Add InMon's sFlow Agent library to the build system.

The C source and header files added in this commit is covered under the
InMon sFlow license at http://www.inmon.com/technology/sflowlicense.txt

The library requires -Wno-unused to compile without warnings, so this
commit adds that for building the sFlow code only.  Automake can only
change compiler flags on a per-library or per-program basis, so sFlow
is built as a separate library.

The library will be used in upcoming commits.

1 files changed, 183 insertions, 0 deletions

diff --git a/lib/sflow_sampler.c b/lib/sflow_sampler.c
new file mode 100644
index 000000000..759b5a22c
--- /dev/null
+++ b/lib/sflow_sampler.c
@@ -0,0 +1,183 @@
+/* Copyright (c) 2002-2009 InMon Corp. Licensed under the terms of the InMon sFlow licence: */
+/* http://www.inmon.com/technology/sflowlicense.txt */
+
+#include "sflow_api.h"
+
+
+/*_________________--------------------------__________________
+  _________________   sfl_sampler_init       __________________
+  -----------------__________________________------------------
+*/
+
+void sfl_sampler_init(SFLSampler *sampler, SFLAgent *agent, SFLDataSource_instance *pdsi)
+{
+    /* copy the dsi in case it points to sampler->dsi, which we are about to clear.
+       (Thanks to Jagjit Choudray of Force 10 Networks for pointing out this bug) */
+    SFLDataSource_instance dsi = *pdsi;
+
+    /* preserve the *nxt pointer too, in case we are resetting this poller and it is
+       already part of the agent's linked list (thanks to Matt Woodly for pointing this out) */
+    SFLSampler *nxtPtr = sampler->nxt;
+  
+    /* clear everything */
+    memset(sampler, 0, sizeof(*sampler));
+  
+    /* restore the linked list ptr */
+    sampler->nxt = nxtPtr;
+  
+    /* now copy in the parameters */
+    sampler->agent = agent;
+    sampler->dsi = dsi;
+  
+    /* set defaults */
+    sampler->sFlowFsMaximumHeaderSize = SFL_DEFAULT_HEADER_SIZE;
+    sampler->sFlowFsPacketSamplingRate = SFL_DEFAULT_SAMPLING_RATE;
+}
+
+/*_________________--------------------------__________________
+  _________________       reset              __________________
+  -----------------__________________________------------------
+*/
+
+static void reset(SFLSampler *sampler)
+{
+    SFLDataSource_instance dsi = sampler->dsi;
+    sfl_sampler_init(sampler, sampler->agent, &dsi);
+}
+
+/*_________________---------------------------__________________
+  _________________      MIB access           __________________
+  -----------------___________________________------------------
+*/
+u_int32_t sfl_sampler_get_sFlowFsReceiver(SFLSampler *sampler) {
+    return sampler->sFlowFsReceiver;
+}
+void sfl_sampler_set_sFlowFsReceiver(SFLSampler *sampler, u_int32_t sFlowFsReceiver) {
+    sampler->sFlowFsReceiver = sFlowFsReceiver;
+    if(sFlowFsReceiver == 0) reset(sampler);
+    else {
+	/* retrieve and cache a direct pointer to my receiver */
+	sampler->myReceiver = sfl_agent_getReceiver(sampler->agent, sampler->sFlowFsReceiver);
+    }
+}
+u_int32_t sfl_sampler_get_sFlowFsPacketSamplingRate(SFLSampler *sampler) {
+    return sampler->sFlowFsPacketSamplingRate;
+}
+void sfl_sampler_set_sFlowFsPacketSamplingRate(SFLSampler *sampler, u_int32_t sFlowFsPacketSamplingRate) {
+    sampler->sFlowFsPacketSamplingRate = sFlowFsPacketSamplingRate;
+}
+u_int32_t sfl_sampler_get_sFlowFsMaximumHeaderSize(SFLSampler *sampler) {
+    return sampler->sFlowFsMaximumHeaderSize;
+}
+void sfl_sampler_set_sFlowFsMaximumHeaderSize(SFLSampler *sampler, u_int32_t sFlowFsMaximumHeaderSize) {
+    sampler->sFlowFsMaximumHeaderSize = sFlowFsMaximumHeaderSize;
+}
+
+/* call this to set a maximum samples-per-second threshold. If the sampler reaches this
+   threshold it will automatically back off the sampling rate. A value of 0 disables the
+   mechanism */
+void sfl_sampler_set_backoffThreshold(SFLSampler *sampler, u_int32_t samplesPerSecond) {
+    sampler->backoffThreshold = samplesPerSecond;
+}
+u_int32_t sfl_sampler_get_backoffThreshold(SFLSampler *sampler) {
+    return sampler->backoffThreshold;
+}
+u_int32_t sfl_sampler_get_samplesLastTick(SFLSampler *sampler) {
+    return sampler->samplesLastTick;
+}
+
+/*_________________---------------------------------__________________
+  _________________   sequence number reset         __________________
+  -----------------_________________________________------------------
+  Used by the agent to indicate a samplePool discontinuity
+  so that the sflow collector will know to ignore the next delta.
+*/
+void sfl_sampler_resetFlowSeqNo(SFLSampler *sampler) { sampler->flowSampleSeqNo = 0; }
+
+
+/*_________________---------------------------__________________
+  _________________    sfl_sampler_tick       __________________
+  -----------------___________________________------------------
+*/
+
+void sfl_sampler_tick(SFLSampler *sampler, time_t now)
+{
+    if(sampler->backoffThreshold && sampler->samplesThisTick > sampler->backoffThreshold) {
+	/* automatic backoff.  If using hardware sampling then this is where you have to
+	 * call out to change the sampling rate and make sure that any other registers/variables
+	 * that hold this value are updated.
+	 */
+	sampler->sFlowFsPacketSamplingRate *= 2;
+    }
+    sampler->samplesLastTick = sampler->samplesThisTick;
+    sampler->samplesThisTick = 0;
+}
+
+
+
+/*_________________------------------------------__________________
+  _________________ sfl_sampler_writeFlowSample  __________________
+  -----------------______________________________------------------
+*/
+
+void sfl_sampler_writeFlowSample(SFLSampler *sampler, SFL_FLOW_SAMPLE_TYPE *fs)
+{
+    if(fs == NULL) return;
+    sampler->samplesThisTick++;
+    /* increment the sequence number */
+    fs->sequence_number = ++sampler->flowSampleSeqNo;
+    /* copy the other header fields in */
+#ifdef SFL_USE_32BIT_INDEX
+    fs->ds_class = SFL_DS_CLASS(sampler->dsi);
+    fs->ds_index = SFL_DS_INDEX(sampler->dsi);
+#else
+    fs->source_id = SFL_DS_DATASOURCE(sampler->dsi);
+#endif
+    /* the sampling rate may have been set already. */
+    if(fs->sampling_rate == 0) fs->sampling_rate = sampler->sFlowFsPacketSamplingRate;
+    /* the samplePool may be maintained upstream too. */
+    if( fs->sample_pool == 0) fs->sample_pool = sampler->samplePool;
+    /* sent to my receiver */
+    if(sampler->myReceiver) sfl_receiver_writeFlowSample(sampler->myReceiver, fs);
+}
+
+#ifdef SFLOW_SOFTWARE_SAMPLING
+
+/* ================== software sampling ========================*/
+
+/*_________________---------------------------__________________
+  _________________     nextRandomSkip        __________________
+  -----------------___________________________------------------
+*/
+
+inline static u_int32_t nextRandomSkip(u_int32_t mean)
+{
+    if(mean == 0 || mean == 1) return 1;
+    return ((random() % ((2 * mean) - 1)) + 1);
+} 
+
+/*_________________---------------------------__________________
+  _________________  sfl_sampler_takeSample   __________________
+  -----------------___________________________------------------
+*/
+
+int sfl_sampler_takeSample(SFLSampler *sampler)
+{
+    if(sampler->skip == 0) {
+	/* first time - seed the random number generator */
+	srandom(SFL_DS_INDEX(sampler->dsi));
+	sampler->skip = nextRandomSkip(sampler->sFlowFsPacketSamplingRate);
+    }
+
+    /* increment the samplePool */
+    sampler->samplePool++;
+
+    if(--sampler->skip == 0) {
+	/* reached zero. Set the next skip and return true. */
+	sampler->skip = nextRandomSkip(sampler->sFlowFsPacketSamplingRate);
+	return 1;
+    }
+    return 0;
+}
+
+#endif /* SFLOW_SOFTWARE_SAMPLING */