Use eager retransmission if the transport is lossy and cheap.

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/TransportConnectionWriter.java

@@ -22,6 +22,11 @@ public interface TransportConnectionWriter {
 	 */
 	int getMaxIdleTime();
 
+	/**
+	 * Returns true if the transport is lossy and cheap.
+	 */
+	boolean isLossyAndCheap();
+
 	/**
 	 * Returns an output stream for writing to the transport connection.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/duplex/AbstractDuplexTransportConnection.java

@@ -79,6 +79,11 @@ public abstract class AbstractDuplexTransportConnection
 			return plugin.getMaxIdleTime();
 		}
 
+		@Override
+		public boolean isLossyAndCheap() {
+			return false;
+		}
+
 		@Override
 		public OutputStream getOutputStream() throws IOException {
 			return AbstractDuplexTransportConnection.this.getOutputStream();

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/simplex/SimplexPlugin.java

@@ -15,6 +15,12 @@ import javax.annotation.Nullable;
 @NotNullByDefault
 public interface SimplexPlugin extends Plugin {
 
+	/**
+	 * Returns true if the transport is likely to lose streams and the cost of
+	 * transmitting redundant copies of data is cheap.
+	 */
+	boolean isLossyAndCheap();
+
 	/**
 	 * Attempts to create and return a reader for the given transport
 	 * properties. Returns null if a reader cannot be created.

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncSessionFactory.java

@@ -16,7 +16,7 @@ public interface SyncSessionFactory {
 			PriorityHandler handler);
 
 	SyncSession createSimplexOutgoingSession(ContactId c, TransportId t,
-			int maxLatency, StreamWriter streamWriter);
+			int maxLatency, boolean eager, StreamWriter streamWriter);
 
 	SyncSession createDuplexOutgoingSession(ContactId c, TransportId t,
 			int maxLatency, int maxIdleTime, StreamWriter streamWriter,