pfring: fix live device counter usage

Live device counter was in fact the number of packets seen by suricata
and not the total number of packet reported by pfring. This patch fixes
this by using counter provided by kernel instead.

Pfring kernel counter is per socket and is not cleared after read.
So to get the number of packet on the interface we can add the new
value for this thread and add it to the interface counter.

src/source-pfring.c

@@ -189,9 +189,18 @@ static inline void PfringDumpCounters(PfringThreadVars *ptv)
 {
     pfring_stat pfring_s;
     if (likely((pfring_stats(ptv->pd, &pfring_s) >= 0))) {
+        /* pfring counter is per socket and is not cleared after read.
+         * So to get the number of packet on the interface we can add
+         * the newly seen packets and drops for this thread and add it
+         * to the interface counter */
+        uint64_t th_pkts = SCPerfGetLocalCounterValue(ptv->capture_kernel_packets,
+                                                      ptv->tv->sc_perf_pca);
+        uint64_t th_drops = SCPerfGetLocalCounterValue(ptv->capture_kernel_drops,
+                                                       ptv->tv->sc_perf_pca);
+        SC_ATOMIC_ADD(ptv->livedev->pkts, pfring_s.recv - th_pkts);
+        SC_ATOMIC_ADD(ptv->livedev->drop, pfring_s.drop - th_drops);
         SCPerfCounterSetUI64(ptv->capture_kernel_packets, ptv->tv->sc_perf_pca, pfring_s.recv);
         SCPerfCounterSetUI64(ptv->capture_kernel_drops, ptv->tv->sc_perf_pca, pfring_s.drop);
-        SC_ATOMIC_SET(ptv->livedev->drop, pfring_s.drop);
     }
 }
 
@@ -211,7 +220,6 @@ static inline void PfringProcessPacket(void *user, struct pfring_pkthdr *h, Pack
 
     ptv->bytes += h->caplen;
     ptv->pkts++;
-    (void) SC_ATOMIC_ADD(ptv->livedev->pkts, 1);
     p->livedev = ptv->livedev;
 
     /* PF_RING may fail to set timestamp */