diff options
| author | Daniel Borkmann <dborkman@redhat.com> | 2014-01-22 02:29:39 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-01-21 23:17:20 -0800 |
| commit | f337db64af059c9a94278a8b0ab97d87259ff62f (patch) | |
| tree | ef7db2258d5929760f2a22b74779d374916634bd /net | |
| parent | 6cd28f044b47aeeba91807d97d6f3ea5a048e88d (diff) | |
random32: add prandom_u32_max and convert open coded users
Many functions have open coded a function that returns a random
number in range [0,N-1]. Under the assumption that we have a PRNG
such as taus113 with being well distributed in [0, ~0U] space,
we can implement such a function as uword t = (n*m')>>32, where
m' is a random number obtained from PRNG, n the right open interval
border and t our resulting random number, with n,m',t in u32 universe.
Lets go with Joe and simply call it prandom_u32_max(), although
technically we have an right open interval endpoint, but that we
have documented. Other users can further be migrated to the new
prandom_u32_max() function later on; for now, we need to make sure
to migrate reciprocal_divide() users for the reciprocal_divide()
follow-up fixup since their function signatures are going to change.
Joint work with Hannes Frederic Sowa.
Cc: Jakub Zawadzki <darkjames-ws@darkjames.pl>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/packet/af_packet.c | 2 | ||||
| -rw-r--r-- | net/sched/sch_choke.c | 9 |
2 files changed, 2 insertions, 9 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 59fb3db2e713..df3cbdd585c7 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1289,7 +1289,7 @@ static unsigned int fanout_demux_rnd(struct packet_fanout *f, struct sk_buff *skb, unsigned int num) { - return reciprocal_divide(prandom_u32(), num); + return prandom_u32_max(num); } static unsigned int fanout_demux_rollover(struct packet_fanout *f, diff --git a/net/sched/sch_choke.c b/net/sched/sch_choke.c index ddd73cb2d7ba..2aee02802c27 100644 --- a/net/sched/sch_choke.c +++ b/net/sched/sch_choke.c @@ -14,7 +14,6 @@ #include <linux/types.h> #include <linux/kernel.h> #include <linux/skbuff.h> -#include <linux/reciprocal_div.h> #include <linux/vmalloc.h> #include <net/pkt_sched.h> #include <net/inet_ecn.h> @@ -77,12 +76,6 @@ struct choke_sched_data { struct sk_buff **tab; }; -/* deliver a random number between 0 and N - 1 */ -static u32 random_N(unsigned int N) -{ - return reciprocal_divide(prandom_u32(), N); -} - /* number of elements in queue including holes */ static unsigned int choke_len(const struct choke_sched_data *q) { @@ -233,7 +226,7 @@ static struct sk_buff *choke_peek_random(const struct choke_sched_data *q, int retrys = 3; do { - *pidx = (q->head + random_N(choke_len(q))) & q->tab_mask; + *pidx = (q->head + prandom_u32_max(choke_len(q))) & q->tab_mask; skb = q->tab[*pidx]; if (skb) return skb; |