lib/sflow_sampler.c

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