[Dnsmasq-discuss] Environment variable DNSMASQ_CLIENT_ID

[Geert Stappers]

On Sun, Dec 05, 2021 at 09:21:17AM +0100, Community Member wrote:
> Follow up from "RaspberryPi PCAP file" thread.
> 
> On Sat, Dec 4, 2021 at 1:42 PM Geert Stappers wrote:
> > On Sat, Dec 04, 2021 at 12:11:13PM -0800, Carl Karsten wrote:
> > > On Sat, Dec 4, 2021 at 10:12 AM Geert Stappers wrote:
> > > >
> > > > My observation on the PCAP file
> > > > * there are several stages
> > > > * each stage starts with a (partial) DHCP session
> > > >
> > > >
> > > > The first stage:
> > > > * DHCP Discover with option 97, Client Identifier,
> > > >   f6 27 6d 7a f6 27 6d 7a f6 27 6d 7a f6 27 6d 7a
> > > >   from client
> > > > * DHCP Offer with filename 'ipxe/undionly.kpxe'
> > > >   from server
>   .....
> > > > The second stage:
> > > > * DHCP Discover with option 97, Client Identifier,
> > > >   f6 27 6d 7a f6 27 6d 7a f6 27 6d 7a f6 27 6d 7a
> > > >   from client  (yes, that is the same identifier)
> > > > * DHCP Offer with filename 'ipxe/undionly.kpxe'
> > > >   from server (yes, that is the same filename)
>   .....
> > >
> > > My pi netboot needs are basically satisfied,
> >
> > OK
> >
> > And what about the dnsmasq needs that did get us here???
> >
> 
> Hmm.. I'm not out of the weeds just yet.
> 
> > > > The first stage:
> > > > * DHCP Discover with option 97, Client Identifier,
> > > >   f6 27 6d 7a f6 27 6d 7a f6 27 6d 7a f6 27 6d 7a
> 
> I need access to that value.  That's the serial number  f6 27 6d 7a
> repeated 4 times.
> but not
> DNSMASQ_CLIENT_ID=01:b8:27:eb:6d:27:f6

That is the MAC-address prefixed with "01:",
not the expected DHCP option 97, Client Identifier.
 
> Here is a quick test I did:
> dhcp-script=/root/dnsmasq-test1.sh
> 
> $ cat /root/dnsmasq-test1.sh
> #!/bin/bash -x
> echo $* >> /tmp/dnsmasq-test1.txt
> /usr/bin/env  >> /tmp/dnsmasq-test1.txt
> 
> $ /tmp/dnsmasq-test1.txt
> old b8:27:eb:6d:27:f6 10.21.0.162 raspberrypi

Yes as dnsmasq manual page says
  The  arguments to the process are "add", "old" or "del", the MAC address
  of the host (or DUID for IPv6) , the  IP address, and the hostname,
  if known.

> DNSMASQ_TAGS=eth-local
> DNSMASQ_INTERFACE=eth-local
> DNSMASQ_VENDOR_CLASS=dhcpcd-8.1.2:Linux-5.10.63-v8+:aarch64:BCM2835
> LANGUAGE=en_US:en
> DNSMASQ_TIME_REMAINING=21600
> DNSMASQ_CLIENT_ID=01:b8:27:eb:6d:27:f6
> PIDFILE=/run/dnsmasq/dnsmasq.pid
> DNSMASQ_LEASE_EXPIRES=1638680174
> PWD=/
> LANG=en_US.UTF-8
> INVOCATION_ID=3bcf8de10dbb44e6b6d844ab5fa06d17
> DNSMASQ_REQUESTED_OPTIONS=1,121,33,3,6,12,15,26,28,51,54,58,59,119
> SHLVL=1
> DNSMASQ_DOMAIN=video.debconf.org
> JOURNAL_STREAM=8:28400
> PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
> DNSMASQ_SUPPLIED_HOSTNAME=raspberrypi
> _=/usr/bin/env
> 
> 
> -- 
> Community M


Groeten
Geert Stappers
-- 
Silence is hard to parse