dhcpcd-discuss

Hi Roy,


On 14 March 2019 00:34:56 Roy Marples <roy@xxxxxxxxxxxx> wrote:

> Hi Roger
>
> On 13/03/2019 17:24, Roger James wrote:
> > Running dhcpcd version 1:6.11.5-1+rpt7 on debian. I see the DUID-LLT
> > generated by dhcpcd and stored dhcpcd.duid is being updated with a new
> > timestamp every time it is sent out for example in a solicit. Surely
> > this is contrary to RFC6355.
> >
> >
> >
> >
> > "DUIDs are intended to remain constant over time, so that they can be
> >  used as permanent identifiers for a device. In the case of DUID-
> >  LLTs, they are intended to be generated once, stored in stable
> >  storage, and reused from that point forward."
> >
> >
> >
> >
> > Is this intentional?
>
> Certainly not from dhcpcd.
> It's not intentional if the case.

Just to clarify, it is just the DUID that is sent out that is changed not 
the one in the file.

> > Also if the dhcp.duid file is hand edited and a DUID-UUID is inserted,
> > then then the UUID part of the DUID is truncated to 8 bytes when it is
> > used.
> >
> >
> >
> >
> > This makes it difficult to use dhcpcd to assign static dhcpv6 leases.
>
> Maybe this is the cause of the former?
> Would you mind sharing a duid file which exhibits this?

This is the duid that gets truncated.

00:02:b5:a9:cd:0e:6d:7a:4d:45:92:e0:49:43:a8:73:4b:95

This is the file I am currently running with.

00:02:b5:a9:cd:0e:6d:7a:4d:45

I did this just to remind me what was actually being sent. This is a not a 
valid type 2 DUID (DUID-UUID). The UUID is defined as a 128 bit field. 
However, my router (openwrt) doesn't seem to bother and quite happily uses 
this along with the iaid to assign a static lease.

The following is a duid as generated by dhcpcd.

00:01:00:01:21:44:28:4a:b8:27:eb:71:99:03

This is the one that gets its time stamp component changed. This seems to 
relate to reboots or restarts of dhcpd. When this happens the lease does 
not match the one I have stored in the router's static ipv6 address table.

I will set up a test system to do any further investigations. The system I 
observed this onev is my pbx. Somewhat critical!


Roger