> From: "Ben Pfaff" <[email protected]> > To: "Lance Richardson" <[email protected]> > Cc: [email protected] > Sent: Tuesday, August 8, 2017 3:48:15 PM > Subject: Re: [ovs-dev] DNS support options > > On Tue, Aug 08, 2017 at 02:59:21PM -0400, Lance Richardson wrote: > > > From: "Ben Pfaff" <[email protected]> > > > To: [email protected] > > > Sent: Tuesday, August 8, 2017 2:43:17 PM > > > Subject: [ovs-dev] DNS support options > > > > > > Open vSwitch currently supports only IP addresses for specifying > > > OpenFlow and OVSDB remotes. It would be nice to support DNS names. > > > Open vSwitch can't afford to let DNS resolution block processing, so it > > > needs some way to resolve DNS asynchronously. I've come up with the > > > following solutions so far: > > > > > > * Implement it ourselves using threads. Probably, this would be > > > a single worker thread that loops through calls to > > > getaddrinfo(). > > > > > > * glibc has getaddrinfo_a(), an asynchronous version of > > > getaddrinfo(). *BSD and Windows do not have this function, so > > > we would still need to implement it ourselves (probably using > > > threads) if we adopted this approach, so it might be more work > > > than the first solution. > > > > > > * Use an external asynchronous DNS library. GNU adns looks like > > > a good choice: http://www.chiark.greenend.org.uk/~ian/adns/. > > > It has a port to Windows but I don't know whether it's > > > up-to-date. > > > > > > > With adns_beforepoll()/adns_afterpoll(), it looks like adns might be easy > > to integrate on top of lib/poll-loop.c. Not requiring a separate thread > > seems like a plus. > > Oops, I just realized that adns is GPL'd, which means that linking it > against OVS would force OVS to be GPL'd, so it's probably not a good > choice. > > Other possible choices: > > - c-ares (https://c-ares.haxx.se/). Main disadvantage seems to > be that it's very "select" oriented. >
c-ares has an API to retrieve the set of socket descriptors that need to be monitored for readability/writability, so integration shouldn't be much work. A socket creation callback function can be registered as well, not sure if it would be needed but it's nice that it's there. Looks like a fairly active project with some contributors I recognize. > - UDNS (http://www.corpit.ru/mjt/udns.html). May not be well > maintained--last release in 2014. Does not fall back to TCP > if necessary. Port to Windows exists, don't know whether it's > up-to-date. > _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
