Date: Sat, 17 Dec 2022 09:13:14 -0800 From: Gleb Smirnoff <glebius@freebsd.org> To: Zhenlei Huang <zlei.huang@gmail.com> Cc: "Bjoern A. Zeeb" <bz@freebsd.org>, "freebsd-jail@freebsd.org" <freebsd-jail@freebsd.org> Subject: Re: What's going on with vnets and epairs w/ addresses? Message-ID: <Y534qgEG1nX5i1iB@FreeBSD.org> In-Reply-To: <150A60D6-6757-46DD-988F-05A9FFA36821@FreeBSD.org> References: <5r22os7n-ro15-27q-r356-rps331o06so5@mnoonqbm.arg> <B6C70A88-11F8-40D7-85E4-63BBA0F7931D@FreeBSD.org> <150A60D6-6757-46DD-988F-05A9FFA36821@FreeBSD.org>
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Zhenlei, On Fri, Dec 16, 2022 at 06:30:57PM +0800, Zhenlei Huang wrote: Z> I managed to repeat this issue on CURRENT/14 with this small snip: Z> Z> ------------------------------------------- Z> #!/bin/sh Z> Z> # test jail name Z> n="test_ref_leak" Z> Z> jail -c name=$n path=/ vnet persist Z> # The following line trigger jail pr_ref leak Z> jexec $n ifconfig lo0 inet 127.0.0.1/8 Z> Z> jail -R $n Z> Z> # wait a moment Z> sleep 1 Z> Z> jls -j $n Z> Z> After DDB debugging and tracing , it seems that is triggered by a combine of [1] and [2] Z> Z> [1] https://reviews.freebsd.org/rGfec8a8c7cbe4384c7e61d376f3aa5be5ac895915 <https://reviews.freebsd.org/rGfec8a8c7cbe4384c7e61d376f3aa5be5ac895915>; Z> [2] https://reviews.freebsd.org/rGeb93b99d698674e3b1cc7139fda98e2b175b8c5b <https://reviews.freebsd.org/rGeb93b99d698674e3b1cc7139fda98e2b175b8c5b>; Z> Z> Z> In [1] the per-VNET uma zone is shared with the global one. Z> `pcbinfo->ipi_zone = pcbstor->ips_zone;` Z> Z> In [2] unref `inp->inp_cred` is deferred called in inpcb_dtor() by uma_zfree_smr() . Z> Z> Unfortunately inps freed by uma_zfree_smr() are cached and inpcb_dtor() is not called immediately , Z> thus leaking `inp->inp_cred` ref and hence `prison->pr_ref`. Z> Z> And it is also not possible to free up the cache by per-VNET SYSUNINIT tcp_destroy / udp_destroy / rip_destroy. This is known issue and I'd prefer not to call it a problem. The "leak" of a jail happens only if machine is idle wrt the networking activity. Getting back to the problem that started this thread - the epair(4)s not immediately popping back to prison0. IMHO, the problem again lies in the design of if_vmove and epair(4) in particular. The if_vmove shall not exist, instead we should do a full if_attach() and if_detach(). The state of an ifnet when it undergoes if_vmove doesn't carry any useful information. With Alexander melifaro@ we discussed better options for creating or attaching interfaces to jails that if_vmove. Until they are ready the most easy workaround to deal with annoying epair(4) come back problem is to remove it manually before destroying a jail, like I did in 80fc25025ff. -- Gleb Smirnoff
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