Re: Question about AETH_NAK_PSN_SEQ_ERROR

[Chengguang Xu <cgxu519@mykernel.net>]

在 2022/5/14 21:35, Chengguang Xu 写道:
> Hello Folks,
>
>
> There is a logic(below code) in check_ack() in rxe_comp.c,  the case 
> (AETH_NAK_PSN_SEQ_ERROR)
> indicates sending side received a nak ack which means opposite side 
> had an psn seq error(expected psn < received psn).
> I don't fully understand the comment(/* a nak implicitly acks all 
> packets with psns before */) here,
> could someone give me a hint for this?

Carefully checking rxe_resp.c and found the psn in the ack (with 
AETH_NAK_PSN_SEQ_ERROR) is resp.psn not received pkt->psn.  :-)



>
> Also, set qp->comp.psn as pkt->psn will skip some psns(from 
> qp->comp.psn to pkt->psn) in the retry, is it correct?
>
> Many thanks in advance!
> Chengguang
>
> -------------------------
>
>   case AETH_NAK:
>             switch (syn) {
>             case AETH_NAK_PSN_SEQ_ERROR:
>                 /* a nak implicitly acks all packets with psns
>                  * before
>                  */
>                 if (psn_compare(pkt->psn, qp->comp.psn) > 0) {
>                     rxe_counter_inc(rxe,
>                             RXE_CNT_RCV_SEQ_ERR);
>                     qp->comp.psn = pkt->psn;
>                     if (qp->req.wait_psn) {
>                         qp->req.wait_psn = 0;
>                         rxe_run_task(&qp->req.task, 0);
>                     }
>                 }
>                 return COMPST_ERROR_RETRY;
>
>
>