Re: [PATCH net-next v5 4/5] ipv6: mld: encode multicast exponential fields

[Nikolay Aleksandrov <razor@blackwall.org>]

On 01/05/2026 20:31, Ujjal Roy wrote:
> In MLD, MRC and QQIC 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 MRC (16-bit) and QQIC (8-bit) fields are
> properly encoded when transmitting query packets with
> intervals that exceed their respective linear thresholds
> (32768 for MRD; 128 for QQI).
> 
> 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         |
>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> 
> 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  |
>      +-+-+-+-+-+-+-+-+
> 
> Reviewed-by: Ido Schimmel <idosch@nvidia.com>
> Signed-off-by: Ujjal Roy <royujjal@gmail.com>
> ---
>   include/net/mld.h         | 119 ++++++++++++++++++++++++++++++++++++++
>   net/bridge/br_multicast.c |   4 +-
>   2 files changed, 121 insertions(+), 2 deletions(-)
> 

Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>