From: Martin KaFai Lau <martin.lau@linux.dev>
To: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
daniel@iogearbox.net, davem@davemloft.net, dsahern@kernel.org,
edumazet@google.com, haoluo@google.com, john.fastabend@gmail.com,
jolsa@kernel.org, kpsingh@kernel.org, kuba@kernel.org,
kuni1840@gmail.com, 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: Tue, 17 Oct 2023 23:19:39 -0700 [thread overview]
Message-ID: <469fd0e9-686f-f1dc-cb45-6c50ff126ccf@linux.dev> (raw)
In-Reply-To: <20231017164807.19824-1-kuniyu@amazon.com>
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? 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.
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.
next prev parent reply other threads:[~2023-10-18 6:20 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 [this message]
2023-10-18 8:02 ` Eric Dumazet
2023-10-18 17:20 ` Kuniyuki Iwashima
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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