[lwip-users] Obtaining destination ip address from udp callback

[Charles Yarnold]

Hello all,

I'm currently trying to expand energia's implementation on lwip for the tiva c ti launchpad to allow for reading of the destination IP of a udp packet. (https://github.com/energia/Energia/blob/master/hardware/lm4f/libraries/Ethernet)

Reading through lwip's udp.h and udp.cpp I'm unable to find where I could pull this information from when the udp recv callback is triggered. It seems to pass the source ip and port but not the destination ip. Destination ip also doesn't seem to be included in the udp_pcb struct, only ports.

Energia's callback function is here: https://github.com/energia/Energia/blob/master/hardware/lm4f/libraries/Ethernet/EthernetUdp.cpp#L11

Ideally I'm trying to extend the engergia ethernet library to include a function to return the destination ip of the packet, i.e. 192.168.1.50 or 192.168.1.255 to allow for filtering on the application layer of packets based off content and if the packet was boradcast or not.

I hope this makes some sense, I must admit this is overreaching some what for me with my current abilities, but if you don't try you won't learn I guess. Any pointers or reading materials would be most welcome, I'm not asking someone to code this for me.

All the best,

Charles