At 2020-10-16 00:16:03, "Ananyev, Konstantin" <[email protected]>
wrote:
>
>
>>
>> > -----Original Message-----
>> > From: Ananyev, Konstantin <[email protected]>
>> > Sent: Wednesday, October 14, 2020 8:06 PM
>> > To: yang_y_yi <[email protected]>; Hu, Jiayu <[email protected]>
>> > Cc: [email protected]; [email protected]; [email protected];
>> > [email protected]
>> > Subject: RE: Re:RE: [PATCH] gso: fix free issue of mbuf gso segments
>> > attach to
>> >
>> >
>> > > From: yang_y_yi <[email protected]>
>> > > Sent: Wednesday, October 14, 2020 3:56 AM
>> > > To: Hu, Jiayu <[email protected]>
>> > > Cc: Ananyev, Konstantin <[email protected]>; [email protected];
>> > [email protected]; [email protected];
>> > > [email protected]
>> > > 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.
>
>
This code block
if (ret > 1) {
pkt_seg = pkt;
while (pkt_seg) {
rte_mbuf_refcnt_update(pkt_seg, -1);
pkt_seg = pkt_seg->next;
}
}
should be equivalent to this
if (ret > 1) {
rte_pktmbuf_free(pkt);
}
So not sure what the issue you're saying is.
