AC_DEFUN([DOVECOT_WANT_GSSAPI], [
  have_gssapi=no
  if test $want_gssapi != no; then
  	AC_CHECK_PROG(KRB5CONFIG, krb5-config, krb5-config, NO)
  	if test $KRB5CONFIG != NO; then
  		KRB5_LIBS="`$KRB5CONFIG --libs`"
  		KRB5_CFLAGS=`$KRB5CONFIG --cflags`
  		if ! $KRB5CONFIG --version gssapi 2>/dev/null > /dev/null; then
  		  # krb5-config doesn't support gssapi.
  		  AC_CHECK_LIB(gss, gss_acquire_cred, [
  		    # Solaris
  		    KRB5_LIBS="$KRB5_LIBS -lgss"
  		  ], [
  		    # failed
  		    KRB5_LIBS=
  		  ], $KRB5_LIBS)
  		else
  		  KRB5_LIBS="$KRB5_LIBS `$KRB5CONFIG --libs gssapi`"
  		  KRB5_CFLAGS="$KRB5_CFLAGS `$KRB5CONFIG --cflags gssapi`"
  		fi
  		if test "$KRB5_LIBS" != ""; then
  			AC_SUBST(KRB5_LIBS)
  			AC_SUBST(KRB5_CFLAGS)
  			
  			# Although krb5-config exists, all systems still don't
  			# have gssapi.h
  			old_CFLAGS=$CFLAGS
  			CFLAGS="$CFLAGS $KRB5_CFLAGS"
  			AC_CHECK_HEADER([gssapi/gssapi.h], [
  				AC_DEFINE(HAVE_GSSAPI_GSSAPI_H,, [GSSAPI headers in gssapi/gssapi.h])
  				have_gssapi=yes
  			])
  			AC_CHECK_HEADER([gssapi.h], [
  				AC_DEFINE(HAVE_GSSAPI_H,, [GSSAPI headers in gssapi.h])
  				have_gssapi=yes
  			])
  			if test $have_gssapi != no; then
  				if test $want_gssapi = plugin; then
  					have_gssapi=plugin
  				fi
  				AC_DEFINE(HAVE_GSSAPI,, [Build with GSSAPI support])
  				AC_CHECK_HEADERS(gssapi/gssapi_ext.h gssapi_krb5.h gssapi/gssapi_krb5.h)
  				AC_CHECK_LIB(gss, __gss_userok, [
  					AC_DEFINE(HAVE___GSS_USEROK,,
  						[Define if you have __gss_userok()])
  					KRB5_LIBS="$KRB5_LIBS -lgss"
  				],, $KRB5_LIBS)
  
  				# MIT has a #define for Heimdal acceptor_identity, but it's way too
  				# difficult to test for it..
  				old_LIBS=$LIBS
  				LIBS="$LIBS $KRB5_LIBS"
  				AC_CHECK_FUNCS(gsskrb5_register_acceptor_identity krb5_gss_register_acceptor_identity)
  				AC_CHECK_FUNCS(krb5_free_context)
  
  				# does the kerberos library support SPNEGO?
  				AC_CACHE_CHECK([whether GSSAPI supports SPNEGO],i_cv_gssapi_spnego,[
  				  AC_TRY_RUN([
  				    #ifdef HAVE_GSSAPI_H
  				    #  include <gssapi.h>
  				    #else
  				    #  include <gssapi/gssapi.h>
  				    #endif
  				    #include <krb5.h>
  				    #include <string.h>
  				    int main(void) {
  				      OM_uint32 minor_status;
  				      gss_OID_set mech_set;
  				      unsigned char spnego_oid[] = { 0x2b, 0x06, 0x01, 0x05, 0x05, 0x02 };
  				      unsigned int i;
      
  				      gss_indicate_mechs(&minor_status, &mech_set);
  				      for (i = 0; i < mech_set->count; i++) {
  					if (mech_set->elements[i].length == 6 &&
  					    memcmp(mech_set->elements[i].elements,
  						   spnego_oid, 6) == 0)
  					      return 0;
  				      }
  				      return 1;
  				    }
  				  ], [
  				    i_cv_gssapi_spnego=yes
  				  ], [
  				    i_cv_gssapi_spnego=no
  				  ])
  				])
  				if test "$i_cv_gssapi_spnego" = "yes"; then
  				  AC_DEFINE(HAVE_GSSAPI_SPNEGO,, [GSSAPI supports SPNEGO])
  				fi
  				LIBS=$old_LIBS
  
  				if test $want_gssapi != plugin; then
  				  AUTH_LIBS="$AUTH_LIBS $KRB5_LIBS"
  				  AUTH_CFLAGS="$AUTH_CFLAGS $KRB5_CFLAGS"
  				  AC_DEFINE(BUILTIN_GSSAPI,, [GSSAPI support is built in])
  				else
  				  have_gssapi_plugin=yes
  				fi
  			else
  			  if test $want_gssapi != auto; then
  			    AC_ERROR([Can't build with GSSAPI support: gssapi.h not found])
  			  fi
  			fi
  			CFLAGS=$old_CFLAGS
  		fi
  	else
  	  if test $want_gssapi != auto; then
  	    AC_ERROR([Can't build with GSSAPI support: krb5-config not found])
  	  fi
  	fi
  fi
  AM_CONDITIONAL(GSSAPI_PLUGIN, test "$have_gssapi_plugin" = "yes")
])