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From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: "Hu, Jiayu" <jiayu.hu@intel.com>, yang_y_yi <yang_y_yi@163.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	"olivier.matz@6wind.com" <olivier.matz@6wind.com>,
	"thomas@monjalon.net" <thomas@monjalon.net>,
	"yangyi01@inspur.com" <yangyi01@inspur.com>
Subject: Re: [dpdk-dev] [PATCH] gso: fix free issue of mbuf gso segments attach to
Date: Thu, 15 Oct 2020 16:16:03 +0000
Message-ID: <BYAPR11MB330178813E4F9DC71E5507EA9A020@BYAPR11MB3301.namprd11.prod.outlook.com> (raw)
In-Reply-To: <cf33f4b88dcf44cf890fb8e6163ddb36@intel.com>



> 
> > -----Original Message-----
> > From: Ananyev, Konstantin <konstantin.ananyev@intel.com>
> > Sent: Wednesday, October 14, 2020 8:06 PM
> > To: yang_y_yi <yang_y_yi@163.com>; Hu, Jiayu <jiayu.hu@intel.com>
> > Cc: dev@dpdk.org; olivier.matz@6wind.com; thomas@monjalon.net;
> > yangyi01@inspur.com
> > Subject: RE: Re:RE: [PATCH] gso: fix free issue of mbuf gso segments attach to
> >
> >
> > > From: yang_y_yi <yang_y_yi@163.com>
> > > Sent: Wednesday, October 14, 2020 3:56 AM
> > > To: Hu, Jiayu <jiayu.hu@intel.com>
> > > Cc: Ananyev, Konstantin <konstantin.ananyev@intel.com>; dev@dpdk.org;
> > olivier.matz@6wind.com; thomas@monjalon.net;
> > > yangyi01@inspur.com
> > > Subject: Re:RE: [PATCH] gso: fix free issue of mbuf gso segments attach to
> > >
> > > I think it isn't a good idea to free it in rte_gso_segment, maybe application
> > will continue to use this pkt for other purpose, rte_gso_segment
> > > can't make decision for application without any notice, it is better to return
> > this decision right backt to application.
> > >
> >
> > I think, if user wants to keep original packet, he can always call
> > rte_pktmbuf_refcnt_update(pkt, 1)
> > just before calling gso function.
> >
> > Also, as I remember in some cases it is not safe to do free() for input packet
> > (as pkt_out[] can contain input pkt itself). Would it also be user responsibility
> > to determine
> > such situations?
> 
> In what case will pkt_out[] contain the input pkt? Can you give an example?

As I can read the code, whenever gso code decides that
no segmentation is not really needed, or it is not capable
of doing it properly.
Let say:

gso_tcp4_segment(struct rte_mbuf *pkt,
                uint16_t gso_size,
                uint8_t ipid_delta,
                struct rte_mempool *direct_pool,
                struct rte_mempool *indirect_pool,
                struct rte_mbuf **pkts_out,
                uint16_t nb_pkts_out)
{
	...
	/* Don't process the fragmented packet */
        ipv4_hdr = (struct rte_ipv4_hdr *)(rte_pktmbuf_mtod(pkt, char *) +
                        pkt->l2_len);
        frag_off = rte_be_to_cpu_16(ipv4_hdr->fragment_offset);
        if (unlikely(IS_FRAGMENTED(frag_off))) {
                pkts_out[0] = pkt;
                return 1;
        }

        /* Don't process the packet without data */
        hdr_offset = pkt->l2_len + pkt->l3_len + pkt->l4_len;
        if (unlikely(hdr_offset >= pkt->pkt_len)) {
                pkts_out[0] = pkt;
                return 1;
        }

That's why in rte_gso_segment() we update refcnt only when ret > 1. 
	



  reply	other threads:[~2020-10-15 16:16 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-10  3:10 yang_y_yi
2020-10-13  7:28 ` Hu, Jiayu
2020-10-13 15:39   ` Ananyev, Konstantin
2020-10-14  1:00     ` Hu, Jiayu
2020-10-14  2:56       ` yang_y_yi
2020-10-14 12:05         ` Ananyev, Konstantin
2020-10-15  5:14           ` Hu, Jiayu
2020-10-15 16:16             ` Ananyev, Konstantin [this message]
2020-10-16  0:53               ` Hu, Jiayu
2020-10-16  8:31                 ` Ananyev, Konstantin
2020-10-19  3:17                   ` Hu, Jiayu
2020-10-19  6:44                     ` yang_y_yi
2020-10-19  8:47                       ` Ananyev, Konstantin
2020-10-20  1:16                         ` yang_y_yi
2020-10-19  2:29                 ` yang_y_yi
2020-10-19  2:20               ` yang_y_yi

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