On Thu, Nov 02, 2017 at 10:26:55PM +0100, Reyk Floeter wrote:
> Hi,
>
> the problem got reported a few times and a similar diff was floating
> around: vmd's "local interface" implements a simple auto-magic BOOTP
> server, but udhcpc doesn't support BOOTP, which is the predecessor and
> a valid subset of DHCP. udhcpc is used by busybox and many embedded
> Linux distributions, maybe even by Android.
>
> The following diff adds minimal DHCP support which works with udhcpc.
>
Thanks Carlos and Mike, I just committed the change.
Here is a practical example of the actual difference:
1. Before the change in simple stateless BOOTP mode:
```
# dhclient vio0
DHCPDISCOVER on vio0 - interval 1
BOOTREPLY from 100.64.1.2 (fe:e1:bb:d1:a9:65)
bound to 100.64.1.3 -- renewal in 8000 seconds.
# cat /var/db/dhclient.leases.vio0
lease {
bootp;
interface "vio0";
fixed-address 100.64.1.3;
next-server 100.64.1.2;
option subnet-mask 255.255.255.254;
option routers 100.64.1.2;
option domain-name-servers 100.64.1.2;
option dhcp-lease-time 12000;
option dhcp-renewal-time 8000;
option dhcp-rebinding-time 10000;
renew 0 2017/11/05 22:03:14 UTC;
rebind 0 2017/11/05 22:36:34 UTC;
expire 0 2017/11/05 23:09:54 UTC;
}
```
2. After the change in minimal DHCP mode:
```
# dhclient vio0
DHCPDISCOVER on vio0 - interval 1
DHCPOFFER from 100.64.1.2 (fe:e1:bb:d1:09:1f)
DHCPREQUEST on vio0 to 255.255.255.255
DHCPACK from 100.64.1.2 (fe:e1:bb:d1:09:1f)
bound to 100.64.1.3 -- renewal in 2147483647 seconds.
# cat /var/db/dhclient.leases.vio0
lease {
interface "vio0";
fixed-address 100.64.1.3;
next-server 100.64.1.2;
option subnet-mask 255.255.255.254;
option routers 100.64.1.2;
option domain-name-servers 100.64.1.2,100.64.1.2;
option dhcp-lease-time 4294967295;
option dhcp-message-type 5;
option dhcp-server-identifier 100.64.1.2;
renew 5 2085/11/23 23:02:27 UTC;
rebind 6 2136/12/08 07:28:03 UTC;
expire 4 2153/12/13 02:16:35 UTC;
}
```
As the lease never changes, I'm setting the lease time to 0xffffffff,
as RFC 2132 section 9.2 defines it as "The time is in units of
seconds, and is specified as a 32-bit unsigned integer". This doesn't
seem to cause any problems on dhclient or udhpc but it would be
interesting to find out if there is any other DHCP implementation that
handles it as "int" ...
Reyk
