From 9ccd037fa0c77d680e1306dfdd0d6bfddf8b05a2 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Wed, 22 Jan 2014 02:29:39 +0100 Subject: 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 Cc: Eric Dumazet Cc: linux-kernel@vger.kernel.org Signed-off-by: Hannes Frederic Sowa Signed-off-by: Daniel Borkmann Signed-off-by: David S. Miller Conflicts: net/packet/af_packet.c --- net/packet/af_packet.c | 7 +++++++ net/sched/sch_choke.c | 9 +-------- 2 files changed, 8 insertions(+), 8 deletions(-) (limited to 'net') diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 2d454a235..a58f9a895 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1173,6 +1173,13 @@ static unsigned int fanout_demux_cpu(struct packet_fanout *f, return smp_processor_id() % num; } +static unsigned int fanout_demux_rnd(struct packet_fanout *f, + struct sk_buff *skb, + unsigned int num) +{ + return prandom_u32_max(num); +} + static unsigned int fanout_demux_rollover(struct packet_fanout *f, struct sk_buff *skb, unsigned int idx, unsigned int skip, diff --git a/net/sched/sch_choke.c b/net/sched/sch_choke.c index ef53ab8d0..7ce6ec04f 100644 --- a/net/sched/sch_choke.c +++ b/net/sched/sch_choke.c @@ -14,7 +14,6 @@ #include #include #include -#include #include #include #include @@ -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; -- cgit v1.2.3