tap: Use different io vector bases depending on tap type

Currently tap_send_frames() expects the frames it is given to include the
vnet_len field, even in pasta mode which doesn't use it (although it need
not be initialized in that case).  To match, tap_iov_base() and
tap_iov_len() construct the frame in that way.

This will inconvenience future changes, so alter things to set the buffers
to include just the frame needed by the tap backend type.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/tap.h b/tap.h
index 8fe460a..40cf480 100644
--- a/tap.h
+++ b/tap.h
@@ -20,8 +20,10 @@ struct tap_hdr {
 
 static inline size_t tap_hdr_len_(const struct ctx *c)
 {
-	(void)c;
-	return sizeof(struct tap_hdr);
+	if (c->mode == MODE_PASST)
+		return sizeof(struct tap_hdr);
+	else
+		return sizeof(struct ethhdr);
 }
 
 /**