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[78.154.15.142]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48722d38a5fsm86886705e9.12.2026.03.27.05.19.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 27 Mar 2026 05:19:24 -0700 (PDT) Message-ID: Date: Fri, 27 Mar 2026 14:19:23 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/4] ipv4: igmp: encode multicast exponential fields To: Ujjal Roy , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Ido Schimmel , David Ahern Cc: Ujjal Roy , bridge@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260326150742.50289-1-royujjal@gmail.com> <20260326150742.50289-4-royujjal@gmail.com> Content-Language: en-US From: Nikolay Aleksandrov In-Reply-To: <20260326150742.50289-4-royujjal@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 26/03/2026 17:07, Ujjal Roy wrote: > In IGMP, QQIC and MRC fields are not currently encoded > when generating query packets. Since the receiver of the > query interprets these fields using the IGMPv3 floating- > point decoding logic, any raw interval value that exceeds > the linear threshold is currently parsed incorrectly 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 > --- > include/linux/igmp.h | 80 +++++++++++++++++++++++++++++++++++++++ > net/bridge/br_multicast.c | 14 +++---- > 2 files changed, 86 insertions(+), 8 deletions(-) > [snip] > diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c > index 1438c023db62..1de6242413e0 100644 > --- a/net/bridge/br_multicast.c > +++ b/net/bridge/br_multicast.c > @@ -939,7 +939,7 @@ static struct sk_buff *br_ip4_multicast_alloc_query(struct net_bridge_mcast *brm > struct sk_buff *skb; > struct igmphdr *ih; > struct ethhdr *eth; > - unsigned long lmqt; > + unsigned long lmqt, mrt; > struct iphdr *iph; > u16 lmqt_srcs = 0; please keep reverse xmas tree order > > @@ -1004,15 +1004,15 @@ static struct sk_buff *br_ip4_multicast_alloc_query(struct net_bridge_mcast *brm > skb_put(skb, 24); > > skb_set_transport_header(skb, skb->len); > + mrt = group ? brmctx->multicast_last_member_interval : > + brmctx->multicast_query_response_interval; > *igmp_type = IGMP_HOST_MEMBERSHIP_QUERY; > > switch (brmctx->multicast_igmp_version) { > case 2: > ih = igmp_hdr(skb); > ih->type = IGMP_HOST_MEMBERSHIP_QUERY; > - ih->code = (group ? brmctx->multicast_last_member_interval : > - brmctx->multicast_query_response_interval) / > - (HZ / IGMP_TIMER_SCALE); > + ih->code = mrt / (HZ / IGMP_TIMER_SCALE); > ih->group = group; > ih->csum = 0; > csum = &ih->csum; > @@ -1021,11 +1021,9 @@ static struct sk_buff *br_ip4_multicast_alloc_query(struct net_bridge_mcast *brm > case 3: > ihv3 = igmpv3_query_hdr(skb); > ihv3->type = IGMP_HOST_MEMBERSHIP_QUERY; > - ihv3->code = (group ? brmctx->multicast_last_member_interval : > - brmctx->multicast_query_response_interval) / > - (HZ / IGMP_TIMER_SCALE); > + ihv3->code = igmpv3_mrc(mrt / (HZ / IGMP_TIMER_SCALE)); > ihv3->group = group; > - ihv3->qqic = brmctx->multicast_query_interval / HZ; > + ihv3->qqic = igmpv3_qqic(brmctx->multicast_query_interval / HZ); > ihv3->nsrcs = htons(lmqt_srcs); > ihv3->resv = 0; > ihv3->suppress = sflag;