netdev - Re: [bpf-next,v2 0/6] Introduce a BPF helper to generate SYN cookies

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Date:   Mon, 29 Jul 2019 16:45:53 -0700
From:   Petar Penkov <ppenkov@...gle.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Petar Penkov <ppenkov.kernel@...il.com>,
        Networking <netdev@...r.kernel.org>, bpf@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Eric Dumazet <edumazet@...gle.com>, lmb@...udflare.com,
        Stanislav Fomichev <sdf@...gle.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [bpf-next,v2 0/6] Introduce a BPF helper to generate SYN cookies

On Mon, Jul 29, 2019 at 1:48 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Mon, Jul 29, 2019 at 09:59:12AM -0700, Petar Penkov wrote:
> > From: Petar Penkov <ppenkov@...gle.com>
> >
> > This patch series introduces a BPF helper function that allows generating SYN
> > cookies from BPF. Currently, this helper is enabled at both the TC hook and the
> > XDP hook.
> >
> > The first two patches in the series add/modify several TCP helper functions to
> > allow for SKB-less operation, as is the case at the XDP hook.
> >
> > The third patch introduces the bpf_tcp_gen_syncookie helper function which
> > generates a SYN cookie for either XDP or TC programs. The return value of
> > this function contains both the MSS value, encoded in the cookie, and the
> > cookie itself.
> >
> > The last three patches sync tools/ and add a test.
> >
> > Performance evaluation:
> > I sent 10Mpps to a fixed port on a host with 2 10G bonded Mellanox 4 NICs from
> > random IPv6 source addresses. Without XDP I observed 7.2Mpps (syn-acks) being
> > sent out if the IPv6 packets carry 20 bytes of TCP options or 7.6Mpps if they
> > carry no options. If I attached a simple program that checks if a packet is
> > IPv6/TCP/SYN, looks up the socket, issues a cookie, and sends it back out after
> > swapping src/dest, recomputing the checksum, and setting the ACK flag, I
> > observed 10Mpps being sent back out.
>

Thank you for reviewing this so quickly!
> Is it 10m because trafic gen is 10m?
Yes, I believe so.

> What is cpu utilization at this rate?
> Is it cpu or nic limited if you crank up the syn flood?
> Original 7M with all cores or single core?
My receiver was configured with 16rx queues and 16 cores. 7M all cores
are at 100% so I believe this case is CPU limited. At XDP, all cores
are at roughly 40%. I couldn't reliably generate higher SYN flood rate
than that, and the highest numbers I could see for XDP did not go past
10.65Mpps with ~42% utilization on each core. I think I am hitting a
NIC limit here since the CPUs are free.


>
> The patch set looks good to me.
> I'd like Eric to review it one more time before applying.
>