Adding lwip Client to NIOS-II

Most of the people here read all the forums anyway, so just pick one that seems appropriate and ask your question there. Multiposting creates several discussions in parallel on the same subject, which makes it very difficult to follow.

I thought that the get_ip_addr and get_mac_addr functions were specific to Interniche, but they seem to be required with lwip too.

Have you read that document? http://www.altera.com.cn/literature/hb/nios2/n2sw_nii52009.pdf

You need to add those two functions to your application, as described in pages 16-4 and further.