dhcpd sporadically ignoring one of two "copies" of a DHCP request

[Phil Mayers]

On 11/03/14 16:43, Phil Mayers wrote:

> What's really odd is that further investigation suggests there is some
> link to the "seconds" field in the bootp header; if secs==0, the 2nd
> DISCOVER is ignored. If secs!=0, it's answered.
>

Actually that might be a red herring; closer investigation suggests that 
it's actually timing/path-dependent:

  * if a server hasn't allocated a lease to the client
  * and it receives two DISCOVER packets in quick succession
  * it will only answer one

...but:

  * if a server has previously allocated lease to the client
  * and it receives two DISCOVER packets in quick succession
  * it will answer both

This suggests there is some locking during the initial lease allocation, 
and that packets received during that period from the same client are 
discarded?