I have been trying to implement simple PC client application which only sends tcp packets to server application that runs on ZYNQ custom board and is only receiving packets. Everything works fine, until I put some random printf just after lwip_recvfrom() function in server app. Then I am getting many prints "unable to alloc pbuf in recv_handler" which is printed from setup_rx_bds() function placed in xemacpsif_dma.c file. However, app doesn't crash there, but continues to work on. Nevertheless, I would like to know what could be causing this message?