make -C src/ install-modules-all 
make[1]: Entering directory '/usr/local/src/kamailio-5.1/kamailio/src'
CC (gcc) [M websocket.so]               ws_frame.o
ws_frame.c:32:10: fatal error: unistr.h: No such file or directory
 #include <unistr.h>
          ^~~~~~~~~~
compilation terminated.
../../Makefile.rules:100: recipe for target 'ws_frame.o' failed
make[2]: *** [ws_frame.o] Error 1
Makefile:511: recipe for target 'install-modules' failed
make[1]: *** [install-modules] Error 1
make[1]: Leaving directory '/usr/local/src/kamailio-5.1/kamailio/src'
Makefile:27: recipe for target 'install-modules-all' failed
make: *** [install-modules-all] Error 2