TCP Fast Open disabled -> 'TCP_USER_TIMEOUT' undeclared #372

Hi,
when i disable TCP Fast Open (-DENABLE_TCP_FAST_OPEN=OFF) then i get this error message:

[ 31%] Building C object CMakeFiles/getdns_objects.dir/src/sync.c.o
/home/x/freetz-ng/source/target-mips_gcc-13.4.0_uClibc-1.0.58-nptl_kernel-3.10/getdns-1.7.3/src/stub.c: In function 'getdns_sock_tcp_send_timeout':
/home/x/freetz-ng/source/target-mips_gcc-13.4.0_uClibc-1.0.58-nptl_kernel-3.10/getdns-1.7.3/src/stub.c:458:45: error: 'TCP_USER_TIMEOUT' undeclared (first use in this function)
458 | if (setsockopt(sockfd, IPPROTO_TCP, TCP_USER_TIMEOUT,
| ^~~~~~~~~~~~~~~~
/home/x/freetz-ng/source/target-mips_gcc-13.4.0_uClibc-1.0.58-nptl_kernel-3.10/getdns-1.7.3/src/stub.c:458:45: note: each undeclared identifier is reported only once for each function it appears in
make[4]: *** [CMakeFiles/getdns_objects.dir/build.make:289: CMakeFiles/getdns_objects.dir/src/stub.c.o] Error 1

Thanx Jens