omshell reservation

[glenn.satchell at uniq.com.au]

Hi Greg,

Oh, sorry didn't pick that up. In the dhcpd.leases(5) man page it 
suggests that it should write the keyword 'reserved;' into the lease 
entry. Note this is the only place in that man page that has the word 
"flags".

        bootp;
        reserved;

        If  present, they indicate that the BOOTP and RESERVED failover 
flags (respectively) should be set.  BOOTP and RESERVED dynamic leases 
are treated differently than normal dynamic leases, as they may
        only be used by the client to which they are currently allocated.

So maybe setting flags = 0 is not the right thing. Perhaps some other 
value or some other name?

Quite likely you may need to look at the source code to get further into 
it. I started here:

https://gitlab.isc.org/isc-projects/dhcp/-/blob/master/dhcpctl/omshell.c

but there are a few levels of indirection to work through and it's a few 
years since I've done much C :)

https://gitlab.isc.org/isc-projects/dhcp/-/blob/master/includes/dhcpd.h

in includes/dhcpd.h in the definition of struct lease near line 590 it 
has:

struct lease {
...
         u_int8_t flags;
...
#       define RESERVED_LEASE           4
#       define MS_NULL_TERMINATION      8

so maybe 4 is the value to set the flags to in OMSHELL? Looking at 
server/omapi.c around line 312 the new value is OR'd in with the 
existing flags.

So I tested this, the only bit different to your recipe was set flags = 
4

omshell
key name value (these are from /etc/dhcpd.conf)
connect
new lease
set ip-address = 192.168.14.219
open
set flags = 4
update

and after giving the update command this is the new lease entry with the 
reserved flag:

lease 192.168.14.219 {
   starts 4 2018/12/20 07:31:58;
   ends 4 2018/12/20 07:33:58;
   tstp 4 2018/12/20 07:33:58;
   cltt 4 2018/12/20 07:31:58;
   binding state free;
   reserved;
   hardware ethernet e0:66:78:50:f0:e8;
   uid "\000glenn at drill.com";
   set remote-handle = %2;
   set param-req-list = "1,121,3,6,15,119,252";
   client-hostname "Ashleighs-iPad";
}

ta da!

regard,
Glenn Satchell

On 2020-07-20 23:18, Gregory Sloop wrote:
> Still struggling with this.
> 
> Perhaps I wasn't clear, but question #3 was about what I see in the
> leases file.
> 
> After the lease is expired, here's what I find in the leases file.
> ---
> lease 10.8.20.229 {
>   starts 5 2020/07/17 22:42:54;
>   ends 5 2020/07/17 22:42:52;
>   tstp 5 2020/07/17 22:42:54;
>   tsfp 5 2020/07/17 22:42:54;
>   atsfp 5 2020/07/17 22:42:54;
>   cltt 5 2020/07/17 18:42:52;
>   binding state backup;
>   hardware ethernet 98:01:a7:ff:ff:ff;
>   uid "\000\000\000\000\000\000";
>   set remote-handle = %3;
>   set vendor-class-identifier = "MSFT 5.0";
> }
> 
> ---
> 
> The only thing that I noticed that changed after setting flags was the
>   set remote-handle = %3;
> And I can't find any detail about what "remote-handle" is.
> Does it even apply to reservations?
> 
> TIA
> -Greg
> 
> gsuca> Great sleuthing there Greg. omshell typically writes something
> into the
> gsuca> leases file, so have a look for the *last* record for the given
> IP
> gsuca> address and see what is in it, especially compared to earlier
> ones.
> 
> gsuca> regards,
> gsuca> -glenn
> 
> gsuca> On 2020-07-18 08:02, Gregory Sloop wrote:
>>> I'm trying to accomplish a "reservation" using omshell.
> 
>>> But just like Unicorns, Santa, and the Easter Bunny, I'm not sure
> it
>>> really exists!
>>> Ok, ok. Yeah, it probably does - but I can't find an example
> anywhere
>>> that's confirmed to work.
> 
>>> This quote from long ago summarizes my feelings so far. [probably
>>> nearly everyone's, actually]
> 
>>>> involves a rather fragile and often misbehaving omshell
>>>> process where the only "documentation" is half a mailing list
> thread
>>>> from ten years ago
> 
>>> So, from what I've gleaned, this is what I'm doing.
>>> After you get into omshell
>>> ---
>>> port xxx
>>> server localhost
>>> key...
>>> set ip-sddress=1.2.3.4
>>> open
>>> ---
> 
>>> I get a listing of the lease for 1.2.3.4
>>> Then it looks like I should use
>>> set flag = 8
>>> update
>>> [And surprisingly the update takes. It feels like magic when you
>>> finally hit on the right incantation!]
> 
>>> So, my questions
>>> 1) Is setting flags = 8 the right thing to set for a reserved
> lease?
>>> (I'm guessing from that even less than half a thread from 10y ago.)
> 
>>> 2) How can I tell if it actually took?
> 
>>> 3) And perhaps realated to #2 - what's this mean in the lease: set
>>> remote-handle = %3; (I see that after setting flag = 8
> 
>>> TIA
>>> -Greg
>>> _______________________________________________
>>> ISC funds the development of this software with paid support
>>> subscriptions. Contact us at https://www.isc.org/contact/ for more
>>> information.