DHCP client always using broadcast as the destination - sdust

Reception, channel detection, network issues, CableCARD setup, etc.
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sdust
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DHCP client always using broadcast as the destination - sdust

Post by sdust »

Looking at network activity of CONNECT 4K it seems the DHCP client does not remember the DHCP server address and always sends DHCP messages to the broadcast address.

Code: Select all

10:18:56.625714 00:18:dd:XX:XX:XX > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 342: (tos 0x0, ttl 64, id 27893, offset 0, flags [DF], proto UDP (17), length 328)
    192.168.0.234.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 00:18:dd:XX:XX:XX, length 300, xid 0x7a2e7c08, Flags [Broadcast]




HDHomeRun CONNECT 4K
Model: HDHR5-4K
Firmware: 20210224

jasonl
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Re: DHCP client always using broadcast as the destination

Post by jasonl »

Per RFC 2131, the client has the option of using either broadcast or unicast for the DHCPREQUEST.

sdust
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Re: DHCP client always using broadcast as the destination

Post by sdust »

jasonl wrote: Mon Jun 07, 2021 8:34 pm Per RFC 2131, the client has the option of using either broadcast or unicast for the DHCPREQUEST.
And HomeRun is the only device flooding the network with the unnecessary broadcast. :D

nickk
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Re: DHCP client always using broadcast as the destination

Post by nickk »

sdust wrote: Mon Jun 07, 2021 10:51 pm
jasonl wrote: Mon Jun 07, 2021 8:34 pm Per RFC 2131, the client has the option of using either broadcast or unicast for the DHCPREQUEST.
And HomeRun is the only device flooding the network with the unnecessary broadcast. :D
2 packets every 12 hours (assuming a 24 hour lease).

sdust
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Re: DHCP client always using broadcast as the destination

Post by sdust »

nickk wrote: Mon Jun 07, 2021 11:42 pm
sdust wrote: Mon Jun 07, 2021 10:51 pm
jasonl wrote: Mon Jun 07, 2021 8:34 pm Per RFC 2131, the client has the option of using either broadcast or unicast for the DHCPREQUEST.
And HomeRun is the only device flooding the network with the unnecessary broadcast. :D
2 packets every 12 hours (assuming a 24 hour lease).
The lease time on my network is 10 minutes in line with AWS. I also think if something is worth doing it is worth doing right. I will refrain from enumerating the many areas where the quality of Silicon Dust engineering does not shine and results in unnecessary suffering of its users. ;)

Edit: A well behaved DHCP client when the IP address of the DHCP server is already known uses unicast. It doesn't also set the broadcast flag on the request which makes the server sending the reply use broadcast as well. This makes watching traffic from/to the device unnecessary difficult.

NedS
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Re: DHCP client always using broadcast as the destination

Post by NedS »

I also think if something is worth doing it is worth doing right.
That statement is in direct contrition to this statement:
The lease time on my network is 10 minutes
A ten minute lease time is absurd for a home network. You are creating your own problem and asking us to fix it.

sdust
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Re: DHCP client always using broadcast as the destination

Post by sdust »

NedS wrote: Tue Jun 08, 2021 1:50 am
I also think if something is worth doing it is worth doing right.
That statement is in direct contrition to this statement:
The lease time on my network is 10 minutes
A ten minute lease time is absurd for a home network. You are creating your own problem and asking us to fix it.
Let's say I have quite a few devices on my network but I would not call the setup absurd. That's uncalled for. ;)

nickk
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Re: DHCP client always using broadcast as the destination

Post by nickk »

A 10 minute lease time is fine. I did the initial development-test with a 60s lease time.

I wrote that code about 10 years ago so a quick revisit is reasonable - I will take a look.

Nick

mski
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Re: DHCP client always using broadcast as the destination

Post by mski »

nickk wrote: Tue Jun 08, 2021 9:48 am > I wrote that code about 10 years ago so a quick revisit is reasonable - I will take a look.
Hi, Nick! I’m just swinging by to say thank you. It’s great to see your team consider enhancements that incorporate best practices (even when the customer TV experience isn’t directly impacted). These updates add up over time to a higher quality total ownership experience. Your team is positioned to get lots of unsolicited and misinformed advise and product development requests. Weeding through those and making progress is impressive!

nickk
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Re: DHCP client always using broadcast as the destination - sdust

Post by nickk »

We have reviewed and tweaked the DHCP handling...

Broadcast is used in the case of:
* DISCOVER or REQUEST due to link-up (no IP address).
* DISCOVER or REQUEST due to rebind.

Unicast is used in the case of:
* REQUEST due to renew.

mski
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Re: DHCP client always using broadcast as the destination - sdust

Post by mski »

Thank you.

sdust
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Re: DHCP client always using broadcast as the destination - sdust

Post by sdust »

Thank you! Going into the next release?

nickk
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Re: DHCP client always using broadcast as the destination - sdust

Post by nickk »

sdust wrote: Mon Jun 28, 2021 11:59 am Thank you! Going into the next release?
Yes, the change will be in the next release.

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