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NetworkStats - no need for xt_qtaguid clat bw fixups

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This is due to the previous addition of the ip6tables raw PREROUTING
drop rules for incoming ipv6 clat traffic pre-translation to ipv4.

Since we no longer double account, we no longer need these fixups.

Test: atest bpf_module_test clatd_test libbpf_android_test libnetdbpf_test
  netd_integration_test netd_unit_test netdutils_test
Bug: 150738490
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ia171b7797cdc99367064d0649bf1293c71579941
Merged-In: Ia171b7797cdc99367064d0649bf1293c71579941
This commit is contained in:
Maciej Żenczykowski
2019-12-24 02:50:35 -08:00
parent 7b69833232
commit cbc6c27d20
1 changed files with 26 additions and 38 deletions
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64
core/java/android/net/NetworkStats.java
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@@ -1047,22 +1047,22 @@ public final class NetworkStats implements Parcelable {
}
/**
* 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 final class NetworkStats implements Parcelable {
*/
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);
}
/**