path: root/src/spdk/dpdk/lib/librte_mbuf/rte_mbuf.c

/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright(c) 2010-2014 Intel Corporation.
 * Copyright 2014 6WIND S.A.
 */

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdarg.h>
#include <inttypes.h>
#include <errno.h>
#include <ctype.h>
#include <sys/queue.h>

#include <rte_compat.h>
#include <rte_debug.h>
#include <rte_common.h>
#include <rte_log.h>
#include <rte_memory.h>
#include <rte_launch.h>
#include <rte_eal.h>
#include <rte_per_lcore.h>
#include <rte_lcore.h>
#include <rte_atomic.h>
#include <rte_branch_prediction.h>
#include <rte_mempool.h>
#include <rte_mbuf.h>
#include <rte_mbuf_pool_ops.h>
#include <rte_string_fns.h>
#include <rte_hexdump.h>
#include <rte_errno.h>
#include <rte_memcpy.h>

/*
 * pktmbuf pool constructor, given as a callback function to
 * rte_mempool_create(), or called directly if using
 * rte_mempool_create_empty()/rte_mempool_populate()
 */
void
rte_pktmbuf_pool_init(struct rte_mempool *mp, void *opaque_arg)
{
	struct rte_pktmbuf_pool_private *user_mbp_priv, *mbp_priv;
	struct rte_pktmbuf_pool_private default_mbp_priv;
	uint16_t roomsz;

	RTE_ASSERT(mp->elt_size >= sizeof(struct rte_mbuf));

	/* if no structure is provided, assume no mbuf private area */
	user_mbp_priv = opaque_arg;
	if (user_mbp_priv == NULL) {
		memset(&default_mbp_priv, 0, sizeof(default_mbp_priv));
		if (mp->elt_size > sizeof(struct rte_mbuf))
			roomsz = mp->elt_size - sizeof(struct rte_mbuf);
		else
			roomsz = 0;
		default_mbp_priv.mbuf_data_room_size = roomsz;
		user_mbp_priv = &default_mbp_priv;
	}

	RTE_ASSERT(mp->elt_size >= sizeof(struct rte_mbuf) +
		((user_mbp_priv->flags & RTE_PKTMBUF_POOL_F_PINNED_EXT_BUF) ?
			sizeof(struct rte_mbuf_ext_shared_info) :
			user_mbp_priv->mbuf_data_room_size) +
		user_mbp_priv->mbuf_priv_size);
	RTE_ASSERT((user_mbp_priv->flags &
		    ~RTE_PKTMBUF_POOL_F_PINNED_EXT_BUF) == 0);

	mbp_priv = rte_mempool_get_priv(mp);
	memcpy(mbp_priv, user_mbp_priv, sizeof(*mbp_priv));
}

/*
 * pktmbuf constructor, given as a callback function to
 * rte_mempool_obj_iter() or rte_mempool_create().
 * Set the fields of a packet mbuf to their default values.
 */
void
rte_pktmbuf_init(struct rte_mempool *mp,
		 __rte_unused void *opaque_arg,
		 void *_m,
		 __rte_unused unsigned i)
{
	struct rte_mbuf *m = _m;
	uint32_t mbuf_size, buf_len, priv_size;

	priv_size = rte_pktmbuf_priv_size(mp);
	mbuf_size = sizeof(struct rte_mbuf) + priv_size;
	buf_len = rte_pktmbuf_data_room_size(mp);

	RTE_ASSERT(RTE_ALIGN(priv_size, RTE_MBUF_PRIV_ALIGN) == priv_size);
	RTE_ASSERT(mp->elt_size >= mbuf_size);
	RTE_ASSERT(buf_len <= UINT16_MAX);

	memset(m, 0, mbuf_size);
	/* start of buffer is after mbuf structure and priv data */
	m->priv_size = priv_size;
	m->buf_addr = (char *)m + mbuf_size;
	m->buf_iova = rte_mempool_virt2iova(m) + mbuf_size;
	m->buf_len = (uint16_t)buf_len;

	/* keep some headroom between start of buffer and data */
	m->data_off = RTE_MIN(RTE_PKTMBUF_HEADROOM, (uint16_t)m->buf_len);

	/* init some constant fields */
	m->pool = mp;
	m->nb_segs = 1;
	m->port = MBUF_INVALID_PORT;
	rte_mbuf_refcnt_set(m, 1);
	m->next = NULL;
}

/*
 * @internal The callback routine called when reference counter in shinfo
 * for mbufs with pinned external buffer reaches zero. It means there is
 * no more reference to buffer backing mbuf and this one should be freed.
 * This routine is called for the regular (not with pinned external or
 * indirect buffer) mbufs on detaching from the mbuf with pinned external
 * buffer.
 */
static void
rte_pktmbuf_free_pinned_extmem(void *addr, void *opaque)
{
	struct rte_mbuf *m = opaque;

	RTE_SET_USED(addr);
	RTE_ASSERT(RTE_MBUF_HAS_EXTBUF(m));
	RTE_ASSERT(RTE_MBUF_HAS_PINNED_EXTBUF(m));
	RTE_ASSERT(m->shinfo->fcb_opaque == m);

	rte_mbuf_ext_refcnt_set(m->shinfo, 1);
	m->ol_flags = EXT_ATTACHED_MBUF;
	if (m->next != NULL) {
		m->next = NULL;
		m->nb_segs = 1;
	}
	rte_mbuf_raw_free(m);
}

/** The context to initialize the mbufs with pinned external buffers. */
struct rte_pktmbuf_extmem_init_ctx {
	const struct rte_pktmbuf_extmem *ext_mem; /* descriptor array. */
	unsigned int ext_num; /* number of descriptors in array. */
	unsigned int ext; /* loop descriptor index. */
	size_t off; /* loop buffer offset. */
};

/**
 * @internal Packet mbuf constructor for pools with pinned external memory.
 *
 * This function initializes some fields in the mbuf structure that are
 * not modified by the user once created (origin pool, buffer start
 * address, and so on). This function is given as a callback function to
 * rte_mempool_obj_iter() called from rte_mempool_create_extmem().
 *
 * @param mp
 *   The mempool from which mbufs originate.
 * @param opaque_arg
 *   A pointer to the rte_pktmbuf_extmem_init_ctx - initialization
 *   context structure
 * @param m
 *   The mbuf to initialize.
 * @param i
 *   The index of the mbuf in the pool table.
 */
static void
__rte_pktmbuf_init_extmem(struct rte_mempool *mp,
			  void *opaque_arg,
			  void *_m,
			  __rte_unused unsigned int i)
{
	struct rte_mbuf *m = _m;
	struct rte_pktmbuf_extmem_init_ctx *ctx = opaque_arg;
	const struct rte_pktmbuf_extmem *ext_mem;
	uint32_t mbuf_size, buf_len, priv_size;
	struct rte_mbuf_ext_shared_info *shinfo;

	priv_size = rte_pktmbuf_priv_size(mp);
	mbuf_size = sizeof(struct rte_mbuf) + priv_size;
	buf_len = rte_pktmbuf_data_room_size(mp);

	RTE_ASSERT(RTE_ALIGN(priv_size, RTE_MBUF_PRIV_ALIGN) == priv_size);
	RTE_ASSERT(mp->elt_size >= mbuf_size);
	RTE_ASSERT(buf_len <= UINT16_MAX);

	memset(m, 0, mbuf_size);
	m->priv_size = priv_size;
	m->buf_len = (uint16_t)buf_len;

	/* set the data buffer pointers to external memory */
	ext_mem = ctx->ext_mem + ctx->ext;

	RTE_ASSERT(ctx->ext < ctx->ext_num);
	RTE_ASSERT(ctx->off < ext_mem->buf_len);

	m->buf_addr = RTE_PTR_ADD(ext_mem->buf_ptr, ctx->off);
	m->buf_iova = ext_mem->buf_iova == RTE_BAD_IOVA ?
		      RTE_BAD_IOVA : (ext_mem->buf_iova + ctx->off);

	ctx->off += ext_mem->elt_size;
	if (ctx->off >= ext_mem->buf_len) {
		ctx->off = 0;
		++ctx->ext;
	}
	/* keep some headroom between start of buffer and data */
	m->data_off = RTE_MIN(RTE_PKTMBUF_HEADROOM, (uint16_t)m->buf_len);

	/* init some constant fields */
	m->pool = mp;
	m->nb_segs = 1;
	m->port = MBUF_INVALID_PORT;
	m->ol_flags = EXT_ATTACHED_MBUF;
	rte_mbuf_refcnt_set(m, 1);
	m->next = NULL;

	/* init external buffer shared info items */
	shinfo = RTE_PTR_ADD(m, mbuf_size);
	m->shinfo = shinfo;
	shinfo->free_cb = rte_pktmbuf_free_pinned_extmem;
	shinfo->fcb_opaque = m;
	rte_mbuf_ext_refcnt_set(shinfo, 1);
}

/* Helper to create a mbuf pool with given mempool ops name*/
struct rte_mempool *
rte_pktmbuf_pool_create_by_ops(const char *name, unsigned int n,
	unsigned int cache_size, uint16_t priv_size, uint16_t data_room_size,
	int socket_id, const char *ops_name)
{
	struct rte_mempool *mp;
	struct rte_pktmbuf_pool_private mbp_priv;
	const char *mp_ops_name = ops_name;
	unsigned elt_size;
	int ret;

	if (RTE_ALIGN(priv_size, RTE_MBUF_PRIV_ALIGN) != priv_size) {
		RTE_LOG(ERR, MBUF, "mbuf priv_size=%u is not aligned\n",
			priv_size);
		rte_errno = EINVAL;
		return NULL;
	}
	elt_size = sizeof(struct rte_mbuf) + (unsigned)priv_size +
		(unsigned)data_room_size;
	memset(&mbp_priv, 0, sizeof(mbp_priv));
	mbp_priv.mbuf_data_room_size = data_room_size;
	mbp_priv.mbuf_priv_size = priv_size;

	mp = rte_mempool_create_empty(name, n, elt_size, cache_size,
		 sizeof(struct rte_pktmbuf_pool_private), socket_id, 0);
	if (mp == NULL)
		return NULL;

	if (mp_ops_name == NULL)
		mp_ops_name = rte_mbuf_best_mempool_ops();
	ret = rte_mempool_set_ops_byname(mp, mp_ops_name, NULL);
	if (ret != 0) {
		RTE_LOG(ERR, MBUF, "error setting mempool handler\n");
		rte_mempool_free(mp);
		rte_errno = -ret;
		return NULL;
	}
	rte_pktmbuf_pool_init(mp, &mbp_priv);

	ret = rte_mempool_populate_default(mp);
	if (ret < 0) {
		rte_mempool_free(mp);
		rte_errno = -ret;
		return NULL;
	}

	rte_mempool_obj_iter(mp, rte_pktmbuf_init, NULL);

	return mp;
}

/* helper to create a mbuf pool */
struct rte_mempool *
rte_pktmbuf_pool_create(const char *name, unsigned int n,
	unsigned int cache_size, uint16_t priv_size, uint16_t data_room_size,
	int socket_id)
{
	return rte_pktmbuf_pool_create_by_ops(name, n, cache_size, priv_size,
			data_room_size, socket_id, NULL);
}

/* Helper to create a mbuf pool with pinned external data buffers. */
struct rte_mempool *
rte_pktmbuf_pool_create_extbuf(const char *name, unsigned int n,
	unsigned int cache_size, uint16_t priv_size,
	uint16_t data_room_size, int socket_id,
	const struct rte_pktmbuf_extmem *ext_mem,
	unsigned int ext_num)
{
	struct rte_mempool *mp;
	struct rte_pktmbuf_pool_private mbp_priv;
	struct rte_pktmbuf_extmem_init_ctx init_ctx;
	const char *mp_ops_name;
	unsigned int elt_size;
	unsigned int i, n_elts = 0;
	int ret;

	if (RTE_ALIGN(priv_size, RTE_MBUF_PRIV_ALIGN) != priv_size) {
		RTE_LOG(ERR, MBUF, "mbuf priv_size=%u is not aligned\n",
			priv_size);
		rte_errno = EINVAL;
		return NULL;
	}
	/* Check the external memory descriptors. */
	for (i = 0; i < ext_num; i++) {
		const struct rte_pktmbuf_extmem *extm = ext_mem + i;

		if (!extm->elt_size || !extm->buf_len || !extm->buf_ptr) {
			RTE_LOG(ERR, MBUF, "invalid extmem descriptor\n");
			rte_errno = EINVAL;
			return NULL;
		}
		if (data_room_size > extm->elt_size) {
			RTE_LOG(ERR, MBUF, "ext elt_size=%u is too small\n",
				priv_size);
			rte_errno = EINVAL;
			return NULL;
		}
		n_elts += extm->buf_len / extm->elt_size;
	}
	/* Check whether enough external memory provided. */
	if (n_elts < n) {
		RTE_LOG(ERR, MBUF, "not enough extmem\n");
		rte_errno = ENOMEM;
		return NULL;
	}
	elt_size = sizeof(struct rte_mbuf) +
		   (unsigned int)priv_size +
		   sizeof(struct rte_mbuf_ext_shared_info);

	memset(&mbp_priv, 0, sizeof(mbp_priv));
	mbp_priv.mbuf_data_room_size = data_room_size;
	mbp_priv.mbuf_priv_size = priv_size;
	mbp_priv.flags = RTE_PKTMBUF_POOL_F_PINNED_EXT_BUF;

	mp = rte_mempool_create_empty(name, n, elt_size, cache_size,
		 sizeof(struct rte_pktmbuf_pool_private), socket_id, 0);
	if (mp == NULL)
		return NULL;

	mp_ops_name = rte_mbuf_best_mempool_ops();
	ret = rte_mempool_set_ops_byname(mp, mp_ops_name, NULL);
	if (ret != 0) {
		RTE_LOG(ERR, MBUF, "error setting mempool handler\n");
		rte_mempool_free(mp);
		rte_errno = -ret;
		return NULL;
	}
	rte_pktmbuf_pool_init(mp, &mbp_priv);

	ret = rte_mempool_populate_default(mp);
	if (ret < 0) {
		rte_mempool_free(mp);
		rte_errno = -ret;
		return NULL;
	}

	init_ctx = (struct rte_pktmbuf_extmem_init_ctx){
		.ext_mem = ext_mem,
		.ext_num = ext_num,
		.ext = 0,
		.off = 0,
	};
	rte_mempool_obj_iter(mp, __rte_pktmbuf_init_extmem, &init_ctx);

	return mp;
}

/* do some sanity checks on a mbuf: panic if it fails */
void
rte_mbuf_sanity_check(const struct rte_mbuf *m, int is_header)
{
	const char *reason;

	if (rte_mbuf_check(m, is_header, &reason))
		rte_panic("%s\n", reason);
}

int rte_mbuf_check(const struct rte_mbuf *m, int is_header,
		   const char **reason)
{
	unsigned int nb_segs, pkt_len;

	if (m == NULL) {
		*reason = "mbuf is NULL";
		return -1;
	}

	/* generic checks */
	if (m->pool == NULL) {
		*reason = "bad mbuf pool";
		return -1;
	}
	if (m->buf_iova == 0) {
		*reason = "bad IO addr";
		return -1;
	}
	if (m->buf_addr == NULL) {
		*reason = "bad virt addr";
		return -1;
	}

	uint16_t cnt = rte_mbuf_refcnt_read(m);
	if ((cnt == 0) || (cnt == UINT16_MAX)) {
		*reason = "bad ref cnt";
		return -1;
	}

	/* nothing to check for sub-segments */
	if (is_header == 0)
		return 0;

	/* data_len is supposed to be not more than pkt_len */
	if (m->data_len > m->pkt_len) {
		*reason = "bad data_len";
		return -1;
	}

	nb_segs = m->nb_segs;
	pkt_len = m->pkt_len;

	do {
		if (m->data_off > m->buf_len) {
			*reason = "data offset too big in mbuf segment";
			return -1;
		}
		if (m->data_off + m->data_len > m->buf_len) {
			*reason = "data length too big in mbuf segment";
			return -1;
		}
		nb_segs -= 1;
		pkt_len -= m->data_len;
	} while ((m = m->next) != NULL);

	if (nb_segs) {
		*reason = "bad nb_segs";
		return -1;
	}
	if (pkt_len) {
		*reason = "bad pkt_len";
		return -1;
	}

	return 0;
}

/**
 * @internal helper function for freeing a bulk of packet mbuf segments
 * via an array holding the packet mbuf segments from the same mempool
 * pending to be freed.
 *
 * @param m
 *  The packet mbuf segment to be freed.
 * @param pending
 *  Pointer to the array of packet mbuf segments pending to be freed.
 * @param nb_pending
 *  Pointer to the number of elements held in the array.
 * @param pending_sz
 *  Number of elements the array can hold.
 *  Note: The compiler should optimize this parameter away when using a
 *  constant value, such as RTE_PKTMBUF_FREE_PENDING_SZ.
 */
static void
__rte_pktmbuf_free_seg_via_array(struct rte_mbuf *m,
	struct rte_mbuf ** const pending, unsigned int * const nb_pending,
	const unsigned int pending_sz)
{
	m = rte_pktmbuf_prefree_seg(m);
	if (likely(m != NULL)) {
		if (*nb_pending == pending_sz ||
		    (*nb_pending > 0 && m->pool != pending[0]->pool)) {
			rte_mempool_put_bulk(pending[0]->pool,
					(void **)pending, *nb_pending);
			*nb_pending = 0;
		}

		pending[(*nb_pending)++] = m;
	}
}

/**
 * Size of the array holding mbufs from the same mempool pending to be freed
 * in bulk.
 */
#define RTE_PKTMBUF_FREE_PENDING_SZ 64

/* Free a bulk of packet mbufs back into their original mempools. */
void rte_pktmbuf_free_bulk(struct rte_mbuf **mbufs, unsigned int count)
{
	struct rte_mbuf *m, *m_next, *pending[RTE_PKTMBUF_FREE_PENDING_SZ];
	unsigned int idx, nb_pending = 0;

	for (idx = 0; idx < count; idx++) {
		m = mbufs[idx];
		if (unlikely(m == NULL))
			continue;

		__rte_mbuf_sanity_check(m, 1);

		do {
			m_next = m->next;
			__rte_pktmbuf_free_seg_via_array(m,
					pending, &nb_pending,
					RTE_PKTMBUF_FREE_PENDING_SZ);
			m = m_next;
		} while (m != NULL);
	}

	if (nb_pending > 0)
		rte_mempool_put_bulk(pending[0]->pool, (void **)pending, nb_pending);
}

/* Creates a shallow copy of mbuf */
struct rte_mbuf *
rte_pktmbuf_clone(struct rte_mbuf *md, struct rte_mempool *mp)
{
	struct rte_mbuf *mc, *mi, **prev;
	uint32_t pktlen;
	uint16_t nseg;

	mc = rte_pktmbuf_alloc(mp);
	if (unlikely(mc == NULL))
		return NULL;

	mi = mc;
	prev = &mi->next;
	pktlen = md->pkt_len;
	nseg = 0;

	do {
		nseg++;
		rte_pktmbuf_attach(mi, md);
		*prev = mi;
		prev = &mi->next;
	} while ((md = md->next) != NULL &&
	    (mi = rte_pktmbuf_alloc(mp)) != NULL);

	*prev = NULL;
	mc->nb_segs = nseg;
	mc->pkt_len = pktlen;

	/* Allocation of new indirect segment failed */
	if (unlikely(mi == NULL)) {
		rte_pktmbuf_free(mc);
		return NULL;
	}

	__rte_mbuf_sanity_check(mc, 1);
	return mc;
}

/* convert multi-segment mbuf to single mbuf */
int
__rte_pktmbuf_linearize(struct rte_mbuf *mbuf)
{
	size_t seg_len, copy_len;
	struct rte_mbuf *m;
	struct rte_mbuf *m_next;
	char *buffer;

	/* Extend first segment to the total packet length */
	copy_len = rte_pktmbuf_pkt_len(mbuf) - rte_pktmbuf_data_len(mbuf);

	if (unlikely(copy_len > rte_pktmbuf_tailroom(mbuf)))
		return -1;

	buffer = rte_pktmbuf_mtod_offset(mbuf, char *, mbuf->data_len);
	mbuf->data_len = (uint16_t)(mbuf->pkt_len);

	/* Append data from next segments to the first one */
	m = mbuf->next;
	while (m != NULL) {
		m_next = m->next;

		seg_len = rte_pktmbuf_data_len(m);
		rte_memcpy(buffer, rte_pktmbuf_mtod(m, char *), seg_len);
		buffer += seg_len;

		rte_pktmbuf_free_seg(m);
		m = m_next;
	}

	mbuf->next = NULL;
	mbuf->nb_segs = 1;

	return 0;
}

/* Create a deep copy of mbuf */
struct rte_mbuf *
rte_pktmbuf_copy(const struct rte_mbuf *m, struct rte_mempool *mp,
		 uint32_t off, uint32_t len)
{
	const struct rte_mbuf *seg = m;
	struct rte_mbuf *mc, *m_last, **prev;

	/* garbage in check */
	__rte_mbuf_sanity_check(m, 1);

	/* check for request to copy at offset past end of mbuf */
	if (unlikely(off >= m->pkt_len))
		return NULL;

	mc = rte_pktmbuf_alloc(mp);
	if (unlikely(mc == NULL))
		return NULL;

	/* truncate requested length to available data */
	if (len > m->pkt_len - off)
		len = m->pkt_len - off;

	__rte_pktmbuf_copy_hdr(mc, m);

	/* copied mbuf is not indirect or external */
	mc->ol_flags = m->ol_flags & ~(IND_ATTACHED_MBUF|EXT_ATTACHED_MBUF);

	prev = &mc->next;
	m_last = mc;
	while (len > 0) {
		uint32_t copy_len;

		/* skip leading mbuf segments */
		while (off >= seg->data_len) {
			off -= seg->data_len;
			seg = seg->next;
		}

		/* current buffer is full, chain a new one */
		if (rte_pktmbuf_tailroom(m_last) == 0) {
			m_last = rte_pktmbuf_alloc(mp);
			if (unlikely(m_last == NULL)) {
				rte_pktmbuf_free(mc);
				return NULL;
			}
			++mc->nb_segs;
			*prev = m_last;
			prev = &m_last->next;
		}

		/*
		 * copy the min of data in input segment (seg)
		 * vs space available in output (m_last)
		 */
		copy_len = RTE_MIN(seg->data_len - off, len);
		if (copy_len > rte_pktmbuf_tailroom(m_last))
			copy_len = rte_pktmbuf_tailroom(m_last);

		/* append from seg to m_last */
		rte_memcpy(rte_pktmbuf_mtod_offset(m_last, char *,
						   m_last->data_len),
			   rte_pktmbuf_mtod_offset(seg, char *, off),
			   copy_len);

		/* update offsets and lengths */
		m_last->data_len += copy_len;
		mc->pkt_len += copy_len;
		off += copy_len;
		len -= copy_len;
	}

	/* garbage out check */
	__rte_mbuf_sanity_check(mc, 1);
	return mc;
}

/* dump a mbuf on console */
void
rte_pktmbuf_dump(FILE *f, const struct rte_mbuf *m, unsigned dump_len)
{
	unsigned int len;
	unsigned int nb_segs;

	__rte_mbuf_sanity_check(m, 1);

	fprintf(f, "dump mbuf at %p, iova=%#"PRIx64", buf_len=%u\n",
		m, m->buf_iova, m->buf_len);
	fprintf(f, "  pkt_len=%u, ol_flags=%#"PRIx64", nb_segs=%u, port=%u",
		m->pkt_len, m->ol_flags, m->nb_segs, m->port);

	if (m->ol_flags & (PKT_RX_VLAN | PKT_TX_VLAN))
		fprintf(f, ", vlan_tci=%u", m->vlan_tci);

	fprintf(f, ", ptype=%#"PRIx32"\n", m->packet_type);

	nb_segs = m->nb_segs;

	while (m && nb_segs != 0) {
		__rte_mbuf_sanity_check(m, 0);

		fprintf(f, "  segment at %p, data=%p, len=%u, off=%u, refcnt=%u\n",
			m, rte_pktmbuf_mtod(m, void *),
			m->data_len, m->data_off, rte_mbuf_refcnt_read(m));

		len = dump_len;
		if (len > m->data_len)
			len = m->data_len;
		if (len != 0)
			rte_hexdump(f, NULL, rte_pktmbuf_mtod(m, void *), len);
		dump_len -= len;
		m = m->next;
		nb_segs --;
	}
}

/* read len data bytes in a mbuf at specified offset (internal) */
const void *__rte_pktmbuf_read(const struct rte_mbuf *m, uint32_t off,
	uint32_t len, void *buf)
{
	const struct rte_mbuf *seg = m;
	uint32_t buf_off = 0, copy_len;

	if (off + len > rte_pktmbuf_pkt_len(m))
		return NULL;

	while (off >= rte_pktmbuf_data_len(seg)) {
		off -= rte_pktmbuf_data_len(seg);
		seg = seg->next;
	}

	if (off + len <= rte_pktmbuf_data_len(seg))
		return rte_pktmbuf_mtod_offset(seg, char *, off);

	/* rare case: header is split among several segments */
	while (len > 0) {
		copy_len = rte_pktmbuf_data_len(seg) - off;
		if (copy_len > len)
			copy_len = len;
		rte_memcpy((char *)buf + buf_off,
			rte_pktmbuf_mtod_offset(seg, char *, off), copy_len);
		off = 0;
		buf_off += copy_len;
		len -= copy_len;
		seg = seg->next;
	}

	return buf;
}

/*
 * Get the name of a RX offload flag. Must be kept synchronized with flag
 * definitions in rte_mbuf.h.
 */
const char *rte_get_rx_ol_flag_name(uint64_t mask)
{
	switch (mask) {
	case PKT_RX_VLAN: return "PKT_RX_VLAN";
	case PKT_RX_RSS_HASH: return "PKT_RX_RSS_HASH";
	case PKT_RX_FDIR: return "PKT_RX_FDIR";
	case PKT_RX_L4_CKSUM_BAD: return "PKT_RX_L4_CKSUM_BAD";
	case PKT_RX_L4_CKSUM_GOOD: return "PKT_RX_L4_CKSUM_GOOD";
	case PKT_RX_L4_CKSUM_NONE: return "PKT_RX_L4_CKSUM_NONE";
	case PKT_RX_IP_CKSUM_BAD: return "PKT_RX_IP_CKSUM_BAD";
	case PKT_RX_IP_CKSUM_GOOD: return "PKT_RX_IP_CKSUM_GOOD";
	case PKT_RX_IP_CKSUM_NONE: return "PKT_RX_IP_CKSUM_NONE";
	case PKT_RX_EIP_CKSUM_BAD: return "PKT_RX_EIP_CKSUM_BAD";
	case PKT_RX_VLAN_STRIPPED: return "PKT_RX_VLAN_STRIPPED";
	case PKT_RX_IEEE1588_PTP: return "PKT_RX_IEEE1588_PTP";
	case PKT_RX_IEEE1588_TMST: return "PKT_RX_IEEE1588_TMST";
	case PKT_RX_FDIR_ID: return "PKT_RX_FDIR_ID";
	case PKT_RX_FDIR_FLX: return "PKT_RX_FDIR_FLX";
	case PKT_RX_QINQ_STRIPPED: return "PKT_RX_QINQ_STRIPPED";
	case PKT_RX_QINQ: return "PKT_RX_QINQ";
	case PKT_RX_LRO: return "PKT_RX_LRO";
	case PKT_RX_TIMESTAMP: return "PKT_RX_TIMESTAMP";
	case PKT_RX_SEC_OFFLOAD: return "PKT_RX_SEC_OFFLOAD";
	case PKT_RX_SEC_OFFLOAD_FAILED: return "PKT_RX_SEC_OFFLOAD_FAILED";
	case PKT_RX_OUTER_L4_CKSUM_BAD: return "PKT_RX_OUTER_L4_CKSUM_BAD";
	case PKT_RX_OUTER_L4_CKSUM_GOOD: return "PKT_RX_OUTER_L4_CKSUM_GOOD";
	case PKT_RX_OUTER_L4_CKSUM_INVALID:
		return "PKT_RX_OUTER_L4_CKSUM_INVALID";

	default: return NULL;
	}
}

struct flag_mask {
	uint64_t flag;
	uint64_t mask;
	const char *default_name;
};

/* write the list of rx ol flags in buffer buf */
int
rte_get_rx_ol_flag_list(uint64_t mask, char *buf, size_t buflen)
{
	const struct flag_mask rx_flags[] = {
		{ PKT_RX_VLAN, PKT_RX_VLAN, NULL },
		{ PKT_RX_RSS_HASH, PKT_RX_RSS_HASH, NULL },
		{ PKT_RX_FDIR, PKT_RX_FDIR, NULL },
		{ PKT_RX_L4_CKSUM_BAD, PKT_RX_L4_CKSUM_MASK, NULL },
		{ PKT_RX_L4_CKSUM_GOOD, PKT_RX_L4_CKSUM_MASK, NULL },
		{ PKT_RX_L4_CKSUM_NONE, PKT_RX_L4_CKSUM_MASK, NULL },
		{ PKT_RX_L4_CKSUM_UNKNOWN, PKT_RX_L4_CKSUM_MASK,
		  "PKT_RX_L4_CKSUM_UNKNOWN" },
		{ PKT_RX_IP_CKSUM_BAD, PKT_RX_IP_CKSUM_MASK, NULL },
		{ PKT_RX_IP_CKSUM_GOOD, PKT_RX_IP_CKSUM_MASK, NULL },
		{ PKT_RX_IP_CKSUM_NONE, PKT_RX_IP_CKSUM_MASK, NULL },
		{ PKT_RX_IP_CKSUM_UNKNOWN, PKT_RX_IP_CKSUM_MASK,
		  "PKT_RX_IP_CKSUM_UNKNOWN" },
		{ PKT_RX_EIP_CKSUM_BAD, PKT_RX_EIP_CKSUM_BAD, NULL },
		{ PKT_RX_VLAN_STRIPPED, PKT_RX_VLAN_STRIPPED, NULL },
		{ PKT_RX_IEEE1588_PTP, PKT_RX_IEEE1588_PTP, NULL },
		{ PKT_RX_IEEE1588_TMST, PKT_RX_IEEE1588_TMST, NULL },
		{ PKT_RX_FDIR_ID, PKT_RX_FDIR_ID, NULL },
		{ PKT_RX_FDIR_FLX, PKT_RX_FDIR_FLX, NULL },
		{ PKT_RX_QINQ_STRIPPED, PKT_RX_QINQ_STRIPPED, NULL },
		{ PKT_RX_LRO, PKT_RX_LRO, NULL },
		{ PKT_RX_TIMESTAMP, PKT_RX_TIMESTAMP, NULL },
		{ PKT_RX_SEC_OFFLOAD, PKT_RX_SEC_OFFLOAD, NULL },
		{ PKT_RX_SEC_OFFLOAD_FAILED, PKT_RX_SEC_OFFLOAD_FAILED, NULL },
		{ PKT_RX_QINQ, PKT_RX_QINQ, NULL },
		{ PKT_RX_OUTER_L4_CKSUM_BAD, PKT_RX_OUTER_L4_CKSUM_MASK, NULL },
		{ PKT_RX_OUTER_L4_CKSUM_GOOD, PKT_RX_OUTER_L4_CKSUM_MASK,
		  NULL },
		{ PKT_RX_OUTER_L4_CKSUM_INVALID, PKT_RX_OUTER_L4_CKSUM_MASK,
		  NULL },
		{ PKT_RX_OUTER_L4_CKSUM_UNKNOWN, PKT_RX_OUTER_L4_CKSUM_MASK,
		  "PKT_RX_OUTER_L4_CKSUM_UNKNOWN" },
	};
	const char *name;
	unsigned int i;
	int ret;

	if (buflen == 0)
		return -1;

	buf[0] = '\0';
	for (i = 0; i < RTE_DIM(rx_flags); i++) {
		if ((mask & rx_flags[i].mask) != rx_flags[i].flag)
			continue;
		name = rte_get_rx_ol_flag_name(rx_flags[i].flag);
		if (name == NULL)
			name = rx_flags[i].default_name;
		ret = snprintf(buf, buflen, "%s ", name);
		if (ret < 0)
			return -1;
		if ((size_t)ret >= buflen)
			return -1;
		buf += ret;
		buflen -= ret;
	}

	return 0;
}

/*
 * Get the name of a TX offload flag. Must be kept synchronized with flag
 * definitions in rte_mbuf.h.
 */
const char *rte_get_tx_ol_flag_name(uint64_t mask)
{
	switch (mask) {
	case PKT_TX_VLAN: return "PKT_TX_VLAN";
	case PKT_TX_IP_CKSUM: return "PKT_TX_IP_CKSUM";
	case PKT_TX_TCP_CKSUM: return "PKT_TX_TCP_CKSUM";
	case PKT_TX_SCTP_CKSUM: return "PKT_TX_SCTP_CKSUM";
	case PKT_TX_UDP_CKSUM: return "PKT_TX_UDP_CKSUM";
	case PKT_TX_IEEE1588_TMST: return "PKT_TX_IEEE1588_TMST";
	case PKT_TX_TCP_SEG: return "PKT_TX_TCP_SEG";
	case PKT_TX_IPV4: return "PKT_TX_IPV4";
	case PKT_TX_IPV6: return "PKT_TX_IPV6";
	case PKT_TX_OUTER_IP_CKSUM: return "PKT_TX_OUTER_IP_CKSUM";
	case PKT_TX_OUTER_IPV4: return "PKT_TX_OUTER_IPV4";
	case PKT_TX_OUTER_IPV6: return "PKT_TX_OUTER_IPV6";
	case PKT_TX_TUNNEL_VXLAN: return "PKT_TX_TUNNEL_VXLAN";
	case PKT_TX_TUNNEL_GTP: return "PKT_TX_TUNNEL_GTP";
	case PKT_TX_TUNNEL_GRE: return "PKT_TX_TUNNEL_GRE";
	case PKT_TX_TUNNEL_IPIP: return "PKT_TX_TUNNEL_IPIP";
	case PKT_TX_TUNNEL_GENEVE: return "PKT_TX_TUNNEL_GENEVE";
	case PKT_TX_TUNNEL_MPLSINUDP: return "PKT_TX_TUNNEL_MPLSINUDP";
	case PKT_TX_TUNNEL_VXLAN_GPE: return "PKT_TX_TUNNEL_VXLAN_GPE";
	case PKT_TX_TUNNEL_IP: return "PKT_TX_TUNNEL_IP";
	case PKT_TX_TUNNEL_UDP: return "PKT_TX_TUNNEL_UDP";
	case PKT_TX_QINQ: return "PKT_TX_QINQ";
	case PKT_TX_MACSEC: return "PKT_TX_MACSEC";
	case PKT_TX_SEC_OFFLOAD: return "PKT_TX_SEC_OFFLOAD";
	case PKT_TX_UDP_SEG: return "PKT_TX_UDP_SEG";
	case PKT_TX_OUTER_UDP_CKSUM: return "PKT_TX_OUTER_UDP_CKSUM";
	default: return NULL;
	}
}

/* write the list of tx ol flags in buffer buf */
int
rte_get_tx_ol_flag_list(uint64_t mask, char *buf, size_t buflen)
{
	const struct flag_mask tx_flags[] = {
		{ PKT_TX_VLAN, PKT_TX_VLAN, NULL },
		{ PKT_TX_IP_CKSUM, PKT_TX_IP_CKSUM, NULL },
		{ PKT_TX_TCP_CKSUM, PKT_TX_L4_MASK, NULL },
		{ PKT_TX_SCTP_CKSUM, PKT_TX_L4_MASK, NULL },
		{ PKT_TX_UDP_CKSUM, PKT_TX_L4_MASK, NULL },
		{ PKT_TX_L4_NO_CKSUM, PKT_TX_L4_MASK, "PKT_TX_L4_NO_CKSUM" },
		{ PKT_TX_IEEE1588_TMST, PKT_TX_IEEE1588_TMST, NULL },
		{ PKT_TX_TCP_SEG, PKT_TX_TCP_SEG, NULL },
		{ PKT_TX_IPV4, PKT_TX_IPV4, NULL },
		{ PKT_TX_IPV6, PKT_TX_IPV6, NULL },
		{ PKT_TX_OUTER_IP_CKSUM, PKT_TX_OUTER_IP_CKSUM, NULL },
		{ PKT_TX_OUTER_IPV4, PKT_TX_OUTER_IPV4, NULL },
		{ PKT_TX_OUTER_IPV6, PKT_TX_OUTER_IPV6, NULL },
		{ PKT_TX_TUNNEL_VXLAN, PKT_TX_TUNNEL_MASK, NULL },
		{ PKT_TX_TUNNEL_GTP, PKT_TX_TUNNEL_MASK, NULL },
		{ PKT_TX_TUNNEL_GRE, PKT_TX_TUNNEL_MASK, NULL },
		{ PKT_TX_TUNNEL_IPIP, PKT_TX_TUNNEL_MASK, NULL },
		{ PKT_TX_TUNNEL_GENEVE, PKT_TX_TUNNEL_MASK, NULL },
		{ PKT_TX_TUNNEL_MPLSINUDP, PKT_TX_TUNNEL_MASK, NULL },
		{ PKT_TX_TUNNEL_VXLAN_GPE, PKT_TX_TUNNEL_MASK, NULL },
		{ PKT_TX_TUNNEL_IP, PKT_TX_TUNNEL_MASK, NULL },
		{ PKT_TX_TUNNEL_UDP, PKT_TX_TUNNEL_MASK, NULL },
		{ PKT_TX_QINQ, PKT_TX_QINQ, NULL },
		{ PKT_TX_MACSEC, PKT_TX_MACSEC, NULL },
		{ PKT_TX_SEC_OFFLOAD, PKT_TX_SEC_OFFLOAD, NULL },
		{ PKT_TX_UDP_SEG, PKT_TX_UDP_SEG, NULL },
		{ PKT_TX_OUTER_UDP_CKSUM, PKT_TX_OUTER_UDP_CKSUM, NULL },
	};
	const char *name;
	unsigned int i;
	int ret;

	if (buflen == 0)
		return -1;

	buf[0] = '\0';
	for (i = 0; i < RTE_DIM(tx_flags); i++) {
		if ((mask & tx_flags[i].mask) != tx_flags[i].flag)
			continue;
		name = rte_get_tx_ol_flag_name(tx_flags[i].flag);
		if (name == NULL)
			name = tx_flags[i].default_name;
		ret = snprintf(buf, buflen, "%s ", name);
		if (ret < 0)
			return -1;
		if ((size_t)ret >= buflen)
			return -1;
		buf += ret;
		buflen -= ret;
	}

	return 0;
}