netdev - Re: [bpf-next, v2] samples: bpf: add max_pckt_size option at xdp_adjust

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Date:   Fri, 30 Aug 2019 03:23:34 +0900
From:   "Daniel T. Lee" <danieltimlee@...il.com>
To:     Song Liu <liu.song.a23@...il.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [bpf-next, v2] samples: bpf: add max_pckt_size option at xdp_adjust_tail

On Fri, Aug 30, 2019 at 5:42 AM Song Liu <liu.song.a23@...il.com> wrote:
>
> On Mon, Aug 26, 2019 at 9:52 AM Daniel T. Lee <danieltimlee@...il.com> wrote:
> >
> > Currently, at xdp_adjust_tail_kern.c, MAX_PCKT_SIZE is limited
> > to 600. To make this size flexible, a new map 'pcktsz' is added.
> >
> > By updating new packet size to this map from the userland,
> > xdp_adjust_tail_kern.o will use this value as a new max_pckt_size.
> >
> > If no '-P <MAX_PCKT_SIZE>' option is used, the size of maximum packet
> > will be 600 as a default.
>
> Please also cc bpf@...r.kernel.org for bpf patches.
>

I'll make sure to have it included next time.

> >
> > Signed-off-by: Daniel T. Lee <danieltimlee@...il.com>
>
> Acked-by: Song Liu <songliubraving@...com>
>
> With a nit below.
>
> [...]
>
> > diff --git a/samples/bpf/xdp_adjust_tail_user.c b/samples/bpf/xdp_adjust_tail_user.c
> > index a3596b617c4c..29ade7caf841 100644
> > --- a/samples/bpf/xdp_adjust_tail_user.c
> > +++ b/samples/bpf/xdp_adjust_tail_user.c
> > @@ -72,6 +72,7 @@ static void usage(const char *cmd)
> >         printf("Usage: %s [...]\n", cmd);
> >         printf("    -i <ifname|ifindex> Interface\n");
> >         printf("    -T <stop-after-X-seconds> Default: 0 (forever)\n");
> > +       printf("    -P <MAX_PCKT_SIZE> Default: 600\n");
>
> nit: printf("    -P <MAX_PCKT_SIZE> Default: %u\n", MAX_PCKT_SIZE);

With all due respect, I'm afraid that MAX_PCKT_SIZE constant is only
defined at '_kern.c'.
Are you saying that it should be defined at '_user.c' either?

Thanks for the review!