> -----Original Message-----
> From: Ananyev, Konstantin <konstantin.anan...@intel.com>
> Sent: Friday, October 16, 2020 12:16 AM
> To: Hu, Jiayu <jiayu...@intel.com>; yang_y_yi <yang_y...@163.com>
> Cc: dev@dpdk.org; olivier.m...@6wind.com; tho...@monjalon.net;
> yangy...@inspur.com
> Subject: RE: Re:RE: [PATCH] gso: fix free issue of mbuf gso segments attach to
>
>
>
> >
> > > -----Original Message-----
> > > From: Ananyev, Konstantin <konstantin.anan...@intel.com>
> > > Sent: Wednesday, October 14, 2020 8:06 PM
> > > To: yang_y_yi <yang_y...@163.com>; Hu, Jiayu <jiayu...@intel.com>
> > > Cc: dev@dpdk.org; olivier.m...@6wind.com; tho...@monjalon.net;
> > > yangy...@inspur.com
> > > Subject: RE: Re:RE: [PATCH] gso: fix free issue of mbuf gso segments
> attach to
> > >
> > >
> > > > From: yang_y_yi <yang_y...@163.com>
> > > > Sent: Wednesday, October 14, 2020 3:56 AM
> > > > To: Hu, Jiayu <jiayu...@intel.com>
> > > > Cc: Ananyev, Konstantin <konstantin.anan...@intel.com>;
> dev@dpdk.org;
> > > olivier.m...@6wind.com; tho...@monjalon.net;
> > > > yangy...@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.
But in these cases, the value of ret is 1. So we can free input pkt only when
ret > 1. Like:
- if (ret > 1) {
- pkt_seg = pkt;
- while (pkt_seg) {
- rte_mbuf_refcnt_update(pkt_seg, -1);
- pkt_seg = pkt_seg->next;
- }
- } else if (ret < 0) {
+ if (ret > 1)
+ rte_pktmbuf_free(pkt);
+ else if (ret < 0) {
/* Revert the ol_flags in the event of failure. */
pkt->ol_flags = ol_flags;
}
Thanks,
Jiayu
>
>
>
