-AC_CACHE_CHECK([for linux/if_tun.h], tinc_cv_linux_if_tun_h,
-[ AC_TRY_COMPILE([#include <linux/if_tun.h>],
- [int a = IFF_TAP],
- if_tun_h="linux/if_tun.h",
- if_tun_h="no")
- if test $if_tun_h = no; then
- AC_MSG_RESULT(none)
- else
- AC_DEFINE(HAVE_TUNTAP)
- AC_DEFINE_UNQUOTED(LINUX_IF_TUN_H, "$if_tun_h")
- AC_SUBST(LINUX_IF_TUN_H)
- AC_MSG_RESULT($if_tun_h)
+ AC_ARG_WITH(kernel,
+ AS_HELP_STRING([--with-kernel=DIR], [give the directory with kernel sources (default: /usr/src/linux)]),
+ kerneldir="$withval",
+ kerneldir="/usr/src/linux"
+ )
+
+ AC_CACHE_CHECK([for linux/if_tun.h], tinc_cv_linux_if_tun_h,
+ [
+ AC_COMPILE_IFELSE(
+ AC_LANG_PROGRAM([
+ #include "$kerneldir/include/linux/if_tun.h"
+ int a = IFF_TAP;
+ ]),
+ [if_tun_h="\"$kerneldir/include/linux/if_tun.h\""],
+ [AC_COMPILE_IFELSE(
+ AC_LANG_PROGRAM([
+ #include <linux/if_tun.h>
+ int a = IFF_TAP;
+ ]),
+ [if_tun_h="default"],
+ [if_tun_h="no"]
+ )]
+ )
+
+ if test $if_tun_h = no; then
+ tinc_cv_linux_if_tun_h=none
+ else
+ tinc_cv_linux_if_tun_h="$if_tun_h"
+ fi
+ ])
+
+ if test $tinc_cv_linux_if_tun_h != none; then
+ AC_DEFINE(HAVE_TUNTAP, 1, [Universal tun/tap driver present])
+ if test $tinc_cv_linux_if_tun_h != default; then
+ AC_DEFINE_UNQUOTED(LINUX_IF_TUN_H, $tinc_cv_linux_if_tun_h, [Location of if_tun.h])
+ fi