[Dnsmasq-discuss] Compile-time options - taming the combinatorial explosion.

[Kevin Darbyshire-Bryant]

> On 25 Oct 2018, at 20:33, Shankar Unni <shankar.unni at gmail.com> wrote:
> 
> On Oct 24, 2018, at 2:49 PM, Simon Kelley <simon at thekelleys.org.uk> wrote:
> 
>> […]
>> The next option in my sights is NO_FORK. This produces a
>> mostly-functional binary that never forks any new processes. It was
>> added long ago to support uclinux, the MMU-less version of Linux. As far
>> as I can tell, MMU-less linux is a dead project, and I'm minded to
>> remove NO_FORK. Opinions? Is this option vital to something I'm not
>> aware of?
> 
> From what i can see, this will kill off the ‘k’ option that’s used by many process-management environments.  E.g. openwrt’s process management (the procd daemon) depends on the originally-launched process to stick around (it doesn’t know or care about the PID file), and does really ugly things if the PID changes after launch.  It also doesn’t seem to have an option to pass in an explicit PID file to read and poll.  (I just verified by removing the -k option, and it keeps spawning more and more dnsmasqs..)
> 
> If you do want to do this, it’ll probably need a few months of warning and preparation for various distros..

A quick glance at the code suggests you’ve misunderstood.  The compile time option ’NO_FORK’ is designed for systems that don’t have a fork system call….which is unusual to say the least.  A fair amount of code is *added* if NO_FORK is NOT defined… or to put in clearer English, the code to support ‘fork’ is added in unless NO_FORK is defined.

The run-time option OPT_NO_FORK aka ‘-k’ is to prevent dnsmasq forking and as you say is used by some process management daemons to determine if a process under its control has died or not.  My reading of the code suggests that removing ’NO_FORK’ build option does NOT remove ‘-k’ OPT_NO_FORK run-time option.

I think Openwrt is safe.   There will be a loud scream from me if it isn’t :-)

Cheers,

Kevin D-B

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