common_time: Move default election config to bcast.

Change the default master election and arbiration to use broadcast
instead of multicast.  As nice as the idea of using multicast for
discovery is, in the end it had just proven to be too unreliable in
random people's home infrastructures as well as the more complicated
managed infrastructures we are using internally.  Multicast still
works, and the service can still be configured to use it, but for now
we are switching to broadcast.

Also, add runtime checks to filter out our own broadcast traffic as
there does not seem to be any good sockopt in linux to do this for us
(there is one for multicast, but not broadcast).

Change-Id: I8ada3541cceca2e76c7a0c1a624a72026122c312

1 files changed, 14 insertions, 3 deletions

diff --git a/services/common_time/common_time_server.cpp b/services/common_time/common_time_server.cpp
index 17f99b9..21e706f 100644
--- a/services/common_time/common_time_server.cpp
+++ b/services/common_time/common_time_server.cpp
@@ -53,9 +53,9 @@
 
 namespace android {
 
-const char*    CommonTimeServer::kDefaultMasterElectionAddr = "239.195.128.88";
-const uint16_t CommonTimeServer::kDefaultMasterElectionPort = 8887;
-const uint64_t CommonTimeServer::kDefaultSyncGroupID = 0;
+const char*    CommonTimeServer::kDefaultMasterElectionAddr = "255.255.255.255";
+const uint16_t CommonTimeServer::kDefaultMasterElectionPort = 8886;
+const uint64_t CommonTimeServer::kDefaultSyncGroupID = 1;
 const uint8_t  CommonTimeServer::kDefaultMasterPriority = 1;
 const uint32_t CommonTimeServer::kDefaultMasterAnnounceIntervalMs = 10000;
 const uint32_t CommonTimeServer::kDefaultSyncRequestIntervalMs = 1000;
@@ -752,6 +752,9 @@ bool CommonTimeServer::handleTimeoutWaitForElection() {
 bool CommonTimeServer::handleWhoIsMasterRequest(
         const WhoIsMasterRequestPacket* request,
         const sockaddr_storage& srcAddr) {
+    // Skip our own messages which come back via broadcast loopback.
+    if (request->senderDeviceID == mDeviceID)
+        return true;
 
     char srcEPStr[64];
     sockaddrToString(srcAddr, true, srcEPStr, sizeof(srcEPStr));
@@ -829,6 +832,10 @@ bool CommonTimeServer::handleWhoIsMasterRequest(
 bool CommonTimeServer::handleWhoIsMasterResponse(
         const WhoIsMasterResponsePacket* response,
         const sockaddr_storage& srcAddr) {
+    // Skip our own messages which come back via broadcast loopback.
+    if (response->deviceID == mDeviceID)
+        return true;
+
     char srcEPStr[64];
     sockaddrToString(srcAddr, true, srcEPStr, sizeof(srcEPStr));
     mElectionLog.log("RXed WhoIs master response while in state %s.  "
@@ -996,6 +1003,10 @@ bool CommonTimeServer::handleMasterAnnouncement(
     uint8_t  newDevicePrio = packet->devicePriority;
     uint64_t newTimelineID = packet->timelineID;
 
+    // Skip our own messages which come back via broadcast loopback.
+    if (newDeviceID == mDeviceID)
+        return true;
+
     char srcEPStr[64];
     sockaddrToString(srcAddr, true, srcEPStr, sizeof(srcEPStr));
     mElectionLog.log("RXed master announcement while in state %s.  "