On 4/16/2019 4:13 PM, Bruce Richardson wrote: > On Tue, Apr 16, 2019 at 08:03:36AM -0700, Stephen Hemminger wrote: >> On Tue, 16 Apr 2019 10:42:13 +0100 >> Bruce Richardson <bruce.richard...@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.yi...@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. > > Yes, I agree it's a problem. I'd prefer see it done in the driver than in the > library, since it's higher in the SW stack and has more context information > as to what is safe or not.
The patch not more needed with current rte_vlan_insert()
