From 82a19cac1ff99b0dbc59622a2430f0f8e0050e48 Mon Sep 17 00:00:00 2001
From: Neil McKee <neil.mckee@inmon.com>
Date: Tue, 14 Mar 2023 16:30:32 -0700
Subject: [PATCH] allow pcap{} config to override sampling rate

---
 hsflowd.spec             |  2 +-
 src/Linux/hsflowconfig.c | 25 ++++++++++++++++++++-----
 src/Linux/hsflowd.h      |  3 +++
 src/Linux/mod_pcap.c     |  8 ++++++--
 4 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/hsflowd.spec b/hsflowd.spec
index a543471..7a38307 100644
--- a/hsflowd.spec
+++ b/hsflowd.spec
@@ -1,7 +1,7 @@
 Summary: host sFlow daemon
 Name: hsflowd
 Version: 2.0.47
-Release: 2
+Release: 3
 License: http://sflow.net/license.html
 Group: Applications/Internet
 URL: http://sflow.net
diff --git a/src/Linux/hsflowconfig.c b/src/Linux/hsflowconfig.c
index e9ec0c4..77d3e40 100644
--- a/src/Linux/hsflowconfig.c
+++ b/src/Linux/hsflowconfig.c
@@ -824,8 +824,8 @@ extern "C" {
 	method = "interface_down";
       }
       else {
-	char speedStr[51];
 	if(adaptor->ifSpeed) {
+	  char speedStr[51];
 	  if(printSpeed(adaptor->ifSpeed, speedStr, 50)
 	     && lookupApplicationSettings(settings, NULL, speedStr, &sampling_n, NULL)) {
 	    method = speedStr;
@@ -834,11 +834,22 @@ extern "C" {
 	    // calcuate default sampling rate based on link speed.  This ensures
 	    // that a network switch comes up with manageable defaults even if
 	    // the config file is empty...
-	    sampling_n = adaptor->ifSpeed / HSP_SPEED_SAMPLING_RATIO;
-	    if(sampling_n < HSP_SPEED_SAMPLING_MIN) {
-	      sampling_n = HSP_SPEED_SAMPLING_MIN;
+	    uint32_t bpsRatio = 0;
+	    if(lookupApplicationSettings(settings, NULL, HSP_BPS_RATIO, &bpsRatio, NULL)) {
+	      // samlping.bps_ratio=0 turns off the behavior, falling back on global default
+	      if(bpsRatio > 0) {
+		sampling_n = adaptor->ifSpeed / bpsRatio;
+		method = HSP_BPS_RATIO;
+	      }
+	    }
+	    else {
+	      // use default bpsratio
+	      sampling_n = adaptor->ifSpeed / HSP_SPEED_SAMPLING_RATIO;
+	      if(sampling_n < HSP_SPEED_SAMPLING_MIN) {
+		sampling_n = HSP_SPEED_SAMPLING_MIN;
+	      }
+	      method = "speed_default";
 	    }
-	    method = "speed_default";
 	  }
 	}
       }
@@ -1749,6 +1760,10 @@ extern "C" {
 	      if((tok = expectIntegerRange64(sp, tok, &pc->speed_min, &pc->speed_max, 0, LLONG_MAX)) == NULL) return NO;
 	      pc->speed_set = YES;
 	      break;
+	    case HSPTOKEN_SAMPLING:
+	      if((tok = expectInteger32(sp, tok, &pc->sampling_n, 0, HSP_MAX_SAMPLING_N)) == NULL) return NO;
+	      pc->sampling_n_set = YES;
+	      break;
 	    default:
 	      unexpectedToken(sp, tok, level[depth]);
 	      return NO;
diff --git a/src/Linux/hsflowd.h b/src/Linux/hsflowd.h
index e905c28..aa2aab1 100644
--- a/src/Linux/hsflowd.h
+++ b/src/Linux/hsflowd.h
@@ -146,6 +146,7 @@ extern "C" {
 
   // For when a switch-port is configured using the default
   // (calculated) sampling-rate (based on link speed)
+#define HSP_BPS_RATIO "bps_ratio"
 #define HSP_SPEED_SAMPLING_RATIO 1000000
 #define HSP_SPEED_SAMPLING_MIN 100
 
@@ -170,6 +171,8 @@ extern "C" {
     uint64_t speed_min;
     uint64_t speed_max;
     bool speed_set;
+    uint32_t sampling_n;
+    bool sampling_n_set;
   } HSPPcap;
 
   typedef struct _HSPPort {
diff --git a/src/Linux/mod_pcap.c b/src/Linux/mod_pcap.c
index dbcd2b7..70f47fa 100644
--- a/src/Linux/mod_pcap.c
+++ b/src/Linux/mod_pcap.c
@@ -32,6 +32,7 @@ extern "C" {
     bool promisc:1;
     bool vport:1;
     bool vport_set:1;
+    bool samplingRateSet:1; // set with pcap{sampling=<n>}
     pcap_t *pcap;
     char pcap_err[PCAP_ERRBUF_SIZE];
     int n_dlts;
@@ -266,8 +267,9 @@ extern "C" {
   static void tap_open(EVMod *mod, BPFSoc *bpfs) {
     HSP_mod_PCAP *mdata = (HSP_mod_PCAP *)mod->data;
     HSP *sp = (HSP *)EVROOTDATA(mod);
-    
-    bpfs->samplingRate = lookupPacketSamplingRate(bpfs->adaptor, sp->sFlowSettings);
+
+    if(!bpfs->samplingRateSet)
+      bpfs->samplingRate = lookupPacketSamplingRate(bpfs->adaptor, sp->sFlowSettings);
     bpfs->subSamplingRate = bpfs->samplingRate;
 
     // create pcap
@@ -397,6 +399,8 @@ extern "C" {
     bpfs->promisc = pcap->promisc;
     bpfs->vport = pcap->vport;
     bpfs->vport_set = pcap->vport_set;
+    bpfs->samplingRate = pcap->sampling_n;
+    bpfs->samplingRateSet = pcap->sampling_n_set;
     tap_open(mod, bpfs);
   }