Re: Flushing the DNS cache?
Eirik Byrkjeflot Anonsen <[email protected]>
| Newsgroups | gmane.comp.web.opera.linux |
|---|---|
| Message-ID | <[email protected]> |
Daniel Pittman <[email protected]> writes: > Eirik Byrkjeflot Anonsen <[email protected]> writes: >> Kenneth Crudup <[email protected]> writes: > > [...] > >>> I dunno if it's 'cause of the way y'all are using libresolv (or similar), >>> but it's appearing to take on the first DNS I use. Try it and see. >> >> I guess it is possible that the system resolver (which would be libc >> on linux, I think) caches the dns server address. But even in that >> case, I would assume that it only caches it per application. >> >> I'd be very disappointed in the desktop team if they aren't leaving >> the whole job of dns resolution to the system resolver. We do cache >> the addresses the dns server returns, but we should never have a >> reason to know what the address of the dns server itself is. > > Well, if you cache the result yourself, and the team responsible for > that code have done a decent job, they *can't* use the libc resolver. > > The default code doesn't return the TTL of results, just the result, so > to be able to implement a correct DNS cache you must talk DNS > directly... You're right. Though I'd argue that it is better that we overshoot extremely short DNS TTL values than that we fail to use the system resolver. Particularly if our DNS cache is using reasonably small TTL values anyway (like 5 or 10 minutes), the cases where it would cause problems would be extremely limited. Though it also depends on the reason for caching. If we are caching only for performance gains, using a 1-minute timeout would probably be fine (and should cause minimal problems for anyone). If we are caching for security reasons (as Herman suggested), then it may actually be correct to use a longer TTL than what the dns server suggests. (Technically, I think that's called "pinning" rather than "caching"). The problems of not using the system resolver are much more serious (consistent failures to look up host names in some setups). eirik -- Opera-Linux: https://list.opera.com/mailman/listinfo/opera-linux More lists: https://list.opera.com/mailman/listinfo/ Unsubscribe: mailto:[email protected]?subject=unsubscribe