[Dnsmasq-discuss] RFC: allowing arbitrarily long options

[Neil Jerram]

On Sun, Jan 14, 2018 at 10:35 PM Simon Kelley <simon at thekelleys.org.uk>
wrote:

> On 14/01/18 18:14, Neil Jerram wrote:
> > Thanks for looking at this, Simon.  Some thoughts below...
> >
> > On Sat, Jan 13, 2018 at 5:34 PM Simon Kelley <simon at thekelleys.org.uk
> > <mailto:simon at thekelleys.org.uk>> wrote:
> >
> >     I'm in favour, in theory at least, of removing arbitrary limits.
> >     Experience has shown that no matter how big, someone, somewhere, will
> >     always find them. The code originally used a fixed buffer which
> happened
> >     to be unused at that point, to reduce the memory footprint. Whilst
> >     dnsmasq is still intended to be "small", small is a relative thing,
> and
> >     absolutely, rather bigger than it was 15 years ago, so allocating a
> big
> >     enough buffer is fine.
> >
> >     In this case, though, as you hint, it's likely that shell limits will
> >     also be a problem. Even eliminating that by using configuration
> files,
> >     you still have very long lines, which is ugly.
> >
> >     Can't we solve this problem by allowing repeated interface names, so
> >
> >     --bridge-interface=eth1,alias-1,alias-2
> >
> >     becomes identical to
> >
> >     --bridge-interface=eth1,alias-1
> >     --bridge-interface=eth1,alias-2
> >
> >     the patch to implement that is probably smaller than your offering.
> >
> >
> > It looks like a nice alternative, but note that it doesn't help at all
> > with any shell limit.  (In fact it would hit any such limit sooner.)  So
> > I think this is a matter of what you think is more elegant for dnsmasq
> > itself; particularly in the configuration file context where shell
> > limits don't apply.
> >
> >
> >
> >
> >     Maybe we should do both?
> >
> >
> > In principle I'm happy to code up and test multiple solutions here; it's
> > not a large amount of work in any case.  So please do let me know what
> > you would prefer.
>
> I'll take both, for preference.
>
> Actually - no. You test the long-options patch and I'll take that. I'll
> do the split-into-multiple lines one.
>

I have (or in fact my colleague has) successfully tested this now (with a
real OpenStack rig, 90 cirros VMs at the same time on a GCE n1-standard-64
compute node), with no further changes to the patch that I attached before.

So I believe the patch is good - please would you consider it for merging?

Many thanks - Neil


>
> Cheers,
>
> Simon.
>
> >
> > Best wishes - Neil
> >
> >
> >
> >
> >     On 07/01/18 14:25, Neil Jerram wrote:
> >     > Calico [1] with OpenStack
> >     > (https://docs.projectcalico.org/v2.6/getting-started/openstack/)
> uses
> >     > dnsmasq with a very long --bridge-interface option:
> >     >
> >     >
> >
>  --bridge-interface=<context-if-name>,<alias-if-name>,<alias-if-name>,...,
> >     >
> >     > where each occurrence of ",<alias-if-name>" occupies 15
> >     characters, and
> >     > there can in principle be as many <alias-if-name>s as you can have
> VMs
> >     > on a single OpenStack compute host.  Currently an option arg is
> >     limited
> >     > in dnsmasq to 1025 chars overall, which only allows for 67
> >     > <alias-if-name>s, which is not necessarily enough, on a powerful
> >     compute
> >     > host.
> >     >
> >     > So I wonder what folk would think about reallocating as necessary
> to
> >     > allow an option arg to be arbitrarily long?  (Or at least, as long
> as
> >     > getopt and the containing shell will allow.)  For reference I've
> >     > attached a patch that I think would implement that - but I haven't
> yet
> >     > been able to test it at all, so please don't merge it yet!
> >     >
> >     > Thanks in advance for your thoughts!
> >     >       Neil
> >     >
> >     >
> >     >
> >     > _______________________________________________
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> >     >
> >
> >
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> >
>
>
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