Date: Sat, 4 Oct 2025 18:24:14 +0200 From: Roman Bogorodskiy <bogorodskiy@gmail.com> To: Kyle Evans <kevans@freebsd.org> Cc: freebsd-net@freebsd.org Subject: Re: ifconfig(8) on trying to destroy tap(4) interface used by a process Message-ID: <aOFKLpYGkbBkFJLU@tulp> In-Reply-To: <87a30461-e2ee-4251-bad7-5bb900e85164@FreeBSD.org> References: <aOEZXmEwJYEDar3u@tulp> <87a30461-e2ee-4251-bad7-5bb900e85164@FreeBSD.org>
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Kyle Evans wrote: > > ifconfig keeps hanging like that and exits only when the process that > > owns the tap(4) interface releases it. > > > > I don't seem to find anything about that in manual pages for both > > tap(4) and ifconfig(8) (probably missed something), but generally, I'd > > expect ifconfig to immediately exit with an error and non-zero exit > > code. > > > > I agree that it should be documented, but historically tun/tap have hung on > destroy if the cdev was still opened by a process. I made it interruptible[0] > somewhat recently, and also added a mode where tun/tap can be configured as > transient[1] so that they just naturally get destroyed on last close. Neither > of those have made it back to stable/14, but I don't think there's a reason > off-hand that they couldn't go back. Thanks for clarification. Both changes look nice to have in stable/14, especially [1], which should make device management/cleanup code a little simpler. > > Additionally, while trying to reproduce and document that, I've got a > > panic: > > > > FreeBSD tulp 16.0-CURRENT FreeBSD 16.0-CURRENT #6 main-n280778-f45608124286: Tue Sep 30 22:25:58 CEST 2025 root@tulp:/usr/obj/usr/src/amd64.amd64/sys/GENERIC amd64 > > > > panic: deadlres_td_sleep_q: possible deadlock detected for 0xfffff80022425780 (ifconfig), blocked for 1802579 ticks > > > > I was able to reproduce this ifconfig(8) behavior on 14.3-RELEASE-p1 > > too. > > > > Is it expected? > > > > I think so, yeah. > > > Thanks, > > Roman > > > > [0] https://cgit.freebsd.org/src/commit/sys/net/if_tuntap.c?id=274bf7c8ae7e7b51853cd541481985f0e687f10e > [1] https://cgit.freebsd.org/src/commit/sys/net/if_tuntap.c?id=a1174b3b1174754b1f69406bff4456d002e8f583 >
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