netdev - Re: [PATCH iproute2 -next v2 4/5] {f,m}_bpf: allow updates on program arrays

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Date:	Thu, 26 Nov 2015 16:19:29 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Daniel Borkmann <daniel@...earbox.net>, stephen@...workplumber.org
Cc:	ast@...nel.org, netdev@...r.kernel.org
Subject: Re: [PATCH iproute2 -next v2 4/5] {f,m}_bpf: allow updates on program
 arrays

On Thu, Nov 26, 2015, at 15:38, Daniel Borkmann wrote:
> +static int bpf_mnt_fs(const char *target)
> +{
> +       bool bind_done = false;
> +
> +       while (mount("", target, "none", MS_PRIVATE | MS_REC, NULL)) {
> +               if (errno != EINVAL || bind_done) {
> +                       fprintf(stderr, "mount --make-private %s failed:
> %s\n",
> +                               target, strerror(errno));
> +                       return -1;
> +               }
> +
> +               if (mount(target, target, "none", MS_BIND, NULL)) {
> +                       fprintf(stderr, "mount --bind %s %s failed:
> %s\n",
> +                               target, target, strerror(errno));
> +                       return -1;
> +               }
> +
> +               bind_done = true;
> +       }

Why does user space actually still have to deal with setting the mount
point private? Isn't this handled by the kernel?

> +       if (mount("bpf", target, "bpf", 0, NULL)) {
> +               fprintf(stderr, "mount -t bpf bpf %s failed: %s\n",
> +                       target, strerror(errno));
> +               return -1;
> +       }

Shouldn't this be just enough?

> +       return 0;
> +}

Thanks,
Hannes
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