commit bc4a15f91f97fbfcbfdc9dc19d73226f380bc977
author Chenbo Feng <fengc@google.com> Fri May 11 19:15:15 2018 -0700
committer Chenbo Feng <fengc@google.com> Tue May 29 20:15:36 2018 -0700
tree 8870f6e47fb4e508de2aa0ac4851c4c9bd0b141a
parent 4f6c237759e8bdc3ace937ad0eaaf9be893702da

Use a separate map to store per app stats

To avoid iterating through the eBPF map to get the total stats of a
specific uid. A new bpf map called appUidStatsMap is added to the
trafficController so that TrafficStats API can directly read that map
for per uid total stats regardless of tag, counterSet and iface
information. This could make this call more efficient and solve the
possible racing problem.

Bug: 79171384
Test: netd_unit_test, libbpf_test, netd_integration_test
Change-Id: I47a4ac3466caa729c5730a498a2de226303d6b77

libbpf/BpfNetworkStats.cpp

diff --git a/libbpf/BpfNetworkStats.cpp b/libbpf/BpfNetworkStats.cpp
index aa604ce..eafbb5e 100644
--- a/libbpf/BpfNetworkStats.cpp
+++ b/libbpf/BpfNetworkStats.cpp
@@ -42,31 +42,27 @@
 static constexpr uint32_t BPF_OPEN_FLAGS = BPF_F_RDONLY;
 
 int bpfGetUidStatsInternal(uid_t uid, Stats* stats,
-                           const BpfMap<StatsKey, StatsValue>& uidStatsMap) {
-    const auto processUidStats = [stats, uid](const StatsKey& key,
-                                              const BpfMap<StatsKey, StatsValue>& uidStatsMap) {
-        if (key.uid == uid) {
-            StatsValue statsEntry;
-            ASSIGN_OR_RETURN(statsEntry, uidStatsMap.readValue(key));
-            stats->rxPackets += statsEntry.rxPackets;
-            stats->txPackets += statsEntry.txPackets;
-            stats->rxBytes += statsEntry.rxBytes;
-            stats->txBytes += statsEntry.txBytes;
-        }
-        return netdutils::status::ok;
-    };
-    return -uidStatsMap.iterate(processUidStats).code();
+                           const BpfMap<uint32_t, StatsValue>& appUidStatsMap) {
+    auto statsEntry = appUidStatsMap.readValue(uid);
+    if (isOk(statsEntry)) {
+        stats->rxPackets = statsEntry.value().rxPackets;
+        stats->txPackets = statsEntry.value().txPackets;
+        stats->rxBytes = statsEntry.value().rxBytes;
+        stats->txBytes = statsEntry.value().txBytes;
+    }
+    return -statsEntry.status().code();
 }
 
 int bpfGetUidStats(uid_t uid, Stats* stats) {
-    BpfMap<StatsKey, StatsValue> uidStatsMap(mapRetrieve(UID_STATS_MAP_PATH, BPF_OPEN_FLAGS));
+    BpfMap<uint32_t, StatsValue> appUidStatsMap(
+        mapRetrieve(APP_UID_STATS_MAP_PATH, BPF_OPEN_FLAGS));
 
-    if (!uidStatsMap.isValid()) {
+    if (!appUidStatsMap.isValid()) {
         int ret = -errno;
-        ALOGE("Opening map fd from %s failed: %s", UID_STATS_MAP_PATH, strerror(errno));
+        ALOGE("Opening appUidStatsMap(%s) failed: %s", UID_STATS_MAP_PATH, strerror(errno));
         return ret;
     }
-    return bpfGetUidStatsInternal(uid, stats, uidStatsMap);
+    return bpfGetUidStatsInternal(uid, stats, appUidStatsMap);
 }
 
 int bpfGetIfaceStatsInternal(const char* iface, Stats* stats,