Linux C: error of redefinition of in include headers

I have a project, which has below header include map:

main.c <- main.h <- tcphelper.h <- tcptest.h <- util.h
                 <- udptest.h    <------------- util.h

In util.h, I defined a function prototype of struct cpu_usage:

void get_cpu_usage(struct cpu_usage *cu);

Now when I compile this project by GCC, I have this redefinition error. How do solve this problem?

thanks!

In file included from udptest.h:15:0,
                 from main.h:10,
                 from main.c:7:
util.h:27:8: error: redefinition of struct cpu_usage
 struct cpu_usage{
        ^
In file included from tcptest.h:14:0,
                 from tcphelper.h:10,
                 from main.h:9,
                 from main.c:7:
util.h:27:8: note: originally defined here
 struct cpu_usage{
        ^