Gigabit Ethernet Interface (via Marvell 88E1111) with Cyclone IVE FPGA

Oh yes I didn't notice in your code that you used the DMA driver directly and wasn't using a TCP/IP stack at all.

Indeed if you want to generate a correct UDP packet you will need to add the headers.

I suggest to change the length "0x00,0x2E" to an IP EtherType ("0x08, 0x00") so that you don't have to worry about the frame size and your packet is recognized as an IP packet.

Then instead of just the payload, you will need to put 20 bytes for the IP header and 4 or 8 more bytes for the UDP header. You can find the header definitions on Wikipedia:

https://en.wikipedia.org/wiki/internet_protocol_version_4#packet_structure https://en.wikipedia.org/wiki/user_datagram_protocol#packet_structure