netdev - [PATCH net-next v3] openvswitch: Make 100 percents packets sampled when sampling rate is 1.

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Message-ID: <1438759847-27666-1-git-send-email-wenyuz@vmware.com>
Date:	Wed, 5 Aug 2015 00:30:47 -0700
From:	Wenyu Zhang <wenyuz@...are.com>
To:	<wenyuz@...are.com>, <jgross@...are.com>, <netdev@...r.kernel.org>,
	<dev@...nvswitch.org>
Subject: [PATCH net-next v3] openvswitch: Make 100 percents packets sampled when sampling rate is 1.

When sampling rate is 1, the sampling probability is UINT32_MAX. The packet
should be sampled even the prandom32() generate the number of UINT32_MAX.
And none packet need be sampled when the probability is 0.

Signed-off-by: Wenyu Zhang <wenyuz@...are.com>
---
 net/openvswitch/actions.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index cf04c2f..a0ac410 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -669,9 +669,12 @@ static int sample(struct datapath *dp, struct sk_buff *skb,
 
 	for (a = nla_data(attr), rem = nla_len(attr); rem > 0;
 		 a = nla_next(a, &rem)) {
+		u32 probability;
+
 		switch (nla_type(a)) {
 		case OVS_SAMPLE_ATTR_PROBABILITY:
-			if (prandom_u32() >= nla_get_u32(a))
+			probability = nla_get_u32(a);
+			if (!probability || prandom_u32() > probability)
 				return 0;
 			break;
 
-- 
1.7.9.5

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