ovs/lib/sflow_poller.c

/* Copyright (c) 2002-2009 InMon Corp. Licensed under the terms of either the
 *   Sun Industry Standards Source License 1.1, that is available at:
 *    http://host-sflow.sourceforge.net/sissl.html
 * or the InMon sFlow License, that is available at:
 *    http://www.inmon.com/technology/sflowlicense.txt
 */

#include "sflow_api.h"
#include "random.h"

/*_________________--------------------------__________________
  _________________    sfl_poller_init       __________________
  -----------------__________________________------------------
*/

void sfl_poller_init(SFLPoller *poller,
		     SFLAgent *agent,
		     SFLDataSource_instance *pdsi,
		     void *magic,         /* ptr to pass back in getCountersFn() */
		     getCountersFn_t getCountersFn)
{
    /* copy the dsi in case it points to poller->dsi, which we are about to clear */
    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) */
    SFLPoller *nxtPtr = poller->nxt;

    /* clear everything */
    memset(poller, 0, sizeof(*poller));

    /* restore the linked list ptr */
    poller->nxt = nxtPtr;

    /* now copy in the parameters */
    poller->agent = agent;
    poller->dsi = dsi; /* structure copy */
    poller->magic = magic;
    poller->getCountersFn = getCountersFn;
}

/*_________________--------------------------__________________
  _________________       reset              __________________
  -----------------__________________________------------------
*/

static void reset(SFLPoller *poller)
{
    SFLDataSource_instance dsi = poller->dsi;
    sfl_poller_init(poller, poller->agent, &dsi, poller->magic, poller->getCountersFn);
}

/*_________________---------------------------__________________
  _________________      MIB access           __________________
  -----------------___________________________------------------
*/
u_int32_t sfl_poller_get_sFlowCpReceiver(SFLPoller *poller) {
    return poller->sFlowCpReceiver;
}

void sfl_poller_set_sFlowCpReceiver(SFLPoller *poller, u_int32_t sFlowCpReceiver) {
    poller->sFlowCpReceiver = sFlowCpReceiver;
    if(sFlowCpReceiver == 0) reset(poller);
    else {
	/* retrieve and cache a direct pointer to my receiver */
	poller->myReceiver = sfl_agent_getReceiver(poller->agent, poller->sFlowCpReceiver);
    }
}

u_int32_t sfl_poller_get_sFlowCpInterval(SFLPoller *poller) {
    return poller->sFlowCpInterval;
}

void sfl_poller_set_sFlowCpInterval(SFLPoller *poller, u_int32_t sFlowCpInterval) {
    poller->sFlowCpInterval = sFlowCpInterval;
    if(sFlowCpInterval) {
        /* Set the countersCountdown to be a randomly selected value between 1 and
	   sFlowCpInterval. That way the counter polling will be desynchronised
	   (on a 200-port switch, polling all the counters in one second could be harmful).
	   In a large network, even this might not be ideal if time-synchroniziation
	   between devices is close and counters are always polled on second boundaries. If
	   1000 different devices all send an sFlow datagram on the same second boundary
	   it could result in an antisocial burst.
	   However when counter-samples are packed into the export datagram they do not
	   always result in that datagram being sent immediately. It is more likely that
	   a subsequent packet-sample will be the one that triggers the datagram to be sent.
	   The packet-sample events are not sychronized to any clock, so that results in
	   excellent desynchronization (http://blog.sflow.com/2009/05/measurement-traffic.html).
	   Another smoothing factor is that the tick() function called here is usually
	   driven from a fairly "soft" polling loop rather than a hard real-time event.
	*/
        poller->countersCountdown = 1 + random_range(sFlowCpInterval);
    }
    else {
        /* Setting sFlowCpInterval to 0 disables counter polling altogether.  Thanks to
	   Andy Kitchingman for spotting this ommission. */
        poller->countersCountdown = 0;
    }
}

/*_________________---------------------------------__________________
  _________________          bridge port            __________________
  -----------------_________________________________------------------
  May need a separate number to reference the local bridge port
  to get counters if it is not the same as the global ifIndex.
*/

void sfl_poller_set_bridgePort(SFLPoller *poller, u_int32_t port_no) {
    poller->bridgePort = port_no;
}

u_int32_t sfl_poller_get_bridgePort(SFLPoller *poller) {
    return poller->bridgePort;
}

/*_________________---------------------------------__________________
  _________________   sequence number reset         __________________
  -----------------_________________________________------------------
  Used to indicate a counter discontinuity
  so that the sflow collector will know to ignore the next delta.
*/
void sfl_poller_resetCountersSeqNo(SFLPoller *poller) {  poller->countersSampleSeqNo = 0; }

/*_________________---------------------------__________________
  _________________    sfl_poller_tick        __________________
  -----------------___________________________------------------
*/

void sfl_poller_tick(SFLPoller *poller)
{
    if(poller->countersCountdown == 0) return; /* counters retrieval was not enabled */
    if(poller->sFlowCpReceiver == 0) return;

    if(--poller->countersCountdown == 0) {
	if(poller->getCountersFn != NULL) {
	    /* call out for counters */
	    SFL_COUNTERS_SAMPLE_TYPE cs;
	    memset(&cs, 0, sizeof(cs));
	    poller->getCountersFn(poller->magic, poller, &cs);
	    /* this countersFn is expected to fill in some counter block elements
	       and then call sfl_poller_writeCountersSample(poller, &cs); */
	}
	/* reset the countdown */
	poller->countersCountdown = poller->sFlowCpInterval;
    }
}

/*_________________---------------------------------__________________
  _________________ sfl_poller_writeCountersSample  __________________
  -----------------_________________________________------------------
*/

void sfl_poller_writeCountersSample(SFLPoller *poller, SFL_COUNTERS_SAMPLE_TYPE *cs)
{
    /* fill in the rest of the header fields, and send to the receiver */
    cs->sequence_number = ++poller->countersSampleSeqNo;
#ifdef SFL_USE_32BIT_INDEX
    cs->ds_class = SFL_DS_CLASS(poller->dsi);
    cs->ds_index = SFL_DS_INDEX(poller->dsi);
#else
    cs->source_id = SFL_DS_DATASOURCE(poller->dsi);
#endif
    /* sent to my receiver */
    if(poller->myReceiver) sfl_receiver_writeCountersSample(poller->myReceiver, cs);
}