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Message-ID: <20140601143639.GE507@brightrain.aerifal.cx> Date: Sun, 1 Jun 2014 10:36:39 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: Requirements for new dns backend, factoring considerations On Sun, Jun 01, 2014 at 10:01:51AM +0200, u-igbb@...ey.se wrote: > > As another alternative, we could drop the goal of doing search > > suffixes in parallel. This would have no bearing on lookups of fully > > qualified names using the default settings (ndots:1) since the > > presence of a dot suppresses search. Where it would negatively impact > > performance, though, is for users who want to have several search > > domains (think: home network, university network, department-specific > > university network, etc.) for quick shortcuts to machines on multiple > > different networks. > > My experience is that such kind of shortcuts is dangerous and inconsistent. > They stir different namespaces, this can not give a reliable outcome > in a general case. I tend to agree with this a lot. As long as you leave ndots=1, your shortcuts have no dots in them, and you only have one search domain, I think the results can be fairly reliable/consistent. But in general you're right. I'm not sure if other implementations fall back to searching when this_query.dots>=ndots and looking up this_query as a fqdn failed, but doing so sounds like bad and dangerous behavior and I'd strongly prefer not to do it. > What a certain shortcut resolves to depends on too many things and among > others on which changes are made by third parties to the contents of > the name spaces which you short-circuit (a new host in one's department > can easily take the place of a desired host at a different department). Yes, I think this feature is harmful whenever third-party changes can affect _which_ result you see and not just whether you see a result or not. Note that any use of ndots>1 leads to such issues (e.g. do you get google.com or google.com.example.com?). > > Another option still is leaving search domains unimplemented (musl has > > not supported them up til now, and there hasn't been much request for > > As I see this, spending your time on other things might be a better choice. If we don't want to accelerate it with parallel lookups, leaving it for later, and only if there's demand, is a perfectly viable strategy. It's only a consideration now if parallelism is considered important. Rich
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