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| author | Daniel Borkmann <dborkman@redhat.com> | 2014-01-22 05:29:39 +0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-01-22 11:17:20 +0400 |
| commit | f337db64af059c9a94278a8b0ab97d87259ff62f (patch) | |
| tree | ef7db2258d5929760f2a22b74779d374916634bd /net/packet | |
| parent | 6cd28f044b47aeeba91807d97d6f3ea5a048e88d (diff) | |
| download | linux-f337db64af059c9a94278a8b0ab97d87259ff62f.tar.xz | |
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/packet')
| -rw-r--r-- | net/packet/af_packet.c | 2 |
1 files changed, 1 insertions, 1 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, |