From: John Fastabend <john.fastabend@gmail.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>, bpf@vger.kernel.org
Cc: Jesper Dangaard Brouer <brouer@redhat.com>,
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
Subject: RE: [PATCH bpf-next V13 2/7] bpf: fix bpf_fib_lookup helper MTU check for SKB ctx
Date: Thu, 28 Jan 2021 22:00:38 -0800 [thread overview]
Message-ID: <6013a4869b7df_2683c20839@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <161159456224.321749.17429593575682232016.stgit@firesoul>
Jesper Dangaard Brouer wrote:
> BPF end-user on Cilium slack-channel (Carlo Carraro) wants to use
> bpf_fib_lookup for doing MTU-check, but *prior* to extending packet size,
> by adjusting fib_params 'tot_len' with the packet length plus the expected
> encap size. (Just like the bpf_check_mtu helper supports). He discovered
> that for SKB ctx the param->tot_len was not used, instead skb->len was used
> (via MTU check in is_skb_forwardable() that checks against netdev MTU).
>
> Fix this by using fib_params 'tot_len' for MTU check. If not provided (e.g.
> zero) then keep existing TC behaviour intact. Notice that 'tot_len' for MTU
> check is done like XDP code-path, which checks against FIB-dst MTU.
>
> V13:
> - Only do ifindex lookup one time, calling dev_get_by_index_rcu().
>
> V10:
> - Use same method as XDP for 'tot_len' MTU check
>
> Fixes: 4c79579b44b1 ("bpf: Change bpf_fib_lookup to return lookup status")
> Reported-by: Carlo Carraro <colrack@gmail.com>
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
> ---
Acked-by: John Fastabend <john.fastabend@gmail.com>
next prev parent reply other threads:[~2021-01-29 6:01 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-25 17:09 [PATCH bpf-next V13 0/7] bpf: New approach for BPF MTU handling Jesper Dangaard Brouer
2021-01-25 17:09 ` [PATCH bpf-next V13 1/7] bpf: Remove MTU check in __bpf_skb_max_len Jesper Dangaard Brouer
2021-01-25 17:09 ` [PATCH bpf-next V13 2/7] bpf: fix bpf_fib_lookup helper MTU check for SKB ctx Jesper Dangaard Brouer
2021-01-29 6:00 ` John Fastabend [this message]
2021-01-25 17:09 ` [PATCH bpf-next V13 3/7] bpf: bpf_fib_lookup return MTU value as output when looked up Jesper Dangaard Brouer
2021-01-29 6:06 ` John Fastabend
2021-01-25 17:09 ` [PATCH bpf-next V13 4/7] bpf: add BPF-helper for MTU checking Jesper Dangaard Brouer
2021-01-29 6:51 ` John Fastabend
2021-01-29 7:36 ` Jesper Dangaard Brouer
[not found] ` <60142eae7cd59_11fd208f1@john-XPS-13-9370.notmuch>
2021-01-30 0:08 ` Daniel Borkmann
2021-01-30 13:51 ` Jesper Dangaard Brouer
2021-01-25 17:09 ` [PATCH bpf-next V13 5/7] bpf: drop MTU check when doing TC-BPF redirect to ingress Jesper Dangaard Brouer
2021-01-29 6:54 ` John Fastabend
2021-01-25 17:09 ` [PATCH bpf-next V13 6/7] selftests/bpf: use bpf_check_mtu in selftest test_cls_redirect Jesper Dangaard Brouer
2021-01-29 6:55 ` John Fastabend
2021-01-25 17:09 ` [PATCH bpf-next V13 7/7] selftests/bpf: tests using bpf_check_mtu BPF-helper Jesper Dangaard Brouer
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