IPv6: Fix algorithm to compute Querier's Query Interval and Maximum Response Delay

5.1.3. Maximum Response Code

The Maximum Response Code field specifies the maximum time allowed before sending a responding Report. The actual time allowed, called the Maximum Response Delay, is represented in units of milliseconds, and is derived from the Maximum Response Code as follows:

If Maximum Response Code < 32768,
Maximum Response Delay = Maximum Response Code

If Maximum Response Code >=32768, Maximum Response Code 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         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Maximum Response Delay = (mant | 0x1000) << (exp+3)

5.1.9. QQIC (Querier's Query Interval Code)

The Querier's Query Interval Code field specifies the [Query Interval] used by the Querier. The actual interval, called the Querier's Query Interval (QQI), is represented in units of seconds, and is derived from the Querier's Query Interval Code as follows:

If QQIC < 128, QQI = QQIC

If QQIC >= 128, QQIC represents a floating-point value as follows:

      0 1 2 3 4 5 6 7
     +-+-+-+-+-+-+-+-+
     |1| exp | mant  |
     +-+-+-+-+-+-+-+-+

QQI = (mant | 0x10) << (exp + 3)

                                               -- rfc3810

#define MLDV2_QQIC(value) MLDV2_EXP(0x80, 4, 3, value) #define MLDV2_MRC(value) MLDV2_EXP(0x8000, 12, 3, value)

Above macro are defined in mcast.c. but 1 << 4 == 0x10 and 1 << 12 == 0x1000. So the result computed by original Macro is larger.

Index: net/ipv6/mcast.c
===================================================================
@@ -164,7 +164,7 @@

#define MLDV2_MASK(value, nb) ((nb)>=32 ? (value) : ((1<<(nb))-1) & (value))

#define MLDV2_EXP(thresh, nbmant, nbexp, value) \
	((value) < (thresh) ? (value) : \
-	((MLDV2_MASK(value, nbmant) | (1<<(nbmant+nbexp))) << \
+	((MLDV2_MASK(value, nbmant) | (1<<(nbmant))) << \
	(MLDV2_MASK((value) >> (nbmant), nbexp) + (nbexp))))

#define MLDV2_QQIC(value) MLDV2_EXP(0x80, 4, 3, value)

Yes, I think you're correct.

Thanks, applying to my tree.

- Arnaldo