[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [RFC] net: Peer with existing NIC in netdev_add
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [RFC] net: Peer with existing NIC in netdev_add |
Date: |
Wed, 24 Oct 2012 14:49:21 +0200 |
Allow netdev_del followed by netdev_add to re-peer a NIC and its netdev:
(qemu) info network
virtio-net-pci.0: type=nic,model=virtio-net-pci,macaddr=52:54:00:12:34:56
\ netdev0: type=user,net=10.0.2.0,restrict=off
(qemu) netdev_del netdev0
(qemu) netdev_add socket,id=netdev0,listen=:1234
(qemu) info network
virtio-net-pci.0: type=nic,model=virtio-net-pci,macaddr=52:54:00:12:34:56
\ netdev0: type=socket,
This makes it possible to switch netdev while the guest is running. It
is not necessary to reset the NIC.
Note that the NIC's link goes down in netdev_del and back up again in
netdev_add. Therefore the guest becomes aware that the network has
changed, although this depends on the emulated NIC model providing link
status change interrupts.
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
This patch addresses the netdev hotplug issue that has been discussed
previously on the mailing list:
https://www.redhat.com/archives/libvir-list/2012-October/msg00629.html
Initially I thought we need to add a new monitor command. After looking at the
code it seems that simply allowing netdev_del followed by netdev_add (as
suggested by Laine) is the simplest way to solve the problem. No new monitor
commands are necessary.
The current code is not safe with virtio-net + tap, where the virtio-net device
reports offload features from the tap device to the guest. If you try to
switch to a -netdev user or -netdev socket device, those offload capabilities
are not present and network communication will fail.
Laine: Please try this out and see if it works for your use case.
net.c | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)
diff --git a/net.c b/net.c
index ae4bc0d..d7c60b0 100644
--- a/net.c
+++ b/net.c
@@ -619,6 +619,19 @@ static int (* const
net_client_init_fun[NET_CLIENT_OPTIONS_KIND_MAX])(
[NET_CLIENT_OPTIONS_KIND_HUBPORT] = net_init_hubport,
};
+static NICState *net_find_nic_for_peername(const char *name)
+{
+ NetClientState *nc;
+ QTAILQ_FOREACH(nc, &net_clients, next) {
+ if (nc->info->type != NET_CLIENT_OPTIONS_KIND_NIC) {
+ continue;
+ }
+ if (nc->peer && strcmp(nc->peer->name, name) == 0) {
+ return (NICState *)nc;
+ }
+ }
+ return NULL;
+}
static int net_client_init1(const void *object, int is_netdev, Error **errp)
{
@@ -678,6 +691,25 @@ static int net_client_init1(const void *object, int
is_netdev, Error **errp)
NetClientOptionsKind_lookup[opts->kind]);
return -1;
}
+
+ /* Peer with existing nic if netdev name matches */
+ if (is_netdev && opts->kind != NET_CLIENT_OPTIONS_KIND_NIC) {
+ NICState *nic = net_find_nic_for_peername(name);
+ if (nic && nic->peer_deleted) {
+ NetClientState *netdev = qemu_find_netdev(name);
+
+ /* TODO vnet_hdr compatibility check */
+
+ qemu_free_net_client(nic->nc.peer);
+ nic->nc.peer = netdev;
+ netdev->peer = &nic->nc;
+ nic->peer_deleted = false;
+ nic->nc.link_down = false;
+ if (nic->nc.info->link_status_changed) {
+ nic->nc.info->link_status_changed(&nic->nc);
+ }
+ }
+ }
}
return 0;
}
--
1.7.11.7
- [Qemu-devel] [RFC] net: Peer with existing NIC in netdev_add,
Stefan Hajnoczi <=