Re: [PATCH v14 net-next 16/23] net/tcp: Ignore specific ICMPs for TCP-AO connections

[Dmitry Safonov <dima@arista.com>]

Hi Eric,

thanks once again for taking a look :)

On 10/11/23 18:53, Eric Dumazet wrote:
> On Tue, Oct 10, 2023 at 1:07 AM Dmitry Safonov <dima@arista.com> wrote:
[..]
>> +bool tcp_ao_ignore_icmp(const struct sock *sk, int type, int code)
>> +{
>> +       bool ignore_icmp = false;
>> +       struct tcp_ao_info *ao;
>> +
>> +       /* RFC5925, 7.8:
>> +        * >> A TCP-AO implementation MUST default to ignore incoming ICMPv4
>> +        * messages of Type 3 (destination unreachable), Codes 2-4 (protocol
>> +        * unreachable, port unreachable, and fragmentation needed -- ’hard
>> +        * errors’), and ICMPv6 Type 1 (destination unreachable), Code 1
>> +        * (administratively prohibited) and Code 4 (port unreachable) intended
>> +        * for connections in synchronized states (ESTABLISHED, FIN-WAIT-1, FIN-
>> +        * WAIT-2, CLOSE-WAIT, CLOSING, LAST-ACK, TIME-WAIT) that match MKTs.
>> +        */
>> +       if (READ_ONCE(sk->sk_family) == AF_INET) {
> 
> You can not use sk->sk_family to make this decision.
> 
>  It could be AF_INET6 and yet the flow could be IPv4.  (dual stack)
> 
> Let the caller pass this information ?
> 
>  tcp_ao_ignore_icmp(sk, AF_INET, type, code);
> 
>  tcp_ao_ignore_icmp(sk, AF_INET6, type, code);

Yes, I thought about it when added READ_ONCE(), but than probably got
distracted over possible IPV6_ADDRFORM races, rather than on correctness.

Looking at other places:
tcp_ao_prepare_reset() seems to do a proper thing for dual stack, but I
see it reads sk->sk_family twice, which needs to be addressed as well.
tcp_ao_connect_init() seems to do the right thing as well, but that is
hidden in tcp_ao_key_cmp().

Will fix in the next version.

Thanks,
             Dmitry