On Tue, 16 Jul 2019 at 08:59, Eric Dumazet <eric.dumazet@xxxxxxxxx> 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?
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