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From 405caa1424358032574230ec5479e64834869298 Mon Sep 17 00:00:00 2001
From: Alfredo Cardigliano <cardigliano@ntop.org>
Date: Thu, 13 Apr 2023 13:03:28 +0200
Subject: [PATCH] Implement probabilistic sampling
---
kernel/linux/pf_ring.h | 4 +++-
kernel/pf_ring.c | 34 ++++++++++++++++++++++++----------
2 files changed, 27 insertions(+), 11 deletions(-)
--- a/kernel/linux/pf_ring.h
+++ b/kernel/linux/pf_ring.h
@@ -1310,7 +1310,9 @@ struct pf_ring_socket {
u_char *ring_slots; /* Points to ring_memory+sizeof(FlowSlotInfo) */
/* Packet Sampling */
- u_int32_t pktToSample, sample_rate;
+ u_int32_t sample_rate;
+ u_int32_t pkts_to_sample;
+ u_int32_t sample_rnd_shift;
/* Virtual Filtering Device */
virtual_filtering_device_element *v_filtering_dev;
--- a/kernel/pf_ring.c
+++ b/kernel/pf_ring.c
@@ -3695,6 +3695,26 @@ int bpf_filter_skb(struct sk_buff *skb,
/* ********************************** */
+int sample_packet(struct pf_ring_socket *pfr) {
+ if(pfr->pkts_to_sample <= 1) {
+ u_int32_t rnd = 0;
+
+ get_random_bytes(&rnd, sizeof(u_int32_t));
+ rnd = rnd % pfr->sample_rate;
+
+ pfr->pkts_to_sample = pfr->sample_rate - pfr->sample_rnd_shift + rnd;
+
+ pfr->sample_rnd_shift = rnd;
+
+ return 1; /* Pass packet */
+ } else {
+ pfr->pkts_to_sample--;
+ return 0; /* Discard packet */
+ }
+}
+
+/* ********************************** */
+
u_int32_t default_rehash_rss_func(struct sk_buff *skb, struct pfring_pkthdr *hdr)
{
return hash_pkt_header(hdr, 0);
@@ -3805,12 +3825,9 @@ static int add_skb_to_ring(struct sk_buf
if(pfr->sample_rate > 1) {
spin_lock_bh(&pfr->ring_index_lock);
- if(pfr->pktToSample <= 1) {
- pfr->pktToSample = pfr->sample_rate;
- } else {
+ if(!sample_packet(pfr)) {
+ /* Discard packet */
pfr->slots_info->tot_pkts++;
- pfr->pktToSample--;
-
spin_unlock_bh(&pfr->ring_index_lock);
atomic_dec(&pfr->num_ring_users);
return(-1);
@@ -4161,11 +4178,8 @@ int pf_ring_skb_ring_handler(struct sk_b
if(pfr->sample_rate > 1) {
spin_lock_bh(&pfr->ring_index_lock);
- if(pfr->pktToSample <= 1) {
- pfr->pktToSample = pfr->sample_rate;
- } else {
+ if (!sample_packet(pfr)) {
pfr->slots_info->tot_pkts++;
- pfr->pktToSample--;
rc = 0;
}
spin_unlock_bh(&pfr->ring_index_lock);
@@ -7957,7 +7971,7 @@ static int ring_getsockopt(struct socket
if(copy_to_user(optval, lowest_if_mac, ETH_ALEN))
return(-EFAULT);
} else {
- char *dev_addr = pfr->ring_dev->dev->dev_addr;
+ const char *dev_addr = pfr->ring_dev->dev->dev_addr;
if (dev_addr == NULL) /* e.g. 'any' device */
dev_addr = empty_mac;
|