On Fri, Oct 4, 2019 at 3:48 PM Kyle Evans <kev...@freebsd.org> wrote: > > On Fri, Oct 4, 2019 at 2:12 PM John Baldwin <j...@freebsd.org> wrote: > > > > On 10/4/19 6:43 AM, Kyle Evans wrote: > > > Author: kevans > > > Date: Fri Oct 4 13:43:07 2019 > > > New Revision: 353103 > > > URL: https://svnweb.freebsd.org/changeset/base/353103 > > > > > > Log: > > > tuntap(4): loosen up tunclose restrictions > > > > > > Realistically, this cannot work. We don't allow the tun to be opened > > > twice, > > > so it must be done via fd passing, fork, dup, some mechanism like these. > > > Applications demonstrably do not enforce strict ordering when they're > > > handing off tun devices, so the parent closing before the child will > > > easily > > > leave the tun/tap device in a bad state where it can't be destroyed and > > > a > > > confused user because they did nothing wrong. > > > > > > Concede that we can't leave the tun/tap device in this kind of state > > > because > > > of software not playing the TUNSIFPID game, but it is still good to > > > find and > > > fix this kind of thing to keep ifconfig(8) up-to-date and help ensure > > > good > > > discipline in tun handling. > > > > Why are you using d_close for last close anyway? It's not really reliable > > compared > > to using cdevpriv and a cdevpriv dtor. > > > > This decision predates me by a long time, I'm afraid. =-) > > If you have time to elaborate on the comparable reliability point, I'd > be interested in hearing it. A little bit of searching didn't seem to > turn up much there, I'm afraid. > > I did otherwise spend a little bit of time diving into the path taken > to get to d_close and the trade-offs between cdevpriv vs. what tuntap > does now. I think I'm convinced either way that cdevpriv is a good way > to go- it seems to have the advantage that with a little refactoring > we could actually set the softc atomically on the device cdevpriv > instead of cdev->si_drv1 and I can axe this rwatson@ comment about the > non-atomic test and set. > > I don't see any downside here.
Well, maybe not on that middle paragraph, but I still see no downsides. =-) _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
