[Dnsmasq-discuss] [PATCH] allow multiple Classless Route Options

Simon Kelley simon at thekelleys.org.uk
Fri Jul 20 17:42:49 BST 2018


On 20/07/18 08:55, Roy Marples wrote:
> On 19/07/2018 21:34, Simon Kelley wrote:
>> This generates multiple instance of the DHCP option 121 in the DHCP
>> reply packet, which isn't strictly legal.
> 
> What makes you think it's not legal?
> RFC3442 makes no mention of it not being legal and RFC3396 describes how
> multiple instances of options should be concatenated when an options
> data exceeds 255 bytes.
> 
> dhcpcd of course supports this :)
> 
> Roy
> 

You're right, of course :)

However dnsmasq tries not to need this function, on the "be liberal in
what you accept and conservative is what you send" principle.

Perhaps I should have said that dnsmasq doesn't use multiple dhcp-option
lines to construct what it sends for a particular option number. Given
that these things can be tagged, and the semantics for which ones a
valid can get quite complicated,  a simplifying rule is that at most one
dhcp-option line is used. That's what the code the OP was patching
actually does, and the patch disabled is as special case for option 121.

The philosophy is that if you need to send multiple values in an option,
then dnsmasq allows you to specify those multiple values in a single
dhcp-option line.



Cheers,

Simon.




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