From: Stephen Hemminger <stephen@networkplumber.org>
To: Bruce Richardson <bruce.richardson@intel.com>
Cc: Ferruh Yigit <ferruh.yigit@intel.com>,
dev@dpdk.org, Chas Williams <chas3@att.com>,
"John W. Linville" <linville@tuxdriver.com>
Subject: Re: [dpdk-dev] [PATCH v2] net/af_packet: fix vlan_insert corruption
Date: Tue, 16 Apr 2019 08:03:36 -0700 [thread overview]
Message-ID: <20190416080336.3b8e16a6@xps13.lan> (raw)
Message-ID: <20190416150336.ngqrI2htPiT6fscmYHKXgl4X2LEhQxJQ6RP1wq-xP5A@z> (raw)
In-Reply-To: <20190416094212.GA1865@bricha3-MOBL.ger.corp.intel.com>
On Tue, 16 Apr 2019 10:42:13 +0100
Bruce Richardson <bruce.richardson@intel.com> wrote:
> On Tue, Apr 16, 2019 at 10:37:07AM +0100, Ferruh Yigit wrote:
> > On 4/12/2019 11:08 PM, Stephen Hemminger wrote:
> > > On Fri, 12 Apr 2019 17:28:17 +0100
> > > Ferruh Yigit <ferruh.yigit@intel.com> wrote:
> > >
> > >> On 4/8/2019 5:41 PM, Stephen Hemminger wrote:
> > >>> If the af_packet transmit is sending a VLAN packet,
> > >>> and the transmit path to the kernel os full, then it would
> > >>> mismanage the outgoing mbuf. The original mbuf would end up
> > >>> being freed twice, once by AF_PACKET PMD and once by caller.
> > >>
> > >> This comment is valid with your new patch [1] that updates 'rte_vlan_insert()'
> > >> to duplicate the mbuf, right?
> > >>
> > >> That patch looks like won't make the release, so I suggest this one wait that
> > >> patch, although this is harmless on its own, commit log is misleading.
> > >>
> > >> [1]
> > >> https://patches.dpdk.org/patch/51870/
> > >
> > > It was always true, even with existing vlan_insert.
> > > Existing vlan_insert has issues if it ever creates a clone packet.
> > > Existing vlan_insert can duplicate mbuf through clone
> > >
> >
> > Right, existing vlan_insert has same issue on af_packet.
> >
> > But, should vlan_insert try to duplicate the mbuf when it is shared, does it
> > worth the complexity it brings? And when that support removed this patch won't
> > be needed.
>
> I don't think vlan insert or other mbuf manipulation APIs should be
> checking for shared state or not - that's the job of the app. We could have
> cases where the user does want to modify a shared mbuf.
>
> Regards,
> /Bruce
The vlan_insert code is called on transmit, and there are lots of
cases where a transmit mbuf might be shared (like TCP stack). And in that
case inserting the vlan must be non-destructive to the original mbuf.
Whether you want to push the problem to the driver or do it in the
library, it is still a problem.
next prev parent reply other threads:[~2019-04-16 15:03 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-08 16:04 [dpdk-dev] [PATCH] " Stephen Hemminger
2019-04-08 16:04 ` Stephen Hemminger
2019-04-08 16:41 ` [dpdk-dev] [PATCH v2] " Stephen Hemminger
2019-04-08 16:41 ` Stephen Hemminger
2019-04-12 16:28 ` Ferruh Yigit
2019-04-12 16:28 ` Ferruh Yigit
2019-04-12 22:08 ` Stephen Hemminger
2019-04-12 22:08 ` Stephen Hemminger
2019-04-16 9:37 ` Ferruh Yigit
2019-04-16 9:37 ` Ferruh Yigit
2019-04-16 9:42 ` Bruce Richardson
2019-04-16 9:42 ` Bruce Richardson
2019-04-16 15:03 ` Stephen Hemminger [this message]
2019-04-16 15:03 ` Stephen Hemminger
2019-04-16 15:13 ` Bruce Richardson
2019-04-16 15:13 ` Bruce Richardson
2019-07-04 18:43 ` Ferruh Yigit
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