2005-10-28 16:00:53

by Yan Zheng

Subject: [PATH] [MCAST] 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.


Signed-off-by: Yan Zheng <[email protected]>

Index: net/ipv6/mcast.c
===================================================================
--- linux-2.6.14/net/ipv6/mcast.c 2005-10-28 08:02:08.000000000 +0800
+++ linux/net/ipv6/mcast.c 2005-10-28 23:41:18.000000000 +0800
@@ -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)

2005-10-28 17:18:38

by David Stevens

Subject: Re: [PATH] [MCAST] IPv6: Fix algorithm to compute Querier's Query Interval and Maximum Response Delay

Yes, I think you're correct.

Acked-by: David L Stevens <[email protected]>
>
> Signed-off-by: Yan Zheng <[email protected]>
>
> Index: net/ipv6/mcast.c
> ===================================================================
> --- linux-2.6.14/net/ipv6/mcast.c 2005-10-28 08:02:08.000000000 +0800
> +++ linux/net/ipv6/mcast.c 2005-10-28 23:41:18.000000000 +0800
> @@ -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)
>
> -
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2005-10-28 18:19:49

by Arnaldo Carvalho de Melo

Subject: Re: [PATH] [MCAST] IPv6: Fix algorithm to compute Querier's Query Interval and Maximum Response Delay

On 10/28/05, David Stevens <[email protected]> wrote:
> Yes, I think you're correct.
>
> Acked-by: David L Stevens <[email protected]>

Thanks, applying to my tree.

- Arnaldo