[Dnsmasq-discuss] Specifying boot options for specific type of
hardware.
Josef Wolf
jw at
Thu Aug 25 23:12:22 BST 2005
On Mon, Aug 22, 2005 at 12:27:33PM +0100, Simon Kelley wrote:
> It's correct that dnsmasq provides both BOOTP and DHCP. I guess I never
> thought about why BOOTP can't do dynamic addresses before - no BOOTP
> server I know about does. How about this: BOOTP has no notion of lease
> times and lease renewal or expiry, so any address allocated by BOOTP
> would have to have an infinite lease and be lost for ever from the pool
> of allocatable addresses.
Yeah. That's essentially what rfc1534 describes:
In summary, a DHCP server:
o MAY support BOOTP clients,
o May return automatic addresses to BOOTP clients,
o MUST provide a configuration switch if returning automatic
addresses to BOOTP clients,
o MUST default this optional configuration to OFF,
o MUST abide by the BOOTP specification when interacting with
BOOTP clients, and
o MAY send DHCP options (those options defined in the DHCP options
document but not in the BOOTP vendor extensions documents) to
a BOOTP client.
> There's therefore a big danger that you would
> eventually run out of dynamically allocatable addresses.
In the general, you're right. But the boxes I try to get onto the net
use BOOTP _only_ to load their OS. After the OS (linux) is loaded, the
normal boot procedure starts and the box configures itself via DHCP.
I guess this is pretty non-standard and every piece of hardware that
acts like this is somewhat braindead. But I have no chance to change
the hardware.
I think in this special case, handing out and reserving a lease for a
couple of minutes for this MAC would not generate any problems. The
box will request a lease (and will be offered the reserved lease) about
5 seconds after it had got the BOOTP-reply.
OTOH, this is what actually happens:
Given following config:
dhcp-range=192.168.1.155,192.168.1.190,15m
dhcp-host=00:43:12:*:*:*,net:foobox,192.168.1.15
dhcp-boot=net:foobox,/tftpboot/bootfile,bootserver,192.168.1.1
1. The box sends a BOOTP request.
2. dnsmasq answers with 192.168.1.15
3. Box boots and requsts dhcp lease.
4. dnsmasq offers 192.168.1.15(!) as lease.
Note that this address is _not_ withhin dhcp-range.
5. Box accepts lease.
[ ... ]
n. Box reboots
n+1. The box sends a BOOTP request.
n+2. dnsmasq complains "address already in use".
n+3. Box hangs. (BOOTP-reply is missing)
--
No software patents in Europe -- http://nosoftwarepatents.com
-- Josef Wolf -- jw at raven.inka.de --
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