[4/4] tap: reset vnet header size on open

Submitted by Stefan Hajnoczi on Nov. 16, 2012, 1:40 p.m.

Details

Message ID 1353073206-31501-5-git-send-email-stefanha@redhat.com
State New
Headers show

Commit Message

Stefan Hajnoczi Nov. 16, 2012, 1:40 p.m.
From: "Michael S. Tsirkin" <mst@redhat.com>

For tap, we currently assume the vnet header size is 10
(the default value) but that might not be the case
if tap is persistent and has been used by qemu previously.
To fix, set host header size in tap device on open.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 net/tap.c | 7 +++++++
 1 file changed, 7 insertions(+)

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diff --git a/net/tap.c b/net/tap.c
index 7102b91..efd2bab 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -338,6 +338,13 @@  static TAPState *net_tap_fd_init(NetClientState *peer,
     s->using_vnet_hdr = 0;
     s->has_ufo = tap_probe_has_ufo(s->fd);
     tap_set_offload(&s->nc, 0, 0, 0, 0, 0);
+    /*
+     * Make sure host header length is set correctly in tap:
+     * it might have been modified by another instance of qemu.
+     */
+    if (tap_probe_vnet_hdr_len(s->fd, s->host_vnet_hdr_len)) {
+        tap_fd_set_vnet_hdr_len(s->fd, s->host_vnet_hdr_len);
+    }
     tap_read_poll(s, 1);
     s->vhost_net = NULL;
     return s;