[Dnsmasq-discuss] custom TFTP port

Geert Stappers stappers at stappers.nl
Thu Dec 9 20:56:08 UTC 2021


On Thu, Dec 09, 2021 at 07:42:30PM +0000, Konstantin Orekhov via Dnsmasq-discuss wrote:
> Hello there!

Welcome,


> Just like described
> in https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2019q4/013650.html,
> I also have a use case in Kubernetes where all containers are running
> as non-root only thus making it impossible for me to start dnsmasq as
> I get permission error:
> dnsmasq: failed to create listening socket for port 69: Permission denied

And what about DNS, port 53,  and DHCP, port 67?


 
> I just love single-port option in dnsmasq for TFTP

Text from https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2019q4/013659.html

|This is standard mode:
|IP 172.17.0.2.42447 > 172.17.0.1.69:  22 RRQ "/some_file" netascii
|IP 172.17.0.1.56457 > 172.17.0.2.42447: UDP, length 15
|IP 172.17.0.2.42447 > 172.17.0.1.56457: UDP, length 4
| 
|This is single port mode:
|IP 172.17.0.2.56296 > 172.17.0.1.69:  22 RRQ "/some_file" netascii
|IP 172.17.0.1.69 > 172.17.0.2.56296:  15 DATA block 1
|IP 172.17.0.2.56296 > 172.17.0.1.69:  4 ACK block 1

More text from that thread:
( https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2019q4/013660.html )
|The TID in the tftp packets is supposed to match the port it's sending
|on.  This is how well-behaving tftp software can verify it's receiving
|the correct packets.  The single-port stuff breaks down when, e.g.,
|you're booting 1500 computers from a given tftpd.
|
|It's always easier to write new code than to learn the existing tools.
|It's just not a sustainable practice, especially when you're violating
|standards in the process.

> and was wondering if custom port for it would be something that is
> possible to add to a list of command line args/config.
> If there's some other way to accomplish the same, please let me know
> as I was not able to find it.


Groeten
Geert Stappers
-- 
Silence is hard to parse



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