lib/sflow_sampler.c

   1 /* Copyright (c) 2002-2009 InMon Corp. Licensed under the terms of either the
   2  *   Sun Industry Standards Source License 1.1, that is available at:
   3  *    http://host-sflow.sourceforge.net/sissl.html
   4  * or the InMon sFlow License, that is available at:
   5  *    http://www.inmon.com/technology/sflowlicense.txt
   6  */
   7
   8 #include "sflow_api.h"
   9
  10
  11 /*_________________--------------------------__________________
  12   _________________   sfl_sampler_init       __________________
  13   -----------------__________________________------------------
  14 */
  15
  16 void sfl_sampler_init(SFLSampler *sampler, SFLAgent *agent, SFLDataSource_instance *pdsi)
  17 {
  18     /* copy the dsi in case it points to sampler->dsi, which we are about to clear.
  19        (Thanks to Jagjit Choudray of Force 10 Networks for pointing out this bug) */
  20     SFLDataSource_instance dsi = *pdsi;
  21
  22     /* preserve the *nxt pointer too, in case we are resetting this poller and it is
  23        already part of the agent's linked list (thanks to Matt Woodly for pointing this out,
  24        and to Andy Kitchingman for pointing out that it applies to the hash_nxt ptr too) */
  25     SFLSampler *nxtPtr = sampler->nxt;
  26     SFLSampler *hashPtr = sampler->hash_nxt;
  27
  28     /* clear everything */
  29     memset(sampler, 0, sizeof(*sampler));
  30
  31     /* restore the linked list and hash-table ptr */
  32     sampler->nxt = nxtPtr;
  33     sampler->hash_nxt = hashPtr;
  34
  35     /* now copy in the parameters */
  36     sampler->agent = agent;
  37     sampler->dsi = dsi;
  38
  39     /* set defaults */
  40     sampler->sFlowFsMaximumHeaderSize = SFL_DEFAULT_HEADER_SIZE;
  41     sampler->sFlowFsPacketSamplingRate = SFL_DEFAULT_SAMPLING_RATE;
  42 }
  43
  44 /*_________________--------------------------__________________
  45   _________________       reset              __________________
  46   -----------------__________________________------------------
  47 */
  48
  49 static void reset(SFLSampler *sampler)
  50 {
  51     SFLDataSource_instance dsi = sampler->dsi;
  52     sfl_sampler_init(sampler, sampler->agent, &dsi);
  53 }
  54
  55 /*_________________---------------------------__________________
  56   _________________      MIB access           __________________
  57   -----------------___________________________------------------
  58 */
  59 u_int32_t sfl_sampler_get_sFlowFsReceiver(SFLSampler *sampler) {
  60     return sampler->sFlowFsReceiver;
  61 }
  62 void sfl_sampler_set_sFlowFsReceiver(SFLSampler *sampler, u_int32_t sFlowFsReceiver) {
  63     sampler->sFlowFsReceiver = sFlowFsReceiver;
  64     if(sFlowFsReceiver == 0) reset(sampler);
  65     else {
  66         /* retrieve and cache a direct pointer to my receiver */
  67         sampler->myReceiver = sfl_agent_getReceiver(sampler->agent, sampler->sFlowFsReceiver);
  68     }
  69 }
  70 u_int32_t sfl_sampler_get_sFlowFsPacketSamplingRate(SFLSampler *sampler) {
  71     return sampler->sFlowFsPacketSamplingRate;
  72 }
  73 void sfl_sampler_set_sFlowFsPacketSamplingRate(SFLSampler *sampler, u_int32_t sFlowFsPacketSamplingRate) {
  74     sampler->sFlowFsPacketSamplingRate = sFlowFsPacketSamplingRate;
  75 }
  76 u_int32_t sfl_sampler_get_sFlowFsMaximumHeaderSize(SFLSampler *sampler) {
  77     return sampler->sFlowFsMaximumHeaderSize;
  78 }
  79 void sfl_sampler_set_sFlowFsMaximumHeaderSize(SFLSampler *sampler, u_int32_t sFlowFsMaximumHeaderSize) {
  80     sampler->sFlowFsMaximumHeaderSize = sFlowFsMaximumHeaderSize;
  81 }
  82
  83 /* call this to set a maximum samples-per-second threshold. If the sampler reaches this
  84    threshold it will automatically back off the sampling rate. A value of 0 disables the
  85    mechanism */
  86 void sfl_sampler_set_backoffThreshold(SFLSampler *sampler, u_int32_t samplesPerSecond) {
  87     sampler->backoffThreshold = samplesPerSecond;
  88 }
  89 u_int32_t sfl_sampler_get_backoffThreshold(SFLSampler *sampler) {
  90     return sampler->backoffThreshold;
  91 }
  92 u_int32_t sfl_sampler_get_samplesLastTick(SFLSampler *sampler) {
  93     return sampler->samplesLastTick;
  94 }
  95
  96 /*_________________---------------------------------__________________
  97   _________________   sequence number reset         __________________
  98   -----------------_________________________________------------------
  99   Used by the agent to indicate a samplePool discontinuity
 100   so that the sflow collector will know to ignore the next delta.
 101 */
 102 void sfl_sampler_resetFlowSeqNo(SFLSampler *sampler) { sampler->flowSampleSeqNo = 0; }
 103
 104
 105 /*_________________---------------------------__________________
 106   _________________    sfl_sampler_tick       __________________
 107   -----------------___________________________------------------
 108 */
 109
 110 void sfl_sampler_tick(SFLSampler *sampler, time_t now)
 111 {
 112     if(sampler->backoffThreshold && sampler->samplesThisTick > sampler->backoffThreshold) {
 113         /* automatic backoff.  If using hardware sampling then this is where you have to
 114          * call out to change the sampling rate and make sure that any other registers/variables
 115          * that hold this value are updated.
 116          */
 117         sampler->sFlowFsPacketSamplingRate *= 2;
 118     }
 119     sampler->samplesLastTick = sampler->samplesThisTick;
 120     sampler->samplesThisTick = 0;
 121 }
 122
 123
 124
 125 /*_________________------------------------------__________________
 126   _________________ sfl_sampler_writeFlowSample  __________________
 127   -----------------______________________________------------------
 128 */
 129
 130 void sfl_sampler_writeFlowSample(SFLSampler *sampler, SFL_FLOW_SAMPLE_TYPE *fs)
 131 {
 132     if(fs == NULL) return;
 133     sampler->samplesThisTick++;
 134     /* increment the sequence number */
 135     fs->sequence_number = ++sampler->flowSampleSeqNo;
 136     /* copy the other header fields in */
 137 #ifdef SFL_USE_32BIT_INDEX
 138     fs->ds_class = SFL_DS_CLASS(sampler->dsi);
 139     fs->ds_index = SFL_DS_INDEX(sampler->dsi);
 140 #else
 141     fs->source_id = SFL_DS_DATASOURCE(sampler->dsi);
 142 #endif
 143     /* the sampling rate may have been set already. */
 144     if(fs->sampling_rate == 0) fs->sampling_rate = sampler->sFlowFsPacketSamplingRate;
 145     /* the samplePool may be maintained upstream too. */
 146     if( fs->sample_pool == 0) fs->sample_pool = sampler->samplePool;
 147     /* sent to my receiver */
 148     if(sampler->myReceiver) sfl_receiver_writeFlowSample(sampler->myReceiver, fs);
 149 }
 150
 151 #ifdef SFLOW_SOFTWARE_SAMPLING
 152
 153 /* ================== software sampling ========================*/
 154
 155 /*_________________---------------------------__________________
 156   _________________     nextRandomSkip        __________________
 157   -----------------___________________________------------------
 158 */
 159
 160 inline static u_int32_t nextRandomSkip(u_int32_t mean)
 161 {
 162     if(mean == 0 || mean == 1) return 1;
 163     return ((random() % ((2 * mean) - 1)) + 1);
 164 }
 165
 166 /*_________________---------------------------__________________
 167   _________________  sfl_sampler_takeSample   __________________
 168   -----------------___________________________------------------
 169 */
 170
 171 int sfl_sampler_takeSample(SFLSampler *sampler)
 172 {
 173     if(sampler->skip == 0) {
 174         /* first time - seed the random number generator */
 175         srandom(SFL_DS_INDEX(sampler->dsi));
 176         sampler->skip = nextRandomSkip(sampler->sFlowFsPacketSamplingRate);
 177     }
 178
 179     /* increment the samplePool */
 180     sampler->samplePool++;
 181
 182     if(--sampler->skip == 0) {
 183         /* reached zero. Set the next skip and return true. */
 184         sampler->skip = nextRandomSkip(sampler->sFlowFsPacketSamplingRate);
 185         return 1;
 186     }
 187     return 0;
 188 }
 189
 190 #endif /* SFLOW_SOFTWARE_SAMPLING */