[PATCH v3] mbuf/ip_frag: Move mbuf chaining to common code

[Simon Kagstrom <simon.kagstrom@netinsight.net>]

Chaining/segmenting mbufs can be useful in many places, so make it
global.

Signed-off-by: Simon Kagstrom <simon.kagstrom@netinsight.net>
Signed-off-by: Johan Faltstrom <johan.faltstrom@netinsight.net>
---
ChangeLog:
v2:
  * Check for nb_segs byte overflow (Olivier MATZ)
  * Don't reset nb_segs in tail (Olivier MATZ)
v3:
  * Describe performance implications of linear search
  * Correct check-for-out-of-bounds (Konstantin Ananyev)

 lib/librte_ip_frag/ip_frag_common.h      | 23 ---------------------
 lib/librte_ip_frag/rte_ipv4_reassembly.c |  7 +++++--
 lib/librte_ip_frag/rte_ipv6_reassembly.c |  7 +++++--
 lib/librte_mbuf/rte_mbuf.h               | 34 ++++++++++++++++++++++++++++++++
 4 files changed, 44 insertions(+), 27 deletions(-)

diff --git a/lib/librte_ip_frag/ip_frag_common.h b/lib/librte_ip_frag/ip_frag_common.h
index 6b2acee..cde6ed4 100644
--- a/lib/librte_ip_frag/ip_frag_common.h
+++ b/lib/librte_ip_frag/ip_frag_common.h
@@ -166,27 +166,4 @@ ip_frag_reset(struct ip_frag_pkt *fp, uint64_t tms)
 	fp->frags[IP_FIRST_FRAG_IDX] = zero_frag;
 }
 
-/* chain two mbufs */
-static inline void
-ip_frag_chain(struct rte_mbuf *mn, struct rte_mbuf *mp)
-{
-	struct rte_mbuf *ms;
-
-	/* adjust start of the last fragment data. */
-	rte_pktmbuf_adj(mp, (uint16_t)(mp->l2_len + mp->l3_len));
-
-	/* chain two fragments. */
-	ms = rte_pktmbuf_lastseg(mn);
-	ms->next = mp;
-
-	/* accumulate number of segments and total length. */
-	mn->nb_segs = (uint8_t)(mn->nb_segs + mp->nb_segs);
-	mn->pkt_len += mp->pkt_len;
-
-	/* reset pkt_len and nb_segs for chained fragment. */
-	mp->pkt_len = mp->data_len;
-	mp->nb_segs = 1;
-}
-
-
 #endif /* _IP_FRAG_COMMON_H_ */
diff --git a/lib/librte_ip_frag/rte_ipv4_reassembly.c b/lib/librte_ip_frag/rte_ipv4_reassembly.c
index 5d24843..26d07f9 100644
--- a/lib/librte_ip_frag/rte_ipv4_reassembly.c
+++ b/lib/librte_ip_frag/rte_ipv4_reassembly.c
@@ -63,7 +63,9 @@ ipv4_frag_reassemble(const struct ip_frag_pkt *fp)
 			/* previous fragment found. */
 			if(fp->frags[i].ofs + fp->frags[i].len == ofs) {
 
-				ip_frag_chain(fp->frags[i].mb, m);
+				/* adjust start of the last fragment data. */
+				rte_pktmbuf_adj(m, (uint16_t)(m->l2_len + m->l3_len));
+				rte_pktmbuf_chain(fp->frags[i].mb, m);
 
 				/* update our last fragment and offset. */
 				m = fp->frags[i].mb;
@@ -78,7 +80,8 @@ ipv4_frag_reassemble(const struct ip_frag_pkt *fp)
 	}
 
 	/* chain with the first fragment. */
-	ip_frag_chain(fp->frags[IP_FIRST_FRAG_IDX].mb, m);
+	rte_pktmbuf_adj(m, (uint16_t)(m->l2_len + m->l3_len));
+	rte_pktmbuf_chain(fp->frags[IP_FIRST_FRAG_IDX].mb, m);
 	m = fp->frags[IP_FIRST_FRAG_IDX].mb;
 
 	/* update mbuf fields for reassembled packet. */
diff --git a/lib/librte_ip_frag/rte_ipv6_reassembly.c b/lib/librte_ip_frag/rte_ipv6_reassembly.c
index 1f1c172..5969b4a 100644
--- a/lib/librte_ip_frag/rte_ipv6_reassembly.c
+++ b/lib/librte_ip_frag/rte_ipv6_reassembly.c
@@ -86,7 +86,9 @@ ipv6_frag_reassemble(const struct ip_frag_pkt *fp)
 			/* previous fragment found. */
 			if (fp->frags[i].ofs + fp->frags[i].len == ofs) {
 
-				ip_frag_chain(fp->frags[i].mb, m);
+				/* adjust start of the last fragment data. */
+				rte_pktmbuf_adj(m, (uint16_t)(m->l2_len + m->l3_len));
+				rte_pktmbuf_chain(fp->frags[i].mb, m);
 
 				/* update our last fragment and offset. */
 				m = fp->frags[i].mb;
@@ -101,7 +103,8 @@ ipv6_frag_reassemble(const struct ip_frag_pkt *fp)
 	}
 
 	/* chain with the first fragment. */
-	ip_frag_chain(fp->frags[IP_FIRST_FRAG_IDX].mb, m);
+	rte_pktmbuf_adj(m, (uint16_t)(m->l2_len + m->l3_len));
+	rte_pktmbuf_chain(fp->frags[IP_FIRST_FRAG_IDX].mb, m);
 	m = fp->frags[IP_FIRST_FRAG_IDX].mb;
 
 	/* update mbuf fields for reassembled packet. */
diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index d7c9030..f1f1400 100644
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -1775,6 +1775,40 @@ static inline int rte_pktmbuf_is_contiguous(const struct rte_mbuf *m)
 }
 
 /**
+ * Chain an mbuf to another, thereby creating a segmented packet.
+ *
+ * Note: The implementation will do a linear walk over the segments to find
+ * the tail entry. For cases when there are many segments, it's better to
+ * chain the entries manually.
+ *
+ * @param head the head of the mbuf chain (the first packet)
+ * @param tail the mbuf to put last in the chain
+ *
+ * @return 0 on success, -EOVERFLOW if the chain is full (256 entries)
+ */
+static inline int rte_pktmbuf_chain(struct rte_mbuf *head, struct rte_mbuf *tail)
+{
+	struct rte_mbuf *cur_tail;
+
+	/* Check for number-of-segments-overflow */
+	if (head->nb_segs + tail->nb_segs >= 1 << (sizeof(head->nb_segs) * 8))
+		return -EOVERFLOW;
+
+	/* Chain 'tail' onto the old tail */
+	cur_tail = rte_pktmbuf_lastseg(head);
+	cur_tail->next = tail;
+
+	/* accumulate number of segments and total length. */
+	head->nb_segs = (uint8_t)(head->nb_segs + tail->nb_segs);
+	head->pkt_len += tail->pkt_len;
+
+	/* pkt_len is only set in the head */
+	tail->pkt_len = tail->data_len;
+
+	return 0;
+}
+
+/**
  * Dump an mbuf structure to the console.
  *
  * Dump all fields for the given packet mbuf and all its associated
-- 
1.9.1