[PULL 10/20] virtio-net: Shrink header byte swapping buffer

[Jason Wang <jasowang@redhat.com>]

From: Akihiko Odaki <akihiko.odaki@daynix.com>

Byte swapping is only performed for the part of header shared with the
legacy standard and the buffer only needs to cover it.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/net/virtio-net.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 13a17a1e5a..dabfa6e7d7 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -676,11 +676,6 @@ static void virtio_net_set_mrg_rx_bufs(VirtIONet *n, int mergeable_rx_bufs,
 
     n->mergeable_rx_bufs = mergeable_rx_bufs;
 
-    /*
-     * Note: when extending the vnet header, please make sure to
-     * change the vnet header copying logic in virtio_net_flush_tx()
-     * as well.
-     */
     if (version_1) {
         n->guest_hdr_len = hash_report ?
             sizeof(struct virtio_net_hdr_v1_hash) :
@@ -2736,7 +2731,7 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
         ssize_t ret;
         unsigned int out_num;
         struct iovec sg[VIRTQUEUE_MAX_SIZE], sg2[VIRTQUEUE_MAX_SIZE + 1], *out_sg;
-        struct virtio_net_hdr_v1_hash vhdr;
+        struct virtio_net_hdr vhdr;
 
         elem = virtqueue_pop(q->tx_vq, sizeof(VirtQueueElement));
         if (!elem) {
@@ -2753,18 +2748,18 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
         }
 
         if (n->needs_vnet_hdr_swap) {
-            if (iov_to_buf(out_sg, out_num, 0, &vhdr, n->guest_hdr_len) <
-                n->guest_hdr_len) {
+            if (iov_to_buf(out_sg, out_num, 0, &vhdr, sizeof(vhdr)) <
+                sizeof(vhdr)) {
                 virtio_error(vdev, "virtio-net header incorrect");
                 virtqueue_detach_element(q->tx_vq, elem, 0);
                 g_free(elem);
                 return -EINVAL;
             }
-            virtio_net_hdr_swap(vdev, (void *) &vhdr);
+            virtio_net_hdr_swap(vdev, &vhdr);
             sg2[0].iov_base = &vhdr;
-            sg2[0].iov_len = n->guest_hdr_len;
+            sg2[0].iov_len = sizeof(vhdr);
             out_num = iov_copy(&sg2[1], ARRAY_SIZE(sg2) - 1, out_sg, out_num,
-                               n->guest_hdr_len, -1);
+                               sizeof(vhdr), -1);
             if (out_num == VIRTQUEUE_MAX_SIZE) {
                 goto drop;
             }
-- 
2.42.0