Portably check for IPSEC_* constants (defined in ipsec.h).

The problem is that FreeBSD defines them as #defines whereas Linux defines them as enums.

configure.in

@@ -839,6 +839,36 @@ AC_CHECK_MEMBERS([struct sadb_x_policy.sadb_x_policy_priority], [], [],
 	#endif
 ])
 
+AC_MSG_CHECKING([for IPSEC_MODE_BEET])
+AC_TRY_COMPILE(
+	[#ifdef HAVE_NETIPSEC_IPSEC_H
+	#include <netipsec/ipsec.h>
+	#elif defined(HAVE_NETINET6_IPSEC_H)
+	#include <netinet6/ipsec.h>
+	#else
+	#include <linux/ipsec.h>
+	#endif],
+	[int mode = IPSEC_MODE_BEET;
+	 return mode;],
+	[AC_MSG_RESULT([yes]); AC_DEFINE([HAVE_IPSEC_MODE_BEET])],
+	[AC_MSG_RESULT([no])]
+)
+
+AC_MSG_CHECKING([for IPSEC_DIR_FWD])
+AC_TRY_COMPILE(
+	[#ifdef HAVE_NETIPSEC_IPSEC_H
+	#include <netipsec/ipsec.h>
+	#elif defined(HAVE_NETINET6_IPSEC_H)
+	#include <netinet6/ipsec.h>
+	#else
+	#include <linux/ipsec.h>
+	#endif],
+	[int dir = IPSEC_DIR_FWD;
+	 return dir;],
+	[AC_MSG_RESULT([yes]); AC_DEFINE([HAVE_IPSEC_DIR_FWD])],
+	[AC_MSG_RESULT([no])]
+)
+
 AC_MSG_CHECKING([for gcc atomic operations])
 AC_TRY_RUN(
 [

src/charon/plugins/kernel_pfkey/kernel_pfkey_ipsec.c

@@ -442,7 +442,7 @@ static u_int8_t mode2kernel(ipsec_mode_t mode)
 			return IPSEC_MODE_TRANSPORT;
 		case MODE_TUNNEL:
 			return IPSEC_MODE_TUNNEL;
-#ifdef IPSEC_MODE_BEET
+#ifdef HAVE_IPSEC_MODE_BEET
 		case MODE_BEET:
 			return IPSEC_MODE_BEET;
 #endif
@@ -462,7 +462,7 @@ static u_int8_t dir2kernel(policy_dir_t dir)
 			return IPSEC_DIR_INBOUND;
 		case POLICY_OUT:
 			return IPSEC_DIR_OUTBOUND;
-#ifdef IPSEC_DIR_FWD
+#ifdef HAVE_IPSEC_DIR_FWD
 		case POLICY_FWD:
 			return IPSEC_DIR_FWD;
 #endif
@@ -483,7 +483,7 @@ static policy_dir_t kernel2dir(u_int8_t  dir)
 			return POLICY_IN;
 		case IPSEC_DIR_OUTBOUND:
 			return POLICY_OUT;
-#ifdef IPSEC_DIR_FWD
+#ifdef HAVE_IPSEC_DIR_FWD
 		case IPSEC_DIR_FWD:
 			return POLICY_FWD;
 #endif