DNS commands in lwip in FPGA

[aminpix]

I am trying to develop a code for Zynq using lwip in vivado/vitis.
I use the vitis sample code TCP_Client_Perf and modify it (I could compile and execute the sample code).
When I want to use dns_setserver command, I will get this error: undefined reference to `dns_setserver'
the only code I added to the sample code is:

#include "lwip/dns.h"


    struct in_addr* dnsserver;
    inet_aton("8.8.8.8", dnsserver);
    dns_setserver(0,dnsserver);