From: Kuniyuki Iwashima <kuniyu@amazon.com>
To: <edumazet@google.com>
Cc: <andrii@kernel.org>, <ast@kernel.org>, <bpf@vger.kernel.org>,
<daniel@iogearbox.net>, <davem@davemloft.net>,
<dsahern@kernel.org>, <haoluo@google.com>,
<john.fastabend@gmail.com>, <jolsa@kernel.org>,
<kpsingh@kernel.org>, <kuba@kernel.org>, <kuni1840@gmail.com>,
<kuniyu@amazon.com>, <martin.lau@linux.dev>, <mykolal@fb.com>,
<netdev@vger.kernel.org>, <pabeni@redhat.com>, <sdf@google.com>,
<song@kernel.org>, <yonghong.song@linux.dev>
Subject: Re: [PATCH v1 bpf-next 00/11] bpf: tcp: Add SYN Cookie generation/validation SOCK_OPS hooks.
Date: Wed, 18 Oct 2023 10:20:27 -0700 [thread overview]
Message-ID: <20231018172027.9936-1-kuniyu@amazon.com> (raw)
In-Reply-To: <CANn89iLZDvqrGy9UJ39a49O3NLT74r+5FXfh7u3SxSSm60BJmA@mail.gmail.com>
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 18 Oct 2023 10:02:51 +0200
> On Wed, Oct 18, 2023 at 8:19 AM Martin KaFai Lau <martin.lau@linux.dev> wrote:
> >
> > On 10/17/23 9:48 AM, Kuniyuki Iwashima wrote:
> > > From: Martin KaFai Lau <martin.lau@linux.dev>
> > > Date: Mon, 16 Oct 2023 22:53:15 -0700
> > >> On 10/13/23 3:04 PM, Kuniyuki Iwashima wrote:
> > >>> Under SYN Flood, the TCP stack generates SYN Cookie to remain stateless
> > >>> After 3WHS, the proxy restores SYN and forwards it and ACK to the backend
> > >>> server. Our kernel module works at Netfilter input/output hooks and first
> > >>> feeds SYN to the TCP stack to initiate 3WHS. When the module is triggered
> > >>> for SYN+ACK, it looks up the corresponding request socket and overwrites
> > >>> tcp_rsk(req)->snt_isn with the proxy's cookie. Then, the module can
> > >>> complete 3WHS with the original ACK as is.
> > >>
> > >> Does the current kernel module also use the timestamp bits differently?
> > >> (something like patch 8 and patch 10 trying to do)
> > >
> > > Our SYN Proxy uses TS as is. The proxy nodes generate a random number
> > > if TS is in SYN.
> > >
> > > But I thought someone would suggest making TS available so that we can
> > > mock the default behaviour at least, and it would be more acceptable.
> > >
> > > The selftest uses TS just to strengthen security by validating 32-bits
> > > hash. Dropping a part of hash makes collision easier to happen, but
> > > 24-bits were sufficient for us to reduce SYN flood to the managable
> > > level at the backend.
> >
> > While enabling bpf to customize the syncookie (and timestamp), I want to explore
> > where can this also be done other than at the tcp layer.
> >
> > Have you thought about directly sending the SYNACK back at a lower layer like
> > tc/xdp after receiving the SYN?
Yes. Actually, at netconf I mentioned the cookie generation hook will not
be necessary and should be replaced with XDP.
> > There are already bpf_tcp_{gen,check}_syncookie
> > helper that allows to do this for the performance reason to absorb synflood. It
> > will be natural to extend it to handle the customized syncookie also.
Maybe we even need not extend it and can use XDP as said below.
> >
> > I think it should already be doable to send a SYNACK back with customized
> > syncookie (and timestamp) at tc/xdp today.
> >
> > When ack is received, the prog@tc/xdp can verify the cookie. It will probably
> > need some new kfuncs to create the ireq and queue the child socket. The bpf prog
> > can change the ireq->{snd_wscale, sack_ok...} if needed. The details of the
> > kfuncs need some more thoughts. I think most of the bpf-side infra is ready,
> > e.g. acquire/release/ref-tracking...etc.
> >
>
> I think I mostly agree with this.
I didn't come up with kfunc to create ireq and queue it to listener, so
cookie_v[46]_check() were best place for me to extend easily, but now it
sounds like kfunc would be the way to go.
Maybe we can move the core part of cookie_v[46]_check() except for kernel
cookie's validation to __cookie_v[46]_check() and expose a wrapper of it
as kfunc ?
Then, we can look up sk and pass the listener, skb, and flags (for sack_ok,
etc) to the kfunc. (It could still introduce some conflicts with Eric's
patch though...)
>
> I am rebasing a patch adding usec resolution to TCP TS,
> that we used for about 10 years at Google, because it is time to upstream it.
>
> I am worried about more changes/conflicts caused by Kuniyuki patch set...
next prev parent reply other threads:[~2023-10-18 17:20 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-13 22:04 [PATCH v1 bpf-next 00/11] bpf: tcp: Add SYN Cookie generation/validation SOCK_OPS hooks Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 01/11] tcp: Clean up reverse xmas tree in cookie_v[46]_check() Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 02/11] tcp: Cache sock_net(sk) " Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 03/11] tcp: Clean up goto labels " Kuniyuki Iwashima
2023-10-17 0:00 ` Kui-Feng Lee
2023-10-17 0:30 ` Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 04/11] tcp: Don't initialise tp->tsoffset in tcp_get_cookie_sock() Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 05/11] bpf: tcp: Add SYN Cookie generation SOCK_OPS hook Kuniyuki Iwashima
2023-10-18 0:54 ` Martin KaFai Lau
2023-10-18 17:00 ` Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 06/11] bpf: tcp: Add SYN Cookie validation " Kuniyuki Iwashima
2023-10-16 20:38 ` Stanislav Fomichev
2023-10-16 22:02 ` Kuniyuki Iwashima
2023-10-17 16:52 ` Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 07/11] bpf: Make bpf_sock_ops.replylong[1] writable Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 08/11] bpf: tcp: Make TS available for SYN Cookie storage Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 09/11] tcp: Split cookie_ecn_ok() Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 10/11] bpf: tcp: Make WS, SACK, ECN configurable from BPF SYN Cookie Kuniyuki Iwashima
2023-10-18 1:08 ` Martin KaFai Lau
2023-10-18 17:02 ` Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 11/11] selftest: bpf: Test BPF_SOCK_OPS_(GEN|CHECK)_SYNCOOKIE_CB Kuniyuki Iwashima
2023-10-17 5:50 ` Martin KaFai Lau
2023-10-17 16:29 ` Kuniyuki Iwashima
2023-10-16 13:05 ` [PATCH v1 bpf-next 00/11] bpf: tcp: Add SYN Cookie generation/validation SOCK_OPS hooks Daniel Borkmann
2023-10-16 16:11 ` Kuniyuki Iwashima
2023-10-16 14:19 ` Willem de Bruijn
2023-10-16 16:46 ` Kuniyuki Iwashima
2023-10-16 18:41 ` Willem de Bruijn
2023-10-17 5:53 ` Martin KaFai Lau
2023-10-17 16:48 ` Kuniyuki Iwashima
2023-10-18 6:19 ` Martin KaFai Lau
2023-10-18 8:02 ` Eric Dumazet
2023-10-18 17:20 ` Kuniyuki Iwashima [this message]
2023-10-18 21:47 ` Kui-Feng Lee
2023-10-18 22:31 ` Kuniyuki Iwashima
2023-10-19 7:25 ` Martin KaFai Lau
2023-10-19 18:01 ` Kuniyuki Iwashima
2023-10-20 19:59 ` Martin KaFai Lau
2023-10-20 23:10 ` Kuniyuki Iwashima
2023-10-21 6:48 ` Kuniyuki Iwashima
2023-10-23 21:35 ` Martin KaFai Lau
2023-10-24 0:37 ` Kui-Feng Lee
2023-10-24 1:22 ` Kuniyuki Iwashima
2023-10-24 17:55 ` Kui-Feng Lee
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