Data storage in the SDRAM from ethernet

Hello,

I am currently designing an FPGA system that would receive data through a Triple Speed Ethernet protocol and store the data into a SDRAM via the help of a controller.

My Hardware Platform (Qsys) involves two mSGDMAs connecting the Ethernet IP to the SDRAM controller, for rx and tx. I also have an On-chip memory (not for purposes of descriptor memory) which is not connected to the Ethernet IP or the mSGDMAs.

My NIOS BSP linker system has all the memory modules on the on-chip memory except for the heap and stack, which are allocated to the SDRAM controller. I am running the simple socket example, which connects to the ethernet (only when stack or heap are placed in the SDRAM).

My question is how do I know where in the SDRAM to allocate the socket receive buffer. I want to utilize most of the SDRAM space for the data, but I am also aware that some addresses are used for the TCP/IP initialization.

How would I know where my data from the ethernet is being stored (if it's at being stored in the SDRAM) without overwriting previously stored data?

Thank you very much for your help.