Merge "NetworkStatsService - xt_qtaguid non-ebpf - account stacked interface stats" am: 9273b6d9

                }

                // Traffic occurring on stacked interfaces is usually clatd.

                // UID stats are always counted on the stacked interface and never

                // on the base interface, because the packets on the base interface

                // do not actually match application sockets until they are translated.

                //

                // Interface stats are more complicated. Packets subject to BPF offload

                // never appear on the base interface and only appear on the stacked

                // interface, so to ensure those packets increment interface stats, interface

                // stats from stacked interfaces must be collected.

                // UID stats are always counted on the stacked interface and never on the base

                // interface, because the packets on the base interface do not actually match

                // application sockets (they're not IPv4) and thus the app uid is not known.

                // For receive this is obvious: packets must be translated from IPv6 to IPv4

                // before the application socket can be found.

                // For transmit: either they go through the clat daemon which by virtue of going

                // through userspace strips the original socket association during the IPv4 to

                // IPv6 translation process, or they are offloaded by eBPF, which doesn't:

                // However, on an ebpf device the accounting is done in cgroup ebpf hooks,

                // which don't trigger again post ebpf translation.

                // (as such stats accounted to the clat uid are ignored)

                //

                // Interface stats are more complicated.

                //

                // eBPF offloaded 464xlat'ed packets never hit base interface ip6tables, and thus

                // *all* statistics are collected by iptables on the stacked v4-* interface.

                //

                // Additionally for ingress all packets bound for the clat IPv6 address are dropped

                // in ip6tables raw prerouting and thus even non-offloaded packets are only

                // accounted for on the stacked interface.

                //

                // For egress, packets subject to eBPF offload never appear on the base interface

                // and only appear on the stacked interface. Thus to ensure packets increment

                // interface stats, we must collate data from stacked interfaces. For xt_qtaguid

                // (or non eBPF offloaded) TX they would appear on both, however egress interface

                // accounting is explicitly bypassed for traffic from the clat uid.

                //

                final List<LinkProperties> stackedLinks = state.linkProperties.getStackedLinks();

                for (LinkProperties stackedLink : stackedLinks) {

                    final String stackedIface = stackedLink.getInterfaceName();

                    if (stackedIface != null) {

                        if (mUseBpfTrafficStats) {

                        findOrCreateNetworkIdentitySet(mActiveIfaces, stackedIface).add(ident);

                        }

                        findOrCreateNetworkIdentitySet(mActiveUidIfaces, stackedIface).add(ident);

                        if (isMobile) {

                            mobileIfaces.add(stackedIface);