[dpdk-dev] [PATCH] examples/vhost: Fix data len issue

[Ouyang Changchun]

Search the right segment to increase its data length, rather than
wrongly early return and exit the tx function, which leads to drop all jumbo frame packets
when vm2vm is in hard forward mode.

Signed-off-by: Changchun Ouyang <changchun.ouyang at intel.com>
---
 examples/vhost/main.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/examples/vhost/main.c b/examples/vhost/main.c
index 1f1edbe..12fa4ce 100644
--- a/examples/vhost/main.c
+++ b/examples/vhost/main.c
@@ -1127,9 +1127,8 @@ virtio_tx_route(struct vhost_dev *vdev, struct rte_mbuf *m, uint16_t vlan_tag)
 		return;
 	}
 
-	if (vm2vm_mode == VM2VM_HARDWARE) {
-		if (find_local_dest(dev, m, &offset, &vlan_tag) != 0 ||
-			offset > rte_pktmbuf_tailroom(m)) {
+	if (unlikely(vm2vm_mode == VM2VM_HARDWARE)) {
+		if (unlikely(find_local_dest(dev, m, &offset, &vlan_tag) != 0)) {
 			rte_pktmbuf_free(m);
 			return;
 		}
@@ -1143,8 +1142,24 @@ virtio_tx_route(struct vhost_dev *vdev, struct rte_mbuf *m, uint16_t vlan_tag)
 
 	m->ol_flags = PKT_TX_VLAN_PKT;
 
-	m->data_len += offset;
-	m->pkt_len += offset;
+	/*
+	 * Find the right seg to adjust the data len when offset is
+	 * bigger than tail room size.
+	 */
+	if (unlikely(vm2vm_mode == VM2VM_HARDWARE)) {
+		if (likely(offset <= rte_pktmbuf_tailroom(m)))
+			m->data_len += offset;
+		else {
+			struct rte_mbuf *seg = m;
+
+			while ((seg->next != NULL) &&
+				(offset > rte_pktmbuf_tailroom(seg)))
+				seg = seg->next;
+
+			seg->data_len += offset;
+		}
+		m->pkt_len += offset;
+	}
 
 	m->vlan_tci = vlan_tag;
 
-- 
1.8.4.2