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References: <20210112194143.1494-1-yuri.benditovich@daynix.com> <20210112194143.1494-4-yuri.benditovich@daynix.com>
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From:   Yuri Benditovich <yuri.benditovich@daynix.com>
Date:   Tue, 12 Jan 2021 22:40:42 +0200
Message-ID: <CAOEp5Ocz-xGq5=e=WY0aipEYHEhN-wxekNaAiqAS+HsOF8TcDQ@mail.gmail.com>
Subject: Re: [RFC PATCH 3/7] tun: allow use of BPF_PROG_TYPE_SCHED_CLS program type
To:     "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        "Michael S . Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>, rdunlap@infradead.org,
        willemb@google.com, gustavoars@kernel.org,
        herbert@gondor.apana.org.au, steffen.klassert@secunet.com,
        pablo@netfilter.org, decui@microsoft.com, cai@lca.pw,
        jakub@cloudflare.com, elver@google.com, pabeni@redhat.com,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        bpf@vger.kernel.org
Cc:     Yan Vugenfirer <yan@daynix.com>
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On Tue, Jan 12, 2021 at 9:42 PM Yuri Benditovich
<yuri.benditovich@daynix.com> wrote:
>
> This program type can set skb hash value. It will be useful
> when the tun will support hash reporting feature if virtio-net.
>
> Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
> ---
>  drivers/net/tun.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 7959b5c2d11f..455f7afc1f36 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2981,6 +2981,8 @@ static int tun_set_ebpf(struct tun_struct *tun, struct tun_prog __rcu **prog_p,
>                 prog = NULL;
>         } else {
>                 prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
> +               if (IS_ERR(prog))
> +                       prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SCHED_CLS);
>                 if (IS_ERR(prog))
>                         return PTR_ERR(prog);
>         }

Comment from Alexei Starovoitov:
Patches 1 and 2 are missing for me, so I couldn't review properly,
but this diff looks odd.
It allows sched_cls prog type to attach to tun.
That means everything that sched_cls progs can do will be done from tun hook?
sched_cls assumes l2 and can modify the packet.
I think crashes are inevitable.

> --
> 2.17.1
>