* datapath. */
#include <assert.h>
+#include "openflow/openflow.h"
#include "dpif.h"
+#include "util.h"
#ifdef __cplusplus
extern "C" {
/* Attempts to receive a message from 'dpif'. If successful, stores the
* message into '*packetp'. The message, if one is received, must begin
- * with 'struct odp_msg' as a header. Only messages of the types selected
- * with the set_listen_mask member function should be received.
+ * with 'struct odp_msg' as a header, and must have at least
+ * DPIF_RECV_MSG_PADDING bytes of headroom (allocated using
+ * e.g. ofpbuf_reserve()). Only messages of the types selected with the
+ * set_listen_mask member function should be received.
*
* This function must not block. If no message is ready to be received
* when it is called, it should return EAGAIN without blocking. */
void (*recv_wait)(struct dpif *dpif);
};
+/* Minimum number of bytes of headroom for a packet returned by the 'recv'
+ * member function (see above). This headroom allows "struct odp_msg" to be
+ * replaced by "struct ofp_packet_in" without copying the buffer. */
+#define DPIF_RECV_MSG_PADDING (sizeof(struct ofp_packet_in) \
+ - sizeof(struct odp_msg))
+BUILD_ASSERT_DECL(sizeof(struct ofp_packet_in) > sizeof(struct odp_msg));
+BUILD_ASSERT_DECL(DPIF_RECV_MSG_PADDING % 4 == 0);
+
extern const struct dpif_class dpif_linux_class;
extern const struct dpif_class dpif_netdev_class;