[Dnsmasq-discuss] Option 120 (RFC 3361)

[Simon Kelley]

Brian Candler wrote:
> Hi,
> 
> I'm using dnsmasq as supplied with OpenWrt WhiteRussian RC6:
> 
> root at OpenWrt:~# dnsmasq -v
> Dnsmasq version 2.33  Copyright (C) 2000-2006 Simon Kelley
> Compile time options IPv6 GNU-getopt ISC-leasefile no-DBus no-I18N
> 
> I'm trying to get it to generate an RFC 3361 "SIP server" option, code 120,
> but I can't make it work. A tcpdump -X on the client shows that this option
> isn't being included.
> 
> I've added the following to the end of /etc/dnsmasq.conf :
> 
> # SIP server (RFC 3361)
> dhcp-option=120,1,192.168.1.1
> 
> and I don't get the option. But strangely, changing this to 
> 
> dhcp-option=42,192.168.1.1
> 
> *does* add an NTP server option into the response.
> 
> I also tried adding -O 120,1,192.168.1.1 to the command line, to no effect.
> 
> The test client is a Linux laptop running dhclient from CentOS 4.4.
> 
> Any suggestions as to what I'm doing wrong?
> 

Grr, another overly-complex and unique DHCP option format. The best you
can do for now is specify exactly what you want, byte-by-byte, in hex.

Assuming your "dhcp-option=120,1,192.168.1.1" is what you want, rather
than just an example, this would be

dhcp-option=120,01:01:01:a8:c0

I'll add explict support for this option format to the next release.

Cheers,

Simon.