From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
To: Marek Zavodsky <marek.zavodsky@gmail.com>
Cc: "Daniel Borkmann" <daniel@iogearbox.net>,
"Jesper Dangaard Brouer" <brouer@redhat.com>,
"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>
Subject: Re: BPF redirect API design issue for BPF-prog MTU feedback?
Date: Mon, 21 Sep 2020 23:17:16 +0200 [thread overview]
Message-ID: <CA+FuTSdx_a+DGG5dSFRB3wkowwNb1ZXHFed=qA3sj5y6U3VtiA@mail.gmail.com> (raw)
In-Reply-To: <CAG0p+LmqDXCJVygVtqvmsd2v4A=HRZdsGU3mSY0G=tGr2DoUvQ@mail.gmail.com>
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.
next prev parent reply other threads:[~2020-09-21 21:25 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 [this message]
2020-09-22 9:15 ` Jesper Dangaard Brouer
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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