Correct use of DHCP option 97

[Arzhel Younsi]

Hi,

We're currently using DHCP option 82 (circuit id) to identify servers
during their initial bootstrapping with the following ISC-DHCP 4.4.1
configuration:
host sretest1004 {
    host-identifier option agent.circuit-id
"lsw1-e8-eqiad:Ethernet0.0:private1-e8-eqiad";
    fixed-address 10.64.158.2;
    option pxelinux.pathprefix "
http://apt.wikimedia.org/tftpboot/bullseye-installer/";
}

This is working fine but option 82 has been more and more problematic to
use, so I've been looking at using option 97 instead as the server's serial
# is embedded in the UUID/GUID sent by PXE.
You can see below the output of dhcpdump. Note that the server's PXE
doesn't send option 61 (client-identifier).

log(binary-to-ascii(16, 8, ":", option pxe-client-id)); does return
0:44:45:4c:4c:5a:0:10:59:80:5a:c4:c0:4f:51:50:32
Which fits what's in Wireshark: https://phabricator.wikimedia.org/F41504283

But I tried all the combinations I could think of to match on it, with
no success.

For example:
host-identifier option pxe-client-id 0
00:44:45:4c:4c:5a:00:10:59:80:5a:c4:c0:4f:51:50:32;
host-identifier option pxe-client-id 0
44:45:4c:4c:5a:00:10:59:80:5a:c4:c0:4f:51:50:32;  (in case the initial 00:
was the type).
With quotes, with an additional 01: or ff: prefix, without the
"host-identifier" statement. With "dhcp-client-identifier" instead, just in
case.
Similarly with the GUID:
host-identifier option pxe-client-id 0
"4c4c4544-005a-5910-805a-c4c04f515032";
host-identifier option pxe-client-id 0
4c:4c:45:44:00:5a:59:10:80:5a:c4:c0:4f:51:50:32;
etc, still no success.

Does anyone have any pointers on how to get it to match on the option 97
value ?

Thanks

  TIME: 2023-11-14 13:50:44.837
    IP: 10.64.146.14 (5c:5e:ab:3d:87:c3) > 208.80.154.74 (aa:0:0:22:9f:cc)
    OP: 1 (BOOTPREQUEST)
 HTYPE: 1 (Ethernet)
  HLEN: 6
  HOPS: 1
   XID: 2d295df0
  SECS: 64
 FLAGS: 7f80
CIADDR: 0.0.0.0
YIADDR: 0.0.0.0
SIADDR: 0.0.0.0
GIADDR: 10.64.158.1
CHADDR: b0:26:28:29:5d:f0:00:00:00:00:00:00:00:00:00:00
 SNAME: .
 FNAME: .
OPTION:  53 (  1) DHCP message type         1 (DHCPDISCOVER)
OPTION:  55 ( 24) Parameter Request List      1 (Subnet mask)
					      2 (Time offset)
					      3 (Routers)
					      5 (Name server)
					      6 (DNS server)
					     11 (Resource location server)
					     12 (Host name)
					     13 (Boot file size)
					     15 (Domainname)
					     16 (Swap server)
					     17 (Root path)
					     18 (Extensions path)
					     43 (Vendor specific info)
					     54 (Server identifier)
					     60 (Vendor class identifier)
					     67 (Bootfile name)
					    128 (???)
					    129 (???)
					    130 (???)
					    131 (???)
					    132 (???)
					    133 (???)
					    134 (???)
					    135 (???)
					
OPTION:  57 (  2) Maximum DHCP message size 1260
OPTION:  97 ( 17) UUID/GUID                 0044454c4c5a0010 .DELLZ..
					    59805ac4c04f5150 Y.Z..OQP
					    32               2
OPTION:  93 (  2) Client System             0000             ..
OPTION:  94 (  3) Client NDI                010201           ...
OPTION:  60 ( 32) Vendor class identifier   PXEClient:Arch:00000:UNDI:002001
OPTION:  82 ( 30) Relay Agent Information
                  Circuit-ID    45:74:68:65:72:6e:65:74:30
                  Remote-ID
63:34:3a:35:61:3a:62:31:3a:31:61:3a:36:33:3a:30:37


-- 
Arzhel
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