Re: [PATCH net-next v3 4/5] ipv6: mld: encode multicast exponential fields

Ido Schimmel
2026-04-07T13:45:15Z

On Fri, Apr 03, 2026 at 03:00:49PM +0000, Ujjal Roy wrote:
> In MLD, QQIC and MRC fields are not correctly encoded when
> generating query packets. Since the receiver of the query
> interprets these fields using the MLDv2 floating-point
> decoding logic, any value that exceeds the linear threshold
> is incorrectly parsed as an exponential value, leading to
> an incorrect interval calculation.
>
> Encode and assign the corresponding protocol fields during
> query generation. Introduce the logic to dynamically
> calculate the exponent and mantissa using bit-scan (fls).
> This ensures QQIC (8-bit) and MRC (16-bit) fields are
> properly encoded when transmitting query packets with
> intervals that exceed their respective linear thresholds
> (128 for QQI; 32768 for MRD).
>
> RFC3810: If QQIC >= 128, the QQIC field represents a
> floating-point value as follows:
> 0 1 2 3 4 5 6 7
> +-+-+-+-+-+-+-+-+
> |1| exp | mant |
> +-+-+-+-+-+-+-+-+
>
> RFC3810: If Maximum Response Code >= 32768, the Maximum
> Response Code field represents a floating-point value as
> follows:
> 0 1 2 3 4 5 6 7 8 9 A B C D E F
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |1| exp | mant |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
> Signed-off-by: Ujjal Roy <royujjal@gmail.com>

Reviewed-by: Ido Schimmel <idosch@nvidia.com>