[dpdk-dev] [PATCH v6 4/5] mbuf: add a pktmbuf copy routine

[Stephen Hemminger]

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.

This patch also introduces internal inline to copy the
metadata fields of mbuf.

Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
---
 lib/librte_mbuf/rte_mbuf.c           | 77 ++++++++++++++++++++++++++++
 lib/librte_mbuf/rte_mbuf.h           | 55 ++++++++++++++++----
 lib/librte_mbuf/rte_mbuf_version.map |  1 +
 3 files changed, 122 insertions(+), 11 deletions(-)

diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
index 9a1a1b5f9468..0236fba76bbc 100644
--- a/lib/librte_mbuf/rte_mbuf.c
+++ b/lib/librte_mbuf/rte_mbuf.c
@@ -321,6 +321,83 @@ __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;
+
+	/* 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)
diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index 6133f12172ae..fb0849ac1473 100644
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -1684,6 +1684,19 @@ rte_pktmbuf_attach_extbuf(struct rte_mbuf *m, void *buf_addr,
  */
 #define rte_pktmbuf_detach_extbuf(m) rte_pktmbuf_detach(m)
 
+/* internal */
+static inline void
+__rte_pktmbuf_copy_hdr(struct rte_mbuf *mdst, const struct rte_mbuf *msrc)
+{
+	mdst->port = msrc->port;
+	mdst->vlan_tci = msrc->vlan_tci;
+	mdst->vlan_tci_outer = msrc->vlan_tci_outer;
+	mdst->tx_offload = msrc->tx_offload;
+	mdst->hash = msrc->hash;
+	mdst->packet_type = msrc->packet_type;
+	mdst->timestamp = msrc->timestamp;
+}
+
 /**
  * Attach packet mbuf to another packet mbuf.
  *
@@ -1721,23 +1734,17 @@ static inline void rte_pktmbuf_attach(struct rte_mbuf *mi, struct rte_mbuf *m)
 		mi->ol_flags = m->ol_flags | IND_ATTACHED_MBUF;
 	}
 
-	mi->buf_iova = m->buf_iova;
-	mi->buf_addr = m->buf_addr;
-	mi->buf_len = m->buf_len;
+	__rte_pktmbuf_copy_hdr(mi, m);
 
 	mi->data_off = m->data_off;
 	mi->data_len = m->data_len;
-	mi->port = m->port;
-	mi->vlan_tci = m->vlan_tci;
-	mi->vlan_tci_outer = m->vlan_tci_outer;
-	mi->tx_offload = m->tx_offload;
-	mi->hash = m->hash;
+	mi->buf_iova = m->buf_iova;
+	mi->buf_addr = m->buf_addr;
+	mi->buf_len = m->buf_len;
 
 	mi->next = NULL;
 	mi->pkt_len = mi->data_len;
 	mi->nb_segs = 1;
-	mi->packet_type = m->packet_type;
-	mi->timestamp = m->timestamp;
 
 	__rte_mbuf_sanity_check(mi, 1);
 	__rte_mbuf_sanity_check(m, 0);
@@ -1908,7 +1915,7 @@ static inline void rte_pktmbuf_free(struct rte_mbuf *m)
 }
 
 /**
- * Creates a "clone" of the given packet mbuf.
+ * Create a "clone" of the given packet mbuf.
  *
  * Walks through all segments of the given packet mbuf, and for each of them:
  *  - Creates a new packet mbuf from the given pool.
@@ -1927,6 +1934,32 @@ static inline void rte_pktmbuf_free(struct rte_mbuf *m)
 struct rte_mbuf *
 rte_pktmbuf_clone(struct rte_mbuf *md, struct rte_mempool *mp);
 
+/**
+ * Create a full copy of a given packet mbuf.
+ *
+ * Copies all the data from a given packet mbuf to a newly allocated
+ * set of mbufs. The private data are is not copied.
+ *
+ * @param m
+ *   The packet mbuf to be copiedd.
+ * @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