Report sparse per-iface stats using atrace.

This reports the total bytes sent and received per interface using
atrace. The totals are taken from the interface counters, rather than
the ringbuffer, since the ring buffer can run out of space.

Interfaces are only reported for interfaces which have packets
sent on them as identified by Nettrace. This helps reduce the cost
significantly for idle periods and on devices with a large number of
interfaces accumulated in the iface stats maps.

Test: TreeHugger
Change-Id: I0e6a3b11de0d1e153b9f8ebb97c338f425381a9c

service-t/native/libs/libnetworkstats/NetworkTracePoller.cpp

@@ -25,9 +25,15 @@
 #include <perfetto/tracing/platform.h>
 #include <perfetto/tracing/tracing.h>
 
+#include <unordered_map>
+#include <unordered_set>
+
+#include "netdbpf/BpfNetworkStats.h"
+
 namespace android {
 namespace bpf {
 namespace internal {
+using ::android::base::StringPrintf;
 
 void NetworkTracePoller::PollAndSchedule(perfetto::base::TaskRunner* runner,
                                          uint32_t poll_ms) {
@@ -116,6 +122,28 @@ bool NetworkTracePoller::Stop() {
   return res.ok();
 }
 
+void NetworkTracePoller::TraceIfaces(const std::vector<PacketTrace>& packets) {
+  if (packets.empty()) return;
+
+  std::unordered_set<uint32_t> uniqueIfindex;
+  for (const PacketTrace& pkt : packets) {
+    uniqueIfindex.insert(pkt.ifindex);
+  }
+
+  for (uint32_t ifindex : uniqueIfindex) {
+    char ifname[IF_NAMESIZE] = {};
+    if (if_indextoname(ifindex, ifname) != ifname) continue;
+
+    StatsValue stats = {};
+    if (bpfGetIfIndexStats(ifindex, &stats) != 0) continue;
+
+    std::string rxTrack = StringPrintf("%s [%d] Rx Bytes", ifname, ifindex);
+    std::string txTrack = StringPrintf("%s [%d] Tx Bytes", ifname, ifindex);
+    ATRACE_INT64(rxTrack.c_str(), stats.rxBytes);
+    ATRACE_INT64(txTrack.c_str(), stats.txBytes);
+  }
+}
+
 bool NetworkTracePoller::ConsumeAll() {
   std::scoped_lock<std::mutex> lock(mMutex);
   return ConsumeAllLocked();
@@ -137,6 +165,7 @@ bool NetworkTracePoller::ConsumeAllLocked() {
 
   ATRACE_INT("NetworkTracePackets", packets.size());
 
+  TraceIfaces(packets);
   mCallback(packets);
 
   return true;

service-t/native/libs/libnetworkstats/include/netdbpf/NetworkTracePoller.h

@@ -61,6 +61,11 @@ class NetworkTracePoller {
   void PollAndSchedule(perfetto::base::TaskRunner* runner, uint32_t poll_ms);
   bool ConsumeAllLocked() REQUIRES(mMutex);
 
+  // Record sparse iface stats via atrace. This queries the per-iface stats maps
+  // for any iface present in the vector of packets. This is inexact, but should
+  // have sufficient coverage given these are cumulative counters.
+  void TraceIfaces(const std::vector<PacketTrace>& packets) REQUIRES(mMutex);
+
   std::mutex mMutex;
 
   // Records the number of successfully started active sessions so that only the