[radvd-devel-l] FlushDNSSL option

Mark Smith radvd at 02a76c927861ca7413a122f2a73a0d37.nosense.org
Fri Mar 25 08:11:05 EDT 2011

Hi Pekka,

On Fri, 25 Mar 2011 13:30:44 +0200 (EET)
Pekka Savola <pekkas at netcore.fi> wrote:

> On Fri, 25 Mar 2011, Mark Smith wrote:
> > After this, there should now be -
> >
> > DeprecatePrefix (default: off)
> > RemoveRoute (default: on)
> > FlushRDNSS (default: on)
> > FlushDNSSL (default: on)
> For consistency, RemoteRoute should probably also be FlushRoute?

I think RemoveRoute is better. "Remove" is the word that the
RFC uses to describe the action performed on the route table when a
route option is received with a zero lifetime. It's also been my
experience that it's a word commonly used by networking people when a
specific and individual route is removed from a route table e.g. you
don't flush a route from a route table, you remove it.

> DeprecatePrefix could also possibly be FlushPrefix, but given that it 
> has different defaults and semantics, the current name is probably 
> more informative.

"Deprecated" is the word used in RFC4862 to describe a prefix that has
had it's preferred life set to zero. I think calling the option
anything else would confuse people as to what action this option was
performing. The prefix is still active on the interface, as it is not
possible to set the valid lifetime to anything less than or equal to 2
hours, unless SEND is being used, so the deprecated prefix and
associated addresses have to age for a while before they'll disappear.
If the option was called "FlushPrefix", then I'd think people would
expect that the addresses on the interface would immediately disappear.
"(D|d)eprecated" is also the word you'll see under at least both
Windows 7 and Linux for when an address has a zero preferred but >1
second valid lifetime.

I'm ok with Flush for the RDNSS and DNSSL options because there isn't
any common operation use or RFC specific terminology used for what
happens when DNS addresses or search list entries are removed. However,
if consistency is an overriding goal, then I'd prefer to make them
RemoveRDNSS (as my original patch did) and RemoveDNSSL.


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