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From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: "Marek Zavodsky" <marek.zavodsky@gmail.com>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Lorenz Bauer" <lmb@cloudflare.com>,
"Maciej Żenczykowski" <maze@google.com>,
"Saeed Mahameed" <saeed@kernel.org>,
"Daniel Borkmann" <borkmann@iogearbox.net>,
"Alexei Starovoitov" <alexei.starovoitov@gmail.com>,
BPF-dev-list <bpf@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"Lorenzo Bianconi" <lorenzo.bianconi@redhat.com>,
"John Fastabend" <john.fastabend@gmail.com>,
"Jakub Kicinski" <kuba@kernel.org>,
"Shaun Crampton" <shaun@tigera.io>,
"David Miller" <davem@davemloft.net>,
"Marek Majkowski" <marek@cloudflare.com>,
brouer@redhat.com
Subject: Re: BPF redirect API design issue for BPF-prog MTU feedback?
Date: Tue, 22 Sep 2020 11:15:43 +0200 [thread overview]
Message-ID: <20200922111543.7cefb3b1@carbon> (raw)
In-Reply-To: <CA+FuTSdx_a+DGG5dSFRB3wkowwNb1ZXHFed=qA3sj5y6U3VtiA@mail.gmail.com>
On Mon, 21 Sep 2020 23:17:16 +0200
Willem de Bruijn <willemdebruijn.kernel@gmail.com> wrote:
> On Mon, Sep 21, 2020 at 6:22 PM Marek Zavodsky <marek.zavodsky@gmail.com> wrote:
> >
> > Hi guys,
> >
> > My kernel knowledge is small, but I experienced this (similar) issue
> > with packet encapsulation (not a redirect), therefore modifying the
> > redirect branch would not help in my case.
> >
> > I'm working on a TC program to do GUE encap/decap (IP + UDP + GUE,
> > outer header has extra 52B).
> > There are no issues with small packets. But when I use curl to
> > download big file HTTP server chunks data randomly. Some packets have
> > MTU size, others are even bigger. Big packets are not an issue,
> > however MTU sized packets fail on bpf_skb_adjust_room with -524
> > (ENOTSUPP).
>
> This is a related, but different, unresolved issue at the boundary of
> GSO packets. Packets that are not GSO, but would exceed MTU once
> encapsulated, will cause adjust room to fail:
>
> (!shrink && (skb->len + len_diff_abs > len_max &&
> !skb_is_gso(skb))))
> return -ENOTSUPP;
>
> As admin, this can be addressed by setting a lower route MTU on routes
> that may be encapsulated. But that is not very obvious or transparent.
Your issue is very much related, and even-though it is not related to
redirect, I also want to address and allow your use-case (in the
patchset that I'm collecting input for now).
I do think this patch[1][2] will actually solve your problem. Could
you please try to apply and test this to make sure? (as we have
discussed on this list, that patch is not a 100% solution, and I will
work on a better solution).
[1] https://lore.kernel.org/bpf/159921182827.1260200.9699352760916903781.stgit@firesoul
[2] http://patchwork.ozlabs.org/project/netdev/patch/159921182827.1260200.9699352760916903781.stgit@firesoul/
--
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:[~2020-09-22 9:16 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-17 12:38 BPF redirect API design issue for BPF-prog MTU feedback? Jesper Dangaard Brouer
2020-09-17 12:54 ` Maciej Żenczykowski
2020-09-17 19:11 ` Saeed Mahameed
2020-09-18 10:00 ` Jesper Dangaard Brouer
2020-09-18 10:34 ` Toke Høiland-Jørgensen
2020-09-18 23:06 ` Maciej Żenczykowski
2020-09-21 10:37 ` Lorenz Bauer
2020-09-21 12:49 ` Jesper Dangaard Brouer
2020-09-21 15:08 ` Daniel Borkmann
2020-09-21 16:21 ` Marek Zavodsky
2020-09-21 21:17 ` Willem de Bruijn
2020-09-22 9:15 ` Jesper Dangaard Brouer [this message]
2020-09-21 16:26 ` Jesper Dangaard Brouer
2020-09-22 6:56 ` Eyal Birger
2020-09-21 18:04 ` John Fastabend
2020-10-06 11:45 ` Jesper Dangaard Brouer
2020-09-21 10:42 ` Lorenz Bauer
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