netdev - Re: [PATCH bpf-next v11 12/12] selftests/bpf: add simple bpf tests in the tx path for timestamping feature

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Message-ID: <CAL+tcoDJ9EA0BDOE-6Qti3MkAa=u-yAtR-2zjbBrAAjBHXnuDg@mail.gmail.com>
Date: Sat, 15 Feb 2025 07:18:53 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, dsahern@...nel.org, willemdebruijn.kernel@...il.com, 
	willemb@...gle.com, ast@...nel.org, daniel@...earbox.net, andrii@...nel.org, 
	eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev, 
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me, 
	haoluo@...gle.com, jolsa@...nel.org, horms@...nel.org, bpf@...r.kernel.org, 
	netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next v11 12/12] selftests/bpf: add simple bpf tests in
 the tx path for timestamping feature

On Sat, Feb 15, 2025 at 4:40 AM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> On 2/13/25 5:00 PM, Jason Xing wrote:
> > +static void test_recv_errmsg_cmsg(struct msghdr *msg)
> > +{
> > +     struct sock_extended_err *serr = NULL;
> > +     struct scm_timestamping *tss = NULL;
> > +     struct cmsghdr *cm;
> > +
> > +     for (cm = CMSG_FIRSTHDR(msg);
> > +          cm && cm->cmsg_len;
> > +          cm = CMSG_NXTHDR(msg, cm)) {
> > +             if (cm->cmsg_level == SOL_SOCKET &&
> > +                 cm->cmsg_type == SCM_TIMESTAMPING) {
> > +                     tss = (void *)CMSG_DATA(cm);
> > +             } else if ((cm->cmsg_level == SOL_IP &&
> > +                         cm->cmsg_type == IP_RECVERR) ||
> > +                        (cm->cmsg_level == SOL_IPV6 &&
> > +                         cm->cmsg_type == IPV6_RECVERR) ||
> > +                        (cm->cmsg_level == SOL_PACKET &&
> > +                         cm->cmsg_type == PACKET_TX_TIMESTAMP)) {
> > +                     serr = (void *)CMSG_DATA(cm);
> > +                     ASSERT_EQ(serr->ee_origin, SO_EE_ORIGIN_TIMESTAMPING,
> > +                               "cmsg type");
> > +             }
> > +
> > +             if (serr && tss)
>
> Regarding this check, does it need to reset both serr and tss to NULL before the
> next iteration? e.g. It can get >1 timestamps in one recvmsg(MSG_ERRQUEUE) ?

If more than one skb carrying timestamping is received in one recvmsg
from the error queue in this case, it means something goes wrong. So
we don't expect that to happen.

Thanks,
Jason

>
> > +                     test_socket_timestamp(tss, serr->ee_info,
> > +                                           serr->ee_data);
> > +     }
> > +}
> > +
>