NetworkStats - no need for xt_qtaguid clat bw fixups am: 5c9097c9e0
Change-Id: Id43e200e60590222e15327f3220de1f99e94f11c
diff --git a/core/java/android/net/NetworkStats.java b/core/java/android/net/NetworkStats.java
index b7fb280..3141320 100644
--- a/core/java/android/net/NetworkStats.java
+++ b/core/java/android/net/NetworkStats.java
@@ -1047,22 +1047,22 @@
}
/**
- * Calculate and apply adjustments to captured statistics for 464xlat traffic counted twice.
+ * Calculate and apply adjustments to captured statistics for 464xlat traffic.
*
- * <p>This mutates both base and stacked traffic stats, to account respectively for
- * double-counted traffic and IPv4/IPv6 header size difference.
+ * <p>This mutates stacked traffic stats, to account for IPv4/IPv6 header size difference.
*
- * <p>For 464xlat traffic, xt_qtaguid sees every IPv4 packet twice, once as a native IPv4
- * packet on the stacked interface, and once as translated to an IPv6 packet on the
- * base interface. For correct stats accounting on the base interface, if using xt_qtaguid,
- * every rx 464xlat packet needs to be subtracted from the root UID on the base interface
- * (http://b/12249687, http:/b/33681750), and every tx 464xlat packet which was counted onto
- * clat uid should be ignored.
+ * <p>UID stats, which are only accounted on the stacked interface, need to be increased
+ * by 20 bytes/packet to account for translation overhead.
*
- * As for eBPF, the per uid stats is collected by different hook, the rx packets on base
- * interface will not be counted. Thus, the adjustment on root uid is not needed. However, the
- * tx traffic counted in the same way xt_qtaguid does, so the traffic on clat uid still
- * needs to be ignored.
+ * <p>The potential additional overhead of 8 bytes/packet for ip fragments is ignored.
+ *
+ * <p>Interface stats need to sum traffic on both stacked and base interface because:
+ * - eBPF offloaded packets appear only on the stacked interface
+ * - Non-offloaded ingress packets appear only on the stacked interface
+ * (due to iptables raw PREROUTING drop rules)
+ * - Non-offloaded egress packets appear only on the stacked interface
+ * (due to ignoring traffic from clat daemon by uid match)
+ * (and of course the 20 bytes/packet overhead needs to be applied to stacked interface stats)
*
* <p>This method will behave fine if {@code stackedIfaces} is an non-synchronized but add-only
* {@code ConcurrentHashMap}
@@ -1074,46 +1074,34 @@
*/
public static void apply464xlatAdjustments(NetworkStats baseTraffic,
NetworkStats stackedTraffic, Map<String, String> stackedIfaces, boolean useBpfStats) {
- // Total 464xlat traffic to subtract from uid 0 on all base interfaces.
- // stackedIfaces may grow afterwards, but NetworkStats will just be resized automatically.
- final NetworkStats adjustments = new NetworkStats(0, stackedIfaces.size());
-
// For recycling
Entry entry = null;
- Entry adjust = new NetworkStats.Entry(IFACE_ALL, 0, 0, 0, 0, 0, 0, 0L, 0L, 0L, 0L, 0L);
-
for (int i = 0; i < stackedTraffic.size; i++) {
entry = stackedTraffic.getValues(i, entry);
- if (entry.iface == null || !entry.iface.startsWith(CLATD_INTERFACE_PREFIX)) {
- continue;
- }
- final String baseIface = stackedIfaces.get(entry.iface);
- if (baseIface == null) {
- continue;
- }
- // Subtract xt_qtaguid 464lat rx traffic seen for the root UID on the current base
- // interface. As for eBPF, the per uid stats is collected by different hook, the rx
- // packets on base interface will not be counted.
- adjust.iface = baseIface;
- if (!useBpfStats) {
- adjust.rxBytes = -(entry.rxBytes + entry.rxPackets * IPV4V6_HEADER_DELTA);
- adjust.rxPackets = -entry.rxPackets;
- }
- adjustments.combineValues(adjust);
+ if (entry == null) continue;
+ if (entry.iface == null) continue;
+ if (!entry.iface.startsWith(CLATD_INTERFACE_PREFIX)) continue;
// For 464xlat traffic, per uid stats only counts the bytes of the native IPv4 packet
// sent on the stacked interface with prefix "v4-" and drops the IPv6 header size after
// unwrapping. To account correctly for on-the-wire traffic, add the 20 additional bytes
// difference for all packets (http://b/12249687, http:/b/33681750).
+ //
+ // Note: this doesn't account for LRO/GRO/GSO/TSO (ie. >mtu) traffic correctly, nor
+ // does it correctly account for the 8 extra bytes in the IPv6 fragmentation header.
+ //
+ // While the ebpf code path does try to simulate proper post segmentation packet
+ // counts, we have nothing of the sort of xt_qtaguid stats.
entry.rxBytes += entry.rxPackets * IPV4V6_HEADER_DELTA;
entry.txBytes += entry.txPackets * IPV4V6_HEADER_DELTA;
stackedTraffic.setValues(i, entry);
}
- // Traffic on clat uid is v6 tx traffic that is already counted with app uid on the stacked
- // v4 interface, so it needs to be removed to avoid double-counting.
+ // Theoretically there should be no traffic accounted to the clat daemon's uid:
+ // see ebpf program 'netd.c's early returns
+ // and iptables '-m owner --uid-owner clat -j RETURN' rules prior to accounting
+ // TODO: remove this - should definitely be safe once ebpf only.
baseTraffic.removeUids(new int[] {CLAT_UID});
- baseTraffic.combineAllValues(adjustments);
}
/**