Re: [lwip-users] dhcp_fine_tmr

[Leon Woestenberg]

Hello Tom,

Tom C. Barker wrote:
> Leon,
>  
> Forgive me if this is a little naive, but if I have an interface
> which has its IP address from DHCP, why do I need to
> constantly run dhcp_fine_tmr? I know I need to run the
> coarse timer, but could that also be backed off after I
> have secured a lease for say, 3 days?
>  
Good point, and you are right. Backing off timers, or setting their 
time-out, is not supported in lwIP to keep it simple, so I kept my DHCP 
client in line with that. Some explanation on the timers:

The fine timer is used for DHCP transaction messages
time-outs. The course timer is used for lease time-outs.

The fine timer only needs to run when there are open transactions
pending (expecting a response from a DHCP server).

The course timer only needs to run when there is at least one
non-infinite lease.

If you can optimize your performance by conditional calls to the
timers, please do so.

However, note that for a single interface, the actions taken in
fine_tmr() are minimal, and are not much heavier than the condition that 
decides whether the timer should be called at all.

Regards,

Leon.

p.s. The same probably goes for TCP.