Patchwork [1/1] tap: reset vnet header size on open

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Submitter Stefan Hajnoczi
Date Nov. 20, 2012, 2:46 p.m.
Message ID <1353422798-30741-2-git-send-email-stefanha@redhat.com>
Download mbox | patch
Permalink /patch/200363/
State New
Headers show

Comments

Stefan Hajnoczi - Nov. 20, 2012, 2:46 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>
Tested-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 net/tap.c | 7 +++++++
 1 file changed, 7 insertions(+)

Patch

diff --git a/net/tap.c b/net/tap.c
index df89caa..1abfd44 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -341,6 +341,13 @@  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;