Subject: Re: [PATCH net-next v3 3/5] ipv4: igmp: encode multicast exponential fields

From: Ido Schimmel <[email-masked]>
Date: Tue, 7 Apr 2026 16:44:46 +0300

On Fri, Apr 03, 2026 at 03:00:48PM +0000, Ujjal Roy wrote:
> In IGMP, QQIC and MRC fields are not correctly encoded
> when generating query packets. Since the receiver of the
> query interprets these fields using the IGMPv3 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 and MRC fields (8-bit) are properly
> encoded when transmitting query packets with intervals
> that exceed their respective linear threshold value of
> 128 (for QQI/MRT).
> 
> RFC 3376: if QQIC/MRC >= 128, the QQIC/MRC field represents
> a floating-point value as follows:
>      0 1 2 3 4 5 6 7
>     +-+-+-+-+-+-+-+-+
>     |1| exp | mant  |
>     +-+-+-+-+-+-+-+-+
> 
> Signed-off-by: Ujjal Roy <[email-masked]>

Same comments as on the previous patches, but otherwise LGTM