AC_MSG_CHECKING(if kppp's headers are installed)
# this is a little piece of code out of kppp. If it doesn't compile,
# kppp is not good for this system. It doesn't do anything, but enough
# to fail ;)
AC_LANG_SAVE
AC_LANG_CPLUSPLUS
AC_TRY_LINK([
#if defined(__osf__) || defined(__svr4__)
  #define _POSIX_PII_SOCKET
  extern "C" int sethostname(char *name, int name_len);
#endif
#include <unistd.h>
#include <arpa/inet.h>
#ifdef __DragonFly__
#include <net/ppp_layer/ppp_defs.h>
#else
#include <net/ppp_defs.h>
#endif
#include <netinet/in.h>

#ifdef __svr4__
  #include <sys/stropts.h>
  #include <net/pppio.h>		/* SVR4, Solaris 2, etc. */

#else
  #include <sys/time.h>
  #include <sys/socket.h>
  #include <net/if.h>

  #ifndef STREAMS 

    #if defined(linux)
      #ifndef aligned_u64
        #define aligned_u64 unsigned long long __attribute__((aligned(8)))
      #endif
      #include <linux/if_ppp.h>
    #elif defined(__DragonFly__)
      #include <net/ppp/if_ppp.h>
    #else
      #include <net/if_ppp.h>                /* BSD, NeXT, etc. */
    #endif

  #else				/* SunOS 4, AIX 4, OSF/1, etc. */
    #include <sys/stream.h>
    #include <net/ppp_str.h>
  #endif
#endif
],[
  sethostname("", 1); /* never run this program! :*/ 
], 
[ AC_MSG_RESULT(yes) ],
[ DO_NOT_COMPILE="$DO_NOT_COMPILE kppp"
  AC_MSG_RESULT(no)
])
AC_LANG_RESTORE
AC_CHECK_HEADERS(sys/param.h string.h)