[dpdk-stable] [PATCH] net/virtio: fix broken transmit functionality

[Andrew Rybchenko]

Previous fix removes usage of rte_pktmbuf_prepend() to get pointer
to virtio net header which changes mbuf data_off and data_len.
Size of virtio net header is added to segment length when Tx descriptor
is composed, but segment address (calculated using data_off) is not
adjusted to take size of virtio net header into account.

Fixes: c100fc6849fb ("net/virtio: fix mbuf data and pkt length mismatch")
Cc: stable at dpdk.org

Signed-off-by: Andrew Rybchenko <arybchenko at solarflare.com>
---
 drivers/net/virtio/virtio_rxtx.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index 929aa4cbd..434e0fedd 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -649,7 +649,8 @@ virtqueue_enqueue_xmit_inorder(struct virtnet_tx *txvq,
 		else
 			virtqueue_xmit_offload(hdr, cookies[i], true);
 
-		start_dp[idx].addr  = VIRTIO_MBUF_DATA_DMA_ADDR(cookies[i], vq);
+		start_dp[idx].addr  =
+			VIRTIO_MBUF_DATA_DMA_ADDR(cookies[i], vq) - head_size;
 		start_dp[idx].len   = cookies[i]->data_len + head_size;
 		start_dp[idx].flags = 0;
 
@@ -696,7 +697,7 @@ virtqueue_enqueue_xmit_packed_fast(struct virtnet_tx *txvq,
 	else
 		virtqueue_xmit_offload(hdr, cookie, true);
 
-	dp->addr = VIRTIO_MBUF_DATA_DMA_ADDR(cookie, vq);
+	dp->addr = VIRTIO_MBUF_DATA_DMA_ADDR(cookie, vq) - head_size;
 	dp->len  = cookie->data_len + head_size;
 	dp->id   = id;
 
@@ -779,6 +780,7 @@ virtqueue_enqueue_xmit_packed(struct virtnet_tx *txvq, struct rte_mbuf *cookie,
 		start_dp[idx].addr = VIRTIO_MBUF_DATA_DMA_ADDR(cookie, vq);
 		start_dp[idx].len  = cookie->data_len;
 		if (prepend_header) {
+			start_dp[idx].addr -= head_size;
 			start_dp[idx].len += head_size;
 			prepend_header = false;
 		}
@@ -882,6 +884,7 @@ virtqueue_enqueue_xmit(struct virtnet_tx *txvq, struct rte_mbuf *cookie,
 		start_dp[idx].addr  = VIRTIO_MBUF_DATA_DMA_ADDR(cookie, vq);
 		start_dp[idx].len   = cookie->data_len;
 		if (prepend_header) {
+			start_dp[idx].addr -= head_size;
 			start_dp[idx].len += head_size;
 			prepend_header = false;
 		}
-- 
2.20.1