* companion radio: connection status now supported (Keep_alive pings, etc)

src/helpers/BaseChatMesh.cpp

@@ -374,7 +374,7 @@ int  BaseChatMesh::sendStatusRequest(const ContactInfo& recipient, uint32_t& est
   uint8_t temp[13];
   uint32_t now = getRTCClock()->getCurrentTimeUnique();
   memcpy(temp, &now, 4);   // mostly an extra blob to help make packet_hash unique
-  temp[4] = CMD_GET_STATUS;
+  temp[4] = REQ_TYPE_GET_STATUS;
   memset(&temp[5], 0, 4);  // reserved (possibly for 'since' param)
   getRNG()->random(&temp[9], 4);   // random blob to help make packet-hash unique
 
@@ -394,6 +394,121 @@ int  BaseChatMesh::sendStatusRequest(const ContactInfo& recipient, uint32_t& est
   return MSG_SEND_FAILED;
 }
 
+bool BaseChatMesh::startConnection(const ContactInfo& contact, uint16_t keep_alive_secs) {
+  int use_idx = -1;
+  for (int i = 0; i < MAX_CONNECTIONS; i++) {
+    if (connections[i].keep_alive_millis == 0) {  // free slot?
+      use_idx = i;
+    } else if (connections[i].server_id.matches(contact.id)) {  // already in table?
+      use_idx = i;
+      break;
+    }
+  }
+  if (use_idx < 0) {
+    return false;   // table is full
+  }
+  connections[use_idx].server_id = contact.id;
+  uint32_t interval = connections[use_idx].keep_alive_millis = ((uint32_t)keep_alive_secs)*1000;
+  connections[use_idx].next_ping = futureMillis(interval);
+  connections[use_idx].expected_ack = 0;
+  connections[use_idx].last_activity = getRTCClock()->getCurrentTime();
+  return true;  // success
+}
+
+void BaseChatMesh::stopConnection(const uint8_t* pub_key) {
+  for (int i = 0; i < MAX_CONNECTIONS; i++) {
+    if (connections[i].server_id.matches(pub_key)) {
+      connections[i].keep_alive_millis = 0;  // mark slot as now free
+      connections[i].next_ping = 0;
+      connections[i].expected_ack = 0;
+      connections[i].last_activity = 0;
+      break;
+    }
+  }
+}
+
+bool BaseChatMesh::hasConnectionTo(const uint8_t* pub_key) {
+  for (int i = 0; i < MAX_CONNECTIONS; i++) {
+    if (connections[i].keep_alive_millis > 0 && connections[i].server_id.matches(pub_key)) return true;
+  }
+  return false;
+}
+
+void BaseChatMesh::markConnectionActive(const ContactInfo& contact) {
+  for (int i = 0; i < MAX_CONNECTIONS; i++) {
+    if (connections[i].keep_alive_millis > 0 && connections[i].server_id.matches(contact.id)) {
+      connections[i].last_activity = getRTCClock()->getCurrentTime();
+
+      // re-schedule next KEEP_ALIVE, now that we have heard from server
+      connections[i].next_ping = futureMillis(connections[i].keep_alive_millis);
+      break;
+    }
+  }
+}
+
+bool BaseChatMesh::checkConnectionsAck(const uint8_t* data) {
+  for (int i = 0; i < MAX_CONNECTIONS; i++) {
+    if (connections[i].keep_alive_millis > 0 && memcmp(&connections[i].expected_ack, data, 4) == 0) {
+      // yes, got an ack for our keep_alive request!
+      connections[i].expected_ack = 0;
+      connections[i].last_activity = getRTCClock()->getCurrentTime();
+
+      // re-schedule next KEEP_ALIVE, now that we have heard from server
+      connections[i].next_ping = futureMillis(connections[i].keep_alive_millis);
+      return true;  // yes, a match
+    }
+  }
+  return false;  /// no match
+}
+
+void BaseChatMesh::checkConnections() {
+  // scan connections[] table, send KEEP_ALIVE requests
+  for (int i = 0; i < MAX_CONNECTIONS; i++) {
+    if (connections[i].keep_alive_millis == 0) continue;  // unused slot
+
+    uint32_t now = getRTCClock()->getCurrentTime();
+    uint32_t expire_secs = (connections[i].keep_alive_millis / 1000) * 5 / 2;   // 2.5 x keep_alive interval
+    if (now >= connections[i].last_activity + expire_secs) {
+      // connection now lost
+      connections[i].keep_alive_millis = 0;
+      connections[i].next_ping = 0;
+      connections[i].expected_ack = 0;
+      connections[i].last_activity = 0;
+      continue;
+    }
+
+    if (millisHasNowPassed(connections[i].next_ping)) {
+      auto contact = lookupContactByPubKey(connections[i].server_id.pub_key, PUB_KEY_SIZE);
+      if (contact == NULL) {
+        MESH_DEBUG_PRINTLN("checkConnections(): Keep_alive contact not found!");
+        continue;
+      }
+      if (contact->out_path_len < 0) {
+        MESH_DEBUG_PRINTLN("checkConnections(): Keep_alive contact, no out_path!");
+        continue;
+      }
+
+      // send KEEP_ALIVE request
+      uint8_t data[9];
+      uint32_t now = getRTCClock()->getCurrentTimeUnique();
+      memcpy(data, &now, 4);
+      data[4] = REQ_TYPE_KEEP_ALIVE;
+      memcpy(&data[5], &contact->sync_since, 4);
+    
+      // calc expected ACK reply
+      mesh::Utils::sha256((uint8_t *)&connections[i].expected_ack, 4, data, 9, self_id.pub_key, PUB_KEY_SIZE);
+
+      auto pkt = createDatagram(PAYLOAD_TYPE_REQ, contact->id, contact->shared_secret, data, 9);
+      if (pkt) {
+        sendDirect(pkt, contact->out_path, contact->out_path_len);
+      }
+    
+      // schedule next KEEP_ALIVE
+      connections[i].next_ping = futureMillis(connections[i].keep_alive_millis);
+    }
+  }
+}
+
 void BaseChatMesh::resetPathTo(ContactInfo& recipient) {
   recipient.out_path_len = -1;
 }

src/helpers/BaseChatMesh.h

@@ -27,7 +27,8 @@ struct ContactInfo {
 #define MSG_SEND_SENT_FLOOD   1
 #define MSG_SEND_SENT_DIRECT  2
 
-#define CMD_GET_STATUS      0x01   // same as _GET_STATS
+#define REQ_TYPE_GET_STATUS      0x01   // same as _GET_STATS
+#define REQ_TYPE_KEEP_ALIVE      0x02
 
 #define RESP_SERVER_LOGIN_OK      0   // response to ANON_REQ
 
@@ -48,6 +49,18 @@ public:
   #define MAX_CONTACTS  32
 #endif
 
+#ifndef MAX_CONNECTIONS
+  #define MAX_CONNECTIONS  16
+#endif
+
+struct ConnectionInfo {
+  mesh::Identity server_id;
+  unsigned long next_ping;
+  uint32_t last_activity;
+  uint32_t keep_alive_millis;
+  uint32_t expected_ack;
+};
+
 /**
  *  \brief  abstract Mesh class for common 'chat' client
  */
@@ -66,6 +79,7 @@ class BaseChatMesh : public mesh::Mesh {
 #endif
   mesh::Packet* _pendingLoopback;
   uint8_t temp_buf[MAX_TRANS_UNIT];
+  ConnectionInfo connections[MAX_CONNECTIONS];
 
   mesh::Packet* composeMsgPacket(const ContactInfo& recipient, uint32_t timestamp, uint8_t attempt, const char *text, uint32_t& expected_ack);
 
@@ -79,6 +93,7 @@ protected:
   #endif
     txt_send_timeout = 0;
     _pendingLoopback = NULL;
+    memset(connections, 0, sizeof(connections));
   }
 
   // 'UI' concepts, for sub-classes to implement
@@ -110,6 +125,14 @@ protected:
 #endif
   void onGroupDataRecv(mesh::Packet* packet, uint8_t type, const mesh::GroupChannel& channel, uint8_t* data, size_t len) override;
 
+  // Connections
+  bool startConnection(const ContactInfo& contact, uint16_t keep_alive_secs);
+  void stopConnection(const uint8_t* pub_key);
+  bool hasConnectionTo(const uint8_t* pub_key);
+  void markConnectionActive(const ContactInfo& contact);
+  bool checkConnectionsAck(const uint8_t* data);
+  void checkConnections();
+
 public:
   mesh::Packet* createSelfAdvert(const char* name, double lat=0.0, double lon=0.0);
   int  sendMessage(const ContactInfo& recipient, uint32_t timestamp, uint8_t attempt, const char* text, uint32_t& expected_ack, uint32_t& est_timeout);