Re: [PATCH mptcp-next v9 2/6] mptcp: accept right edge of mapping validating

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

On Thu, 23 Jun 2022, Geliang Tang wrote:

> If ssn is at the right edge of DSS mapping (ssn == subflow->map_subflow_seq
> + subflow->map_data_len), it shouldn't be handled as a bad map. This
> happens in the redundant subflows test cases.
>
> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
> net/mptcp/subflow.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
> index 63e8892ec807..69a2c3e6fd76 100644
> --- a/net/mptcp/subflow.c
> +++ b/net/mptcp/subflow.c
> @@ -878,8 +878,8 @@ static bool validate_mapping(struct sock *ssk, struct sk_buff *skb)
> 		dbg_bad_map(subflow, ssn);
> 		return false;
> 	}
> -	if (unlikely(!before(ssn, subflow->map_subflow_seq +
> -				  subflow->map_data_len))) {
> +	if (unlikely(after(ssn, subflow->map_subflow_seq +
> +				subflow->map_data_len))) {

I'm not sure this correct.

For example, if subflow->map_data_len == 1, then ssn can only be equal to 
subflow->map_subflow_seq. Changing this to after() allows the skb to 
include an extra byte that isn't covered by the mapping.

> 		/* Mapping does covers past subflow data, invalid */
> 		dbg_bad_map(subflow, ssn);
> 		return false;
> -- 
> 2.35.3
>
>
>

--
Mat Martineau
Intel