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Apprentice

lack of DHCP-linked DNS view

Hi,

 

my old router (LInksys E4200) provided a DHCP-linked DNS view. When I added a local computer to my network, it responded to DNS queries for its name with its address.  The AX4200/RBR750 I just bought does not :-(

 

I looked a little bit at its software.  It seems to be running Busybox's udhcpd for its DHCP and dnsmasq for its DNS forwarding. I don't immediately see how they do that, though, as I can't spot how dnsmasq's DHCP server functionality is disabled.

 

dnsmasq is run as

 

dnsmasq -h -n -c 0 -N -i br* -r /tmp/resolv.conf -u root root

 

and udhcpd is run with this config:

 

# cat /tmp/udhcpd.conf
pidfile /tmp/udhcpd.pid
start 192.168.1.15
end 192.168.1.254
interface br-lan
remaining yes
lease_file /tmp/udhcpd.leases
option subnet 255.255.255.0
option router 192.168.1.1
option dns 192.168.1.1
option lease 86400
option domain

 

/tmp/udhcpd.leases contains the local client information, including their hostnames.

 

Question: has anyone debugged this further?

 

Is there a way to get the Netgear device to provide a DHCP-linked DNS view?

Message 1 of 13
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Guru

Re: lack of DHCP-linked DNS view

I would point out that if one mfr has one feature that this doen't mean it would be seen or should be seen with nother mfr. 

 

Each Mfr may have reason why they don't have some or similar features in there products. You're basing your observations on a 9 year old router aswell. Older tech. I believe Orbi systems and probably other NG products are based on more simplistic designs for the common house hold user. Not much advanced or granular features as seen back then. Thus no deep dives into some features that seem missing. Just not used for the average home user. 


My Setup (Cable 900Mbps/50Mbps)>CAX80>Orbi RBK50 v2.5.1.16(Router Mode)
Additional NG HW: C7800/CM1100/CM1200, Orbi CBK40, Orbi RBK50/RBK853, R7800, R7960P, EX7500/EX7700, XR450 and WNHDE111
Message 2 of 13
Highlighted
Guru

Re: lack of DHCP-linked DNS view

This feature does come essentially free as it's perfectly implemented with dnsmasq - required would be a default local domain with the default config, the ability to change the default domain in a config field, and some better check of the hostnames provided by the DHCP clients (to avoid breaking dnsmasq). Every major consumer router has it, Asus, AVM/Fritz!, ..., ZyXEL ... for years of not at least a decade. One of many features proofing Netgear is unable and unwilling to change anything on these 1990 router specs.

Message 3 of 13
Highlighted
Guru

Re: lack of DHCP-linked DNS view

It can certainly be requested here:

https://community.netgear.com/t5/Idea-Exchange-For-Home/idb-p/idea-exchange-for-home

 


My Setup (Cable 900Mbps/50Mbps)>CAX80>Orbi RBK50 v2.5.1.16(Router Mode)
Additional NG HW: C7800/CM1100/CM1200, Orbi CBK40, Orbi RBK50/RBK853, R7800, R7960P, EX7500/EX7700, XR450 and WNHDE111
Message 4 of 13
Highlighted
Guru

Re: lack of DHCP-linked DNS view

When you search the Idea Exchange for Home for DHCP and DNS you find eleven entries, representing about seven or eight valid feature requests for features people expect on thier routers in weeks, and not probably in seven years when Netgear CBU has grown up from their first (ZyXEL) OEM router from 1899 or so. Named OEM has changed since. Netgear hasn't.

 

For you reference - here is the request for Orbi: https://community.netgear.com/t5/Idea-Exchange-For-Home/orbi-add-dns-server/idi-p/1474376 ...oh there are even hacks shown on how to make it happen on an experimental base.

 

Has anything requested implemented from that list the last ten years? 

Message 5 of 13
Highlighted
Apprentice

Re: lack of DHCP-linked DNS view

Thanks for the link. I kind of thought it's a known issue, but I was confused which forum to search. Do all Netgear devices use a more or less shared code base?

 

In any event, the hack proposed there probably isn't going to work on the RBR750 in my possession. /tmp/dhcpd_hostlist doesn't exist.  Also, FWIW, it's not clear from a quick scan of the dnsmasq man page how often it polls any files listing additional hosts, or whether they are read only on startup. (This may not be a big issue since presumably the set of hosts isn't changing frequently.) Plus, they pass -n to prevent dnsmasq from polling even the resolv.conf file for changes.

 

All in all, my first impression from looking at their OS is that it seems cobbled together.

 

I'm not surprised by government warnings like these,

See also.

 

Kind of makes me regret shelling out $400 based on good reviews of the AX6 series together with the fact that Netgear at least doesn't require an App to set up (this was my 2nd must have).

 

 

 

Message 6 of 13
Highlighted
Apprentice

Re: lack of DHCP-linked DNS view


@FURRYe38 wrote:

I would point out that if one mfr has one feature that this doen't mean it would be seen or should be seen with nother mfr. 

 

Each Mfr may have reason why they don't have some or similar features in there products. You're basing your observations on a 9 year old router aswell. Older tech. I believe Orbi systems and probably other NG products are based on more simplistic designs for the common house hold user. Not much advanced or granular features as seen back then. Thus no deep dives into some features that seem missing. Just not used for the average home user. 


Finding a hostname of a connected device is, if anything, something the "common household user" needs because they expect to find their computers on their network without needing to use/know their IP address.

 

Perhaps reply a little bit less often?

 

Message 7 of 13
Highlighted
Guru

Re: lack of DHCP-linked DNS view

Maybe however again, your dealing with the average home user. NG tried to employ there own host name or device naming scheme of things so this is what is need in the UI or the Orbi app. 

 

Good Luck. 


My Setup (Cable 900Mbps/50Mbps)>CAX80>Orbi RBK50 v2.5.1.16(Router Mode)
Additional NG HW: C7800/CM1100/CM1200, Orbi CBK40, Orbi RBK50/RBK853, R7800, R7960P, EX7500/EX7700, XR450 and WNHDE111
Message 8 of 13
Highlighted
Guru

Re: lack of DHCP-linked DNS view

All consumer vendors are carrying forward standard code, daemons, ... Here it has hit a simple httpd carried forward for a long time, in the mean time the problesm was fixed for few models - then the old code returned. It's careless code management ...   Here are often derivatives of some low footprint code, wrapped over awful and even more crappy chip vendor dev kits (often prohibiting using reasonabe Linux code), so often it happens for devices using kind of similar chipsets that' the base code is carried forward ... that's how the XR300 (that's the "newest" router model that hits my eyes on that vulnerability) came into the lists.

 

Your Orbi AX system isn't affected, there is a newer Web server code in place.

I have spent reasonable time on making Netgear change some code line for a late 802.11ac router (as that one runs on a generic computing platform) - if an how this time and resources was worth and carried forwards or not to similar and newer router model lines.


Message 9 of 13
Highlighted
Apprentice

Re: lack of DHCP-linked DNS view

To answer one of the questions I raised - why aren't udhcpd and dnsmasq conflicting; I learned that dnsmasq was built without support for DHCP:

 

# dnsmasq -v
Dnsmasq version 2.78  Copyright (c) 2000-2017 Simon Kelley
Compile time options: IPv6 GNU-getopt no-DBus no-i18n no-IDN no-DHCP no-scripts no-TFTP no-conntrack no-ipset auth no-DNSSEC loop-detect inotify

This software comes with ABSOLUTELY NO WARRANTY.
Dnsmasq is free software, and you are welcome to redistribute it
under the terms of the GNU General Public License, version 2 or 3.
Message 10 of 13
Highlighted
Apprentice

Re: lack of DHCP-linked DNS view

 
@schumaku wrote:

All consumer vendors are carrying forward standard code, daemons, ... Here it has hit a simple httpd carried forward for a long time, in the mean time the problesm was fixed for few models - then the old code returned. It's careless code management ...   Here are often derivatives of some low footprint code, wrapped over awful and even more crappy chip vendor dev kits (often prohibiting using reasonabe Linux code), so often it happens for devices using kind of similar chipsets that' the base code is carried forward ... that's how the XR300 (that's the "newest" router model that hits my eyes on that vulnerability) came into the lists.

 

Your Orbi AX system isn't affected, there is a newer Web server code in place.

I have spent reasonable time on making Netgear change some code line for a late 802.11ac router (as that one runs on a generic computing platform) - if an how this time and resources was worth and carried forwards or not to similar and newer router model lines.



Interesting. I took a closer look at what they're running.

 

A number of daemons appear to related to BitDefender, a service I do not use or know of.

Then, there is a directory /tmp/aws_json_dir that contains a number of files with the result of a Fing scan of my network.

 

So Netgear doesn't implement a DHCP-linked DNS view, but they do send the DHCP fingerprint of all devices located on my local network to a server in the AWS cloud (there's a program called 'aws_json' that appears to do that.)  Ironically, this includes whether the DHCP client used option 12.

 

Interesting priorities.  I haven't even checked what privacy policies I must have agreed to when buying this device that allows them to scan and fingerprint my network (including MAC addresses, OS versions, Hardware guesses, etc.) and collect this information.

 

FWIW, Fing doesn't appear to be high quality software, fortunately. It scanned my Linux machines as running Windows.

Message 11 of 13
Highlighted
Guru

Re: lack of DHCP-linked DNS view


@gb777 wrote:

A number of daemons appear to related to BitDefender, a service I do not use or know of.


Netgear does make use of BitDefender (and probably some more) under the name Netgear Armor where e.g. BitDefender vulnerabiity scans are run from the router on all attached devices.

 


@gb777 wrote:

Then, there is a directory /tmp/aws_json_dir that contains a number of files with the result of a Fing scan of my network. ... but they do send the DHCP fingerprint of all devices located on my local network to a server in the AWS cloud (there's a program called 'aws_json' that appears to do that.)


Just guessing - this is probably related to have a more or less complete inventory on the attached devices to run adjusted scans. Ok, I?m wearing my green glasses today.

 


@gb777 wrote:

So Netgear doesn't implement a DHCP-linked DNS view, ...  Ironically, this includes whether the DHCP client used option 12.

Interesting priorities.


Have looked into the R9000 here again - no Armor so luckily none of the above. However of course typical behaviour:

 

  • Appears dnsmasq (v2.80 as I nagged - and of course that's carried ahead to other newer products - there are known vulnerabilities on 2.78 and 2.79 ... so why bother, Netgear?) is built here _with_ DHCP support, but there is no DHCP config.
  • Instead, the Busybox (one of my favourites due to the very incomplete shell functionality) integrated udhcpd (and udhcpc) seems to be in place now.
  • Checking the config does show:
    ---
    root@R9000-1:/# cat /tmp/udhcpd.conf
    pidfile /var/run/udhcpd.pid
    start 192.168.10.1
    end 192.168.10.253
    interface br0
    remaining yes
    auto_time 5
    lease_file /tmp/udhcpd.leases
    ---
    While the /tmp/udhcpd.leases file does exist, it's never touched or updated - obviously a bug. OK, I'm testing with Android 10 and 11 systems not providing a host name.
    ---
    root@R9000-1:/# ls -als /tmp/udhcpd.leases
    0 -rw-r--r-- 1 root root 0 Jan 1 1970 /tmp/udhcpd.leases
    ---

This would make updating the local DNS somewhat difficult. Same on your Orbi @gb777 ?

These are the reasons why there is still no local DHCP-hostname DNS update.


@Christian_R please share these issues and bugs with the consumer business unit...


@gb777 wrote:

Interesting priorities.  I haven't even checked what privacy policies I must have agreed to when buying this device that allows them to scan and fingerprint my network (including MAC addresses, OS versions, Hardware guesses, etc.) and collect this information.


Security software under the Armor label does certainly sell better than a DHCP-DNS integration - especially as it is bundling the BitDefender for Android, iOS (somewhat basic), Windows, and MacOS for the customer's client devices.

 


@gb777 wrote:

FWIW, Fing doesn't appear to be high quality software, fortunately. It scanned my Linux machines as running Windows.


Wondering for a longer time why some of the WIndows 10 systems here are identified (e.g. by the free Fing App or Windows part) Apple MacOS systems.

And yes, it's always interesting looking under the hood of consumer devices....

Message 12 of 13
Highlighted
Apprentice

Re: lack of DHCP-linked DNS view


@schumaku wrote:

 


@gb777 wrote:

So Netgear doesn't implement a DHCP-linked DNS view, ...  Ironically, this includes whether the DHCP client used option 12.

Interesting priorities.


Have looked into the R9000 here again - no Armor so luckily none of the above. However of course typical behaviour:

 

  • Appears dnsmasq (v2.80 as I nagged - and of course that's carried ahead to other newer products - there are known vulnerabilities on 2.78 and 2.79 ... so why bother, Netgear?) is built here _with_ DHCP support, but there is no DHCP config.
  • Instead, the Busybox (one of my favourites due to the very incomplete shell functionality) integrated udhcpd (and udhcpc) seems to be in place now.
  • Checking the config does show:
    ---
    root@R9000-1:/# cat /tmp/udhcpd.conf
    pidfile /var/run/udhcpd.pid
    start 192.168.10.1
    end 192.168.10.253
    interface br0
    remaining yes
    auto_time 5
    lease_file /tmp/udhcpd.leases
    ---
    While the /tmp/udhcpd.leases file does exist, it's never touched or updated - obviously a bug. OK, I'm testing with Android 10 and 11 systems not providing a host name.
    ---
    root@R9000-1:/# ls -als /tmp/udhcpd.leases
    0 -rw-r--r-- 1 root root 0 Jan 1 1970 /tmp/udhcpd.leases
    ---

This would make updating the local DNS somewhat difficult. Same on your Orbi @gb777 ?

 

No, my udhcpd.leases has stuff in it, e.g.

 

00000540 52 42 53 37 35 30 00 00 00 00 00 00 00 00 00 00 |RBS750..........|
00000550 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|


@Christian_R please share these issues and bugs with the consumer business unit...


@gb777 wrote:

Interesting priorities.  I haven't even checked what privacy policies I must have agreed to when buying this device that allows them to scan and fingerprint my network (including MAC addresses, OS versions, Hardware guesses, etc.) and collect this information.


Security software under the Armor label does certainly sell better than a DHCP-DNS integration - especially as it is bundling the BitDefender for Android, iOS (somewhat basic), Windows, and MacOS for the customer's client devices.

 

I wonder if BitDefender flags the RBR devices itself.

BTW, this edit widget is completely screwed up, at least for me. I can't unquote parts of the message, so my responses above are at the wrong indentation level. Oh well.

Message 13 of 13