or anywhere, so it could happen that the bugs are never fixed, and we cant blame DD-WRT or the upstream project.

I would suggest our community report bugs with 3rd party libs upstream absolutely without fail and following their bug reporting processes, but this is unlikely to have any effect, and likely outcome of any reports would only include vague data attached, like (it doesn't work).

Im off...

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ho1Aetoo
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PostPosted: Thu May 19, 2022 8:57    Post subject: Reply with quote
The major projects all use the test and RC versions.

See Pi-Hole project:

https://github.com/pi-hole/FTL/releases

Quote:
v5.14

Update embedded dnsmasq to v2.87test8

v5.13

Update embedded dnsmasq to v2.87test4-18

v5.12

Update embedded dnsmasq to v2.87test4-6


etc....


Partially also non-public versions are used

https://svn.dd-wrt.com/changeset/45026

Quote:
dnsmasq-pre-2.83


The reason is simply that the test / RC versions contain important CVE fixes and the next release is far away.

Also, as I said, the test versions are used by all projects anyway!

And for me personally there is also nothing to report - because I have no problems with the current version, neither on the dd-wrt router nor on my Pi-Hole


Last edited by ho1Aetoo on Thu May 19, 2022 9:21; edited 1 time in total
the-joker
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PostPosted: Thu May 19, 2022 9:20    Post subject: Reply with quote
Well, this guy has stumbled on an issue I also stumbled on https://forum.dd-wrt.com/phpBB2/viewtopic.php?p=1262894#1262894 for different reasons.

and other people also report random bags of fun with dnsmasq which I also stumbled on.

That said, its not about projects using or not rc, new code like I said is not mature enough and has limited pool of testers, and any 3rd party projects users rarely report issues upstream.

Your situation or setup could exclude you from stumbling on said issues anyway. This doesn't mean there are no issues.

RE: CVE's if a project fixes a CVE only in master/rc builds and doesn't release a version asap (e.g. previous stable release with ported fixes), this is the same as ignoring the CVE altogether. ANY Distros that are not rolling releases dont use rc's, therefore rely only on backports of said fixes, luckily backports happen.

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