netdev - Re: [PATCH bpf 1/3] selftests/xsk: print correct payload for packet dump

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Date:   Tue, 15 Nov 2022 13:40:48 +0100
From:   Magnus Karlsson <magnus.karlsson@...il.com>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc:     magnus.karlsson@...el.com, bjorn@...nel.org, ast@...nel.org,
        daniel@...earbox.net, netdev@...r.kernel.org,
        jonathan.lemon@...il.com, bpf@...r.kernel.org
Subject: Re: [PATCH bpf 1/3] selftests/xsk: print correct payload for packet dump

On Tue, Nov 15, 2022 at 1:29 PM Maciej Fijalkowski
<maciej.fijalkowski@...el.com> wrote:
>
> On Tue, Nov 15, 2022 at 09:05:36AM +0100, Magnus Karlsson wrote:
> > From: Magnus Karlsson <magnus.karlsson@...el.com>
> >
> > Print the correct payload when the packet dump option is selected. The
> > network to host conversion was forgotten and the payload was
> > erronously declared to be an int instead of an unsigned int. Changed
> > the loop index i too, as it does not need to be an int and was
> > declared on the same row.
> >
> > The printout looks something like this after the fix:
> >
> > DEBUG>> L2: dst mac: 000A569EEE62
> > DEBUG>> L2: src mac: 000A569EEE61
> > DEBUG>> L3: ip_hdr->ihl: 05
> > DEBUG>> L3: ip_hdr->saddr: 192.168.100.161
> > DEBUG>> L3: ip_hdr->daddr: 192.168.100.162
> > DEBUG>> L4: udp_hdr->src: 2121
> > DEBUG>> L4: udp_hdr->dst: 2020
> > DEBUG>> L5: payload: 4
> > ---------------------------------------
>
> Above would be helpful if previous output was included as well but not a
> big deal i guess.

It would not bring any value IMHO. The only difference is that the
"L5: payload" row is now showing the correct payload.

> >
> > Fixes: facb7cb2e909 ("selftests/bpf: Xsk selftests - SKB POLL, NOPOLL")
> > Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
> > ---
> >  tools/testing/selftests/bpf/xskxceiver.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/testing/selftests/bpf/xskxceiver.c b/tools/testing/selftests/bpf/xskxceiver.c
> > index 681a5db80dae..51e693318b3f 100644
> > --- a/tools/testing/selftests/bpf/xskxceiver.c
> > +++ b/tools/testing/selftests/bpf/xskxceiver.c
> > @@ -767,7 +767,7 @@ static void pkt_dump(void *pkt, u32 len)
> >       struct ethhdr *ethhdr;
> >       struct udphdr *udphdr;
> >       struct iphdr *iphdr;
> > -     int payload, i;
> > +     u32 payload, i;
> >
> >       ethhdr = pkt;
> >       iphdr = pkt + sizeof(*ethhdr);
> > @@ -792,7 +792,7 @@ static void pkt_dump(void *pkt, u32 len)
> >       fprintf(stdout, "DEBUG>> L4: udp_hdr->src: %d\n", ntohs(udphdr->source));
> >       fprintf(stdout, "DEBUG>> L4: udp_hdr->dst: %d\n", ntohs(udphdr->dest));
> >       /*extract L5 frame */
> > -     payload = *((uint32_t *)(pkt + PKT_HDR_SIZE));
> > +     payload = ntohl(*((u32 *)(pkt + PKT_HDR_SIZE)));
> >
> >       fprintf(stdout, "DEBUG>> L5: payload: %d\n", payload);
> >       fprintf(stdout, "---------------------------------------\n");
> > --
> > 2.34.1
> >