[dpdk-dev] [PATCH v3 4/6] mbuf: add a pktmbuf copy routine

[Stephen Hemminger <stephen@networkplumber.org>]

This is a commonly used operation that surprisingly the
DPDK has not supported. The new rte_pktmbuf_copy does a
deep copy of packet. This is a complete copy including
meta-data.

It handles the case where the source mbuf comes from a pool
with larger data area than the destination pool. The routine
also has options for skipping data, or truncating at a fixed
length.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/librte_mbuf/rte_mbuf.c           | 74 ++++++++++++++++++++++++++++
 lib/librte_mbuf/rte_mbuf.h           | 26 ++++++++++
 lib/librte_mbuf/rte_mbuf_version.map |  1 +
 3 files changed, 101 insertions(+)

diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
index 9a1a1b5f9468..901df0192d2e 100644
--- a/lib/librte_mbuf/rte_mbuf.c
+++ b/lib/librte_mbuf/rte_mbuf.c
@@ -321,6 +321,80 @@ __rte_pktmbuf_linearize(struct rte_mbuf *mbuf)
 	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;
+
+	if (unlikely(off >= m->pkt_len))
+		return NULL;
+
+	mc = rte_pktmbuf_alloc(mp);
+	if (unlikely(mc == NULL))
+		return NULL;
+
+	if (len > m->pkt_len - off)
+		len = m->pkt_len - off;
+
+	/* clone meta data from original */
+	mc->port = m->port;
+	mc->vlan_tci = m->vlan_tci;
+	mc->vlan_tci_outer = m->vlan_tci_outer;
+	mc->tx_offload = m->tx_offload;
+	mc->hash = m->hash;
+	mc->packet_type = m->packet_type;
+	mc->timestamp = m->timestamp;
+
+	/* copy private data (if any) */
+	rte_memcpy(mc + 1, m + 1,
+		   rte_pktmbuf_priv_size(mp));
+
+	prev = &mc->next;
+	m_last = mc;
+	while (len > 0) {
+		uint32_t copy_len;
+
+		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_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);
+
+		m_last->data_len += copy_len;
+		mc->pkt_len += copy_len;
+		off += copy_len;
+		len -= copy_len;
+	}
+
+	__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)
diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index 6133f12172ae..b860d570ef20 100644
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -1927,6 +1927,32 @@ static inline void rte_pktmbuf_free(struct rte_mbuf *m)
 struct rte_mbuf *
 rte_pktmbuf_clone(struct rte_mbuf *md, struct rte_mempool *mp);
 
+/**
+ * Creates a full copy of a given packet mbuf.
+ *
+ * Copies all the data from a given packet mbuf to a newly allocated
+ * set of mbufs.
+ *
+ * @param m
+ *   The packet mbuf to be cloned.
+ * @param mp
+ *   The mempool from which the "clone" mbufs are allocated.
+ * @param offset
+ *   The number of bytes to skip before copying.
+ *   If the mbuf does not have that many bytes, it is an error
+ *   and NULL is returned.
+ * @param length
+ *   The upper limit on bytes to copy.  Passing UINT32_MAX
+ *   means all data (after offset).
+ * @return
+ *   - The pointer to the new "clone" mbuf on success.
+ *   - NULL if allocation fails.
+ */
+__rte_experimental
+struct rte_mbuf *
+rte_pktmbuf_copy(const struct rte_mbuf *m, struct rte_mempool *mp,
+		 uint32_t offset, uint32_t length);
+
 /**
  * Adds given value to the refcnt of all packet mbuf segments.
  *
diff --git a/lib/librte_mbuf/rte_mbuf_version.map b/lib/librte_mbuf/rte_mbuf_version.map
index ff5c18a5559b..a50dcb6db9ec 100644
--- a/lib/librte_mbuf/rte_mbuf_version.map
+++ b/lib/librte_mbuf/rte_mbuf_version.map
@@ -57,4 +57,5 @@ EXPERIMENTAL {
 	global:
 
 	rte_mbuf_check;
+	rte_pktmbuf_copy;
 } DPDK_18.08;
-- 
2.20.1