On Wed, Jun 13, 2018 at 7:50 AM, Eric Dumazet <eric.duma...@gmail.com> wrote:
>
>
> On 06/12/2018 02:41 PM, Frank van der Linden wrote:
>> commit 079096f103fa ("tcp/dccp: install syn_recv requests into ehash
>> table") introduced an optimization for the handling of child sockets
>> created for a new TCP connection.
>>
>> But this optimization passes any data associated with the last ACK of the
>> connection handshake up the stack without verifying its checksum, because it
>> calls tcp_child_process(), which in turn calls tcp_rcv_state_process()
>> directly. These lower-level processing functions do not do any checksum
>> verification.
>>
>> Insert a tcp_checksum_complete call in the TCP_NEW_SYN_RECEIVE path to
>> fix this.
>>
>> Signed-off-by: Frank van der Linden <fllin...@amazon.com>
>
>
> This is way too complicated.
>
> You should call tcp_checksum_complete() earlier and avoid all this mess.
>
>
> IPV4 part shown here :
>
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index
> fed3f1c6616708997f621535efe9412e4afa0a50..7b5f32aa3835b0124b0a9bd342c371df7b46f471
> 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -1730,6 +1730,10 @@ int tcp_v4_rcv(struct sk_buff *skb)
> reqsk_put(req);
> goto discard_it;
> }
> + if (unlikely(tcp_checksum_complete(skb))) {
> + reqsk_put(req);
> + goto csum_error;
> + }
I like this variant, it is not under the sock_lock, but it skips
tcp_filter() as Frank pointed out.
I tested a variant of this patch with an increment of MIB/CSUM errors
and jump to discard_and_relse and it seemed to pass my testing
Balbir Singh.
