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android_frameworks_base/services/common_time/common_time_server.cpp
John Grossman 8100960892 am e1d6c080: Make common_time more deferential when coming out of networkless mode. 
* commit 'e1d6c080f0b1769637d742e51cc22167c7af12bb':
  Make common_time more deferential when coming out of networkless mode.
2012-04-09 17:00:24 -07:00

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/*
* Copyright (C) 2012 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* A service that exchanges time synchronization information between
* a master that defines a timeline and clients that follow the timeline.
*/
#define LOG_TAG "common_time"
#include <utils/Log.h>
#include <arpa/inet.h>
#include <assert.h>
#include <fcntl.h>
#include <linux/if_ether.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <netinet/ip.h>
#include <poll.h>
#include <stdio.h>
#include <sys/eventfd.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <common_time/local_clock.h>
#include <binder/IPCThreadState.h>
#include <binder/ProcessState.h>
#include <utils/Timers.h>
#include "common_clock_service.h"
#include "common_time_config_service.h"
#include "common_time_server.h"
#include "common_time_server_packets.h"
#include "clock_recovery.h"
#include "common_clock.h"
#define MAX_INT ((int)0x7FFFFFFF)
namespace android {
const char* CommonTimeServer::kDefaultMasterElectionAddr = "239.195.128.88";
const uint16_t CommonTimeServer::kDefaultMasterElectionPort = 8887;
const uint64_t CommonTimeServer::kDefaultSyncGroupID = 0;
const uint8_t CommonTimeServer::kDefaultMasterPriority = 1;
const uint32_t CommonTimeServer::kDefaultMasterAnnounceIntervalMs = 10000;
const uint32_t CommonTimeServer::kDefaultSyncRequestIntervalMs = 1000;
const uint32_t CommonTimeServer::kDefaultPanicThresholdUsec = 50000;
const bool CommonTimeServer::kDefaultAutoDisable = true;
const int CommonTimeServer::kSetupRetryTimeoutMs = 30000;
const int64_t CommonTimeServer::kNoGoodDataPanicThresholdUsec = 600000000ll;
const uint32_t CommonTimeServer::kRTTDiscardPanicThreshMultiplier = 5;
// timeout value representing an infinite timeout
const int CommonTimeServer::kInfiniteTimeout = -1;
/*** Initial state constants ***/
// number of WhoIsMaster attempts sent before giving up
const int CommonTimeServer::kInitial_NumWhoIsMasterRetries = 6;
// timeout used when waiting for a response to a WhoIsMaster request
const int CommonTimeServer::kInitial_WhoIsMasterTimeoutMs = 500;
/*** Client state constants ***/
// number of sync requests that can fail before a client assumes its master
// is dead
const int CommonTimeServer::kClient_NumSyncRequestRetries = 10;
/*** Master state constants ***/
/*** Ronin state constants ***/
// number of WhoIsMaster attempts sent before declaring ourselves master
const int CommonTimeServer::kRonin_NumWhoIsMasterRetries = 20;
// timeout used when waiting for a response to a WhoIsMaster request
const int CommonTimeServer::kRonin_WhoIsMasterTimeoutMs = 500;
/*** WaitForElection state constants ***/
// how long do we wait for an announcement from a master before
// trying another election?
const int CommonTimeServer::kWaitForElection_TimeoutMs = 12500;
CommonTimeServer::CommonTimeServer()
: Thread(false)
, mState(ICommonClock::STATE_INITIAL)
, mClockRecovery(&mLocalClock, &mCommonClock)
, mSocket(-1)
, mLastPacketRxLocalTime(0)
, mTimelineID(ICommonClock::kInvalidTimelineID)
, mClockSynced(false)
, mCommonClockHasClients(false)
, mInitial_WhoIsMasterRequestTimeouts(0)
, mClient_MasterDeviceID(0)
, mClient_MasterDevicePriority(0)
, mRonin_WhoIsMasterRequestTimeouts(0) {
// zero out sync stats
resetSyncStats();
// Setup the master election endpoint to use the default.
struct sockaddr_in* meep =
reinterpret_cast<struct sockaddr_in*>(&mMasterElectionEP);
memset(&mMasterElectionEP, 0, sizeof(mMasterElectionEP));
inet_aton(kDefaultMasterElectionAddr, &meep->sin_addr);
meep->sin_family = AF_INET;
meep->sin_port = htons(kDefaultMasterElectionPort);
// Zero out the master endpoint.
memset(&mMasterEP, 0, sizeof(mMasterEP));
mMasterEPValid = false;
mBindIfaceValid = false;
setForceLowPriority(false);
// Set all remaining configuration parameters to their defaults.
mDeviceID = 0;
mSyncGroupID = kDefaultSyncGroupID;
mMasterPriority = kDefaultMasterPriority;
mMasterAnnounceIntervalMs = kDefaultMasterAnnounceIntervalMs;
mSyncRequestIntervalMs = kDefaultSyncRequestIntervalMs;
mPanicThresholdUsec = kDefaultPanicThresholdUsec;
mAutoDisable = kDefaultAutoDisable;
// Create the eventfd we will use to signal our thread to wake up when
// needed.
mWakeupThreadFD = eventfd(0, EFD_NONBLOCK);
// seed the random number generator (used to generated timeline IDs)
srand48(static_cast<unsigned int>(systemTime()));
}
CommonTimeServer::~CommonTimeServer() {
shutdownThread();
// No need to grab the lock here. We are in the destructor; if the the user
// has a thread in any of the APIs while the destructor is being called,
// there is a threading problem a the application level we cannot reasonably
// do anything about.
cleanupSocket_l();
if (mWakeupThreadFD >= 0) {
close(mWakeupThreadFD);
mWakeupThreadFD = -1;
}
}
bool CommonTimeServer::startServices() {
// start the ICommonClock service
mICommonClock = CommonClockService::instantiate(*this);
if (mICommonClock == NULL)
return false;
// start the ICommonTimeConfig service
mICommonTimeConfig = CommonTimeConfigService::instantiate(*this);
if (mICommonTimeConfig == NULL)
return false;
return true;
}
bool CommonTimeServer::threadLoop() {
// Register our service interfaces.
if (!startServices())
return false;
// Hold the lock while we are in the main thread loop. It will release the
// lock when it blocks, and hold the lock at all other times.
mLock.lock();
runStateMachine_l();
mLock.unlock();
IPCThreadState::self()->stopProcess();
return false;
}
bool CommonTimeServer::runStateMachine_l() {
if (!mLocalClock.initCheck())
return false;
if (!mCommonClock.init(mLocalClock.getLocalFreq()))
return false;
// Enter the initial state.
becomeInitial("startup");
// run the state machine
while (!exitPending()) {
struct pollfd pfds[2];
int rc;
int eventCnt = 0;
int64_t wakeupTime;
// We are always interested in our wakeup FD.
pfds[eventCnt].fd = mWakeupThreadFD;
pfds[eventCnt].events = POLLIN;
pfds[eventCnt].revents = 0;
eventCnt++;
// If we have a valid socket, then we are interested in what it has to
// say as well.
if (mSocket >= 0) {
pfds[eventCnt].fd = mSocket;
pfds[eventCnt].events = POLLIN;
pfds[eventCnt].revents = 0;
eventCnt++;
}
// Note, we were holding mLock when this function was called. We
// release it only while we are blocking and hold it at all other times.
mLock.unlock();
rc = poll(pfds, eventCnt, mCurTimeout.msecTillTimeout());
wakeupTime = mLocalClock.getLocalTime();
mLock.lock();
// Is it time to shutdown? If so, don't hesitate... just do it.
if (exitPending())
break;
// Did the poll fail? This should never happen and is fatal if it does.
if (rc < 0) {
ALOGE("%s:%d poll failed", __PRETTY_FUNCTION__, __LINE__);
return false;
}
if (rc == 0)
mCurTimeout.setTimeout(kInfiniteTimeout);
// Were we woken up on purpose? If so, clear the eventfd with a read.
if (pfds[0].revents)
clearPendingWakeupEvents_l();
// Is out bind address dirty? If so, clean up our socket (if any).
// Alternatively, do we have an active socket but should be auto
// disabled? If so, release the socket and enter the proper sync state.
bool droppedSocket = false;
if (mBindIfaceDirty || ((mSocket >= 0) && shouldAutoDisable())) {
cleanupSocket_l();
mBindIfaceDirty = false;
droppedSocket = true;
}
// Do we not have a socket but should have one? If so, try to set one
// up.
if ((mSocket < 0) && mBindIfaceValid && !shouldAutoDisable()) {
if (setupSocket_l()) {
// Success! We are now joining a new network (either coming
// from no network, or coming from a potentially different
// network). Force our priority to be lower so that we defer to
// any other masters which may already be on the network we are
// joining. Later, when we enter either the client or the
// master state, we will clear this flag and go back to our
// normal election priority.
setForceLowPriority(true);
switch (mState) {
// If we were in initial (whether we had a immediately
// before this network or not) we want to simply reset the
// system and start again. Forcing a transition from
// INITIAL to INITIAL should do the job.
case CommonClockService::STATE_INITIAL:
becomeInitial("bound interface");
break;
// If we were in the master state, then either we were the
// master in a no-network situation, or we were the master
// of a different network and have moved to a new interface.
// In either case, immediately transition to Ronin at low
// priority. If there is no one in the network we just
// joined, we will become master soon enough. If there is,
// we want to be certain to defer master status to the
// existing timeline currently running on the network.
//
case CommonClockService::STATE_MASTER:
becomeRonin("leaving networkless mode");
break;
// If we were in any other state (CLIENT, RONIN, or
// WAIT_FOR_ELECTION) then we must be moving from one
// network to another. We have lost our old master;
// transition to RONIN in an attempt to find a new master.
// If there are none out there, we will just assume
// responsibility for the timeline we used to be a client
// of.
default:
becomeRonin("bound interface");
break;
}
} else {
// That's odd... we failed to set up our socket. This could be
// due to some transient network change which will work itself
// out shortly; schedule a retry attempt in the near future.
mCurTimeout.setTimeout(kSetupRetryTimeoutMs);
}
// One way or the other, we don't have any data to process at this
// point (since we just tried to bulid a new socket). Loop back
// around and wait for the next thing to do.
continue;
} else if (droppedSocket) {
// We just lost our socket, and for whatever reason (either no
// config, or auto disable engaged) we are not supposed to rebuild
// one at this time. We are not going to rebuild our socket until
// something about our config/auto-disabled status changes, so we
// are basically in network-less mode. If we are already in either
// INITIAL or MASTER, just stay there until something changes. If
// we are in any other state (CLIENT, RONIN or WAIT_FOR_ELECTION),
// then transition to either INITIAL or MASTER depending on whether
// or not our timeline is valid.
ALOGI("Entering networkless mode interface is %s, "
"shouldAutoDisable = %s",
mBindIfaceValid ? "valid" : "invalid",
shouldAutoDisable() ? "true" : "false");
if ((mState != ICommonClock::STATE_INITIAL) &&
(mState != ICommonClock::STATE_MASTER)) {
if (mTimelineID == ICommonClock::kInvalidTimelineID)
becomeInitial("network-less mode");
else
becomeMaster("network-less mode");
}
continue;
}
// Did we wakeup with no signalled events across all of our FDs? If so,
// we must have hit our timeout.
if (rc == 0) {
if (!handleTimeout())
ALOGE("handleTimeout failed");
continue;
}
// Does our socket have data for us (assuming we still have one, we
// may have RXed a packet at the same time as a config change telling us
// to shut our socket down)? If so, process its data.
if ((mSocket >= 0) && (eventCnt > 1) && (pfds[1].revents)) {
mLastPacketRxLocalTime = wakeupTime;
if (!handlePacket())
ALOGE("handlePacket failed");
}
}
cleanupSocket_l();
return true;
}
void CommonTimeServer::clearPendingWakeupEvents_l() {
int64_t tmp;
read(mWakeupThreadFD, &tmp, sizeof(tmp));
}
void CommonTimeServer::wakeupThread_l() {
int64_t tmp = 1;
write(mWakeupThreadFD, &tmp, sizeof(tmp));
}
void CommonTimeServer::cleanupSocket_l() {
if (mSocket >= 0) {
close(mSocket);
mSocket = -1;
}
}
void CommonTimeServer::shutdownThread() {
// Flag the work thread for shutdown.
this->requestExit();
// Signal the thread in case its sleeping.
mLock.lock();
wakeupThread_l();
mLock.unlock();
// Wait for the thread to exit.
this->join();
}
bool CommonTimeServer::setupSocket_l() {
int rc;
bool ret_val = false;
struct sockaddr_in* ipv4_addr = NULL;
char masterElectionEPStr[64];
const int one = 1;
// This should never be needed, but if we happened to have an old socket
// lying around, be sure to not leak it before proceeding.
cleanupSocket_l();
// If we don't have a valid endpoint to bind to, then how did we get here in
// the first place? Regardless, we know that we are going to fail to bind,
// so don't even try.
if (!mBindIfaceValid)
return false;
sockaddrToString(mMasterElectionEP, true, masterElectionEPStr,
sizeof(masterElectionEPStr));
ALOGI("Building socket :: bind = %s master election = %s",
mBindIface.string(), masterElectionEPStr);
// TODO: add proper support for IPv6. Right now, we block IPv6 addresses at
// the configuration interface level.
if (AF_INET != mMasterElectionEP.ss_family) {
ALOGW("TODO: add proper IPv6 support");
goto bailout;
}
// open a UDP socket for the timeline serivce
mSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (mSocket < 0) {
ALOGE("Failed to create socket (errno = %d)", errno);
goto bailout;
}
// Bind to the selected interface using Linux's spiffy SO_BINDTODEVICE.
struct ifreq ifr;
memset(&ifr, 0, sizeof(ifr));
snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "%s", mBindIface.string());
ifr.ifr_name[sizeof(ifr.ifr_name) - 1] = 0;
rc = setsockopt(mSocket, SOL_SOCKET, SO_BINDTODEVICE,
(void *)&ifr, sizeof(ifr));
if (rc) {
ALOGE("Failed to bind socket at to interface %s (errno = %d)",
ifr.ifr_name, errno);
goto bailout;
}
// Bind our socket to INADDR_ANY and the master election port. The
// interface binding we made using SO_BINDTODEVICE should limit us to
// traffic only on the interface we are interested in. We need to bind to
// INADDR_ANY and the specific master election port in order to be able to
// receive both unicast traffic and master election multicast traffic with
// just a single socket.
struct sockaddr_in bindAddr;
ipv4_addr = reinterpret_cast<struct sockaddr_in*>(&mMasterElectionEP);
memcpy(&bindAddr, ipv4_addr, sizeof(bindAddr));
bindAddr.sin_addr.s_addr = INADDR_ANY;
rc = bind(mSocket,
reinterpret_cast<const sockaddr *>(&bindAddr),
sizeof(bindAddr));
if (rc) {
ALOGE("Failed to bind socket to port %hu (errno = %d)",
ntohs(bindAddr.sin_port), errno);
goto bailout;
}
if (0xE0000000 == (ntohl(ipv4_addr->sin_addr.s_addr) & 0xF0000000)) {
// If our master election endpoint is a multicast address, be sure to join
// the multicast group.
struct ip_mreq mreq;
mreq.imr_multiaddr = ipv4_addr->sin_addr;
mreq.imr_interface.s_addr = htonl(INADDR_ANY);
rc = setsockopt(mSocket, IPPROTO_IP, IP_ADD_MEMBERSHIP,
&mreq, sizeof(mreq));
if (rc == -1) {
ALOGE("Failed to join multicast group at %s. (errno = %d)",
masterElectionEPStr, errno);
goto bailout;
}
// disable loopback of multicast packets
const int zero = 0;
rc = setsockopt(mSocket, IPPROTO_IP, IP_MULTICAST_LOOP,
&zero, sizeof(zero));
if (rc == -1) {
ALOGE("Failed to disable multicast loopback (errno = %d)", errno);
goto bailout;
}
} else
if (ntohl(ipv4_addr->sin_addr.s_addr) != 0xFFFFFFFF) {
// If the master election address is neither broadcast, nor multicast,
// then we are misconfigured. The config API layer should prevent this
// from ever happening.
goto bailout;
}
// Set the TTL of sent packets to 1. (Time protocol sync should never leave
// the local subnet)
rc = setsockopt(mSocket, IPPROTO_IP, IP_TTL, &one, sizeof(one));
if (rc == -1) {
ALOGE("Failed to set TTL to %d (errno = %d)", one, errno);
goto bailout;
}
// get the device's unique ID
if (!assignDeviceID())
goto bailout;
ret_val = true;
bailout:
if (!ret_val)
cleanupSocket_l();
return ret_val;
}
// generate a unique device ID that can be used for arbitration
bool CommonTimeServer::assignDeviceID() {
if (!mBindIfaceValid)
return false;
struct ifreq ifr;
memset(&ifr, 0, sizeof(ifr));
ifr.ifr_addr.sa_family = AF_INET;
strlcpy(ifr.ifr_name, mBindIface.string(), IFNAMSIZ);
int rc = ioctl(mSocket, SIOCGIFHWADDR, &ifr);
if (rc) {
ALOGE("%s:%d ioctl failed", __PRETTY_FUNCTION__, __LINE__);
return false;
}
if (ifr.ifr_addr.sa_family != ARPHRD_ETHER) {
ALOGE("%s:%d got non-Ethernet address", __PRETTY_FUNCTION__, __LINE__);
return false;
}
mDeviceID = 0;
for (int i = 0; i < ETH_ALEN; i++) {
mDeviceID = (mDeviceID << 8) | ifr.ifr_hwaddr.sa_data[i];
}
return true;
}
// generate a new timeline ID
void CommonTimeServer::assignTimelineID() {
do {
mTimelineID = (static_cast<uint64_t>(lrand48()) << 32)
| static_cast<uint64_t>(lrand48());
} while (mTimelineID == ICommonClock::kInvalidTimelineID);
}
// Select a preference between the device IDs of two potential masters.
// Returns true if the first ID wins, or false if the second ID wins.
bool CommonTimeServer::arbitrateMaster(
uint64_t deviceID1, uint8_t devicePrio1,
uint64_t deviceID2, uint8_t devicePrio2) {
return ((devicePrio1 > devicePrio2) ||
((devicePrio1 == devicePrio2) && (deviceID1 > deviceID2)));
}
bool CommonTimeServer::handlePacket() {
uint8_t buf[256];
struct sockaddr_storage srcAddr;
socklen_t srcAddrLen = sizeof(srcAddr);
ssize_t recvBytes = recvfrom(
mSocket, buf, sizeof(buf), 0,
reinterpret_cast<const sockaddr *>(&srcAddr), &srcAddrLen);
if (recvBytes < 0) {
ALOGE("%s:%d recvfrom failed", __PRETTY_FUNCTION__, __LINE__);
return false;
}
UniversalTimeServicePacket pkt;
recvBytes = pkt.deserializePacket(buf, recvBytes, mSyncGroupID);
if (recvBytes < 0)
return false;
bool result;
switch (pkt.packetType) {
case TIME_PACKET_WHO_IS_MASTER_REQUEST:
result = handleWhoIsMasterRequest(&pkt.p.who_is_master_request,
srcAddr);
break;
case TIME_PACKET_WHO_IS_MASTER_RESPONSE:
result = handleWhoIsMasterResponse(&pkt.p.who_is_master_response,
srcAddr);
break;
case TIME_PACKET_SYNC_REQUEST:
result = handleSyncRequest(&pkt.p.sync_request, srcAddr);
break;
case TIME_PACKET_SYNC_RESPONSE:
result = handleSyncResponse(&pkt.p.sync_response, srcAddr);
break;
case TIME_PACKET_MASTER_ANNOUNCEMENT:
result = handleMasterAnnouncement(&pkt.p.master_announcement,
srcAddr);
break;
default: {
ALOGD("%s:%d unknown packet type(%d)",
__PRETTY_FUNCTION__, __LINE__, pkt.packetType);
result = false;
} break;
}
return result;
}
bool CommonTimeServer::handleTimeout() {
// If we have no socket, then this must be a timeout to retry socket setup.
if (mSocket < 0)
return true;
switch (mState) {
case ICommonClock::STATE_INITIAL:
return handleTimeoutInitial();
case ICommonClock::STATE_CLIENT:
return handleTimeoutClient();
case ICommonClock::STATE_MASTER:
return handleTimeoutMaster();
case ICommonClock::STATE_RONIN:
return handleTimeoutRonin();
case ICommonClock::STATE_WAIT_FOR_ELECTION:
return handleTimeoutWaitForElection();
}
return false;
}
bool CommonTimeServer::handleTimeoutInitial() {
if (++mInitial_WhoIsMasterRequestTimeouts ==
kInitial_NumWhoIsMasterRetries) {
// none of our attempts to discover a master succeeded, so make
// this device the master
return becomeMaster("initial timeout");
} else {
// retry the WhoIsMaster request
return sendWhoIsMasterRequest();
}
}
bool CommonTimeServer::handleTimeoutClient() {
if (shouldPanicNotGettingGoodData())
return becomeInitial("timeout panic, no good data");
if (mClient_SyncRequestPending) {
mClient_SyncRequestPending = false;
if (++mClient_SyncRequestTimeouts < kClient_NumSyncRequestRetries) {
// a sync request has timed out, so retry
return sendSyncRequest();
} else {
// The master has failed to respond to a sync request for too many
// times in a row. Assume the master is dead and start electing
// a new master.
return becomeRonin("master not responding");
}
} else {
// initiate the next sync request
return sendSyncRequest();
}
}
bool CommonTimeServer::handleTimeoutMaster() {
// send another announcement from the master
return sendMasterAnnouncement();
}
bool CommonTimeServer::handleTimeoutRonin() {
if (++mRonin_WhoIsMasterRequestTimeouts == kRonin_NumWhoIsMasterRetries) {
// no other master is out there, so we won the election
return becomeMaster("no better masters detected");
} else {
return sendWhoIsMasterRequest();
}
}
bool CommonTimeServer::handleTimeoutWaitForElection() {
return becomeRonin("timeout waiting for election conclusion");
}
bool CommonTimeServer::handleWhoIsMasterRequest(
const WhoIsMasterRequestPacket* request,
const sockaddr_storage& srcAddr) {
if (mState == ICommonClock::STATE_MASTER) {
// is this request related to this master's timeline?
if (request->timelineID != ICommonClock::kInvalidTimelineID &&
request->timelineID != mTimelineID)
return true;
WhoIsMasterResponsePacket pkt;
pkt.initHeader(mTimelineID, mSyncGroupID);
pkt.deviceID = mDeviceID;
pkt.devicePriority = effectivePriority();
uint8_t buf[256];
ssize_t bufSz = pkt.serializePacket(buf, sizeof(buf));
if (bufSz < 0)
return false;
ssize_t sendBytes = sendto(
mSocket, buf, bufSz, 0,
reinterpret_cast<const sockaddr *>(&srcAddr),
sizeof(srcAddr));
if (sendBytes == -1) {
ALOGE("%s:%d sendto failed", __PRETTY_FUNCTION__, __LINE__);
return false;
}
} else if (mState == ICommonClock::STATE_RONIN) {
// if we hear a WhoIsMaster request from another device following
// the same timeline and that device wins arbitration, then we will stop
// trying to elect ourselves master and will instead wait for an
// announcement from the election winner
if (request->timelineID != mTimelineID)
return true;
if (arbitrateMaster(request->senderDeviceID,
request->senderDevicePriority,
mDeviceID,
effectivePriority()))
return becomeWaitForElection("would lose election");
return true;
} else if (mState == ICommonClock::STATE_INITIAL) {
// If a group of devices booted simultaneously (e.g. after a power
// outage) and all of them are in the initial state and there is no
// master, then each device may time out and declare itself master at
// the same time. To avoid this, listen for
// WhoIsMaster(InvalidTimeline) requests from peers. If we would lose
// arbitration against that peer, reset our timeout count so that the
// peer has a chance to become master before we time out.
if (request->timelineID == ICommonClock::kInvalidTimelineID &&
arbitrateMaster(request->senderDeviceID,
request->senderDevicePriority,
mDeviceID,
effectivePriority())) {
mInitial_WhoIsMasterRequestTimeouts = 0;
}
}
return true;
}
bool CommonTimeServer::handleWhoIsMasterResponse(
const WhoIsMasterResponsePacket* response,
const sockaddr_storage& srcAddr) {
if (mState == ICommonClock::STATE_INITIAL || mState == ICommonClock::STATE_RONIN) {
return becomeClient(srcAddr,
response->deviceID,
response->devicePriority,
response->timelineID,
"heard whois response");
} else if (mState == ICommonClock::STATE_CLIENT) {
// if we get multiple responses because there are multiple devices
// who believe that they are master, then follow the master that
// wins arbitration
if (arbitrateMaster(response->deviceID,
response->devicePriority,
mClient_MasterDeviceID,
mClient_MasterDevicePriority)) {
return becomeClient(srcAddr,
response->deviceID,
response->devicePriority,
response->timelineID,
"heard whois response");
}
}
return true;
}
bool CommonTimeServer::handleSyncRequest(const SyncRequestPacket* request,
const sockaddr_storage& srcAddr) {
SyncResponsePacket pkt;
pkt.initHeader(mTimelineID, mSyncGroupID);
if ((mState == ICommonClock::STATE_MASTER) &&
(mTimelineID == request->timelineID)) {
int64_t rxLocalTime = mLastPacketRxLocalTime;
int64_t rxCommonTime;
// If we are master on an actual network and have actual clients, then
// we are no longer low priority.
setForceLowPriority(false);
if (OK != mCommonClock.localToCommon(rxLocalTime, &rxCommonTime)) {
return false;
}
int64_t txLocalTime = mLocalClock.getLocalTime();;
int64_t txCommonTime;
if (OK != mCommonClock.localToCommon(txLocalTime, &txCommonTime)) {
return false;
}
pkt.nak = 0;
pkt.clientTxLocalTime = request->clientTxLocalTime;
pkt.masterRxCommonTime = rxCommonTime;
pkt.masterTxCommonTime = txCommonTime;
} else {
pkt.nak = 1;
pkt.clientTxLocalTime = 0;
pkt.masterRxCommonTime = 0;
pkt.masterTxCommonTime = 0;
}
uint8_t buf[256];
ssize_t bufSz = pkt.serializePacket(buf, sizeof(buf));
if (bufSz < 0)
return false;
ssize_t sendBytes = sendto(
mSocket, &buf, bufSz, 0,
reinterpret_cast<const sockaddr *>(&srcAddr),
sizeof(srcAddr));
if (sendBytes == -1) {
ALOGE("%s:%d sendto failed", __PRETTY_FUNCTION__, __LINE__);
return false;
}
return true;
}
bool CommonTimeServer::handleSyncResponse(
const SyncResponsePacket* response,
const sockaddr_storage& srcAddr) {
if (mState != ICommonClock::STATE_CLIENT)
return true;
assert(mMasterEPValid);
if (!sockaddrMatch(srcAddr, mMasterEP, true)) {
char srcEP[64], expectedEP[64];
sockaddrToString(srcAddr, true, srcEP, sizeof(srcEP));
sockaddrToString(mMasterEP, true, expectedEP, sizeof(expectedEP));
ALOGI("Dropping sync response from unexpected address."
" Expected %s Got %s", expectedEP, srcEP);
return true;
}
if (response->nak) {
// if our master is no longer accepting requests, then we need to find
// a new master
return becomeRonin("master NAK'ed");
}
mClient_SyncRequestPending = 0;
mClient_SyncRequestTimeouts = 0;
mClient_PacketRTTLog.logRX(response->clientTxLocalTime,
mLastPacketRxLocalTime);
bool result;
if (!(mClient_SyncRespsRXedFromCurMaster++)) {
// the first request/response exchange between a client and a master
// may take unusually long due to ARP, so discard it.
result = true;
} else {
int64_t clientTxLocalTime = response->clientTxLocalTime;
int64_t clientRxLocalTime = mLastPacketRxLocalTime;
int64_t masterTxCommonTime = response->masterTxCommonTime;
int64_t masterRxCommonTime = response->masterRxCommonTime;
int64_t rtt = (clientRxLocalTime - clientTxLocalTime);
int64_t avgLocal = (clientTxLocalTime + clientRxLocalTime) >> 1;
int64_t avgCommon = (masterTxCommonTime + masterRxCommonTime) >> 1;
// if the RTT of the packet is significantly larger than the panic
// threshold, we should simply discard it. Its better to do nothing
// than to take cues from a packet like that.
int rttCommon = mCommonClock.localDurationToCommonDuration(rtt);
if (rttCommon > (static_cast<int64_t>(mPanicThresholdUsec) *
kRTTDiscardPanicThreshMultiplier)) {
ALOGV("Dropping sync response with RTT of %lld uSec", rttCommon);
mClient_ExpiredSyncRespsRXedFromCurMaster++;
if (shouldPanicNotGettingGoodData())
return becomeInitial("RX panic, no good data");
} else {
result = mClockRecovery.pushDisciplineEvent(avgLocal, avgCommon, rttCommon);
mClient_LastGoodSyncRX = clientRxLocalTime;
if (result) {
// indicate to listeners that we've synced to the common timeline
notifyClockSync();
} else {
ALOGE("Panic! Observed clock sync error is too high to tolerate,"
" resetting state machine and starting over.");
notifyClockSyncLoss();
return becomeInitial("panic");
}
}
}
mCurTimeout.setTimeout(mSyncRequestIntervalMs);
return result;
}
bool CommonTimeServer::handleMasterAnnouncement(
const MasterAnnouncementPacket* packet,
const sockaddr_storage& srcAddr) {
uint64_t newDeviceID = packet->deviceID;
uint8_t newDevicePrio = packet->devicePriority;
uint64_t newTimelineID = packet->timelineID;
if (mState == ICommonClock::STATE_INITIAL ||
mState == ICommonClock::STATE_RONIN ||
mState == ICommonClock::STATE_WAIT_FOR_ELECTION) {
// if we aren't currently following a master, then start following
// this new master
return becomeClient(srcAddr,
newDeviceID,
newDevicePrio,
newTimelineID,
"heard master announcement");
} else if (mState == ICommonClock::STATE_CLIENT) {
// if the new master wins arbitration against our current master,
// then become a client of the new master
if (arbitrateMaster(newDeviceID,
newDevicePrio,
mClient_MasterDeviceID,
mClient_MasterDevicePriority))
return becomeClient(srcAddr,
newDeviceID,
newDevicePrio,
newTimelineID,
"heard master announcement");
} else if (mState == ICommonClock::STATE_MASTER) {
// two masters are competing - if the new one wins arbitration, then
// cease acting as master
if (arbitrateMaster(newDeviceID, newDevicePrio,
mDeviceID, effectivePriority()))
return becomeClient(srcAddr, newDeviceID,
newDevicePrio, newTimelineID,
"heard master announcement");
}
return true;
}
bool CommonTimeServer::sendWhoIsMasterRequest() {
assert(mState == ICommonClock::STATE_INITIAL || mState == ICommonClock::STATE_RONIN);
// If we have no socket, then we must be in the unconfigured initial state.
// Don't report any errors, just don't try to send the initial who-is-master
// query. Eventually, our network will either become configured, or we will
// be forced into network-less master mode by higher level code.
if (mSocket < 0) {
assert(mState == ICommonClock::STATE_INITIAL);
return true;
}
bool ret = false;
WhoIsMasterRequestPacket pkt;
pkt.initHeader(mSyncGroupID);
pkt.senderDeviceID = mDeviceID;
pkt.senderDevicePriority = effectivePriority();
uint8_t buf[256];
ssize_t bufSz = pkt.serializePacket(buf, sizeof(buf));
if (bufSz >= 0) {
ssize_t sendBytes = sendto(
mSocket, buf, bufSz, 0,
reinterpret_cast<const sockaddr *>(&mMasterElectionEP),
sizeof(mMasterElectionEP));
if (sendBytes < 0)
ALOGE("WhoIsMaster sendto failed (errno %d)", errno);
ret = true;
}
if (mState == ICommonClock::STATE_INITIAL) {
mCurTimeout.setTimeout(kInitial_WhoIsMasterTimeoutMs);
} else {
mCurTimeout.setTimeout(kRonin_WhoIsMasterTimeoutMs);
}
return ret;
}
bool CommonTimeServer::sendSyncRequest() {
// If we are sending sync requests, then we must be in the client state and
// we must have a socket (when we have no network, we are only supposed to
// be in INITIAL or MASTER)
assert(mState == ICommonClock::STATE_CLIENT);
assert(mSocket >= 0);
bool ret = false;
SyncRequestPacket pkt;
pkt.initHeader(mTimelineID, mSyncGroupID);
pkt.clientTxLocalTime = mLocalClock.getLocalTime();
if (!mClient_FirstSyncTX)
mClient_FirstSyncTX = pkt.clientTxLocalTime;
mClient_PacketRTTLog.logTX(pkt.clientTxLocalTime);
uint8_t buf[256];
ssize_t bufSz = pkt.serializePacket(buf, sizeof(buf));
if (bufSz >= 0) {
ssize_t sendBytes = sendto(
mSocket, buf, bufSz, 0,
reinterpret_cast<const sockaddr *>(&mMasterEP),
sizeof(mMasterEP));
if (sendBytes < 0)
ALOGE("SyncRequest sendto failed (errno %d)", errno);
ret = true;
}
mClient_SyncsSentToCurMaster++;
mCurTimeout.setTimeout(mSyncRequestIntervalMs);
mClient_SyncRequestPending = true;
return ret;
}
bool CommonTimeServer::sendMasterAnnouncement() {
bool ret = false;
assert(mState == ICommonClock::STATE_MASTER);
// If we are being asked to send a master announcement, but we have no
// socket, we must be in network-less master mode. Don't bother to send the
// announcement, and don't bother to schedule a timeout. When the network
// comes up, the work thread will get poked and start the process of
// figuring out who the current master should be.
if (mSocket < 0) {
mCurTimeout.setTimeout(kInfiniteTimeout);
return true;
}
MasterAnnouncementPacket pkt;
pkt.initHeader(mTimelineID, mSyncGroupID);
pkt.deviceID = mDeviceID;
pkt.devicePriority = effectivePriority();
uint8_t buf[256];
ssize_t bufSz = pkt.serializePacket(buf, sizeof(buf));
if (bufSz >= 0) {
ssize_t sendBytes = sendto(
mSocket, buf, bufSz, 0,
reinterpret_cast<const sockaddr *>(&mMasterElectionEP),
sizeof(mMasterElectionEP));
if (sendBytes < 0)
ALOGE("MasterAnnouncement sendto failed (errno %d)", errno);
ret = true;
}
mCurTimeout.setTimeout(mMasterAnnounceIntervalMs);
return ret;
}
bool CommonTimeServer::becomeClient(const sockaddr_storage& masterEP,
uint64_t masterDeviceID,
uint8_t masterDevicePriority,
uint64_t timelineID,
const char* cause) {
char newEPStr[64], oldEPStr[64];
sockaddrToString(masterEP, true, newEPStr, sizeof(newEPStr));
sockaddrToString(mMasterEP, mMasterEPValid, oldEPStr, sizeof(oldEPStr));
ALOGI("%s --> CLIENT (%s) :%s"
" OldMaster: %02x-%014llx::%016llx::%s"
" NewMaster: %02x-%014llx::%016llx::%s",
stateToString(mState), cause,
(mTimelineID != timelineID) ? " (new timeline)" : "",
mClient_MasterDevicePriority, mClient_MasterDeviceID,
mTimelineID, oldEPStr,
masterDevicePriority, masterDeviceID,
timelineID, newEPStr);
if (mTimelineID != timelineID) {
// start following a new timeline
mTimelineID = timelineID;
mClockRecovery.reset(true, true);
notifyClockSyncLoss();
} else {
// start following a new master on the existing timeline
mClockRecovery.reset(false, true);
}
mMasterEP = masterEP;
mMasterEPValid = true;
// If we are on a real network as a client of a real master, then we should
// no longer force low priority. If our master disappears, we should have
// the high priority bit set during the election to replace the master
// because this group was a real group and not a singleton created in
// networkless mode.
setForceLowPriority(false);
mClient_MasterDeviceID = masterDeviceID;
mClient_MasterDevicePriority = masterDevicePriority;
resetSyncStats();
setState(ICommonClock::STATE_CLIENT);
// add some jitter to when the various clients send their requests
// in order to reduce the likelihood that a group of clients overload
// the master after receiving a master announcement
usleep((lrand48() % 100) * 1000);
return sendSyncRequest();
}
bool CommonTimeServer::becomeMaster(const char* cause) {
uint64_t oldTimelineID = mTimelineID;
if (mTimelineID == ICommonClock::kInvalidTimelineID) {
// this device has not been following any existing timeline,
// so it will create a new timeline and declare itself master
assert(!mCommonClock.isValid());
// set the common time basis
mCommonClock.setBasis(mLocalClock.getLocalTime(), 0);
// assign an arbitrary timeline iD
assignTimelineID();
// notify listeners that we've created a common timeline
notifyClockSync();
}
ALOGI("%s --> MASTER (%s) : %s timeline %016llx",
stateToString(mState), cause,
(oldTimelineID == mTimelineID) ? "taking ownership of"
: "creating new",
mTimelineID);
memset(&mMasterEP, 0, sizeof(mMasterEP));
mMasterEPValid = false;
mClient_MasterDevicePriority = effectivePriority();
mClient_MasterDeviceID = mDeviceID;
mClockRecovery.reset(false, true);
resetSyncStats();
setState(ICommonClock::STATE_MASTER);
return sendMasterAnnouncement();
}
bool CommonTimeServer::becomeRonin(const char* cause) {
// If we were the client of a given timeline, but had never received even a
// single time sync packet, then we transition back to Initial instead of
// Ronin. If we transition to Ronin and end up becoming the new Master, we
// will be unable to service requests for other clients because we never
// actually knew what time it was. By going to initial, we ensure that
// other clients who know what time it is, but would lose master arbitration
// in the Ronin case, will step up and become the proper new master of the
// old timeline.
char oldEPStr[64];
sockaddrToString(mMasterEP, mMasterEPValid, oldEPStr, sizeof(oldEPStr));
memset(&mMasterEP, 0, sizeof(mMasterEP));
mMasterEPValid = false;
if (mCommonClock.isValid()) {
ALOGI("%s --> RONIN (%s) : lost track of previously valid timeline "
"%02x-%014llx::%016llx::%s (%d TXed %d RXed %d RXExpired)",
stateToString(mState), cause,
mClient_MasterDevicePriority, mClient_MasterDeviceID,
mTimelineID, oldEPStr,
mClient_SyncsSentToCurMaster,
mClient_SyncRespsRXedFromCurMaster,
mClient_ExpiredSyncRespsRXedFromCurMaster);
mRonin_WhoIsMasterRequestTimeouts = 0;
setState(ICommonClock::STATE_RONIN);
return sendWhoIsMasterRequest();
} else {
ALOGI("%s --> INITIAL (%s) : never synced timeline "
"%02x-%014llx::%016llx::%s (%d TXed %d RXed %d RXExpired)",
stateToString(mState), cause,
mClient_MasterDevicePriority, mClient_MasterDeviceID,
mTimelineID, oldEPStr,
mClient_SyncsSentToCurMaster,
mClient_SyncRespsRXedFromCurMaster,
mClient_ExpiredSyncRespsRXedFromCurMaster);
return becomeInitial("ronin, no timeline");
}
}
bool CommonTimeServer::becomeWaitForElection(const char* cause) {
ALOGI("%s --> WAIT_FOR_ELECTION (%s) : dropping out of election,"
" waiting %d mSec for completion.",
stateToString(mState), cause, kWaitForElection_TimeoutMs);
setState(ICommonClock::STATE_WAIT_FOR_ELECTION);
mCurTimeout.setTimeout(kWaitForElection_TimeoutMs);
return true;
}
bool CommonTimeServer::becomeInitial(const char* cause) {
ALOGI("Entering INITIAL (%s), total reset.", cause);
setState(ICommonClock::STATE_INITIAL);
// reset clock recovery
mClockRecovery.reset(true, true);
// reset internal state bookkeeping.
mCurTimeout.setTimeout(kInfiniteTimeout);
memset(&mMasterEP, 0, sizeof(mMasterEP));
mMasterEPValid = false;
mLastPacketRxLocalTime = 0;
mTimelineID = ICommonClock::kInvalidTimelineID;
mClockSynced = false;
mInitial_WhoIsMasterRequestTimeouts = 0;
mClient_MasterDeviceID = 0;
mClient_MasterDevicePriority = 0;
mRonin_WhoIsMasterRequestTimeouts = 0;
resetSyncStats();
// send the first request to discover the master
return sendWhoIsMasterRequest();
}
void CommonTimeServer::notifyClockSync() {
if (!mClockSynced) {
mClockSynced = true;
mICommonClock->notifyOnTimelineChanged(mTimelineID);
}
}
void CommonTimeServer::notifyClockSyncLoss() {
if (mClockSynced) {
mClockSynced = false;
mICommonClock->notifyOnTimelineChanged(
ICommonClock::kInvalidTimelineID);
}
}
void CommonTimeServer::setState(ICommonClock::State s) {
mState = s;
}
const char* CommonTimeServer::stateToString(ICommonClock::State s) {
switch(s) {
case ICommonClock::STATE_INITIAL:
return "INITIAL";
case ICommonClock::STATE_CLIENT:
return "CLIENT";
case ICommonClock::STATE_MASTER:
return "MASTER";
case ICommonClock::STATE_RONIN:
return "RONIN";
case ICommonClock::STATE_WAIT_FOR_ELECTION:
return "WAIT_FOR_ELECTION";
default:
return "unknown";
}
}
void CommonTimeServer::sockaddrToString(const sockaddr_storage& addr,
bool addrValid,
char* buf, size_t bufLen) {
if (!bufLen || !buf)
return;
if (addrValid) {
switch (addr.ss_family) {
case AF_INET: {
const struct sockaddr_in* sa =
reinterpret_cast<const struct sockaddr_in*>(&addr);
unsigned long a = ntohl(sa->sin_addr.s_addr);
uint16_t p = ntohs(sa->sin_port);
snprintf(buf, bufLen, "%lu.%lu.%lu.%lu:%hu",
((a >> 24) & 0xFF), ((a >> 16) & 0xFF),
((a >> 8) & 0xFF), (a & 0xFF), p);
} break;
case AF_INET6: {
const struct sockaddr_in6* sa =
reinterpret_cast<const struct sockaddr_in6*>(&addr);
const uint8_t* a = sa->sin6_addr.s6_addr;
uint16_t p = ntohs(sa->sin6_port);
snprintf(buf, bufLen,
"%02X%02X:%02X%02X:%02X%02X:%02X%02X:"
"%02X%02X:%02X%02X:%02X%02X:%02X%02X port %hd",
a[0], a[1], a[ 2], a[ 3], a[ 4], a[ 5], a[ 6], a[ 7],
a[8], a[9], a[10], a[11], a[12], a[13], a[14], a[15],
p);
} break;
default:
snprintf(buf, bufLen,
"<unknown sockaddr family %d>", addr.ss_family);
break;
}
} else {
snprintf(buf, bufLen, "<none>");
}
buf[bufLen - 1] = 0;
}
bool CommonTimeServer::sockaddrMatch(const sockaddr_storage& a1,
const sockaddr_storage& a2,
bool matchAddressOnly) {
if (a1.ss_family != a2.ss_family)
return false;
switch (a1.ss_family) {
case AF_INET: {
const struct sockaddr_in* sa1 =
reinterpret_cast<const struct sockaddr_in*>(&a1);
const struct sockaddr_in* sa2 =
reinterpret_cast<const struct sockaddr_in*>(&a2);
if (sa1->sin_addr.s_addr != sa2->sin_addr.s_addr)
return false;
return (matchAddressOnly || (sa1->sin_port == sa2->sin_port));
} break;
case AF_INET6: {
const struct sockaddr_in6* sa1 =
reinterpret_cast<const struct sockaddr_in6*>(&a1);
const struct sockaddr_in6* sa2 =
reinterpret_cast<const struct sockaddr_in6*>(&a2);
if (memcmp(&sa1->sin6_addr, &sa2->sin6_addr, sizeof(sa2->sin6_addr)))
return false;
return (matchAddressOnly || (sa1->sin6_port == sa2->sin6_port));
} break;
// Huh? We don't deal in non-IPv[46] addresses. Not sure how we got
// here, but we don't know how to comapre these addresses and simply
// default to a no-match decision.
default: return false;
}
}
void CommonTimeServer::TimeoutHelper::setTimeout(int msec) {
mTimeoutValid = (msec >= 0);
if (mTimeoutValid)
mEndTime = systemTime() +
(static_cast<nsecs_t>(msec) * 1000000);
}
int CommonTimeServer::TimeoutHelper::msecTillTimeout() {
if (!mTimeoutValid)
return kInfiniteTimeout;
nsecs_t now = systemTime();
if (now >= mEndTime)
return 0;
uint64_t deltaMsec = (((mEndTime - now) + 999999) / 1000000);
if (deltaMsec > static_cast<uint64_t>(MAX_INT))
return MAX_INT;
return static_cast<int>(deltaMsec);
}
bool CommonTimeServer::shouldPanicNotGettingGoodData() {
if (mClient_FirstSyncTX) {
int64_t now = mLocalClock.getLocalTime();
int64_t delta = now - (mClient_LastGoodSyncRX
? mClient_LastGoodSyncRX
: mClient_FirstSyncTX);
int64_t deltaUsec = mCommonClock.localDurationToCommonDuration(delta);
if (deltaUsec >= kNoGoodDataPanicThresholdUsec)
return true;
}
return false;
}
void CommonTimeServer::PacketRTTLog::logTX(int64_t txTime) {
txTimes[wrPtr] = txTime;
rxTimes[wrPtr] = 0;
wrPtr = (wrPtr + 1) % RTT_LOG_SIZE;
if (!wrPtr)
logFull = true;
}
void CommonTimeServer::PacketRTTLog::logRX(int64_t txTime, int64_t rxTime) {
if (!logFull && !wrPtr)
return;
uint32_t i = logFull ? wrPtr : 0;
do {
if (txTimes[i] == txTime) {
rxTimes[i] = rxTime;
break;
}
i = (i + 1) % RTT_LOG_SIZE;
} while (i != wrPtr);
}
} // namespace android
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