netdev - Re: [bpf-next RFC 3/6] bpf: add bpf_tcp_gen

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Message-ID: <CACAyw9_5+3cznRspLJ2ZDcK22keLVtQQHbQOypSs4sx-F=ajow@mail.gmail.com>
Date:   Tue, 16 Jul 2019 12:56:15 +0100
From:   Lorenz Bauer <lmb@...udflare.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Petar Penkov <ppenkov.kernel@...il.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        davem@...emloft.net, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Eric Dumazet <edumazet@...gle.com>, sdf@...gle.com,
        Petar Penkov <ppenkov@...gle.com>
Subject: Re: [bpf-next RFC 3/6] bpf: add bpf_tcp_gen_syncookie helper

On Tue, 16 Jul 2019 at 08:59, Eric Dumazet <eric.dumazet@...il.com> wrote:
> > +             return -EINVAL;
> > +
> > +     if (sk->sk_protocol != IPPROTO_TCP || sk->sk_state != TCP_LISTEN)
> > +             return -EINVAL;
> > +
> > +     if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies)
> > +             return -EINVAL;
> > +
> > +     if (!th->syn || th->ack || th->fin || th->rst)
> > +             return -EINVAL;
> > +
> > +     switch (sk->sk_family) {
>
> This is strange, because a dual stack listener will have sk->sk_family set to AF_INET6.
>
> What really matters here is if the packet is IPv4 or IPv6.
>
> So you need to look at iph->version instead.
>
> Then look if the socket family allows this packet to be processed
> (For example AF_INET6 sockets might prevent IPv4 packets, see sk->sk_ipv6only )

Does this apply for (the existing) tcp_check_syn_cookie as well?

-- 
Lorenz Bauer  |  Systems Engineer
6th Floor, County Hall/The Riverside Building, SE1 7PB, UK

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