From: Jesper Dangaard Brouer <brouer@redhat.com>
To: sdf@google.com
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
Daniel Borkmann <borkmann@iogearbox.net>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
maze@google.com, lmb@cloudflare.com, shaun@tigera.io,
Lorenzo Bianconi <lorenzo@kernel.org>,
marek@cloudflare.com, John Fastabend <john.fastabend@gmail.com>,
Jakub Kicinski <kuba@kernel.org>,
eyal.birger@gmail.com, colrack@gmail.com, brouer@redhat.com
Subject: Re: [PATCH bpf-next V7 4/8] bpf: add BPF-helper for MTU checking
Date: Mon, 14 Dec 2020 12:52:42 +0100 [thread overview]
Message-ID: <20201214125242.7cea3ecb@carbon> (raw)
In-Reply-To: <X8ktpX/BYfiL0l2l@google.com>
On Thu, 3 Dec 2020 10:25:41 -0800
sdf@google.com wrote:
> > +BPF_CALL_5(bpf_skb_check_mtu, struct sk_buff *, skb,
> > + u32, ifindex, u32 *, mtu_len, s32, len_diff, u64, flags)
> > +{
> > + int ret = BPF_MTU_CHK_RET_FRAG_NEEDED;
> > + struct net_device *dev = skb->dev;
> > + int len;
> > + int mtu;
> > +
> > + if (flags & ~(BPF_MTU_CHK_SEGS))
> > + return -EINVAL;
> > +
> > + dev = __dev_via_ifindex(dev, ifindex);
> > + if (!dev)
> > + return -ENODEV;
> > +
> > + mtu = READ_ONCE(dev->mtu);
> > +
> > + /* TC len is L2, remove L2-header as dev MTU is L3 size */
>
> [..]
> > + len = skb->len - ETH_HLEN;
> Any reason not to do s/ETH_HLEN/dev->hard_header_len/ (or min_header_len?)
> thought this patch?
Will fix in V9.
There is a very small (performance) overhead, but mostly because
net_device struct layout have placed mtu and hard_header_len on
different cache-lines. (This is something that should be fixed
separately).
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
next prev parent reply other threads:[~2020-12-14 11:54 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-20 16:18 [PATCH bpf-next V7 0/8] bpf: New approach for BPF MTU handling Jesper Dangaard Brouer
2020-11-20 16:18 ` [PATCH bpf-next V7 1/8] bpf: Remove MTU check in __bpf_skb_max_len Jesper Dangaard Brouer
2020-11-20 16:18 ` [PATCH bpf-next V7 2/8] bpf: fix bpf_fib_lookup helper MTU check for SKB ctx Jesper Dangaard Brouer
2020-12-02 21:44 ` Daniel Borkmann
2020-12-02 22:00 ` Daniel Borkmann
2020-11-20 16:18 ` [PATCH bpf-next V7 3/8] bpf: bpf_fib_lookup return MTU value as output when looked up Jesper Dangaard Brouer
2020-11-20 16:18 ` [PATCH bpf-next V7 4/8] bpf: add BPF-helper for MTU checking Jesper Dangaard Brouer
2020-12-03 18:25 ` sdf
2020-12-14 11:52 ` Jesper Dangaard Brouer [this message]
2020-11-20 16:18 ` [PATCH bpf-next V7 5/8] bpf: drop MTU check when doing TC-BPF redirect to ingress Jesper Dangaard Brouer
2020-11-20 16:18 ` [PATCH bpf-next V7 6/8] bpf: make it possible to identify BPF redirected SKBs Jesper Dangaard Brouer
2020-11-20 16:18 ` [PATCH bpf-next V7 7/8] selftests/bpf: use bpf_check_mtu in selftest test_cls_redirect Jesper Dangaard Brouer
2020-11-20 16:18 ` [PATCH bpf-next V7 8/8] bpf/selftests: activating bpf_check_mtu BPF-helper Jesper Dangaard Brouer
2020-11-20 21:50 ` Alexei Starovoitov
2020-11-21 7:41 ` Andrii Nakryiko
2020-11-24 14:33 ` Jesper Dangaard Brouer
2020-11-24 16:50 ` Yonghong Song
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