netdev - Re: [PATCH bpf-next v3 4/8] bpf: add helper to check for a valid SYN cookie

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Message-ID: <20190322020646.mnrpce2i2ooe6shi@ast-mbp.dhcp.thefacebook.com>
Date:   Thu, 21 Mar 2019 19:06:48 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Lorenz Bauer <lmb@...udflare.com>
Cc:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        bpf@...r.kernel.org, kafai@...com
Subject: Re: [PATCH bpf-next v3 4/8] bpf: add helper to check for a valid SYN
 cookie

On Fri, Mar 22, 2019 at 09:54:02AM +0800, Lorenz Bauer wrote:
> Using bpf_skc_lookup_tcp it's possible to ascertain whether a packet
> belongs to a known connection. However, there is one corner case: no
> sockets are created if SYN cookies are active. This means that the final
> ACK in the 3WHS is misclassified.
> 
> Using the helper, we can look up the listening socket via
> bpf_skc_lookup_tcp and then check whether a packet is a valid SYN
> cookie ACK.
> 
> Signed-off-by: Lorenz Bauer <lmb@...udflare.com>
...
> +static const struct bpf_func_proto bpf_tcp_check_syncookie_proto = {
> +	.func		= bpf_tcp_check_syncookie,
> +	.gpl_only	= true,

you really want your employer to open source the load balancer :)
Fine by me.

The series applied to bpf-next.