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ipv4: igmp: get rid of IGMPV3_{QQIC,MRC} and simplify calculation

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Get rid of the IGMPV3_MRC macro and use the igmpv3_mrt() API to
calculate the Max Resp Time from the Maximum Response Code.

Similarly, for IGMPV3_QQIC, use the igmpv3_qqi() API to calculate
the Querier's Query Interval from the QQIC field.

Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Ujjal Roy <royujjal@gmail.com>
Link: https://patch.msgid.link/20260502131907.987-2-royujjal@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Ujjal Roy
2026-05-02 13:19:02 +00:00
committed by Jakub Kicinski
parent 43c6720d34
commit 726fa7da2d
3 changed files with 76 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

80
include/linux/igmp.h
View File

@@ -92,15 +92,79 @@ struct ip_mc_list {
struct rcu_head rcu;
};
/* V3 exponential field decoding */
#define IGMPV3_MASK(value, nb) ((nb)>=32 ? (value) : ((1<<(nb))-1) & (value))
#define IGMPV3_EXP(thresh, nbmant, nbexp, value) \
((value) < (thresh) ? (value) : \
((IGMPV3_MASK(value, nbmant) | (1<<(nbmant))) << \
(IGMPV3_MASK((value) >> (nbmant), nbexp) + (nbexp))))
/* RFC3376, relevant sections:
* - 4.1.1. Maximum Response Code
* - 4.1.7. QQIC (Querier's Query Interval Code)
*
* For both MRC and QQIC, values >= 128 use the same floating-point
* encoding as follows:
*
* 0 1 2 3 4 5 6 7
* +-+-+-+-+-+-+-+-+
* |1| exp | mant |
* +-+-+-+-+-+-+-+-+
*/
#define IGMPV3_FP_EXP(value) (((value) >> 4) & 0x07)
#define IGMPV3_FP_MAN(value) ((value) & 0x0f)
#define IGMPV3_QQIC(value) IGMPV3_EXP(0x80, 4, 3, value)
#define IGMPV3_MRC(value) IGMPV3_EXP(0x80, 4, 3, value)
/* IGMPv3 floating-point exponential field min threshold */
#define IGMPV3_EXP_MIN_THRESHOLD 128
/* V3 exponential field decoding */
/* IGMPv3 MRC/QQIC 8-bit exponential field decode
*
* RFC3376, 4.1.1 & 4.1.7. defines the decoding formula:
* 0 1 2 3 4 5 6 7
* +-+-+-+-+-+-+-+-+
* |1| exp | mant |
* +-+-+-+-+-+-+-+-+
* Max Resp Time = (mant | 0x10) << (exp + 3)
* QQI = (mant | 0x10) << (exp + 3)
*/
static inline unsigned long igmpv3_exp_field_decode(const u8 code)
{
if (code < IGMPV3_EXP_MIN_THRESHOLD) {
return code;
} else {
unsigned long mc_man, mc_exp;
mc_exp = IGMPV3_FP_EXP(code);
mc_man = IGMPV3_FP_MAN(code);
return (mc_man | 0x10) << (mc_exp + 3);
}
}
/* Calculate Max Resp Time from Maximum Response Code
*
* RFC3376, relevant sections:
* - 4.1.1. Maximum Response Code
* - 8.3. Query Response Interval
*
* After decode, MRC represents the Maximum Response Time (MRT) in
* units of 0.1 seconds (100 ms).
*/
static inline unsigned long igmpv3_mrt(const struct igmpv3_query *ih3)
{
return igmpv3_exp_field_decode(ih3->code);
}
/* Calculate Querier's Query Interval from Querier's Query Interval Code
*
* RFC3376, relevant sections:
* - 4.1.7. QQIC (Querier's Query Interval Code)
* - 8.2. Query Interval
* - 8.12. Older Version Querier Present Timeout
* (the [Query Interval] in the last Query received)
*
* After decode, QQIC represents the Querier's Query Interval in units
* of seconds.
*/
static inline unsigned long igmpv3_qqi(const struct igmpv3_query *ih3)
{
return igmpv3_exp_field_decode(ih3->qqic);
}
static inline int ip_mc_may_pull(struct sk_buff *skb, unsigned int len)
{

2
net/bridge/br_multicast.c
View File

@@ -3518,7 +3518,7 @@ static void br_ip4_multicast_query(struct net_bridge_mcast *brmctx,
goto out;
max_delay = ih3->code ?
IGMPV3_MRC(ih3->code) * (HZ / IGMP_TIMER_SCALE) : 1;
igmpv3_mrt(ih3) * (HZ / IGMP_TIMER_SCALE) : 1;
} else {
goto out;
}

6
net/ipv4/igmp.c
View File

@@ -991,7 +991,7 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
* different encoding. We use the v3 encoding as more likely
* to be intended in a v3 query.
*/
max_delay = IGMPV3_MRC(ih3->code)*(HZ/IGMP_TIMER_SCALE);
max_delay = igmpv3_mrt(ih3) * (HZ / IGMP_TIMER_SCALE);
if (!max_delay)
max_delay = 1; /* can't mod w/ 0 */
} else { /* v3 */
@@ -1006,7 +1006,7 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
ih3 = igmpv3_query_hdr(skb);
}
max_delay = IGMPV3_MRC(ih3->code)*(HZ/IGMP_TIMER_SCALE);
max_delay = igmpv3_mrt(ih3) * (HZ / IGMP_TIMER_SCALE);
if (!max_delay)
max_delay = 1; /* can't mod w/ 0 */
WRITE_ONCE(in_dev->mr_maxdelay, max_delay);
@@ -1016,7 +1016,7 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
* configured value.
*/
in_dev->mr_qrv = ih3->qrv ?: READ_ONCE(net->ipv4.sysctl_igmp_qrv);
in_dev->mr_qi = IGMPV3_QQIC(ih3->qqic)*HZ ?: IGMP_QUERY_INTERVAL;
in_dev->mr_qi = igmpv3_qqi(ih3) * HZ ? : IGMP_QUERY_INTERVAL;
/* RFC3376, 8.3. Query Response Interval:
* The number of seconds represented by the [Query Response