diff --git a/lib/librte_ether/rte_flow.c b/lib/librte_ether/rte_flow.c
index f4fb607..46f430e 100644
--- a/lib/librte_ether/rte_flow.c
+++ b/lib/librte_ether/rte_flow.c
@@ -37,75 +37,14 @@
 #include <string.h>
 
 #include <rte_common.h>
+#include <rte_debug.h>
 #include <rte_errno.h>
 #include <rte_branch_prediction.h>
 #include "rte_ethdev.h"
+#include "rte_flow_conv.h"
 #include "rte_flow_driver.h"
 #include "rte_flow.h"
 
-/**
- * Flow elements description tables.
- */
-struct rte_flow_desc_data {
-	const char *name;
-	size_t size;
-};
-
-/** Generate flow_item[] entry. */
-#define MK_FLOW_ITEM(t, s) \
-	[RTE_FLOW_ITEM_TYPE_ ## t] = { \
-		.name = # t, \
-		.size = s, \
-	}
-
-/** Information about known flow pattern items. */
-static const struct rte_flow_desc_data rte_flow_desc_item[] = {
-	MK_FLOW_ITEM(END, 0),
-	MK_FLOW_ITEM(VOID, 0),
-	MK_FLOW_ITEM(INVERT, 0),
-	MK_FLOW_ITEM(ANY, sizeof(struct rte_flow_item_any)),
-	MK_FLOW_ITEM(PF, 0),
-	MK_FLOW_ITEM(VF, sizeof(struct rte_flow_item_vf)),
-	MK_FLOW_ITEM(PORT, sizeof(struct rte_flow_item_port)),
-	MK_FLOW_ITEM(RAW, sizeof(struct rte_flow_item_raw)), /* +pattern[] */
-	MK_FLOW_ITEM(ETH, sizeof(struct rte_flow_item_eth)),
-	MK_FLOW_ITEM(VLAN, sizeof(struct rte_flow_item_vlan)),
-	MK_FLOW_ITEM(IPV4, sizeof(struct rte_flow_item_ipv4)),
-	MK_FLOW_ITEM(IPV6, sizeof(struct rte_flow_item_ipv6)),
-	MK_FLOW_ITEM(ICMP, sizeof(struct rte_flow_item_icmp)),
-	MK_FLOW_ITEM(UDP, sizeof(struct rte_flow_item_udp)),
-	MK_FLOW_ITEM(TCP, sizeof(struct rte_flow_item_tcp)),
-	MK_FLOW_ITEM(SCTP, sizeof(struct rte_flow_item_sctp)),
-	MK_FLOW_ITEM(VXLAN, sizeof(struct rte_flow_item_vxlan)),
-	MK_FLOW_ITEM(MPLS, sizeof(struct rte_flow_item_mpls)),
-	MK_FLOW_ITEM(GRE, sizeof(struct rte_flow_item_gre)),
-	MK_FLOW_ITEM(E_TAG, sizeof(struct rte_flow_item_e_tag)),
-	MK_FLOW_ITEM(NVGRE, sizeof(struct rte_flow_item_nvgre)),
-};
-
-/** Generate flow_action[] entry. */
-#define MK_FLOW_ACTION(t, s) \
-	[RTE_FLOW_ACTION_TYPE_ ## t] = { \
-		.name = # t, \
-		.size = s, \
-	}
-
-/** Information about known flow actions. */
-static const struct rte_flow_desc_data rte_flow_desc_action[] = {
-	MK_FLOW_ACTION(END, 0),
-	MK_FLOW_ACTION(VOID, 0),
-	MK_FLOW_ACTION(PASSTHRU, 0),
-	MK_FLOW_ACTION(MARK, sizeof(struct rte_flow_action_mark)),
-	MK_FLOW_ACTION(FLAG, 0),
-	MK_FLOW_ACTION(QUEUE, sizeof(struct rte_flow_action_queue)),
-	MK_FLOW_ACTION(DROP, 0),
-	MK_FLOW_ACTION(COUNT, 0),
-	MK_FLOW_ACTION(DUP, sizeof(struct rte_flow_action_dup)),
-	MK_FLOW_ACTION(RSS, sizeof(struct rte_flow_action_rss)), /* +queue[] */
-	MK_FLOW_ACTION(PF, 0),
-	MK_FLOW_ACTION(VF, sizeof(struct rte_flow_action_vf)),
-};
-
 /* Get generic flow operations structure from a port. */
 const struct rte_flow_ops *
 rte_flow_ops_get(uint8_t port_id, struct rte_flow_error *error)
@@ -243,59 +182,39 @@ rte_flow_isolate(uint8_t port_id,
 				  NULL, rte_strerror(ENOSYS));
 }
 
-/** Compute storage space needed by item specification. */
-static void
-flow_item_spec_size(const struct rte_flow_item *item,
-		    size_t *size, size_t *pad)
-{
-	if (!item->spec) {
-		*size = 0;
-		goto empty;
-	}
-	switch (item->type) {
-		union {
-			const struct rte_flow_item_raw *raw;
-		} spec;
-
-	/* Not a fall-through */
-	case RTE_FLOW_ITEM_TYPE_RAW:
-		spec.raw = item->spec;
-		*size = offsetof(struct rte_flow_item_raw, pattern) +
-			spec.raw->length * sizeof(*spec.raw->pattern);
-		break;
-	default:
-		*size = rte_flow_desc_item[item->type].size;
-		break;
-	}
-empty:
-	*pad = RTE_ALIGN_CEIL(*size, sizeof(double)) - *size;
-}
-
-/** Compute storage space needed by action configuration. */
+/** Compute storage space needed for item->spec or action->conf. */
 static void
-flow_action_conf_size(const struct rte_flow_action *action,
-		      size_t *size, size_t *pad)
+rte_flow_conv_res_size(const struct rte_flow_conv_res *res, const void *obj,
+		       size_t *size, size_t *pad)
 {
-	if (!action->conf) {
+	if (!obj) {
 		*size = 0;
-		goto empty;
-	}
-	switch (action->type) {
-		union {
-			const struct rte_flow_action_rss *rss;
-		} conf;
-
-	/* Not a fall-through. */
-	case RTE_FLOW_ACTION_TYPE_RSS:
-		conf.rss = action->conf;
-		*size = offsetof(struct rte_flow_action_rss, queue) +
-			conf.rss->num * sizeof(*conf.rss->queue);
-		break;
-	default:
-		*size = rte_flow_desc_action[action->type].size;
-		break;
+	} else if (res->flex_off) {
+		void *flex_len_ptr =
+			(void *)((uintptr_t)obj + res->flex_len_off);
+		uint64_t flex_len = 0;
+
+		switch (res->flex_len_type) {
+		case sizeof(uint8_t):
+			flex_len = *(uint8_t *)flex_len_ptr;
+			break;
+		case sizeof(uint16_t):
+			flex_len = *(uint16_t *)flex_len_ptr;
+			break;
+		case sizeof(uint32_t):
+			flex_len = *(uint32_t *)flex_len_ptr;
+			break;
+		case sizeof(uint64_t):
+			flex_len = *(uint64_t *)flex_len_ptr;
+			break;
+		default:
+			RTE_ASSERT(!"unsupported flex_len_type in"
+				   " struct rte_flow_conv_res");
+		}
+		*size = res->flex_off + res->flex_elt_size * flex_len;
+	} else {
+		*size = res->size;
 	}
-empty:
 	*pad = RTE_ALIGN_CEIL(*size, sizeof(double)) - *size;
 }
 
@@ -315,15 +234,17 @@ rte_flow_conv_pattern(struct rte_flow_item *dst,
 
 store:
 	for (off = 0, i = 0; !num || i != num; ++i, ++src, ++dst) {
+		const struct rte_flow_conv_res *res =
+			&rte_flow_conv_res_item[src->type];
 		size_t spec;
 		size_t pad;
 
-		if ((size_t)src->type >= RTE_DIM(rte_flow_desc_item) ||
-		    !rte_flow_desc_item[src->type].name)
+		if ((size_t)src->type >= RTE_DIM(rte_flow_conv_res_item) ||
+		    !res->name)
 			goto notsup;
 		if (store)
 			*dst = (struct rte_flow_item){ .type = src->type, };
-		flow_item_spec_size(src, &spec, &pad);
+		rte_flow_conv_res_size(res, src->spec, &spec, &pad);
 		if (spec)
 			off = RTE_ALIGN_CEIL(off, sizeof(double));
 		if (src->spec) {
@@ -380,15 +301,17 @@ rte_flow_conv_actions(struct rte_flow_action *dst,
 
 store:
 	for (off = 0, i = 0; !num || i != num; ++i, ++src, ++dst) {
+		const struct rte_flow_conv_res *res =
+			&rte_flow_conv_res_action[src->type];
 		size_t conf;
 		size_t pad;
 
-		if ((size_t)src->type >= RTE_DIM(rte_flow_desc_action) ||
-		    !rte_flow_desc_action[src->type].name)
+		if ((size_t)src->type >= RTE_DIM(rte_flow_conv_res_action) ||
+		    !res->name)
 			goto notsup;
 		if (store)
 			*dst = (struct rte_flow_action){ .type = src->type, };
-		flow_action_conf_size(src, &conf, &pad);
+		rte_flow_conv_res_size(res, src->conf, &conf, &pad);
 		if (conf)
 			off = RTE_ALIGN_CEIL(off, sizeof(double));
 		if (store && conf)
@@ -474,11 +397,17 @@ rte_flow_conv_name(int is_action,
 		   struct rte_flow_error *error)
 {
 	const struct {
-		const struct rte_flow_desc_data *data;
+		const struct rte_flow_conv_res *data;
 		size_t num;
 	} res_data[2] = {
-		{ rte_flow_desc_item, RTE_DIM(rte_flow_desc_item), },
-		{ rte_flow_desc_action, RTE_DIM(rte_flow_desc_action), },
+		{
+			rte_flow_conv_res_item,
+			RTE_DIM(rte_flow_conv_res_item),
+		},
+		{
+			rte_flow_conv_res_action,
+			RTE_DIM(rte_flow_conv_res_action),
+		},
 	}, *const res = &res_data[!!is_action];
 	unsigned int obj_type = (uintptr_t)src;
 
@@ -498,11 +427,17 @@ rte_flow_conv_name_ptr(int is_action,
 		       struct rte_flow_error *error)
 {
 	const struct {
-		const struct rte_flow_desc_data *data;
+		const struct rte_flow_conv_res *data;
 		size_t num;
 	} res_data[2] = {
-		{ rte_flow_desc_item, RTE_DIM(rte_flow_desc_item), },
-		{ rte_flow_desc_action, RTE_DIM(rte_flow_desc_action), },
+		{
+			rte_flow_conv_res_item,
+			RTE_DIM(rte_flow_conv_res_item),
+		},
+		{
+			rte_flow_conv_res_action,
+			RTE_DIM(rte_flow_conv_res_action),
+		},
 	}, *const res = &res_data[!!is_action];
 	unsigned int obj_type = (uintptr_t)src;
 
diff --git a/lib/librte_ether/rte_flow_conv.h b/lib/librte_ether/rte_flow_conv.h
new file mode 100644
index 0000000..2244970
--- /dev/null
+++ b/lib/librte_ether/rte_flow_conv.h
@@ -0,0 +1,333 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright 2017 6WIND S.A.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of 6WIND S.A. nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * @file
+ * RTE generic flow API (internal)
+ *
+ * This file exports resources needed by rte_flow_conv().
+ */
+
+#ifndef RTE_FLOW_CONV_H_
+#define RTE_FLOW_CONV_H_
+
+#include <stddef.h>
+
+#include "rte_flow.h"
+
+/**
+ * This structure describes either a pattern item or an action as well as
+ * their associated specification or configuration structure.
+ */
+struct rte_flow_conv_res {
+	const char *name; /**< Object name. */
+	const void *mask; /**< Default mask for structure if relevant. */
+	size_t size; /**< Associated structure size. */
+	size_t flex_len_type; /**< Length field type for flexible array. */
+	size_t flex_len_off; /**< Length field offset for flexible array. */
+	size_t flex_elt_size; /**< Flexible array element size. */
+	size_t flex_off; /**< Flexible array field offset. */
+};
+
+/** Pattern items description table. */
+static const struct rte_flow_conv_res rte_flow_conv_res_item[] = {
+	[RTE_FLOW_ITEM_TYPE_END] = {
+		.name = "end",
+		.size = 0,
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_VOID] = {
+		.name = "void",
+		.size = 0,
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_INVERT] = {
+		.name = "invert",
+		.size = 0,
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_ANY] = {
+		.name = "any",
+		.size = sizeof(struct rte_flow_item_any),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_PF] = {
+		.name = "pf",
+		.size = 0,
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_VF] = {
+		.name = "vf",
+		.size = sizeof(struct rte_flow_item_vf),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_PORT] = {
+		.name = "port",
+		.size = sizeof(struct rte_flow_item_port),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_RAW] = {
+		.name = "raw",
+		.size = sizeof(struct rte_flow_item_raw),
+		.flex_len_type = sizeof(((struct rte_flow_item_raw *)0)->length),
+		.flex_len_off = offsetof(struct rte_flow_item_raw, length),
+		.flex_elt_size = sizeof(((struct rte_flow_item_raw *)0)->pattern[0]),
+		.flex_off = offsetof(struct rte_flow_item_raw, pattern),
+	},
+	[RTE_FLOW_ITEM_TYPE_ETH] = {
+		.name = "eth",
+		.size = sizeof(struct rte_flow_item_eth),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_VLAN] = {
+		.name = "vlan",
+		.size = sizeof(struct rte_flow_item_vlan),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_IPV4] = {
+		.name = "ipv4",
+		.size = sizeof(struct rte_flow_item_ipv4),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_IPV6] = {
+		.name = "ipv6",
+		.size = sizeof(struct rte_flow_item_ipv6),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_ICMP] = {
+		.name = "icmp",
+		.size = sizeof(struct rte_flow_item_icmp),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_UDP] = {
+		.name = "udp",
+		.size = sizeof(struct rte_flow_item_udp),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_TCP] = {
+		.name = "tcp",
+		.size = sizeof(struct rte_flow_item_tcp),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_SCTP] = {
+		.name = "sctp",
+		.size = sizeof(struct rte_flow_item_sctp),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_VXLAN] = {
+		.name = "vxlan",
+		.size = sizeof(struct rte_flow_item_vxlan),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_E_TAG] = {
+		.name = "e_tag",
+		.size = sizeof(struct rte_flow_item_e_tag),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_NVGRE] = {
+		.name = "nvgre",
+		.size = sizeof(struct rte_flow_item_nvgre),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_MPLS] = {
+		.name = "mpls",
+		.size = sizeof(struct rte_flow_item_mpls),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ITEM_TYPE_GRE] = {
+		.name = "gre",
+		.size = sizeof(struct rte_flow_item_gre),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+};
+
+/** Actions description table. */
+static const struct rte_flow_conv_res rte_flow_conv_res_action[] = {
+	[RTE_FLOW_ACTION_TYPE_END] = {
+		.name = "end",
+		.size = 0,
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ACTION_TYPE_VOID] = {
+		.name = "void",
+		.size = 0,
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ACTION_TYPE_PASSTHRU] = {
+		.name = "passthru",
+		.size = 0,
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ACTION_TYPE_MARK] = {
+		.name = "mark",
+		.size = sizeof(struct rte_flow_action_mark),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ACTION_TYPE_FLAG] = {
+		.name = "flag",
+		.size = 0,
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ACTION_TYPE_QUEUE] = {
+		.name = "queue",
+		.size = sizeof(struct rte_flow_action_queue),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ACTION_TYPE_DROP] = {
+		.name = "drop",
+		.size = 0,
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ACTION_TYPE_COUNT] = {
+		.name = "count",
+		.size = 0,
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ACTION_TYPE_DUP] = {
+		.name = "dup",
+		.size = sizeof(struct rte_flow_action_dup),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ACTION_TYPE_RSS] = {
+		.name = "rss",
+		.size = sizeof(struct rte_flow_action_rss),
+		.flex_len_type = sizeof(((struct rte_flow_action_rss *)0)->num),
+		.flex_len_off = offsetof(struct rte_flow_action_rss, num),
+		.flex_elt_size = sizeof(((struct rte_flow_action_rss *)0)->queue[0]),
+		.flex_off = offsetof(struct rte_flow_action_rss, queue),
+	},
+	[RTE_FLOW_ACTION_TYPE_PF] = {
+		.name = "pf",
+		.size = 0,
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+	[RTE_FLOW_ACTION_TYPE_VF] = {
+		.name = "vf",
+		.size = sizeof(struct rte_flow_action_vf),
+		.flex_len_type = 0,
+		.flex_len_off = 0,
+		.flex_elt_size = 0,
+		.flex_off = 0,
+	},
+};
+
+#endif /* RTE_FLOW_CONV_H_ */
