xfer: set TCP_NODELAY on recv side

This works around hangs where only a couple of bytes could be sent
to the socket and retrying to send the last bytes of the ack never
seem to work.

Closes #1167.

src/plugins/xfer/xfer-dcc.c

@@ -28,6 +28,7 @@
 #include <sys/socket.h>
 #include <poll.h>
 #include <netinet/in.h>
+#include <netinet/tcp.h>
 #include <fcntl.h>
 #include <time.h>
 #include <netdb.h>
@@ -345,6 +346,11 @@ xfer_dcc_recv_file_child (struct t_xfer *xfer)
         return;
     }
 
+    /* set TCP_NODELAY to be more aggressive with acks */
+    /* ignore error as transfer should still work if this fails */
+    flags = 1;
+    setsockopt(xfer->sock, IPPROTO_TCP, TCP_NODELAY, &flags, sizeof(flags));
+
     /* connection is OK, change DCC status (inform parent process) */
     xfer_network_write_pipe (xfer, XFER_STATUS_ACTIVE,
                              XFER_NO_ERROR);